Sepracor Inc. will collaborate with Alza Corp. to develop atransdermally delivered single-isomer version of drugcurrently available only in racemic form.

The companies, which announced an agreement in principle onMonday, would not reveal the drug to be covered under theagreement. Sepracor (NASDAQ:SEPR) of Marlborough, Mass.,will receive a combination of development costs and royaltypayments for the development and manufacture of the agent,which Alza (NYSE:AZA) of Palo Alto, Calif., will then incorporateinto a transdermal patch delivery system. Other financialdetails of the agreement were not disclosed.

Robert Bratzler, general manager of Sepracor's chiral chemicalbusiness, told BioWorld that the company would move veryquickly into preclinical testing of the drug. He called thedevelopment of a single-isomer version of an FDA-approveddrug "relatively low risk" and predicted that the companywould be able to move into clinical trials quickly.

Bratzler explained that racemic compounds consist of twomirror-image isomers, only one of which is pharmaceuticallyeffective. While the "left-hand" isomer may deliver the desiredtherapeutic properties, the "right-hand" isomer may be thesource of side effects or may compete with the left-handisomer to reduce uptake and decrease dosage efficiency.

"None of this is predictable in advance," he added, so theadvantages of a given single-isomer drug over its racemiccounterpart will not be apparent until it is tested.

Although the company does not know how much it canimprove the pharmacokinetic profile and therapeutic efficiencyof the Alza drug, Bratzler said Sepracor believes the single-isomer version will have greater transdermal penetration thanthe racemic version. The resulting ability to put a given dose ofa drug into a smaller patch can be useful for compounds withlow potency, he said.

Sepracor will take advantage of its acquisition of a Nova Scotiamanufacturing facility, announced last week, to manufacturethe compound for Alza.

Sepracor's stock closed at $7.75 a share, up 50 cents. Alza'sstock closed at $28.88 a share, up 25 cents.

-- Karl A. Thiel Associate Editor

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