Take One Snail And Call Me In The Morning...continued
A Drug Tailor-Made For Humans
Olivera had initially focused on fish-eating rather than worm-eating snails because he hoped that toxins designed to hit certain vertebrates (fish) would also work on mice and humans.
But ziconotide doesn’t kill humans precisely because it doesn’t fit this pattern. In fish, ziconotide causes paralysis by blocking nerve to muscle communication, but mammals have evolved calcium channels at the nerve-muscle junction that are insensitive to ziconotide. As George Miljanich, senior director of biochemistry at Neurex, says, "lucky for pain sufferers, and for Neurex."
The one place that ziconotide binds in the human spinal cord is the part that is used for sending pain signals. Clinical trials of ziconotide for pain were completed in 1998, and Neurex expects to file a new drug application soon.
The drug is delivered directly to the spinal cord using a pump developed by Medtronic, Inc. (Minneapolis, Minnesota). The pump is the size of a hockey puck, and is implanted in the chest and refilled by syringe. A pump is more cumbersome than a pill but, Miljanich says, "hundreds of thousands of patients suffer chronic, otherwise intractable pain, and tens of thousands already have intra-spinal morphine."
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