Tiny, seemingly harmless cone snails may one day be the source of pain relievers stronger than morphine that can treat chronic nerve pain. Scientists from the University of Queensland in Australia have identified five new experimental substances derived from cone snail venom that contains hundreds of small proteins known as conotoxins. Cone snails use their conotoxins to paralyze prey, but conotoxins seem to have an analgesic effect in humans, according to Professor David Carik, Ph.D., who led a study reporting on the new substances.
“This is an important incremental step that could serve as the blueprint for the development of a whole new class of drugs capable of relieving one of the most severe forms of chronic pain that is currently very difficult to treat,” said Dr. Craik.
Dr. Craik will be presenting the scientists’ work at the 247th National Meeting & Exposition of the American Chemical Society taking place this week in Dallas, Texas. Although the use of conotoxin-derived medication is not novel (ziconotide has been approved for use in humans), Dr. Craik and colleagues are developing conotoxin-based drugs that can be taken orally (ziconotide must be injected into the lower spinal cord). Oral administration of conotoxin would be possible as the scientists modified the proteins to form circular chains of amino acids. In this form, they are extremely stable and resistant to enzyme attack in the body. These drugs could be used in patients who suffer from chronic neuropathic pain and replace addictive drugs such as morphine. Addiction is less of a concern for conotoxins because they act on different receptors in the brain than morphine.
Conotoxin-based drugs have shown benefits during laboratory tests on rats using standard protocols to test pain. What’s more, small doses of conotoxin were 100 times more potent than the “gold standard” drugs morphine or gabapentin. “We don’t know about side effects yet, as it hasn’t been tested in humans. But we think it would be safe,” Dr. Craik said. “It acts by a completely different mechanism than morphine so we think it has a minimal possibility of producing the side effects of that medication. That is one of the big advantages of this drug.” It will likely be two more years before human testing can begin.