Acura Pharmaceuticals Inc said the U.S. Food and Drug Administration (FDA) indicated that the company may have to conduct an additional study to determine the abuse-deterrent capability of its experimental painkiller treatment.
The FDA in May said data was insufficient to support the company's claim that the drug could not be abused by snorting.
The company said on Friday it would review data from a previous trial to determine whether to proceed with an additional clinical study.
Acura's drug, which contains common painkillers hydrocodone bitartrate and acetaminophen, is designed to cause a burning sensation when snorted or form a gelatinous mixture when dissolved for injecting.
The drug failed in a mid-stage trial to show statistically significant results in reducing likability among abusers by snorting compared with the generic hydrocodone/acetaminophen tablet.
The FDA in December 2013 agreed to review the results of the failed mid-stage trial.
Up to Thursday's close of 86.5 cents, Acura's stock had nearly halved in value this year.
(Reporting by Anand Basu in Bangalore; Editing by Sriraj Kalluvila)