Leptin discovery (1994-2005)
Jeffrey Friedman's lab cloned the ob gene and showed leptin injections reversed obesity in mice, raising hopes of a human weight-loss cure.
Human trials showed leptin only worked for rare leptin-deficient individuals; most obese people were leptin-resistant.
A well-documented case of a mouse mechanism that did not generalize to the broader human condition.
A reminder that a mechanism proven in mice does not always scale to humans.
