Idenix drops after FDA loosens one hold but slaps on another

Just as regulators decided to change a full clinical hold on Idenix's lead hepatitis C drug to a partial hold, paving the way to a combo drug trial later this year, the FDA slapped a new clinical hold on an HIV therapy the biotech had licensed to GlaxoSmithKline, jeopardizing $390 million in milestones. And the biotech killed a second hep C program after concluding that the drug was linked to instances of liver toxicity which had prompted the original hold.

Confronted by the company's ($IDIX) swaying fortunes, investors quickly ducked, trimming 25 percent off of Idenix's share price.  

The fresh bout of bad news was generated by GSK2248761, which GSK had licensed, spawning payments of $60.5 million for the Cambridge, MA-based developer. But Idenix still has a potential $390 million to collect on the drug--a non-nucleoside reverse transcriptase inhibitor. Idenix did not detail what prompted the hold, noting only that it had been told of the action by GSK's ViiV Healthcare.

On a brighter note, Idenix will now be able to push ahead with a Phase IIb 12-week hepatitis C trial of IDX184 in combination with pegylated interferon and ribavirin in the second half of 2011. The clinical hold was issued in September 2010 as a result of three cases of elevated liver function tests observed during a drug-drug interaction study of the combination of IDX184 and IDX320, an HCV protease inhibitor, in healthy volunteers. Researchers subsequently concluded that IDX320 was the culprit and the developer has now stopped work on that drug.

- here's the release from Idenix