Gilead Sciences
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SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549
------------------------
FORM 10-K

(MARK ONE)

<TABLE>
<C> <S>
/X/ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
SECURITIES EXCHANGE ACT OF 1934
</TABLE>

FOR THE FISCAL YEAR ENDED DECEMBER 31, 1999
OR

<TABLE>
<C> <S>
/ / TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
SECURITIES EXCHANGE ACT OF 1934
</TABLE>

FOR THE TRANSITION PERIOD FROM ______________ TO ______________

COMMISSION FILE NO. 0-19731
------------------------
GILEAD SCIENCES, INC.

(Exact name of registrant as specified in its charter)

<TABLE>
<S> <C>
DELAWARE 94-3047598
(State or other jurisdiction of (I.R.S. Employer Identification No.)
incorporation or organization)
333 LAKESIDE DRIVE, FOSTER CITY, 94404
CALIFORNIA (Zip Code)
(Address of principal executive
offices)
</TABLE>

Registrant's telephone number, including area code: 650-574-3000
------------------------

SECURITIES REGISTERED PURSUANT TO SECTION 12 (b) OF THE ACT: NONE

SECURITIES REGISTERED PURSUANT TO SECTION 12 (g) OF THE ACT:

COMMON STOCK $.001 PAR VALUE
(Title of Class)
------------------------

Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15 (d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
Registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes /X/ No / /

Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K (Section 229.405 of this chapter) is not contained herein,
and will not be contained, to the best of registrant's knowledge, in definitive
proxy or information statements incorporated by reference in Part III of this
Form 10-K or any amendment to this Form 10-K. Yes /X/ No / /

The aggregate market value of the voting stock held by non-affiliates of the
Registrant based upon the closing price of the Common Stock on the Nasdaq Stock
Market on February 25, 2000 was $2,442,500,000*.

The number of shares outstanding of the Registrant's Common Stock on
February 25, 2000 was 44,388,828.

DOCUMENTS INCORPORATED BY REFERENCE

Specified portions of Registrant's Definitive Proxy Statement filed with the
Commission pursuant to Regulation 14A in connection with the 2000 Annual Meeting
are incorporated by reference into Part III of this Report.

- ------------------------

* Based on a closing price of $72.34 per share. Excludes 10,625,287 shares of
the Registrant's Common Stock held by executive officers, directors and
stockholders whose ownership exceeds 5% of the Common Stock outstanding at
February 25, 2000. Exclusion of such shares should not be construed to
indicate that any such person possesses the power, direct or indirect, to
direct or cause the direction of the management or policies of the
Registrant or that such person is controlled by or under common control with
the Registrant.

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PART I

ITEM 1. BUSINESS

FORWARD-LOOKING STATEMENTS AND RISK FACTORS

In addition to the historical information contained in this report, this
report contains forward-looking statements within the meaning of Section 27A of
the Securities Act and Section 21E of the Exchange Act that involve risks and
uncertainties. Our actual financial and operating results could differ
materially from our expectations. Factors that could cause or contribute to
these differences include uncertainties related to future sales of our products
and uncertainties relating to clinical results and regulatory approval of our
product candidates, as well as the factors listed under "Risk Factors" beginning
on page 26 of this report.

GENERAL

Gilead Sciences, Inc. is an independent biopharmaceutical company that seeks
to provide accelerated solutions for patients and the people who care for them.
We have a broad-based focus on developing and marketing drugs to treat patients
with infectious diseases, including viral infections, fungal infections and
bacterial infections, and a specialized focus on cancer. We also have expertise
in liposomal drug delivery technology, a technology that we use to develop drugs
that are safer, easier for patients to tolerate and more effective.

Within our focus areas, we have developed four products that have been
approved by the U.S. Food and Drug Administration (FDA). We also have five
product candidates in human clinical trials, including two that are in "Phase
III" advanced clinical trials. In addition, we continually seek to develop or
acquire rights to additional products, compounds and technologies to treat
diseases for which no therapies exist or for which patients and the medical
community have demanded new and improved therapies.

Developing and selling drugs is a very difficult business. We discuss many
of the factors that make this a difficult business under the caption "Risk
Factors" beginning on page 26. Perhaps the most challenging aspect of our
business is the complex regulatory environment that we operate in. Before we can
sell a drug, we must obtain a substantial amount of data about the drug in
rigorous clinical trials. The FDA and regulatory authorities in other countries
then review the data generated from these trials. The FDA and these other
regulatory authorities will not approve a drug if they believe that it is not
safe enough, or effective enough, if they believe it cannot be properly
manufactured, or if they believe that our clinical trails are unreliable. In
addition, our approved drugs are subject to extensive ongoing regulation.

We have been researching and developing drugs at our corporate headquarters
in Foster City since we became a company in 1987 and began selling our first
commercial product, VISTIDE-Registered Trademark-, in June 1996. In July 1999,
we substantially increased the size of our organization when we combined with
NeXstar Pharmaceuticals, Inc. in a stock-for-stock merger. Today we have four
commercial products and research and development facilities in Foster City,
California, Boulder, Colorado, San Dimas, California and Cambridge, U.K. We also
have manufacturing operations at our San Dimas facility and in Ireland, and
sales and marketing operations in the United States, Europe and Australia.

OUR MARKETED PRODUCTS

The products we have developed that are commercially available include:

- AmBisome-Registered Trademark-: A drug for treating and preventing
life-threatening fungal infections;

- Tamiflu-TM-: A drug for treating influenza;

1
- VISTIDE: A drug for treating CMV retinitis in AIDS patients; and

- DaunoXome-Registered Trademark-: A drug for treating AIDS-related Kaposi's
sarcoma.

How these products are sold, and the uses or "indications" that they are
approved for, varies with each product and in each country or region where they
are sold.

In 1999, we earned revenues of approximately $150.3 million from sales of
these products. Of this amount, sales of AmBisome generated aggregate product
sales and royalty revenues of approximately $137.5 million, or 81% of our total
revenues. Hoffmann-La Roche, our corporate partner who sells Tamiflu, did not
begin selling Tamiflu until November 1999. We expect that royalty revenues we
earn from sales of Tamiflu in 2000 will decrease the percentage of our total
revenues from sales of AmBisome, although we cannot predict with any certainty
what our actual revenues from either AmBisome or Tamiflu will be in 2000. We do,
however, expect that revenues from sales of AmBisome will continue to constitute
a substantial majority of our total revenues in 2000.

AMBISOME

AmBisome is a liposomal formulation of amphotericin B. Amphotericin B is a
powerful antifungal agent that is well known for its ability to attack and kill
a broad variety of life-threatening fungal infections but also has serious side
effects, including kidney toxicity. The patients most likely to suffer from
these fungal infections are patients with weakened immune systems including
transplant patients, patients infected with the HIV virus, and cancer patients
undergoing chemotherapy. By delivering amphotericin B in our proprietary
liposomal formulation, studies show that AmBisome reduces the rate and severity
of kidney toxicity and injection-related reactions, and allows these patients to
receive higher and more effective doses of amphotericin B.

We sell AmBisome in 40 countries, including the United States, all of the
European Union, most of the rest of Europe and several countries in Latin
America and Asia. AmBisome is primarily used for treating patients who are known
to have life-threatening fungal infections. AmBisome is also approved in the
United States and nine other countries to treat patients who, because of certain
symptoms, are presumed to have fungal infections. In addition, AmBisome is
approved in four countries as a precautionary treatment for preventing fungal
infections in liver transplant patients, and is approved for treating a rare
parasitic infection called visceral leishmaniasis in several countries. In 16 of
the countries where we sell AmBisome, including the United States, we are
authorized to promote AmBisome as a first choice for treating patients who are
known to have a fungal infection--a "first line therapy". In the other 24
countries, we promote AmBisome for use after traditional amphotericin B therapy
fails or when traditional amphotericin B cannot be used--a "second line
therapy."

In the United States, we co-promote AmBisome with Fujisawa Healthcare
through our domestic sales force. Our agreement with Fujisawa entitles us to a
percentage of revenues generated from these sales and provides that Fujisawa
purchases AmBisome from us at our manufacturing cost. See "Collaborative
Relationships--Fujisawa". In the major European countries and in Australia, we
sell AmBisome through our international sales force. We also sell AmBisome
through independent distributors in a number of countries in Europe, Latin
America and Asia. Our corporate partner, Sumitomo, has filed an application
requesting approval of AmBisome in Japan. We gave Sumitomo the exclusive right
to sell AmBisome in Japan and would receive a percentage of any revenues that
they receive from those sales. See "Collaborative Relationships--Sumitomo." Most
of our sales of AmBisome are in Europe and we expect this to be the case for the
foreseeable future. In most significant European countries, we sell AmBisome in
the currency of that country and our revenues could therefore be decreased if
the value of the U.S. Dollar were to decrease relative to these other
currencies.

2
Traditional amphotericin B is the most significant competition for AmBisome.
In many countries, AmBisome cannot be prescribed until traditional amphotericin
B therapy has failed or cannot be used. In addition, there are other lipid-based
formulations of amphotericin B that compete with AmBisome and there are other
products being developed that are likely to compete with AmBisome in the future.
The most significant lipid-based amphotericin B product that currently competes
with AmBisome is Abelcet, a drug sold by The Liposome Company. The Liposome
Company recently announced that it will be acquired by Elan Corporation, a
company with significantly greater resources than we have. Traditional
amphotericin B is significantly less expensive than AmBisome, and Abelcet is
also less expensive than AmBisome. Fujisawa recently completed a multicenter
study in 244 patients comparing AmBisome to Abelcet. This study showed that in
neutropenic cancer patients with unresolved fever (cancer patients with low
white blood cell counts and continuing fevers), AmBisome was significantly safer
than Abelcet yet was equally effective. The FDA has reviewed this study and has
allowed Fujisawa to include this comparative data in their labels for AmBisome
sold in the United States. We cannot be certain, however, that the medical
community will accept the results of this study or that the study will improve
the competitive position of AmBisome. See "Competition."

OTHER POTENTIAL USES FOR AMBISOME

AmBisome is also being studied for the following potential uses:

- Fujisawa has completed Phase III clinical trials for treating acute
cryptococcal meningitis in AIDS patients and has requested approval from
the FDA for this use. We have filed for approval of AmBisome for this use
in France.

- Fujisawa is studying AmBisome in Phase II clinical trials for treating
"Histoplasmosis" a rare fungal infection that affects persons with
compromised immune systems and is most common in the midwestern United
States. The results of this study, which showed that AmBisome was safer
and more effective than traditional amphotericin B in achieving certain
clinical end points, will be presented to the FDA and published.

We cannot be certain that any of these studies will be successful or that
the FDA or any other regulatory agencies will approve AmBisome for these other
potential uses.

TAMIFLU

Tamiflu is an orally administered pill for the treatment of influenza A and
B that was approved by the FDA on October 27, 1999. Tamiflu is in a new class of
drugs called neuraminidase inhibitors that act by disabling all common strains
of the flu virus and preventing the virus from spreading in a patient. As
approved by the FDA, when taken twice daily for five days starting within 48
hours of initial symptoms, studies show that Tamiflu reduces the duration of the
flu by an average of 1.3 days. Tamiflu also reduces the severity of flu symptoms
and the incidence of secondary infections. Tamiflu is approved for this use in
adult patients with uncomplicated influenza. The most common side effect
associated with Tamiflu is mild nausea and vomiting.

Hoffmann-La Roche, our corporate partner who developed Tamiflu with us and
who has the exclusive right to sell Tamiflu, began selling Tamiflu in the United
States in November 1999. In May 1999, Hoffmann-La Roche submitted a Marketing
Authorisation Application to the European Commission seeking to have Tamiflu
approved under the centralized procedure in the European Union. We cannot be
certain if or when this application will be approved. We receive a percentage of
the net revenues that Hoffmann-La Roche generates from sales of Tamiflu. See
"Collaborative Relationships--Hoffmann-La Roche."

There are several products that have been available to treat the flu for
some time, but they have not been shown to be as effective or safe as
neuraminidase inhibitors. Relenza, an anti-flu drug sold by

3
Glaxo Wellcome, is the only other neuraminidase inhibitor that has been approved
by the FDA. This drug, which is delivered as an inhaled powder, is direct and
significant competition for Tamiflu. Tamiflu currently is the only FDA-approved
neuraminidase inhibitor that is available in a pill and we believe that this
method of delivery gives Tamiflu a competitive advantage over Relenza. We are
aware, however, that Johnson & Johnson is developing a neuraminidase inhibitor
that has the potential to be delivered as a once-daily pill. When and if
Johnson & Johnson receives approval for this product, it will also be direct and
significant competition for Tamiflu. See "Competition."

OTHER POTENTIAL USES FOR TAMIFLU

Tamiflu is also being studied for the following potential uses:

- Hoffmann-La Roche is evaluating Tamiflu in elderly patients aged 65 and
older as well as in children between the ages 1-12. The results of the
study of Tamiflu in elderly patients and children have been similar to the
results of the studies involving adults ages 18-65.

- Hoffmann-La Roche is studying Tamiflu as a preventative medicine--a pill
that a healthy person could take to prevent the flu. This study has shown
that people in the study groups who have taken Tamiflu are less likely to
become infected with the flu than people in the study groups who have not
taken Tamiflu.

Drugs tend to have different affects on people in different age groups and
it is possible that the FDA will have different criteria to approve Tamiflu for
these uses. We cannot be certain that Tamiflu will be approved for any of these
additional uses.

Tamiflu is not being marketed as an alternative to influenza vaccinations.
Even if Tamiflu is approved as a method to prevent infection with the flu virus,
influenza vaccinations will remain the most effective method of preventing the
flu.

VISTIDE

VISTIDE is an antiviral medication for the treatment of CMV retinitis in
patients with AIDS. CMV retinitis is a condition caused by a viral infection
(cytomegalovirus or CMV) that is characterized by lesions that form on a
patient's retina. This condition affects persons with weakened immune systems
and is most common in patients with AIDS. If left untreated, CMV retinitis can
lead to blindness. VISTIDE was approved by the FDA in June 1996 and by the
European regulatory authorities in May 1997 based on clinical trials
demonstrating that the drug delays the progression of CMV retinitis lesions in
newly diagnosed patients, and in previously treated patients who had failed
other therapies.

We sell VISTIDE in the United States primarily through our sales force of
therapeutic specialists. These specialists promote VISTIDE through direct
contact with physicians, hospitals, clinics, and other healthcare providers who
are involved in the treatment of patients with CMV retinitis. We also sell
VISTIDE to wholesalers and specialty distributors who sell the product in the
United States to healthcare providers. See "Marketing and Sales." Outside the
United States, Pharmacia & Upjohn has the exclusive right to sell VISTIDE.
Pharmacia & Upjohn currently sells VISTIDE in all 15 countries of the European
Union as well as 7 other countries throughout the world and is seeking clearance
to sell VISTIDE in Colombia, Mexico and New Zealand. Pharmacia & Upjohn pay to
us a percentage of any revenues it generates from sales of VISTIDE. See
"Collaborative Relationships--Pharmacia & Upjohn."

There are several other products that compete with VISTIDE. Ganciclovir,
which is sold by Roche Laboratories, is the most widely prescribed drug
treatment for CMV retinitis. Ganciclovir is available in injectable and oral
formulations, and the oral formulation is approved for both preventing and
treating CMV retinitis. There is a device that is marketed by Bausch & Lomb
Incorporated that is implanted in a patient's infected eye and releases
ganciclovir directly to the infected area. In addition, AstraZeneca sells an
injectable drug for the treatment of CMV retinitis called foscarnet, and
CibaVision sells a

4
CMV retinitis drug called formivirsen, that is injected directly into the eye.
There also are drugs in clinical development for the treatment of CMV retinitis
that would compete with VISTIDE if they are approved. We believe that VISTIDE
has competitive advantages over existing products, including dosing convenience
and effectiveness, but we can't be certain that we will be successful in
maintaining or increasing VISTIDE's share of the declining CMV retinitis
treatment market. See "Competition." The CMV retinitis market has been declining
in recent years due to the success of combination antiretroviral drug therapies
in treating HIV-infected patients.

The most significant side effect associated with the use of VISTIDE is
kidney toxicity. Due to this side effect, certain precautions must be taken when
VISTIDE is used, and in certain circumstances VISTIDE may not be used. Each time
VISTIDE is given to a patient, the patient must first be tested for warning
signs of kidney toxicity. If the patient does not have warning signs of kidney
toxicity, VISTIDE may be given to that patient but only in combination with
certain solutions that reduce the possibility of kidney toxicity. In addition,
VISTIDE may not be given to patients who are receiving other drugs that can
cause kidney toxicity. Patients who are receiving other drugs that are known to
cause kidney toxicity must discontinue taking those drugs and then wait
seven days before using VISTIDE. In certain animal studies, cidofovir, the
active ingredient in VISTIDE, has caused cancer. These side effects and dosing
limitations are a competitive disadvantage of VISTIDE.

In August 1994, we entered into a license and supply agreement with
Bausch & Lomb. This agreement provided that Bausch & Lomb would develop and have
the right to market an eye drop formulation of cidofovir for the potential
treatment of certain infections of the eye. This agreement and the related
funding was terminated by Bausch & Lomb in December 1999 because Bausch & Lomb
did not believe they were achieving their performance objectives. We are
evaluating this use of cidofovir but have not yet determined if we will continue
this development ourselves, seek a partner for this development or terminate
this program.

We have an exclusive, worldwide license to patent rights and related
technology for cidofovir from IOCB/REGA, and are obligated to pay a percentage
of any revenues from sales of VISTIDE or any other products containing cidofovir
to IOCB/REGA. See "Collaborative Relationships--
IOCB/REGA."

DAUNOXOME

DaunoXome is a liposomal formulation of the anticancer agent daunorubicin.
We have received approval to sell DaunoXome in the United States, Canada and 22
other countries as a primary "first line" therapy for treating patients who
suffer from HIV-associated Kaposi's sarcoma. Kaposi's sarcoma is a disease
characterized by widely disseminated lesions in the skin, mucous membranes,
lymph nodes and viscera that can be life threatening for patients suffering from
AIDS.

DaunoXome uses our proprietary liposomal technology to deliver safer and
more effective doses of daunorubicin to the disease site. Studies have shown
that DaunoXome may actually locate and accumulate in the patient's tumor and
allow a patient to receive higher concentrations of daunorubicin at the disease
site than could be obtained with an equivalent dose of non-liposomal
daunorubicin.

DaunoXome is marketed in the United States and abroad by our therapeutic
specialists and, in certain foreign countries, by distributors. The number of
HIV-infected patients who develop Kaposi's sarcoma has declined in recent years
due to the success of combination therapies in treating HIV patients. This has
reduced the overall size of the potential market for drugs that, like DuanoXome,
treat these patients.

DaunoXome is also being studied for other potential uses in other forms of
cancer including a Phase II clinical trial for certain forms of leukemia. We
cannot be certain that any of these studies will be successful or that DaunoXome
will ever be approved for any additional uses.

5
PRODUCTS IN LATE STAGE CLINICAL TRIALS

We have two product candidates in large, late-stage human clinical trials:
tenofovir DF for treating patients with HIV; and adefovir dipivoxil for treating
patients with hepatitis B. If these Phase III clinical trials are successful, we
will apply with the FDA and other foreign regulatory agencies for approval to
sell these drugs. We cannot determine with any certainty whether or not any of
these clinical trials will be successful and, if they are successful, whether or
not the FDA or any other regulatory agencies will approve either of these drugs
for marketing.

TENOFOVIR DISOPROXIL FUMARATE

In September 1999, we presented results from our Phase II clinical trial of
tenofovir DF. This study evaluated the safety and effectiveness of three doses
of tenofovir DF in combination with other HIV drugs in 189 patients who had been
taking other HIV drugs. This randomized, placebo controlled, double blind trial*
showed that, following 24 weeks of treatment, higher doses of tenofovir DF were
associated with lower levels of the HIV in a treatment-experienced patient
population. The study also showed that 24 weeks of dosing with tenofovir DF did
not result in an increase of serious adverse events compared to dosing with
placebo. The following chart provides more detail regarding the data that was
obtained through the 24-week period:

<TABLE>
<CAPTION>
AFFECT ON VIRAL
LEVELS IN BLOOD STATISTICAL SIGNIFICANCE
(AVERAGE % CHANGE (COMPARING VIRAL LOAD CHANGES PERCENTAGE OF PATIENTS
BETWEEN BASELINE ON TENOFOVIR TO THOSE ON EXPERIENCING SERIOUS ADVERSE
DOSE AND 24 WEEKS) PLACEBO) 1 EVENTS
- ---------------------------- ----------------- ----------------------------- ----------------------------
<S> <C> <C> <C>
Placebo (no drug)........... 34% Reduction Not Applicable 11%
75 mg....................... 64% Reduction P=0.014 2%
150 mg...................... 60% Reduction P=0.001 12%
300 mg...................... 80% Reduction P=0.001 6%
</TABLE>

- ------------------------
1 A smaller number indicates that the results have greater statistical
significance (reliability). In general, results begin to have reliability
when they are less than 0.05.

Based on these promising results, in November 1999 we began enrolling
patients in a 48-week randomized, placebo controlled double blind Phase III
clinical trial of a 300 mg dose of tenofovir DF as a component of combination
therapy. This trial, which is expected to enroll a total of 600 treatment-
experienced patients** at nearly 70 sites in the United States, Europe and
Australia, is designed to provide us with conclusive data regarding the safety
and effectiveness of tenofovir DF. If this data is favorable, it will, together
with data from other late stage clinical trials, form the basis of a marketing
application with the FDA. We cannot be certain that the results of our Phase III
clinical trials will be the same as the Phase II clinical results, particularly
given the much larger patient base and longer dosing period. In addition, even
if these data appear favorable to us, the FDA could reject our application for a
number of reasons including if they require a higher level of safety or
effectiveness, or more data than we anticipated, or if they disagree with our
design or interpretation of these trials.

- ------------------------

* Randomized means that the patients were randomly divided into four dosing
groups and were not selected to be in a particular group. This ensures that the
selection process does not affect the results. Placebo controlled means that one
of these groups received a placebo (a non-therapeutic substitute) instead of the
drug. This allows us to evaluate the health of a patient who received the drug
versus a patient who did not receive the drug. Double blind means that neither
the physician nor the patient were made aware of the particular group that the
patient was in. This ensures that the results within each group are not
influenced by any knowledge of the physician or the patient regarding which
group the patient is in.

**The patients we enroll in this trial have HIV RNA levels between 400 and 1,000
copies/ml and have maintained a stable antiretroviral regimen of not more than
three antiretroviral agents for at least 8 weeks.

6
One of the major challenges in treating HIV-infected patients is drug
resistance. Because many of the existing therapies for treating HIV and AIDS
rely on similar drug processes, patients who have developed a resistance to one
drug often develop a resistance to other drugs within its class. We believe that
tenofovir DF, if eventually approved by the FDA, could be a very important drug
for treatment-experienced patients because available data has shown that
patients do not develop rapid resistance to tenofovir DF and that tenofovir DF
is effective in treating patients who have developed resistance to other
therapies. Current data also show that tenofovir DF does not cause patients to
develop resistance to currently available therapies. We cannot be certain,
however, that the resistance data we may obtain from the much broader and longer
term Phase III clinical trials, which are the data the FDA will consider, will
show similar resistance characteristics to the data we obtained from the more
limited and shorter Phase II clinical trials.

Another major concern in HIV treatment is convenience of dosing. The
combination therapies that are having a very positive impact on the health of
HIV-infected patients require these patients to take numerous different drugs.
Some of these drugs require multiple doses every day taken by injection and many
have food and timing restrictions. This results not only in discomfort and
inconvenience for patients, but also contributes to patients missing doses or
not adhering to their therapy. We believe that nucleotide analogues, like
tenofovir DF, can be administered in a once-daily oral pill without food
restrictions, a dosing form and schedule that may be very appealing to HIV
patients and their physicians.

OTHER POTENTIAL USES FOR TENOFOVIR DF

Tenofovir DF is also being studied for the following potential uses:

- The National Institutes of Health (NIH) is evaluating the use of
intravenous tenofovir DF to prevent transmission of HIV from a mother to
her unborn child; and

- The NIH is evaluating a form of tenofovir DF in a topical gel to prevent
sexual transmission of the HIV virus.

We cannot be certain that these studies will be successful or that tenofovir
DF will be approved for treatment of HIV or these other uses.

In December 1999, we discontinued developing adefovir dipivoxil for treating
HIV-infected patients. This decision followed a recommendation by an FDA
Advisory Panel not to approve a 60 mg dose of adefovir dipivoxil for treating
HIV due primarily to concerns of kidney toxicity that developed late in the
trials, as well as a desire for additional evidence of treatment benefits.
Tenofovir DF has a structure and activity very similar to adefovir dipivoxil.
While tenofovir DF has not been associated with kidney toxicity and has shown
superior treatment benefits in our Phase II clinical trials, we cannot be
certain that the kidney toxicity issues that occurred in the later stages of the
Phase III clinical trials for adefovir dipivoxil will not arise in the Phase III
clinical trials for tenofovir DF or that we will achieve adequate treatment
benefits.

We have an exclusive, worldwide license to patent rights and related
technology for tenofovir DF from IOCB/REGA, and would be obligated to pay a
percentage of any revenues from sales of tenofovir DF to IOCB/REGA. See
"Collaborative Relationships--IOCB/REGA."

ADEFOVIR DIPIVOXIL FOR HEPATITIS B

Hepatitis B is a highly contagious viral infection that can cause acute
liver failure. Some patients develop a chronic infection which over many years
can lead to complications (such as cirrhosis and cancer) that can lead to death.
The Centers for Disease Control and Prevention estimates that there are
approximately 350 million people worldwide who are infected with chronic
hepatitis B, including 1.25 million people in the United States. Adefovir
dipivoxil is a nucleotide analogue reverse

7
transcriptase inhibitor with a structure similar to tenofovir DF. Adefovir
dipivoxil disables the hepatitis B virus by interfering with the activity of
certain enzymes that are necessary for the hepatitis B virus to replicate. In
randomized, double blind, placebo controlled Phase II clinical trials, a 30 mg
dose of adefovir dipivoxil reduced the median hepatitis B viral load by
over 99%.

We have two separate Phase III clinical trials to evaluate the safety and
effectiveness of adefovir dipivoxil in 10 mg and 30 mg orally-administered pills
for treating patients with chronic hepatitis B infection. Both of our Phase III
trails were designed as randomized, double blind, placebo controlled studies and
are being conducted at clinical sites in the United States, Canada, Europe,
Australia and Southeast Asia. One of these trials, which is fully enrolled with
515 patients, is evaluating adefovir dipivoxil for treating patients who test
positive for the hepatitis B "e" antigen, the most common type of hepatitis. The
other trial, which is evaluating adefovir dipivoxil for treating patients with a
type of hepatitis B known as "precore mutant hepatitis B," began enrolling
patients in January 2000 and is expected to enroll approximately 180 patients by
June 30, 2000. Precore mutant hepatitis B is most common in countries of
Southeast Asia and the Mediterranean where evidence suggests that it infects
approximately 30-80% of all hepatitis B patients.

A vaccine is available that can prevent the transmission of hepatitis B, but
it does not cure patients who become infected with the virus. It is expected
that as this vaccine becomes more widely available, the incidence of hepatitis B
will significantly decrease. Existing therapies for treating patients who are
infected with hepatitis B include the drugs Epivir-HBV (a form of lamivudine
that is sold by Glaxo Wellcome) and Intron-A (a form of alpha interferon that is
sold by Schering Plough). Epivir-HBV is an orally-administered drug that
prevents the virus from replicating in patients. Intron-A is an injectable drug
that can provide a reduction in the amount of virus in the blood of some
patients, but is often associated with side effects. We believe that if the FDA
approves adefovir dipivoxil, Epivir-HBV would be its most significant
competition. Of course we cannot be certain that adefovir dipivoxil will be
approved for the treatment of hepatitis B and we cannot determine if adefovir
dipivoxil would be competitive with Epivir-HBV. See "Competition."

As is the case with HIV, drug resistance is a serious problem with drugs
that treat hepatitis B. Available data has shown that hepatitis B patients do
not develop rapid resistance to adefovir dipivoxil and that adefovir dipivoxil
is effective in treating patients who have developed resistance to other
therapies, including Epivir-HBV. Current data also show that adefovir dipivoxil
does not cause patients to develop resistance to currently available therapies.
We believe that the resistance profile of adefovir dipivoxil could make adefovir
dipivoxil an important drug for treating chronic hepatitis B infection. We
cannot be certain, however, that the resistance data we may obtain from the much
broader and longer term Phase III clinical trials on adefovir dipivoxil will
also show these resistance characteristics.

As described above under tenofovir DF, we discontinued development of 60 mg
doses of adefovir dipivoxil for treatment of HIV due to safety and benefit
concerns from the FDA. Studies have shown that adefovir dipivoxil is more
effective against the hepatitis B virus than against the HIV virus, allowing us
to use lower doses that have not shown significant kidney toxicity in our
clinical trials. We have no clinical data demonstrating the safety or benefits
of the 10 mg dose of adefovir dipivoxil for hepatitis B and we cannot be certain
that the broad, long term studies of adefovir dipivoxil at 10 mg and 30 mg doses
will demonstrate, to the satisfaction of the FDA and other regulatory agencies,
that adefovir dipivoxil can be a safe and effective treatment for chronic
hepatitis B.

Hepatitis B is most common in China and Southeast Asian countries. We do not
have regulatory expertise or marketing capacity in these countries. Therefore,
our potential revenues from adefovir dipivoxil for chronic hepatitis B will
depend on our ability to establish a collaborative relationship with a corporate
partner for these activities. We cannot be certain that we will be able to enter
into a collaborative relationship for these activities or that the terms of any
such relationship will be favorable

8
to us. It is also difficult to protect patents in these countries and we could
be adversely affected if we were unable to obtain adequate patent protection for
adefovir dipivoxil in China and Southeast Asia.

We have an exclusive, worldwide license to patent rights and related
technology for adefovir dipivoxil from IOCB/REGA, and would be obligated to pay
a percentage of any revenues from sales of adefovir dipivoxil to IOCB/REGA. See
"Collaborative Relationships--IOCB/REGA."

OTHER PRODUCTS IN DEVELOPMENT

NX 211

NX 211 is a liposomal formulation of lurtotecan, an anti-cancer compound
developed by Glaxo Wellcome. Glaxo Wellcome granted to us the exclusive right to
develop and commercialize NX 211, although Glaxo Wellcome can elect to
participate in this development and commercialization at certain specified times
during the development process. See "Collaborative Relationships--Glaxo
Wellcome--NX 211."

Prior to granting us these development and commercialization rights, Glaxo
Wellcome conducted Phase II clinical trials on non-liposomal lurtotecan as a
treatment for various forms of cancer. These Phase II clinical trials showed
that lurtotecan has anti-cancer activity but we believe that Glaxo Wellcome did
not continue pursuing development of non-liposomal lurtotecan because they were
not convinced that these Phase II clinical trials showed sufficient treatment
benefits at safe doses when compared to other available anti-cancer agents. We
entered into the development and commercialization relationship with Glaxo
Wellcome because we believe that by delivering lurtotecan in a liposome, we may
be able to increase the treatment benefits of lurtotecan and give patients doses
that are both safe and effective.

