New 12 Week, Interferon-Free Treatment Arms Added to All-Oral Combination Study of PSI-7977 and Daclatasvir (BMS-790052) for HCV Genotype 1

PRINCETON, N.J., Nov. 4, 2011 /PRNewswire/ -- Pharmasset, Inc. (Nasdaq: VRUS) and Bristol-Myers Squibb Company (NYSE: BMY) announced today the addition of four treatment arms to the ongoing Phase IIa trial evaluating the combination of Pharmasset's PSI-7977, a nucleotide polymerase inhibitor, and Bristol-Myers Squibb Company's daclatasvir (BMS-790052), an investigational NS5A replication complex inhibitor, for the treatment of chronic hepatitis C (HCV).  This trial is the result of a clinical collaboration agreement between Pharmasset and Bristol-Myers Squibb announced in January 2011.

"Recent data from Pharmasset's ELECTRON trial as well as other all-oral DAA combination studies have demonstrated the potential of 12 week treatment regimens," stated William Symonds, Pharmasset's Senior Vice President of Clinical Pharmacology and Translational Medicine. "This study will evaluate whether the potent antiviral activity and high barrier to resistance seen in Phase II studies of PSI-7977 may enable shorter treatment durations with an interferon-free regimen than the current standard of care."

"Hepatitis C is a rapidly evolving field of research.  As the science evolves, we are evolving our clinical development programs to continue to drive advances in HCV research," said Brian Daniels, senior vice president, Development, Bristol-Myers Squibb.  "Shorter duration, all-oral therapy and effective treatment options for patients who have failed approved triple therapy regimens are clear unmet medical needs in HCV.  With this study, we aim to understand the potential for daclatasvir to help address these needs, as part of a novel combination treatment regimen."

About the Trial

This Phase IIa trial completed enrollment in September 2011 with approximately 84 subjects with chronic HCV genotypes 1, 2 or 3 who have not been treated previously. The primary endpoint of the trial is sustained virologic response (SVR). Subjects were randomized equally across each of the following arms:

• PSI-7977 400mg QD for 7 days, then add daclatasvir 60mg QD for a further 23 weeks in genotype 1 subjects;
• PSI-7977 400mg QD for 7 days, then add daclatasvir 60mg QD for a further 23 weeks in genotype 2 or 3 subjects;
• PSI-7977 400mg QD and daclatasvir 60mg QD for 24 weeks in genotype 1 subjects;
• PSI-7977 400mg QD and daclatasvir 60mg QD for 24 weeks in genotype 2 or 3 subjects;
• PSI-7977 400mg QD, daclatasvir 60mg QD and ribavirin for 24 weeks in genotype 1 subjects;
• PSI-7977 400mg QD, daclatasvir 60mg QD and ribavirin for 24 weeks in genotype 2 or 3 subjects.

Four new treatment arms are now being added to the study; two in genotype 1 treatment-naïve subjects and two in subjects who have failed therapy with pegylated interferon and ribavirin in combination with telaprevir or boceprevir. One hundred and twenty patients will be enrolled in the following four arms (2:2:1:1):

• PSI-7977 400mg QD and daclatasvir 60mg QD for 12 weeks in HCV genotype 1 treatment-naïve patients;
• PSI-7977 400mg QD, daclatasvir 60mg QD and ribavirin for 12 weeks in HCV genotype 1 treatment-naive patients;
• PSI-7977 400mg QD and daclatasvir 60mg QD for 12 weeks in genotype 1 HCV patients who have previously failed telaprevir or boceprevir treatment;
• PSI-7977 400mg QD, daclatasvir 60mg QD and ribavirin for 12 weeks in HCV genotype 1 patients who have previously failed telaprevir or boceprevir treatment.

Additional details can be found at www.clinicaltrials.gov.

