Takeda Pharmaceutical Co. has threatened to end its collaboration with Orexigen Therapeutics Inc. after a safety study of the obesity drug Contrave was halted by researchers who criticized Orexigen for an early release of trial data.

"Takeda sent a dispute letter to Orexigen on May 12 whereby Takeda seeks termination of its collaboration agreement with Orexigen based on Orexigen's material breach of the agreement," spokeswoman Sandy Rodriguez said Tuesday in an email.

"Takeda is working closely with Orexigen to try to resolve the situation and avoid termination of the agreement." Takeda didn't say what it considered a material breach.