Cytogen Corp. announced Wednesday that FDA approved thefirst monoclonal antibody (MAb)-based imaging agent formarketing in the U.S.

The product, OncoScint CR/OV, allows physicians to visualizethe extent and location of malignancies in patients with knowncolorectal or ovarian cancer in whom recurrent or metastaticdisease is suspected. The agent may provide earlier diagnosisof small tumor deposits in the abdominal cavity in patientswith recurrent ovarian cancer, growths that are often missedby conventional tests, according to FDA.

Colorectal cancer is the second most common malignancy in theworld, and strikes about 150,000 Americans each year. Ovariancancer accounts for 4 percent of all cancer in women, with anestimated 21,000 new cases diagnosed in the U.S. each year.The ovarian cancer application for OncoScint has orphan drugapproval, allowing exclusive marketing for seven years.

Cytogen (NASDAQ:CYTO) of Princeton, N.J., submitted a productlicense application (PLA) in September 1989 for colorectaldiagnostic imaging using patented, proprietary antibody"linker" technology that attaches genetically engineered mouseantibodies to radioisotopes.

Upon injection into the patient, the MAb seeks out and binds tospecific malignant cells. Radioactivity from the attached isotopeis detected outside the body by a gamma camera to reveal thelocation and extent of disease.

Cytogen filed a product license application (PLA) to use thediagnostic agent in ovarian cancer in April 1990.

"The statement this approval makes about our technology ismore profound than the product itself," Martin Cleary,Cytogen's group vice president told BioWorld. "It validates thetechnology and the platform we've spent so long developing."

The product was approved for single-use applications. InSeptember, Cleary said, Cytogen submitted a dossier formultiple-use applications so patients could be followed forcancer recurrence. Successive injections have been a concernbecause up to a third of patients may develop human anti-mouse antibodies (HAMA) after exposure to the agent. Abouthalf of reactive patients apparently become human anti-mouseantibody-negative within four to 12 months, however.

The FDA's approval includes the first commercial use ofIndiclor, indium-111 chloride, an imaging agent used inconjunction with OncoScint CR/OV. Developed by AmershamInternational of Arlington Heights, Ill., it is marketed by Medi-Physics Inc.

Cytogen is completing Phase III clinical trials of an OncoScintimaging agent for prostate cancer, Cleary said, and isdeveloping therapies to direct radiation treatment to malignanttissues, with a therapy for ovarian cancer in Phase II clinicaltrials, and a therapy for prostrate cancer in Phase I.

The newly licensed product will be jointly promoted byCytogen and U.S.-based Knoll Pharmaceutical Co., which isowned by BASF A.G. and Knoll A.G.

Cytogen received a milestone payment from Knoll uponreceiving FDA approval, and plans to launch the product in lateJanuary.

Approval "gets the product out on the market so physicians cansee what it can do," said Maureen McGann, an analyst withMerrill Lynch, which was one of the underwriters for Cytogen'sinitial public offering. "The next step is getting physicians touse it."

McGann projected U.S. sales in 1993 of $22 million for thecolorectal application and $4 million for the ovarian application,with sales reaching $100 million and almost $16 million,respectively, by 1998. She projects a total U.S. market atmaturity in 1998 of $240 million for colorectal use and $20million for ovarian use.

She also forecasts losses of 76 cents per share this year, 28cents per share in 1993, and a profit of 97 cents a share in1994.

Edmund A. Debler, who follows the biotechnology sector forMehta & Isaly, added that the approval will allow the productto undergo "some real field testing" to gauge its value and showhow much it will affect treatment.

In clinical studies, physicians told Cytogen, the imaging agentchanged their course of treatment one out of four times. Theagent is licensed to be used in conjunction with other tests.

Cytogen's closest competitor, Immunomedics Inc.(NASDAQ:IMMU) of Morris Plains, N. J., filed an application for anew product license for a colorectal cancer imaging agentalmost 18 months later than Cytogen.

"We think the FDA had a big learning curve on this technology,"Amy Factor, Immunomedics' vice president of finance andadministration, told BioWorld.

Factor asserted that her company's ImmuRAID-CEA is superiorbecause it uses an antibody fragment, avoiding HAMAreactions, and is excreted by the kidney instead of the liver, aprimary site of colorectal cancer spread. OncoScint is excretedby the liver and will not specifically target malignancies there.Factor said ImmuRAID-CEA also uses a readily available andless-expensive isotope, technetium-99, and requires only a fewhours after injection for an imaging session rather than two tofour days. Immunomedics has a marketing agreement with thechemotherapy marketer Adria Laboratories of Columbus, Ohio.

Cowen & Co. analyst Carol Werther predicted a worldwidemarket of $400 million for colorectal imaging applications andissued "buy" recommendations on both Cytogen andImmunomedics, saying that being first will help Cytogendespite the competition.

Cytogen's stock was up $3.25 a share on Wednesday, closing at$22.25. Immunomedics closed at $10.38, up 38 cents a share.

-- Nancy Garcia Associate Editor

(c) 1997 American Health Consultants. All rights reserved.

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