Shares of hepatitis C (HCV) drug developer Idenix Pharmaceuticals (NASDAQ:IDIX) have fallen slightly this week after it released mildly interesting clinical trial results for its lead drug candidate.

The results were from a phase 2 study of its lead hepatitis C drug candidate, valopicitabine. The 117-person three-arm clinical trial in HCV genotype-1 infected patients tested valopicitabine against the current standard of care for treating HCV, which is pegylated interferon and ribavirin. Valopicitabine was also tested in combination with the standard of care.

Since the study was so small it's hard to draw conclusions from it unless one treatment were to perform much better or worse than the others. At 36 days the best results were seen in patients taking valopicitabine plus the standard of care. Those patients performed more than twice as well as patients who received the standard of care without valopicitabine added.

At 12 weeks 72% of patients receiving the Idenix drug in combination treatment were HCV negative compared to 62% of those just on standard of care. The downside for Idenix is that patients in the third arm of the study who received just valopicitabine and ribavirin didn't perform so well. For the 12-week data Idenix didn't even release the results for this patient group in the press release. Only 44% of patients from this valopicitabine and ribavirin patient group were HCV negative so Idenix plans on only testing the drug in triple combination treatment with pegylated interferon and ribavirin going forward.

Since this was only a small phase 2 study there is much more that can be learned about valopicitabine in future studies. Idenix and partner Novartis (NYSE:NVS) are planning another 12-week phase 2 study to shed further light on the potential for valopicitabine. The pressure is on Idenix to produce strong results with valopicitabine since there are multiple other exciting HCV treatments in development. Notable competitors include ViroPharma's (NASDAQ:VPHM) HCV-796, InterMune's (NASDAQ:ITMN) ITMN-191, and Vertex Pharmaceuticals' (NASDAQ:VRTX) telaprevir.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy.