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Basel, Switzerland and Princeton, NJ, 25 April 2009

Roche and Pharmasset Initiate Phase IIb Clinical Trial of R7128, Most Advanced Nucleoside Polymerase Inhibitor in Development for Chronic Hepatitis C

Triggering $10 million milestone payment to Pharmasset

Roche and Pharmasset, Inc. (Nasdaq: VRUS) today announced that the first patient has been dosed in a Phase IIb study of R7128, the most advanced nucleoside polymerase inhibitor in development for the treatment of chronic hepatitis C. The trial will evaluate the dose and duration of treatment of R7128 in combination with current standard of care – Roche’s PEGASYS® (peginterferon alfa-2a) and COPEGUS® (ribavirin) – in HCV patients who have not been treated previously. The goal of adding R7128 to the existing standard therapy is to improve rates of sustained virological response (SVR), widely equated to a cure, and to shorten the length of treatment for patients.

R7128 is being developed by Roche and Pharmasset under a partnership agreement entered into in 2004. The first patient dosed in this study triggered a $10 million payment to Pharmasset from Roche.

A Phase I/IIa trial demonstrated the ability of R7128 to generate high rapid virologic response rates (RVR) in combination with Pegasys and Copegus. Unlike protease inhibitors in development, R7128 is active against multiple HCV genotypes and presents a high barrier to the development of resistance.

“We look for the Phase IIb study to further support the efficacy and safety of R7128, and nucleoside polymerase inhibitors as a class,” said Michelle Berrey, MD, MPH, Pharmasset’s Chief Medical Officer. “We believe nucleoside inhibitors have a number of advantages over other classes of HCV drugs, including a higher barrier to resistance and activity across multiple genotypes, as well as a high level of potency.”

“The collaboration with Pharmasset underscores Roche’s commitment to develop new therapies that will meet the needs of a growing population of patients with hepatitis C,” said Rob Mitchell, Global Head of Roche’s Virology business. “We are hopeful that a combination of R7128 and the current gold standard of PEGASYS and COPEGUS can provide a more potent – and potentially shorter – treatment regimen.”

About the Phase IIb Trial

The Phase IIb trial is anticipated to enroll about 400 HCV-infected patients with genotypes 1 or 4 who have not been treated previously. It is being conducted in North America, Europe and Australia.

The primary efficacy endpoint of the trial will be the proportion of patients who achieve an SVR, defined as undetectable levels of HCV (measured by Roche TaqMan assay) 24 weeks after completion of treatment. Patients will be enrolled into one of 5 arms:

  • 24 weeks of total treatment, with R7128 500mg bid in combination with PEGASYS and COPEGUS for 12 weeks, followed by 12 weeks of PEGASYS and COPEGUS (“12+12”)
  • 24 weeks of total treatment, with R7128 1000mg bid in combination with PEGASYS and COPEGUS for 12 weeks, followed by 12 weeks of PEGASYS and COPEGUS (“12+12”)
  • 24 weeks of total treatment, with R7128 1000mg bid in combination with PEGASYS and COPEGUS for 8 weeks, followed by a further 16 weeks of PEGASYS and COPEGUS (“8+16”)
  • 48 weeks of total treatment, with R7128 1000mg bid in combination with PEGASYS and COPEGUS for 12 weeks, followed by a further 36 weeks of PEGASYS and COPEGUS (“12+36”)
  • A control arm with PEGASYS and COPEGUS for 48 weeks.  

Patients in the 24-week arms will discontinue all treatment at week 24 if they have achieved a rapid virological response (RVR), defined as undetectable levels of HCV at week 4 (a strategy known as “RVR-guided” treatment), and maintain undetectable levels of HCV until week 22. Patients who do not achieve an RVR at week 4 will continue on the standard of care until week 48.

According to the study design, 100 patients will be initially enrolled, equally across all five arms. The remaining 300 will be enrolled following a review of the 12-week data by the data safety monitoring board.

More About R7128

R7128, a cytidine nucleoside analog inhibitor, is being developed for the treatment of chronic HCV infection. R7128 has shown in vitro activity against all of the most common HCV genotypes.

