Scientists Reveal How Tirzepatide Activates Two Hormone Receptors at Once — and Why Triple Agonists Could Be Even Better

Cryo-EM structures revealed how tirzepatide (dual GIP/GLP-1 agonist) and peptide 20 (triple GIP/GLP-1/glucagon agonist) achieve their multiplexed receptor activation. The structures showed both common and unique binding features at near-atomic resolution, explaining how a single peptide can effectively activate two or three different receptors. Key finding: retention of glucagon receptor function is required for the triple agonist to achieve advantages over GLP-1 monotherapy alone.

Cryo-electron microscopy was used to determine five receptor-peptide complex structures: tirzepatide bound to GIPR and GLP-1R, and peptide 20 bound to GIPR, GLP-1R, and GCGR. Structural analysis identified key binding interactions, conformational changes, and receptor-specific contacts that explain dual and triple agonism. Comparisons were made to monoagonist semaglutide's binding mode.

Tirzepatide is producing unprecedented weight loss and metabolic improvements in clinical trials, but how one peptide activates two different receptors was unclear. These structures provide the molecular blueprint for designing even better multi-targeting peptide drugs — and reveal that triple agonism (adding glucagon activity) may be the next frontier beyond tirzepatide.

Multi-receptor peptide agonists represent the cutting edge of metabolic drug design. Tirzepatide's dual agonism has already produced clinical results superior to semaglutide, and this structural work shows why: the peptide adopts different binding conformations at each receptor. The revelation that triple agonism (adding glucagon) provides additional benefits has catalyzed development of several triple agonist peptides now entering clinical trials. These structures are essentially the instruction manual for designing the next generation of metabolic peptide drugs.

Structural biology study — structures represent snapshots of receptor-peptide complexes that may not capture the full dynamic signaling process. The clinical implications of specific structural features are inferred rather than directly demonstrated. Peptide 20 is a research compound, not yet in clinical development. Structures were determined in detergent/nanodisc conditions that differ from native cell membranes.