Also known as LY3437943 · Triple G · GGG agonist · GIP/GLP-1/glucagon triple agonist
Investigational once-weekly triple agonist (GIP / GLP-1 / glucagon) — the molecule some in the research community nickname "GLP-3" — with the largest weight reductions reported for any incretin-class agent.
Research refreshed
Retatrutide is an Eli Lilly–developed triple agonist targeting GIP, GLP-1, and glucagon receptors. Phase 2 trials reported ~24% mean weight reduction at 48 weeks at the highest dose (NEJM 2023), and the first Phase 3 readout (TRIUMPH-4, December 2025) reported 28.7% mean weight loss at 68 weeks — approaching the range long associated with bariatric surgery. It remains investigational and is not FDA-approved.
Retatrutide (development code LY3437943) is an investigational single peptide that activates three receptors — GIP, GLP-1, and glucagon. It is sometimes informally called "GLP-3" or a "Triple G" agonist in research and community discussions, though it has no such official designation; the nickname simply reflects the three incretin/glucagon-family receptors one molecule engages. Adding glucagon-receptor agonism to the incretin pair is studied as a way to increase energy expenditure and lipolysis on top of the insulinotropic and satiety effects of GIP and GLP-1 — the receptor logic that separates it from single agonists (semaglutide) and dual agonists (tirzepatide, survodutide, mazdutide).
Developed by Eli Lilly, retatrutide has produced the largest weight reductions reported for any incretin-class agent. The Phase 2 obesity trial (Jastreboff et al., NEJM 2023, PMID 37366315) reported dose-dependent mean reductions up to −24.2% at 48 weeks at the 12 mg dose, versus −2.1% on placebo — with weight curves that had not plateaued at study end. The Phase 2 type-2-diabetes trial (Rosenstock et al., Lancet 2023, PMID 37385280) reported deep HbA1c reductions alongside up to ~17% weight loss at 36 weeks. A liver-fat sub-study in participants with MASLD (PMID 38858523) reported relative liver-fat reductions exceeding 80% at the two highest doses — the largest such reduction reported for any drug class candidate at the time.
The Phase 3 TRIUMPH program began reporting in December 2025: TRIUMPH-4 (obesity with knee osteoarthritis, NCT05931367) reported mean weight loss of 28.7% (about 71 lbs) at 68 weeks at the 12 mg dose, with substantial improvement in osteoarthritis pain scores. Lilly has stated that results across the broader TRIUMPH program — including obesity without osteoarthritis and obstructive sleep apnea — are expected through 2026. Retatrutide remains investigational everywhere: no regulator has approved it, and all data comes from clinical research.
Triple receptor agonism — GIP + GLP-1 (insulinotropic, satiety, slowed gastric emptying) plus glucagon (energy expenditure, lipolysis, hepatic-fat mobilization) — from a single acylated ~39-residue peptide dosed once weekly.
Behind every vial of Retatrutide is the same exacting pipeline every research peptide runs — but the chemistry plays out differently for this molecule. Here is how Retatrutide, specifically, is brought into being.
On paper, Retatrutide is C221H342N46O68 — about 4,731.5 daltons of precisely arranged atoms. Before a single bond is made, the target sequence, salt form, and purity threshold are written down as the contract the finished material must meet.
Retatrutide is assembled by solid-phase peptide synthesis — the chain grows one protected residue at a time on resin, and what you fail to build cleanly here you pay to remove later. It also carries fatty-acid acylation, an extra step beyond a plain chain that adds both capability and cost.
The crude mixture — Retatrutide plus its deletions and side products — is then separated on preparative HPLC, and where the cut is taken decides the difference between a genuinely pure peptide and a barely-passable one.
A real batch of Retatrutide proves itself: identity confirmed by mass spectrometry against its ~4,731.5 Da, purity read directly off an analytical HPLC trace, water and counterion content measured. That batch-specific certificate of analysis is the only honest way to know what is actually in a vial of Retatrutide — and a short, cold, accountable chain of custody is how that purity survives the trip to your bench.
A ~39-residue triple (GIP/GLP-1/glucagon) agonist built by solid-phase synthesis with Aib substitutions and a fatty-diacid chain on a side-chain lysine that binds albumin for once-weekly dosing. The acylation step and the sterically hindered Aib couplings are the hard parts, and the long sequence makes deletion-sequence control the dominant purity problem.
Don't judge a vial by its cake. A fluffy, good-looking lyophilized powder reflects bulking agents and freeze-drying parameters — not purity. Insist on a batch-specific certificate of analysis.
Recent clinical trials and publications mentioning Retatrutide, pulled automatically from ClinicalTrials.gov and PubMed and refreshed daily. Listings are unfiltered search results, not curated endorsements.
Retatrutide (LY3437943) is an investigational Eli Lilly triple agonist of the GIP, GLP-1, and glucagon receptors, in late-stage trials for obesity, type 2 diabetes, and MASH. Phase 2 reported ~24% mean weight reduction at 48 weeks; the first Phase 3 readout reported 28.7% at 68 weeks.
"GLP-3" is an informal nickname, not an official name — there is no receptor called GLP-3. The community coined it for triple agonists that engage three targets: GIP, GLP-1, and glucagon receptors. Retatrutide (LY3437943) is the most advanced molecule in this class, which is why "GLP-3" in search results and forums almost always refers to retatrutide.
Phase 2 (NEJM 2023): a dose-dependent mean of −8.7% (1 mg) to −24.2% (12 mg) at 48 weeks, versus −2.1% placebo. Phase 3 TRIUMPH-4 (December 2025 topline): −26.4% (9 mg) to −28.7% (12 mg) at 68 weeks. These are population means from trials, not predictions for any individual.
Semaglutide activates GLP-1 alone; tirzepatide activates GIP + GLP-1. Retatrutide adds a third target — the glucagon receptor — studied for increased energy expenditure and fat mobilization, including from the liver. That added arm is the proposed basis for its larger reported weight reductions.
In published trials the most common adverse events were gastrointestinal — nausea, vomiting, diarrhea, and constipation — mostly during dose escalation and mostly mild to moderate, similar in character to the broader incretin class. Glucagon-receptor agonism is also studied for its effects on heart rate. Full Phase 3 safety data is still being characterized; this page is a research reference, not medical advice.
It is not approved anywhere, and no approval date has been announced. The TRIUMPH Phase 3 program began reporting results in December 2025, with further readouts expected through 2026; any regulatory submission would follow completed Phase 3 data. Any retatrutide sold today is outside any approved or regulated channel.
Yes — a single ~39-residue synthetic peptide (~4,731.5 Da, C221H342N46O68) built by solid-phase synthesis, with Aib substitutions and a fatty-diacid side chain on a lysine that binds albumin to give a once-weekly half-life.
Eli Lilly, which created it as LY3437943. This page is a research and educational reference, not medical advice or an offer for sale.
The once-weekly GLP-1 receptor agonist behind Ozempic, Wegovy, and Rybelsus — FDA-approved for type 2 diabetes, chronic weight management, cardiovascular risk reduction, and MASH.
ViewThe once-daily GLP-1 agonist that preceded semaglutide — FDA-approved for diabetes (Victoza) and obesity (Saxenda).
ViewDual GIP / GLP-1 receptor agonist with industry-leading weight-loss endpoints.
ViewDosing protocols, mechanism, comparisons, and the latest trials — citation-backed answers grounded in PubMed, PubChem, and ClinicalTrials.gov.