Read more: 鈥�Drugs with bite: The healing powers of venoms鈥�
DRUG: Captopril
SOURCE: Pit viper
CONDITION: Hypertension
How does deadly pit viper venom work as a drug? It鈥檚 all a question of quantity. 鈥淓very medicine is also a poison 鈥� the effect depends on the dose,鈥� says Bryan Fry, who researches venomous animals and their evolution at the University of Queensland in Brisbane, Australia. 鈥淭he snake kills by dropping its target鈥檚 blood pressure through the floor,鈥� he says. 鈥淭o use the venom as a drug, you just give less of it.鈥�
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Pit viper venom provided more than just the original venom-based drug, though. It is also intimately tied up with the discovery of how the body regulates blood pressure. In the late 1960s, this mechanism was still something of a mystery, confounding efforts to manipulate it. Among those working to understand it was John Vane, a pharmacologist at the Royal College of Surgeons of England. The breakthrough came when a Brazilian postdoctoral researcher, S茅rgio Ferreira, joined Vane鈥檚 group. Ferreira had been studying the venom of a pit viper native to Brazil, Bothrops jararaca, and he brought a sample of it with him. The team discovered that a toxic peptide in the venom would selectively inhibit the action of angiotensin-converting enzyme (ACE), a chemical suspected of playing a role in the regulation of blood pressure.
During the following decade, the role of ACE in boosting blood pressure by controlling the release of water and salts from the kidneys became clear 鈥� as did the therapeutic value of blocking it. Captopril, a synthetic analogue of the snake venom peptide, was first made in 1975, and hit the clinic just six years later. It was the founder member of what is now a family of ACE inhibitor drugs (Hypertension, vol 17, p 589).
Most of the venom-derived drugs approved since captopril also originated in snakes, mainly because snake venoms are the easiest to work with. Compared with a scorpion or a spider, say, snakes produce a vast volume of venom, making them easier to analyse. Snake venom is also a much simpler cocktail than that produced by many other animals: a spider鈥檚 venom can contain over 1000 peptides, whereas a snake鈥檚 venom might contain only 25.
