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Research reference — not for sale

Retatrutide

B
best evidence
Peptide
also called — retatrutide · LY3437943 · GLP-1 / GIP / glucagon triple agonist · "triple-G" · investigational (Eli Lilly). INCI: none
metabolicobesity / weighttype-2 diabetes (investigational)

Reference entry — NOT a sellable lane, and NOT approved anywhere. Retatrutide is the sharpest "demand-outruns-approval" case in the register: genuinely spectacular trial data, but an investigational drug with zero legal sellable pathway. The "research-use-only" retatrutide sold gray-market is unregu

In brief

Retatrutide is Eli Lilly's investigational triple GLP-1/GIP/glucagon agonist ("triple-G"), which in Phase 3 (TRIUMPH-1) produced the deepest weight loss of any obesity candidate to date (~28–30%). The evidence is genuinely strong and trending toward approval — but it is not approved anywhere, the Phase 3 programme is still completing, and the "research-use-only" retatrutide sold online is unregulated and not the studied product.

Legal standing, by region
International
See note

- Everywhere — investigational, NOT approved. No FDA, no EMA, no approved prescription pathway; all legitimate use is within Lilly's clinical trials. - Gray market: "research-use-only" retatrutide is widely sold but unapproved and unregulated — unknown purity, sterility, and dosing accuracy; it is not the trial compound. - This venture: not a sellable lane — an investigational drug; gray-market sa

Evidence, by outcome

An honest grade per outcome — drawn from the evidence, not any catalogue. Hype and undemonstrated marketing claims grade low.

OutcomeEvidence base · effectGrade
Weight loss (obesity)
Phase 3 topline is positive, but not yet approved; full peer-reviewed Phase 3 data + regulatory review pending
Phase 2 (NEJM 2023, 24.2%/48wk) + Phase 3 TRIUMPH-1 topline (28.3%/80wk) · Deepest weight loss of any obesity candidate to date
B
Type-2 diabetes glycemic control
Topline only; not approved
Phase 3 TRANSCEND-T2D-1 topline (≤2.0% A1C, ~16.8% weight, 40wk) · Strong
B
Hepatic fat / energy expenditure (the glucagon arm)
The arm neither semaglutide nor tirzepatide has; long-term effects still being characterised
Mechanistic + trial signals · Promising / distinguishing
C
Safety / long-term
Long-term and glucagon-arm safety being established in Phase 3; gray-market product safety is unknown
Phase 2/3 (incretin-class GI AEs, mostly mild-moderate on escalation) · GI-predominant

Identity a single engineered synthetic peptide that activates three receptors — GLP-1, GIP, and glucagon — once weekly. The first triple agonist to reach Phase 3. (Semaglutide is a GLP-1 mono-agonist; tirzepatide is a GLP-1/GIP dual agonist; retatrutide adds the glucagon arm.) ## Mechanism (as proposed) a single peptide acting as a triple agonistGLP-1 (appetite suppression, slowed gastric emptying) + GIP (insulinotropic, satiety) + glucagon (raises basal energy expenditure and reduces hepatic fat). Lilly attributes the unusually deep weight loss partly to adding glucagon agonism on top of the GIP/GLP-1 pathways.

Sources — 2 cited
01Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity — a Phase 2 trial. N Engl J Med. 2023.
02Eli Lilly — TRIUMPH-1 Phase 3 topline (21 May 2026); TRANSCEND-T2D-1 topline (19 Mar 2026); TRIUMPH programme design (Diabetes Obes Metab, 2026).
Review status
Not yet reviewed

A credentialed reviewer (PharmD / PhD / MD) will be named before this entry is finalised. Until then, treat it as a working draft. Last updated July 2026 (fast-moving — re-check TRIUMPH-2/-3 readouts and any regulatory filing).

Grades reflect the published evidence, not our interest. No dosing, reconstitution, or administration is published for research compounds — that restraint is deliberate.

Related compounds
SemaglutideA
Peptide
TirzepatideA
Peptide
CagrilintideB
Peptide
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Retatrutide (LY3437943) — evidence, "triple-G" status & the research-peptide reality · Vallydia