SCIENCE / MEDICINE : Cancer Drug Shows Promise

From Times Staff and Wire Reports

A Johns Hopkins School of Medicine biochemist has found that a promising drug derived from a Chinese tree appears able to overcome cancer cells’ resistance to chemotherapy. Leroy F. Liu told a cancer symposium in Tokyo that the new drug is not affected by the action of protein “pumps” on cancer cell surfaces that reject most anti-cancer agents before they can be effective.

The drug--9-amino camptothecin or 9-AC--already has shown that it can dramatically shrink human colon cancers transplanted into “nude” mice, animals that lack an immune system and are routinely used to test drugs against tumors. And Liu has high hopes that the new drug will prove equally effective in continuing animal studies that target lung, breast and stomach cancers. “We will know soon,” Liu said.

“The reason 9-AC and camptothecin, the natural product, are effective in nude mice is not completely clear,” Liu said, “but it appears that camptothecin can accumulate inside solid tumor cells” that normally expel cancer-fighting drugs. Human trials are expected to begin within a year.