Orforglipron (revision 4)

Orforglipron (development code LY3502970) is an investigational orally administered non-peptide agonist of the GLP-1 receptor. It is not a peptide and is not subject to proteolysis, so it requires neither an absorption enhancer nor the strict fasting conditions that govern oral semaglutide.^[1]

Small-molecule agonism at a class B G-protein-coupled receptor was long considered difficult, because the natural ligand engages a large surface across two receptor domains.^[2] Orforglipron binds a pocket near the extracellular face of the transmembrane bundle and stabilises an active conformation without reproducing the peptide's binding mode.^[1]

The receptor's orthosteric peptide site is a poor target for a small molecule: the natural ligand contacts both the extracellular domain and the transmembrane bundle across a large interface, and a molecule of a few hundred daltons cannot reproduce that. Orforglipron instead occupies a pocket accessible from the extracellular face of the bundle and acts as an agonist by stabilising the same active receptor conformation by a different route.^[1]

A consequence is species selectivity. The pocket differs between human and rodent receptors sufficiently that activity does not translate, and preclinical work required humanised receptor models — a practical complication of small-molecule work at this target that peptide agonists do not face.