U.S. health regulators have denied approval to Acurox, a pain drug by Acura Pharmaceuticals Inc (ACUR.O) and King Pharmaceuticals Inc (KG.N).

The FDA has sent a complete response letter to the companies. The letter raises issues regarding potential abuse-deterrent benefits of the drug.

The companies said they expect to respond to the issues raised in the letter, without conducting any additional studies.
The FDA had earlier sent a preliminary review letter to the companies last month. On the basis of the letter, the companies had then said that they don't expect an approval by the June 30 action date.

Acurox includes the powerful pain reliever oxycodone, and contains components designed to thwart prescription drug abuse, which can be common with opioid pain drugs.

Biologic Investment Research analyst Kevin McNamara said: "This is all that Acurox is, its abuse-deterrent. And now there are questions about what FDA thinks about those benefits. It sounds pretty bad."