Tenofovir (Viread) Maintains HBV Suppression without Resistance for 4 Years

Viread for Hepatitis B Maintains Antiviral Suppression with No Development of Resistance through Four Years of Treatment

New Long-Term Data Also Show Significant "s" Antigen Loss
in Key Patient Population

Boston -- October 30, 2010 -- Gilead Sciences, Inc. (Nasdaq: GILD) today announced new data from the open-label phase of two pivotal Phase III clinical trials (Studies 102 and 103) evaluating the four-year efficacy of Viread (tenofovir disoproxil fumarate) for the treatment of chronic hepatitis B virus (HBV) infection. Significantly, no resistance to Viread emerged over 192 weeks of treatment, and 10.8 percent of patients receiving Viread in Study 103 (HBeAg-positive) for four years experienced surface, or "s," antigen (HBsAg) loss, which is a marker of the resolution of chronic HBV infection. Additional data from these studies and from Study 106 show the durable antiviral efficacy of Viread among several key patient subpopulations, including patients with high baseline viral levels, individuals of Asian descent and treatment-experienced patients. These findings are being presented at the 61st annual meeting of the American Association for the Study of Liver Diseases (The Liver Meeting 2010) in Boston.

"The complete absence of Viread-related resistance detected among study participants shows that this therapy has a high and durable barrier to viral resistance, which is essential for the long-term success of HBV therapy," said Patrick Marcellin, MD, of Hopital Beaujon in Clichy, France, INSERM CRB3 and University of Paris Denis Diderot, and the principal investigator of Study 102. "These four-year results underscore the long-term benefits of Viread for diverse patient populations, including those who are difficult to treat."

The 192-week data from Studies 102 and 103 evaluate the intent-to-treat population (with the exception of those who left the study for administrative reasons). In Studies 102 and 103, the majority of patients who received Viread for up to 192 weeks experienced sustained suppression of HBV DNA levels in the blood below 400 copies/mL and normalization of alanine aminotransferase (ALT, an enzyme that serves as a measure of liver damage). Notably, no HBV pol/RT amino acid substitutions associated with tenofovir resistance were detected through 192 weeks of Viread.

Among HBeAg-positive patients, 29 percent (based on observed data at week 192) experienced "e" antigen seroconversion, which is defined as both the disappearance of the hepatitis B "e" antigen, a marker of HBV replication (rendering the patient "HBe-antigen negative"), and the appearance of antibodies to this antigen (making the patient "HBe-antibody positive"). Additionally, among HBeAg-positive patients receiving Viread through 192 weeks, the cumulative probability (estimated by Kaplan-Meier) of "s" antigen loss, suggesting that HBV infections may have cleared completely, was 10.8 percent.

"Over the years, physicians have come to understand the critical role of 's' antigen loss in the cessation of disease activity," said Jenny Heathcote, MD, of the University of Toronto, Canada, and the principal investigator for Study 103. "The 10.8 percent 's' loss observed in this trial is a significant finding that makes Viread a highly attractive treatment option for HBV."

Viread for HBV was approved by the U.S. Food and Drug Administration (FDA) in 2008 and has since become the most-prescribed HBV medicine in the United States. It is the only recommended first-line therapy for hepatitis B to demonstrate continuous efficacy and safety through four years in pivotal studies. In October 2010, the FDA expanded Viread's indication to include the treatment of chronic hepatitis B among patients with decompensated liver disease, the end stage of hepatitis B in which liver function is marginal and clinical complications frequently occur. Decompensated liver disease is an indication for consideration of liver transplantation.

Viread Data at The Liver Meeting

Studies 102 and 103 are both multi-center, randomized, double-blind Phase III clinical trials comparing Viread to Hepsera (adefovir dipivoxil) among HBeAg-negative presumed pre-core mutant (Study 102; n=375) and HBeAg-positive (Study 103; n=266) chronic hepatitis B patients with compensated liver disease. Patients had HBV DNA (viral load) above 100,000 copies/mL and elevated levels of ALT upon study initiation. The majority of patients were treatment-naive, although some patients had prior lamivudine treatment experience. Patients originally randomized to Hepsera in both studies rolled over to open-label Viread treatment (n=196) at week 48, while patients originally randomized to Viread continued open-label Viread (n=389). After 72 weeks, patients with confirmed viremia (HBV DNA levels at or above 400 copies/mL on two consecutive visits) had the option of adding emtricitabine treatment by substituting Truvada (emtricitabine and tenofovir disoproxil fumarate) for Viread. The number of patients entering year four was 218 (Study 102) and 130 (Study 103) for those originally randomized to receive Viread and 109 (Study 102) and 71 (Study 103) for those originally randomized to receive Hepsera.

Overall Efficacy and Safety at Week 192 (Abstracts 476 and 477)

In an on-treatment analysis, 99 percent of patients in Study 102 and 96 percent of patients in Study 103 who were originally randomized to receive Viread through 192 weeks achieved viral suppression below 400 copies/mL. Among those who were originally randomized to receive Hepsera, 100 percent of patients in Study 102 and 99 percent of patients in Study 103 achieved viral suppression below 400 copies/mL. In an analysis in which the addition of emtricitabine equals failure, 84 percent and 68 percent of patients (Studies 102 and 103, respectively) originally randomized to receive Viread and 87 percent and 72 percent of patients (Studies 102 and 103, respectively) originally randomized to receive Hepsera experienced sustained viral suppression. The majority of patients with elevated ALT at baseline achieved normalized ALT on treatment (ranging from 77 percent to 86 percent across both arms in both studies). Viread was well-tolerated in both studies. During the open-label period (week 48 through week 192), seven patients discontinued treatment due to an adverse event. Creatinine levels, an indicator of kidney function, remained stable through 192 weeks.

