Following Phase 1 drug-drug interaction study with ritonavir-boosted atazanavir showing elevated liver enzymes, sovaprevir placed on clinical hold by FDA Ongoing enrollment and treatment of patients remains unaffected in Phase 2 -007 combination trial evaluating 12-weeks of sovaprevir and ACH-3102 for treatment-naive genotype 1 patients Conference call and webcast to be hosted today at 4:15 p.m. EDT NEW HAVEN, Conn., July 1, 2013 (GLOBE NEWSWIRE) -- Achillion Pharmaceuticals, Inc. (Nasdaq:ACHN) today announced that the Company has received notice from the U.S. Food and Drug Administration (FDA) that a clinical hold has been placed on sovaprevir after elevations in liver enzymes associated with significantly higher than anticipated exposures to atazanivir and sovaprevir were noted in a Phase 1 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 2 -007 clinical trial evaluating 12-weeks of sovaprevir in combination with ACH-3102 and ribavirin for patients with treatment-naive genotype 1 hepatitis C viral infection (HCV). In a Phase 1 drug-drug interaction study, Achillion 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). Achillion voluntarily stopped further dosing in the DDI study and promptly notified the FDA of these findings. Preliminary pharmacokinetic results indicate a metabolic interaction whereby plasma concentrations of both atazanavir and sovaprevir were substantially increased upon co-administration. Such ALT elevations have not been seen in the 12-week combination -007 trial, the 12-week combination -005 trial with ACH-3102 and ribavirin, or in any other drug-drug interaction studies completed with sovaprevir to date.