TUESDAY, April 15 (HealthDay News) -- The drug riluzole, approved in the United States to treat amyotrophic lateral sclerosis (ALS), slows the growth of highly aggressive melanoma skin cancer, according to a new study.

A common feature of both melanoma and ALS (also called Lou Gehrig's disease) is an excess amount of the protein glutamate, a cellular growth factor or food for cells. Too much glutamate can overstimulate neurons to the point where they burn out -- a possible explanation for what happens in ALS, according to background information in the study. Overproduction of glutamate causes the growth and expansion of melanoma.

Riluzole (brand name Rilutek) inhibits the release of glutamate.

In laboratory tests using cultures of human melanoma cell lines, researchers at Rutgers University and the Cancer Institute of New Jersey found that riluzole appeared to switch off overproduction of glutamate and slow the growth rate of the melanoma cells. In tests on animals, the drug showed the same suppression of melanoma cell growth.

The researchers then started testing the drug on 11 people with late-stage (stage 3 or 4) melanoma. The patients in this phase 0 (exploratory, first-in-humans) trial received riluzole for two weeks.

"Our preliminary results show three solid positive responses in nine of the patients who had been able to complete the trial to date," Dr. James Goydos, a surgical oncologist at the Cancer Institute of New Jersey, said in a prepared statement.

Other patients in the group showed some indications of responding to the drug, and they'll be reassessed at the end of the trial.

The research was to be presented April 15 at the annual meeting of the American Association for Cancer Research, in San Diego.

The findings provide "enough data to show that we should go on to a more extensive (phase 1/2) trial," Goydos said. He expects it will begin later this year and include 50 to 100 patients with stage 4 melanoma.

"I think this drug is going to be extremely important as an adjunct to surgical treatment of stage 3 or stage 4 melanoma," Goydos said. "The challenge is to keep it from recurring, which has happened in patients on the order of 50 percent. With low toxicity likely, riluzole could potentially be given for long periods of time to slow down the metabolic process responsible for the disease's recurrence."

More information

The U.S. National Cancer Institute has more about melanoma.