After the market closed Monday, EPIX Pharmaceuticals Inc. said the FDA extended the action date for MS-325, EPIX's imaging pharmaceutical, by 90 days until mid-January. EPIX then watched its stock fall more than 15 percent Tuesday.

The FDA's communication - in the form of a fax - "came as a surprise, as we were roughly two weeks away from our mid-October PDUFA date," Michael Webb, EPIX's CEO, said in a conference call late Monday.

The stock (NASDAQ:EPIX) closed at $16.99, down $3.01, or 15.1 percent.

EPIX, of Cambridge, Mass., filed for approval of MS-325 in December, and the agency accepted the package for review in February. Since then, though, the FDA has asked for additional analyses of the submitted data, one of which it classified as a "major amendment," Webb said, thereby allowing the agency to extend the action date. (See BioWorld Today, Dec. 17, 2003.)

The major amendment, or "the straw that broke the camel's back," as Webb put it, "relates to an August 30 submission of a supplemental database. This database was requested by the statistical reviewers to aid in their evaluation." He added that the filing contains data from four Phase III trials and 780 patients.

Since the filing in December, EPIX has submitted analyses relating to non-contrast magnetic resonance imaging, uninterpretable scans and subgroup analyses by scanner type, geographic location, vessel bed and readers, the company said. There has been no request for new data.

Still, though, holders sold off Tuesday, and the company was downgraded by San Francisco-based Wells Fargo & Co., which changed its rating from "buy" to "hold."

EPIX is seeking approval for MS-325 as a blood-pool agent designed for magnetic resonance angiography. MS-325 is designed to bind reversibly to human serum albumin, thereby brightening the blood for an extended amount of time.

Webb noted that EPIX has "had an excellent review under way" and that he thinks "we can get things resolved in the 90-day time frame."

The agent is being developed with Schering AG, of Berlin, in a deal signed in May 2003. Schering "is working with us in our interactions and responses to the FDA," Webb said, and the partner submitted an application for marketing approval in the European Union, which was accepted for review in June. The partnership also includes EP-2104, an imaging agent for blood clots, and the companies also are researching new compounds for magnetic resonance imaging.

The company reported a net loss of $5 million for the quarter ended June 30, or 22 cents per share, on revenues of $3.2 million. It had cash, cash equivalents and marketable securities of $173.6 million at the end of the second quarter, and 22.9 million shares outstanding.