ROCKVILLE, Md. -- Xoma Corp. stock plunged $5 to $15.50 onWednesday after the Food and Drug Administration said it wasnot ready to act on the company's E5 antibody and members ofan advisory committee said they were unenthusiastic aboutrecommending approval for the drug without further studies.

The committee members' opinions were voiced in paneldiscussion after the surprise announcement by Dr. ThomasHoffman that the agency was "not prepared to accept arecommendation regarding licensure of this product." Hoffmanis chairman of the licensing committee that has beenconsidering Xoma's application for E5 as a treatment for gram-negative sepsis.

Xoma's clinical data on reduced mortality rates for patientstreated with E5 are "marginal," said Richard Johnson, actingchairman of the Vaccines and Related Biological Productsadvisory committee. "On balance, we could not find significantdata to assure us that it would be effective clinically."

He added, "The FDA says they are not through with theiranalysis, so we don't really have all the data we need."

The FDA has not finished analyzing results of a second PhaseIII trial because the company did not submit data until July 29,said Hoffman, who is also lab chief in the division ofhematology in the Center for Biologics. FDA "staff are notreadily available in August" to do analysis, he told BioWorld.

Hoffman said he expects the analysis to be completed "in acouple of weeks. There are no identifiable obstacles thatanyone in the FDA has found to this point."

Xoma said it had "no indication" prior to the long-awaitedmeeting that the committee would not vote on the application.President Patrick J. Scannon promised that the Berkeley,Calif.-based company will work with the FDA "day and night" tocomplete the analysis.

Scannon said Xoma is seeking approval for E5 to treat "patientswho can be prospectively identified at the bedside as havingsuspected gram-negative sepsis and organ failure that ishighly correlated to endotoxemia prior to development ofrefactory shock."

An FDA decision on whether to reconvene the advisorycommittee to review E5 again "could go either way," saidHoffman. The committee is not scheduled to meet again untilNovember.

However, Scannon said he has "no evidence" that an additionalreview meeting will be required, "and our very strong feelingis that once the analysis is completed, we will not have aproblem moving ahead."

Most of the advisory committee members expressedreservations about approval for E5, however. "As it standsnow, there are insufficient data to convince most members ofthe advisory committee that the risk-to-benefit ratio comesdown in favor of licensing of the drug. So the implication is, ifyou want approval, there are going to have to be someadditional studies," Johnson said.

Committee members expressed concerns about E5 side effects,including hypotension episodes, and a human anti-mouseantibody (HAMA) response that would preclude retreatment. E5is derived from mouse antibodies, while rival Centocor'sCentoxin is derived from both human and mouse antibodies.

Several members called for comparative tests that wouldinvolve testing Centoxin and E5 together.

Scannon said Xoma (NASDAQ:XOMA) will later develop E5 forindications that include shock and will address HAMA, whichwill become "a very minor issue."

-- Kris Herbst BioWorld Washington Bureau

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