We have completed a number of preclinical experiments that indicate that
NX 211 can increase the safety and treatment benefit profile of lurtotecan.
Based upon these preclinical experiments, we are currently conducting three
Phase I clinical trials on NX 211 in the Netherlands, Canada and the United
States to determine the safety and pharmaceutical characteristics of NX 211. We
expect that the data from these trials will be available during 2000. If these
Phase I clinical trails show sufficient safety at doses that we believe could
provide significant treatment benefits, we would commence Phase II clinical
trials of NX 211 to evaluate NX 211 in ovarian cancer and small-cell lung cancer
and potentially other cancer types. We cannot accurately predict the outcome of
these clinical trials.

Lurtotecan is in a class of compounds called camptothecins. These compounds
work by disrupting a cell's ability to use "topoisomerase I," an enzyme that is
required for cells to replicate. Studies show that the ability of these
compounds to kill and stop the spread of cancer cells is directly related to the
length of time that cancer cells are exposed to the compound. We believe that by
formulating lurtotecan in a liposome, we may be able to increase its time of
exposure and its treatment benefits.

MIKASOME

MiKasome is a liposomal formulation of amikacin, an antibiotic that is
highly effective in treating serious bacterial infections, but is associated
with serious side effects such as kidney failure, hearing loss and loss of
balance. By encapsulating amikacin in a liposome, we hope to significantly
improve its safety, reduce required dosing, increase its potency and permit its
use for a broader range of infections. We are evaluating MiKasome in Phase II
clinical trials as a potential treatment for complicated urinary tract
infections, as well as other infections that are difficult to treat with
ordinary antibiotics. It is too early for us to determine if these Phase II
clinical trials will show that MiKasome can be a safe and effective treatment
for these diseases.

9
NX 1838

NX 1838 is an aptamer that we identified with our proprietary SELEX
technology. We have studied NX 1838 in Phase I clinical trials as a treatment
for age-related macular degeneration (AMD). AMD is a disease that causes loss of
vision, and is the single leading cause of blindness in the United States and in
other developed countries around the world.

In medical studies, NX 1838 has shown the ability to attach to a protein
associated with AMD and prevent that protein from causing AMD. Because AMD is
not within our strategic focus, we are currently seeking a collaborative partner
to complete the development of and to commercialize NX 1838. It is our intention
to grant a collaborative partner the exclusive right to develop and
commercialize NX 1838 in exchange for the partner paying to us fees and
royalties. The partner would be responsible for all future development of NX
1838. We cannot be certain that we will find an appropriate partner for NX 1838
or that NX 1838 will ever become a commercial product.

OUR SCIENCE

We have approximately 180 research scientists in Foster City, California,
San Dimas California, Boulder Colorado and Cambridge U.K. These scientists seek
to develop new compounds and technologies that we hope will lead to new drug
candidates, and work with existing compounds to develop and test new drug
candidates. The primary focus of our scientific efforts is developing drugs to
treat patients with infectious diseases, including viral infections, fungal
infections and bacterial infections, and cancer.

NUCLEOTIDE ANALOGUES

Our scientists are working with our proprietary compounds known as "small
molecule nucleotide analogues" to develop treatments for viral infections. These
compounds treat viral infections by interfering with the activity of certain
proteins that are necessary for the virus to grow. For example, VISTIDE, which
was developed with one of these nucleotide analogues, inhibits the activity of
certain proteins in the cytomegalovirus that are essential for that virus to
spread. Tenofovir DF and adefovir dipivoxil are nucleotide analogues and work by
inhibiting the activity of reverse transcriptase, a protein necessary for
replication of the HIV virus (tenofovir DF) and the hepatitis B virus (adefovir
dipivoxil). Other viruses we are seeking to treat using nucleotide analogues
include the herpesviruses and poxviruses. Several nucleotide analogues are also
being evaluated in animals for activity against cancer.

We believe that small molecule nucleotide analogues can offer advantages as
therapeutics. These advantages include:

- These molecules have demonstrated the ability to work in both infected and
uninfected cells. This could enable us to develop drugs that not only
treat a patient who is infected with a virus, but that can also prevent a
healthy person from becoming infected in the first place; and

- Drugs developed with these molecules have been shown to have treatment
activity in a patient for longer periods of time than other available
drugs. This could enable us to develop drugs that require less frequent
dosing and that are more convenient for patients.

Given the complexity of drug development, we cannot be certain that any drug
candidates we develop with this science will have any or all of these
advantages. And, even if we do develop drug candidates with some or each of
these advantages, the FDA and other regulatory agencies could reject marketing
approval of these drug candidates for other reasons, including safety and
benefit concerns.

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LIPOSOMES

We also have scientists who are focused on applying our liposomal drug
delivery technology to develop safer, more effective and more convenient drugs.
A lipid is a compound that is made of phospholipids, the basic matter that make
up human cell walls. They are hollow spheres into which drugs can be packed. We
believe that we can influence the way compounds are released and distributed in
the body by placing them in liposomes. This can, in turn, improve the safety and
treatment benefits of that compound. For example, we developed AmBisome by
incorporating amphotericin B in a liposome. Clinical studies have shown that
AmBisome delivers amphotericin B in a manner that results in fewer side effects
and improved treatment benefits over conventional amphotericin B, including
concentrating the drug at the site of the infection, extending the time the drug
remains in the blood stream to prolong the therapeutic effect and reducing
kidney toxicity and injection related reactions.

Our current strategy is to use our liposome technology with compounds we
develop internally and to identify appropriate compounds developed by third
parties for use with this technology. Compounds developed by third parties that
are appropriate for our technology include those that, like amphotericin B, have
proven therapeutic benefits but suffer from significant side effects, or that
suffer from dosing and administration problems. We believe that we can use our
liposomal technology to improve the safety of these drugs while maintaining or
even improving their therapeutic benefits.

We have identified certain generic compounds (compounds that are not
protected by patents) and proprietary compounds owned by third parties that may
benefit substantially from our liposomal technology and have begun formulation
studies for these compounds. In addition, we have discussed, and will continue
to discuss, collaborative relationships with other companies to develop
liposomal formulations of their compounds. We also intend to continue internally
developing products based on our liposomal technology.

HIV PROTEASE INHIBITORS

We are evaluating a number of small molecule compounds known as "protease
inhibitors" for the treatment of HIV. Protease inhibitors act by interfering
with the activity of protease, an enzyme that, like transcriptase, is necessary
for replication of the HIV virus. We have conducted a number of preclinical
experiments on these compounds that have demonstrated anti-viral activity. Our
scientists are trying to increase the safety and treatment benefits of these
compounds and to reduce resistance concerns with these compounds before
conducting further preclinical development.

ANTIBACTERIAL PROGRAM

We have developed a series of small molecule compounds that have shown
antibacterial activity in bacteria cultured in test tubes as well as in
laboratory animal bacterial infection experiments. These compounds have activity
against certain bacteria, including methicillin-resistant STAPHYLOCOCCUS AUREUS,
the bacteria responsible for numerous hospital and community acquired infections
such as pneumonia, surgical wound infections, and skin and soft tissue
infections. This antibiotic resistant strain of STAPHYLOCOCCUS is responsible
for approximately 30% of all STAPHYLOCOCCUS AUREUS infections, and is more
likely to cause serious illness and death because of its antibiotic resistance.
The current focus of this program is to improve the potency of these compounds
and their ability to selectively kill bacteria while causing minimal toxic side
effects in preclinical animal models.

ADENOSINE RECEPTOR REGULATORS

We are working with the National Institute of Diabetes, Digestive and Kidney
Diseases at the National Institutes of Health to study compounds known as
"adenosine receptor agonists and antagonists" for the treatment and prevention
of neurodegenerative disorders (disorders of the brain and upper spine),
particularly stroke. We also intend to evaluate the use of these compounds in

11
inflammatory and allergic conditions. NIH researchers have developed a number of
these compounds, some of which (A3 receptor agonists and antagonists) have shown
therapeutic benefits in stroke.

DRUG DISCOVERY TECHNOLOGIES

We have a technology that we call the "SELEX process" that is used to
identify potential drug candidates. This process works by identifying drug
compounds, known as "aptamers", that tend to bind to the molecule that is
causing the disease. Because these aptamers tend to bind to the disease
molecules, we believe that they can be effective for treating disease at low
doses. We also believe that the SELEX process can reduce the time and cost of
discovering and developing drug candidates. NX 1838 is an example of an aptamer
identified with the SELEX process. See "Other Products in
Development--NX 1838."

MARKETING AND SALES

We established a United States sales force of therapeutic specialists when
we began selling VISTIDE in 1996. As a result of our merger with NeXstar in
July 1999, we also have marketing subsidiaries in the United Kingdom, Germany,
Italy, Spain, France, Portugal and Australia, a marketing operation in Greece,
and sales professionals in the United States to promote and sell AmBisome and
DaunoXome. AmBisome is also sold by Fujisawa in the United States (where we
co-promote the product) and in Canada. Pharmacia & Upjohn promotes and sells
VISTIDE in countries outside of the United States and Hoffmann-La Roche promotes
and sells Tamiflu everywhere it is sold. See "Collaborative Relationships." On
March 6, 2000, we entered into a promotion agreement with The Virco Group. Under
this arrangement, our United States therapeutic specialists will promote Virco's
HIV resistance monitoring services to HIV-treating physicians through the end of
2001.

Our U.S. sales force currently consists of approximately 30 sales
representatives and five regional directors who promote VISTIDE to physicians,
hospitals, clinics, and other healthcare providers who treat AIDS patients,
AmBisome to infectious disease specialists, hospitals, home health care
providers and cancer specialists, and DaunoXome to cancer specialists and
hospitals. The U.S. sales force is supported by a managed care/national accounts
team, and a marketing and sales support staff of approximately 20 people based
at our headquarters in Foster City, California.

Our international marketing subsidiaries are each headed by a general
manager who oversees the operations in the market(s) served by that subsidiary.
We currently have approximately 140 people located mainly in Europe, including
medical, accounting and human resources personnel, who support our international
sales and marketing operations. These subsidiaries also assist in obtaining
regulatory approvals in the countries where they are located.

In the United States, we also sell VISTIDE to wholesalers and specialty
distributors who, in turn, sell the product to physicians, hospitals, clinics,
pharmacies and other healthcare providers. Outside of the United States, we have
agreements with third-party distributors, including distributors in certain of
the countries where we have marketing operations, to promote, sell and
distribute AmBisome and DaunoXome. These international distribution agreements
generally provide that the distributor has the exclusive right to sell AmBisome
and DaunoXome in a particular country or several countries for a specified
period of time.

If tenofovir DF is approved by the FDA for treatment of HIV, a larger sales
force and additional marketing resources would be required to expand our
coverage of healthcare professionals treating HIV patients. It is our current
intention to retain the commercial rights to adefovir dipivoxil for hepatitis B
in the United States and certain countries in Europe and give a marketing
partner rights to this product in Asia and the rest of the world. If we do
retain significant commercial rights to adefovir dipivoxil for hepatitis B and
the product is approved by the FDA, we would need to increase our sales force
and use additional marketing resources to sell this product.

12
The revenues we receive from sales of AmBisome by Fujisawa, sales of VISTIDE
by Pharmacia & Upjohn and sales of Tamiflu by Hoffmann-La Roche depend on the
efforts of these marketing partners. We cannot be certain that the efforts by
these partners will be successful, that our interests and the interests of our
partners will not be in conflict or that any of our partners will not terminate
their relationship with us. See "Collaborative Relationships" and "Risk
Factors."

VISTIDE is returnable in its original, unopened container up to one year
beyond the expiration date or, if damaged when received by the customer. Our
customers may return AmBisome or DaunoXome if the shelf life has expired or if
the product is damaged or defective when it is received by the customer.
AmBisome has an approved shelf life of 36 months in the United States, in Canada
and most European countries. DaunoXome has a shelf life of 52 weeks in the
United States and 40 weeks in Canada and most European countries. Additionally,
certain governmental agency customers are entitled to discounts, and we are
required to provide rebates under state Medicaid programs. To date, returns,
rebates and discounts have not been material. Fujisawa establishes the return
policy for AmBisome in North America and Hoffmann-La Roche establishes the
return policy for Tamiflu.

COLLABORATIVE RELATIONSHIPS

As part of our business strategy, we establish collaborations with other
companies to assist in the clinical development and/or commercialization of
certain of our products and product candidates, and to provide support for our
research programs. We also evaluate opportunities for acquiring products or
rights to products and technologies from other companies that are complementary
to our business. Our existing collaborative relationships are as follows:

HOFFMANN-LA ROCHE

In September 1996, we entered into a collaboration agreement with
Hoffmann-La Roche to develop and commercialize therapies to treat and prevent
the flu. Under this agreement, we granted Hoffmann-La Roche exclusive worldwide
rights to all of our proprietary influenza neuraminidase inhibitors, including
Tamiflu. In October 1999, the FDA approved Tamiflu for marketing and in
November 1999, Hoffmann-La Roche began selling Tamiflu.

As of December 31, 1999, we have received license fees and milestone
payments from Hoffmann-La Roche totaling $29.1 million relating to the execution
of this agreement and to regulatory filings and approvals. Hoffmann-La Roche
also funded all of the research and development costs for Tamiflu, including
reimbursement to us of $26.7 million for the period from January 1, 1997 through
the end of 1999. In addition, under this agreement:

- Hoffmann-La Roche is responsible for pricing, promoting and selling
Tamiflu on a worldwide basis; and

- Hoffmann-La Roche pays us a percentage of its net revenues from sales of
Tamiflu and any other products developed under the collaboration. In
certain circumstances, the amount that Hoffmann-La Roche pays to us may be
reduced by a percentage of the cost of materials they use to manufacture
Tamiflu. We receive payments and recognize revenue from Hoffmann-La Roche
in the quarter following the quarter when the sales were made.

The agreement with Roche terminates on a country-by-country basis as patent
coverage for Tamiflu (or any other product that may be developed under the
agreement) expires. Hoffmann-La Roche has the right to terminate the agreement
prior to expiration at any time upon 12 months notice. See "Our Marketed
Products--Tamiflu."

13
FUJISAWA

In 1991, we entered into an agreement with Fujisawa providing that:

- We have the exclusive right to promote and sell AmBisome in all countries,
except the United States and Canada;

- Fujisawa has the exclusive right to promote and sell AmBisome in Canada;

- In the United States:

- We have the right to co-promote AmBisome with Fujisawa;

- Fujisawa has primary responsibility for promoting and selling
AmBisome in the United States; and

- We receive 20% of the gross profits from the sale of AmBisome in the
United States for our co-promotion efforts;

- We receive payments and recognize revenue from Fujisawa in the month
following the month when the sales are made;

- We would be required to pay Fujisawa a 4% royalty in connection with sales
of AmBisome in significant Asian markets, including Japan, Korea, Taiwan,
China and India; and

- We manufacture AmBisome for all sales. Fujisawa purchases AmBisome from us
for sale in the United States at a price equal to our cost to manufacture
the product and in Canada at that cost plus a specified percentage.

Our agreement with Fujisawa terminates when the last patent covering
AmBisome in the United States or Japan expires.

See "Our Marketed Products--AmBisome."

IOCB/REGA

In 1991 and 1992, we entered into agreements with IOCB/REGA relating to
nucleotide compounds discovered at these institutions. Under these agreements
and later amendments to these agreements:

- We received from IOCB/REGA the exclusive right to manufacture, use and
sell the nucleotide compounds covered by this agreement; and

- We are required to pay to IOCB/REGA a percentage of any net revenues
generated from sales of our products containing these compounds.

The compounds covered by the agreements with IOCB/REGA include cidofovir,
adefovir dipivoxil and tenofovir DF but do not cover Tamiflu or any of our other
compounds in clinical or preclinical development. We are currently making
quarterly payments to IOCB/REGA based upon a percentage of sales of VISTIDE and,
if we receive marketing approval from the FDA, would be obligated to pay
additional amounts upon any future sales of adefovir dipivoxil or tenofovir DF.

The agreements with IOCB/REGA terminate on a country-by-country basis as
patent coverage for any product licensed under the agreements expires. IOCB/REGA
may terminate the licenses under these agreements for a particular product, in a
particular country, if we do not make any sales of that product in that country
within 12 months after regulatory approval. We also have an agreement with
IOCB/REGA that gives us an option to receive an exclusive license to any new
developments by IOCB/ REGA during the term of this agreement. Either of us may
terminate this agreement on six months notice.

14
PHARMACIA & UPJOHN

In August 1996, we entered into an agreement with Pharmacia & Upjohn
relating to VISTIDE. Under this agreement:

- Pharmacia & Upjohn has the exclusive right to market and sell VISTIDE in
all countries outside of the United States;

- We are responsible for maintaining the patents for cidofovir;

- We are required to sell bulk cidofovir to Pharmacia & Upjohn;

- Pharmacia & Upjohn will pay to us a percentage of its net sales of VISTIDE
and any other products developed under the collaboration. We receive
payments and recognize revenue from Pharmacia & Upjohn in the quarter
following the quarter when the sales were made; and

- Pharmacia & Upjohn holds 1,133,786 shares of common stock that it
purchased in connection with this agreement. Pharmacia & Upjohn may not
sell their shares or acquire additional shares of our stock without our
approval until June 2002.

Our agreement with Pharmacia & Upjohn terminates:

- on a country-by-country basis as patent coverage for VISTIDE expires; or

- upon six months notice by Pharmacia & Upjohn.

See "Our Marketed Products--VISTIDE."

SUMITOMO PHARMACEUTICALS CO., LTD.

In 1996, we entered into an agreement with Sumitomo Pharmaceuticals Co.,
Ltd. that gave Sumitomo the right to develop and market AmBisome in Japan.
Sumitomo paid to us $7 million at the time we entered into the agreement and
$3 million in March 1998 when it made a regulatory filing to sell AmBisome in
Japan. Under the terms of this agreement:

- Sumitomo is required to make a payment of $4 million to us if AmBisome is
approved for sale in Japan;

- Sumitimo is required to pay to us a percentage of any revenue they
generate from sales of AmBisome; and

- If approved in Japan, we would manufacture AmBisome for sale by Sumitomo
in Japan. The price that we would charge Sumitomo for the supply of
AmBisome and the percentage of revenues that they would be required to pay
to us would be determined by the price of AmBisome in Japan.

This agreement terminates on the later of:

- Ten years after Sumitomo begins selling AmBisome in Japan; or

- The date the last patent for AmBisome in Japan expires.

15
PROLIGO L.L.C.

We own a 49% interest in Proligo L.L.C., a company that manufactures
oligonucleotides. We also have agreements with Proligo and SKW Americas, Inc.
(the owner of the other 51% of Proligo) relating to the ownership, operations
and funding of Proligo. Under these agreements:

- We contributed a total of $4.9 million to Proligo to fund its operations
in late 1999 and early 2000;

- SKW Americas will have the right to purchase our ownership interest in
Proligo for a 90-day period beginning on July 29, 2001 for an amount equal
to the fair market value of that interest in 1999; and

- Over the next four years, SKW Americas is obligated to pay to us $400,000;
and

- Proligo agreed to manufacture oligonucleotides for us. We would pay them
an amount equal to their manufacturing cost plus a pre-determined
percentage for those oligonucleotides.

Proligo will dissolve and any remaining assets will be distributed to its
owners on August 2, 2028, unless the owners of Proligo at that time decide to
extend the term. The agreement relating to the manufacture and supply of
oligonucleotides expires on August 15, 2008.

SCHERING A.G.

In 1993, we entered into agreements with Schering A.G. Under these
agreements Schering has funded our discovery, research, and development of
aptamers for "IN VIVO DIAGNOSTICS"--diagnosing diseases and other conditions in
humans and animals. Schering funded $250,000 for these activities in 1999.
Schering discontinued funding and we discontinued further research and
development under these agreements in 1999.

Under these agreements, Schering was given the right to develop and
commercialize the aptamers we developed in the collaboration as IN VIVO
diagnostic agents or "radiotherapeutics."

If Schering decides to commercialize any product with these aptamers:

- Schering would be required to make certain payments to us upon achieving
certain goals relating to regulatory approval for that product. These
payments could total up to $6 million for each product developed; and

- Schering would be required to pay to us a percentage of any revenues it
receives from selling the product.

We have the right to develop and commercialize products based on aptamers
that Schering discovered under this agreement that are not IN VIVO diagnostic
agents or radiotherapeutics. If we did commercialize a product resulting from
this collaboration, we would be required to pay Schering a percentage of any
revenues we receive from sales of those products. The rights to use and develop
products granted under these agreements and the obligations to pay revenues from
selling products survive termination of the agreements.

GLAXO WELLCOME--NX 211

In May 1998, we entered into agreements with Glaxo Wellcome giving us rights
to Glaxo Wellcome's proprietary compound lurtotecan, and granting Glaxo Wellcome
rights to use our SELEX process to identify aptamers for therapeutic uses.

16
Under the agreement relating to lurtotecan, we are developing NX 211, a
liposomal formulation of lurtotecan. This agreement provides that:

- We have the exclusive right to develop and commercialize NX 211 unless
Glaxo Wellcome elects to participate in these activities;

- We may be required to make payments to Glaxo Wellcome if we achieve
certain development goals relating to the regulatory approval of NX 211:

- If Glaxo Wellcome elects to participate in the development and
commercialization of NX 211 in certain countries, we would not need
to make these payments; and

- If NX 211 is approved for marketing, we would be required to pay to Glaxo
Wellcome a percentage of any revenues we generate from sales of NX 211 in
any country where Glaxo Wellcome does not participate in the development
and commercialization of NX 211;

- Glaxo Wellcome can exercise its right to participate in these development
and commercialization activities after we have completed Phase II clinical
trials on NX 211 and at the time we commence Phase III clinical trials on
NX 211; and

- If Glaxo Wellcome elects to participate in these development and
communication activities:

- At the time it elects, it would be required to pay to us a fee and in
some cases a percentage of the money that we spent to develop NX 211,

- If it elects to participate in certain countries, including the
United States, the major countries in Europe and in Australia, we
would have the right to sell NX 211 with Glaxo Wellcome in those
countries. We would share with Glaxo Wellcome any profits in any
territories where we sell NX 211 with Glaxo Wellcome, and

- If it elects to participate in Asia, including Japan and any of the
other countries where we do not have the right to sell the product
with Glaxo Wellcome, Glaxo Wellcome would have the exclusive right to
promote and sell NX 211 in those countries. Glaxo Wellcome would be
required to pay to us a percentage of revenues in any territories
where it has the exclusive right to sell NX 211.

NX 211 is still in an early stage of development. We cannot be certain that
the data we generate from our Phase I clinical trial for NX 211 will support
Phase II clinical trials of NX 211 or that if we complete Phase II clinical
trials, that those results would support a Phase III program.

This agreement terminates on the later of:

- Ten years after Glaxo Wellcome begins selling NX 211; or

- The date the last patent for NX 211 expires.

GLAXO WELLCOME--SELEX

At the time we entered into the agreement with Glaxo Wellcome relating to NX
211, we also entered into an agreement giving Glaxo Wellcome the non-exclusive
right to use our SELEX technology for five years to identify aptamers.

Under this agreement, if Glaxo Wellcome identifies an aptamer having certain
characteristics, they may elect to enter into an additional agreement with us to
use the SELEX process to develop and commercialize that aptamer. Under this
additional agreement:

- Glaxo Wellcome would be required to pay to us a fee at the time we enter
into the agreement;

17
- Glaxo Wellcome would be required to make payments to us based on achieving
certain goals relating to the regulatory approval of any product they
develop based on the aptamer; and

- Glaxo Wellcome would be required to pay to us a percentage of any revenues
they may generate from sales of any product they develop based on the
aptamer.

This agreement terminates on May 27, 2003 except:

- Glaxo Wellcome can extend this agreement for additional one year periods
in which case Glaxo Wellcome would be required to pay to us an appropriate
fee; and

- Glaxo Wellcome can terminate this agreement earlier at any time on
90 days notice to us.

SOMALOGIC, INC.

In November 1999, we entered into an agreement with Somalogic, Inc., a
company formed by Larry Gold, the founder of NeXstar, relating to SELEX
technology. Under this agreement:

- We gave Somalogic the exclusive right to use SELEX technology to make and
sell in vitro diagnostic products (diagnostic products that are not used
in a person or animal);

- We sold to Somalogic certain patents and materials relating to in vitro
diagnostics, including robotic SELEX machines;

- We have the right to use the other drug discovery technology that is the
subject of this agreement internally to study diseases and in our drug
development and clinical trial programs; and

- Somalogic paid to us the first installment of a fee at the time we entered
into the agreement and is obligated to pay to us a second and final
installment in November 2000.

This agreement terminates on the later of:

- On a country by country basis as patent coverage for this drug discovery
technology expires; or

- November 2024.

INTERNATIONAL DISTRIBUTION AGREEMENTS

We have agreements with distributors in Western Europe, Eastern Europe,
South America, the Middle East and Africa that grant these distributors the
exclusive right to sell AmBisome, and in some cases DaunoXome, in a particular
country or countries for a specified period of time. These agreements also
provide for collaborative efforts between us and the distributor for obtaining
regulatory approval for the product in the particular country and for marketing
the product in the country. Most of these agreements establish a price that the
distributor must pay for our product and require us to deliver quantities of the
product ordered by the distributor.

ACADEMIC AND CONSULTING RELATIONSHIPS

To supplement our research and development efforts, as part of our regular
business we enter into arrangements with universities and medical research
institutions. These arrangements often provide us with rights to patents, patent
applications and technology owned by these institutions in return for payments
and fees relating to our use of these rights.

UNIVERSITY OF COLORADO

We have an ongoing collaborative arrangement with the University of Colorado
at Boulder relating to our SELEX technology. Under this arrangement:

18
- The University of Colorado at Boulder has given us all of its present and
future rights to:

- inventions covered by patents and patent applications for SELEX
technology;

- improvements to SELEX technology it makes or discovers;

- oligonucleotides or other molecules it makes using SELEX technology;

- results of certain research; and

- computer software related to SELEX technology.

- We are required to pay to the University of Colorado at Boulder:

- 2% of the revenues we generate from our sales of SELEX-derived
products;

- 15% of any amounts we receive from a third party that are based upon
sales by those third parties of SELEX-derived products; and

- 5% of other payments we receive from third parties as a result of
certain arrangements we have with those third parties to develop and
sell SELEX-derived products.

MANUFACTURING

We manufacture AmBisome and DaunoXome in commercial quantities in two
separate but adjacent facilities in San Dimas, California. The Medicines Control
Agency of the United Kingdom has approved both of these facilities to
manufacture AmBisome and DaunoXome for commercial use. The FDA has approved both
these facilities to manufacture AmBisome but only one of these facilities to
manufacture DaunoXome for distribution in the United States. To import AmBisome
and DaunoXome into the European Union, we own a manufacturing facility in
Dublin, Ireland where we perform quality control testing, final labeling and
packaging for the European Union and elsewhere.

We hire third parties to manufacture our non-liposomal drugs for clinical
and commercial purposes, including VISTIDE, adefovir dipivoxil tablets and
tenofovir DF tablets. Hoffmann-La Roche manufactures Tamiflu. We have no
commercial-scale manufacturing facilities for our non-liposomal products that
are qualified under the FDA's current Good Manufacturing Practices, and we have
no current plans to establish these facilities. AmBisome is sold as a
freeze-dried product and we currently hire third parties to freeze dry some of
the product. We are installing additional freeze drying capacity and when this
equipment has been installed and approved by regulatory authorities, we expect
that we will no longer rely on third parties for this process. We cannot be
certain that the third parties we rely on will perform their obligations
effectively and on a timely basis. If these third parties do not perform
effectively and timely, our clinical trials or regulatory filings could be
delayed or we could be unable to deliver our products to customers on a timely
basis and this would adversely affect our operating results.

We use commercially available materials and equipment to manufacture our
products. Currently, we obtain the amphotericin B, daunorubicin HCl and
cholesterol that we use to manufacture AmBisome and DaunoXome from single
approved suppliers. We have one supplier that has been approved by the FDA to
manufacture the cidofovir used in VISTIDE and a single FDA approved supplier for
the final drug product. We manufacture the active ingredient in tenofovir DF in
small quantities at our own facilities and in larger quantities through a
contract manufacturer. The final tenofovir DF and adefovir tablets used in our
clinical trials are manufactured at three contract manufacturing sites. If any
of these sites we use were interrupted for any reason, our ability to complete
our clinical trials or ship our products would be impaired and this would
adversely affect us.

For our non-liposomal products in particular, we will need to develop
additional manufacturing capabilities and establish additional third party
suppliers in order to manufacture sufficient quantities of

19
our product candidates to complete clinical trials and to manufacture sufficient
quantities of any candidates that are approved for commercial sale. If we are
unable to develop manufacturing capabilities internally or contract for large
scale manufacturing with third parties on acceptable terms for our non-liposomal
products, our ability to conduct large-scale clinical trials, and meet customer
demand for commercial products, would be adversely affected. Manufacturing
liposomal products is a particularly complex process and any new liposomal
product we develop will require unique and complex variations in our
manufacturing process.

We believe that the technology we use to manufacture our products and
compounds is proprietary. For our non-liposomal products, we have licensed this
technology to contract manufacturers to enable them to manufacture the products
and compounds for us. We have agreements with these manufacturers that are
intended to restrict them from using or revealing this technology but we cannot
be certain that these manufacturers will comply with these restrictions. In
addition, these manufacturers could develop their own technology related to the
work they perform for us that we may need to manufacture our products or
compounds. We could be required to enter into an agreement with that
manufacturer if we wanted to use that technology ourselves or allow another
manufacturer to use that technology. The manufacturer could refuse to allow us
to use their technology or could demand terms to use their technology that are
not acceptable.

PATENTS AND PROPRIETARY RIGHTS

Patents and other proprietary rights are extremely important to our
business. If we have a properly designed and enforceable patent it can be more
difficult for our competitors to use our technology to create competitive
products and more difficult for our competitors to obtain a patent that prevents
us from using technology we create. As part of our business strategy, we
actively seek patent protection both in the U.S. and internationally and file
additional patent applications, when appropriate, to cover improvements in our
compounds, products and technology. We also rely on trade secrets, internal
know-how, technological innovations and agreements with third parties to
develop, maintain and protect our competitive position. Our ability to be
competitive will depend on the success of this strategy.

We have a number of patents, patent applications and rights to patents
related to our compounds, products and technology but we cannot be certain that
issued patents will be enforceable or provide adequate protection or that
pending patent applications will result in issued patents. The following table
shows the actual or estimated patent expiration dates in the United States and
Europe for the primary patents that cover the compounds in our marketed products
and our product candidates:

<TABLE>
<CAPTION>
PRODUCTS U.S. PATENT EXPIRATION EUROPEAN PATENT EXPIRATION
- -------- ---------------------- --------------------------
<S> <C> <C>
AmBisome........................................... 2016* 2008
Tamiflu............................................ 2016 2016*
VISTIDE............................................ 2010 2012
DaunoXome.......................................... 2009 2008

PRODUCT CANDIDATES
- ---------------------------------------------------
tenofovir DF....................................... 2017 2017*
adefovir dipivoxil................................. 2014 2011
MiKasome........................................... 2015* 2006
NX 211............................................. 2013* 2012*
NX 1838............................................ 2012* *
</TABLE>

- ------------------------

* Applications pending.

