Retatrutide[LY3437943; sometimes mislabelled 'GLP-3']
Compound snapshot
Class
Triple incretin receptor agonist (GLP-1 / GIP / glucagon)
FDA approved
No — investigational; Lilly plans a BLA submission in Q1 2027
Clinical development
Phase 3
Last reviewed
September 2026
Research areas
Body weight / Type 2 diabetes / Appetite regulation / Energy expenditure
Regulatory status
Investigational — Phase 3; not FDA-approved
Internet attention
Very high
Registry query
Retatrutide
A once-weekly investigational peptide developed by Eli Lilly that activates three hormone receptors at once: GLP-1, GIP and glucagon. The nickname 'GLP-3' is not scientifically accurate — it is a single peptide acting on three established receptors, not a new hormone class.
Reality check — what we actually know
Supported by human evidence
- Phase 2 (NEJM 2023): 24.2% mean weight loss at 48 weeks on 12 mg versus 2.1% on placebo
- Phase 3 TRIUMPH-1 topline (June 2026, company-reported): 28.3% mean weight loss at 80 weeks on 12 mg — awaiting peer review
- Phase 3 TRANSCEND-T2D-1 (The Lancet, 2026): A1C reduction up to 2.0% and up to 16.8% weight loss at 40 weeks in type 2 diabetes
- Phase 3 TRIUMPH-2 and TRIUMPH-3 topline (23 July 2026): up to 20.8% and 22.6% weight loss at 80 weeks; TRIUMPH-3 did not demonstrate a reduction in cardiovascular events
Animal research only
- Triple-receptor activation produces greater weight loss than single-receptor agonists in preclinical models
Mechanistically plausible
- GLP-1 and GIP receptor activation suppress appetite and support insulin signalling; glucagon receptor activation raises energy expenditure
Common internet claims
- "GLP-3 is the next-generation fat burner" — the nickname is not scientifically accurate
- "Side-effect free" — gastrointestinal effects are common in trials
Not established
- Long-term human safety and cardiovascular outcomes
- Approved indication — it is not an approved medicine for any use
- Safety of compounded or research-market products sold under this name
Evidence distribution
Each band is a live PubMed search for Retatrutide, filtered to that kind of study. Top is the strongest evidence; the base is reasoning, not proof. A band with no records means that kind of study has not been published for this compound yet.
Mechanism and reported findings
GLP-1 receptor activation suppresses appetite and slows stomach emptying; GIP receptor activation supports insulin and fat-tissue signalling; glucagon receptor activation raises energy expenditure. The triple combination is designed to reduce food intake while also increasing calories burned.
- In the Phase 2 trial published in the New England Journal of Medicine (2023), the 12 mg group lost a mean 24.2% of body weight at 48 weeks versus 2.1% with placebo
- Phase 3 TRIUMPH-1 (company-reported, June 2026): 28.3% mean weight loss at 80 weeks on 12 mg, with 65.3% of participants reaching a BMI below 30; also reported reductions in knee osteoarthritis pain and obstructive sleep apnoea severity
- Phase 3 TRANSCEND-T2D-1 (published in The Lancet, 2026): A1C reductions of up to 2.0% and up to 16.8% weight loss at 40 weeks in type 2 diabetes
- Phase 3 TRIUMPH-2 and TRIUMPH-3 (company-reported topline, 23 July 2026): up to 20.8% mean weight loss at 80 weeks in adults with obesity and type 2 diabetes, and up to 22.6% in adults with severe obesity and established cardiovascular disease
- Eli Lilly states it plans to submit a Biologics License Application to the FDA in the first quarter of 2027; it is not an approved medicine anywhere
Strength of the evidence: A randomised, double-blind, placebo-controlled Phase 2 trial in the New England Journal of Medicine, a Lancet-published Phase 3 diabetes trial, and further Phase 3 obesity results released as company topline statements awaiting peer review. TRIUMPH-3, run in people with established cardiovascular disease, did not demonstrate a reduction in cardiovascular events. Long-term safety data are still being collected.
Safety and known cautions
Not approved for any use. Nausea, vomiting and diarrhoea are common in trials, especially during dose increases. Muscle loss accompanies rapid weight loss without adequate protein and resistance training. Topline company figures are not the same as peer-reviewed results. Compounded or research-market 'retatrutide' products are unverified and may be unsafe. Any use belongs under a prescribing clinician.
Evidence at a glance
No single score, on purpose. The line beside each bar shows how much reported outcomes vary between studies.
Development stage
- Discovery
- Preclinical
- Phase 1
- Phase 2
- Phase 3Current
- Regulatory review
- Approved