Retatrutide is tirzepatide's successor in Lilly's pipeline: the same idea of one peptide activating several receptors, extended from two to three. The third receptor is glucagon's. Glucagon raises blood glucose, which is why a diabetes drug that activates it sounds wrong, but it also raises energy expenditure and hepatic fat oxidation, and in combination with GLP-1 and GIP activity the glucose effect is offset. The phase 2 result was the largest mean weight reduction reported for any incretin drug at the time.
Mechanism and receptor profile
A single peptide with agonist activity at the GIP, GLP-1 and glucagon receptors, given once weekly by subcutaneous injection. The trial abstracts describe it as a triple-hormone-receptor agonist. There is no label, so there is no FDA-reviewed mechanism statement; the physiology is set out on the how the class works guide.
Regulatory status
No application in Drugs@FDA as of 4 September 2026. The TRIUMPH phase 3 program in obesity, obstructive sleep apnea and knee osteoarthritis is described in a 2026 design paper (PubMed 41090431); the first phase 3 publication, in type 2 diabetes, appeared in the Lancet in June 2026. This page will carry approval dates and label dosing when there is a label to cite.
Trials and their numbers
| Trial | Population and duration | Result | PubMed |
|---|---|---|---|
| Phase 2, obesity | 338 adults with obesity or overweight, no diabetes; 48 weeks | Weight -8.7% (1 mg), -17.1% (4 mg), -22.8% (8 mg), -24.2% (12 mg) vs -2.1% placebo; at 12 mg, 100% lost 5% or more, 93% lost 10% or more, 83% lost 15% or more vs 27%, 9% and 2% on placebo | 37366315 |
| Phase 3, type 2 diabetes | 537 adults with type 2 diabetes inadequately controlled on diet and exercise, mean HbA1c 7.9% | HbA1c -1.69, -1.86, -1.94 points (4, 9, 12 mg) vs -0.81 placebo; weight -11.5%, -13.9%, -15.3% vs -2.6%; discontinuation for adverse events 2% to 5% vs 0%; no severe hypoglycemia | 42250575 |
At 24 weeks in phase 2 the 8 mg and 12 mg arms were already at minus 17.3% and minus 17.5%, and the curves had not flattened at 48 weeks, which is the observation that made the drug famous. The abstract reports that adverse events were mostly gastrointestinal, dose-related, mild to moderate, and partly mitigated by a lower starting dose.
Adverse events
No label table exists. From the abstracts: gastrointestinal events were the most common in both trials; in the phase 3 diabetes trial two deaths occurred during the study, reported in the abstract without attribution in the portion available. Full safety tables are in the papers, not on this page.
Boxed warning
None yet; there is no label. As a peptide agonist at the GLP-1 receptor, it would be expected to carry the class thyroid C-cell warning if approved, but that is inference, not record.
Manufacturer
Eli Lilly, which funded both trials.
Where next
Survodutide takes the GLP-1 plus glucagon route without GIP; CagriSema pairs GLP-1 with amylin instead. The comparison table preset "Multi-receptor agents" lines them up next to tirzepatide.
Questions people ask
Is retatrutide available?
Not as an approved medicine. Drugs@FDA has no application for it. Anything sold as retatrutide outside a clinical trial is an unapproved, untested product with no label; this site does not describe dosing for it.
How much more weight loss than tirzepatide?
Nobody has measured that head to head. Phase 2 retatrutide reported minus 24.2% at 48 weeks at 12 mg; SURMOUNT-1 tirzepatide reported minus 20.9% at 72 weeks at 15 mg. Different trials, different durations, different populations. Phase 3 retatrutide results in obesity are what will allow a fair statement.
Sources
- Jastreboff AM et al. Triple-hormone-receptor agonist retatrutide for obesity, a phase 2 trial. N Engl J Med 2023. PubMed 37366315 Accessed September 4, 2026.
- Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control (phase 3). Lancet 2026. PubMed 42250575 Accessed September 4, 2026.
- Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: rationale and design of the TRIUMPH program. Diabetes Obes Metab 2026. PubMed 41090431 Accessed September 4, 2026.
- Drugs@FDA search (no application for retatrutide on 4 September 2026) Accessed September 4, 2026.
Canonical URL: https://formblendsglp1s.com/agents/retatrutide. Written by the FormBlends editorial team. This page is educational and is not medical advice; see the medical disclaimer.