Idenix Pharmaceuticals announced this morning that FDA had placed a clinical hold on its Phase II valopicitabine hepatitis C polymerase inhibitor.
Valopicitabine, previously dubbed NM283, was the furthest-along HCV polymerase inhibitor in clinical development and the first of a next-generation set of targeted HCV therapies. The polymerase class hasn't received as much attention as HCV protease inhibitors, which have been the subject of some pretty sizeable deals--Vertex's alliance with Johnson & Johnson and Intermune's alliance with Roche, for example. But Idenix had maintained that the future of HCV antiviral therapy would be combination, a sentiment shared by many, and so pushed ahead with development despite only moderate clinical success with the compound.
The biotech's partner Novartis must have agreed; the companies have a broad alliance whereby Novartis gets first right of refusal on any Idenix compound when it hits Phase II. For valopicitabine, Novartis had to pony up more than half a billion dollars to maintain its share of the drug. Novartis owns upwards of 57% of Idenix.
Today's news is the second clinical hold placed on a Novartis-in-licensed HCV candidate this year. Last summer FDA halted trials of Anadys' ANA975 drug, a TLR-7 agonist in Phase Ib, after a preclinical toxicology study unearthed a potential safety signal.
HCV dealmaking has definitely been a hot space, and will likely continue to be so despite this spate of clinical difficulties. For our roundup of drugs in development for HCV, see this late-2005 IN VIVO story.
UPDATE: Idenix shares are off about two bucks, or 35%, at about 11:30a.