The U.S. Food and Drug Administration (FDA) has rejected Orexigen Therapeutics Inc. (NASDAQ: OREX)'s weight-loss drug Contrave on concerns over heart safety issues. Following the announcement, shares of the California-based company plunged nearly 72 percent in Tuesday's pre-market trade to $2.52.

Contrave is the third of three obesity drugs to be rejected by the US regulator since October when it turned down Arena Pharmaceuticals' lorcaserin, requesting for more data. The FDA also asked for more information about Vivus' Qnexa.

In a letter to Orexigen, the FDA stated that before your application can be approved, you must conduct a randomized, double-blind, placebo-controlled trial of sufficient size and duration to demonstrate that the risk of major adverse cardiovascular events in overweight and obese subjects treated with naltrexone/bupropion does not adversely affect the drug's benefit-risk profile.

We are surprised and extremely disappointed with the Agency's request in light of the extensive discussion and resulting vote on this topic at the December 7 Advisory Committee meeting, said Orexigen chief executive officer Michael Narachi.

We plan to work closely with the Agency to gain more information to determine the appropriate next steps regarding the Contrave application, he said.

Contrave, an investigational combination therapy of naltrexone HCl and bupropion HCl, was studied for its ability to help people with obesity initiate and sustain weight loss of at least 5 percent of their starting body weight in one year.

Contrave was submitted for U.S. regulatory approval in March 2010. The original submission was based on multiple clinical trials that evaluated Contrave in more than 4500 patients.

Orexigen's other product candidate Empatic for treating obesity has completed Phase 2 clinical development.

Shares of Orexigen ended Monday's regular trading at $9.09.