Orexigen Therapeutics tumbled 12 percent in premarket trading after regulators extended by three months a review of its experimental weight loss treatment.

The Food and Drug Administration is now expected to make a decision on Contrave, also known as NB32, by September 11.

Orexigen is trying to create a drug that reduces appetite and controls cravings while at the same time increasing the metabolism of users. Contrave combines bupropion, the active ingredient in the antidepressant Wellbutrin, with the anti-addiction drug naltrexone.

The FDA refused to approve the drug in 2011, citing concerns about cardiovascular risk. Orexigen resubmitted its application to regulators in December, saying that the drug fared well in an early analysis of a study designed to rule out excessive cardiovascular risk.

Since rejecting Contrave, the FDA has approved the obesity drugs Qsymia from Vivus Inc. and Arena Pharmaceuticals Inc.'s Belviq. Both of those drugs were also rejected initially.

Orexigen, based in La Jolla, California, has no products on the market, and Contrave is its lead candidate.

Shares of Orexigen Therapeutics Inc. fell 82 cents, to $5.99 in premarket trading. The stock had climbed 19 percent so far this year.