VX-497, or merimempodib, produced by Vertex Pharmaceuticals, is an inosine monophosphate dehydrogenase (IMPDH)
inhibitor, now in phase II clinical trials for the treatment of HCV infection. Blocking IMPDH function prevents viruses from duplicating themselves within host cells.
A randomized study of VX-497 alone in 30 HCV-infected non-responders to IFN monotherapy resulted in decreased
liver inflammation and ALT levels. Present phase II studies will look at the effects of longer treatment, especially
in non-responders. According to laboratory studies comparing the efficacy of VX-497 to that of ribavirin, the company
believes it may be as effective as ribavirin. Studies combining the product with pegylated interferon are being planned for 2001 (
Phase II studies combining the product with ribavirin and pegylated interferon in genotype 1 patients are in progress.
At six months, merimempodib met its primary endpoint of safety and tolerability, and showed a statistically significant
antiviral response in the patients involved in the study (up to 86% of patients receiving higher doses). (