The Healing Power of Venom
Scientists are turning toxins from scorpions, snakes and spiders into treatments for diseases including diabetes and cancer
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Scorpions to help us fight cancer? It isn’t as crazy as it sounds. Scientists are at work on a “tumor paint” known as BLZ-100, derived from scorpion venom. The paint, which started its Phase I clinical trial for children’s brain tumors last year, is based on a toxin that causes rapid paralysis in insects, the scorpion’s usual prey. But in mammals, the toxin binds to chloride channels found in tumor cells. By linking the toxin to a fluorescent dye, doctors can see and remove an entire cancerous mass, reducing the likelihood of relapse.
Scorpions and other animals that deploy toxins to survive are becoming increasingly important allies in humanity’s fight against ailments ranging from cardiovascular disease to diabetes and cancer. Whether it is sea-anemone venom tackling autoimmune disorders, tarantula venom attacking muscular dystrophy or centipede venom alleviating excruciating pain, scientists are finding the lifesaving potential in species that are feared for their painful, sometimes deadly stings.
Humans have been toying with this idea for centuries. One of the earliest treatments for ailments from gout to baldness was apitherapy, the medical application of bee venom, which was used in ancient Greece, China and Egypt. The ancient Greeks associated snakes and their venoms with medicine through the god Asclepius, whose followers prescribed venoms as cures and whose staff had a snake wrapped around it—the inspiration for the well-known symbol of medicine today.
Even so, scientists have only recently started to intensively explore the healing powers of venom. “In the 1980s and ’90s, people weren’t saying, ‘We should use venoms as a drug source,’ ” says Glenn King, a biologist at the University of Queensland in Brisbane, Australia. That changed at the beginning of this century: Scientists started to look at venoms as “complex molecular libraries,” he says. The bodily mechanisms that venoms derail often turn out to be the same ones that we need to manipulate to cure deadly diseases.
Naturally occurring venoms already do what we need man-made drugs to do: target and modulate key molecules in our cells. Just like pharmaceuticals, venoms can alter core physiological processes that are disrupted by diseases. By controlling the dosage or slightly altering the chemical composition, scientists can turn toxins into treatments.
Consider patients with intractable pain or other neurological conditions. They need something that will stop the relentless firing of neurons—and neurotoxic venoms, found naturally in many snakes and spiders, can shut down neurons in their intended prey. Databases like VenomKB allow researchers to search through hundreds of thousands of compounds to find ones that may have health benefits.
Chemical engineers have taken to mining living organisms, fine-tuning their chemicals to be more potent and precise. This process, known as bioprospecting, has had increasing appeal for scientists eager to tackle incurable diseases. Bioprospecting involves selecting a species with a type of venom known to have a specific effect on the human body—say, a snake with venom that causes a steep drop in blood pressure. The scientists will adjust the level of the toxin or tweak it biochemically so that it becomes not harmful but therapeutic.
It can takes years—even decades—to go from discovery to market, Dr. King says. A half-dozen solely venom-derived drugs are available now, and they are both lifesaving and lucrative. The trend started with Captopril, pulled from the venom of the Brazilian jararaca viper, which was known to cause life-threatening low blood pressure. This blockbuster drug has raked in billions of dollars since its release in 1981 and transformed the treatment of high blood pressure—saving more lives in a few decades than the viper and its relatives have taken over many centuries.
Captopril paved the way for more venom bioprospecting. One notable example is Byetta, a type-2 diabetes drug derived from the venom of the Gila monster.
The lizards—shy, slow, mottled creatures that live in Arizona and New Mexico—have in their venom a compound called exendin, which was discovered in the early 1990s by an endocrinologist named John Eng. He developed a synthetic version of the compound, exendin-4, and licensed it to the pharmaceutical firm Amylin, which later partnered with Eli Lilly on the resultant drug. Byetta won approval from the U.S. Food and Drug Administration in 2005.
The synthetic molecule mimics a hormone that encourages digestion and insulin production. That hormone stimulates insulin release only in the presence of high blood sugar—so unlike regular insulin injections, there’s no accidental hypoglycemia (or low blood sugar) from an excess of insulin. More important, the venom-derived synthetic molecule lasts for hours, unlike the human form of the molecule, which gets chopped up within minutes in the body.
The popularity of Byetta triggered a battle among drug companies. First came a similar product named Victoza (developed by Novo Nordisk), followed by, among others, an extended-release version called Bydureon (from Eli Lilly and Amylin), then GlaxoSmithKline’s Tanzeum and Eli Lilly’s Trulicity in 2014. (Byetta and Bydureon are now the property of AstraZeneca.)
The drugs haven’t been a panacea. The FDA announced in 2013 that it was “evaluating” reports suggesting they might increase the risk of inflammation of the pancreas and precancerous cell changes. Still, none of these widely prescribed diabetes drugs would exist if it weren’t for the Gila monster. And scientists with the National Institute on Aging have noticed that exendin-4 doesn’t just work on the pancreas; it stimulates neuron growth, which may mean that the Gila-monster peptide might one day help people with early stage Alzheimer’s or mild cognitive impairment.
The drugs haven’t been a panacea. The FDA announced in 2013 that it was “evaluating” reports suggesting they might increase the risk of inflammation of the pancreas and precancerous cell changes. Still, none of these widely prescribed diabetes drugs would exist if it weren’t for the Gila monster. And scientists with the National Institute on Aging have noticed that exendin-4 doesn’t just work on the pancreas; it stimulates neuron growth, which may mean that the Gila-monster peptide might one day help people with early stage Alzheimer’s or mild cognitive impairment.
Cancer is a natural target, and treatments may be lurking not just in scorpion venom but in the venoms of bees, snakes, snails, and even mammals. A compound derived from venomous shrews concluded a Phase I trial last year. This innovative peptide blocks a calcium channel called TRPV6, which is abundant in cancer cells, starving them of an essential element needed to grow and divide.
How about less life-threatening complaints, like erectile dysfunction? A compound in the venom of the Brazilian wandering spider might help. Crow’s feet? Bee venom might be better than Botox, according to a South Korean biologist (and Elle magazine). The venom of black widow spiders may even contain a spermicide, which seems fitting (when you eat your lovers after sex, you get a certain reputation).
Each venomous animal is an artisanal mixologist, crafting chemical cocktails that can contain thousands of ingredients. The wealth of potential in venoms—each with its unique recipe—is hard to overstate. That is yet another reason to preserve our planet’s endangered ecosystems: If venomous species become extinct, millions of lifesaving drugs may slip through our fingers.
—Dr. Wilcox is the author of “Venomous: How Earth’s Deadliest Creatures Mastered Biochemistry,” to be published Aug. 9 by Scientific American/Farrar, Straus and Giroux.
Corrections & Amplifications
The diabetes drug Byetta resulted from John Eng’s licensing of a compound he discovered to the pharmaceutical firm Amylin, which later worked with Eli Lilly on the resultant medication. An earlier version of this article incorrectly said Dr. Eng had sold the compound to Eli Lilly. (July 25, 2016)