Gilead Announces 100 Percent Sustained Virologic Response Rate (SVR4) for an Interferon-Free Regimen of Sofosbuvir (GS-7977), GS

  Gilead Announces 100 Percent Sustained Virologic Response Rate (SVR4) for an
  Interferon-Free Regimen of Sofosbuvir (GS-7977), GS-5885 and Ribavirin in
  Treatment-Naïve Genotype 1 Hepatitis C Infected Patients

- Phase 3 Study with a Fixed-Dose Combination Tablet of Sofosbuvir and GS-5885
                                Now Underway -

Business Wire

BOSTON -- November 10, 2012

Gilead Sciences (Nasdaq: GILD) today announced interim data from the ongoing
Phase 2 ELECTRON study examining a 12-week course of therapy with the
investigational nucleotide sofosbuvir (formerly referred to as GS-7977), the
NS5A inhibitor GS-5885 and ribavirin in patients with genotype 1 chronic
hepatitis C virus (HCV) infection. Among treatment-naïve patients receiving
this combination, 100 percent (n=25/25) remained HCV RNA undetectable four
weeks after completing therapy (SVR4). These data will be presented on
Tuesday, November 13^th at the 63rd annual meeting of the American Association
for the Study of Liver Diseases (The Liver Meeting 2012) in Boston.

“These results indicate that adding GS-5885 to sofosbuvir-based regimens may
enhance SVR rates, potentially offering HCV genotype 1 infected patients a
convenient 12-week course of oral therapy,” said Professor Edward Gane, MD,
Deputy Director and Hepatologist, New Zealand Liver Transplant Unit, Auckland
City Hospital in New Zealand, and principal investigator of the ELECTRON
study. “Along with other data from the ELECTRON study, these results add to
the growing body of evidence supporting the potential for effective
sofosbuvir-based all-oral regimens.”

Gilead recently initiated the first Phase 3 trial (ION-I) evaluating a
fixed-dose combination of sofosbuvir and GS-5885 in treatment-naïve genotype 1
patients. This four-arm study is evaluating the fixed-dose combination with
and without ribavirin for 12-and 24-week durations in 800 patients, 20 percent
of whom have evidence of cirrhosis.

Data from five additional arms of the ELECTRON study examining
sofosbuvir-based therapy in various patient populations also will be
presented:

                                                         
Treatment                   Population                     Results
                            GT 1 treatment-naïve           84% (21/25)
                                                               SVR12
Sofosbuvir + ribavirin        GT 1 null responders           10% (1/10)
for 12 weeks                                                   SVR12
                            GT 2/3 treatment-experienced   68% (17/25)
                                                               SVR12
Sofosbuvir + ribavirin      GT 2/3 treatment-naïve         64% (16/25)
for 8 weeks                                                    SVR12
Sofosbuvir + ribavirin      GT 2/3 treatment-naïve         60% (6/10) SVR8
(800 mg) for 12 weeks
                                                            

Preliminary data from a subset of an ongoing cohort in the ELECTRON study in
which nine genotype 1 previous null responders were treated with sofosbuvir,
GS-5885 and ribavirin for 12 weeks also will be presented on Tuesday. Thus
far, three of the nine patients have reached the four-week post-treatment time
point and all three remain HCV negative.

Both sofosbuvir in combination with ribavirin and sofosbuvir in combination
with GS-5885 and ribavirin were well tolerated in the ELECTRON study. In the
sofosbuvir combined with GS-5885 and ribavirin groups, there was one
discontinuation due to an adverse event unrelated to study drugs. Despite
stopping therapy at week 8, this patient also achieved SVR4.

The most common adverse events were headache, fatigue, upper respiratory tract
infection and nausea. The most common clinically significant grade 3/4
laboratory abnormality was a hemoglobin reduction.

Additional Safety Data for GS-5885

In a poster presentation at The Liver Meeting on Sunday, November 11^th,
investigators will report combined safety data for more than 1,000 patients
who have received at least one dose of GS-5885, in combination with other HCV
medicines, in six ongoing Phase 2 clinical trials. In this analysis, 616
patients received a 30 mg dose and 423 patients received the 90 mg dose of
GS-5885, which is being assessed in Phase 3 research. More than 700 patients
completed at least 12 weeks of treatment with GS-5885. Approximately 70
percent of patients were treatment-naïve and 70 percent had HCV genotype 1a
infection.

Researchers concluded that GS-5885 is safe and well tolerated. No laboratory
abnormalities or other safety signal of concern has been observed in the
GS-5885 development program.

Sofosbuvir and GS-5885 are investigational products and their safety and
efficacy have not yet been established.

About Gilead Sciences

Gilead Sciences is a biopharmaceutical company that discovers, develops and
commercializes innovative therapeutics in areas of unmet medical need. The
company’s mission is to advance the care of patients suffering from
life-threatening diseases worldwide. Headquartered in Foster City, California,
Gilead has operations in North America, Europe and Asia Pacific.

Forward-Looking Statement

This press release includes forward-looking statements within the meaning of
the Private Securities Litigation Reform Act of 1995 that are subject to
risks, uncertainties and other factors, including the possibility that the
proportion of patients who maintain a sustained virologic response 12 weeks
post-treatment will not be as favorable as the sustained virologic response
rates reported in this press release, the possibility that results from the
arm of the ELECTRON study evaluating the efficacy and safety of sofosbuvir,
GS-5885 and ribavirin in genotype 1 previous null responder patients will not
be favorable once four and 12 week post-treatment data from all nine patients
are available and the possibility of unfavorable results from additional arms
of the ELECTRON study and subsequent clinical trials involving sofosbuvir and
GS-5885 with and without ribavirin. As a result, sofosbuvir and GS-5885 as
single agents or as a fixed-dose combination may never be successfully
commercialized. Further, Gilead may make a strategic decision to discontinue
development of the compounds or the fixed-dose combination regimen if, for
example, Gilead believes commercialization will be difficult relative to other
opportunities in its pipeline. These risks, uncertainties and other factors
could cause actual results to differ materially from those referred to in the
forward-looking statements. The reader is cautioned not to rely on these
forward-looking statements. These and other risks are described in detail in
Gilead’s Annual Report on Form 10-K for the quarter ended September 30, 2012,
as filed with the U.S. Securities and Exchange Commission. All forward-looking
statements are based on information currently available to Gilead, and Gilead
assumes no obligation to update any such forward-looking statements.

For more information on Gilead Sciences, please visit the company’s website at
  www.gilead.com, follow Gilead on Twitter (@GileadSciences) or call Gilead
             Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

Contact:

Gilead Sciences, Inc.
Patrick O’Brien, 650-522-1936
Investors
or
Cara Miller, 650-522-1616
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