FDA seeks contingency details from Genzyme

The company is the only supplier of the drugs Fabrazyme and Myozyme, and the request from the FDA raises the possibility that regulators could revoke Genzyme’s so-called orphan drug status, which gives it seven years of exclusivity for drugs to treat conditions affecting 200,000 or fewer people.

But some industry analysts said such a move was unlikely, noting that Genzyme’s market exclusivity for Fabrazyme expires next April and no competitor is in a position to win approval for a competing drug by then. The company will continue to have exclusive rights for Myozyme until 2013, but the FDA has thus far approved production of it only in small batches.

The company said the FDA’s request for supply assurances came last month as Genzyme was decontaminating its Allston Landing plant after it detected a virus on production equipment in June.

That plant produces Fabrazyme and another drug, Cerezyme, which does not have orphan drug status. Genzyme used to produce large batches of Myozyme for the European market, but production was shifted to Belgium. Genzyme sterilized the Allston plant and resumed manufacturing late last month, but will not begin shipping new lots made there until late this year.

David Meeker, executive vice president for therapeutics and corporate operations at Genzyme, yesterday said the company has responded to the FDA’s request. “We’ve told them this interruption in supply is temporary and we’re working our way through that,’’ he said. “We’ll be through the Fabrazyme shortage by the end of the year.’’

FDA officials are “concerned about the situation and following it closely,’’ said agency spokeswoman Karen Riley. She would not address the possibility of the FDA revoking orphan drug status for one or both of the Genzyme drugs covered in its July request.

Fabrazyme and Myozyme are enzyme replacement treatments. Fabrazyme treats Fabry disease, in which a missing or faulty enzyme prevents the body from breaking down oils, waxes, and fatty acids that build up in the eyes and kidneys as well as the nervous and cardiovascular systems. Myozyme treats Pompe disease, which interferes with muscle development and causes severe respiratory problems.

Analysts said the FDA is prudent to protect patients by closely monitoring the situation. But they noted that Genzyme has been working to address its production problems and said the FDA has only revoked orphan drug status in the past when it determined that a patient population had exceeded 200,000 - a standard for exclusivity.

“I’m not aware that the FDA has ever removed exclusivity because of supply issues,’’ said Kevin J. Gorman, managing partner for Putnam Associates, a Burlington consulting firm specializing in life sciences. “I’d be very surprised if that was to happen. I don’t see that there’s a generic company waiting in the wings with new drugs.’’

In its filing with the Securities and Exchange Commission this week, Genzyme also disclosed that FDA inspectors, who will be paying another visit to the Allston Landing site soon, will be examining the company’s cleanup campaign there and its effort to identify the source of the virus discovered in the facility in June.

The disclosure on July 31 that inspectors will revisit the Allston plant was followed on Aug. 3 by news that the FDA had given doctors approval to prescribe a rival drug to Cerezyme, the Genzyme treatment for Gaucher disease, though the competing drug developed by Shire PLC has not been approved for commercial use.

Those developments sent Genzyme’s shares down more than 10 percent, though they have recovered much of that loss.

Yesterday, shares edged up 95 cents, or 1.9 percent, to $50.31 on the Nasdaq exchange.

Robert Weisman can be reached at weisman@globe.com.