Patents covering VISTIDE, adefovir, and lurtotecan (the active ingredient in
NX 211) are held by third parties. We acquired exclusive rights to these patents
in the agreements we have with these

20
parties. See "Collaborative Relationships." Patents do not cover the active
ingredients in AmBisome, DaunoXome and MiKasome. Instead, we hold patents to the
liposomal formulations of these compounds and protect these formulations through
trade secrets. We do not have patent filings covering adefovir dipivoxil in
China or in certain other Asian countries, although we do have applications
pending in various Asian countries, including China, which relate to specific
forms and formulations of adefovir dipivoxil. Asia is a major market for
hepatitis B therapies.

We may obtain patents for our compounds many years before we obtain
marketing approval for them. This limits the time that we can prevent other
companies from developing these compounds and therefore reduces the value of the
product. However, we can apply for patent term extensions. For example,
extensions for the patents on VISTIDE have been applied for or granted in the
United States and a number of European countries, compensating in part for
delays in obtaining marketing approval. Similar patent term extensions may be
available for other products that we are developing but we cannot be certain we
will obtain them.

It is also very important that we do not infringe patents or proprietary
rights of others and that we do not violate the agreements that grant
proprietary rights to us. If we do infringe patents or violate these agreements,
we could be prevented from developing or selling products or from using the
processes covered by those patents or agreements, or we could be required to
obtain a license from the third party allowing us to use their technology. We
cannot be certain that, if required, we could obtain a license to any
third-party technology or that we could obtain one at a reasonable cost. If we
were not able to obtain a required license, we could be adversely affected. In
August 1998, we were sued by Chiron who claimed that we were infringing their
patents for hepatitis C and related technology. In, December 1999, we agreed to
the terms of a settlement agreement with Chiron and, as a result, we agreed to
cease certain development activities relating to hepatitis C and made a one-time
settlement payment of $0.4 million to Chiron.

Patents relating to pharmaceutical, biopharmaceutical and biotechnology
products, compounds and processes like those that cover our existing compounds,
products and processes and those that we will likely file in the future, do not
always provide complete or adequate protection. Future litigation or
reexamination proceedings regarding the enforcement or validity of our existing
patents or any future patents could invalidate our patents or substantially
reduce their protection. In addition, our pending patent applications and patent
applications filed by our collaborative partners may not result in the issuance
of any patents or may result in patents that do not provide adequate protection.
As a result, we may not be able to prevent third parties from developing the
same compounds and products that we are developing. Also, in the United States,
patent applications are maintained in secrecy until patents are issued so we
cannot be certain that we are the inventor of technologies covered by our
pending patent applications or that we were the first to file patent
applications for those inventions.

We also rely on unpatented trade secrets and improvements, unpatented
internal know-how and technological innovation. In particular, a great deal of
our liposomal manufacturing expertise, which is a key component of our liposomal
technology, is not covered by patents but is instead protected as a trade
secret. We protect these rights mainly through confidentiality agreements with
our corporate partners, employees, consultants and vendors. These agreements
provide that all confidential information developed or made known to an
individual during the course of their relationship with us will be kept
confidential and will not be used or disclosed to third parties except in
specified circumstances. In the case of employees, the agreements provide that
all inventions made by the individual while employed by us will be our exclusive
property. We cannot be certain that these parties will comply with these
confidentiality agreements, that we would have adequate remedies for any breach,
or that our trade secrets will not otherwise become known or be independently
discovered by our competitors. Under some of our research and development
agreements, inventions discovered in certain cases become jointly owned by us
and our corporate partner and in other cases become the exclusive property of
one of us. It can be difficult to determine who owns a particular invention and
disputes could arise regarding those inventions.

21
COMPETITION

Our products and development programs target a number of diseases and
conditions, including fungal infections, viral infections and cancer. There are
many commercially available products for these diseases, and a large number of
companies and institutions are spending considerable amounts of money and
resources to develop additional products to treat these diseases. Our current
products compete with other available products based primarily on:

- product performance;

- safety;

- tolerability;

- acceptance by doctors;

- patient compliance;

- patent protection;

- ease of use;

- price;

- insurance and other reimbursement coverage;

- distribution;

- marketing; and

- adaptability to various modes of dosing.

Any other products we market in the future will also compete with products
offered by our competitors. If our competitors introduce data that shows
improved characteristics of their products, improve or increase their marketing
efforts or simply lower the price of their products, sales of our products could
decrease. We also cannot be certain that any products we develop in the future
will compare favorably to products offered by our competitors, or that our
existing or future products will compare favorably to any new products that are
developed by our competitors. Our ability to be competitive also depends upon
our ability to attract and retain qualified personnel, obtain patent protection
or otherwise develop proprietary products or processes and secure sufficient
capital resources for the substantial period that it takes to develop a product.

22
In markets where AmBisome has been approved as a first time therapy, it
competes against traditional amphotericin B, which is made by Bristol-Myers
Squibb Company and numerous generic manufacturers, and we expect to face more
competition from new antifungal products, including those produced or currently
being developed by major pharmaceutical companies, including Pfizer, Inc. and
Merck. There is also a number of other lipid-based amphotericin B products that
have been approved in the United States and throughout Europe, including
Abelcet, which is sold by The Liposome Company (who recently announced that they
will be acquired by Elan Corporation) and Amphotec, which is sold by ALZA
Corporation. These products compete against AmBisome as both primary and
secondary therapy and have been offered at prices that are less than AmBisome's
price.

Tamiflu competes with Relenza, an anti-flu drug that is sold by Glaxo
Wellcome, in the United States and Europe. Relenza is a neuraminidase inhibitor
that is delivered as an orally-inhaled dry powder. In addition, Johnson &
Johnson and Biocryst are developing a neuraminidase inhibitor anti-flu drug that
will represent significant competition when and if the FDA approves it. This
drug being developed by Johnson and Johnson and Biocryst may be administered as
a once-daily pill as opposed to Tamiflu, which must be taken twice daily. We
cannot be certain that Tamiflu will compare favorably to this drug based on
performance, price, length of dosing, side effects or any other criteria.
Johnson & Johnson began Phase III clinical trials of this compound in
February 2000 and it could be on the market as early as the winter 2000-2001 flu
season.

VISTIDE competes with a number of drugs that also treat CMV retinitis. These
drugs include:

- Ganciclovir, a drug that is sold in intravenous and oral formulations by
Roche Laboratories and as an ocular implant by Bausch & Lomb Incorporated;

- Foscarnet, an intravenous drug sold by AstraZeneca; and

- Formivirsen, a drug that is injected directly into the eye that is sold by
CibaVision.

In addition, we are aware that several other companies are developing drugs
to treat CMV retinitis.

If approved, tenofovir DF will face substantial competition. A number of
drugs to treat HIV infection and AIDS are currently sold or are in advanced
stages of clinical development, including 14 products currently sold in the
United States. Among the companies that are significant competitors in the
HIV/AIDS market are Glaxo Wellcome, Bristol-Myers Squibb, Hoffmann-La Roche,
Agouron Pharmaceuticals, Merck & Co. and DuPont Pharma.

Lamivudine is a drug that was developed by Glaxo Wellcome in collaboration
with Biochem Pharma. Lamivudine is sold in the United States, China and several
other countries and has been shown to be effective in treating patients with
hepatitis B. If adefovir dipivoxil is approved to treat hepatitis B, lamivudine
will be significant competition.

There are drugs that have been approved, or are awaiting approval, for the
treatment of Kaposi's sarcoma in the United States and Europe, including one
that is sold in a liposomal formulation. These drugs compete or are expected to
compete with DaunoXome.

A number of companies are pursuing the development of technologies
competitive with our research programs. These competing companies include
specialized pharmaceutical firms and large pharmaceutical companies acting
either independently or together with biopharmaceutical companies. Furthermore,
academic institutions, government agencies and other public and private
organizations conducting research may seek patent protection and may establish
collaborative arrangements for competitive products and programs.

We anticipate that we will face increased competition in the future as our
competitors introduce new products to the market and new technologies become
available. We cannot determine if existing

23
products or new products that our competitors develop will be more effective, or
more effectively marketed and sold, than any that we develop. Competitive
products could render our technology and products obsolete or noncompetitive
before we recover the money and resources we used to develop these products.

GOVERNMENT REGULATION

Our operations and activities are subject to extensive regulation by
numerous government authorities in the United States and other countries. In the
United States, drugs are subject to rigorous FDA regulation. The Federal Food,
Drug and Cosmetic Act and other federal and state statutes and regulations
govern the testing, manufacture, safety, effectiveness, labeling, storage,
record keeping, approval, advertising and promotion of our products. As a result
of these regulations, product development and approval is very expensive and
time consuming.

The FDA must approve a drug before it can be sold in the United States. The
general process for this approval is as follows:

PRE-CLINICAL TESTING

Before we can test a drug candidate in humans, we must study the drug in
laboratory experiments and in animals to generate data to support the drug's
potential safety and benefits. We submit this data to the FDA in a
"investigational new drug application" seeking their approval to test the
compound in humans.

CLINICAL TRIALS

If the FDA accepts the investigational new drug application, we study the
drug in human clinical trails to determine if the drug is safe and effective.
These clinical trials involve three separate phases, which often overlap, and
can take many years and are very expensive. These three phases, which are
themselves subject to considerable regulation, are as follows:

- PHASE I. The drug is given to a small number of healthy human subjects or
patients to test for safety, dose tolerance, pharmacokinetics, metabolism,
distribution, and excretion.

- PHASE II. The drug is given to a limited patient population to determine:

- the effect of the drug in treating the disease,

- the best dose of the drug, and

- the possible side effects and safety risks of the drug.

- PHASE III. If a compound appears to be effective and safe in Phase II
clinical trials, Phase III clinical trials are commenced to confirm those
results. Phase III clinical trials are long-term, involve a significantly
larger population, are conducted at numerous sites in different geographic
regions and are carefully designed to provide reliable and conclusive data
regarding the safety and benefits of a drug. It is not uncommon for a drug
that appears promising in Phase II clinical trials to fail in the more
rigorous and reliable Phase III clinical trials.

FDA APPROVAL PROCESS

If we believe that the data from the Phase III clinical trials show an
adequate level of safety and effectiveness, we file a "new drug application"
with the FDA seeking approval to sell the drug for a particular use. The FDA
will review the new drug application and often will hold a public hearing where
an independent advisory committee of expert advisors asks additional questions
regarding the drug. This committee makes a recommendation to the FDA that is not
binding on the FDA but is

24
generally followed by the FDA. If the FDA agrees that the compound has a
required level of safety and effectiveness for a particular use, it will allow
us to sell the drug in the United States for that use. It is not unusual,
however, for the FDA to reject an application because it believes that the drug
is not safe enough or effective enough, or because the FDA does not believe that
the data submitted is reliable or conclusive.

At any point in this process, the development of a drug could be stopped for
a number of reasons including safety concerns and lack of treatment benefit. We
cannot be certain that any Phase I, Phase II or Phase III clinical trials that
we are conducting, including those for tenofovir DF for HIV and for adefovir
dipivoxil for chronic hepatitis B, or any that we conduct in the future, will be
completed successfully or within any specified time period. We may choose or the
FDA may require us to delay or suspend our clinical trials at any time if it
appears that the patients are being exposed to an unacceptable health risk or if
the drug candidate does not appear to have sufficient treatment benefit.

The FDA may also require us to complete additional testing, provide
additional data or information, improve our manufacturing processes, procedures
or facilities or require extensive post-marketing testing and surveillance to
monitor the safety or benefits of our product candidates if they determine that
our new drug application does not contain adequate evidence of the safety and
benefits of the drug. In addition, even if the FDA approves a drug, it could
limit the uses of the drug. Approvals can also be withdrawn if the FDA does not
believe that we are complying with regulatory standards or if problems are
uncovered or occur after approval.

In addition to obtaining FDA approval for each drug, the manufacturing
facilities for any drug we sell, including those of companies who manufacture
our drugs for us as well as our own, must be approved by the FDA and are subject
to periodic inspections by the FDA. Foreign establishments that manufacture
products to be sold in the United States must also be approved by the FDA and
are subject to periodic regulatory inspection. Manufacturing facilities located
in California, including our San Dimas facility and Foster City facility, also
must be licensed by the State of California in compliance with local regulatory
requirements.

Drugs that treat serious or life-threatening diseases and conditions that
are not adequately addressed by existing drugs may be designated as "fast track"
products by the FDA and may be eligible for priority (six month) review and
accelerated approval. Drugs receiving accelerated approval must be monitored in
post-marketing clinical trials in order to confirm the safety and benefits of
the drug. Certain products we are developing, including tenofovir DF for HIV,
may qualify as fast track products and be eligible for accelerated approval. We
have not determined if we would seek "fast track" status of these products if
they qualified or the impact of this status on the timing or likelihood of
approval of any of these potential products or those of our competitors.

We are also subject to other federal, state and local regulations regarding
workplace safety and protection of the environment. We use hazardous materials,
chemicals, viruses and various radioactive compounds in our research and
development activities and cannot eliminate the risk of accidental contamination
or injury from these materials. Any misuse or accidents involving these
materials could lead to significant litigation, fines and penalties.

Drugs are also subject to extensive regulation outside of the United States.
In the European Union, there is a centralized approval procedure that authorizes
marketing of a product in all countries in the European Union (which includes
most major countries in Europe). If this procedure is not used, under a
decentralized system, an approval in one country of the European Union can be
used to obtain approval in another country of the European Union under a
simplified application process. After approval under the centralized procedure,
pricing and reimbursement approvals are also required in most countries. VISTIDE
was approved by the European Union under the centralized procedure. Tamiflu is
being reviewed under the centralized procedure but has not yet been approved in
Europe.

25
PRICING AND REIMBURSEMENT

Insurance companies, HMOs and other third-party payors and some governments,
seek to limit the amount we can charge for our drugs. For example, in certain
foreign markets, pricing negotiations are often required to obtain approval of a
product, and in the United States there have been, and we expect that there will
continue to be, a number of federal and state proposals to implement drug price
control. In addition, managed care organizations are becoming more common in the
United States and will continue to seek lower drug prices. The announcement of
these proposals or efforts can cause our stock price to lower, and if these
proposals are adopted, our revenues would decrease.

Our ability to sell our drugs also depends on the availability of
reimbursement from governments and private insurance companies. These
governments and insurance companies often demand rebates or predetermined
discounts from list prices. For example, a significant proportion of VISTIDE
sales is subject to reimbursement by government agencies, resulting in
significant discounts from list price and rebate obligations. We expect that
other products we are developing, particularly for AIDS indications, will be
subject to reimbursement issues. We cannot be certain that any of our other
products that obtain regulatory approval will be reimbursed by these government
and insurance companies.

Regulatory approval of prices is generally required in most foreign
countries. In particular, certain countries will condition their approval of a
product on the agreement of the seller not to sell that product for more than a
certain price in that country and in the past have required price reductions
after or in connection with product approval. We cannot be certain that
regulatory authorities in the future will not establish lower prices or that any
regulatory action reducing the price of our products in any one country will not
have the practical effect of requiring us to reduce our prices in other
countries.

HUMAN RESOURCES

As of December 31, 1999, we had approximately 760 full-time employees. We
believe that we have good relations with our employees.

RISK FACTORS

In evaluating our business, you should carefully consider the following
risks in addition to the other information in this report. Any of the following
risks could materially and adversely affect our business, operating results and
financial condition.

ANY SIGNIFICANT REDUCTION IN AMBISOME SALES WOULD SIGNIFICANTLY REDUCE OUR
OPERATING INCOME, AND COULD REQUIRE US TO SCALE BACK OUR MANUFACTURING
OPERATIONS AND REDUCE OUR SALES FORCE. AmBisome sales for the year ended
December 31, 1999 were approximately $129.2 million. During the same period,
sales of VISTIDE and DaunoXome, were approximately $5.9 million and
$4.8 million, respectively. Our corporate partner, Hoffmann-La Roche, began
selling Tamiflu in November 1999 but we have not yet recognized any revenues
from this product for 1999 sales. In March 2000, we received a payment from
Hoffman-La Roche in the amount of $5.4 million for sales in 1999, which will be
recognized as royalty revenue in the first quarter of 2000. We expect that
revenues from sales of Tamiflu in 2000 will increase, therefore decreasing the
percentage of our total revenues from sales of AmBisome, although we cannot
predict with any certainty what our actual revenues from either AmBisome or
Tamiflu will be in 2000. We do, however, expect that revenues from sales of
AmBisome in 2000 will continue to constitute a substantial majority of our total
product revenues in 2000.

Accordingly, for the foreseeable future, we expect that we will continue to
rely on sales of AmBisome to support our existing manufacturing and sales
infrastructure and to provide operating income to offset a significant portion
of our administrative, research and development expenditures. Any significant
reduction in sales of AmBisome, whether as a result of the introduction of
competitive

26
products or otherwise, would have a material adverse effect on us, including the
possibility that we would have to scale back our manufacturing operations and
reduce our sales force. There are several products on the market that compete
with AmBisome and are generally priced lower than AmBisome. In addition, there
are other potentially competitive products in clinical development by major
pharmaceutical companies.

TAMIFLU IS A NEW DRUG AND IT IS TOO EARLY TO DETERMINE IF IT WILL GAIN
SIGNIFICANT MARKET ACCEPTANCE. Most people who become infected with the flu use
over-the-counter drugs to treat the flu symptoms, and rely on their immune
system to fight the infection. Tamiflu is in a class of drugs that is a new
approach to treating the flu. Tamiflu is available only by prescription and its
primary benefit is that it reduces the duration of the illness by an average of
1.3 days. Patients may be reluctant to visit a physician or seek a prescription
drug for the flu, physicians may be reluctant to prescribe a flu drug and
government reimbursers and private insurance companies may refuse to pay for an
anti-flu drug. In order for Tamiflu to be successful, our marketing partner
Hoffmann-La Roche will need to increase awareness of this new approach to
treating the flu and change the attitudes of patients, physicians, nurses,
pharmacies, government reimbursers and insurance companies regarding flu
treatment. We cannot be certain that Hoffmann-La Roche will be successful in
these efforts.

The 1999-2000 flu season was the first flu season that Tamiflu was
available. It is too early to determine if Tamiflu will achieve significant
market acceptance. If Tamiflu does not achieve significant market acceptance, we
would be adversely affected.

WE DEVELOP DRUGS TO TREAT AIDS AND AIDS-RELATED CONDITIONS, AND THEREFORE WE
CAN BE ADVERSELY AFFECTED BY CHANGES IN THE REGULATORY AND COMMERCIAL
ENVIRONMENT FOR AIDS THERAPIES. Several of our products and products in
development address AIDS or AIDS-related conditions. These products include
VISTIDE (cidofovir injection) for CMV retinitis, tenofovir DF for HIV and AIDS,
and DaunoXome for HIV-associated Kaposi's sarcoma. The medical, regulatory and
commercial environment for AIDS therapies changes quickly and often in ways that
we are unable to accurately predict. We develop our AIDS products based upon
current policy and the current marketplace for AIDS therapies, as well as our
prediction of future policy and the future marketplace for these therapies. Our
business will be subject to substantial risk because these policies and markets
change quickly and unpredictably and in ways that could have a material adverse
impact on our ability to obtain regulatory approval and commercial acceptance of
these products.

WE MAY NOT RECEIVE APPROVAL FOR EXPANDED USES FOR EXISTING PRODUCTS OR
APPROVAL OF ADDITIONAL PRODUCTS. Additional regulatory approvals will be needed
to expand the uses for which AmBisome may be marketed in the countries where it
is already approved, and those approvals may or may not be obtained. Similarly,
to the extent that we seek to expand the indications for DaunoXome beyond
Kaposi's sarcoma, the drug may not be effective for the treatment of other
diseases, and we may never obtain additional regulatory approvals. In December
1999, Bausch & Lomb terminated a collaborative program studying the use of an
eye drop formulation of cidofovir, the active ingredient in VISTIDE, for the
potential treatment of certain eye viruses, because they did not believe the
compound achieved their performance objectives.

27
OUR OPERATIONS DEPEND ON COMPLIANCE WITH COMPLEX FDA AND COMPARABLE
INTERNATIONAL REGULATIONS. FAILURE TO OBTAIN BROAD APPROVALS ON A TIMELY BASIS
OR TO ACHIEVE CONTINUED COMPLIANCE COULD DELAY COMMERCIALIZATION OF OUR PRODUCTS
AND ADVERSELY AFFECT US. The products that we will develop and sell must be
approved and will be subject to extensive regulation by the FDA and comparable
agencies in other countries. We are continuing clinical trials for both AmBisome
and DaunoXome for currently approved and additional uses. We are also conducting
clinical trials for five other products, adefovir dipivoxil for hepatitis B
infection, tenofovir DF, MiKasome, NX 211 and NX 1838. We anticipate that we
will conduct a variety of clinical trials and file for marketing approval of
additional products over the next several years. These products may fail to
receive marketing approval on a timely basis, or at all. In addition, these
products may receive marketing approvals that place limitations on their uses.
These failures, delays or limitations, as well as other regulatory changes,
actions and recalls, could delay commercialization of any products and adversely
affect our results of operations.

In addition, even after our products are marketed, the products and their
manufacturers are subject to continual review. Later discovery of previously
unknown problems with our products, our own manufacturing or the production by
third-party manufacturers may result in restrictions on our products or the
manufacture of our products, including withdrawal of the products from the
market.

RESULTS OF CLINICAL TRIALS AND APPROVAL OF PRODUCTS ARE UNCERTAIN, AND WE
MAY BE DELAYED IN OR PROHIBITED FROM SELLING OUR PRODUCTS. We have a number of
potential products that have reached the development stage. These potential
products include adefovir dipivoxil for hepatitis B, tenofovir DF, MiKasome, NX
211 and NX 1838. We will be required to demonstrate the safety and effectiveness
of these and any other products we develop in each intended use through
extensive preclinical studies and clinical trials in order to obtain regulatory
approval of these products. The results from preclinical and early clinical
studies do not always accurately predict results in later, large-scale clinical
trials for several reasons, including:

- preliminary results may not be indicative of effectiveness;

- further clinical trials may not achieve the desired result; and

- further clinical trials may reveal unduly harmful side effects or may show
the drugs to be less effective than other drugs or delivery systems for
the desired indications.

Even successfully completed large-scale clinical trials may not result in
marketable products for several reasons, including:

- the potential products are not shown to be safe and effective;

- regulatory authorities disagree with the results or design of our studies
and trials;

- required regulatory approvals are not obtained;

- the potential products are too difficult to develop into commercially
viable products; or

- the potential products do not obtain market acceptance.

On November 1, 1999, an FDA Advisory Committee recommended against approval
of our application to approve a 60 mg dose of adefovir dipivoxil to treat AIDS.
Kidney toxicity associated with this 60 mg dose, as well as a desire for
additional data, were the major concerns of this committee. Following this
recommendation, we were informed by the FDA that they would not approve our
application unless we obtained additional data that satisfied the concerns
raised by this committee. Based on these discussions, we terminated our
development of adefovir dipivoxil for the treatment of AIDS. We are using 10 and
30 milligram doses of adefovir dipivoxil in our Phase III clinical trials of
adefovir dipivoxil for hepatitis B. We believe that these lower doses will not
result in the kidney toxicity experienced with 60 milligrams and that adefovir
dipivoxil can be effective in treating hepatitis B at this lower dose. We cannot
be certain, however, that these lower doses will be both safe enough and have

28
sufficient treatment benefits to receive FDA approval. Tenofovir DF is in the
same class of drugs as adefovir dipivoxil. And, while we have not yet
experienced kidney toxicity in our clinical trials of tenofovir DF, the kidney
toxicity in our clinical trials of adefovir dipivoxil for AIDS did not arise
until the later stages of our clinical trials. We cannot be certain that similar
toxicity issues will not arise later in our clinical trials of tenofovir DF. A
number of companies in our industry have suffered similar setbacks in advanced
clinical trials despite promising results in earlier trials. In the end, we may
be unable to develop additional marketable products.

DELAYS IN PATIENT ENROLLMENT FOR CLINICAL TRIALS COULD INCREASE COSTS AND
DELAY REGULATORY APPROVALS. The rate of completion of our clinical trials will
depend on the rate of patient enrollment. There will be substantial competition
to enroll patients in clinical trials for our drugs in development. This
competition has delayed our clinical trials in the past. In addition, recent
improvements in existing drug therapy, particularly for AIDS, hepatitis B and
certain cancers, may make it more difficult for us to enroll patients in our
clinical trials as the patient population may choose to enroll in clinical
trials sponsored by other companies or choose alternative therapies. Delays in
planned patient enrollment can result in increased development costs and delays
in regulatory approvals.

OUR PRODUCT DEVELOPMENT EFFORTS MAY NOT YIELD MARKETABLE PRODUCTS DUE TO
RESULTS OF STUDIES OR TRIALS, FAILURE TO ACHIEVE REGULATORY APPROVALS OR MARKET
ACCEPTANCE, PROPRIETARY RIGHTS OF OTHERS OR MANUFACTURING ISSUES. Our success
depends on our ability to successfully develop and obtain regulatory approval to
market new pharmaceutical products. A significant portion of the research that
we will conduct will involve new and unproven technologies. Development of a
product requires substantial technical, financial and human resources even if
the product is not successfully completed.

Our potential products may appear to be promising at various stages of
development yet fail to reach the market for a number of reasons, including:

- lack of sufficient treatment benefit or unacceptable toxicity during
preclinical studies or clinical trials;

- failure to receive necessary regulatory approvals;

- existence of proprietary rights of third parties; and

- inability to develop manufacturing methods that are efficient,
cost-effective and capable of meeting stringent regulatory standards.

WE MAY UNDERESTIMATE DEVELOPMENT COSTS, ADVERSELY AFFECTING OUR
BUSINESS. Due to uncertainties that are part of the development process, we may
underestimate the costs associated with the development of a potential product.
Delays or unanticipated increases in costs of development or failure to obtain
regulatory approval or market acceptance for our products could adversely affect
our operating results.

WE DEPEND ON RELATIONSHIPS WITH OTHER COMPANIES FOR RESEARCH FUNDING,
CLINICAL DEVELOPMENT, SALES AND MARKETING PERFORMANCE AND REVENUES. FAILURE TO
MAINTAIN THESE RELATIONSHIPS WOULD NEGATIVELY IMPACT OUR BUSINESS. We rely on a
number of significant collaborative relationships with major pharmaceutical
companies for our research funding, clinical development and/or sales and
marketing performance. These include collaborations with Fujisawa USA Inc.,
Glaxo Wellcome, Hoffmann-La Roche, Pharmacia & Upjohn, Schering AG and Sumitomo
Pharmaceuticals Co. Inc. We also only rely on international distributors for
sales of AmBisome in certain countries. Reliance on collaborative relationships
poses a number of risks, including:

- we will not be able to control whether our corporate partners will devote
sufficient resources to our programs or products;

- disputes may arise in the future with respect to the ownership of rights
to technology developed with corporate partners;

29
- disagreements with corporate partners could lead to delays in or
termination of the research, development or commercialization of product
candidates, or result in litigation or arbitration;

- contracts with our corporate partners may fail to provide significant
protection or may fail to be effectively enforced if one of these partners
fails to perform;

- corporate partners have considerable discretion in electing whether to
pursue the development of any additional products and may pursue
alternative technologies or products either on their own or in
collaboration with our competitors; and

- corporate partners with marketing rights may choose to devote fewer
resources to the marketing of our products than they do to products of
their own development.

Given these risks, there is a great deal of uncertainty regarding the
success of our current and future collaborative efforts. If these efforts fail,
our product development or commercialization of new products could be delayed or
revenue from existing products, including Tamiflu, AmBisome and VISTIDE, could
decline.

OUR RIGHTS TO MARKET AMBISOME IN THE UNITED STATES AND CANADA ARE LIMITED BY
AN AGREEMENT WITH FUJISAWA. FAILURE OF FUJISAWA TO EFFECTIVELY MARKET AMBISOME
MAY REDUCE REVENUES. Our rights to market AmBisome in the United States and
Canada are subject to an agreement with Fujisawa Healthcare, Inc. Under the
terms of this agreement, we have sole marketing rights to AmBisome in all
countries except the United States and Canada, but must pay royalties in
connection with sales in most significant Asian markets, including Japan. We
co-promote AmBisome with Fujisawa in the United States. We manufacture AmBisome
for sale in the United States and Canada and sell AmBisome to Fujisawa at cost
in the United States and at cost plus a specified percentage in Canada. Fujisawa
collects all revenues from AmBisome sales in the United States and pays us 20%
of the gross profits from such sales. The success of AmBisome in the United
States will be dependent primarily on the efforts of Fujisawa and in Canada the
success of AmBisome will depend entirely on Fujisawa. If Fujisawa fails in its
efforts, potential revenues from the sales of AmBisome may be substantially
reduced.

FAILURE OF HOFFMANN-LA ROCHE TO EFFECTIVELY MARKET TAMIFLU WOULD REDUCE
POTENTIAL REVENUES. Hoffmann-La Roche has sole responsibility for promoting and
selling Tamiflu on a worldwide basis and we have no control over their
activities. Therefore, we are relying on the efforts of Hoffmann-La Roche for
any revenues we receive from the sale of Tamiflu. If Hoffmann-La Roche does not
dedicate sufficient resources to the promotion of Tamiflu, or if Hoffmann-La
Roche fails in its marketing efforts, the royalties we receive from the sale of
Tamiflu would decrease and we would be adversely affected.

INABILITY TO ESTABLISH FUTURE SUCCESSFUL COLLABORATIVE RELATIONSHIPS MAY
IMPAIR OUR FINANCIAL RESULTS. We may seek future collaborative relationships
with corporate partners to fund some of our research and development expenses
and to develop and commercialize some of our potential products. For example, we
have been in discussions with several potential corporate partners about
collaborative development and commercialization of adefovir dipivoxil for
hepatitis B, particularly in Asian territories. Further, we anticipate that our
revenues from collaborative agreements will continue to be affected by existing
agreements, as well as by the timing of drug development programs of our
corporate partners. We may not be able to negotiate acceptable collaborative
arrangements in the future, and any arrangements we do negotiate may not be
successful. If we fail to establish additional collaborative relationships, we
will be required to undertake research, development, marketing and manufacturing
of our proposed products at our own expense.

WE HAVE A HISTORY OF LOSSES, EXPECT TO OPERATE AT A LOSS FOR THE FORESEEABLE
FUTURE AND MAY NEVER BE PROFITABLE. We have never been profitable on a
full-year basis. We may never become profitable. At December 31, 1999, our
accumulated deficit was $449.2 million. Our losses have resulted principally

30
from expenses associated with our research and development programs and, to a
lesser extent, from sales, general and administrative expenses. Our product
sales and royalty revenues are derived from sales of AmBisome, VISTIDE and
DaunoXome and royalty arrangements related to AmBisome and VISTIDE. In addition,
we continue to integrate Gilead and NeXstar and unforeseen costs could require
us to spend substantially more financial resources that we have anticipated.

