Triple Agonist

Triple Agonist

A triple agonist is a drug designed to activate three separate receptor pathways with a single molecule. In metabolic medicine, the term usually means molecules that target three key gut and pancreatic hormone receptors: GIP (glucose-dependent insulinotropic polypeptide), GLP-1 (glucagon-like peptide-1) and glucagon. Retatrutide (LY3437943) is the most advanced triple agonist in clinical development.

The idea builds on the success of single agonists (e.g., semaglutide, which targets GLP-1 alone) and dual agonists (e.g., tirzepatide, which targets GIP and GLP-1). Each added receptor pathway is thought to bring its own metabolic benefit. GLP-1 activity drives appetite suppression and blood sugar control. GIP activity affects fat tissue function and increases fullness. Glucagon activity raises energy use and promotes fat burning in the liver. Together, the three pathways may produce effects greater than the sum of their parts.

Designing one peptide that activates all three receptors well is a hard engineering problem. The natural hormones for the GIP, GLP-1 and glucagon receptors are structurally similar, because all three belong to the glucagon family of peptides. Eli Lilly researchers used this shared ancestry to build retatrutide’s peptide backbone, adding specific amino acid changes to get the right balance of strength at each receptor and to make the molecule last long enough for once-weekly dosing.

Data from retatrutide’s Phase 2 program suggest the triple agonist approach produces more weight loss and greater metabolic gains than reported for single or dual agonists, though head-to-head comparisons are needed to confirm this.