Retatrutide
First-in-class triple agonist engaging GIP, GLP-1, and glucagon receptors; the glucagon component is hypothesized to drive additional energy expenditure beyond incretin-only agents.
Retatrutide is a synthetic 39-residue peptide engineered as a balanced agonist of three receptors: the glucose-dependent insulinotropic polypeptide (GIP) receptor, the glucagon-like peptide-1 (GLP-1) receptor, and the glucagon receptor. The molecule extends the dual-agonist concept pioneered by Tirzepatide (GIP+GLP-1) by adding controlled glucagon-receptor engagement, with the rationale that glucagon’s hepatic and energy-expenditure effects can complement incretin-driven appetite reduction.
Mechanistically, the glucagon component is the most novel and the most carefully calibrated element. Excess glucagon agonism would raise blood glucose, but in the presence of strong GLP-1 insulinotropic activity, the net glycemic effect remains favorable while the metabolic-rate effects of glucagon are retained. Reported phenotypes in clinical trials include sustained reductions in body weight that exceed those observed with Tirzepatide at comparable trial durations, alongside improvements in hepatic steatosis and a generally favorable cardiometabolic profile.
Retatrutide is currently in late-stage clinical trials for obesity and type 2 diabetes (Eli Lilly’s TRIUMPH program). It is not yet approved by any regulatory body and is cataloged here as a representative entry in the emerging triple-agonist class.