Inhibition of inosine monophosphate dehydrogenase (IMPDH) is one of several proposed mechanisms of action for ribavirin (RBV), a critical component of the current treatment for chronic hepatitis C (CHC). This study was a double-blind, placebo-controlled dose-escalation study of a novel, selective, orally active small molecule inhibitor of IMPDH, merimepodib (VX-497 or MMPD) in combination with standard interferon-alpha (IFN-alpha). Fifty-four treatment-naive patients with genotype-1 CHC were randomized to receive IFN-alpha 3 MIU subcutaneously three times a week, alone or in combination with 100 mg or 300 mg (every 8 h) of MMPD for 4 weeks. At the end of 4 weeks, all patients were offered 48 weeks of treatment with IFN-alpha/RBV. The objectives of the study were to evaluate the tolerability of the IFN-alpha/MMPD combination and to evaluate whether MMPD had an on-treatment effect on HCV-RNA, similar to RBV when added to IFN-alpha. The drug combination was generally well tolerated; one patient at the higher dose discontinued because of elevated alanine aminotransferase levels. No pharmacokinetic interactions were evident between the two drugs. Analysis of covariance that adjusted for a baseline imbalance in HCV-RNA in the intent-to-treat population did not show any significant differences between the treatment groups, or between MMPD plus IFN-alpha compared with IFN-alpha alone. However, the per-protocol primary efficacy analysis based on treatment-compliant patients demonstrated a greater reduction in mean HCV-RNA in the combination of 100 mg MMPD plus IFN-alpha compared with IFN-alpha alone (-1.78 log vs -0.86 log, P=0.037). In conclusion, the addition of a selective IMPDH inhibitor to IFN-alpha was well tolerated. In a low-dose range, the addition of MMPD may have the potential to add to the antiviral efficacy of IFN-alpha. Larger, longer duration trials incorporating pegylated IFN would be required to determine whether this combination, alone or with RBV, would increase either early or sustained virological response rates.
View details for Web of Science ID 000231963400006
View details for PubMedID 16152757