Retatrutide: Triple Agonist Phase 3 Results and Current Status

Retatrutide has produced the largest weight-loss results ever published for a drug: 28.3% mean loss at 80 weeks on 12 mg in TRIUMPH-1, and 30.3% at 104 weeks in a higher-BMI extension. It also has no FDA-approved application as of 23 August 2026, which means there is no US prescription route to it outside a clinical trial. Everything sold online under the name retatrutide comes from unregulated synthesis and is not the drug those trials tested. Both of those facts are true at once, and the forums that push the first one tend to skip the second.

What retatrutide is

Retatrutide is a once-weekly injectable peptide that activates three receptors: GIP, GLP-1 and glucagon. Semaglutide hits one of those. Tirzepatide hits two. The glucagon receptor is the addition that makes retatrutide structurally different from everything already approved, and it is the reason the efficacy numbers stepped up rather than crept up.

Glucagon receptor agonism is associated with increased energy expenditure, which is a different lever from the appetite and gastric-emptying effects that drive GLP-1 weight loss. Whether that mechanism explains the trial results is a question the full publications should answer, not something the topline numbers establish on their own.

Retatrutide is also sold and discussed as reta, reta peptide, triple-G, GGG and "GLP-3". The last of those is not a real receptor or drug and is explained on our GLP-3 page. Its Eli Lilly development code is LY3437943, which is the term to use when searching for primary sources.

TRIUMPH-1: the headline result

TRIUMPH-1 randomised 2,339 adults with obesity, or overweight plus at least one weight-related comorbidity, without diabetes. It ran 80 weeks, placebo-controlled.

At 12 mg, mean weight loss was 28.3%, reported as 70.3 lb. 45.3% of participants in that arm lost 30% or more of their body weight. Placebo lost 3.9% on the estimand where the dose-response was reported.

• 4 mg: 17.6% mean loss
• 9 mg: 23.7% mean loss
• 12 mg: 25.0% on that estimand, 28.3% on the estimand carrying the 70.3 lb figure
• Placebo: 3.9%

The 104-week extension

Participants with a baseline BMI of 35 or above who continued into a study extension reached up to 30.3% mean weight loss at 104 weeks, reported as 85.0 lb. That is the largest figure attached to retatrutide anywhere and it is the one most often quoted without its conditions, which are a specific subgroup, a longer duration and continued treatment.

The rest of the TRIUMPH programme

TRIUMPH-2 and TRIUMPH-3 reported up to 22.6% weight reduction in their own populations. The headline number for retatrutide therefore varies by roughly six percentage points depending on which trial you cite, which is not inconsistency but a reminder that populations and endpoints differ across a programme.

Lilly's phase 3 reporting also described substantial relief from osteoarthritis pain alongside weight loss. That finding is early and comes from company reporting rather than an independent publication, so treat it as emerging rather than settled.

Regulatory status: not approved anywhere

Retatrutide is in phase 3. It has no FDA-approved application as of 23 August 2026. There is no compounding route, no off-label prescription route and no early-access route that a member of the public can use. The only legitimate way to receive retatrutide is enrolment in a trial that is recruiting.

Long-term safety has not been established outside the trial programme. Class-typical gastrointestinal effects are expected, and the glucagon component raises questions about heart rate and hepatic parameters that the full publications need to answer.

Why research-use-only retatrutide is not the trial drug

Retatrutide is one of the most heavily sold compounds in the grey market, precisely because the trial data are extraordinary and the drug is unobtainable. Products sold under that name are synthesised outside the regulated supply chain and shipped with a research-use-only label.

That label is a legal position taken by the seller. It is not a quality assurance. There is no independent verification of identity, no assay confirming concentration, no sterility testing and no stability data for the vial in front of you. The peptide impurity and immunogenicity concerns FDA has cited for unregulated peptide supply apply directly here.

The practical consequence is that a dose number from TRIUMPH-1 cannot be carried over to a grey-market vial, because the amount of drug actually present is unknown. The trial results describe a specific molecule at a specific purity delivered under supervision. None of those conditions hold outside the trial.

The evidence, one row per claim

Questions people ask

Sources

1. AJMC
2. The Pharmaceutical Journal
3. Eli Lilly press release
4. The Cardiology Advisor
5. Barchart / Lilly release
6. openFDA Drugs@FDA query returning no approved US application for retatrutide — the query deliberately returns no results, and that absence is the evidence (returns no results — that is the evidence)

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