RUO onlyMetabolic

Retatrutide

LY3437943 / Triple G / GLP-1/GIP/Glucagon triple agonist

A triple receptor agonist targeting GLP-1, GIP, and glucagon receptors simultaneously. Developed by Eli Lilly. Phase 2 data showed up to 24.2% body-weight reduction at 12mg over 48 weeks — exceeding semaglutide and tirzepatide in early comparisons. Phase 3 TRIUMPH trials ongoing. Most legally sensitive GLP-1 adjacent compound in the current market — Eli Lilly has actively pursued legal action against vendors selling it as RUO.

Evidence

Human data exists

Routes

injectable

Available since

Developed by Eli Lilly. Phase 2 data published 2023. Phase 3 TRIUMPH program ongoing as of 2026.

Mechanism of action

Activates three complementary metabolic receptors simultaneously. GLP-1 receptors drive insulin secretion and appetite suppression. GIP receptors enhance insulin response and fat metabolism. Glucagon receptors increase energy expenditure and hepatic fat metabolism. The triple mechanism targets metabolic dysfunction through more pathways than any currently approved drug. Once-weekly subcutaneous injection with extended half-life formulation.

Effects in the body

Phase 2 data showed 24.2% average body-weight reduction at 12mg over 48 weeks — the highest reported in any metabolic peptide trial to date at time of publication. Phase 3 TRIUMPH trials are ongoing as of 2026. Dr. Abud Bakri discussed retatrutide on the Huberman Lab podcast (June 1, 2026) covering its triple receptor mechanism and how drug patents and nomenclature work in the GLP-1 space. Eli Lilly has actively pursued legal action against vendors and compounding pharmacies selling this compound under RUO or research-use disclaimers — making it the highest-risk GLP-1 compound from a regulatory exposure standpoint.

Pros & cons (from the literature)

Pros

Triple receptor mechanism targeting GLP-1 GIP and glucagon simultaneously
Phase 2 data showed 24.2% weight reduction — highest reported in any metabolic peptide trial to date
Developed by Eli Lilly with active Phase 3 TRIUMPH program
Once-weekly dosing
Potential for greater efficacy than tirzepatide based on early comparative data

Cautions

Not FDA approved — Phase 3 trials still ongoing as of 2026
Eli Lilly has actively filed federal lawsuits against vendors and compounding pharmacies selling this compound
FDA issued warning letters to multiple vendors marketing retatrutide under RUO disclaimers
RUO market versions have no pharmaceutical quality controls
Long-term safety profile unknown — Phase 3 data not yet complete
Highest legal risk of any metabolic compound currently available through research vendors

Protocol summary (from published research)

Phase 2 trial used escalation from 1mg to 8-12mg weekly subcutaneous injection over 24 weeks. No established research protocol outside clinical trial settings. Extreme caution warranted given active regulatory enforcement and incomplete safety data.

Dosing ranges reproduced from published research literature. Not a prescription, not medical advice.

FDA & regulatory status

Research Use Only. Not FDA approved. Importantly: Eli Lilly (retatrutide's developer) has actively pursued federal legal action against compounding pharmacies and vendors selling this compound under research-use-only disclaimers. The FDA has issued warning letters to multiple vendors. This is among the most legally sensitive compounds in the current research peptide market. Phase 3 FDA filing expected 2026-2027. Researchers should understand this regulatory and legal context fully before sourcing.

Evidence base

Phase 2 RCT published showing 24.2% weight reduction at 12mg. Phase 3 TRIUMPH trials ongoing. No completed Phase 3 data available as of 2026. Active enforcement environment around this compound.

Primary research sources

Peer-reviewed literature referenced throughout this profile is drawn from PubMed, Cell Metabolism, and clinical trial registries cited in the evidence base above.

Important. ThePeptide.expert summarizes published research. We are not a pharmacy, do not prescribe, and make no therapeutic claims. Regulatory status varies by jurisdiction.