Washington Editor

WASHINGTON - Stock values plummeted in the companies behind the molecular imaging agent Combidex (ferumoxtran-10) following a negative FDA panel vote. That thumbs-down damaged Advanced Magnetics Inc.'s shares by two-thirds and halved Cytogen Corp.'s stock.

Officials from Cytogen declined to speak to BioWorld Today, though Advanced Magnetics' chairman, president and CEO, Jerome Goldstein, said that the companies "look forward to meeting with the FDA to determine appropriate next steps."

Advanced Magnetics' stock (AMEX:AVM) plunged $12.40 Thursday, or 65.1 percent, to $6.65, while shares in Cytogen (NASDAQ:CYTO) dropped $6.75, or 51.9 percent, to close at $6.26.

Citing insufficient clinical data, the agency's Oncologic Drugs Advisory Committee voted 15-4 against supporting a broad indication for Combidex, declining the product's use to differentiate metastatic from non-metastatic lymph nodes across all cancer types. The new drug application is seeking approval for the product's intravenous administration and use as a magnetic resonance imaging contrast agent to assist in the differentiation of lymph nodes in patients with confirmed primary cancer who are at risk for lymph node metastases.

Data underlying the NDA included findings published in the New England Journal of Medicine showing that Combidex assisted in detecting lymph node metastases as small as 2 millimeters in prostate cancer patients. Other data, reported in Radiology, demonstrated the imaging agent's sensitivity for detecting the spread of cancer to lymph nodes in patients with urinary bladder cancer. Newer findings published in the Public Library of Science showed the feasibility of semi-automated analysis of Combidex-enhanced MRI in nodal staging.

Several panel members expressed enthusiasm for the product's potential compared to current lymph node imaging techniques, which include computed tomography and MRI without contrast. Nevertheless, the broad indication sought in the NDA proved to be the major stumbling block.

A final FDA decision is expected by March 30, the agency's designated user-fee goal date, and the agency typically follows its panels' recommendations.

Safety issues were not of paramount concern to the committee, although in FDA briefing documents released just before the panel meeting, the agency raised a question about a single study-related death in which a patient died after bolus administration of Combidex, which is made of iron oxide nanoparticles. Two other patients experienced serious but non-fatal reactions following bolus dosing, but the companies applied for administration via a 30-minute intravenous infusion.

Cytogen, of Princeton, N.J., had been drawing up plans to market the diagnostic product per terms of a U.S. commercialization agreement with Cambridge, Mass.-based Advanced Magnetics.