Oncotech Inc. of Irvine, Calif., is developing a test to predict thelikely effectiveness of immunotherapeutic drugs in cancerpatients.

Interleukins, interferons, tumor necrosis factors and colonystimulating factors are naturally occurring compounds. Theycan be mass-produced in the laboratory and used astherapeutic agents to stimulate the immune system to attackcancer cells. But the compounds, also called biological responsemodifiers, are notorious for their ability to induce dramaticregression of cancers in a small number of patients whilehaving no effect, or even an extremely toxic one, in others.

Last summer, the Food and Drug Administration's BiologicalResponse Modifiers Advisory Committee denied approval ofCetus Corp.'s interleukin-2 to treat renal cell carcinoma, citingas one reason the need to be able to identify patients likely tobenefit from the therapy.

Oncotech's test may allow clinicians to pick out such patients.The method requires incubation of a tumor tissue sample in theabsence or presence of the therapeutic. The degree to whichthe tumor cells are killed is used as an index of drugeffectiveness. In February, the U.S. Patent and TrademarkOffice issued a patent to Oncotech covering the method.

The privately held company has applied the test, together withvarious immunotherapeutics, to hundreds of human cancerspecimens. The test judges a given drug as effective at thesame frequency -- about 30 percent -- as seen in clinical trialsof the drugs, said Larry Weisenthal, Oncotech vice president forscientific affairs and the inventor of the Oncotech method. Hesaid the tests also have shown that immunotherapeutic drugswere often more effective at killing cancer cells taken frompatients who had previously received chemotherapy.

Oncotech now must show that a positive laboratory test resultfor a drug correlates with successful treatment of the cancer.The company plans to start clinical trials this summer, saidWeisenthal.

-- Rachel Nowak Washington Bureau Chief

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