Which venomous lizard's venom is the source of the diabetes drug exenatide?

The Gila monster is the venomous lizard whose venom supplied the peptide that led to the diabetes drug exenatide. Exenatide is a synthetic version of exendin-4, a 39-amino-acid peptide originally isolated from Gila monster venom.

The discovery began with research into why this slow-moving desert lizard can eat only occasionally. In 1992, endocrinologist John Eng isolated exendin-4 from the lizard’s venom. In diabetic mice, it lowered blood glucose for much longer than human GLP-1, a hormone with a very short half-life. That durability made the lizard peptide a promising drug template.

Exenatide activates GLP-1 receptors, helping stimulate insulin release when glucose is elevated, reduce glucagon secretion, and slow stomach emptying. The U.S. Food and Drug Administration approved it in 2005 as Byetta for type 2 diabetes. A common mix-up is the Mexican beaded lizard: it is a close venomous relative, but the named source of exendin-4—and therefore exenatide—is the Gila monster.