ImmunoGen Inc. annonced that it has been issued U.S. patent No. 5,239,062, covering itspotent cytotoxic agent blocked ricin and its use in conjugates that specifically killcancer cells.

Blocked ricin is a derivative of the toxin ricin, which is derived from castor beans.In laboratory tests, it has been shown to be up to 1,000 times more potent thanconventional chemotherapeutic agents.

“This patent further strengthens ImmunoGen's proprietary position on the use ofthe Oncolysins as innovative anti-cancer agents,“ said Mitchel Sayare, chairman andchief executive officer of ImmunoGen (NASDAQ:IMGN).

ImmunoGen of Cambridge, Mass., develops innovative therapeutics for treating cancer andimmune-mediated diseases. It has for Oncolysin conjugates in clinical trials in thetreatment of various types of cancer.