National Geographic : 2013 Feb
venom 79 “It’s designed to cover both things.” The closely related black mamba, a snake whose open mouth resembles a coffin and whose venom can quickly put you in one, holds a toxin with huge potential to be a powerful new painkiller. Gila monsters, pebbly-skinned lizards found in the deserts of the U.S. Southwest, eat as few as three big meals a year (storing fat in their tails for the long wait), but their blood sugar remains stable. In 1992 an endocrinologist named John Eng at the Bronx/James J. Peters VA Medical Center in New York identified a component in Gila venom that controls blood sugar and even reduces appetite. Exenatide, a drug derived from the venom in their saliva, works like a natural hormone, stimulating cells to deal with sugar overload but remaining inactive when sugar lev- els are normal. It even helps diabetics produce their own insulin and lose weight. With almost 25 million people suffering from type 2 diabetes in the U.S. alone, the Gila monster is nothing short of a medical superhero. Venomous mammals, though rare, are in the game. The current drug for ischemic stroke victims works only if administered within three hours. A drug based on an anticoagulant toxin in the saliva of the vampire bat is now in clinical trials and would extend the time to nine hours. Even some arthropods are skittering down the venom-to-medicine track. Recall Michael’s run- in with the scorpion in Mexico. Takacs, in what may be his first Designer Toxins breakthrough, is investigating a novel toxin fused from the venoms of three different scorpion species that selectively blocks immune T cells, implicated in numerous autoimmune diseases. Several drug companies are also pursuing this lead. Meanwhile, a neurotoxin from the venom of the giant deathstalker scorpion has been found to attach to the surface of brain cancer cells. The overwhelming reason tumors come back is that surgeons can’t reliably distinguish good cells from bad at the growths’ edges. Magnetic resonance imaging—the best available diagnostic tool—doesn’t detect masses smaller than about a billion cells. This means surgeons have to find the boundaries between tumors and healthy tissue “purely by visual and textural cues,” says James Olson of the Fred Hutchinson Cancer Re- search Center in Seattle, Washington. “It’s a very imperfect science. Glioma cells weave into nor- mal tissue, and pieces sometimes get left behind.” Doctors who treat glioma, the most com- mon form of brain cancer, created a “molecu- lar flashlight” by marking chlorotoxin with a near-infrared dye. On the very first trial, Olson says, the “tumor paint,” as he calls the scorpion- derived marker, “lit up the cancer beautifully. We were literally jumping up and down because we knew what incredible potential this had.” The paint reveals masses with as few as 200 tumor cells. “You can truly see the tumor almost cell by cell,” Olson says. “This will let surgeons get more cancer out, maybe even 100 percent.” Hu- man trials on the dyed toxin will start later this year, and if tests go well, the paint could be used for prostate, colorectal, lung, breast, pancreatic, This cobra, known to spit its venom, is one of numerous snakes farmed in concrete bunkers in le Mat Village, Hanoi. Cobras in Vietnam and many other snakes are traded within southeast asia for consumption. Venom-based cures aren’t new. They show up in Sanskrit texts from the second century.