Company Collaboration to Test BMS-790052 + PSI-7977 Combo for Hepatitis C

	SUMMARY: Bristol-Myers Squibb and Pharmasset recently announced that they will collaborate to conduct clinical testing of a combination direct-acting hepatitis C treatment regimen consisting of the HCV NS5A inhibitor BMS-790052 plus the nucleotide HCV polymerase inhibitor PSI-7977. The companies will test all-oral regimens with and without ribavirin in previously untreated patients.

Bristol-Myers Squibb and Pharmasset Enter into a Clinical Collaboration Agreement for Proof of Concept Combination Study in Patients Chronically Infected with Hepatitis C

	Study is the first cross-company collaboration combining two oral, direct-acting antivirals
	Study to evaluate the combination with and without ribavirin in treatment-naive patients

New York, N.Y. and Princeton, N.J. -- January 10, 2011 -- Bristol-Myers Squibb Company (NYSE:BMY) and Pharmasset (NASDAQ: VRUS) announced today that the companies have entered into a clinical collaboration agreement to evaluate the utility of BMS-790052, Bristol-Myers Squibb's NS5A replication complex inhibitor, in combination with PSI-7977, Pharmasset's nucleotide polymerase inhibitor, for the treatment of chronic hepatitis C virus (HCV).

This proof of concept study will evaluate the potential to achieve sustained viral response 24 weeks post treatment with an oral, once-daily treatment regimen in patients across HCV genotypes. Specifically, the study will assess the safety, pharmacokinetics and pharmacodynamics of BMS-790052 in combination with PSI-7977, with and without ribavirin, in treatment-naive patients chronically infected with HCV genotypes 1, 2, and 3. The study is planned to start in the first half of 2011. This collaboration represents the first cross-company collaboration combining two oral agents to address a significant unmet medical need in the treatment of HCV.

"Bristol-Myers Squibb is committed to the goal of helping patients prevail over hepatitis C by investigating multiple therapeutic platforms," said Brian Daniels, senior vice president, Development. "We are pleased to partner with Pharmasset on this important study to advance the scientific understanding of the potential for an all-oral regimen to treat hepatitis C. Conducting this study highlights Bristol-Myers Squibb's ability to collaborate with other companies to develop innovative combination therapies in areas of high unmet need."

"We are excited to be working with Bristol-Myers Squibb and to be investigating PSI-7977 with a different class of direct acting antivirals," stated Michelle Berrey, MD, MPH, Chief Medical Officer. "This collaboration represents one of many approaches we are pursuing with our portfolio of nucleoside/tide analogs that include both interferon free and interferon-sparing regimens. We believe the development of an all oral treatment regimen represents an important evolution in the treatment of HCV."

About BMS-790052

BMS-790052 is an investigational oral hepatitis C NS5A replication complex inhibitor. NS5A is one of the essential components for HCV replication. BMS-790052 is one of several molecules Bristol-Myers Squibb is studying for the potential treatment of chronic hepatitis C. The portfolio of investigational compounds, which also includes a novel pegylated interferon lambda, fits into the company's overall R&D focus on diseases where there is major unmet medical need.

About PSI-7977

PSI-7977 is a uracil nucleotide analog inhibitor of the NS5B polymerase being developed for the treatment of chronic HCV infection. Nucleotide analog polymerase inhibitors work by acting as alternative substrates that block the synthesis of HCV RNA, which is essential for the virus to replicate. PSI-7977 has been studied in combination with peginterferon and ribavirin for up to 12 weeks in genotype 1, 2 or 3 patients and is currently in two Phase 2b studies, one of which is investigating an interferon sparing regimen in genotype 2 or 3 patients. PSI-7977 is also being investigated in a 14-day combination study with PSI-938, a guanine nucleotide analog.

About Bristol-Myers Squibb

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.

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). Our research and development efforts focus on nucleoside/tide analogs, a class of compounds which act as alternative substrates for the viral polymerase, thus inhibiting viral replication. We currently have four clinical-stage product candidates. RG7128, a cytosine nucleoside analog for chronic HCV infection, is in two Phase 2b clinical studies in combination with Pegasys plus Copegus and is also in the INFORM studies, the first series of studies designed to assess the potential of combinations of small molecules without Pegasys and Copegus to treat chronic HCV. These clinical studies are being conducted through a strategic collaboration with Roche. Our other clinical stage HCV candidates include PSI-7977, an unpartnered uracil nucleotide analog that is in two Phase 2b studies in patients with HCV genotypes 1, 2, or 3, and PSI-938, an unpartnered guanine nucleotide analog which recently completed a 14-day monotherapy study and has recently initiated a 14-day combination study with PSI-7977. We also have in our pipeline an additional purine nucleotide analog, PSI-661, in advanced preclinical development. For more information visit www.pharmasset.com.