Retatrutide (LY3437943) is a triple GLP-1R, GIPR, and GCGR agonist; in vitro, it shows balanced GCGR and GLP-1R activity but greater GIPR activity (Coskun et al., 2022).[2] This triple agonist profile — "triagonist" — represents a pharmacological step beyond tirzepatide's dual GLP-1/GIP activity.
The Three Receptor Targets
GLP-1R agonism drives glucose-dependent insulin secretion, suppresses glucagon, slows gastric emptying, and activates hypothalamic satiety circuits.
GIPR agonism potentiates insulin secretion synergistically, promotes adipocyte lipid handling, and engages distinct hypothalamic satiety circuits.
GCGR agonism is the key addition. Glucagon receptor agonism drives energy-metabolism signaling via hepatic fatty acid oxidation and thermogenesis; promotes lipolysis in adipose tissue; and is studied for hepatic-lipid endpoints. When combined with GLP-1R agonism, the glucose-raising effect of glucagon is blunted by GLP-1's insulin-stimulating activity — neutralizing the hyperglycemic liability while preserving glucagon's thermogenic and lipolytic actions.
Phase 2 TRIUMPH Study Endpoints
In the referenced phase-2 study (Jastreboff et al., 2023, N Engl J Med), reported endpoints at 48 weeks included:
- Dose-dependent body-composition changes, with the highest-dose arm showing the largest change.
- Continued change in body-composition endpoints through the 48-week measurement point.
- Adverse events consistent with the incretin class; no unexpected safety signals.
Hepatic Effects and MASLD Research
GCGR agonism directly stimulates hepatic fatty acid oxidation and reduces de novo lipogenesis — a hepatic-lipid effect described as partly independent of body-composition change. In research terms this makes retatrutide notable for work on metabolic dysfunction-associated steatotic liver disease (MASLD) models.
References
- Jastreboff AM, et al. (2023). Triple–Hormone-Receptor Agonist Retatrutide for Obesity. N Engl J Med, 389, 514–526.
- Coskun T, Urva S, Roell WC, et al. (2022). LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept. Cell Metab, 34(9), 1234–1247.e9. PMID: 35985340. DOI: 10.1016/j.cmet.2022.07.013.
- Day JW, et al. (2009). A new glucagon and GLP-1 co-agonist eliminates obesity in rodents. Nat Chem Biol, 5(10), 749–757.
This article summarizes publicly available research for educational purposes and does not constitute medical advice, a therapeutic claim, or a recommendation for human use. Products referenced are sold for laboratory research use only.