THE GILA monster is a poisonous North American lizard that measures around 50 centimetres and sports a distinctive coat of black and orange scales. This lethargic reptile, which mostly dwells underground and eats just three to four times a year, is the unlikely inspiration for one of pharma’s biggest blockbusters: a new generation of weight-loss drugs that has patients—and investors—in a frenzy. Originally made for diabetes, evidence is growing that they also have benefits in diseases of the heart, kidney, liver and beyond.

Since the late 1980s scientists believed that a gut hormone called glucagon-like peptide-1 (GLP-1), which is secreted by the intestines after a meal, could help treat diabetes. GLP-1 increases the production of insulin (a hormone that lowers blood-sugar levels) and reduces the production of glucagon (which increases blood-sugar levels). But GLP-1 is broken down by enzymes in the body very quickly, so it sticks around for only a few minutes. If it were to be used as a drug, therefore, patients would have faced the unwelcome prospect of needing GLP-1 injections every hour.