Stock of Cambridge, Mass.-Based Genzyme Tumbles 8 Percent on FDA Delay.

Byline: Naomi Aoki

Dec. 28--Shares of Genzyme Corp. fell as much as 8 percent yesterday, a day after the company said the Food and Drug Administration had asked for additional information on the company's treatment for Fabry disease.

The delay of a decision on approval of the drug Fabrazyme sparked yet another round of speculation among investors about whether Genzyme could beat Transkaryotic Therapies Inc. in the race to become the sole provider of a breakthrough treatment for the rare genetic disorder.

FDA rules require that only one drug be approved to treat a rare disease such as Fabry, which affects only a few thousand people worldwide. The "orphan drug" act gives a company 10 years to sell its drug unhindered by competition in exchange for being the first to develop a drug to treat a rare disease.

The rule seems to turn the race for approval into a winner-take-all proposition for one of the Cambridge companies. Both firms submitted their applications to the FDA in June.

Analysts say the regulatory agency never before has been faced with two applications submitted within weeks of each other for nearly identical drugs to treat the same rare disease. And, they say, the situation puts pressure on the FDA to approve the better drug or find a loophole that allows approval of both.

But investors seemed to be hedging their bets following the news that the FDA had questions about Genzyme's application. The company's shares fell on the Nasdaq Stock Market while TKT's shares rose $3.31 to close at $35.44.