An advisory committee recommended on Thursday that theFood and Drug Administration approve Cytogen Corp.'sOncoScint for use in determining the location and extent oftumors in selected subsets of ovarian and colorectal cancerpatients.
Cytogen filed for OncoScint approval in September 1989 for thecolorectal indication and in March 1990 for the ovarian. Itwould be the first monoclonal antibody-based cancer imagingagent allowed on the U.S. market. OncoScint would have orphandrug status for the ovarian indication.
Cytogen (NASDAQ:CYTO) gained $3.38 to $31.50 on Thursday.
Although the Biological Response Modifiers AdvisoryCommittee unanimously recommended approval, it raisedquestions about Cytogen's claims for OncoScint's utility, andabout the efficacy and safety of multiple injections of the agent.
Panel members disputed Cytogen's contention that 25 percentto 30 percent of ovarian cancer patients would benefit fromOncoScint scans. Panel member Frederick Applebaum, aresearcher at the Fred Hutchinson Cancer Research Center inSeattle, said that Cytogen was "overstating the issue," and thatit would be of clinical utility for 10 percent to 15 percent ofthese patients.
The recommendation states that OncoScint should be approvedfor use in cases in which other diagnostic modalities areequivocal or negative.
The panel also raised concerns about human anti-mouseantibodies (HAMA) that Cytogen said develop in up to a thirdof patients after a single injection of OncoScint. The Princeton,N.J., company presented evidence indicating that about half ofthis group become HAMA-negative within four to 12 months.
Presence of HAMA can render further OncoScint scansinconclusive. It can also interfere with markers that are used totrace the tumor recurrence.
The panel also warned that a positive HAMA reading couldpreclude a patient's participation in trials of experimentalmonoclonal antibody cancer therapies. Because of the potentialimpact on diagnostic efficacy, the panel recommended thatOncoScint labelling include a warning that HAMA-positivepatients should not receive further injections.
OncoScint has received approvals in seven European countriesfor colorectal cancer diagnosis. The company plans to apply forovarian cancer indications soon.
Cheryl Shipley Coyle, director of marketing, said that thecompany expects to receive final FDA approval in time to startmarketing in April. The company projects annual U.S. sales of$200 million for colorectal cancer and $20 million for ovariancancer, with similar markets in Europe, Coyle said.
OncoScint kits sell for about $300 in Europe. Although U.S.pricing has not been set, the cost of a full-body diagnostic scanusing OncoScint and a gamma camera will be equivalent to thatof a CT scan, the company said.
-- Steve Usdin BioWorld Washington Bureau
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