Data from the completed Phase I clinical safety trial ofImmunoGen Inc.'s Oncolysin S immunoconjugate for treatingsmall cell lung cancer were presented Monday at the AnnualMeeting of the American Society of Clinical Oncology (ASCO) inOrlando, Fla.

The 21 patients in the trial had relapsed with small cell lungcancer (SCLC), a malignancy that is particularly vicious. Evenafter chemotherapy, patients almost always relapse within 12-18 months. Less than 5 percent of the 40,000-50,000 patientswho get this type of cancer every year in the U.S. survive longterm.

"We have established a safety profile for the drug in this trial,and we also have seen evidence of efficacy at the higher dosesused," said Carol Epstein, vice president and chief medicalofficer at ImmunoGen of Cambridge, Mass.

"This includes one partial response of significant duration andseveral patients whose disease has stabilized followingtreatment with Oncolysin S," Epstein added. This partialresponse lasted four months, after which that patient was "lostto follow-up," according to Mark Ratner, ImmunoGen's directorof external communications.

Oncolysin S specifically binds to the CD56 antigen, a markerfound on SCLC cells, and ImmunoGen scientists havedocumented that it does indeed bind to metastasized SCLCtumor cells in bone marrow, liver and lung. The antibody-toxinconjugate also apparently binds to some peripheral nerve cellsand cardiac muscle, but Epstein said that "we have observed nocardiac or neurological toxicity related to the administration ofthe drug."

ImmunoGen (NASDAQ:IMGN) is "moving quickly to broadenclinical studies to include SCLC patients who are in remissionfollowing treatment with conventional chemotherapeuticagents," said Donald McCarren, ImmunoGen's president andchief executive officer.

ImmunoGen received the go-ahead from FDA for this Phase Itrial of Oncolysin S in the fall of 1990, and treated the firstpatient in February 1991 at Dana Farber Cancer Institute inBoston. "It's not an easy patient group," Ratner told BioWorld."We're treating patients with the disease who have noalternative therapies available to them."

While ImmunoGen's immunotoxin therapeutic targets the smallcell lung cancer cells by a "seek-and-destroy" approach,ImClone Systems Inc. (NASDAQ:IMCL) is using a vaccine madeof anti-idiotypic antibodies to inhibit the SCLC cells fromgrowing. ImClone of New York started a Phase I pilot trial onits LuVax anti-id vaccine at New York's Memorial SloanKettering Cancer Center in February. The anti-id is designed tomimic, and consequently elicit an immune response againstGD3, an antigen found on the surface of small cell lung cancercells. When administered after chemotherapy, the vaccinecould inhibit the growth of any remaining GD3-containing cells,thus reducing or preventing relapse.

And Genetic Therapy Inc. (NASDAQ:GTII) of Gaithersburg, Md.,has decided to try gene therapy for treating small cell lungcancer. In fact, the Recombinant DNA Advisory Committee ofthe National Institutes of Health approved its gene-therapyprotocol last October. Those trials will involve the direct in vivo administration into patients of genetically altered vectors,designed to contain an antisense gene to the cancer-causing k-ras gene. Administering this construct to patients may slow therate of tumor cell growth. The trials, which will be performedat M.D. Anderson Cancer Center in Houston, haven't started yet,according to Marc Schneebaum, Genetic Therapy's vicepresident and chief financial officer. "We're still in the processof getting FDA approval," he told BioWorld.

-- Jennifer Van Brunt Senior Editor

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