OUR EXISTING PRODUCTS AND PRODUCTS UNDER DEVELOPMENT MAY NOT BE ACCEPTED BY
PHYSICIANS, INSURERS AND PATIENTS. Many of our products in development, if
approved for marketing, would have no established market. The ability of these
products to achieve and sustain market acceptance will depend on the receipt and
scope of regulatory approvals and whether or not government authorities and
managed care organizations will adequately reimburse patients who use these
products.

In addition, we need to convince the medical and patient advocacy community
of:

- the effectiveness of these products in treating disease;

- the safety of these products when administered to patients; and

- the advantages of these products over competitive products.

Physicians, patients, patient advocates, payors and the medical community in
general may not accept and use any products that we may develop. If our products
are not accepted, our results of operations will suffer.

MANY OTHER COMPANIES ARE TARGETING THE SAME DISEASES AND CONDITIONS AS WE
ARE. COMPETITIVE PRODUCTS FROM OTHER COMPANIES COULD SIGNIFICANTLY REDUCE THE
MARKET ACCEPTANCE OF OUR PRODUCTS. Our products and development programs target
a number of diseases and conditions, including viral infections, fungal
infections, bacterial infections and cancer. There are many commercially
available products for these diseases. Certain of these products are
well-established therapies and have generated substantial sales. In addition, a
large number of companies and institutions are conducting well-funded research
and development activities directed at developing treatments for these diseases.
Products currently on the market and those under development by our competitors
could make our technology and products obsolete or noncompetitive. We expect
that competition for the treatment of these diseases will increase in the future
as new products enter the market and advanced technologies become available. We
will also be competing to license or acquire technology from other companies.

Most of our competitors and potential competitors have substantially greater
resources than we do. Those resources include superior product development
capabilities and financial, scientific, manufacturing, marketing, managerial and
human resources. These competitors may achieve superior patent protection,
obtain key technology, receive regulatory approval or achieve product
commercialization earlier than us.

THE SIGNIFICANTLY GREATER RESOURCES OF THE MARKETING ORGANIZATIONS OF LARGE
PHARMACEUTICAL COMPANIES COULD HINDER OUR ABILITY TO COMPETE SUCCESSFULLY. Our
products compete, and the products we may develop are likely to compete, with
products of other companies that currently have extensive and well-funded
marketing and sales operations. Because these companies are capable of devoting
significantly greater resources to their marketing efforts, our marketing or
sales efforts may not compete successfully against the efforts of these other
companies.

OUR EXISTING PRODUCTS ARE SUBJECT TO REIMBURSEMENT FROM GOVERNMENT AGENCIES
AND OTHER THIRD PARTIES. PHARMACEUTICAL PRICING AND REIMBURSEMENT PRESSURES MAY
REDUCE PROFITABILITY. Successful commercialization of our products depends, in
part, on the availability of governmental and third party payor reimbursement
for the cost of such products and related treatments. Government health
administration authorities, private health insurers and other organizations
generally provide reimbursement. Government authorities and third-party payors
increasingly are challenging the price of

31
medical products and services, particularly for innovative new products and
therapies. This has resulted in lower average sales prices. For example, a
majority of our sales of AmBisome, VISTIDE and DaunoXome are subject to
reimbursement by government agencies, resulting in significant discounts from
list price and rebate obligations. If Tamiflu is approved for sale in Europe,
its success will also depend largely on obtaining government reimbursement in
Europe because in many European countries, including the United Kingdom and
France, patients are reluctant to pay for prescription drugs out of their own
pockets. We also expect that several of our products in development,
particularly for AIDS indications, will have a similar reimbursement profile, if
they receive regulatory approval. Even if reimbursement is available,
reimbursement policies may adversely affect our ability to sell our products on
a profitable basis.

In addition, in many international markets, governments control the prices
of prescription pharmaceuticals. In these markets, once marketing approval is
received, pricing negotiation can take another six to twelve months or longer.
Product sales, attempts to gain market share or introductory pricing programs of
our competitors could require us to lower our prices in these countries, which
could adversely affect our results of operations.

MOST OF OUR PRODUCT SALES ARE MADE IN EUROPE, AND CURRENCY FLUCTUATIONS MAY
IMPAIR OUR FINANCIAL RESULTS. A majority of our product sales are made in
Europe, with 51.3% of our product sales for the year ending December 31, 1999
occurring in the United Kingdom, France, Germany, Italy and Spain. In most
significant European markets, we sell AmBisome and DaunoXome in the currency of
the country in which they are sold. Accordingly, the prices of these products in
U.S. Dollars will vary as the value of the U.S. Dollar fluctuates against these
foreign currencies or the Euro. Increases in the value of the U.S. Dollar
against foreign currencies may reduce our U.S. Dollar return on the sale of our
products. In addition, although we implement hedging techniques with respect to
our foreign currency accounts receivable, these techniques do not eliminate the
effects of foreign currency fluctuations with respect to anticipated revenues.
Therefore our future results will continue to be affected by foreign currency
fluctuations.

WE MAY NOT BE ABLE TO OBTAIN EFFECTIVE PATENTS TO PROTECT OUR TECHNOLOGIES
FROM USE BY COMPETITORS, AND PATENTS OF OTHER COMPANIES COULD REQUIRE US TO STOP
USING OR PAY FOR THE USE OF REQUIRED TECHNOLOGY. Our success will depend to a
significant degree on our ability to:

- obtain patents and licenses to patent rights;

- preserve trade secrets; and

- operate without infringing on the proprietary rights of others.

We have rights to United States and foreign issued patents and have filed
and will continue to file patent applications in the United States and abroad
relating to our technologies. There is a risk, however, that patents may not
issue from any of these applications or that the patents will not be sufficient
to protect our technology. Patent applications in the United States are
confidential until a patent is granted. As a result, we would not know if our
competitors filed patent applications for technology covered by our pending
applications. We also cannot be certain that we were the first to invent the
technology that is the subject of our patent applications. Competitors may have
filed patent applications or received patents and may obtain additional patents
and proprietary rights that block or compete with our patents.

We do not have patent filings covering adefovir dipivoxil per se in China or
in certain other Asian countries, although we do have applications pending in
various Asian countries, including China, which relate to various forms and
formulations of adefovir dipivoxil. Asia is a major market for hepatitis B
therapies, one of the potential indications for adefovir dipivoxil. We may
obtain patents for certain products many years before marketing approval is
obtained for those products. Because patents have a

32
limited life, which may begin to run prior to commercial sale, the commercial
value of the product may be limited.

Our competitors may file patent applications covering our technology. If so,
we may have to participate in interference proceedings or litigation to
determine the right to a patent. Litigation and interference proceedings are
expensive even if successful. In August 1998, we were served with a patent
infringement lawsuit filed by Chiron Corporation alleging that our research
infringes Chiron's patents covering the hepatitis C NS-3 protein and gene
sequences and their use in screening for potential hepatitis C therapeutics. We
have ceased our activities with respect to the NS-3 protein and have settled the
litigation with Chiron.

Our success depends in large part on our ability to operate without
infringing upon the patents or other proprietary rights of third parties. If we
infringe patents of others, we may be prevented from commercializing products or
may be required to obtain licenses from these third parties. We cannot be
certain that we would be able to obtain alternative technologies or any required
license. Even if we were to obtain such technologies or licenses, we cannot be
certain that the terms would be reasonable. If we fail to obtain such licenses
or alternative technologies, we may be unable to develop some or all of our
products.

In addition, we use significant proprietary technology and rely on
unpatented trade secrets and proprietary know-how to protect certain aspects of
our production and other technologies. Our trade secrets may become known or
independently discovered by our competitors.

MANUFACTURING PROBLEMS COULD DELAY PRODUCT SHIPMENTS AND REGULATORY
APPROVALS. For VISTIDE, adefovir dipivoxil and tenofovir DF, we rely on third
parties for the manufacture of bulk drug substance and final drug product for
clinical and commercial purposes. Hoffmann-La Roche is responsible for
manufacturing Tamiflu and if they encounter problems in this process, our
revenues from the sales of Tamiflu could decrease. We depend on these third
parties to perform their obligations effectively and on a timely basis. If these
third parties fail to perform as required, our clinical trials or submission of
products for regulatory approval may be delayed. These delays could impair our
ability to deliver commercial products on a timely basis and could impair our
competitive position.

We manufacture AmBisome and DaunoXome at our facilities in San Dimas,
California. Our only formulation and manufacturing facilities are in San Dimas,
California; although we own a manufacturing facility in Ireland that performs
certain quality control testing, labeling and packaging, and we use third
parties to fill and lyophilize (freeze dry) certain batches of product as
alternate contract suppliers. In the event of a natural disaster, including an
earthquake, equipment failure, strike or other difficulty, we may be unable to
replace this manufacturing capacity in a timely manner and would be unable to
manufacture AmBisome and DaunoXome to meet market needs.

WE MAY NOT BE ABLE TO OBTAIN MATERIALS NECESSARY TO MANUFACTURE OUR
PRODUCTS. Many of the materials that we utilize in our operations are made at
only one facility. For example, we depend on single suppliers for high quality
amphotericin B, daunorubicin HC1 and high quality cholesterol, each of which is
used in the manufacture of our liposome products. We have qualified only one
supplier with the FDA for the bulk drug substance used in VISTIDE and one
different supplier for the final drug product. A shutdown in any of these
facilities due to technical, regulatory or other problems, resulting in an
interruption in supply of these materials, could have an adverse impact on our
financial results. While we have established a second source of bulk drug
substance supply for VISTIDE, we have not yet qualified this source with the FDA
and cannot be certain that the FDA will approve this second source. Because the
suppliers of key components and materials must be named in the new drug
application filed with the FDA for a product, significant delays can occur if
the qualification of a new supplier is required. If supplies from our suppliers
were interrupted for any reason, we could be unable to ship AmBisome, VISTIDE or
DaunoXome, or supply any of our products in development for clinical trials.

33
WE HAVE LIMITED EXPERIENCE IN MANUFACTURING NON-LIPOSOMAL PRODUCTS AND COULD
BE ADVERSELY AFFECTED IF WE FAIL TO DEVELOP MANUFACTURING CAPACITY. For some of
our potential products, we will need to develop further our production
technologies for use on a larger scale in order to conduct clinical trials and
produce such products for commercial sale at an acceptable cost. We cannot be
certain that we will be able to implement any of these developments
successfully.

The manufacturing process for pharmaceutical products is highly regulated,
and regulators may shut down manufacturing facilities that they believe do not
comply with regulations. The FDA's current Good Manufacturing Practices are
extensive regulations governing manufacturing processes, stability testing,
record-keeping and quality standards. In addition, our manufacturing operations
are subject to routine inspections by regulatory agencies and similar
regulations are in effect in other countries.

OUR BUSINESSES MAY GIVE RISE TO PRODUCT LIABILITY CLAIMS NOT COVERED BY
INSURANCE OR INDEMNITY AGREEMENTS. The testing, manufacturing, marketing and
use of AmBisome, VISTIDE and DaunoXome, as well as products in development,
involve substantial risk of product liability claims. These claims may be made
directly by consumers, healthcare providers, pharmaceutical companies or others.
Although we maintain product liability insurance, a single product liability
claim could exceed the coverage limits, and multiple claims are possible. If
that happens, the insurance coverage we have may not be adequate. A successful
product liability claim in excess of our coverage could require us to pay
substantial amounts. This could adversely affect our results of operations.
Moreover, the amount and scope of any coverage may be inadequate to protect us
in the event of a successful product liability claim. In the future such
insurance may not be renewed at an acceptable cost or at all. If liability
insurance becomes unobtainable, our ability to clinically test and to market our
products could be significantly impaired.

Additionally, we are required by governmental regulations to test our
products even after they have been sold and used by patients. As a result of
such tests, we may be required to, or may determine that, we should recall
products already in the market. Subsequent testing and product recalls may
increase our potential exposure to product liability claims.

OUR USE OF HAZARDOUS MATERIALS, CHEMICALS, VIRUSES AND RADIOACTIVE COMPOUNDS
EXPOSES US TO POTENTIAL LIABILITIES. Our research and development involves the
controlled use of hazardous materials, chemicals, viruses and various
radioactive compounds. Although we believe that our safety procedures for
handling and disposing of such materials comply with the standards prescribed by
state and federal regulations, we cannot completely eliminate the risk of
accidental contamination or injury from these materials. In the event of such an
accident, we could be held liable for significant damages or fines.

ITEM 2. PROPERTIES

Our corporate headquarters, including our principal executive offices and
certain of our research facilities are located in Foster City, California. At
this location, we lease approximately 221,600 square feet of space in eight
proximately located buildings. One of the leases covering 59,039 square feet of
space in this group of buildings expires in December 2003 and there are no
renewal options. The remaining leases expire in March and September 2006 and we
have an option to renew all of these leases for two additional five-year
periods.

In Boulder, Colorado, we sublease a facility of approximately 32,000 square
feet of office space, which we use as administrative offices. This sublease
expires in July 2003. We also lease approximately 60,000 square feet of space,
which we use both as research laboratories and as administrative offices. This
lease expires in October 2001, but can be renewed at our option for two
successive five-year periods.

We also occupy a facility in San Dimas, California under a noncancelable
operating lease that expires in May 2003 with two five-year renewal options.
This facility has 51,500 square feet of space and houses research and
development activities, manufacturing and certain administrative functions.

34
The facility has been inspected by the State of California for compliance with
"current Good Manufacturing Practices" and is licensed by the State of
California for pharmaceutical manufacturing. The license is renewable annually.
The San Dimas facility has been registered for the commercial production of
AmBisome and DaunoXome by the Medicines Control Agency in the United Kingdom
(MCA) and the FDA.

We also lease a second manufacturing facility adjacent to our other facility
in San Dimas, California. This lease expires in November 2003 with two five-year
renewal options. This second facility in San Dimas provides in excess of 70,000
square feet of space, including approximately 45,000 square feet of
manufacturing space, and is our primary injectable pharmaceutical production
plant. Both the MCA and the FDA have approved the manufacture of AmBisome at
this facility.

Finally, the Company owns a 9,700 square foot facility located in Dublin,
Ireland, in which the quality control testing, final labeling and packaging are
currently being conducted for AmBisome and DaunoXome for the European Union and
elsewhere.

ITEM 3. LEGAL PROCEEDINGS

On August 11, 1997, we reached a settlement with The Liposome Company, Inc.
in which we each agreed to dismiss all legal proceedings involving patents
related to our liposomal formulation of amphotericin B. In the settlement
agreement, The Liposome Company agreed not to sue us in connection with the
worldwide production and sales of AmBisome and gave us rights to use some of
their patents. Under the terms of the settlement Agreement, we are required to
make payments based on AmBisome sales over the next several years.

In August 1998, we were sued by Chiron who claimed that we were infringing
their patents for hepatitis C and related technology. In December 1999, we
agreed to the terms of a settlement agreement with Chiron and, as a result, we
made a one-time settlement payment of $0.4 million to Chiron.

We are also a party to various other legal actions that arose in the
ordinary course of our business. We do not believe that any of these other legal
actions will have any significant impact on our business.

ITEM 4. SUBMISSION OF MATTERS TO A VOTE OF SECURITIES HOLDERS

Not applicable.

35
PART II

ITEM 5. MARKET FOR REGISTRANT'S COMMON STOCK AND RELATED STOCKHOLDER MATTERS

Our common stock is traded on The Nasdaq Stock Market under the symbol
"GILD." The following table sets forth for the periods indicated the high and
low prices per share of our common stock on The Nasdaq Stock Market. These
prices represent quotations among dealers without adjustments for retail
mark-ups, mark-downs or commissions, and may not represent prices of actual
transactions.

<TABLE>
<CAPTION>
1999 CLOSING HIGH CLOSING LOW
- ---- -------------- --------------
<S> <C> <C>
First Quarter........................................ $ 56 3/4 $ 35 3/4
Second Quarter....................................... $ 52 1/4 $ 36 1/16
Third Quarter........................................ $ 92 3/8 $ 52 1/8
Fourth Quarter....................................... $ 73 25/32 $ 37 1/4

<CAPTION>
1998
- ----
First Quarter. $ 42 5/8 35
<S> <C> <C>
Second Quarter....................................... $ 43 1/4 $ 31 5/8
Third Quarter........................................ $ 30 3/8 $ 18 1/4
Fourth Quarter....................................... $ 41 1/16 $ 18 3/4
</TABLE>

As of February 25, 2000, we had 44,388,828 shares of common stock
outstanding held by approximately 586 stockholders of record. We have not paid
dividends on our common stock since our inception and we do not anticipate
paying any in the foreseeable future.

ITEM 6. SELECTED FINANCIAL DATA

GILEAD SCIENCES, INC.
SELECTED CONSOLIDATED FINANCIAL DATA(1)
(IN THOUSANDS, EXCEPT PER SHARE DATA)

<TABLE>
<CAPTION>
NINE MONTHS
YEARS ENDED DECEMBER 31, ENDED
--------------------------------------------- DECEMBER 31,
1999 1998 1997 1996 1995 (2)
--------- --------- --------- --------- -------------
<S> <C> <C> <C> <C> <C>
CONSOLIDATED STATEMENT OF OPERATIONS
DATA:
Total revenues....................... $ 168,979 $ 151,119 $ 132,258 $ 122,121 $ 50,744
Total costs and expenses............. 239,838 230,631 220,480 181,403 114,800
Loss from operations................. (70,859) (79,512) (88,222) (59,282) (64,056)
Net loss............................. (66,486) (44,758) (72,893) (45,614) (59,225)
Basic and diluted net loss per common
share.............................. $ (1.55) $ (1.09) $ (1.85) $ (1.21) $ (1.97)
Common shares used to calculate basic
and diluted net loss per common
share.............................. 42,826 41,015 39,432 37,641 30,187
</TABLE>

36
<TABLE>
<CAPTION>
DECEMBER 31,
----------------------------------------------------------
1999 1998 1997 1996 1995
--------- --------- --------- --------- ----------
<S> <C> <C> <C> <C> <C>
CONSOLIDATED BALANCE SHEET DATA:
Cash, cash equivalents and marketable
securities......................... $ 294,394 $ 348,743 $ 387,361 $ 338,354 $ 182,657
Working capital...................... 324,104 359,555 396,810 332,352 180,568
Total assets......................... 436,808 487,764 516,989 450,540 275,376
Long-term obligations................ 5,253 8,883 9,658 18,120 13,330
Convertible subordinated
debentures......................... 79,533 80,000 80,000 -- --
Accumulated deficit.................. (449,232) (382,746) (337,988) (265,095) (219,481)
Total stockholders' equity (3)....... 297,292 333,699 357,726 374,649 228,931
</TABLE>

- ------------------------

(1) Periods prior to the year ended December 31, 1999 have been restated to
reflect the merger with NeXstar Pharmaceuticals, Inc. on July 29, 1999,
which has been accounted for as a pooling of interests.

(2) In October 1995, we changed our fiscal year end from March 31 to
December 31, effective with the nine months ended December 31, 1995.

(3) No dividends have been declared or paid on our common stock.

ITEM 7. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
OF OPERATIONS

OVERVIEW

We were incorporated in Delaware on June 22, 1987, and are an independent
biopharmaceutical company that seeks to provide accelerated solutions for
patients and the people who care for them. We discover, develop, manufacture and
commercialize proprietary therapeutics for challenging infectious diseases
(viral, fungal and bacterial diseases) and cancer. Currently, we market
AmBisome-Registered Trademark-((amphotericin B) liposome for injection), an
antifungal agent, DaunoXome-Registered Trademark- (daunorubicin citrate liposome
injection), a drug approved for the treatment of Kaposi's sarcoma, and
VISTIDE-Registered Trademark- (cidofovir injection) for the treatment of
cytomegalovirus ("CMV") retinitis. Hoffmann-La Roche Inc. ("Roche") markets
Tamiflu-TM- (oseltamivir phosphate) for the treatment of influenza, under a
collaborative agreement. In addition, we are developing products to treat
diseases caused by human immunodeficiency virus ("HIV"), hepatitis B virus
("HBV"), bacterial infections and cancer.

On July 29, 1999, we entered into a business combination with NeXstar
Pharmaceuticals, Inc. ("NeXstar"). The business combination has been accounted
for as a pooling of interests and our historical consolidated financial
statements for all years prior to the business combination have been restated in
the accompanying consolidated financial statements to include the financial
position, results of operations and cash flows of NeXstar.

FORWARD-LOOKING STATEMENTS AND RISK FACTORS

The following discussion of our financial condition and results of
operations contains forward-looking statements within the meaning of Section 27A
of the Securities Act and Section 21E of the Exchange Act that involve risks and
uncertainties. Our actual financial and operating results could differ
materially from our expectations. Some of the factors that could cause these
differences are listed below. These factors, as well as other factors that could
cause or contribute to these differences, are described in more detail under
"Risk Factors" beginning on page 26 of this report.

37
MERGER INTEGRATION.  We continue to integrate Gilead with NeXstar and
unforeseen integration issues could disrupt our business or require us to expend
substantially more financial resources than anticipated.

REGULATORY PROCESS. The FDA and foreign agencies could reject or limit the
commercialization of our products for a number of reasons. If these agencies
reject or limit the commercialization of our products, our financial results
would be adversely affected.

AMBISOME SALES. We rely on sales of AmBisome for a significant portion of
our operating income. If revenues from sales of AmBisome decrease, our operating
income would decrease.

MARKET ACCEPTANCE OF PRODUCTS. If our products do not achieve and sustain
market acceptance, our results of operations will suffer. Tamiflu is in a new
class of drugs that represent a new approach to treating the flu. In order for
Tamiflu to achieve significant market acceptance, our marketing partner,
Hoffmann-La Roche, must change attitudes toward flu treatment.

COLLABORATIONS. We depend on collaborations for the development and
commercialization of certain products and for revenue, including the
collaboration with Hoffmann-La Roche for sales of Tamiflu and the collaboration
with Fujisawa for sales of AmBisome in the United States and Canada. These
collaborations could fail for a number of reasons. We will also seek additional
collaborations, including a collaboration for adefovir dipivoxil for the
treatment of Hepatitis B virus infection. If our collaborations fail or if we
are unable to establish additional collaborations, our financial results would
be adversely affected.

FOREIGN CURRENCY FLUCTUATIONS. A significant portion of our sales is in
foreign currency. Increases in the value of the U.S. Dollar against foreign
currencies can reduce our U.S. Dollar return on these sales and negatively
impact our financial condition.

UNCERTAIN FINANCIAL RESULTS. We expect that our financial results will
continue to fluctuate from quarter to quarter and that such fluctuations may be
substantial. We have never been profitable on a full-year basis and may never
achieve or sustain profitability. As of December 31, 1999, our accumulated
deficit was $449.2 million.

REVENUES

We had total revenues of $169.0 million, $151.1 million and $132.3 million
for the years ended December 31, 1999, 1998 and 1997, respectively. Total
revenues include revenues from net product sales, net royalties and contracts,
including research and development ("R&D") collaborations.

Net product sales revenue was $139.9 million, $114.2 million and
$100.9 million for 1999, 1998 and 1997, respectively. Such revenues are
increasingly derived from sales of AmBisome, which represented 92%, 91% and 83%
of total product sales revenue in 1999, 1998 and 1997, respectively. We also
recognized product sales revenue of $5.9 million and $4.8 million from sales of
VISTIDE and DaunoXome, respectively, during 1999. A significant majority of our
product sales, particularly sales of AmBisome, are denominated in foreign
currencies. In future periods, the combined levels of sales of VISTIDE and
DaunoXome are expected to be relatively flat as compared to 1999 amounts.

During 1999, 1998 and 1997, we recorded net royalty revenue of
$10.4 million, $7.3 million and $1.6 million, respectively. During this
three-year period, the most significant source of royalty revenue was from sales
of AmBisome in the United States by Fujisawa Healthcare, Inc. ("Fujisawa"),
under a co-promotion arrangement we have with them. During the fourth quarter of
1999, we began recognizing royalty revenues from Fujisawa's sales of AmBisome in
the month following the month in which the related product sales occur. Prior to
the fourth quarter of 1999, we recognized this royalty revenue in the month the
sales occurred. We have recognized net royalty revenue of $8.3 million from

38
Fujisawa in 1999, which represents 11 months of sales by Fujisawa to customers.
Net royalty revenues recognized from Fujisawa's sales of AmBisome in 1998 and
1997 were $4.8 million and $0.7 million, respectively. Substantially all of the
remaining net royalty revenue recognized in each year of this three-year period
represents royalties from sales of VISTIDE by Pharmacia & Upjohn S.A.
("Pharmacia & Upjohn") outside the United States. In future periods, royalties
from sales of VISTIDE are expected to be relatively flat. In October 1999, the
U.S. Food and Drug Administration approved Tamiflu for the treatment of
influenza A & B in adults. We co-developed Tamiflu with F. Hoffmann-La Roche
Ltd. and Hoffmann-La Roche Inc. (collectively, "Roche"), which owns the
worldwide commercial rights to the product and is required to pay to us a
royalty on net sales. Beginning in 2000, we expect that royalties from sales of
Tamiflu will comprise a greater portion of our net royalty revenue. We will
recognize royalty revenue from sales of Tamiflu in the quarter following that in
which the related product sales occur.

Contract revenue was $18.7 million, $29.6 million and $29.8 million in 1999,
1998 and 1997, respectively. The single most significant source of contract
revenue in each of these three years relates to the development of Tamiflu under
our R&D collaboration agreement with Roche. Tamiflu is an orally-administered
compound developed to treat and potentially to prevent viral influenza in
humans. During 1999, 1998 and 1997, we recorded approximately $14.9 million,
$16.4 million and $14.2 million, respectively, of contract revenue under this
agreement with Roche. The 1999 amount includes $2.1 million of R&D
reimbursements and $12.8 million of milestone payments. The $16.4 million
recorded during 1998 represents reimbursed R&D expenses and includes $5.2
million attributable to R&D expenses incurred in the fourth quarter of 1997,
which were subject to Roche's approval as of December 31, 1997. Such expenses
were approved for reimbursement and recognized as revenue in 1998. During 1997,
we recognized as contract revenue R&D reimbursements of $8.2 million and
milestone payments of $6.0 million. We are entitled to additional milestone
payments of up to $21.2 million upon achieving certain developmental and
regulatory milestones. While we may earn additional milestones under the Roche
agreement in 2000, R&D reimbursements under the Roche agreement are expected to
be slightly lower in 2000 as compared to 1999. Such reimbursements will
approximate actual related R&D costs we incur.

In November 1999, we entered into an agreement with Somalogic, Inc.
("Somalogic") under which we assigned to Somalogic a sole and exclusive license
to certain intellectual property, including patents and patent applications.
Under the terms of the agreement, Somalogic is required to pay to us a total of
$2.5 million in two nonrefundable installments. The first installment of $1.5
million was paid in November 1999 and is included in contract revenue in our
consolidated statement of operations for the year ended December 31, 1999. The
remaining $1.0 million installment is due in November 2000 and, because
Somalogic is a developmental stage entity that may require third party
financing, we will recognize this amount as contract revenue when received.
Contract revenue recognized in 1999 also includes a $1.0 million
performance-based milestone payment received from SKW Americas, Inc. ("SKW").
SKW is the 51% owner of Proligo L.L.C. ("Proligo"), an entity in which we hold
the remaining 49% ownership interest.

In 1998, we recorded as contract revenue a $3.0 million milestone payment
from Sumitomo Pharmaceuticals Co., Ltd., related to a license of AmBisome rights
in Japan. Also in 1998, we entered into an agreement with Isis Pharmaceuticals,
Inc. ("Isis") under which we sold to Isis the holdings of its antisense patent
estate, including patents and patent applications. Under the terms of the
agreement, Isis is required to pay to us a total of $6.0 million in four
installments. The total sale price of $6.0 million is included in contract
revenue in 1998.

Contract revenue for both 1998 and 1997 also includes reimbursement of
research expenses under our collaborative agreements with Glaxo Wellcome Inc.
("Glaxo") and Schering A.G. ("Schering"). Under our agreement with Schering
related to the discovery and development of aptamers as in vivo diagnostic
agents ("Schering Research Agreement"), we recognized $2.4 million of contract
revenue in

39
both 1998 and 1997. The Schering Research Agreement expired in 1999, but a
related license agreement remains in effect. Our collaborative agreement with
Glaxo was related to its code blocker program. Contract revenue recognized in
connection with the Glaxo agreement was $1.8 million in 1998 and $3.0 million in
1997. In June 1998, the agreement and the funding for the program were
terminated, resulting in reduced revenue in 1998 as compared to 1997.

During 1997, we recognized in contract revenue a $10.0 million milestone
payment under our collaborative agreement with Pharmacia & Upjohn following the
marketing authorisation for VISTIDE in the European Union. This is the only
milestone payment provided for under that agreement.

COSTS AND EXPENSES

Cost of goods sold was $29.5 million, $23.4 million and $21.6 million for
the years ended December 31, 1999, 1998 and 1997, respectively, and resulted
from sales of AmBisome, VISTIDE, and DaunoXome. Overall, cost of goods sold has
been in the range of 20% to 21% of net product sales in each of the three years
presented. In connection with most of our European product sales, we price our
products in the currency of the country into which they are sold ("Payment
Currencies"). A significant majority of our manufacturing costs are in U.S.
Dollars. It is likely that any decline in the value of the Payment Currencies
relative to the U.S. Dollar would negatively impact our gross margins since our
manufacturing costs would remain approximately the same while our revenues,
which are reported in U.S. Dollars, would decline. Except for the potential
impact of unpredictable and uncontrollable changes in Payment Currencies
relative to the U.S. Dollar, we expect the relationship between cost of goods
sold and net product sales to be consistent for the foreseeable future, provided
there are no significant changes in the nature or mix of product sales.

Our R&D expenses for the years ended December 31, 1999, 1998 and 1997 were
$112.9 million, $127.8 million and $112.2 million, respectively. The 12%
decrease in 1999 as compared to 1998 is primarily attributable to our reduced
research activities at our Boulder, Colorado facility. In August 1998, we
transferred our Boulder-based NeXstar Technology Products division to Proligo,
our equity investee. In addition, in October 1998, we reduced our R&D workforce
in Boulder by 47 employees and recorded an expense of $1.6 million related to
severance packages for the discharged employees. In 1999, we reduced our R&D
workforce in Boulder by 30 employees upon completing our merger with NeXstar.
Finally, we had a reduced level of involvement in the development of Tamiflu in
1999 as compared to 1998. These decreases were offset in part by greater levels
of expense in 1999 for the development programs for adefovir dipivoxil for
hepatitis B infection and tenofovir disoproxil fumarate (PMPA oral prodrug) for
HIV, as well as an adjustment of $2.9 million to fully reserve our supply of
adefovir dipivoxil for HIV. This adjustment was made as a result of our decision
to discontinue the development of this product candidate in the United States
after a negative recommendation from an FDA advisory panel and discussions with
the FDA following this recommendation. The $15.6 million increase in R&D
expenses between 1997 and 1998 was primarily attributable to costs associated
with Phase III clinical trials for adefovir dipivoxil for HIV, as well as the
expanded access program for patients with HIV infection. Increased R&D expenses
in 1998 as compared to 1997 also reflect costs associated with the development
of adefovir dipivoxil for hepatitis B infection. We expect our R&D expenses to
increase in 2000 relative to 1999, primarily reflecting increased expenses
related to the continued late-stage development of tenofovir disoproxil fumarate
for HIV and adefovir dipivoxil for hepatitis B.

