Retatrutide

About the name

GLP-3 is not a real hormone, receptor or drug class. It circulates as an informal nickname for retatrutide because the molecule is seen as the generational step after GLP-1 drugs and dual agonists. Peer-reviewed literature and regulatory filings use "retatrutide" or "triple agonist".

Mechanism

Retatrutide adds glucagon receptor agonism to the GIP and GLP-1 activity of a dual agonist. Glucagon signalling raises energy expenditure and promotes hepatic fat mobilisation, which is the proposed reason weight loss in trials exceeded that of dual agonists.

Clinical evidence

In the Phase 2 obesity trial published in the NEJM in 2023, participants on 12 mg lost a mean of 24.2% of body weight at 48 weeks. Phase 3 TRIUMPH results were published in 2026 (TRIUMPH-1 in the NEJM and TRIUMPH-2 in The Lancet, 29 September 2026), and Lilly plans a U.S. Biologics License Application in Q1 2027. As of 7 October 2026 retatrutide is not approved by any regulator.

Reported adverse events were predominantly gastrointestinal and dose-dependent, with cutaneous sensory effects reported at the highest dose.

Access

There is no prescription route for retatrutide while it remains investigational; outside clinical trials the only regulated pathway is a narrow, physician-requested expanded access programme (ClinicalTrials.gov NCT07629401). Vials sold online as "research chemicals" are unverified in identity, purity and sterility, and are not the same thing as trial material.