Vertex Pharmaceuticals Inc. maintains the reasons behind declining sales of HCV drug Incivek telaprevir are due to marketwide factors, including a bolus of clinical trials and a wait-and-see attitude by some physicians. But two doctors contacted by BioCentury said anemia issues specific to Incivek and payer preferences for a competing drug also play a role.

Regardless of the reasons, Incivek's best days could be behind it despite entering the market only 18 months ago. Both Incivek and the competing HCV NS3/4A protease inhibitor - Victrelis boceprevir from Merck & Co. Inc. - face uncertain futures as all oral, interferon (IFN)-free regimens are expected to be approved next year.