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An experimental drug made from snail venom has shown early signs of promise in numbing
pain, raising hopes in the hunt for new, non-addictive medications, researchers said Sunday. The
drug, which has not been tested yet on humans, was judged to be about 100 times more potent
than morphine or gabapentin, which are currently considered the gold standard for chronic nerve
pain. The active ingredient, conotoxin, comes from
carnivorous cone snails, which are common in the western Pacific and Indian Ocean.
The marine animals can reach out and stab prey, injecting a venom that paralyses fish
long enough for the snail to eat it up. A tiny protein derived from the snail's venom
has formed the basis of five new experimental compounds, said lead researcher David Craik
of the University of Queensland in Australia. A preliminary study using one of these new
compounds on lab rats "appeared to significantly reduce pain," said a press statement released
ahead of Craik's presentation at an American Chemical Society meeting in Dallas, Texas.
"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 Craik. Animal venoms are poisons that
can block certain channels in the nervous system, and act differently than opioid painkillers
such as morphine and hydrocodone, which carry the risk of addiction and death from overdose.
Pharmaceutical companies have begun investigating venoms in recent years as potential sources
of new drugs for managing neuropathic pain, which affects 15 per cent of the US population
and can arise from cancer, AIDS, diabetes, and other debilitating diseases. One conotoxin-derived
drug, ziconotide, has already been approved for human use. However, it is not available
in pill form and must be infused directly into the lower part of the spinal cord. The
five new compounds Craik and colleagues are developing would be taken orally. "We don't
know about side effects yet, as it hasn't been tested in humans. But we think it would
be safe," Craik said, adding that human trials are at least two years away.