Relief could be on its way for people suffering from types of pain that is poorly treated by current drugs. Hope rests with a chemical found in the toxins used by marine snails to subdue their prey. Sadly, though, there is a long way to go before a product hits the market. Anyone anxiously awaiting relief from chronic suffering may wonder if the development is taking place at a speed set by the snails themselves.
The poisons and venoms of the animal kingdom represent some of the richest stores of biologically active chemicals we know, and have inspired some of our most important drugs. Sometimes this is because we are in need of a more subtle version of the role the chemicals play in nature; vipers help subdue their prey through drastic drops in blood pressure, leading to captopril a world-changing drug in an era when hypertension endangers millions.
However, Dr. Richard Clark of the University of Queensland doesn't think the cone snail Conus victoriae, endemic to Australia, is out to give its prey a painless death. “It feeds on fish and worms,” he told IFLScience. “The fact that it has a pain relief effect on humans is probably coincidental.” Nevertheless, studies that broke the snails' venom into its constituent parts suggested that some of them might block pain transmission in mammals, inspiring Clark to investigate further.
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“Translating the venom’s toxins into a viable drug has proved difficult,” Clark said in a statement. “But now we’ve been able to identify a core component of one of these conotoxins [toxins from cone snail venom] during laboratory tests. We think this will make it much easier to translate the active ingredient into a useful drug.”
In Angewandte Chemie International Edition, Clark has described techniques for synthesizing the target molecule. “We can do in 2-3 days what used to take weeks,” he told IFLScience. “This has cut down the time it takes to develop it further, and will hopefully reduce the cost when we are ready for mass production.”
The reason Clark and his colleagues have devoted so much effort to the conotoxin is that it could fill a gap in the pain relief market. Different forms of pain require the blocking of different receptors. Clark said that current drugs only offer relief to 50-70 percent of the sufferers of the neuropathic pain the conotoxin blocks. Of these, most gain only partial escape from their suffering.
“Using a laboratory rat model, we used the modified conotoxin to successfully treat pain generated in the colon, similar to that experienced by humans with irritable bowel syndrome,” Clark said. “Although the conotoxin has been modified, its pain relief properties remained as effective as the full-size model.”
Nevertheless, Clark told IFLScience that further modifications would need to be made to the molecule to make it stable enough for human use, even before clinical trials can start. Consequently, even on the most optimistic timeline it will be 5-7 years before many people will gain any benefit.