(Reuters) - Achillion Pharmaceuticals Inc said the U.S. Food and Drug Administration decided not to lift a clinical hold it had placed on the firm's hepatitis C drug, sovaprevir, leaving an uncertain fate for the company's most promising drug.
The news caused Achillion's shares to plunge 45 percent in after-market trade on Friday.
The FDA asked the company to halt development of sovaprevir in June, after detecting elevated liver enzymes, an indication of liver damage, in multiple patients who were given the drug in a clinical study.
The regulator asked for some clinical data on the drug, and while Achillion submitted that, the agency concluded that removal of the clinical hold was not warranted, Achillion said in a statement on Friday.
"While we are disappointed that we were not able to resolve the clinical hold at this time despite having addressed all the issues, we believe the breadth of our portfolio allows us to quickly advance other all-oral combination regimens for the treatment of HCV," Achillion's Chief Executive Milind Deshpande stated.
Achillion is among a number of drugmakers developing a new class of drugs to treat the liver-hampering virus by using a drug regimen that does not include the conventional hepatitis C drug constituent, interferon, which causes flu-like symptoms.
However, multiple drugmakers have suffered regulatory and development setbacks over the past year.
Most recently in July, Vertex Pharmaceuticals Inc, which already sells the market-leading hepatitis C treatment Incivek, said U.S. health regulators placed a partial clinical hold on a mid-stage study of its experimental oral hepatitis C treatment, VX-135, because of potential liver problems.
Vertex said it is working with the agency to resolve issues.
Achillion on Friday also reported interim results from an ongoing mid-stage clinical trial testing a combination of its experimental drugs, including sovaprevir.
Initial data from this mid-stage study showed that 79 percent of patients with the most common and difficult to treat genotype 1 form of hepatitis C achieved rapid virologic response, or undetectable virus levels after four weeks of treatment.
Trading in Achillion's shares was halted at 1643 ET on Friday, pending release of the news. After resumption, Achillion's shares hit a low of $3.95 in extended trade.
Reporting by Zeba Siddiqui in Bangalore; Editing by Ken Wills