UPDATE 2-Vivus obesity drug to see US panel review in July

* Advisory panel on Qnexa ahead of Oct FDA action date

* Arena says has not heard from FDA about panel meeting

* Vivus shares unchanged

(Adds Arena comment, background, updates share price)

NEW YORK, March 26 (Reuters) - Vivus Inc's (VVUS.O) closely watched experimental obesity drug will be reviewed by a U.S. advisory committee in July, ahead of expected action by the Food and Drug Administration in October, the company said on Friday.

The FDA often holds meetings to solicit opinions from outside scientific advisors ahead of approval decisions on experimental medicines.

The Endocrinologic and Metabolic Drugs Advisory Committee is tentatively scheduled to review Vivus' Qnexa on July 15, the company said. The agency is expected to act on the Qnexa application by Oct 28.

"Because the FDA generally tends to follow the recommendation of the advisory panels, we should have a fairly clear idea of approvability of the drug after the panel vote," Leerink Swann analyst Steve Yoo said in a research note.

Rival Arena Pharmaceuticals (ARNA.O) has also filed for FDA review of its experimental weight loss drug, lorcaserin, and the deadline for the regulators decision is Oct. 22. A spokesman for Arena said on Friday that the company had not heard from the FDA about an advisory committee.

A third drug developer, Orexigen Therapeutics (OREX.O), has said it plans to file for FDA approval of its own experimental weight loss drug before the end of April.

Vivus shares unchanged at $9.36 in late trading on the Nasdaq.

The panel meeting is sure to be a major event as the history of obesity treatments is littered with disappointment. (Reporting by Lewis Krauskopf and Deena Beasley; Editing by Steve Orlofsky)