UPDATE 1-U.S Patent Office allows key Orexigen drug patent

(Updates with details, analyst comment)

BOSTON, Jan. 31 (Reuters) - The U.S. patent office has approved a key patent covering an experimental obesity drug being developed by Orexigen Therapeutics Inc (OREX.O), according to the U.S. Patent and Trademark's Website.

The notice states that the patent on the drug, Contrave, has been allowed, though the notice of allowance has not yet been mailed.

Stephen Gendel, a spokesman for Orexigen, said the company knows about the approval but has not yet put out a press release as they have not received official notification.

"Orexigen's struggle to secure this patent has been a sticking point for many potential investors," said Cory Kasimov, an analyst at JP Morgan. "Now, however, we believe Contrave's value is substantially enhanced by any valuation metric."

Orexigen's shares closed on Wednesday at $10.94

(Reporting by Toni Clarke, editing by Dave Zimmerman)