Patients with High Viral Load (Abstract 137)

In a subgroup analysis pooling data from Studies 102 and 103, 71 percent of patients who entered the trials with high viral levels (HBV DNA of at least 9 log10 copies/mL) (n=129), achieved sustained viral suppression after 192 weeks of Viread treatment. Of 29 patients who opted to add emtricitabine treatment after 72 weeks due to confirmed viremia, 20 had viral suppression at week 192. At week 192, ALT levels were normalized in 77 percent of patients with high viral load at baseline. Among HBeAg-positive patients (n=118) in this group, 35 percent achieved HBeAg loss and 23 percent experienced HBeAg seroconversion. Overall, 15 percent of patients with high viral load experienced HBsAg loss.

Patients of Asian Descent (Abstract 481)

In another subgroup analysis pooling four-year data from Studies 102 and 103, 77 percent of Asian patients achieved sustained viral suppression (163 patients entered the open-label study phase). Of seven Asian patients who added emtricitabine treatment during the study, four of six remaining on study had viral suppression at week 192. ALT levels normalized in 86 percent of Asians after 192 weeks on treatment. Of 65 HBeAg-positive Asian patients with week 192 serology results, 35 percent achieved HBeAg loss and 26 percent experienced HBeAg seroconversion. Viread was well tolerated among this group of patients. During the open-label phase of Viread treatment, serious adverse events occurred in 6 percent of Asian patients, while grade 3-4 laboratory abnormalities occurred in 15 percent. During the study, one Asian patient had a confirmed serum phosphorus level less than 2 mg/dL, which normalized by week 192, and another had a confirmed increase of at least 0.5 mg/dL in serum creatinine.

Treatment-Experienced Patients (Abstract 136)

In Study 106, Viread showed sustained efficacy in patients with prior Hepsera treatment experience through 168 weeks. Patients with an incomplete virologic response after receiving Hepsera for at least six months were randomly assigned to Viread (n=53) or Truvada (n=52). More than half of all patients also had prior treatment experience with lamivudine. Sixteen patients in the Viread arm and nine patients in the Truvada arm remained viremic (HBV DNA greater than 400 copies/mL) after week 24 and initiated open-label Truvada.

The percent of patients achieving viral suppression (HBV DNA below 400 copies/mL) through 168 weeks was the same in both arms of the study at 82 percent. Additionally, 100 percent of patients with baseline resistance mutations to lamivudine (13/13 patients) and 90 percent of patients with baseline resistance mutations to adefovir (9/10 patients) achieved viral suppression. ALT normalization occurred in 68 percent of Viread and 67 percent of Truvada patients. Both Viread and Truvada were well tolerated, and no unexpected or clinically important adverse events related to renal function were reported among these treatment-experienced patients. Notably, no patient experienced a confirmed increase of at least 0.5 mg/dL in serum creatinine, calculated creatinine clearance less than 50 mL/min or serum phosphorus less than 2.0 mg/dL.

Investigator affiliations:

Marcellin study: Gilead Sciences, Durham, NC; Hopital Beaujon, University of Paris, Clichy, France; Servicio de Medicina Interna Hepatologia, Hospital General Universitari Vall d'Hebron and Ciberehd, Barcelona, Spain; University Hospital St. Ivan Rilsky, Sofia, Bulgaria; University of Uludag, Bursa, Turkey; St. Louis University School of Medicine, St. Louis, MO; Mount Sinai School of Medicine, New York , NY; Royal Free Hospital, London, UK; University of Toronto, Toronto, Ontario, Canada.

Heathcote study: University of Toronto, Toronto, Ontario, Canada; Middlemore Hospital, Auckland, New Zealand; Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands; New York Hospital at Queens, Flushing, NY; Storr Liver Unit, Westmead Hospital and University of Sydney, Sydney, NSW, Australia; Hawaii Medical Center East, Honolulu, HI; Hopital Beaujon, University of Paris, Clichy, France; Gilead Sciences, Durham, NC.

Gordon study: Henry Ford Medical Center, Detroit, MI; Hopital Beaujon, University of Paris, Clichy, France; University Hospital, St. Ivan Rilsky, Sofia, Bulgaria; Warsaw Medical University, Warsaw, Poland; Liver Unit Asklepios Klinik St. Georg, Hamburg, Germany; Institute for Clinical and Experimental Medicine, Prague, Czech Republic; Metropolitan Research, Fairfax, VA; University of Toronto, Toronto, Ontario, Canada; Gilead Sciences, Durham, NC.

Gane study: Middlemore Hospital, Auckland, New Zealand; University of Calgary, Calgary, Alberta, Canada; Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada; Monash University, Melbourne, Victoria, Australia; San Jose Gastroenterology, San Jose, CA; University of Manitoba Health Science Center, Winnipeg, Manitoba, Canada; Inova Fairfax Hospital, Falls Church, VA; Storr Liver Unit, Westmead Hospital and University of Sydney, Westmead, NSW, Australia; Hopital Beaujon, Clichy, France; Gilead Sciences, Durham, NC.
Snow-Lampart study: Gilead Sciences, Durham , NC; Hospital Beaujon, Service Hepatologie Center Pierre Abrami, Clichy, France; University of Toronto, Toronto Western Research Institute, Toronto, Ontario, Canada.

Berg study: Universitätsklinik Leipzig, Leipzig, Germany; Hopital Beaujon, Clichy, France; Private Practice, Berlin, Germany; Private Practice, San Jose, CA; Private Practice, Flushing, NY; Hospital Universitario de Valme, Sevilla, Spain; Gilead Sciences, Durham, NC.