40
Selling, general and administrative ("SG&A") expenses were $78.3 million,
$78.2 million and $70.6 million for the years ended December 31, 1999, 1998 and
1997. During 1999, we recorded $2.3 million of compensation expense related to a
NeXstar stock option plan that requires the use of variable plan accounting.
This charge was substantially offset by cost savings related to the elimination
of duplicate selling, general and administrative positions and functions within
the combined Gilead and NeXstar organization. The $7.6 million increase in SG&A
expenses in 1998 as compared to 1997 primarily represents costs incurred to:
strengthen the sales and marketing organization in Europe to support increased
levels of AmBisome sales; expand sales, marketing and operational capacity in
anticipation of the then-planned commercial launch of adefovir dipivoxil for
HIV; accrue an executive termination agreement and severance packages for a
NeXstar workforce reduction; and, to support a greater level of R&D activities.
We expect our SG&A expenses to increase during 2000 to support both ongoing
marketing and sales activities and the planned increase in research and
development activities.

Expenses attributable to our merger with NeXstar were $18.3 million for the
year ended December 31, 1999. These expenses primarily consist of transaction
costs, including professional fees, filing fees and printing costs, employee
severance costs and the write-down of certain NeXstar property and equipment
that are not expected to be used in future operations. Total employee severance
costs incurred of $5.3 million relate to the termination of 70 employees, the
majority of which were from our Boulder, Colorado facility. As of December 31,
1999, all employees for which severance costs were accrued had been terminated.
The balance of this accrued liability was $2.5 million at December 31, 1999 and
we anticipate that substantially all remaining accrued severance costs will be
paid to former employees by September 2000. We do not expect to achieve any
significant ongoing future cost savings as a result of these staff reductions,
which were primarily undertaken to functionally realign our organization during
the merger integration process. As we continue to grow, increased spending in
other areas will offset the effect of these cost savings. We do not expect to
recognize any expenses related to the NeXstar merger in future periods.

LITIGATION SETTLEMENT AND RELATED EXPENSES

We reported litigation settlement and related expenses of $0.8 million, $1.3
million and $16.0 million in 1999, 1998 and 1997, respectively. The amount for
1997 was primarily related to the August 1997 settlement with The Liposome
Company ("TLC") in which both parties agreed to dismiss all legal proceedings in
connection with two United States patents and their international counterparts
held by TLC (the "Patent Litigation"). Under the terms of the settlement
agreement, we made an initial payment to TLC of $1.8 million and are required to
make additional payments beginning in 1998 based on AmBisome sales over the next
several years. Because the payments are subject to certain minimum and maximum
amounts, $10.0 million of the accounting charge recorded in 1997 represents the
net present value of all future minimum payments we are required to make. We do
not expect the difference between the future minimum and maximum payments to TLC
to be material. During 1997, we recorded additional expenses related to the
Patent Litigation of $4.2 million.

GAIN ON SALE OF SUBSIDIARY

In 1998, we recorded a $22.1 million gain on the sale of our 51% interest
(the "Interest") in our newly established subsidiary, Proligo, a Delaware
limited liability company, to SKW. Proligo was formed in July 1998 and initially
consisted of the assets of our NeXstar Technology Products division, a
manufacturer of oligonucleotides and specialty chemicals for the pharmaceuticals
industry. As payment for the interest, we received $15.0 million and a 49%
interest in PerSeptive Biosystems GmbH, a company in Hamburg, Germany (the
"Hamburg Company"), which specializes in the manufacture of nucleoside
phosphoramidite monomers. In addition, SKW agreed to pay to us $3.0 million in
guaranteed payments and up to $20.5 million in performance-based milestones
through 2003. As part of the transaction, we contributed $4.9 million and our
49% interest in the Hamburg Company to

41
Proligo. The 49% interest in the Hamburg Company had a fair value of
approximately $5.5 million. SKW contributed $5.1 million and the remaining 51%
of the Hamburg Company to Proligo.

INTEREST INCOME AND INTEREST EXPENSE

We had interest income of $16.4 million, $21.8 million and $20.7 million in
1999, 1998 and 1997, respectively. The decrease in interest income in 1999 as
compared to 1998 is due to both a declining balance of invested cash as well as
slightly lower investment returns in 1999. While the balance of invested cash
also decreased from 1997 to 1998, this decrease was offset by greater investment
returns in 1998. We expect interest income to continue to decline substantially
in 2000, primarily due to decreasing balances of invested cash.

We incurred interest expense of $6.5 million, $7.2 million and $5.1 million
in 1999, 1998 and 1997, respectively. The decrease in interest expense in 1999
as compared to 1998 is primarily due to the repayment of debt obligations.
Interest expense is greater in 1998 than in 1997 primarily due to the fact that
we incurred a full-year's interest expense on our convertible subordinated
debentures in 1998. The debentures were issued in mid-1997. We expect interest
expense to further decline in 2000 as we continue to repay our debt obligations.

EQUITY IN LOSS OF UNCONSOLIDATED AFFILIATE

During 1999, we recorded $4.7 million as our equity in the loss of Proligo,
representing our 49% share of Proligo's net loss for Proligo's fiscal year ended
November 30, 1999. In 1998, we recorded $1.1 million as our equity in the loss
of Proligo for the period from August 15, 1998 (Proligo's inception date)
through November 30, 1998. The Proligo operating loss for December 1999 is
approximately $0.9 million of which we will recognize our 49% share
(approximately $0.4 million) in 2000. We expect to continue to recognize losses
on our equity investment in Proligo during 2000.

Our investment in Proligo is reported in other noncurrent assets on our
consolidated balance sheet. The carrying amount of this investment is $7.6
million at December 31, 1999. In October 1999 and January 2000, we funded
Proligo with a total of $4.9 million to maintain our percentage ownership
interest in Proligo. We presently have no further commitments to provide
additional funding to Proligo.

LIQUIDITY AND CAPITAL RESOURCES

Cash, cash equivalents and marketable securities totaled $294.4 million at
December 31, 1999, compared to $348.7 million at December 31, 1998. This
decrease of $54.3 million is primarily due to the use of cash both to fund
operating activities and to purchase capital items, offset by proceeds from
issuances of stock under employee stock plans.

Significant changes in working capital during 1999 include a $4.4 million
increase in the balance of inventories. During 1999, we began to build our
inventory of adefovir dipivoxil in anticipation of the planned launch of
adefovir dipivoxil for HIV at the end of the year. We discontinued the
development of adefovir dipivoxil for HIV in the United States after a negative
recommendation from an FDA advisory panel and discussions with the FDA following
the recommendation. While we are not carrying a finished goods component of
these inventories, $2.2 million of the $3.8 million increase in raw materials is
due to an increased supply of adefovir dipivoxil. This drug substance does not
have a limited shelf life and we intend to use it in our development of adefovir
dipivoxil for hepatitis B. Our inventories of AmBisome have also increased,
consistent with increasing sales. Prepaid expenses and other current assets also
increased by $2.5 million. This increase is primarily due to the addition of a
$1.0 million receivable from Somalogic. Other noncurrent assets decreased from
$19.9 million at December 31, 1998 to $13.4 million at December 31, 1999. In
part, this $6.5 million decrease consists of a $2.7 million reduction in the
carrying value of our investment in Proligo, a $1.8 million receipt of our
receivable from SKW and a $1.0 million repayment of our receivable from Isis.
Accrued clinical

42
and preclinical expenses decreased from $12.8 million at December 31, 1998 to
$5.5 million at December 31, 1999. This decrease is largely due to timing issues
related to the completion of certain clinical trials and the commencement or
advancement of others. At December 31, 1998, other accrued liabilities includes
a $5.0 million accrued liability to Roche, which represents Roche's 1998 R&D
funding in excess of our related R&D spending. During 1999, we achieved three
milestones under our R&D agreement with Roche and recognized $12.8 million of
contract revenue as a result. Roche funded a portion of these milestone
payments, as well as the $0.7 million of R&D reimbursement revenue for the first
quarter of 1999, by permitting us to offset our liability to Roche. Accordingly,
the $5.0 million reported as an accrued liability at December 31, 1998 is
reported as contract revenue during 1999.

Our accounts receivable balance at December 31, 1999 was $45.6 million as
compared to $43.1 million at December 31, 1998. The growth in receivables was
primarily due to increased sales of AmBisome and proportionately increased sales
of our products in countries in which payments tend to be relatively slow. In
certain cases, these slow payment practices reflect the pace at which
governmental entities reimburse our customers. Sales to customers in countries
that tend to be relatively slow paying have in the past increased, and in the
future may further increase, the average length of time that accounts receivable
are outstanding. This, in turn, may increase the financial risk of certain of
our customers. In certain countries in which payments have been slow,
particularly Greece, Spain and Italy, our accounts receivable are significant.
At December 31, 1999, our past due accounts receivable for Greece, Spain and
Italy totaled approximately $15.8 million, of which approximately $5.0 million
was more than 120 days past due. To date, we have experienced only modest losses
with respect to the collection of our accounts receivable and believe that the
past due accounts receivable for Greece, Spain and Italy are collectible. We
continually seek to improve our collection process to ensure that we collect as
much as possible from our product sales and that such collections are timely.

We maintain a $10.0 million unsecured line of credit (the "Credit
Agreement") that bears interest at a floating rate with a major financial
institution. Under the terms of the Credit Agreement, we are required to
maintain certain financial ratios and there are limitations on our ability to
incur additional debt or to engage in certain significant transactions. The
Credit Agreement, which includes a foreign exchange facility, expires on
April 16, 2001. As of December 31, 1999, we had no outstanding borrowings under
the Credit Agreement.

We believe that our existing capital resources, supplemented by net product
revenues and contract and royalty revenues, will be adequate to satisfy our
capital needs for the foreseeable future. As of December 31, 1999, we were
entitled to additional cash payments of up to $21.2 million from Roche upon
achieving specific additional developmental and regulatory milestones, although
there can be no assurance that any of the milestones will be met. Our future
capital requirements will depend on many factors, including our continuing
integration with NeXstar, the progress of our research and development efforts,
the scope and results of preclinical studies and clinical trials, the cost,
timing and outcomes of regulatory reviews, the rate of technological advances,
determinations as to the commercial potential of our products under development,
the commercial performance of AmBisome and any of our products in development
that receive marketing approval, administrative expenses, the status of
competitive products, the establishment of manufacturing capacity or third-party
manufacturing arrangements, the expansion of sales and marketing capabilities,
possible geographic expansion and the establishment of additional collaborative
relationships with other companies.

We may in the future require additional funding, which could be in the form
of proceeds from equity or debt financings or additional collaborative
agreements with corporate partners. If such funding is required, there can be no
assurance that it will be available on favorable terms, if at all.

43
NEW ACCOUNTING PRONOUNCEMENTS

In June 1998, the Financial Accounting Standards Board ("FASB") issued SFAS
No. 133, ACCOUNTING FOR DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES, which
establishes accounting and reporting standards for derivative instruments,
including forward foreign exchange contracts, and hedging activities. In June
1999, the FASB issued SFAS No. 137, ACCOUNTING FOR DERIVATIVE INSTRUMENTS AND
HEDGING ACTIVITIES--DEFERRAL OF THE EFFECTIVE DATE OF FASB STATEMENT NO. 133.
SFAS No. 133 is now effective for fiscal years beginning after June 15, 2000
and, therefore, we will adopt this accounting standard effective January 1,
2001. We have not yet determined the impact of SFAS No. 133 on our financial
position or results of operations.

We have recognized nonrefundable technology access fees received in
connection with collaboration agreements as revenue when received, when the
technology has been transferred and when all contractual obligations relating to
the fees are fulfilled. In December 1999, the Securities and Exchange Commission
("SEC") issued Staff Accounting Bulletin ("SAB") No. 101, "REVENUE RECOGNITION
IN FINANCIAL STATEMENTS." Among other things, SAB No. 101 describes the SEC
Staff's position on the recognition of certain nonrefundable upfront fees
received in connection with research collaborations. We are evaluating the
applicability of SAB No. 101 to our existing collaborative agreements. Should we
conclude that the approach described in SAB No. 101 is more appropriate, we will
change our method of accounting effective January 1, 2000 to recognize such fees
over the term of the related agreement. Any required adjustment would be
recognized as a cumulative effect of a change in accounting principle.

IMPACT OF YEAR 2000

In prior years, we implemented a Year 2000 project to address the issue of
computer software and hardware correctly processing dates through and beyond the
Year 2000. The goal of this project was to ensure that all computer software and
hardware that we use or rely upon is retired, replaced or made Year 2000
compliant before December 31, 1999. To date, we have not experienced any Year
2000-related operational issues and are not aware of any material potential
problems that may arise as a result of Year 2000 issues either from our own
internal systems or from the products and services of third parties upon which
we rely.

The total cost of our Year 2000 compliance efforts was not material to our
financial condition or results of operations. External costs of such compliance
efforts were approximately $2.1 million. Of this amount, $1.4 million was
charged to expense and the remainder has been capitalized. Any remaining
expenses related to remediation efforts will be charged to expense as incurred.
We will continue to monitor our business-critical computer applications and
those of our suppliers and vendors throughout the year 2000 to ensure that any
latent Year 2000 problems that may arise are promptly addressed.

MARKET RISK DISCLOSURES

FOREIGN CURRENCY EXCHANGE RISK

Our operations include manufacturing and sales activities in the United
States as well as sales activities in Europe and Australia. As a result, our
financial results could be significantly affected by factors such as changes in
foreign currency exchange rates or weak economic conditions in the foreign
markets in which we distribute our products. Our operating results are exposed
to changes in exchange rates between the U.S. Dollar and various foreign
currencies, the most significant of which are the Euro, the British Pound and
the Australian Dollar. When the U.S. Dollar strengthens against these
currencies, the relative value of sales made in the respective foreign currency
decreases. Conversely, when the U.S. Dollar weakens, the relative amounts of
such sales increase. Overall, we are a net receiver of foreign currencies and,
therefore, benefit from a weaker U.S. Dollar and are adversely

44
affected by a stronger U.S. Dollar relative to those foreign currencies in which
we transact significant amounts of business.

To mitigate the impact of changes in currency exchange rates on our foreign
currency sales transactions, we enter into foreign exchange forward contracts to
hedge our foreign currency accounts receivables. These hedging activities cannot
eliminate foreign-exchange risk.

The following table summarizes the notional amounts, average currency
exchange rates and fair values of our open foreign exchange forward contracts at
December 31, 1999. None of the contracts have maturities that exceed one year.
Average rates are stated in terms of the amount of foreign currency per U.S.
Dollar. Fair values represent estimated settlement amounts at December 31, 1999
(contract amounts and fair values in thousands):

<TABLE>
<CAPTION>
FAIR VALUE
CURRENCY CONTRACT AMOUNT AVERAGE RATE DECEMBER 31, 1999
- -------- --------------- ------------ ------------------
<S> <C> <C> <C>
Australian Dollar................................. $ 2,147 1.5547 $ (54)
British Pound..................................... 7,657 0.6238 (54)
Danish Krone...................................... 34 7.3527 --
Euro.............................................. 31,448 0.9755 20
Norwegian Krone................................... 105 8.0322 --
Swedish Krona..................................... 587 8.5494 (2)
Swiss Franc....................................... 261 1.5840 1
</TABLE>

INTEREST RATE RISK

Our portfolio of available-for-sale investment securities and our fixed-rate
liabilities create an exposure to interest rate risk. With respect to the
investment portfolio, we adhere to an investment policy that requires us to
limit amounts invested in securities based on maturity, industry group,
investment type and issuer, except for securities issued by the U.S. government.
The goals of our investment policy, in order of priority, are as follows:

1. Safety and preservation of principal and diversification of risk;

2. Liquidity of investments sufficient to meet cash flow requirements; and

3. Competitive after-tax rate of return.

The following table summarizes the expected maturities and average interest
rates of our interest-bearing assets and fixed-rate liabilities at December 31,
1999 (dollars in thousands):

<TABLE>
<CAPTION>
YEARS ENDING DECEMBER 31, FAIR VALUE
---------------------------------------------------- DECEMBER 31,
2000 2001 2002 2003 2004 THEREAFTER TOTAL 1999
-------- -------- -------- -------- -------- ---------- -------- -------------
<S> <C> <C> <C> <C> <C> <C> <C> <C>
ASSETS
Available-for-sale
Securities......... $177,018 $65,346 $18,500 $ -- $ -- $ -- $260,864 $258,341
Average interest
rate............... 6.08% 5.73% 6.32%

LIABILITIES
Minimum litigation
settlement,
including current
portion............ 1,083 1,178 1,281 1,394 1,516 2,084 8,536 8,536
Discount rate........ 8.50% 8.50% 8.50% 8.50% 8.50% 8.50%
Long-term debt,
including current
portion............ 1,003 807 652 301 -- -- 2,763 2,763
Average interest
rate............... 11.54% 11.71% 11.64% 11.50%
Convertible
subordinated
debentures......... -- -- -- -- 79,533 -- 79,533 101,802
Interest rate........ 6.25% 6.25% 6.25% 6.25% 6.25%
</TABLE>

45
ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA

The financial statements required by this item are set forth beginning at
page 53 of this report.

ITEM 9. CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING AND
FINANCIAL DISCLOSURE

Not applicable.

PART III

ITEM 10. DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT

The information required by this Item concerning our directors and executive
officers is incorporated by reference to pages 3 through 6 of our Definitive
Proxy Statement filed with the SEC pursuant to Regulation 14A in connection with
the 2000 Annual Meeting (the "Proxy Statement") under the headings "Nominees"
and "Executive Officers."

COMPLIANCE WITH SECTION 16(A) OF THE EXCHANGE ACT

The information required by this Item is incorporated by reference to page
14 of the Proxy Statement under the heading "Compliance with Section 16(a) of
the Securities Exchange Act of 1934."

ITEM 11. EXECUTIVE COMPENSATION

The information required by this Item is incorporated by reference to pages
15 through 21 of the Proxy Statement under the headings "Executive Compensation"
and "Compensation Committee Report."

ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

The information required by this Item is incorporated by reference to pages
13 through 14 of the Proxy Statement under the heading "Security Ownership of
Certain Beneficial Owners and Management."

ITEM 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

The information required by this Item is incorporated by reference to
page 22 of the Proxy Statement under the heading "Certain Transactions" and by
reference to pages 15 through 21 of the Proxy Statement under the heading
"Executive Compensation."

46
PART IV

ITEM 14. EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K

(a) The following documents are filed as part of this Form 10-K:

(1) Schedule II is included on page 85 of this report. All other schedules
are omitted because they are not required or the required information is
included in the financial statements or notes thereto.

(2) Exhibits

<TABLE>
<CAPTION>
EXHIBIT EXHIBIT
FOOTNOTE NUMBER DESCRIPTION OF DOCUMENT
- --------------------- -------- -----------------------
<C> <S> <C>
(1) 3.1 Certificate of Amendment to Restated Certificate of
Incorporation of the Registrant.
(2) 3.2 Amended and Restated Certificate of Incorporation of the
Registrant
(3) 3.3 Bylaws of the Registrant, as amended and restated March 30,
1999
4.1 Reference is made to Exhibits 3.1, 3.2, and 3.3.
(4) 4.2 Rights Agreement, dated as of November 21, 1994, between
Registrant and First Interstate Bank, with exhibits.
(4) 4.3 Form of letter sent to Gilead Sciences, Inc. stockholders,
dated December 14, 1994.
(1) 4.4 First Supplemental Indenture dated July 29, 1999 among IBJ
Whitehall Bank & Trust Company, NeXstar Pharmaceuticals,
Inc. and the Registrant to the Indenture dated July 31, 1997
between IBJ Whitehall Bank & Trust Company and NeXstar
Pharmaceuticals, Inc.
(5) 4.5 Indenture dated July 31, 1997 between IBJ Whitehall Bank &
Trust Company and NeXstar Pharmaceuticals, Inc. for 6 1/4%
Convertible Subordinated Debentures.
(6) 4.6 Amended and Restated Rights Agreement dated as of
October 21, 1999 between Gilead Sciences, Inc. and
ChaseMellon Shareholder Services, LLC.
(3) 10.1 Form of Indemnity Agreement entered into between the
Registrant and its directors and executive officers.
(7) 10.3 Form of Employee Proprietary Information and Invention
Agreement entered into between Registrant and certain of its
officers and key employees.
(2) 10.4 Registrant's 1987 Incentive Stock Option Plan and related
agreements.
(2) 10.5 Registrant's 1987 Supplemental Stock Option Plan and related
agreements.
10.7 Registrant's Employee Stock Purchase Plan, as amended
March 30, 1999.
10.8 Registrant's 1991 Stock Option Plan, as amended March 30,
1999.
(2) 10.15 Form of Non-Qualified Stock Option issued to certain
executive officers and directors in 1991.
(2) 10.16 Relocation Loan Agreement, dated as of November 1, 1990
among Registrant, John C. Martin and Rosemary Martin.
(2) 10.17 Vintage Park Research and Development Net Lease by and
between Registrant and Vintage Park Associates dated
March 27, 1992 for premises located at 344B, 346 and 353
Lakeside Drive, Foster City, California with related
addendum, exhibits and amendments.
(2) 10.21 Letter Agreement, dated as of September 23, 1991 between
Registrant and IOCB/ REGA, with exhibits with certain
confidential information deleted.
(8) 10.23 Vintage Park Research and Development Net Lease by and
between Registrant and Vintage Park Associates dated
September 16, 1993 for premises located at 335 Lakeside
Drive, Foster City, California with related exhibits.
</TABLE>

47
<TABLE>
<CAPTION>
EXHIBIT EXHIBIT
FOOTNOTE NUMBER DESCRIPTION OF DOCUMENT
- --------------------- -------- -----------------------
<C> <S> <C>
(9) 10.26 Amendment Agreement, dated October 25, 1993 between
Registrant and IOCB/ REGA, and related license agreements
and exhibits with certain confidential information deleted.
(10) 10.29 License and Supply agreement between Registrant and American
Cyanamid Company dated August 1, 1994 with certain
confidential information deleted.
(4) 10.30 Loan Agreement, dated as of October 1, 1994 among Registrant
and Mark L. Perry and Melanie P. Pena.
(30) 10.33 Registrant's 1995 Non-Employee Directors' Stock Option Plan,
as amended January 26, 1999, and related form of stock
option grant.
(11) 10.34 Collaborative Research Agreement, dated as of March 25,
1996, by and between Registrant and Glaxo Wellcome Inc. with
certain confidential information deleted.
(12) 10.36 Vintage Park Research and Development Lease by and between
Registrant and WCB Sixteen Limited Partnership dated
June 24, 1996 for premises located at 333 Lakeside Drive,
Foster City, California.
(12) 10.37 Amendment No. 1 to Vintage Park Research and Development
Lease by and between Registrant and WCB Seventeen Limited
Partnership dated June 24, 1996 for premises located at 335
Lakeside Drive, Foster City, California.
(12) 10.38 Amendment No. 2 to Vintage Park Research and Development
Lease by and between Registrant and WCB Seventeen Limited
Partnership dated June 24, 1996 for premises located at
344B, 346 and 353 Lakeside Drive, Foster City, California.
(13) 10.40 License and Supply Agreement between Registrant and
Pharmacia & Upjohn S.A. dated August 7, 1996 with certain
confidential information deleted.
(13) 10.41 Series B Preferred Stock Purchase Agreement between
Registrant and Pharmacia & Upjohn S.A. dated August 7, 1996.
(13) 10.42 Development and License Agreement between Registrant and F.
Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc dated
September 27, 1996 with certain confidential information
deleted.
(14) 10.45 Amended and Restated Co-promotion Agreement between
Registrant and Roche Laboratories, Inc. dated September 12,
1997 with certain confidential information deleted.
(15) 10.46 Amendment No. 1 to Collaborative Research Agreement, dated
as of December 22, 1997, between Registrant and Glaxo
Wellcome Inc.
(31) 10.47 Patent Rights Purchase Agreement between Registrant and Isis
Pharmaceuticals, Inc. dated December 18, 1998 with certain
confidential information deleted.
(31) 10.48 Amendment No. 3 to Vintage Park Research and Development
Lease by and between Registrant and Spieker Properties, L.P.
dated August 14, 1998 for premises located at 355 Lakeside
Drive, Foster City, California.
(16) 10.49 Agreement and Plan of Merger dated February 28, 1999 by and
among Registrant, Gazelle Acquisition Sub, Inc. and NeXstar
Pharmaceuticals, Inc.
(17) 10.52 License Agreement between University Research Corporation
and NeXstar Pharmaceuticals, Inc., effective as of July 17,
1991, as amended on October 26, 1992.
(18) 10.53 Amendment No. 2, effective April 5, 1996, and Amendment No.
3, dated September 5, 1996, to the License Agreement between
University Research Corporation and NeXstar Pharmaceuticals,
Inc., effective as of July 17, 1991, as amended on
October 26, 1992.
(17) 10.55 Collaborative Research Agreement between NeXstar
Pharmaceuticals, Inc. and Schering A.G., dated as of
November 16, 1993.
</TABLE>

48
<TABLE>
<CAPTION>
EXHIBIT EXHIBIT
FOOTNOTE NUMBER DESCRIPTION OF DOCUMENT
- --------------------- -------- -----------------------
<C> <S> <C>
(18) 10.56 Letter Agreement between NeXstar Pharmaceuticals, Inc. and
Schering A.G., effective February 1, 1997, amending the
Collaborative Research Agreement between NeXstar
Pharmaceuticals, Inc. and Schering A.G., dated as of
November 16, 1993.
(17) 10.57 License Agreement between NeXstar Pharmaceuticals, Inc. and
Schering A.G., dated as of November 16, 1993.
(5) 10.60 Master Lease Agreement, dated as of September 9, 1996,
between General Electric Capital Corporation and NeXstar
Pharmaceuticals, Inc.
(5) 10.61 Master Security Agreement, dated as of March 27, 1997,
between General Electric Capital Corporation and NeXstar
Pharmaceuticals, Inc.
(5) 10.62 NeXagen, Inc. 1993 Incentive Stock Plan, adopted
February 8, 1993, as amended.
(20) 10.63 NeXstar Pharmaceuticals, Inc.'s 1995 Director Option Plan,
adopted July 25, 1995.
(21) 10.64 Vestar, Inc. 1988 Stock Option Plan.
(21) 10.65 Lease, dated March 26, 1987, between Vestar, Inc. and
Majestic Realty Co. and Patrician Associates, Inc. and
Amendment No. 1 thereto and Amendment No. 2 thereto, dated
as of June 8, 1992.
(19) 10.66 Third Amendment, dated January 11, 1996, between Majestic
Realty Co. and Patrician Associates, Inc. and the
Registrant, to Lease, dated March 26, 1987, between Vestar,
Inc. and Majestic Realty Co. and Patrician Associates, Inc.
(22) 10.67 Assignment and Royalty Agreement, dated December 21, 1990,
effective as of June 2, 1989, between Vestar, Inc. and City
of Hope National Medical Center.
(19) 10.68 License Agreement, effective as of August 12, 1986, between
Vestar, Inc. and The Regents of the University of
California.
(21) 10.69 Agreement by and between Fujisawa USA, Inc. and Vestar,
Inc., dated August 9, 1991, and Amendment No. 1 thereto,
dated as of May 17, 1994.
(20) 10.70 Amendment No. 2 to agreement between Fujisawa USA, Inc. and
Vestar, Inc., dated as of April 3, 1995, between Fujisawa
USA, Inc. and Vestar, Inc. with certain confidential
information deleted.
(19) 10.71 Amendment No. 3 to Agreement between Fujisawa USA, Inc. and
the Registrant, dated March 4, 1996, to the Agreement by and
between Fujisawa USA, Inc. and Vestar, Inc., dated
August 9, 1991.
(21) 10.72 Lease, dated April 13, 1992, between Vestar, Inc. and
Majestic Realty Co. and Patrician Associates, Inc.
(19) 10.73 First Amendment to Lease, dated April 10, 1993, between
Majestic Realty Co. and Patrician Associates, Inc. and
Vestar, Inc. amending Lease, dated April 13, 1992, between
Majestic Realty Co. and Patrician Associates, Inc. and
Vestar, Inc.
(21) 10.74 Master Lease Agreement, dated June 29, 1994, between Vestar,
Inc. and Comdisco, Inc.
(23) 10.75 Amendment No. 1, dated December 5, 1997, between NeXstar
Pharmaceuticals, Inc. and Comdisco, Inc. to the Master Lease
Agreement, dated June 29, 1994, between Vestar, Inc. and
Comdisco, Inc.
(19) 10.76 Royalty Agreement, dated October 30, 1995, between NeXstar
Pharmaceuticals, Inc. and Amplimed Corporation.
(24) 10.77 Pharmaceutical Pricing Agreement between the Secretary of
Veterans Affairs and NeXstar Pharmaceuticals, Inc., dated
April 30, 1996.
(24) 10.78 Master Agreement between Secretary of Veterans Affairs and
NeXstar Pharmaceuticals, Inc., dated April 30, 1996.
(24) 10.79 Pharmaceutical Pricing Agreement between the Secretary of
Health and Human Services and NeXstar Pharmaceuticals, Inc.,
dated April 30, 1996.
</TABLE>

49
<TABLE>
<CAPTION>
EXHIBIT EXHIBIT
FOOTNOTE NUMBER DESCRIPTION OF DOCUMENT
- --------------------- -------- -----------------------
<C> <S> <C>
(24) 10.80 Rebate Agreement between the Secretary of Health and Human
Services and the Registrant, dated April 30, 1996.
(25) 10.81 Industrial Real Estate Lease, dated July 1, 1996, by and
between Wilderness Place, Ltd. and NeXstar Pharmaceuticals,
Inc.
(26) 10.82 Sublease Agreement, dated July 31, 1996, between Sybase,
Inc. and NeXstar Pharmaceuticals, Inc.
(18) 10.83 License and Distribution Agreement, dated September 26,
1997, by and between Sumitomo Pharmaceuticals Co., Ltd. and
NeXstar Pharmaceuticals, Inc. with certain confidential
information deleted.
(27) 10.84 Settlement Agreement, dated August 11, 1997, by and among
NeXstar Pharmaceuticals, Inc., Fujisawa U.S.A., Inc. and The
Liposome Company, Inc. with certain confidential information
deleted.
(27) 10.85 Credit Agreement, dated September 1, 1997, by and between
NeXstar Pharmaceuticals, Inc. and Wells Fargo Bank, National
Association.
(28) 10.86 First Amendment to Credit Agreement, dated May 1, 1998, by
and between NeXstar Pharmaceuticals, Inc. and Wells Fargo
Bank, National Association amending Credit Agreement, dated
September 1, 1997, by and between NeXstar Pharmaceuticals,
Inc. and Wells Fargo Bank, National Association.
(28) 10.87 Letter agreement, dated September 1, 1998, between NeXstar
Pharmaceuticals, Inc. and Wells Fargo Bank, National
Association amending Credit Agreement, dated September 1,
1997, as amended, by and between NeXstar Pharmaceuticals,
Inc. and Wells Fargo Bank, National Association.
(28) 10.88 Second Amendment to Credit Agreement, dated November 1,
1998, by and between NeXstar Pharmaceuticals, Inc. and Wells
Fargo Bank, National Association amending Credit Agreement,
dated September 1, 1997, as amended, by and between NeXstar
Pharmaceuticals, Inc. and Wells Fargo Bank, National
Association.
(28) 10.89 Amended and Restated Limited Liability Company Agreement of
Proligo L.L.C., dated August 15, 1998, by and among NeXstar
Pharmaceuticals International, Inc., SKW Americas, Inc. and
NeXstar Pharmaceuticals, Inc.
(29) 10.90 Amendment, dated April 30, 1998, between Sumitomo
Pharmaceuticals Co., Ltd. (Sumitomo) and NeXstar
Pharmaceuticals, Inc. to the License and Distribution
Agreement, dated September 26, 1996, between Sumitomo and
NeXstar Pharmaceuticals, Inc.
10.91 Lease agreement between THW Partners Limited Partnership and
Registrant dated January 25, 2000.
21.1 Subsidiaries of the Registrant.
23.1 Consent of Ernst & Young LLP, Independent Auditors.
23.2 Consent of PricewaterhouseCoopers LLP, Independent Auditors.
24.1 Power of Attorney. Reference is made to page 86.
27.1 Financial Data Schedule.
</TABLE>

- ------------------------

(1) Filed as an exhibit to Registrant's Current Report on Form 8-K filed on
August 6, 1999 and incorporated herein by reference.

