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Subject: ImmunoGen Drug Eradicates Large Human Colon Tumors in Mice Without Harmful Side Effects; Proceedings of the National Academy of Sciences Report Date: Tue, 6 Aug 1996 05:41:43 -0700 PR Newswire Press Release: CAMBRIDGE, Mass., Aug. 6 /PRNewswire/ --Researchers at ImmunoGen, Inc. (Nasdaq: IMGN) reported today that an experimental compound completely eradicated human colon tumors grown in mice at doses well below those that produce toxic side effects. The studies, published today in the Proceedings of the National Academy of Sciences USA (PNAS), suggest that the drug, called C242-DM1, represents a promising new approach to the treatment of colorectal cancer. "One of the key challenges in cancer drug discovery is to deliver sufficient drug to kill the tumor without also producing intolerable side effects," said Walter Blattler, ImmunoGen's Senior Vice President, Research and Development, and a study author. "The effectiveness of conventional cancer drugs is limited by side effects because they act non-specifically on dividing cells. More recent efforts to use antibodies to target these compounds to tumor cells have generally resulted in agents with reduced drug potency that require high, toxic doses to achieve a significant effect. "Our approach to this challenge was to select a cytotoxic drug, DM1, that is over 100 times more potent than conventional agents and link it with an antibody, C242, that binds to a protein commonly found on colon tumor cells," explained Dr. Blattler. "We have shown that we are able to harness the high potency of DM1 and deliver it specifically to the tumor. While animal studies must be interpreted cautiously, the results are particularly striking in light of the poor response of colon tumors to current drugs. C242-DM1 uniformly eliminated large tumors at doses that had minimal toxicity. The drug was effective even when tested against tumors expressing low levels of the protein recognized by the C242 antibody." Colorectal cancer is one of the most common malignancies and is among the leading causes of death from cancer. There are approximately 140,000 new cases each year in the United States alone. Although surgery is the primary treatment for these tumors, about one-half of patients eventually die from the spread of the disease to other organs. Chemotherapy, which is used as an adjunct after surgery, yields a response rate of under 25 percent and has not significantly improved long-term patient survival. In the studies reported today in the PNAS, the research team, led by Changnian Liu, Ph.D., and Ravi Chari, Ph.D., both of ImmunoGen, tested C242- DM1 against several types and sizes of human colon tumors that were grown in immune-deficient mice. Initially, the researchers treated eight mice with a daily injection of C242-DM1 1/8equivalent to 300 micrograms of DM1 per kilogram (kg) 3/8 for five days. All eight mice were "cured" of their tumors and remained tumor-free for 200 days, the duration of the experiment. Significantly, the mice did not lose weight, indicating the absence of toxic side effects when treated with the drug at this dose. By contrast, treatment with the unconjugated drug and antibody had only a minimal effect on tumor growth. To further assess the potency of C242-DM1, mice were given lower doses, equivalent to 150 to 300 micrograms of DM1 per kg per day for 5 days. The drug successfully eliminated tumors in all of the animals at doses as low as 225 micrograms of DM1 per kg per day, less than 60 percent of the maximum tolerated dose. The researchers observed a significant delay in tumor growth even at the lowest dose tested. The researchers also compared the effect on larger tumors of C242-DM1 with that of 5-FU, the chemotherapeutic drug most frequently used in the treatment of colon cancer. Again, C242-DM1-treated mice were "cured," remaining tumor free for 200 days, while administration of 5-FU at the maximum tolerated dose only slightly delayed (for five days) tumor growth. In still larger tumors, C242-DM1 produced complete regressions lasting seven weeks in six of eight mice. The remaining mice remained tumor-free for the duration of the experiment (120 days). Finally, the researchers compared the effectiveness of C242-DM1 and 5-FU in mice which had been injected with two other types of colon tumors (those which express the protein recognized by the C242 antibody on only 20-30 percent of their cells, as opposed to on all of their cells). There were complete tumor regressions for five weeks in all of the animals treated with one five-day course of treatment with C242-DM1 1/8equivalent to 300 micrograms of DM1 per kg per day 3/8. The researchers also were able to extend the tumor- free period to nine weeks by administering a second course of treatment with C242-DM1. The second course also did not produce toxic side effects, suggesting that use of multiple cycles of this drug for treatment of colorectal cancer may be a feasible clinical regimen. In contrast, these tumors grew large rapidly in the control animals treated with 5-FU. "C242-DM1 represents a new class of anticancer drugs that may fulfill the potential of antibody-targeted chemotherapeutic agents," said ImmunoGen Chairman and Chief Executive Officer, Mitchel Sayare. "We plan to build on these highly promising results and further validate the technology base we have established at ImmunoGen." The studies are reported in an article entitled "Eradication of Large Tumor Xenografts by Targeted Delivery of Maytansinoids". In addition to Drs. Liu, Chari and Blattler, the authors on the paper include B. Mitra Tadayoni, Ph.D., Lizabeth A. Bourret, Kristin M. Mattocks, Susan M. Derr, Wayne Widdison, Ph.D., Nancy L. Kedersha, Ph.D., Pamela D. Ariniello, Victor Goldmacher, Ph.D., and John M. Lambert, Ph.D., all of ImmunoGen. ImmunoGen, Inc., develops innovative biopharmaceuticals, primarily for cancer treatment. The Company has created potent immunoconjugates consisting of toxins or drugs coupled to monoclonal antibodies for delivery to and destruction of cancer cells. ImmunoGen's first product, Oncolysin B, is being tested in a large-scale Phase III clinical trial for the treatment of lymphoma subsequent to autologous bone marrow transplantation. This press release includes forward-looking statements based on management's current expectations. Factors that could cause future results to differ materially from such expectations include, but are not limited to: ability to secure future funding, difficulties inherent in developing pharmaceuticals; uncertainty as to whether there will exist adequate reimbursement for these products from government, private healthcare insurers and third-party payors; and uncertainties as to the extent of future government regulation of the pharmaceutical business. NOTE: Backgrounder available upon request. SOURCE ImmunoGen, Inc. -0- 8/6/96 /CONTACT: Mitchel Sayare, Chairman, Chief Executive Officer of ImmunoGen, Inc., 617-661-9312, or Robert Gottlieb of Feinstein Partners Inc., 617-577-8110/ | ||||||||||||
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