US FDA puts clinical hold on Achillion's sovaprevir on safety concerns

USA-based Achillion Pharmaceuticals (Nasdaq: ACHN) announced yesterday (July 1) that the US Food and Drug Administration has put a clinical hold on sovaprevir, the company’s hepatitis C candidate. Shares of Achillion, trading of which was stopped ahead of the news, dropped around 21% to $6.60 in extended trading in moderate volume following the announcement.

The decision was taken after elevations in liver enzymes associated with significantly higher than anticipated exposures to atazanivir and sovaprevir were noted in a Phase I healthy subject drug-drug interaction (DDI) study evaluating the effects of concomitant administration of sovaprevir with ritonavir-boosted atazanavir.

The FDA has allowed continued enrollment and treatment of patients in the Phase II -007 clinical trial evaluating 12-weeks of sovaprevir in combination with ACH-3102 and ribavirin. Achillion said that in a Phase I drug-drug interaction study, it was evaluating the effects of concomitant administration of sovaprevir with ritonavir-boosted atazanavir. While conducting this study, Achillion detected unanticipated elevations in ALT liver enzymes (grade 3 or 4) in multiple subjects, although none of these met the criteria for a serious adverse event (SAE).