* FDA issues complete response letter to the two cos
* Raises questions on the drug's abuse-deterrent properties
* Cos believe can address issues without additional trials
* Acura shares fall as much as 15 pct, King down 3 pct (Adds analyst comments; updates stock movement)
By Esha Dey
BANGALORE, July 2 (Reuters) - Acura Pharmaceuticals Inc ACUR.O and King Pharmaceuticals Inc KG.N said U.S. health regulators denied approval of their pain drug, Acurox, and raised questions on the potential abuse-deterrent benefits of the drug.
The companies, which were issued a complete response letter by the U.S. Food and Drug Administration, said they expect to respond to the issues raised in the letter without conducting any additional studies.
"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," Biologic Investment Research analyst Kevin McNamara said.
McNamara, who has a "sell" rating on the stock, said it is highly unlikely that the drug might even get approved as a branded generic form of oxycodone.
Late last month, Acura had received a preliminary review letter from FDA, and said that based on that letter it was no longer expecting an approval by the June 30 action date. Acurox, which includes the powerful pain reliever oxycodone, contains components designed to thwart prescription drug abuse, which can be common with opioid pain drugs.
The FDA had said in February that it wanted manufacturers to take stronger measures to prevent misuse and abuse of long-acting and sustained-release opioids, a class of powerful, highly addictive narcotics prescribed to relieve chronic pain.
Apart from Acurox, Acura has two more pain drugs, Acuracet and Vycavert, in the pipeline, and they are also designed to resist common methods of abuse through intravenous injection of dissolved drugs, nasal snorting of crushed tablets or swallowing in excess quantities.
"The other pipeline drugs are essentially the exact same thing (abuse-deterrent painkillers). So today's news can apply to their entire portfolio," Biologic Investment's McNamara said.
Shares of Acura fell to a low of $5.01 but pared losses to trade up 6 cents at $5.97 Thursday morning on Nasdaq. King shares were down 3 percent at $9.53 on the New York Stock Exchange. (Editing by Deepak Kannan)