Synthetic snail venom might relieve cancer pain

Wednesday, January 7th 2004, 12:00 am
By: News On 6

CHICAGO (AP) _ A synthetic form of sea snail venom can ease pain in cancer and AIDS victims who get no relief from morphine or other conventional painkillers, a study found.

Laboratory research has found evidence that the venom that the snails inject to immobilize their prey might have beneficial effects on some heart problems, strokes, central nervous system disorders and other ills.

The latest study involved the experimental drug ziconotide, a laboratory-made equivalent of a compound in the venom of the small Conus Magus cone snail, which lives in shallow tropical saltwater.

The infusions produced significant relief in patients whose pain did not respond to more conventional drugs such as morphine.

Side effects, including dizziness and confusion, were common but can be reduced by fine-tuning the drug dose, said co-author Dr. David Ellis, a medical director of Elan Pharmaceuticals, which makes ziconotide and helped fund the study.

``This is a new, promising kind of treatment,'' said Dr. Jerome Yates, vice president for research at the American Cancer Society. Yates, who was not involved in the study, said thousands of cancer patients suffer from intractable pain and might benefit from the new drug.

Elan is seeking federal approval for the drug, and one of the researchers said he expects it to become commercially available within the year.

The study appears in Wednesday's Journal of the American Medical Association. Medtronic, which makes infusion pumps for delivering painkillers, co-funded the study.

Seeking human uses for animals' defense mechanisms is not new. Other recent efforts include an experimental drug derived from snake venom that has shown promise in treating strokes.

The snail-venom research involved 111 patients ages 24 to 85 in the United States, Australia and the Netherlands. All were treated with a small, battery-operated pump implanted in their abdomens and attached to a catheter that delivered continuous medication or a dummy drug into fluid surrounding the spinal cord. Treatment lasted about 10 days; most patients were not hospitalized during that time.

The patients rated their pain. Pain relief was moderate to complete in 53 percent of ziconotide patients, compared with about 18 percent of the placebo group.

Serious side effects occurred in 22 ziconotide patients and four placebo patients. Subsequent research has shown that starting patients on lower doses reduces the risks, and many have remained on treatment for more than a year, Ellis said.

``This gives us another weapon to help deal with those patients who don't respond to the normal, conventional treatments,'' said Dr. Steven Charapata, a co-author and director of the Pain Institute at Research Medical Center in Kansas City, Mo.