About Pharmasset

Pharmasset is a clinical-stage pharmaceutical company committed to discovering, developing, and commercializing novel drugs to treat viral infections. Pharmasset's primary focus is the development of oral therapeutics for the treatment of hepatitis C virus (HCV) infection. Our research and development efforts are focused on nucleoside/tide analogs, a class of compounds which act as alternative substrates for the viral polymerase, thus inhibiting viral replication. We currently have three clinical-stage product candidates advancing in trials in various populations. Our pyrimidine, PSI-7977, an unpartnered uracil nucleotide analog, is initiating an interferon-free, Phase III program in patients with HCV genotypes 1, 2 and 3 and continues to be evaluated in five Phase IIb trials in patients with all HCV genotypes. Our purine, PSI-938, an unpartnered guanosine nucleotide analog, is being studied in QUANTUM, a Phase IIb interferon-free trial of PSI-7977 and PSI-938 in subjects with all HCV genotypes. Mericitabine (RG7128) continues in development through a strategic collaboration with Roche.

About Bristol-Myers Squibb

Bristol-Myers Squibb is advancing a portfolio of compounds that aim to address unmet medical needs across the liver disease continuum, including hepatitis C, hepatitis B and liver cancer.  The Company's hepatitis C pipeline includes a portfolio of compounds with different mechanisms of action, pursuing both biologics as well as small molecule antivirals. These compounds are being studied as part of multiple novel treatment regimens with the goal of increasing SVR rates across diverse patient types and geographies.  Discovered by Bristol-Myers Squibb through a genomics approach, daclatasvir, also known as BMS-790052, is the first NS5A replication complex inhibitor to be investigated in hepatitis C clinical trials and is currently in Phase III development.

Bristol-Myers Squibb is a global biopharmaceutical company whose mission is to discover, develop and deliver innovative medicines that help patients prevail over serious diseases.  For more information, please visit http://www.bms.com or follow us on Twitter at http://twitter.com/bmsnews.

Pharmasset Contact:
Richard E. T. Smith, Ph.D.
VP, Investor Relations and Corporate Communications
Office+1 (609) 865-0693

Bristol-Myers Squibb Contacts:
Media:  Jennifer Fron Mauer, 609-252-6579, [email protected]
Investors: John Elicker, 609-252-4611, [email protected]

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Pharmasset "Safe Harbor" Statement under the Private Securities Litigation Reform Act of 1995: Statements in this press release that are not historical facts are "forward-looking statements," that involve risks, uncertainties, and other important factors, including, without limitation, the risk of cessation or delay of any of the ongoing or planned clinical trials and/or our development of our product candidates, the risk that the results of previously conducted studies involving our product candidates will not be repeated or observed in ongoing or future studies involving our product candidates, the risk that our collaboration with Roche will not continue or will not be successful, and the risk that any one or more of our product candidates will not be successfully developed and commercialized. For a discussion of risks, uncertainties, and other important factors, any of which could cause our actual results to differ from those contained in the forward-looking statements, see the section entitled "Risk Factors" in our Annual Report on Form 10-K for the fiscal year ended September 30, 2010 and our Quarterly Reports on Form 10-Q filed with the Securities and Exchange Commission and discussions of potential risks, uncertainties, and other important factors in our subsequent filings with the Securities and Exchange Commission.

Bristol-Myers Squibb Forward-Looking Statement

This press release contains "forward-looking statements" as that term is defined in the Private Securities Litigation Reform Act of 1995, regarding the development and commercialization of pharmaceutical products.  Such forward-looking statements are based on current expectations and involve inherent risks and uncertainties, including factors that could delay, divert or change any of them, and could cause actual outcomes and results to differ materially from current expectations.  No forward-looking statement can be guaranteed.  Among other risks, there can be no guarantee that clinical trials of the compound described in this release will support a regulatory filing, or that the compound will receive regulatory approval or become a commercially successful product. Forward-looking statements in the press release should be evaluated together with the many uncertainties that affect Bristol-Myers Squibb's business, particularly those identified in the cautionary factors discussion in Bristol-Myers Squibb's Annual Report on Form 10-K for the year ended December 31, 2010, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K.  Bristol-Myers Squibb undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events, or otherwise.

SOURCE Pharmasset, Inc.