(2) Filed as an exhibit to Registrant's Registration Statement on Form S-8 (No.
33-46058) and incorporated herein by reference.

(3) Filed as an exhibit to Registrant's Annual Report on Form 10-K/A for the
fiscal year ended December 31, 1998 and incorporated herein by reference.

50
(4) Filed as an exhibit to Registrant's Quarterly Report on Form 10-Q for the
quarter ended December 31, 1994 and incorporated herein by reference.

(5) Filed as an exhibit to NeXstar Pharmaceutical, Inc.'s Quarterly Report on
Form 10-Q for the quarter ended June 30, 1997 and incorporated herein by
reference.

(6) Filed as an exhibit to Registrant's Current Report on Form 8-K filed on
October 22, 1999 and incorporated herein by reference.

(7) Filed as an exhibit to Registrant's Registration Statement on Form S-1 (No.
33-55680) or amendments thereto and incorporated herein by reference.

(8) Filed as an exhibit to Registrant's Quarterly Report on Form 10-Q for the
quarter ended September 30, 1993 and incorporated herein by reference.

(9) Filed as an exhibit to Registrant's Annual Report on Form 10-K for the
fiscal year ended March 31, 1994 and incorporated herein by reference.

(10) Filed as an exhibit to Registrant's Quarterly Report on Form 10-Q for the
quarter ended September 30, 1994 and incorporated herein by reference.

(11) Filed as an exhibit to Registrant's Annual Report on Form 10-K for the nine
month period ended December 31, 1995.

(12) Filed as an exhibit to Registrant's Quarterly Report on Form 10-Q for the
quarter ended June 30, 1996 and incorporated herein by reference.

(13) Filed as an exhibit to Registrant's Quarterly Report on Form 10-Q for the
quarter ended September 30, 1996 and incorporated herein by reference.

(14) Filed as an exhibit to Registrant's Quarterly Report on Form 10-Q for the
quarter ended September 30, 1997 and incorporated herein by reference.

(15) Filed as an exhibit to Registrant's Annual Report on Form 10-K for the year
ended December 31, 1997 and incorporated herein by reference.

(16) Filed as an exhibit to Registrant's Current Report on Form 8-K filed on
March 9, 1999 and incorporated herein by reference.

(17) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Registration
Statement on Form S-1 (File No. 33-72142), declared effective by the
Securities and Exchange Commission on January 28, 1994, and incorporated
herein by reference.

(18) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-K for the
fiscal year ended December 31, 1996, and incorporated herein by reference.

(19) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-K for the
fiscal year ended December 31, 1995, and incorporated herein by reference.

(20) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-Q for the
quarterly period ended September 30, 1995, and incorporated herein by
reference.

(21) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-K for the
fiscal year ended December 31, 1994, and incorporated herein by reference.

(22) Filed on March 22, 1991 as an exhibit to NeXstar Pharmaceuticals, Inc.'s
Registration Statement on Form S-2 (File No. 33-39549), and incorporated
herein by reference.

(23) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-K for the
year ended December 31, 1997, and incorporated herein by reference.

51
(24) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-Q for the
quarterly period ended March 31, 1996, and incorporated herein by reference.

(25) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-Q for the
quarterly period ended June 30, 1996, and incorporated herein by reference.

(26) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-Q for the
quarterly period ended September 30, 1996, and incorporated herein by
reference.

(27) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-Q for the
quarterly period ended September 30, 1997, and incorporated herein by
reference.

(28) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-Q for the
quarter ended September 30, 1998, and incorporated herein by reference.

(29) Filed as an exhibit to NeXstar Pharmaceuticals, Inc.'s Form 10-Q for the
quarter ended June 30, 1998 and incorporated herein by reference.

(30) Filed as an Exhibit to Registrant's Form 10-K/A for the year ended
December 31, 1998, and incorporated herein by reference.

(31) Filed as an Exhibit to Registrant's Form 10-K for the year ended
December 31, 1998, and incorporated herein by reference.

(B) REPORTS ON FORM 8-K

On March 9, 1999, the Registrant filed a Current Report on Form 8-K
regarding the proposed merger with NeXstar Pharmaceuticals, Inc. On August 6,
1999, the Registrant filed a Current Report on Form 8-K regarding its merger
with NeXstar. On August 8, 1999, the Registrant filed a Current Report on
Form 8-K relating to the Supplemental Indenture for its 6 1/4% Convertible
Subordinated Debentures. On September 15, 1999 the Registrant filed an
additional Current Report on Form 8-K regarding its merger with NeXstar, which
included audited supplemental consolidated balance sheets of Gilead as of
December 31, 1998 and 1997 and the related supplemental consolidated statements
of operations, stockholders' equity and cash flows for each of the three years
in the period ended December 31, 1998 together with the related supplemental
financial statement schedule of Gilead, representing Gilead's and NeXstar's
combined operations for these periods. On October 22, 1999, the Registrant filed
a Current Report on From 8-K relating to its Amended and Restated Rights
Agreement.

52
GILEAD SCIENCES, INC.

CONSOLIDATED FINANCIAL STATEMENTS

YEARS ENDED DECEMBER 31, 1999, 1998 AND 1997,

CONTENTS

<TABLE>
<S> <C>
Reports of Independent Auditors............................. 54

Audited Consolidated Financial Statements

Consolidated Balance Sheets................................. 56
Consolidated Statements of Operations....................... 57
Consolidated Statement of Stockholders' Equity.............. 58
Consolidated Statements of Cash Flows....................... 59
Notes to Consolidated Financial Statements.................. 60
</TABLE>

53
REPORT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS

The Board of Directors and Stockholders
Gilead Sciences, Inc.

We have audited the accompanying consolidated balance sheets of Gilead
Sciences, Inc. as of December 31, 1999 and 1998, and the related consolidated
statements of operations, stockholders' equity, and cash flows for each of the
three years in the period ended December 31, 1999. Our audits also included the
financial statement schedule listed in the Exhibit Index. These financial
statements and schedule are the responsibility of the management of Gilead
Sciences, Inc. Our responsibility is to express an opinion on these financial
statements and schedule based on our audits. We did not audit the financial
statements of Proligo L.L.C., a limited liability company, the investment in
which is reflected in the accompanying consolidated financial statements using
the equity method of accounting. The investment in Proligo L.L.C. represents
1.7% and 2.1% of consolidated total assets at December 31, 1999 and 1998,
respectively, and the Company's equity in the net loss of Proligo L.L.C. is
$4,656,000 and $1,101,000 in 1999 and 1998, respectively. The 1999 and 1998
financial statements of Proligo L.L.C. have been audited by other auditors whose
report has been furnished to us; insofar as our opinion on the 1999 and 1998
consolidated financial statements relates to data included for Proligo L.L.C.,
it is based solely on their report.

We conducted our audits in accordance with auditing standards generally
accepted in the United States. Those standards require that we plan and perform
the audit to obtain reasonable assurance about whether the financial statements
are free of material misstatement. An audit includes examining, on a test basis,
evidence supporting the amounts and disclosures in the financial statements. An
audit also includes assessing the accounting principles used and significant
estimates made by management, as well as evaluating the overall financial
statement presentation. We believe that our audits provide a reasonable basis
for our opinion.

In our opinion, based on our audits and the report of other auditors, the
consolidated financial statements referred to above present fairly, in all
material respects, the consolidated financial position of Gilead Sciences, Inc.
at December 31, 1999 and 1998, and the consolidated results of its operations
and its cash flows for each of the three years in the period ended December 31,
1999, in conformity with accounting principles generally accepted in the United
States. Also in our opinion, the financial statement schedule referred to above,
when considered in relation to the basic financial statements taken as a whole,
presents fairly, in all material respects, the information set forth therein.

ERNST & YOUNG LLP

Palo Alto, California
January 24, 2000

54
REPORT OF INDEPENDENT AUDITORS

The Board of Directors and
Members of Proligo LLC:

In our opinion, the accompanying consolidated balance sheets and the related
consolidated statements of operations, of members' equity and of cash flows
present fairly, in all material respects, the financial position of Proligo LLC
and its subsidiary at November 30, 1999 and 1998, and the results of their
operations and their cash flows for the year ended November 30, 1999 and the
period from August 15, 1998 through November 30, 1998, in conformity with
generally accepted accounting principles in the United States. These financial
statements are the responsibility of the Company's management; our
responsibility is to express an opinion on these financial statements based on
our audits. We conducted our audits of these financial statements in accordance
with generally accepted auditing standards in the United States which require
that we plan and perform the audit to obtain reasonable assurance about whether
the financial statements are free of material misstatement. An audit includes
examining, on a test basis, evidence supporting the amounts and disclosures in
the financial statements, assessing the accounting principles used and
significant estimates made by management, and evaluating the overall financial
statement presentation. We believe that our audits provide a reasonable basis
for the opinion expressed above.

PricewaterhouseCoopers LLP

Denver, Colorado
January 7, 2000

55
GILEAD SCIENCES, INC.

CONSOLIDATED BALANCE SHEETS

(IN THOUSANDS, EXCEPT SHARE AND PER SHARE AMOUNTS)

<TABLE>
<CAPTION>
DECEMBER 31,
---------------------
1999 1998
--------- ---------
<S> <C> <C>
ASSETS
Current assets:
Cash and cash equivalents................................. $ 47,011 $ 101,136
Marketable securities..................................... 247,383 247,607
Accounts receivable, net of allowance for doubtful
accounts of $2,333 in 1999 and $1,480 in 1998........... 45,599 43,090
Inventories............................................... 20,959 16,550
Prepaid expenses and other................................ 11,029 8,506
--------- ---------
Total current assets........................................ 371,981 416,889
Property, plant and equipment, net.......................... 51,398 51,019
Other noncurrent assets..................................... 13,429 19,856
--------- ---------
$ 436,808 $ 487,764
========= =========
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
Accounts payable.......................................... $ 9,481 $ 7,662
Accrued clinical and preclinical expenses................. 5,467 12,841
Accrued compensation and employee benefits................ 9,901 9,387
Other accrued liabilities................................. 15,004 19,327
Deferred revenue.......................................... 4,833 3,275
Long-term obligations due within one year................. 3,191 4,842
--------- ---------
Total current liabilities................................... 47,877 57,334
Accrued litigation settlement expenses due after one year... 6,853 7,848
Long-term obligations due after one year.................... 5,253 8,883
Convertible subordinated debentures......................... 79,533 80,000
Commitments and contingencies
Stockholders' equity:
Preferred stock, par value $.001 per share, issuable in
series; 5,000,000 shares authorized; 1,133,786 shares of
Series B convertible preferred issued and outstanding at
December 31, 1998 (liquidation preference of $40,000)... -- 1
Common stock, par value $.001 per share; 100,000,000
shares authorized; 44,092,779 shares and 41,562,837
shares issued and outstanding at December 31, 1999 and
1998, respectively...................................... 44 42
Additional paid-in capital................................ 749,081 716,964
Accumulated other comprehensive loss...................... (2,527) (337)
Deferred compensation..................................... (74) (225)
Accumulated deficit....................................... (449,232) (382,746)
--------- ---------
Total stockholders' equity.................................. 297,292 333,699
--------- ---------
$ 436,808 $ 487,764
========= =========
</TABLE>

See accompanying notes

56
GILEAD SCIENCES, INC.

CONSOLIDATED STATEMENTS OF OPERATIONS

(IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
------------------------------
1999 1998 1997
-------- -------- --------
<S> <C> <C> <C>
Revenues:
Product sales, net........................................ $139,890 $114,176 $100,887
Royalty revenue, net...................................... 10,431 7,305 1,560
Contract revenue.......................................... 18,658 29,638 29,811
-------- -------- --------
Total revenues.............................................. 168,979 151,119 132,258
Expenses:
Cost of goods sold........................................ 29,546 23,357 21,646
Research and development.................................. 112,888 127,773 112,177
Selling, general and administrative....................... 78,347 78,234 70,626
Merger related expenses................................... 18,303 -- --
Litigation settlement and related expenses................ 754 1,267 16,031
-------- -------- --------
Total costs and expenses.................................... 239,838 230,631 220,480
-------- -------- --------
Loss from operations........................................ (70,859) (79,512) (88,222)
Gain on sale of a majority interest in a Subsidiary......... -- 22,132 --
Interest income............................................. 16,435 21,765 20,706
Interest expense............................................ (6,518) (7,183) (5,055)
-------- -------- --------
Loss before provision for income taxes and equity in loss of
unconsolidated affiliate.................................. (60,942) (42,798) (72,571)
Provision for income taxes.................................. 888 859 322
Equity in loss of unconsolidated affiliate.................. (4,656) (1,101) --
-------- -------- --------
Net loss.................................................... $(66,486) $(44,758) $(72,893)
======== ======== ========
Basic and diluted net loss per common share................. $ (1.55) $ (1.09) $ (1.85)
======== ======== ========
Common shares used to calculate basic and diluted net loss
per common share.......................................... 42,826 41,015 39,432
======== ======== ========
</TABLE>

See accompanying notes

57
GILEAD SCIENCES, INC.

CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY

(IN THOUSANDS, EXCEPT SHARE AND PER SHARE AMOUNTS)
<TABLE>
<CAPTION>
ACCUMULATED
OTHER
COMMON STOCK ADDITIONAL COMPREHENSIVE
PREFERRED --------------------- PAID-IN INCOME DEFERRED ACCUMULATED
STOCK SHARES AMOUNT CAPITAL (LOSS) COMPENSATION DEFICIT
--------- ---------- -------- ---------- -------------- ------------- ------------
<S> <C> <C> <C> <C> <C> <C> <C>
Balance at December 31, 1996....... $ -- 38,757,298 $39 $640,762 $ (141) $(916) $(265,095)
Net loss......................... -- -- -- -- -- -- (72,893)
Unrealized gain on
available-for-sale short-term
investments, net............... -- -- -- -- 255 -- --
Foreign currency translation
adjustment..................... -- -- -- -- (164) -- --
Comprehensive loss............. -- -- -- -- -- -- --
Issuance of warrant to related
party.......................... -- -- -- 353 -- -- --
Stock repurchases................ -- (155) -- -- -- -- --
Employee stock purchase plan..... -- 123,909 -- 2,799 -- -- --
Option exercises................. -- 1,251,556 1 12,176 -- -- --
Warrant exercises................ -- 292,609 -- 27 -- -- --
Issuance of 1,133,786 shares of
preferred Stock................ 1 -- -- 39,999 -- -- --
Compensation expense related to
stock option transactions...... -- -- -- 44 -- (44) --
Amortization of deferred
compensation................... -- -- -- -- -- 523 --
---- ---------- --- -------- ------- ----- ---------
Balance at December 31, 1997....... 1 40,425,217 40 696,160 (50) (437) (337,988)
Net loss......................... -- -- -- -- -- -- (44,758)
Unrealized loss on
available-for-sale short-term
investments, net............... -- -- -- -- (301) -- --
Foreign currency translation
adjustment..................... -- -- -- -- 14 -- --
Comprehensive loss............. -- -- -- -- -- -- --
Private issuance of common
stock.......................... -- 364,257 1 9,982 -- -- --
Employee stock purchase plan..... -- 133,404 -- 2,879 -- -- --
Option exercises................. -- 639,959 1 7,509 -- -- --
Amortization of deferred
compensation................... -- -- -- -- -- 212 --
Amounts recognized under
compensatory stock
transactions................... -- -- -- 434 -- -- --
---- ---------- --- -------- ------- ----- ---------
Balance at December 31, 1998....... 1 41,562,837 42 716,964 (337) (225) (382,746)
Net loss......................... -- -- -- -- -- -- (66,486)
Unrealized loss on
available-for-sale short-term
investments, net............... -- -- -- -- (1,602) -- --
Foreign currency translation
adjustment..................... -- -- -- -- (588) -- --
Comprehensive loss............. -- -- -- -- -- -- --
Employee stock purchase plan..... -- 100,166 -- 3,075 -- -- --
Option exercises, net............ -- 1,253,223 1 26,139 -- -- --
Warrant exercises, net........... -- 32,302 -- 80 -- -- --
Conversion of 1,133,786 shares of
preferred stock................ (1) 1,133,786 1 -- -- -- --
Conversion of convertible
subordinated debentures........ -- 10,465 -- 467 -- -- --
Amortization of deferred
compensation................... -- -- -- -- -- 151 --
Amounts recognized under
compensatory stock
transactions................... -- -- -- 2,356 -- -- --
---- ---------- --- -------- ------- ----- ---------
Balance at December 31, 1999....... $ -- 44,092,779 $44 $749,081 $(2,527) $ (74) $(449,232)
==== ========== === ======== ======= ===== =========

<CAPTION>

TOTAL
STOCKHOLDERS'
EQUITY
-------------
<S> <C>
Balance at December 31, 1996....... $374,649
Net loss......................... (72,893)
Unrealized gain on
available-for-sale short-term
investments, net............... 255
Foreign currency translation
adjustment..................... (164)
--------
Comprehensive loss............. (72,802)
Issuance of warrant to related
party.......................... 353
Stock repurchases................ --
Employee stock purchase plan..... 2,799
Option exercises................. 12,177
Warrant exercises................ 27
Issuance of 1,133,786 shares of
preferred Stock................ 40,000
Compensation expense related to
stock option transactions...... --
Amortization of deferred
compensation................... 523
--------
Balance at December 31, 1997....... 357,726
Net loss......................... (44,758)
Unrealized loss on
available-for-sale short-term
investments, net............... (301)
Foreign currency translation
adjustment..................... 14
--------
Comprehensive loss............. (45,045)
Private issuance of common
stock.......................... 9,983
Employee stock purchase plan..... 2,879
Option exercises................. 7,510
Amortization of deferred
compensation................... 212
Amounts recognized under
compensatory stock
transactions................... 434
--------
Balance at December 31, 1998....... 333,699
Net loss......................... (66,486)
Unrealized loss on
available-for-sale short-term
investments, net............... (1,602)
Foreign currency translation
adjustment..................... (588)
--------
Comprehensive loss............. (68,676)
Employee stock purchase plan..... 3,075
Option exercises, net............ 26,140
Warrant exercises, net........... 80
Conversion of 1,133,786 shares of
preferred stock................ --
Conversion of convertible
subordinated debentures........ 467
Amortization of deferred
compensation................... 151
Amounts recognized under
compensatory stock
transactions................... 2,356
--------
Balance at December 31, 1999....... $297,292
========
</TABLE>

See accompanying notes

58
GILEAD SCIENCES, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

(IN THOUSANDS)

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
---------------------------------
1999 1998 1997
--------- --------- ---------
<S> <C> <C> <C>
OPERATING ACTIVITIES:
Net loss.................................................. $ (66,486) $ (44,758) $ (72,893)
Adjustments to reconcile net loss to net cash used in
operating activities:
Depreciation and amortization........................... 12,623 13,231 15,226
Compensation expense from stock option transactions..... 2,356 434 --
Gain on sale of a majority interest in a subsidiary..... -- (22,483) --
Equity in loss of unconsolidated affiliate.............. 4,656 1,101 --
Litigation settlement charges........................... 754 827 10,017
Net additions to (reductions of) allowance for doubtful
accounts.............................................. 888 (407) (114)
Reduction in allowance for note receivable.............. -- (550) --
Net unrealized loss (gain) on foreign currency
transactions.......................................... 2,846 (1,628) 100
Changes in operating assets and liabilities:
Accounts receivable................................... (7,041) (6,523) (6,118)
Inventories........................................... (4,409) 860 (1,004)
Prepaid expenses and other assets..................... (349) 5,298 (13,691)
Accounts payable...................................... 1,443 (502) (4,847)
Accrued liabilities................................... (11,389) 10,159 9,738
Deferred revenue...................................... 1,558 (6,383) 9,131
--------- --------- ---------
Net cash used in operating activities....................... (62,550) (51,324) (54,455)
INVESTING ACTIVITIES:
Purchases of marketable securities........................ (186,997) (488,407) (430,498)
Sales of marketable securities............................ 101,943 390,426 198,515
Maturities of marketable securities....................... 83,677 166,129 100,944
Capital expenditures...................................... (12,475) (11,010) (13,832)
Proceeds from sale of a majority interest in a subsidiary,
net of closing costs.................................... -- 14,652
Proceeds from sale of investment in life science
enterprise.............................................. -- -- 2,683
Investment in unconsolidated affiliate.................... (2,450) (4,900) --
Payments received on note receivable...................... -- 550 706
--------- --------- ---------
Net cash provided by (used in) investing activities......... (16,302) 67,440 (141,482)
--------- --------- ---------
FINANCING ACTIVITIES:
Proceeds from issuance of preferred stock................. -- -- 40,000
Proceeds from issuances of common stock................... 29,295 20,372 15,003
Payments on short-term borrowings, net.................... -- (5,102) (7,438)
Proceeds from issuance of long-term debt.................. 74 4,478 20,334
Repayments of long-term debt.............................. (5,394) (6,606) (32,650)
Proceeds from issuance of convertible subordinated
debentures, net of offering costs....................... -- -- 77,200
--------- --------- ---------
Net cash provided by financing activities................... 23,975 13,142 112,449
--------- --------- ---------
Effect of exchange rate changes on cash..................... 752 573 1,201
--------- --------- ---------
Net increase (decrease) in cash and cash equivalents........ (54,125) 29,831 (82,287)
Cash and cash equivalents at beginning of year.............. 101,136 71,305 153,592
--------- --------- ---------
Cash and cash equivalents at end of year.................... $ 47,011 $ 101,136 $ 71,305
========= ========= =========
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Interest paid............................................. $ 6,234 $ 6,793 $ 2,815
Income taxes paid......................................... 527 790 253
DISCLOSURES OF GAIN ON SALE OF A MAJORITY INTEREST IN A
SUBSIDIARY:
Cash receipts, net of closing costs....................... $ -- $ 14,652 $ --
Receipt of 49% interest in manufacturing facility......... -- 5,500 --
Net present value of guaranteed payments.................. -- 2,668 --
Other..................................................... -- 63 --
Net book value of 51% interest sold....................... -- (751) --
--------- --------- ---------
$ -- $ 22,132 $ --
SCHEDULE OF NON-CASH INVESTMENT AND FINANCING ACTIVITIES:
Purchase of equipment and leasehold improvements through
accounts payable........................................ $ 124 $ 757 $ 889
Common stock issued upon conversion of debentures......... 467 -- --
</TABLE>

See accompanying notes

59
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

DECEMBER 31, 1999

1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

BUSINESS AND ORGANIZATION

Gilead Sciences, Inc. (the "Company" or "Gilead") was incorporated in
Delaware on June 22, 1987, and is an independent biopharmaceutical company that
seeks to provide accelerated solutions for patients and the people who care for
them. The Company discovers, develops, manufactures and commercializes
proprietary therapeutics for challenging infectious diseases (viral, fungal and
bacterial infections) and cancer. Gilead also has expertise in liposomal drug
delivery technology. Currently, the Company markets
AmBisome-Registered Trademark- ((amphotericin B) liposome for injection), an
antifungal agent, DaunoXome-Registered Trademark- (daunorubicin citrate liposome
injection), a drug approved for the treatment of Kaposi's Sarcoma, and
VISTIDE-Registered Trademark- (cidofovir injection) for the treatment of
cytomegalovirus ("CMV") retinitis. Hoffmann-La Roche, Inc. markets Tamiflu-TM-
(oseltamivir phosphate) for the treatment of influenza, under a collaborative
agreement with the Company. In addition, the Company is developing products to
treat diseases caused by human immunodeficiency virus ("HIV") and hepatitis B
virus ("HBV"), bacterial infections and cancer.

As more fully described in Note 2, on July 29, 1999, Gilead entered into a
business combination (the "Merger") with NeXstar Pharmaceuticals, Inc.
("NeXstar"). The business combination has been accounted for as a pooling of
interests and the historical consolidated financial statements of Gilead for all
years prior to the business combination have been restated to include the
financial position, results of operations and cash flows of NeXstar. No material
adjustments were necessary to conform the accounting policies of the two
companies. Costs of the Merger were charged to operations in 1999.

The accompanying consolidated financial statements include the accounts of
the Company and its wholly and majority-owned subsidiaries. Significant
intercompany transactions have been eliminated. Certain reclassifications have
been made to prior year amounts to be consistent with the current year
presentation.

USE OF ESTIMATES

The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the amounts reported in the consolidated financial
statements and accompanying notes. Actual results could differ from those
estimates.

REVENUE RECOGNITION

Product sales revenue is recognized upon passage of legal title of the
inventory and satisfaction of all of the Company's performance obligations. The
Company does not provide its customers with a general right of product return.
However, the Company will accept returns of product that has expired or is
deemed to be damaged or defective. Provisions are made for doubtful accounts,
estimated product returns, cash discounts and government discounts and rebates.

In connection with most of its European product sales, the Company prices
its products in the currency of the country into which they are sold ("Payment
Currencies"). A significant majority of the Company's manufacturing costs are in
U.S. Dollars. Therefore, any decline in the value of the Payment Currencies
relative to the U.S. Dollar is likely to negatively impact gross margins since
the Company's manufacturing costs would remain approximately the same while its
revenue in terms of U.S. Dollars

60
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
would decline. Periodically, the Company's gross margin is adversely affected by
such currency fluctuations.

Contract revenue recognized under the Company's collaborative research and
development ("R&D") arrangements, license and supply agreements and intellectual
property sales and license agreements is recorded as earned based upon the
performance requirements of the underlying contracts. Milestone payments are
recognized as revenue when all of the Company's performance obligations have
been met, the amount of the milestone payment is readily determinable and the
Company has a unilateral right to demand a nonrefundable payment. Payments
received in advance under such agreements are recorded as deferred revenue until
earned.

Royalty revenue from sales of AmBisome is recognized in the month following
that in which the corresponding sales occur. Royalty revenue from sales of
VISTIDE is recognized when received, which is in the quarter following that in
which the corresponding sales occur. Royalty revenue from sales of Tamiflu will
also be recognized in the quarter following that in which the related sales
occur, beginning in the first quarter of 2000.

RESEARCH AND DEVELOPMENT COSTS

All R&D costs, including those funded by third parties, are charged to
expense as incurred.

STOCK-BASED COMPENSATION

In accordance with the provisions of Statement of Financial Accounting
Standards ("SFAS") No. 123, ACCOUNTING FOR STOCK-BASED COMPENSATION, the Company
has elected to follow Accounting Principles Board Opinion ("APB") No. 25,
ACCOUNTING FOR STOCK ISSUED TO EMPLOYEES, and related interpretations in
accounting for its employee stock option plans. Under APB No. 25, if the
exercise price of the Company's employee and director stock options equals or
exceeds the fair value of the underlying stock on the date of grant, no
compensation expense is recognized. See Note 11 for pro forma disclosures of
stock-based compensation pursuant to SFAS No. 123.

BASIC AND DILUTED LOSS PER COMMON SHARE

For all periods presented, both basic and diluted loss per common share are
computed based on the weighted average number of common shares outstanding
during the period. The impact of convertible debentures, stock options and
warrants could potentially dilute basic earnings per share in the future, but
were excluded from the computation of diluted loss per share as their effect is
antidilutive for the periods presented.

CASH AND CASH EQUIVALENTS

The Company considers highly liquid investments with insignificant interest
rate risk and a remaining maturity of three months or less at the purchase date
to be cash equivalents. Gilead may enter into overnight repurchase agreements
under which it purchases securities with an obligation to resell them the
following day. Securities purchased under agreements to resell are recorded at
face value and reported as cash and cash equivalents. Under the Company's
investment policy, it may enter into repurchase agreements ("repos") with major
banks and authorized dealers provided that such

61
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
repos are collateralized by U.S. government securities with a fair value of at
least 102% of the fair value of securities sold to Gilead.

MARKETABLE SECURITIES

Management determines the appropriate classification of its marketable debt
securities at the time of purchase and reevaluates such designation at each
balance sheet date. All of the Company's marketable debt securities are
classified as available-for-sale and carried at estimated fair values and
reported in either cash equivalents or marketable securities. At December 31,
1999, cash and cash equivalents include $14.3 million of securities designated
as available-for-sale ($89.2 million at December 31, 1998). Unrealized gains and
losses on available-for-sale securities are excluded from earnings and reported
as a separate component of stockholders' equity. Interest income includes
interest, dividends, amortization of purchase premiums and discounts, and
realized gains and losses on sales of securities. The cost of securities sold is
based on the specific identification method.

CONCENTRATIONS OF CREDIT RISK

Gilead is subject to credit risk from its portfolio of cash equivalents and
marketable securities. By policy, the Company limits amounts invested in such
securities by maturity, industry group, investment type and issuer, except for
securities issued by the U.S. government. Gilead is not exposed to any
significant concentrations of credit risk from these financial instruments. The
goals of the Company's investment policy, in order of priority, are as follows:

1. Safety and preservation of principal and diversification of risk;

2. Liquidity of investments sufficient to meet cash flow requirements; and

3. Competitive after-tax rate of return.

Gilead is also subject to credit risk from its accounts receivable related
to product sales. A majority of the Company's trade accounts receivable arises
from sales of AmBisome, primarily through sales to the Company's European
subsidiaries and export sales to its distributors in Europe. The Company
performs credit evaluations of its customers' financial condition and has not
required collateral. To date, the Company has experienced only modest credit
losses with respect to its accounts receivable.