  • In a 4-week Phase I combination study conducted in 81 treatment-naive patients with chronic HCV, R7128 demonstrated significant short-term antiviral activity with safety and tolerability comparable to placebo with standard of care. Up to 88% of patients achieved undetectable levels of HCV (<15 IU/ml) after only 4 weeks of treatment with R7128 1000mg bid and the standard of care, compared to 18.75% treated with the standard of care alone.
  • In a harder to treat population of genotype 2 or 3 patients who hadn’t responded to previous therapy, results with R7127 1500 mg twice-daily in combination with the standard of care showed that 90% of patients achieved undetectable levels of HCV(<15 IU/ml) after 4 weeks, compared to 60% in the standard of care arm.

In November 2008, Roche, Pharmasset and InterMune initiated the INFORM-1 trial to investigate the combination of R7128 with InterMune’s R7227, a protease inhibitor, in HCV patients. This is the first-ever clinical study to investigate the combination of two oral antiviral medicines in the absence of weekly injections of interferon, or ribavirin. Interim results of this trial will be presented this weekend at the European Association of Liver Disease (EASL) meeting being held in Copenhagen, Denmark.

About Hepatitis C

The hepatitis C virus (HCV) is transmitted primarily through blood or blood products. HCV chronically affects 180 million people worldwide, which makes it over four times more prevalent than HIV.1,2It is a leading cause of cirrhosis, liver cancer and liver failure.

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 on the development of oral therapeutics for the treatment of hepatitis C virus (HCV) and human immunodeficiency virus (HIV). Pharmasset is currently developing three product candidates. R7128, an oral treatment for chronic HCV infection, has completed a 4-week clinical trial in combination with PEGASYS plus COPEGUS through a strategic collaboration with Roche, and is initiating a Phase 2b trial. Racivir, which is being developed for the treatment of HIV in combination with other approved HIV drugs, has completed a Phase 2 clinical trial. PSI-7851, an unpartnered second generation HCV nucleotide analogue recently entered phase 1 studies.

Pharmasset Forward-Looking Statements

Pharmasset "Safe Harbor" Statement under the Private Securities Litigation Reform Act of 1995: Statements in this press release regarding our business that are not historical facts are "forward-looking statements" that involve risks and uncertainties, including without limitation, the risk that adverse events could cause the 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 these risks and uncertainties, any of which could cause our actual results to differ from those contained in the forward-looking statements, see the section of our Annual Report on Form 10-K for the fiscal year ended September 30, 2008 and our Quarterly Report on Form 10-Q for the period ended December 31, 2008 filed with the Securities and Exchange Commission entitled "Risk Factors" and discussions of potential risks and uncertainties in our subsequent filings with the Securities and Exchange Commission.

About Roche

Headquartered in Basel, Switzerland, Roche is a leader in research-focused healthcare with combined strengths in pharmaceuticals and diagnostics. Roche is the world’s largest biotech company with truly differentiated medicines in oncology, virology, inflammation, metabolism and CNS. Roche is also the world leader in in-vitro diagnostics, tissue-based cancer diagnostics and a pioneer in diabetes management. Roche’s personalised healthcare strategy aims at providing medicines and diagnostic tools that enable tangible improvements in the health, quality of life and survival of patients.

In 2008, Roche had over 80,000 employees worldwide and invested almost 9 billion Swiss francs in R&D. The Group posted sales of 45.6 billion Swiss francs. Genentech, United States, is a wholly owned member of the Roche Group. Roche has a majority stake in Chugai Pharmaceutical, Japan. For more information: www.roche.com.

All trademarks used or mentioned in this release are protected by law.

1) AIDS Epidemic Update. 2006. (Accessed October 26, 2007, at http://www.who.int/hiv/mediacentre/2006_EpiUpdate_en.pdf.)
2) World Health Organization. Initiative for Vaccine Research, Viral Cancers, Hepatitis C. 2006. (Accessed July 24, 2006, at http://www.who.int/vaccine_research/diseases/viral_cancers/en/index2.html.)