Overview
Retatrutide (LY3437943) is a once-weekly synthetic peptide and the most-advanced "triple G" agonist in development. A single molecule activates all three of GLP-1R, GIPR, and GCGR. As of 2026 it remains investigational, with peer-reviewed phase 2 obesity data and company-reported phase 3 readouts in type 2 diabetes; no marketed label exists yet.
Mechanism
Lilly's discovery work describes retatrutide as balanced at GCGR and GLP-1R with greater activity at GIPR. Subsequent structural and pharmacology work shows that relative to native ligands it is more potent at GIPR and somewhat less potent at GLP-1R and GCGR. The design intent is to combine GLP-1-mediated appetite suppression and glucose lowering, GIP-mediated insulinotropic effects, and glucagon-mediated increases in energy expenditure into a single agonist with weight-loss efficacy beyond what dual agonists achieve.