Your Next Painkiller Could Come From A Snail : Shots - Health News The drug derived from the venom of cone snails must be injected into the spinal column to get beyond a patient's blood-brain barrier and bring relief. But scientists think they may have a workaround.

Snail Venom Yields Potent Painkiller, But Delivering The Drug Is Tricky

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MELISSA BLOCK, HOST:

Researchers are increasingly turning to nature for inspiration for new drugs. One example is Prialt. It's an incredibly powerful painkiller that people sometimes turn to when morphine no longer works. Surprisingly, the active ingredient in Prialt is based on a component in the venom of a marine snail. As part of his project Joe's Big Idea, NPR's Joe Palca tells the story of a scientist in New York who's trying to make Prialt a better drug.

JOE PALCA, BYLINE: Prialt wasn't on Mande Holford's mind when she began her career in chemistry. No, she wanted to study peptides. These are short strings of amino acids that do things inside cells.

MANDE HOLFORD: I started out with this love for peptides - love (laughter). It sounds weird to say you love peptides out loud.

PALCA: And then when she was in graduate school, a visiting scientist gave a lecture about the peptides in snail venom.

HOLFORD: He had this amazing video of a snail eating a fish. And it just looked so crazy.

PALCA: Holford was captivated. How could a snail eat a fish? Well, it's got this powerful venom it uses to paralyze the fish.

HOLFORD: Snails are just so cool. I mean, it's amazing. If you haven't seen a snail eat a fish, you will become converted when you do.

PALCA: Now, it turns out this venom is made of a hundred or more different peptides. Most of them aren't very good for you.

HOLFORD: If I were to inject you with a complete cocktail of cone snail venom, it would kill you.

PALCA: But Holford says one particular peptide in the venom is able to do something medically useful. It dramatically reduces pain. In 2004, the FDA approved the drug Prialt, made from a synthetic form of the peptide. Right now, Prialt is only used in cases of extreme unrelenting pain because there's a major problem with Prialt.

HOLFORD: It doesn't cross the blood-brain barrier.

PALCA: The blood-brain barrier is a kind of membrane that prevents most compounds in the blood from entering the brain. If Prialt doesn't get into the brain, it can't ease pain. So the peptide drug Prialt has to be administered intrathecally. It's a great word. It means directly into the spinal cord. Holford has been looking for a way around that.

HOLFORD: We're using what I like to call our Trojan horse strategy in which we put the peptide inside of a carrier, which is called, in this case, a viral nanocontainer.

PALCA: This is a tiny receptacle made from proteins found in viruses.

HOLFORD: And then we sort of shuttle it across the blood-brain barrier using another peptide, which is a cell-penetrating peptide which can cut through all kinds of membranes, including the blood-brain barrier.

PALCA: As Holford and first author Prachi Anand write in the current issue in the journal Scientific Reports, the system seems to work in lab models of the blood-brain barrier. If her Trojan horse idea stands up to further testing, it would be possible to inject the drug, or maybe someday just take it as a pill. But there's still a lot to do before Holford and her colleagues will know if that's really possible.

HOLFORD: The next step is to figure out if the peptide is still functional once we get it across the blood brain-barrier.

PALCA: In other words, whether it still works as a painkiller once it's delivered with Holford's Trojan horse. I'll report back when they've figured that out. Joe Palca, NPR News.

BLOCK: And if you want to be converted by watching a video of a cone snail eating a fish, go ahead and watch. It's on our website, npr.org.

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