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Scientists have developed a new pain-relief pill from a chemical used by sea snails to catch their prey.

It was found to be as effective as morphine for relieving the most severe forms of pain but without the added risk of addiction.

Marine cone snails produce a saliva that contains a deadly dose of peptide toxins to help the slow-moving creatures catch prey. They inject passing victims with needle-like teeth that shoot out of their mouths.

Scientists have already transformed one of the chemicals into a pain-reliever for humans. However, it has to be injected directly into the spinal cord which limits how much it can be used.

Now researchers in Australia, led by David Craik of the University of Queensland, have developed a form of the painkiller that can be taken orally.

The modified chemical was found to reduce severe pain in rats at a much lower dose than existing medications, according to an article in Chemical & Engineering News.

‘For years people have been saying that peptides make fantastic drug leads because they’ve very potent,’ Professor Craik told the magazine.

However, peptides were regarded as poor drugs as they were not stable and could not be taken orally.

This could be set to change, after the team led by Professor Craik, found they could stabilise the amino-acid chains by synthetically lashing the head to the tail.

‘All you need is for the ends to be roughly close to one another,’ he said.

The drug could potentially revolutionise the treatment of the most severe forms of pain and Professor Craik is keen to take his research further.

Colourful cone snails are some of the most venomous creatures on the planet. But the powerful poisons they produce can, in tiny doses, help to reveal how nerve cells function — and potentially help to treat conditions from epilepsy to, as in today’s case, chronic neuropathic pain that is thought to affect up to eight per cent of the world’s population.

Hopes of a treatment have been raised by research on two species of cone snail that eat worms: Conus regius, which measures up to three inches in length and lives from Georgia southward along Central America to Brazil’s central coast; and the second is the similarly sized Conus victoriae, which lives off Australia.

The toxins named RgIA and Vc1.1 from snail venom can treat nerve hypersensitivity and pain according to University of Utah scientists. “It is a previously unrecognised mechanism for treating pain,” said Prof Michael McIntosh, one of the team that reports the finding today in the Proceedings of the National Academy of Sciences.

“Numerous analgesic compounds currently available are largely ineffective” for chronic nerve pain, Prof McIntosh and colleagues write. The team not only reveals a previously unrecognised molecular mechanism for the treatment of neuropathic pain but the involvement of a protein, called the alpha9 alpha10 nicotinic receptor – in nerve injury.

Vc1.1, also known as ACV1, was found by University of Melbourne scientist Prof Bruce Livett and is being developed by an Australian company, Metabolic, and is undergoing trials in human patients.

Prof McIntosh added that he hopes the new findings also make it feasible to develop a painkiller based on RgIA that could be taken orally, but he believes that will take around a decade.

The study dealt with what is known as neuropathic pain, which is chronic pain due to injury to the nerves, spinal cord or brain. Such pain can result from diabetes damage to nerves in the feet or elsewhere, spinal injury, degenerative disc disease, alcoholism, failed low-back surgery, tumours compressing nerves, spinal tumours, repetitive motion disorders, multiple sclerosis, infection, stroke, traumatic brain injury, shingles, nerve toxins and electrical or other damage to peripheral nerves.

Symptoms can include numbness and pain that feels like constant burning, “pins and needles,” sharp shooting pain, electricity or electrical shock, or tingling. People with neuropathic pain often are hypersensitive to previously innocuous stimuli – for example, feeling pain from a foot rubbing against the inside of a shoe – and feel an exaggerated response to things that are painful.

Common pain medicines like aspirin, ibuprofen and paracetamol often fail to relieve neuropathic pain. Morphine-like drugs such as oxycodone sometimes are used, but can cause constipation, nausea and a spaced-out feeling.

“There really is no highly effective treatment available for this kind of severe pain, so having a new way to treat it is exciting,” Prof McIntosh says. If the new discovery eventually leads to a new pain drug that is combined with existing treatments, “you may be able to reduce the pain to a lower level than ever before.”

Researchers have also identified a natural painkiller produced in humans, termed opiorphin, which is several times as potent as morphine in pain studies in rats, according to a second study in the same issue of PNAS. Catherine Rougeot of the Institut Pasteur, Paris, and colleagues had recently identified a potent pain sensation inhibitor in rats called sialorphin and wondered whether humans also secrete a similar compound. The researchers successfully isolated opiorphin from human saliva that works in the same way. The analgesic properties of opiorphin warrant further study, they report.

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