Shares of Achillion Pharmaceuticals Inc. (ACHN) tanked 22 percent in after-hours trade on Monday, as the U.S. Food and Drug Administration placed on clinical hold its hepatitis C drug, sovaprevir, following elevated liver enzymes during a Phase 1 drug-drug interaction study with ritonavir-boosted atazanavir.
Meanwhile, the FDA has allowed on 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.
In the Phase 1 drug-drug interaction study that evaluated the effects of concomitant administration of sovaprevir with ritonavir-boosted atazanavir, Achillion found unexpected elevations in ALT liver enzymes in multiple subjects and notified the FDA.
"Preliminary pharmacokinetic results indicate a metabolic interaction whereby plasma concentrations of both atazanavir and sovaprevir were substantially increased upon co-administration," the company said. Such elevations were not seen in any other drug-drug interaction studies completed with sovaprevir, the company noted.
The FDA has asked for study reports from two drug-drug interaction studies and an integrated safety analysis of on-going sovaprevir trials, each of which Achillion expects to provide within six weeks.
As for the ongoing -007 Phase 2 clinical trial, Achillion is treating patients in the first segment and plans to release interim trial results in the third and fourth quarters.
Hepatitis C is an infectious disease affecting mainly the liver, caused by the hepatitis C virus. The disease is spread mainly by blood-to-blood contact associated with intravenous drug use, poorly sterilized medical equipment and transfusions. It is estimated that over 170 million people are infected with HCV worldwide.
Sovaprevir is a potent inhibitor of HCV NS3 protease which has the potential to be a best-in-class protease inhibitor for the treatment of chronic HCV infection.
Achillon closed Monday at $8.36, up 2.20%, on a volume of 851 thousand shares. In after hours, the stock dropped $1.88 or 22.49% at $6.48.
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