Pharmasset Commences Dosing in Phase 3 Registration Studies of Clevudi...(s 301 and 302. Twelve weeks after comple...),Health

Clevudine was generally safe and well-tolerated by patients with chronic HBV. Serious adverse events during treatment in Studies 301 and 302 and during follow-up indicated that a higher percentage of placebo-treated patients had seriously elevated liver enzyme levels. Otherwise, there was no meaningful difference between clevudine and placebo in the incidence of serious adverse events.

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 B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV).

Pharmasset is currently developing three product candidates. Clevudine, for the treatment of chronic HBV infection, is in Phase 3 clinical trials for registration in the Americas and Europe. Clevudine is already approved for HBV in South Korea and marketed by Bukwang Pharmaceuticals in South Korea under the brand name Levovir. R7128, an oral treatment for chronic HCV infection, is in a Phase 1 clinical trial through a strategic collaboration with Roche. Racivir, which is being developed for the treatment of HIV in combination with other approved HIV drugs, has completed a Phase 2 clinical trial.

Hepsera is a registered trademark of Gilead Sciences, Inc.

Contact

Alan Roemer, Vice President

Investor Relations & Corporate Communications

alan.roemer@pharmasset.com

Office: (609) 613-4125

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-looki
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