Sepracor Inc. stock gained $1 to $10.50 on Wednesday after thecompany said it has received a patent on S-fluoxetine, the pureisomer form of the anti-depression drug Prozac.

Prozac, sold by Eli Lilly and Co., is a racemic mixture consistingof R- and S- isomers, or mirror-image molecules. The drug had$990 million in 1991 sales, according to industry estimatesprovided by Sepracor.

While chemically identical, different isomers often havedifferent biological activity, with one isomer frequently beingeither inactive or responsible for a drug's side effects.

The use patent could position Sepracor in an exclusive positionto commercialize the isomer for depression once the patent forthe racemic form expires, said Timothy Barberich, presidentand chief executive.

The patent on Prozac will expire in 1995 in Europe and in 2001in the United States, said Barberich. The Marlborough, Mass.,company (NASDAQ:SEPR) plans to begin Phase I trials of S-fluoxetine in 1993.

"In general, our strategy is to work with the innovator when itmakes sense," said Barberich. He declined to say whetherSepracor is negotiating to license S-fluoxetine to Lilly.

Sepracor has filed about 40 patent applications for the single-isomer form of existing and new drugs as part of the company'sstrategy of product enhancement and patent life extension.

The company is conducting Phase I trials of the single-isomerform of the anti-inflammatory drug flurbiprofen in atoothpaste formulation for the treatment of bone loss due toperiodontal disease. The drug is currently marketed as Ansaidby The Upjohn Co. Sepracor is also in the clinic with a pureisomer form of the beta blocker atenolol for hypertension andangina, and expects to begin Phase III studies next year.Atenolol is sold by ICI plc as Tenormin. -- Karen Bernstein

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