Cone snails are by many accounts extraordinary predators of the sea. While lying hidden in mud on the ocean floor, these deadly sea snails use their proboscis, which wiggle in a worm-like fashion, to attract fish. Once a curious fish draws close, the snail swiftly sends out a tooth-like harpoon, which injects the fish with its poisonous venom. The venom is a fast-acting painkiller and quickly paralyzes the fish, which the cone snail then eats for dinner.
Researchers are intrigued by this unique sea creature, especially the venom that its produces, because of its ability to turn off pain receptors. That’s why a group of German scientists from the Pharmaceutical Institute of the University of Bonn is studying the cone snail for its potential use in blocking pain signals in humans.
“We are interested in the cone snail’s neurotoxins, called conotoxins. They can be effective in minute quantities, interrupt the transmission of signals in nerve paths in a highly selective manner, and are thus able to block the transmission of pain very well,” says Dr. Diana Imhof, the project’s lead investigator.
The toxins are of particular interest for developing analgesics for chronically ill or terminal cancer patients for whom other medications can no longer be used. The venom of some cone snails is 1000 times as powerful as morphine and, perhaps just as important, is non-addictive.
“The advantage of these conotoxins is that they do not cause dependency. Since the peptide we studied decomposes rather quickly in the body, we do, however, need more stable forms that we can administer,” said Imhof.
The German scientists have been able to replicate the cone snail’s venom in vitro. They were able to find three active peptide types, but found slight variations in their biological efficacy. Imhof and her colleagues want to conduct additional studies, but caution it could take years before patients see any benefit. “We are still in the basic research stadium,” said Imhof.
In the U.S., a pharmaceutical grade drug derived from cone snail neurotoxins has already been developed and marketed under the brand name Prialt. Prialt is the first Food and Drug Administration approved painkiller derived from cone snail neurotoxins. The drug is injected in spinal cord fluid to treat severe pain caused by failed back surgery, injury, AIDS, and cancer.
Many cone snail produced peptides show promise as future pain medications and are in preclinical and clinical trials. For example, a peptide derived from an Australian cone snail has been shown effective in treating neuropathic and postsurgical pain, and accelerating recovery from nerve injuries. Other conotoxin compounds are also being tested as potential treatments for epilepsy, Parkinson’s disease, and Alzheimer’s disease.