BOSTON (TheStreet) -- Arena Pharmaceuticals (ARNA - Get Report) shares plunged Tuesday after a staff review of its experimental diet drug by the Food and Drug Administration highlighted three safety issues, including rat rumors and memory loss.

Arena Pharmaceuticals shares tumbled by $2.50, or 36.5%, to $4.35 after an initial review of its drug lorcaserin showed "valvular heart disease, neuro-psychiatric and cognitive-related adverse events, and preclinical tumor development" in rats.

The FDA staff review also noted that lorcaserin 10 mg tablet satisfied categorical efficacy criterion "by a slim margin." An FDA advisory panel will hold a public meeting on Thursday to discuss lorcaserin.

Other obesity drug makers were trading lower in sympathy. Vivus ( VVUS - Get Report), which saw an FDA panel vote against its drug Qnexa in July on safety risks, was down 1.1% to $6.07. Orexigen Therapeutics ( OREX), which will meet with an FDA advisory panel in December over its drug Contrave, slumped nearly 7% to $4.79.

-- Written by Robert Holmes in Boston.

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