INVENTORIES

Raw materials, work in process and finished goods inventories are recorded
at the lower of cost or market, with cost determined on a first-in, first-out
basis. Management periodically reviews the composition of inventory in order to
identify obsolete, slow-moving or otherwise unsaleable items. If such items are
observed and there are no alternate uses for the inventory, the Company will
take a write-down to net realizable value in the period that the units are
identified as impaired. Historically, inventory write-downs have been
insignificant and consistent with management's expectations.

62
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
PROPERTY, PLANT AND EQUIPMENT

Property, plant and equipment are stated at cost less accumulated
depreciation and amortization. Depreciation and amortization are recognized
using the straight-line method. Estimated useful lives are as follows:

<TABLE>
<CAPTION>
DESCRIPTION ESTIMATED USEFUL LIFE (IN YEARS)
- ----------- --------------------------------
<S> <C>
Building and improvements.......................... 20
Laboratory and manufacturing equipment............. 4-8
Office and computer equipment...................... 2-7
</TABLE>

Office and computer equipment includes capitalized computer software. All of
the Company's capitalized software is purchased. The Company has no internally
developed computer software. Leasehold improvements and capitalized leased
equipment are amortized over the shorter of the lease term or the item's useful
life.

LONG-LIVED ASSETS

The carrying value of long-lived assets is reviewed on a regular basis for
the existence of facts or circumstances both internally and externally that may
suggest impairment. Specific potential indicators of impairment include:

- a significant decrease in the fair value of an asset;

- a significant change in the extent or manner in which an asset is used or
a significant physical change in an asset;

- a significant adverse change in legal factors or in the business climate
that affects the value of an asset or an adverse action or assessment by a
regulator;

- an accumulation of costs significantly in excess of the amount originally
expected to acquire or construct an asset; and

- operating or cash flow losses combined with a history of operating or cash
flow losses or a projection or forecast that demonstrates continuing
losses associated with an income-producing asset.

Should there be indication of impairment, the Company will confirm this by
comparing the estimated future cash flows expected to result from the use of the
asset and its eventual disposition to the carrying amount of the asset. In
estimating these future cash flows, assets are grouped at the lowest level for
which there are identifiable cash flows that are largely independent of the cash
flows generated by other asset groups. If the sum of the expected future cash
flows (undiscounted and without interest changes) is less than the carrying
amount of the asset, an impairment loss, measured as the excess of the carrying
value of the asset over its fair value, will be recognized. The cash flow
estimates used in such calculations are based on management's best estimates,
using appropriate and customary assumptions and projections at the time.

63
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
OTHER ACCRUED LIABILITIES

At December 31, 1999 and 1998, other accrued liabilities includes
$2.4 million and $2.1 million, respectively, of accrued litigation settlement
costs. See the Patent Matters discussion in Note 10.

At December 31, 1999 and 1998, other accrued liabilities includes
$1.3 million and $5.0 million, respectively, due to F. Hoffmann-La Roche, Ltd.
and Hoffmann-La Roche, Inc. (collectively, "Roche"). See the Hoffmann-La Roche
discussion in Note 4.

FOREIGN CURRENCY TRANSLATION, TRANSACTIONS AND CONTRACTS

Adjustments resulting from translating the financial statements of the
Company's foreign subsidiaries into U.S. Dollars are excluded from the
determination of net income and are accumulated in a separate component of
stockholders' equity. Net foreign exchange transaction losses are reported as a
selling, general and administrative expense in the consolidated statements of
operations. In 1999, 1998 and 1997 such amounts were $0.5 million, $0.3 million
and $0.3 million, respectively.

The Company hedges certain of its foreign currency exposures related to
outstanding trade accounts receivable and firmly committed purchase transactions
with foreign exchange forward contracts. In general, these contracts do not
expose the Company to market risk because gains and losses on the contracts
offset gains and losses on the transactions being hedged. The Company's exposure
to credit risk from these contracts is a function of changes in interest and
currency exchange rates and, therefore, varies over time. Gilead limits the risk
that counterparties to these contracts may be unable to perform by transacting
only with major U.S. banks. The Company also limits its risk of loss by entering
into contracts that provide for net settlement at maturity. Therefore, the
Company's overall risk of loss in the event of a counterparty default is limited
to the amount of any unrecognized and unrealized gains on outstanding contracts
(i.e., those contracts that have a positive fair value) at the date of default.
At December 31, 1999, the Company has recorded an immaterial net unrealized loss
on its open foreign exchange forward contracts. The Company does not enter into
speculative foreign currency transactions and does not write options.

In accounting for hedges of accounts receivable, the Company's aggregate net
foreign currency transaction gain or loss is reported as a selling, general and
administrative expense. The Company recognizes the net unrealized gain or loss
on outstanding forward contracts based on the difference between the contract
exchange rate and the market exchange rate at each balance sheet date. With
respect to hedges of firmly committed purchase transactions, unrealized gains
and losses on the underlying forward contracts are deferred and reported as a
component of the related transaction in the period in which it occurs.

At December 31, 1999 and 1998, the Company had forward exchange contracts
outstanding of $42.9 million and $42.4 million, respectively. None of these
contracts have maturities that exceed one year.

The Company presently does not hedge its net investment in any of its
foreign subsidiaries.

64
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
FAIR VALUE OF FINANCIAL INSTRUMENTS

The Company's financial instruments consist principally of cash and cash
equivalents, marketable securities, accounts receivable, certain other
non-current assets, forward foreign exchange contracts, accounts payable,
long-term obligations and convertible subordinated debentures. Cash and cash
equivalents, marketable securities and substantially all of the forward foreign
exchange contracts are reported at their respective fair values on the balance
sheet. Management believes the remaining financial instruments, with the
exception of the convertible subordinated debentures, are reported on the
balance sheet at amounts that approximate current fair values. The fair value of
the convertible subordinated debentures at December 31, 1999 and 1998 was
$101.8 million and $69.4 million, respectively (such fair values being
determined by a market maker for the convertible subordinated debentures). This
compares to a carrying value of $79.5 million and $80.0 million at December 31,
1999 and 1998, respectively.

NEW ACCOUNTING PRONOUNCEMENTS

In June 1998, the Financial Accounting Standards Board ("FASB") issued SFAS
No.133, ACCOUNTING FOR DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES, which
establishes accounting and reporting standards for derivative instruments,
including forward foreign exchange contracts, and hedging activities. In
June 1999, the FASB issued SFAS No. 137, ACCOUNTING FOR DERIVATIVE INSTRUMENTS
AND HEDGING ACTIVITIES--DEFERRAL OF THE EFFECTIVE DATE OF FASB STATEMENT
NO. 133. SFAS No. 133 is now effective for fiscal years beginning after
June 15, 2000 and, therefore, the Company will adopt this accounting standard
effective January 1, 2001. Management has not yet determined the impact of SFAS
No. 133 on its financial position or results of operations.

The Company has recognized nonrefundable technology access fees received in
connection with collaboration agreements as revenue when received, when the
technology has been transferred and when all contractual obligations of the
Company relating to the fees are fulfilled. In December 1999, the Securities and
Exchange Commission ("SEC") issued Staff Accounting Bulletin ("SAB") No. 101,
"REVENUE RECOGNITION IN FINANCIAL STATEMENTS." Among other things, SAB No. 101
describes the SEC Staff's position on the recognition of certain nonrefundable
upfront fees received in connection with research collaborations. The Company is
evaluating the applicability of SAB No. 101 to its existing collaborative
agreements. Should the Company conclude that the approach described in SAB
No. 101 is more appropriate, it will change its method of accounting effective
January 1, 2000 to recognize such fees over the term of the related agreement.
Any required adjustment would be recognized as a cumulative effect of a change
in accounting principle.

2. ACQUISITION OF NEXSTAR

On July 29, 1999, the Company acquired all of the outstanding common stock
of NeXstar pursuant to an Agreement and Plan of Merger dated as of February 28,
1999. As a result, NeXstar became a wholly owned subsidiary of Gilead. In
connection with the Merger, Gilead issued a total of 11.2 million shares of
Gilead common stock, or 0.3786 of a share of Gilead common stock for each share
of NeXstar common stock, to NeXstar's stockholders as consideration for all
shares of common stock of NeXstar. In addition, holders of options and warrants
outstanding at the time of the Merger to purchase an aggregate of approximately
2.2 million shares of NeXstar common stock will receive, upon

65
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

2. ACQUISITION OF NEXSTAR (CONTINUED)
exercise of such options and warrants, the same fraction of a share of Gilead
common stock, and holders of $80.0 million principal amount of 6.25% Convertible
Subordinated Debentures of NeXstar ("Debentures") have the right to convert the
Debentures into approximately 1.8 million shares of Gilead common stock. The
Merger is intended to qualify as a tax-free reorganization and has been
accounted for as a pooling of interests.

The table below presents the separate results of operations for Gilead and
NeXstar for the periods prior to the merger and combined results after the
merger:

<TABLE>
<CAPTION>
MERGER-RELATED
(IN THOUSANDS) GILEAD NEXSTAR ADJUSTMENTS TOTAL
- -------------- -------- -------- -------------- --------
<S> <C> <C> <C> <C>
Year ended December 31, 1999
Revenues..................... $ 24,659 $144,320 $ -- $168,979
Net income (loss)............ (73,534) 25,351 (18,303)(a) (66,486)
Year ended December 31, 1998
Revenues..................... $ 32,570 $118,549 $ -- $151,119
Net income (loss)............ (56,075) 10,920 397(b) (44,758)
Year ended December 31, 1997
Revenues..................... $ 40,037 $ 92,221 $ -- $132,258
Net income (loss)............ (27,993) (43,910) (990)(b) (72,893)
</TABLE>

- ------------------------

(a) Merger-related costs

(b) Adjustment required to conform accounting policy. NeXstar's policy was to
capitalize certain patent and trademark costs, while it was Gilead's policy
to charge such items to selling, general and administrative expense in the
period incurred. The accompanying financial statements have been restated
for all periods such that all patent and trademark costs are expensed as
incurred.

As a result of its merger with NeXstar, Gilead incurred merger-related costs
consisting of transaction costs (primarily professional fees, filing fees,
printing costs and other related charges), employee severance costs and the
write-down of certain NeXstar assets that will not be used in continuing
operations. The following table shows the details of the merger-related costs
and accruals at December 31, 1999:

<TABLE>
<CAPTION>
CHARGED TO EXPENSE THROUGH DECEMBER 31, 1999
(IN THOUSANDS) DECEMBER 31, 1999 UTILIZED ACCRUAL BALANCE
- -------------- -------------------------- -------- -----------------
<S> <C> <C> <C>
Merger transaction costs.... $12,214 $12,196 $ 18
Employee severance.......... 5,309 2,821 2,488
Write-down of NeXstar
assets.................... 536 N/A N/A
Other....................... 244 244 --
------- ------- ------
Total..................... $18,303 $15,261 $2,506
======= ======= ======
</TABLE>

As of December 31, 1999, all employees for which severance costs were
accrued had been terminated. The Company anticipates that substantially all
remaining accrued severance costs will be paid to former employees by
September 2000.

66
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

3. AVAILABLE-FOR-SALE SECURITIES

The following is a summary of available-for-sale securities. Estimated fair
values of available-for-sale securities are based on prices obtained from
commercial pricing services (in thousands).

<TABLE>
<CAPTION>
GROSS GROSS
AMORTIZED UNREALIZED UNREALIZED ESTIMATED
COST GAINS LOSSES FAIR VALUE
--------- ---------- ---------- ----------
<S> <C> <C> <C> <C>
DECEMBER 31, 1999
U.S. treasury securities and
obligations of U.S. Government
agencies.......................... $133,444 $512 $(1,243) $132,713
Certificates of deposit............. 5,309 1 -- 5,310
Corporate debt securities........... 70,726 19 (583) 70,162
Asset-backed securities............. 39,554 2 (266) 39,290
Other debt securities............... 14,256 -- -- 14,256
-------- ---- ------- --------
Total............................. $263,289 $534 $(2,092) $261,731
======== ==== ======= ========
DECEMBER 31, 1998
U.S. treasury securities and
obligations of U.S. Government
agencies.......................... $ 78,846 $ 62 $ (123) $ 78,785
Certificates of deposit............. 38,058 65 (11) 38,112
Corporate debt securities........... 34,676 152 (18) 34,810
Asset-backed securities............. 89,565 101 (185) 89,481
Other debt securities............... 95,626 -- -- 95,626
-------- ---- ------- --------
Total............................. $336,771 $380 $ (337) $336,814
======== ==== ======= ========
</TABLE>

The following table presents certain information related to sales of
available-for-sales securities (in thousands):

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
------------------------------
1999 1998 1997
-------- -------- --------
<S> <C> <C> <C>
Proceeds from sales........................... $101,943 $390,426 $198,515
Gross realized gains on sales................. $ 92 $ 1,127 $ 229
Gross realized losses on sales................ $ (475) $ (654) $ (142)
</TABLE>

At December 31, 1999, $128.4 million of the Company's portfolio of
marketable securities (excluding asset-backed securities) has a contractual
maturity of less than one year and $94.0 million of the portfolio has a
contractual maturity greater than one year but less than three years. None of
the estimated maturities of the Company's asset-backed securities exceed three
years.

4. COLLABORATIVE ARRANGEMENTS AND CONTRACTS

FUJISAWA

The Company's rights to market AmBisome are subject to an agreement between
the Company and Fujisawa Healthcare, Inc., as successor to Fujisawa USA, Inc.
("Fujisawa"). Under the terms of the Fujisawa agreement, as amended, Fujisawa
and the Company co-promote AmBisome in the United

67
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

4. COLLABORATIVE ARRANGEMENTS AND CONTRACTS (CONTINUED)
States, Fujisawa has sole marketing rights to AmBisome in Canada and the Company
has exclusive marketing rights to AmBisome in the rest of the world, provided
the Company pays royalties to Fujisawa in connection with sales in most
significant Asian markets, including Japan. In connection with sales in the
United States, Fujisawa purchases AmBisome from the Company at cost. Fujisawa
collects all payments from the sale of AmBisome in the United States, and the
Company receives 20% of the gross profits from the sale of AmBisome in the
United States. The Company also sells AmBisome to Fujisawa Canada at cost plus a
specified percentage. In 1999, 1998 and 1997, the Company recorded
$8.3 million, $4.8 million and $0.7 million of royalty income, respectively, in
connection with the agreement between the Company and Fujisawa.

SUMITOMO

In September 1996, the Company and Sumitomo Pharmaceuticals Co., Ltd.
("Sumitomo") entered into an agreement ("Sumitomo License") pursuant to which
Sumitomo has agreed to develop and market AmBisome in Japan. Under the terms of
the Sumitomo License, Sumitomo paid the Company an initial $7.0 million
licensing fee (less withholding taxes of $0.7 million) in October 1996 and a
$3.0 million milestone payment (less withholding taxes of $0.3 million) in
March 1998. Sumitomo also is required to make additional payments to the Company
if certain clinical and commercial milestones are met and to pay the Company
royalties on all Japanese AmBisome sales. AmBisome is not yet approved for
marketing in Japan.

HOFFMANN-LA ROCHE

In September 1996, Gilead and Roche entered into a collaboration agreement
("Roche Agreement") to develop and commercialize therapies to treat and prevent
viral influenza. Under the Roche Agreement, Roche received exclusive worldwide
rights to Gilead's proprietary influenza neuraminidase inhibitors. In 1996,
Roche made an initial license fee payment to Gilead of $10.3 million. Upon
achieving certain developmental milestones, in both the second and fourth
quarters of 1997, Gilead earned cash payments of $3.0 million per quarter, for a
total of $6.0 million. During 1999, Gilead recognized a total of $12.8 million
of additional milestone payments due to the commencement of certain clinical
trials in Japan, the filing of a marketing authorisation application to market
Tamiflu in the European Union, and the filing and subsequent approval of a New
Drug Application ("NDA") to market Tamiflu in the United States. As of
December 31, 1999, Gilead is entitled to additional cash payments of up to
$21.2 million upon achieving additional developmental and regulatory milestones.
In addition, Roche is required to pay Gilead royalties on net product sales. No
revenues from Roche's sales of Tamiflu have been recognized as net royalty
revenue as of December 31, 1999. The Company will recognize royalty revenue from
sales of Tamiflu in the quarter following that in which the related product
sales occur.

Under the Roche Agreement, Roche also reimburses the Company for its related
R&D costs under the program by funding such costs quarterly and generally in
advance, based on an annual budget. Reimbursements are included in contract
revenue as the Company incurs the related R&D costs. Amounts incurred by the
Company in excess of amounts funded may also be reimbursed, subject to Roche's
approval. In this event, revenue is not recognized until such approval has been
obtained.

68
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

4. COLLABORATIVE ARRANGEMENTS AND CONTRACTS (CONTINUED)
Conversely, if amounts funded by Roche exceed the Company's related R&D costs,
the Company may be required to repay such excess funding to Roche.

For the years ended December 31, 1999, 1998 and 1997, the Company recorded
approximately $2.1 million, $16.4 million and $8.2 million, respectively, of R&D
reimbursement revenue related to the Roche Agreement, which is reported as
contract revenue in the accompanying consolidated statements of operations. The
$16.4 million recorded as revenue during 1998 includes $5.2 million attributable
to R&D expenses incurred in the fourth quarter of 1997, which were subject to
Roche's approval as of December 31, 1997. Such expenses were approved for
reimbursement and recognized in contract revenue in 1998. Except for this
$5.2 million, R&D costs related to the Roche Agreement approximate the
reimbursement revenue in each year presented and are included in R&D expenses.

PHARMACIA & UPJOHN

In August 1996, the Company and Pharmacia & Upjohn S.A. ("Pharmacia &
Upjohn") entered into a License and Supply Agreement ("Pharmacia & Upjohn
Agreement") to market VISTIDE in all countries outside the United States. Under
the terms of the Pharmacia & Upjohn Agreement, Pharmacia & Upjohn paid Gilead an
initial license fee of $10.0 million. During the second quarter of 1997, VISTIDE
was approved for marketing in the European Union by the European Commission,
which triggered an additional cash milestone payment of $10.0 million by
Pharmacia & Upjohn to the Company. Also as a result of achieving this milestone,
in the second quarter of 1997 the Company issued and Pharmacia & Upjohn
purchased 1,133,786 shares of Series B Convertible Preferred Stock for
approximately $40.0 million, or $35.28 per share. The preferred stock
automatically converted into an equal number of shares of common stock in 1999.
For additional information about the preferred stock, refer to Note 11.

Under the terms of the Pharmacia & Upjohn Agreement and related agreements
covering expanded access programs for VISTIDE outside of the United States, the
Company is responsible for maintaining the cidofovir patent portfolio and for
supplying to Pharmacia & Upjohn bulk cidofovir used to manufacture the finished
VISTIDE product ("Product"). Gilead is entitled to receive a royalty based upon
Pharmacia & Upjohn's sales of Product. It receives a portion of the royalty upon
shipping either bulk drug substance or Product to Pharmacia & Upjohn, and the
remainder upon Pharmacia & Upjohn's sale of Product to third parties. Any
royalties that Gilead receives before Product is sold to third parties are
recorded as deferred revenue until such third-party sales occur. At
December 31, 1999, the Company has recorded on its balance sheet approximately
$3.7 million of such deferred revenue ($3.3 million at December 31, 1998). The
Company recognized royalty revenue of $2.0 million, $1.7 million and
$0.7 million in 1999, 1998 and 1997, respectively, from sales of VISTIDE outside
of the United States by Pharmacia & Upjohn.

SOMALOGIC

In November 1999, Gilead and Somalogic, Inc. ("Somalogic") entered into an
agreement whereby Gilead assigned to Somalogic under a sole and exclusive
license certain intellectual property related to the SELEX process, including
patents and patent applications. Under the terms of the agreement, Somalogic is
required to pay Gilead a total of $2.5 million in two nonrefundable
installments. The first $1.5 million was paid in November 1999 and is included
in contract revenue in the Company's

69
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

4. COLLABORATIVE ARRANGEMENTS AND CONTRACTS (CONTINUED)
consolidated statement of operations for the year ended December 31, 1999. The
remaining $1.0 million is due in November 2000 and, because Somalogic is a
developmental stage entity that may require third party financing, Gilead will
recognize this amount as contract revenue when received. Gilead has no ongoing
research or funding obligations under the agreement. At December 31, 1999, the
$1.0 million payment due in November 2000 is reported as deferred revenue on the
consolidated balance sheet.

SCHERING A.G.

In 1993, the Company entered into a collaborative research agreement
("Schering Research Agreement") and license agreement ("Schering License
Agreement") with Schering A.G. Under the Schering Research Agreement, Schering
A.G. has funded research at Gilead for the discovery and development of aptamers
as IN VIVO diagnostic agents. The level of funding under this agreement has
varied over the five-year term, from $1.0 million to $2.4 million annually. In
March 1999, Schering A.G. agreed to fund $0.3 million under the Schering
Research Agreement for the first half of 1999, which Gilead received and
reported in contract revenue in 1999. The Schering Research Agreement expired in
1999 and the Company does not expect to receive any additional payments
thereunder.

Under the Schering License Agreement, Schering A.G. has the right to develop
and commercialize aptamers as IN VIVO diagnostic agents or radiotherapeutics
discovered and developed under the Schering Research Agreement. Schering A.G. is
required to make milestone and royalty payments to the Company upon
commercialization and sale of any products developed under the collaboration
with the Company. The milestone payments for any one product total $6.0 million
and are triggered by the filing of an Investigational New Drug application, the
initiation of Phase III clinical trials, the filing of an NDA and approval of a
product for commercial sale. The Schering License Agreement, which was still in
effect as of December 31, 1999, permits the Company to develop and commercialize
aptamers discovered under the Schering Research Agreement outside the field of
IN VIVO diagnostic agents or radiotherapeutics, subject to royalty payments to
Schering A.G.

ISIS PHARMACEUTICALS

In December 1998, Gilead and Isis Pharmaceuticals, Inc. ("Isis") entered
into an agreement under which Gilead sold to Isis certain intellectual property,
including patents and patent applications covering antisense chemistry and
antisense drug delivery systems. Under the terms of the agreement, Isis is
required to pay to Gilead a total of $6.0 million in four nonrefundable
installments. The first installment of $2.0 million was paid in December 1998,
the second installment of $1.0 million was paid in December 1999 and the
remaining $3.0 million is payable in two additional payments (one payment of
$1.0 million in 2000 and one payment of $2.0 million in 2001). The total sale
price of $6.0 million is included in contract revenue in the Company's
consolidated statement of operations for the year ended December 31, 1998.
Gilead has no ongoing research or funding obligations under the agreement.

GLAXO WELLCOME

In May 1998, the Company entered into a three-part collaboration with Glaxo
Wellcome Inc. ("Glaxo") in which (a) Glaxo received a non-exclusive right to use
the Company's proprietary SELEX process for target validation; (b) the Company
received the exclusive rights (subject to Glaxo's right to

70
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

4. COLLABORATIVE ARRANGEMENTS AND CONTRACTS (CONTINUED)
elect to participate in such activities) to develop and commercialize NX 211, a
liposomal formulation of Glaxo's proprietary topoisomerase I inhibitor
(lurtoctecan); and (c) Glaxo acquired 364,257 shares of the Company's common
stock for $10.0 million in a private offering.

In July 1990, the Company entered into a collaborative research agreement
with Glaxo with respect to the Company's antisense technology. Under the terms
of the Glaxo agreement, as amended over time, the Company received $1.8 million
in 1998, and $3.0 million in both 1997 and 1996, to fund research, which is
reported as contract revenue in the accompanying consolidated statements of
operations. The R&D costs reimbursed by Glaxo approximate the related revenue
and are included in R&D expense. This agreement and the related funding were
terminated in June 1998.

BAUSCH & LOMB

In August 1994, the Company entered into a license and supply agreement with
Bausch & Lomb Incorporated (formerly Storz Instrument Company, a subsidiary of
American Home Products Corporation), to develop and market an eyedrop
formulation of cidofovir for the potential treatment of topical ophthalmic
viruses. The Company received a $0.3 million annual fee under this agreement in
each of the years ended December 31, 1999 and 1997, which is reported as
contract revenue. This agreement was terminated in 1999 and the Company will not
receive any additional payments in the future.

5. INVENTORIES

Inventories are summarized as follows (in thousands):

<TABLE>
<CAPTION>
DECEMBER 31,
-------------------
1999 1998
-------- --------
<S> <C> <C>
Finished goods............................................ $ 3,463 $ 3,672
Work in process........................................... 6,793 5,962
Raw materials............................................. 10,703 6,916
------- -------
$20,959 $16,550
======= =======
</TABLE>

6. PROPERTY, PLANT AND EQUIPMENT

Property, plant and equipment consist of the following (in thousands):

<TABLE>
<CAPTION>
DECEMBER 31,
-------------------
1999 1998
-------- --------
<S> <C> <C>
Building and improvements (including leasehold
improvements)......................................... $ 46,597 $ 44,700
Laboratory and manufacturing equipment.................. 27,204 26,568
Office and computer equipment........................... 20,127 18,969
Capitalized leased equipment............................ 16,042 17,385
Construction in progress................................ 5,540 639
-------- --------
115,510 108,261
Less accumulated depreciation and amortization.......... (64,112) (57,242)
-------- --------
$ 51,398 $ 51,019
======== ========
</TABLE>

71
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

7. INVESTMENT IN UNCONSOLIDATED AFFILIATE

In late 1997, the Company established its NeXstar Technology Products
division which included the Company's proprietary technology called Product
Anchored Sequential Synthesis ("PASS"), a method of synthesizing the
oligonucleotides that are the basis for the products being developed using the
SELEX process. In July 1998, the Company established Proligo L.L.C., a Delaware
limited liability company ("Proligo"), as a wholly owned subsidiary and
transferred all of the assets of the NeXstar Technology Products division to
Proligo. Proligo supplies nucleic acid and peptide synthesis products to the
pharmaceutical and biopharmaceutical industry for sale and use as laboratory
research reagents and in therapeutic and diagnostic products.

On August 15, 1998, the Company sold a 51% interest (the "Interest") in
Proligo to SKW Americas, Inc. ("SKW"). As payment for the Interest, the Company
received $15.0 million in cash and a 49% interest in PerSeptive Biosystems GmbH,
a company in Hamburg, Germany (the "Hamburg Company"), which specializes in the
manufacture of nucleoside phosphoramidite monomers. The 49% interest in the
Hamburg Company had a fair market value of approximately $5.5 million. In
addition, SKW agreed to pay the Company $3.0 million in guaranteed payments
(discounted at 8.5% for gain recognition purposes) and up to $20.5 million in
performance-based milestones over the next four years. During 1999, the Company
received $2.6 million of the guaranteed payments from SKW. The Company also
received a performance-based milestone payment of $1.0 million, which is
reported in contract revenue on the consolidated statement of operations. As
part of the original transaction, the Company contributed $4.9 million and its
49% interest in the Hamburg Company to Proligo. The Company recorded a
$22.1 million gain in connection with this sale in 1998. SKW contributed
$5.1 million and the remaining 51% interest in the Hamburg Company to Proligo.
Also in connection with this transaction, the Company and Proligo agreed that
Proligo would manufacture oligonucleotides required by the Company at cost plus
a fixed percentage. During 1999, the Company purchased oligonucleotides from
Proligo for a total of $0.4 million. This entire amount has been charged to R&D
expense.

The Company accounts for its investment in Proligo using the equity method
of accounting. The net book value of its investment at December 31, 1999 and
1998 was approximately $7.6 million and $10.3 million, respectively, and is
reported in other noncurrent assets on the Company's consolidated balance
sheets. In 1999, the Company recorded its equity in the loss of Proligo of
$4.7 million, which represents its 49% share of Proligo's loss for its fiscal
year ended November 30, 1999. In 1998, the Company recorded its equity in the
loss of Proligo of $1.1 million for the period from August 15, 1998 through
November 30, 1998. The Proligo operating loss for December 1999 was
approximately $0.9 million, of which the Company will recognize its 49% share in
2000.

In October 1999, the Company made a capital contribution to Proligo of
$2.5 million to maintain its 49% ownership interest. The Company also agreed to
contribute an additional $2.5 million in 2000, again to maintain its 49%
ownership interest. Upon making this capital contribution in January 2000, the
Company has no commitments to provide additional funding to Proligo.

72
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

8. LONG-TERM OBLIGATIONS

Long-term obligations consist of the following (in thousands):

<TABLE>
<CAPTION>
DECEMBER 31,
-------------------
1999 1998
-------- --------
<S> <C> <C>
Capital lease obligations: Interest payable monthly at 6.89%
to 13.91%................................................. $5,681 $7,901
Adjustable rate debt: Quarterly installments through 2000;
unsecured; interest payable quarterly based on applicable
LIBOR rates............................................... -- 1,313
Fixed rate debt: Monthly installments through 2003; secured
by equipment; interest payable monthly at 9.69% to
12.62%.................................................... 2,763 4,511
------ ------
Total long-term obligations................................. 8,444 13,725
Less current portion........................................ (3,191) (4,842)
------ ------
Long-term obligations due after one year.................... $5,253 $8,883
====== ======
</TABLE>

Maturities of all long-term obligations, including capital lease
obligations, due subsequent to December 31, 1999 are as follows (in thousands):

<TABLE>
<CAPTION>
YEAR ENDING DECEMBER 31, AMOUNT
- ------------------------ --------
<S> <C>
2000........................................................ $3,191
2001........................................................ 3,050
2002........................................................ 1,902
2003........................................................ 301
------
Total....................................................... $8,444
======
</TABLE>

The terms of the various debt agreements require the Company to comply with
certain financial and operating covenants. At December 31, 1999, the Company was
in compliance with all such covenants.

9. CONVERTIBLE SUBORDINATED DEBENTURES

During the third quarter of 1997, the Company sold $80.0 million of 6.25%
Debentures due 2004 in a private offering to SBC Warburg Inc. and Oppenheimer &
Co., Inc., which resold the Debentures to a group of private investors. The
Debentures were issued pursuant to an indenture and are convertible into a total
of up to 1,794,844 shares of the Company's common stock at $44.57 per share,
which was greater than the fair market value of the Company's common stock at
the time the Debentures were issued. The Company reserved 1,794,844 shares of
its authorized common stock for issuance upon conversion of the Debentures. The
Debentures are redeemable in whole or in part, at the option of the Company, at
any time on or after August 10, 2000, at specified redemption prices plus
accrued interest. During 1999, holders of $0.5 million of Debentures converted
their holdings into 10,465 shares of common stock.

73
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

10. COMMITMENTS AND CONTINGENCIES

LEASES AND FINANCING ARRANGEMENTS

The Company has entered into long-term noncancelable operating leases for
facilities in Boulder, Colorado, Foster City, California and San Dimas,
California. The leases contain the following terms:

<TABLE>
<CAPTION>
LOCATION TERMINATION DATE RENEWAL OPTIONS
- -------- ---------------- -------------------
<S> <C> <C>
Boulder, CO............................. October 2001 Two five-year terms
Boulder, CO............................. July 2003 None
Foster City, CA......................... December 2003 None
Foster City, CA......................... March 2006 Two five-year terms
Foster City, CA......................... September 2006 Two five-year terms
San Dimas, CA........................... May 2003 Two five-year terms
San Dimas, CA........................... November 2003 Two five-year terms
</TABLE>

Rent expense net of sublease income under the Company's operating leases
totaled approximately $7.9 million, $6.8 million and $6.8 million for the years
ended December 31, 1999, 1998 and 1997, respectively.

