The company said it would consider out-licensing the product after it wraps up a second mid-stage study of the drug, codenamed ALKS 37.

"We will focus our future clinical development efforts on our other development programs including ALKS 9070 for schizophrenia and ALKS 5461 for major depressive disorder," Chief Medical Officer Elliot Ehrich said in a statement.

ALKS 37 was not important for the company, which derives a majority of its revenue from royalties, said Cowen & Co analyst Anant Padmanabhan.

"ALKS 37 would have been a nice-to-have but was not a key value driver for the company," the analyst told Reuters.

Ireland-based Alkermes receives royalties from drug makers including Johnson & Johnson for schizophrenia drugs Risperdal Consta and Invega Sustenna and from Amylin Pharmaceutical Inc for diabetes drug Bydureon.

The main pipeline product for the company now is its experimental schizophrenia drug ALKS 9070, since the company already has expertise in the field, the analyst said.

In the mid-stage study, ALKS 37 was able to improve bowel movement in the 150 patients it was tested on but did not satisfy the company's criteria to advance it into further studies.

The halt marks the second development failure for Alkermes. The company last July stopped developing an experimental drug to treat binge-eating disorder.

Opioids are very effective at managing pain but constipation is often a side-effect. Companies such as Salix Pharmaceuticals Ltd, Progenics Pharmaceuticals and Nektar Therapeutics are currently developing treatments for this condition.

Shares in Alkermes, which also sells an alcohol dependence treatment Vivitrol, fell marginally in extended trade on Wednesday. They closed at $16.06 on the Nasdaq.

(Reporting by Zeba Siddiqui in Bangalore; Editing by Sriraj Kalluvila)

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