What Is Retatrutide?
Retatrutide (also known by development code LY3437943) is an injectable peptide developed by Eli Lilly that simultaneously activates three receptors: GLP-1, GIP, and glucagon. This triple mechanism sets it apart from all currently approved medications, which target at most two of these pathways. It is currently in Phase 3 clinical trials.
The Phase 2 Results
Phase 2 trial results for retatrutide, published in The New England Journal of Medicine in 2023, generated significant excitement. Participants taking the highest dose (12 mg weekly) lost an average of approximately 24% of their body weight over 48 weeks. At that pace, extrapolated to a longer treatment duration, the results approach what is achievable with bariatric surgery — which has historically been the only intervention capable of 25–30% sustained weight loss.
The Role of Glucagon Agonism
The key differentiator in retatrutide versus tirzepatide is the addition of glucagon receptor agonism. While glucagon typically raises blood sugar, activating glucagon receptors in the right context produces a powerful fat-burning effect. The GLP-1 and GIP components keep blood sugar in check while the glucagon component accelerates fat oxidation — a combination that appears synergistic rather than counterproductive.
Current Status
As of 2026, retatrutide is in Phase 3 trials examining its efficacy and safety in adults with obesity. If Phase 3 results confirm Phase 2 findings, an FDA submission could follow in the next one to two years.
Retatrutide is not yet available. Do not purchase products claiming to be retatrutide from compounding pharmacies or unregulated sources — they cannot legally or safely produce this compound in its clinical form.