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Pharmasset Initiates First Time in Human Study of PSI-938 for the Treatment of Hepatitis C: unique new HCV drug, nucleotide
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PRINCETON, N.J., April 8, 2010 Pharmasset, Inc. (Nasdaq: VRUS) announced today that dosing has initiated in a phase 1, single ascending dose (SAD) study in healthy volunteers with PSI-938, a third generation purine nucleotide analog polymerase inhibitor of hepatitis C virus (HCV). Pharmasset recently filed an Investigational New Drug Application (IND) with the Food and Drug Administration (FDA).
"PSI-938 is our first purine nucleotide analog to move into clinical development," stated Dr. Michelle Berrey, Pharmasset's Chief Medical Officer. "As PSI-938's resistance profile is different from other nucleoside/tides in development for HCV and it has a different metabolic pathway from pyrimidine analogs, such as RG7128 and PSI-7977, we believe PSI-938 could be potentially combined with other nucleosides in development to deliver a pan-genotype regimen. We look forward to reporting the first antiviral data with PSI-938 in the third quarter of 2010."
Purine and Pyrimidine Analogs
Purine nucleoside/tide analogs have many of the benefits of pyrimidine nucleoside/tide analogs, such as RG7128 and PSI-7977, in that they have demonstrated in vitro activity across multiple HCV genotypes, have a higher barrier to resistance than other classes of HCV small molecules in development, and have a lower risk of drug interactions when combined with other direct acting antivirals targeting HCV. In addition, Pharmasset's purine analogs retain activity against the S282T mutation associated with in vitro resistance in other nucleoside/tide analogs in development, and are metabolized to the active triphosphate form through a different phosphorylation pathway than the pyrimidine analogs. Given these characteristics, Pharmasset's purine and pyrimidine analogs have the potential to be combined as part of a future treatment regimen.
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, secondarily, on the development of Racivir(TM) for the treatment of human immunodeficiency virus (HIV). 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 three clinical-stage product candidates. RG7128, a nucleoside analog for chronic HCV infection, is in two Phase 2b clinical trials in combination with Pegasys(R) plus Copegus(R) and is also in the INFORM studies, the first series of studies designed to assess the potential of combinations of small molecules without Pegasys(R) and Copegus(R) to treat chronic HCV. These clinical studies are being conducted through a strategic collaboration with Roche. Our other clinical stage candidates include PSI-7977, an isomer of PSI-7851 and an unpartnered, next-generation HCV nucleotide analog that is in a Phase 2a trial, and the third-generation purine analog PSI-938 in Phase 1. Racivir, for the treatment of HIV, has completed a Phase 2 clinical trial. We also have in our pipeline an additional purine nucleotide analog, PSI-661, an isomer of PSI-879 in advanced preclinical development.
Pegasys(R) and Copegus(R) are registered trademarks of Roche.
Contact
Richard E. T. Smith, Ph.D.
VP, Investor Relations and Corporate Communications
Office: +1 (609) 613-4181
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