Clinical results from a trial of anti-idiotype antibodies inmelanoma patients showed a significantly longer survival insome patients, but not all patients appeared to have respondedto the therapy as expected from animal studies.
Anti-idiotypes create a molecular image of a selected cellmarker that should prompt the immune system to destroytumor cells bearing that marker.
The trial at Memorial Sloan-Kettering Cancer Center in NewYork showed that patients who developed antibodies thatrecognized the targeted marker on melanoma cells lived longerthan those who failed to develop the antibodies. Three patientsalso showed significant shrinkage of their tumors.
But nine of 23 patients did not develop signs that the anti-idiotype therapy was activating their immune systems todestroy the cancer. By contrast, all the mice that theresearchers have injected with the treatment have respondedappropriately.
Writing in the current Proceedings of the National Academy ofSciences, the researchers from New York Medical College inValhalla concluded that further studies should determine themechanisms underlying the inability of some patients todevelop immunity after the immunization.
Biotech companies are testing other anti-ids in clinical trialsagainst melanoma.
ImClone Systems Inc. (NASDAQ:IMCL) of New York said itbelieves that its anti-idiotype, which mimics the marker calledGD3 on the surface of melanoma cells, is the crucial antigen.
"GD3 is one of the more promising molecules for use inimmunotherapy for malignant melanoma," ImClone PresidentSamuel Waksal told BioWorld.
Phase I trials of ImClone's product started last July 1 at SloanKettering.
Phase III clinical trials of anti-id products developed by IdecPharmaceuticals Corp. (NASDAQ:IDPH) of La Jolla, Calif., againstB-cell lymphoma and Phase I clinicals against melanoma arealso in progress. -- Roberta Friedman
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