Epix and marketing partner Schering AG will need to conduct additional studies for their vascular imaging agent MS-325 following an FDA "approvable letter."

"Epix has received an action letter from the FDA designating MS-325 as approvable but requesting additional clinical studies," Epix CEO Michael Webb said during an analysts call Jan. 14 to discuss FDA's decision.

The approvable letter requests additional clinical studies for MD-325 (gadofosveset trisodium) due to a possible confounding effect depending on the non-contrast baseline comparator scanning method used in Phase III trials.

"FDA continued to express its concern that a lack of standardization in the non-contrast imaging procedures may have generated poorer quality non-contrast [magnetic resonance angiography] images than could have been theoretically obtained if the sites had used a uniform standard method," Webb said.

FDA also questions the statistical treatment of uninterpretable baseline scans which may have inflated MS-325's efficacy.

"The FDA is concerned about what it perceives to be a high rate of uninterpretable non-contrast scans in our prespecified analysis, and that the rate of the uninterpretable scans may have artificially exaggerated the benefit of MS-325," Webb said.

Epix maintained that the NDA is adequate for approval and that the company followed FDA guidance on trial design.

"Throughout the MS-325 development program, we have sought and received FDA guidance regarding the appropriate path to approval for a general magnetic resonance angiography label outside the heart," Webb said.

"Ultimately we pursued a Phase III strategy suggested by the agency," he said.

One upside for the company is that the FDA letter did not cite any safety or manufacturing deficiencies for MS-325.

The announcement comes one day before the product's user fee date.

Epix originally submitted the NDA on Dec. 15, 2003. The user fee date was extended to Jan. 15 following the submission of a re-analysis of the clinical trial data in October (¹ Also see "Epix MS-325 User Fee Date Extended" - Pink Sheet, 4 October, 2004.)

- John Rancourt

Schering AG/Epix' Imaging Agent Requires Additional Clinical Studies, FDA Says

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