conotoxin

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Scientists have uncovered a surprising reason to value cone snails: their deadly conotoxins are inspiring the next generation of painkilling medicines. Because as well as blocking nerve signals to paralyze prey, conotoxins also block nerves that transmit pain: cone snails numb their victims before eating them.

Ziconotide, or Prialt, is a painkiller derived from the magician’s cone snail (Conus magus). It’s highly effective in treating chronic pain: it’s at least 100 times more potent than morphine, working in very low doses and without the risk of addiction.

But there is a drawback: Prialt needs to be injected directly into the spinal cord via a small pump worn by the patient. The problem with making a conotoxin-inspired painkiller in tablet form is making the peptides stable enough so they don’t break down in the stomach before reaching their target.

Recently, David Craik and his team from the University of Queensland in Australia think they’ve cracked the problem by engineering a synthetic conotoxin molecule and adding some extra amino acids. This transforms the peptide into a ring making it more stable.

“The peptide work performed by the Craik group is truly pioneering and represents plausible steps towards both classical and novel types of therapeutics in the future,” says Johan Svenson, a senior scientist at the SP Technical Research Institute of Sweden, who was not involved in the research. “The diverse bioactivities displayed by these natural peptides makes them a rich source of starting material in the search for new drugs against a range of disorders currently poorly managed.”

One of the major hurdles for the development of peptide-based drugs is the cost of production. Many plants, including sunflowers, naturally produce orally-stable cyclic peptides. In a bit of ‘blue sky’ thinking, Craik suggested that one route to production could be by creating edible plant-based formulations.

While there are a lot of potential hurdles for these products, such as understanding how to manage dosing levels for foods, determining how cooking methods could affect the therapeutic effects, or managing the complex regulatory challenge, Craik suggested that these potential functional foods could offer hope for people with chronic pain who need long-term treatment.

These patients are underserved by current drugs, he said, which can have a range of sedative side effects, and may only help 30–40% of patients. Plant-based production methods are also cheaper, which could improve access to drugs for low-income markets.

Other pharmaceutical treasures could lie inside cone snails. Conotoxins have already shown potential in treating Parkinson’s disease, strokes and epilepsy. However, many of these future cures could disappear before they’re found. Most cone snails live in coral reefs and mangrove forests, two of the most threatened habitats on the planet due to climate change, overfishing and coastal development. The extraordinary cone snails are just one group of animals that would be an immense loss if they were to fade away.

--Wikipedia
--The Pharmaceutical Journal, 12 MAR 2015
--Chemistry World, 8 January 2014

July 7, 2015