The Company has entered into certain financing and sale-leaseback
transactions and related equipment and facilities improvement master lease and
financing agreements for manufacturing equipment, general laboratory and
scientific equipment, office equipment, furniture, fixtures and facilities
improvements. Title to assets acquired under the Company's lease lines of credit
resides with the lessor. The Company has the option to purchase the assets at
the end of the lease terms at fair market value. The leases have terms ranging
from three to five years. At December 31, 1999, no amounts were available under
such agreements.

Aggregate noncancelable future minimum rental payments under operating and
capital leases, net of aggregate future minimum rentals to be received by the
Company under noncancelable subleases, are as follows (in thousands):

<TABLE>
<CAPTION>
OPERATING LEASES, NET OF
YEARS ENDING DECEMBER 31, NONCANCELABLE SUBLEASES CAPITAL LEASES
- ------------------------- ------------------------ --------------
<S> <C> <C>
2000....................................... $ 8,458 $ 2,607
2001....................................... 8,430 2,449
2002....................................... 9,661 1,294
2003....................................... 8,999 --
2004....................................... 5,672 --
Thereafter................................. 6,870 --
------- -------
$48,090 6,350
=======
Less amount representing interest.......... (669)
-------
Total capital lease obligations............ 5,681
Less current portion....................... (2,192)
-------
Capital lease obligations due after one
year..................................... $ 3,489
=======
</TABLE>

74
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

10. COMMITMENTS AND CONTINGENCIES (CONTINUED)
The Company has in place a letter of credit agreement from a bank, which
secures the aggregate future payments under one of its facilities leases. At
December 31, 1999, a total of $0.5 million was secured under this letter of
credit arrangement.

CONTINGENT LIABILITIES

In connection with the August 1998 sale of a majority interest in its
subsidiary, Proligo, as described in Note 7, the Company transferred certain
property and equipment with a net book value of $4.5 million to Proligo. The
majority of such property and equipment is financed or leased by the Company in
accordance with the financing arrangements and sale-leaseback transactions
described above. Concurrent with this transfer of property and equipment, the
Company transferred the underlying debt to Proligo pursuant to various Sublease,
Consent and Assignment Agreements (collectively, the "Sublease Agreements"). As
a result, the Company is required to pay the debt financing and lease
liabilities to the financial institutions and lessors directly for Proligo's
share of the liabilities. Proligo is required to reimburse the Company for these
amounts and is bound by the same terms and conditions as those in the Company's
agreements with the financial institutions and lessors. If Proligo were to
default on its obligations under the Sublease Agreements, the Company would
continue to be liable for amounts outstanding as of the date of the default.
However, in this event, SKW would be obligated to reimburse the Company for 51%
of such amounts paid. At December 31, 1999, Proligo was current with respect to
its reimbursements to the Company and the balance of Proligo's future lease and
debt obligations under the Sublease Agreements was $1.9 million.

Additionally, the Company and Proligo entered into Assignment, Assumption
and Consent Agreements ("Agreements") with the landlords of two laboratory
facilities Proligo occupies. Under the Agreements, Proligo has assumed the
obligations to the landlords, but the Company remains contingently liable in the
event of default. The total unpaid amount of such operating lease commitments as
of December 31, 1999 was approximately $0.4 million.

Gilead has subleased certain of its facilities, primarily in California,
through 2001. If any of the sublessees default on their obligations under these
subleases, the Company would be primarily liable to the original lessor. The
total amount due under these subleases as of December 31, 1999 is $3.0 million.

SHORT-TERM BORROWINGS

In September 1997, the Company entered into an unsecured bank line of credit
for $10.0 million (the "Credit Agreement"). Under the terms of the Credit
Agreement, the Company is required to maintain certain financial ratios. There
are also limitations on the Company's ability to incur additional debt or to
engage in certain significant transactions. The Credit Agreement, which includes
a foreign exchange facility, was being renegotiated as of December 31, 1999 and
was subsequently extended until April 2001. There were no amounts outstanding
under this agreement as of either December 31, 1999 or 1998.

75
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

10. COMMITMENTS AND CONTINGENCIES (CONTINUED)
PATENT MATTERS

On August 11, 1997, the Company and The Liposome Company, Inc. ("TLC")
reached a settlement ("Settlement Agreement") in which the two companies agreed
to dismiss all legal proceedings involving TLC's reexamined U.S. Patent
No. 4,880,635 ("TLC 635 Patent") and U.S. Patent No. 5,578,320 ("TLC 320
Patent") and their international counterparts. The legal proceedings related to
whether AmBisome, the Company's liposomal formulation of amphotericin B,
infringed TLC's patents because of the manner in which it is freeze dried
(lyophilized). In the Settlement Agreement between the parties, TLC granted the
Company immunity from suit in connection with the worldwide production and sales
of AmBisome and a worldwide right to use both the TLC 635 Patent and the TLC 320
Patent. Under the terms of the Settlement Agreement, the Company made an initial
payment to TLC of $1.8 million and was required to make payments beginning in
1998 based on AmBisome sales over the next several years. Because the payments
are subject to certain minimum and maximum amounts, the Company recorded
accounting charges in 1997 of $11.8 million, of which $10.0 million represented
the net present value of all future minimum payments and $1.8 million
represented the initial cash payment. Beginning in 1998, the Company is
recording an expense each quarter based on the difference between all future
minimum payments and the expense recorded in 1997. In addition, beginning in
1998, the Company is recognizing as cost of goods sold the difference between
the minimum and maximum payments, if any. The Company does not expect the
difference between its future minimum and maximum payments to TLC to be
material.

In August 1998, The Company was served with a patent infringement lawsuit
filed by Chiron Corporation ("Chiron") in the U.S. District Court for the
Northern District of California. In the lawsuit, Chiron alleged that Gilead
conducted scientific research that infringes Chiron patents covering the
hepatitis C protein and gene sequences and their use in screening for potential
hepatitis C therapeutics. In, December 1999, Gilead and Chiron agreed to the
terms of a settlement agreement and, as a result, the Company made a one-time
settlement payment of $0.4 million to Chiron at that time.

LEGAL PROCEEDINGS

The Company is involved from time to time in legal proceedings arising in
the ordinary course of its business. In the opinion of management, none of these
matters is expected to have a material adverse effect on the financial position
or operations of the Company based on factors currently known to management.

11. STOCKHOLDERS' EQUITY

PREFERRED STOCK

The Company has 5,000,000 shares of authorized preferred stock issuable in
series. The Company's Board of Directors ("Board") is authorized to determine
the designation, powers, preferences and rights of any such series. The Company
has reserved 400,000 shares of preferred stock for potential issuance under the
Preferred Share Purchase Rights Plan.

In June 1997, the Company issued 1,133,786 shares of Series B Convertible
Preferred Stock ("Preferred Stock") to Pharmacia & Upjohn for approximately
$40.0 million, or $35.28 per share. On

76
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

11. STOCKHOLDERS' EQUITY (CONTINUED)
July 15, 1999, the average of the closing price of the Company's common stock
for the thirty days then ended was $49.79. This event triggered the automatic
conversion of the Preferred Stock owned by Pharmacia & Upjohn into the Company's
common stock. Accordingly, the Preferred Stock converted into 1,133,786 shares
of common stock at the original issue price of $35.28 per share on July 16,
1999.

EMPLOYEE STOCK PURCHASE PLAN

Under Gilead's Employee Stock Purchase Plan ("ESPP"), employees can purchase
shares of Gilead common stock based on a percentage of their compensation. The
purchase price per share must equal at least the lower of 85 percent of the
market value on the date offered or the date purchased. A total of 1,580,000
shares of common stock are reserved for issuance under the ESPP. As of
December 31, 1999, 881,283 shares had been issued under the ESPP (794,049 shares
as of December 31, 1998).

Emerging Issues Task Force ("EITF") Issue No. 97-12, ACCOUNTING FOR
INCREASED SHARE AUTHORIZATIONS IN AN IRS SECTION 423 EMPLOYEE STOCK PURCHASE
PLAN UNDER APB OPINION NO. 25, provides that new shares authorized under
existing Section 423 employee stock purchase plans may give rise to compensation
expense under circumstances specified in that accounting standard. During 1998,
Gilead recognized compensation expense of $0.4 million related to an ESPP share
authorization approved in 1998 in accordance with the provisions of EITF Issue
No. 97-12. In future years, the Company will not be required to recognize
additional compensation expense related to the 1998 share authorization.

STOCK OPTION PLANS

In December 1987, Gilead adopted the 1987 Incentive Stock Option Plan and
the Supplemental Stock Option Plan for issuance of common stock to employees,
consultants and scientific advisors. In April 1991, the Board approved the
granting of certain additional nonqualified stock options with terms and
conditions substantially similar to those granted under the 1987 Supplemental
Stock Option Plan. At the grant date, none of the options described above had
exercise prices that were less than the fair value of the underlying stock on
that date. The options vest over five years pursuant to a formula determined by
the Board and expire after ten years. No shares are available for grant of
future options under any of these plans.

In November 1991, Gilead adopted the 1991 Stock Option Plan ("1991 Plan")
for issuance of common stock to employees and consultants. Options issued under
the 1991 Plan shall, at the discretion of the Board, be either incentive stock
options or nonqualified stock options. In May 1998, the 1991 Plan was amended
such that the exercise price of all stock options must be at least equal to the
fair value of Gilead's common stock on the date of grant. The options vest over
five years pursuant to a formula determined by the Board and expire after ten
years. At December 31, 1999, 3,185,020 shares were available for grant of future
options.

In November 1995, Gilead adopted the 1995 Non-Employee Directors' Stock
Option Plan ("Directors' Plan") for issuance of common stock to non-employee
Directors pursuant to a predetermined formula. The exercise price of options
granted under the Directors' Plan must be at least equal to the fair value of
Gilead's common stock on the date of grant. The options vest over five

77
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

11. STOCKHOLDERS' EQUITY (CONTINUED)
years from the date of grant in quarterly 5 percent installments and expire
after ten years. At December 31, 1999, 239,000 shares were available for grant
of future options under the Directors' Plan.

NeXstar's stock plans include the 1988 Stock Option Plan ("1988 Plan"), the
1993 Incentive Stock Plan, and the 1995 Director Option Plan (collectively,
"NeXstar Plans"). Options pursuant to the 1988 Stock Option Plan and the 1993
Incentive Stock Plan that were issued and outstanding as of July 29, 1999 have
been converted into options to purchase Gilead common stock as a result of the
Merger and remain subject to their original terms and conditions. Options
outstanding under the 1995 Director Option Plan became fully vested at the close
of the Merger and are exercisable for a period of 24 months thereafter. No
shares are available for grant of future options under any of the NeXstar Plans.

NeXstar's 1988 Plan allows certain option holders to execute cashless
exercises of options. In a cashless exercise transaction, the option holder
specifies how many shares will be exercised and the Company issues the specified
number of shares, less the number that would be required to cover the exercise
price based on the fair value of the stock on the exercise date. During 1999,
several option holders performed cashless exercises. As a result, NeXstar' 1988
Plan is considered to be a variable plan and, therefore, the Company recognized
compensation expense of $2.3 million. Of this amount, $1.5 million relates to
exercised options and the remaining $0.8 million relates to options that remain
outstanding under the 1988 Plan at December 31, 1999.

The following table summarizes activity under all Gilead and NeXstar stock
option plans for each of the three years in the period ended December 31, 1999.
All option grants presented in the table had exercise prices not less than the
fair value of the underlying stock on the grant date (shares in thousands):

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31, 1998
---------------------------------------------------------------
1999 1998 1997
------------------- ------------------- -------------------
WEIGHTED WEIGHTED WEIGHTED
AVERAGE AVERAGE AVERAGE
EXERCISE EXERCISE EXERCISE
SHARES PRICE SHARES PRICE SHARES PRICE
-------- -------- -------- -------- -------- --------
<S> <C> <C> <C> <C> <C> <C>
Outstanding,
Beginning of year.............. 5,656 $24.38 5,246 $22.36 5,569 $17.77
Granted...................... 1,669 54.84 1,428 27.49 1,263 30.67
Forfeited.................... (371) 33.61 (378) 31.20 (333) 24.49
Exercised.................... (1,323) 21.52 (640) 11.74 (1,253) 9.73
------ ------ ------ ------ ------ ------
Outstanding, end of year......... 5,631 $33.36 5,656 $24.38 5,246 $22.36
====== ====== ====== ====== ====== ======
Exercisable, end of year......... 2,276 $22.56 2,518 $20.51 2,190 $17.08
====== ====== ====== ====== ====== ======
Weighted Avg. Fair Value of
Options Granted................ $33.53 $15.46 $16.51
</TABLE>

78
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

11. STOCKHOLDERS' EQUITY (CONTINUED)

The following is a summary of Gilead options outstanding and options
exercisable at December 31, 1999 (options in thousands):

<TABLE>
<CAPTION>
OPTIONS OUTSTANDING OPTIONS EXERCISABLE
-------------------------------------- ----------------------------
WEIGHTED
AVERAGE WEIGHTED
RANGE OF REMAINING AVERAGE WEIGHTED
EXERCISE OPTIONS CONTRACTUAL EXERCISE OPTIONS AVERAGE
PRICES OUTSTANDING LIFE IN YEARS PRICE EXERCISABLE EXERCISE PRICE
- ---------------------------- ----------- ------------- -------- ----------- --------------
<S> <C> <C> <C> <C> <C>
$0.24--$22.50 1,464 4.59 $14.61 1,162 $13.55
$22.88--$27.65 1,338 7.69 $24.88 418 $25.21
$29.63--$41.06 1,409 6.72 $34.55 601 $34.06
$41.27--$85.95 1,420 8.96 $59.50 95 $48.25
------ ------
Total....................... 5,631 6.96 $33.36 2,276 $22.56
====== ======
</TABLE>

PRO FORMA DISCLOSURES

The table below presents the combined net loss and basic and diluted loss
per common share if compensation cost for both Gilead's and NeXstar's stock
option plans had been determined based on their estimated fair values at the
grant dates for awards under those plans.

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
------------------------------
1999 1998 1997
-------- -------- --------
<S> <C> <C> <C>
Pro forma net loss (in thousands).............. $(93,816) $(61,444) $(87,393)
Pro forma basic and diluted net loss per
share........................................ $ (2.19) $ (1.50) $ (2.22)
</TABLE>

Fair values of the options granted under the stock option plans were
estimated at grant dates using a Black-Scholes option pricing model. The Company
used the multiple option approach and the following assumptions:

<TABLE>
<CAPTION>
1999 1998 1997
-------- ------------ ------------
<S> <C> <C> <C>
Expected life in years (from vesting
date)--Stock options................... 1.86 1.44 to 1.78 1.00 to 1.75
Expected life in years--ESPP 1.21 1.51 0.75
Interest rate--Stock options............. 5.6% 4.7% to 5.5% 5.6% to 6.2%
Interest rate--ESPP...................... 5.0% 5.2% 5.6%
Volatility(1)............................ 67% 66% 66%
Expected dividend yield.................. 0% 0% 0%
</TABLE>

- ------------------------

(1) NeXstar's volatility rates for 1998 and 1997 were 61% and 52%, respectively.

The weighted average estimated fair value of each Gilead ESPP option granted
for the years ended December 31, 1999, 1998 and 1997 was $16.22, $11.97 and
$9.57, respectively.

79
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

11. STOCKHOLDERS' EQUITY (CONTINUED)
PREFERRED SHARE PURCHASE RIGHTS PLAN

In November 1994, the Company adopted a Preferred Share Purchase Rights Plan
(the "Plan"). The Plan provides for the distribution of a preferred stock
purchase right (a "Right") as a dividend for each share of Gilead common stock
held of record at the close of business on December 14, 1994. The Rights are not
currently exercisable. Under certain conditions involving an acquisition or
proposed acquisition by any person or group of 15% or more of the Company's
common stock, the Rights permit the holders (other than the 15% holder) to
purchase Gilead common stock at a 50% discount from the market price at that
time, upon payment of an exercise price of a specified exercise price per Right.
In addition, in the event of certain business combinations, the Rights permit
the purchase of the common stock of an acquirer at a 50% discount from the
market price at that time. Under certain conditions, the Rights may be redeemed
by the Board in whole, but not in part, at a price of $.01 per Right. The Rights
have no voting privileges and are attached to and automatically trade with
Gilead common stock.

In October 1999, the Board of Directors approved an amendment to the Plan.
This amendment provides, among other things, for an increase in the exercise
price of the right under the Plan from $60 to $400 and an extension of the term
of the Plan from November 21, 2004 to October 20, 2009.

12. COMPREHENSIVE INCOME

The following reclassification adjustments are required to avoid
double-counting net realized gains on sales of securities that were previously
included in comprehensive income prior to the sales of the securities (in
thousands):

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
------------------------------
1999 1998 1997
-------- -------- --------
<S> <C> <C> <C>
Net gain (loss) on sales of securities included in
interest income.................................... $ (383) $ 473 $ 87
======= ===== ====
Other comprehensive income:
Net unrealized gain (loss) arising during the
year............................................. $(1,985) $ 172 $342
Reclassification adjustment........................ 383 (473) (87)
------- ----- ----
Net unrealized gain (loss) reported in other
comprehensive income............................... $(1,602) $(301) $255
======= ===== ====
</TABLE>

The balance of accumulated other comprehensive loss as reported on the
balance sheet consists of the following components (in thousands):

<TABLE>
<CAPTION>
DECEMBER 31,
-------------------
1999 1998
-------- --------
<S> <C> <C>
Net unrealized (loss) gain on available-for-sale
securities................................................ $(1,559) $ 43
Cumulative loss on foreign currency translation............. (968) (380)
------- -----
Accumulated other comprehensive loss...................... $(2,527) $(337)
======= =====
</TABLE>

80
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

13. DISCLOSURES ABOUT SEGMENTS OF AN ENTERPRISE AND RELATED INFORMATION

Effective January 1, 1998, the Company adopted SFAS No. 131,
"DISCLOSURES ABOUT SEGMENTS OF AN ENTERPRISE AND RELATED INFORMATION."
Statement No. 131 establishes standards for the way that public business
enterprises report information about operating segments in annual financial
statements and requires that those enterprises report selected information
about operating segments in interim financial reports. It also establishes
standards for related disclosures about products and services, geographic
areas and major customers. The Company has determined that it only has one
reportable segment because management has organized the business along its
functional lines.

PRODUCT SALES REVENUES

Product sales revenues consisted of the following (in thousands):

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
------------------------------
1999 1998 1997
-------- -------- --------
<S> <C> <C> <C>
AmBisome...................................... $129,177 $103,430 $ 83,918
DaunoXome..................................... 4,775 4,672 5,234
VISTIDE....................................... 5,938 6,074 11,735
-------- -------- --------
$139,890 $114,176 $100,887
======== ======== ========
</TABLE>

REVENUES FROM EXTERNAL CUSTOMERS AND COLLABORATIVE PARTNERS BY GEOGRAPHIC REGION

The following table summarizes revenues from external customers and
collaborative partners by geographic region. Revenues are attributed to
countries based on the location of the customer or collaborative partner (in
thousands).

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
------------------------------
1999 1998 1997
-------- -------- --------
<S> <C> <C> <C>
United States................................. $ 28,389 $ 23,601 $ 17,679
Germany....................................... 21,647 22,254 17,063
United Kingdom................................ 19,259 17,241 17,794
Switzerland................................... 15,763 16,400 14,200
Italy......................................... 16,293 13,420 10,993
Spain......................................... 14,625 11,934 8,880
France........................................ 8,347 4,993 3,155
Sweden........................................ 4,400 1,696 10,802
Other European countries...................... 27,100 25,340 23,665
Other foreign countries....................... 13,156 14,240 8,027
-------- -------- --------
Consolidated total............................ $168,979 $151,119 $132,258
======== ======== ========
</TABLE>

81
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

13. DISCLOSURES ABOUT SEGMENTS OF AN ENTERPRISE AND RELATED INFORMATION
(CONTINUED)

At December 31, 1999, the net book value of the Company's property,
plant and equipment was $51.4 million. Approximately 93% of such assets were
located in the United States. At December 31, 1998, the net book value of
the Company's property, plant and equipment was approximately
$51.0 million. Approximately 92% of such assets were located in the United
States.

MAJOR CUSTOMER

In 1999, 1998 and 1997, sales to one distributor accounted for approximately
14%, 13% and 14% of product revenues, respectively.

14. INCOME TAXES

The Company has no deferred provision for income taxes. The current
provision for income taxes consists of the following (in thousands):

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
------------------------------------
1999 1998 1997
-------- -------- --------
<S> <C> <C> <C>
Current:
Federal............................................ $ 65 $160 $ --
State.............................................. 30 21 --
Foreign............................................ 793 678 322
---- ---- ----
$888 $859 $322
==== ==== ====
</TABLE>

Foreign pre-tax income (loss) was $2.0 million, 0.1 million and ($2.8)
million in 1999, 1998 and 1997, respectively.

The difference between the provision for taxes on income and the amount
computed by applying the federal statutory income tax rate to income before
provision for income taxes and equity in loss of unconsolidated affiliate is
explained below (in thousands):

<TABLE>
<CAPTION>
YEAR ENDED DECEMBER 31,
------------------------------
1999 1998 1997
-------- -------- --------
<S> <C> <C> <C>
Loss before provision for income taxes......... $(60,942) $(42,798) $(72,571)
======== ======== ========
Tax at federal statutory rate.................. $(20,720) $(14,552) $(24,675)
Unbenefitted losses............................ 21,074 14,698 24,660
Other.......................................... 534 713 337
-------- -------- --------
$ 888 $ 859 $ 322
======== ======== ========
</TABLE>

At December 31, 1999, the Company had U.S. federal and state net operating
loss carryforwards of $413.3 million and $69.8 million, respectively. The
federal net operating loss carryforwards will expire at various dates beginning
in 2001 through 2019, if not utilized. The state net operating loss
carryforwards will expire at various dates from 2000 through 2012, if not
utilized. Utilization of net operating losses may be subject to an annual
limitation due to ownership change limitations provided in

82
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

14. INCOME TAXES (CONTINUED)
the Internal Revenue Code and similar state provisions. This annual limitation
may result in the expiration of the net operating losses and credits before
utilization.

Deferred income taxes reflect the net tax effects of temporary differences
between the carrying amounts of assets and liabilities for financial reporting
purposes and the amounts used for income tax purposes. Significant components of
the Company's deferred tax assets and liabilities as of December 31, 1999 and
1998 are as follows (in thousands):

<TABLE>
<CAPTION>
DECEMBER 31,
---------------------
1999 1998
--------- ---------
<S> <C> <C>
Net operating loss carryforwards...................... $ 144,600 $ 125,439
Research and other credits............................ 27,400 24,985
Capitalized R&D for California........................ 14,800 11,200
Other, net............................................ 7,400 8,987
--------- ---------
Total deferred tax assets........................... $ 194,200 $ 170,611
Valuation allowance................................... (194,200) (170,611)
--------- ---------
Net deferred tax assets recognized.................... $ -- $ --
========= =========
</TABLE>

The valuation allowance increased by $23.6 million and $34.2 million for the
years ended December 31, 1999 and 1998, respectively. Approximately
$24.4 million of the valuation allowance at December 31, 1999 relates to the tax
benefits of stock option deductions, which will be credited to additional
paid-in capital when realized.

15. RETIREMENT SAVINGS PLAN

As of December 31, 1999, Gilead maintained two separate retirement savings
plan pursuant to which eligible employees may defer compensation for income tax
purposes under Section 401(k) of the Internal Revenue Code of 1986 ("Savings
Plans"). One Savings Plan primarily covers NeXstar employees ("NeXstar Plan"),
while the other Savings Plan primarily covers all other eligible employees of
the combined company ("Gilead Plan"). Under the NeXstar Plan, employee
contributions are discretionary, but may not exceed 15% of eligible annual
compensation. In addition, the NeXstar Plan includes a Company match of 50% of
employee contributions up to a maximum of 6% of eligible annual compensation.
For the years ended December 31, 1999, 1998, and 1997, the Company recorded
contribution expenses related to the NeXstar Plan of approximately
$0.5 million, $0.5 million and $0.6 million, respectively. At December 31, 1999,
approximately $0.9 million, representing 17,225 shares of the Company's common
stock, was held by the NeXstar Plan in trust for plan participants. Effective
February 1995, contributions to the NeXstar Plan may not be invested in the
Company's common stock.

16. RELATED PARTY TRANSACTIONS

During 1999 and 1998, Gilead paid an aggregate of $6.7 million and
$4.7 million, respectively, to PharmaResearch Corporation, a contract research
organization, for services rendered in connection

83
GILEAD SCIENCES, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)

DECEMBER 31, 1999

16. RELATED PARTY TRANSACTIONS (CONTINUED)
with clinical studies. A member of the Board is a senior advisor to an
investment fund that owns a controlling interest in PharmaResearch Corporation.

17. QUARTERLY RESULTS (UNAUDITED)

The following table is in thousands, except per share amounts:

<TABLE>
<CAPTION>
1ST QUARTER 2ND QUARTER 3RD QUARTER 4TH QUARTER
----------- ----------- ----------- -----------
<S> <C> <C> <C> <C>
1999
Total revenues.................. $38,276 $43,537 $38,390 $48,776
Total costs and expenses........ 54,937 55,791 69,608 59,502
Net loss........................ (15,476) (11,691) (30,365) (8,954)
Basic and diluted net loss per
share......................... (.37) (.28) (.70) (.20)

1998
Total revenues.................. $41,513 $35,289 $31,866 $42,451
Total costs and expenses........ 55,209 57,528 53,483 64,411
Net income (loss)............... (10,066) (18,287) 2,202 (18,607)
Basic and diluted net income
(loss) per share.............. (.25) (.45) .05 (.45)
</TABLE>

84
GILEAD SCIENCES, INC.
SCHEDULE II: VALUATION AND QUALIFYING ACCOUNTS

<TABLE>
<CAPTION>
ADDITIONS ADDITIONS
BALANCE AT ---------- ---------- BALANCE AT
BEGINNING OF CHARGED TO CHARGED TO END OF
PERIOD EXPENSE OTHER DEDUCTIONS PERIOD
------------ ---------- ---------- ---------- ----------
<S> <C> <C> <C> <C> <C>
YEAR ENDED DECEMBER 31, 1999
Allowance for doubtful accounts......... $ 1,480 $1,059 $ -- $ 206 $ 2,333
Valuation allowance for deferred tax
assets................................ 170,611 -- 23,589(3) -- 194,200
-------- ------ ------- ------ --------
$172,091 $1,059 $23,589 $ 206 $196,533
======== ====== ======= ====== ========
YEAR ENDED DECEMBER 31, 1998
Allowance for doubtful accounts......... $ 1,883 $ (294)(1) $ -- $ 109 $ 1,480
Allowance for other noncurrent assets... 1,737 (550)(2) -- 1,187(2) --
Valuation allowance for deferred tax
assets................................ 136,411 -- 34,200(3) -- 170,611
-------- ------ ------- ------ --------
$140,031 $ (844) $34,200 $1,296 $172,091
======== ====== ======= ====== ========
YEAR ENDED DECEMBER 31, 1997
Allowance for doubtful accounts......... $ 2,002 $ 306 $ -- $ 425 $ 1,883
Allowance for other noncurrent assets... 1,737 -- -- -- 1,737
Valuation allowance for deferred tax
assets................................ 106,380 -- 30,031(3) -- 136,411
-------- ------ ------- ------ --------
$110,119 $ 306 $30,031 $ 425 $140,031
======== ====== ======= ====== ========
</TABLE>

- ------------------------

(1) In August 1996, a major customer of the Company filed for bankruptcy
protection under Chapter 11 of the U.S. Bankruptcy Code. The total
receivable outstanding from that customer as of December 31, 1996 of
$0.6 million was reserved. In 1997, the Company collected approximately
$0.1 million of this amount by assigning its claim to a third party. In
1998, the Company reversed that portion of the allowance for doubtful
accounts no longer deemed necessary.

(2) The Company accepted $550,000 in full settlement of an outstanding note
receivable that was fully reserved on the balance sheet.

(3) Charged to deferred tax benefit.

85
SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Registrant has duly caused this Report to be signed on
its behalf by the undersigned, thereunto duly authorized.

<TABLE>
<S> <C> <C>
GILEAD SCIENCES, INC.

By: /s/ JOHN C. MARTIN
-----------------------------------------
John C. Martin
PRESIDENT AND CHIEF EXECUTIVE OFFICER
</TABLE>

POWER OF ATTORNEY KNOW ALL PERSONS BY THESE PRESENTS, that each person whose
signature appears below constitutes and appoints John C. Martin and Mark L.
Perry, and each of them, as his true and lawful attorneys-in-fact and agents,
with full power of substitution and resubstitution, for him and in his name,
place, and stead, in any and all capacities, to sign any and all amendments to
this Report, and to file the same, with all exhibits thereto, and other
documents in connection therewith, with the Securities and Exchange Commission,
granting unto said attorneys-in-fact and agents, and each of them, full power
and authority to do and perform each and every act and thing requisite and
necessary to be done in connection therewith, as fully to all intents and
purposes as he might or could do in person, hereby ratifying and confirming that
all said attorneys-in-fact and agents, or any of them or their or his substitute
or substitutes, may lawfully do or cause to be done by virtue hereof. Pursuant
to the requirements of the Securities Exchange Act of 1934, this Report has been
signed below by the following persons on behalf of the Registrant and in the
capacities and on the dates indicated.

Pursuant to the requirements of the Securities Exchange Act of 1934, this
Report has been signed below by the following persons on behalf of the
Registrant and in the capacities and on the dates indicated.

<TABLE>
<CAPTION>
SIGNATURE TITLE DATE
--------- ----- ----
<C> <S> <C>
/s/ JOHN C. MARTIN President and Chief Executive
------------------------------------------- Officer, Director (Principal March 29, 2000
John C. Martin Executive Officer)

Vice President, Chief
/s/ SHARON SURREY-BARBARI Financial Officer (Principal
------------------------------------------- Financial and Accounting March 29, 2000
Sharon Surrey-Barbari Officer)

/s/ DONALD H. RUMSFELD
------------------------------------------- Chairman of the Board of March 29, 2000
Donald H. Rumsfeld Directors

/s/ PAUL BERG
------------------------------------------- Director March 29, 2000
Paul Berg
</TABLE>

86
<TABLE>
<CAPTION>
SIGNATURE TITLE DATE
--------- ----- ----
<C> <S> <C>
/s/ ETIENNE F. DAVIGNON
------------------------------------------- Director March 29, 2000
Etienne F. Davignon

/s/ JAMES M. DENNY, SR.
------------------------------------------- Director March 29, 2000
James M. Denny, Sr.

/s/ GORDON E. MOORE
------------------------------------------- Director March 29, 2000
Gordon E. Moore

/s/ GEORGE P. SHULTZ
------------------------------------------- Director March 29, 2000
George P. Shultz
</TABLE>

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