Retatrutide
Retatrutide (LY3437943) — evidence, "triple-G" status & the research-peptide reality

Class: peptide
Synonyms: retatrutide
LY3437943
GLP-1 / GIP / glucagon triple agonist
"triple-G"
investigational (Eli Lilly). INCI: none
Function tags: metabolic
obesity / weight
type-2 diabetes (investigational)
Overall evidence grade: B
WADA prohibited: no
WADA note: Sport: an investigational incretin-class agent; not a listed performance category, but athletes under testing should verify current status.
Last updated: 2026-07-13

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.

## 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 agonist** — **GLP-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.

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

Legal status:
region: INT
status: See note
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 sale is illegal and unsafe.
- Sport: an investigational incretin-class agent; not a listed performance category, but athletes under testing should verify current status.

Cosmetic claims:

Note: 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 unregulated and is not the trial compound. No dosing published here.
Status note: fast-moving — re-check TRIUMPH-2/-3 readouts and any regulatory filing

Sources:
Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity — a Phase 2 trial. N Engl J Med. 2023.
Eli Lilly — TRIUMPH-1 Phase 3 topline (21 May 2026); TRANSCEND-T2D-1 topline (19 Mar 2026); TRIUMPH programme design (Diabetes Obes Metab, 2026).