Retatrutide

Mechanism

In plain terms, retatrutide mimics several natural gut and pancreatic hormones at once to reduce appetite and food intake while affecting how the body handles glucose and energy. Technically, it is a synthetic peptide that simultaneously agonizes the glucose-dependent insulinotropic polypeptide (GIP) receptor, the glucagon-like peptide-1 (GLP-1) receptor, and the glucagon receptor. GLP-1 and GIP activity promote satiety and glucose-dependent insulin secretion, while glucagon-receptor agonism is thought to increase energy expenditure and lipid metabolism, a combination proposed to drive greater weight loss than single- or dual-incretin agents.

Regulatory Status by Region

• United States (FDA)Investigational; not approved. Phase 3 TRIUMPH program ongoing, with a first positive topline readout (TRIUMPH-4) reported in December 2025.
• Australia (TGA)Not entered on the Australian Register of Therapeutic Goods (ARTG); investigational only and not approved for supply.
• European Union (EMA)Not authorized; investigational, no marketing authorization.
• WADANot listed on the WADA Prohibited List. As an investigational incretin-class agent it is not a banned substance; the closely related approved GLP-1 agonists are on WADA's monitoring program rather than prohibited.

Key Studies

• Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial (Jastreboff et al.) (N Engl J Med 2023;389:514-526; DOI 10.1056/NEJMoa2301972; PMID 37366315)
• Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, phase 2 trial (Rosenstock et al.) (Lancet 2023; DOI 10.1016/S0140-6736(23)01053-X; PMID 37385280)
• A Study of Retatrutide (LY3437943) in Participants Who Have Obesity or Overweight (TRIUMPH-1, Phase 3) (ClinicalTrials.gov NCT05929066)