Enzyme-Blocking Drug May Fight Cancer

Experimental agent attacks tumor's blood supply, scientists say

MONDAY, Jan. 15, 2007 (HealthDay News) -- For the first time, an investigational cancer drug designed to block enzymes thought to play a role in tumor blood supply has been shown to be active in patients, a new U.K. study shows.

Previous research in animals indicated that enzymes involved in the synthesis of nitric oxide may play a role in maintaining blood supply to tumors. The new drug, N-nitro-L-arginine (L-NNA), is designed to block nitric oxide synthase enzymes.

In this dose-escalation phase I study, researchers assessed the effect of L-NNA on tumor blood volume in 18 patients with various kinds of cancers. The eight patients who received the higher doses of the drug showed a significant reduction in tumor blood volume an hour after they were given the drug. This reduction was maintained for 24 hours.

The study, published online Monday in The Lancet Oncology, also found a significant correlation between concentrations of L-NNA in the patients' blood and reduction of tumor blood volume after 24 hours. This provided more proof of the drug's anti-vascular activity, the researchers said.

"We have shown in vivo in patients with cancer that nitric oxide has a role in maintaining tumor blood supply, and we provide early clinical evidence that inhibition of nitric-oxide synthesis has tumor anti-vascular activity," study lead author Peter Hoskin, of the Mount Vernon Cancer Centre in Middlesex, said in a prepared statement.

Study first author Dr. Quan-Sing Ng, also of the Mount Vernon Cancer Centre, added, "The sustained reductions in tumor blood volume seen in all patients after just a single dose of L-NNA is exciting, and there is potential for its use as a novel vascular targeting agent in the treatment of cancer. This study provides support for further development of this agent in clinical trials."

More information

The American Cancer Society has more about cancer.

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