>>SOUTH SAN FRANCISCO, Calif., Nov. 12 /PRNewswire-FirstCall/ -- Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL - News) today announced that it has initiated an escalating single dose safety trial of R803, an experimental drug to treat the hepatitis C virus (HCV). The goal of this trial is to establish the safety and pharmacokinetics of R803. Results of this trial are expected in January 2004, and, if successful, will allow Rigel to enter into phase I/II efficacy trials in the United States in the first half of 2004.
R803, Rigel's oral, small-molecule, anti-HCV compound, is a non-nucleoside HCV polymerase inhibitor. Based on preclinical data, Rigel believes that R803 is potent, selective, rapidly inhibits viral replication and is active against all genotypes of HCV. Moreover, as a result of R803's unique viral binding site, resistance may be slow to develop. R803 is extremely potent at inhibiting viral replication, with an EC(50) (the concentration of the drug necessary to produce a 50% inhibition of viral replication) in the low nanomolar range, as assessed both in a replicon system and in a live virus assay. Pre-clinical testing completed to date shows no significant adverse effects attributed to R803 at the clinical dose levels. Evaluated across numerous human cell lines, the compound does not appear to interfere with normal cellular functions, including DNA, RNA and protein synthesis, cell signaling and immune cell activation and function. In assays using live virus, R803 appears to act within days to reduce viral levels significantly.
"R803 has shown significant potential as a potent therapeutic agent that rapidly inhibits viral replication," said Dr. Donald G. Payan, Rigel's co-founder and Chief Scientific Officer. "This is one of the first direct hepatitis C anti-virals to enter human clinical trials and, if proven safe and effective, we believe that it could dramatically improve the treatment of this serious disease."<<
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