Faced with the prospect that generic competition for Eli Lilly and Co.'s Prozac fluoxetine anti-depressant is just around the corner, investors apparently decided not to wait around to see if LLY will be able to defend its franchise with Sepracor Inc.'s pure R-enantiomeric form of the drug.

A U.S. appeals court ruling last week made it likely that a generic version of Prozac could be on the market as early as next February. Investors responded by dumping SEPR (Marlborough, Mass.), which has licensed its R-isomer to LLY, perhaps