Retatrutide and tirzepatide compared
The two names tend to appear together. They share a developer and a drug family. What separates them is the number of receptors each engages and how far each has progressed. This page sets out both differences without spin.
On this page
Side-by-side summary
| Tirzepatide | Retatrutide | |
|---|---|---|
| Receptor targets | GLP-1 + GIP | GLP-1 + GIP + glucagon |
| Class | Dual agonist | Triple agonist |
| Frequency | Weekly | Weekly, as tested in trials |
| Developer | Eli Lilly | Eli Lilly |
| Regulatory status | Approved as Mounjaro and Zepbound | Phase 3, investigational |
Two targets versus three
Tirzepatide activates two receptors, GLP-1 and GIP. In combination they reduce appetite, delay gastric emptying and improve glucose control. Retatrutide covers the same ground. It then adds a third signal at the glucagon receptor. That signal increases energy expenditure and supports the breakdown of fat stores. The glucagon component is the entire rationale for retatrutide as a distinct molecule. Our mechanism explainer covers it in depth.
Trial evidence for each
Tirzepatide rests on a large, completed programme of trials. In its obesity studies, mean weight reduction came to roughly 20 percent. Retatrutide's best-known data is a Phase 2 trial in the New England Journal of Medicine, 2023. At the top dose, mean weight fell by about 24 percent over 48 weeks. Its Phase 3 TRIUMPH studies, reporting in 2025 and 2026, gave numbers in a comparable or higher band.
These are figures from different trials with different designs. A Phase 3 head-to-head study, TRIUMPH-5, is comparing the two directly, but Lilly reports that no such trial has been completed yet.
Educational summary of published clinical research. Numbers taken from separate trials do not form a direct comparison and say nothing about any individual.
Is one more potent?
Judged by trial averages, retatrutide has produced the larger weight reduction. That is consistent with its added glucagon target. Still, “stronger” is a blunt word here. The studies were designed differently. Tirzepatide has years of real-world use; retatrutide has none. And individual responses vary. A balanced reading is this: early data favours retatrutide on size of effect, while tirzepatide is the established, approved compound today.
Where each stands with regulators
Tirzepatide holds approval as a medicine. Retatrutide does not. In August 2026 it remained in Phase 3, and Eli Lilly has said it plans to file with the FDA in the first quarter of 2027. The full picture is in our article on retatrutide's FDA status.
References
- Jastreboff AM, Kaplan LM, Frias JP, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. PMID 37366315.
- ClinicalTrials.gov. Retatrutide (LY3437943): Phase 3 TRIUMPH studies. Trial records.
- Jastreboff AM, Kaplan LM, Hartman ML. Triple-Hormone-Receptor Agonist Retatrutide for Obesity. Reply. N Engl J Med. 2023;389(17):1629-1630. PMID 37888927.
- Lilly Medical. How does retatrutide compare with other incretin-based therapies? (TRIUMPH-5, NCT06662383). medical.lilly.com.
- Eli Lilly and Company. Retatrutide successful in two additional Phase 3 obesity trials (TRIUMPH-2, TRIUMPH-3). Press release, 23 July 2026. investor.lilly.com.
Frequently asked questions
Does retatrutide outperform tirzepatide?
Early trial data showed a larger average weight reduction with retatrutide, matching its additional glucagon target. No head-to-head trial has reported yet, and tirzepatide remains the approved, established compound.
How do retatrutide and tirzepatide differ?
The receptor count and the approval status. Tirzepatide engages GLP-1 and GIP and already has approval. Retatrutide engages those two plus glucagon, and it remains investigational.
Does one company make both?
Yes. Eli Lilly develops both compounds.
Does retatrutide have approval, as tirzepatide does?
No. Tirzepatide is approved. In August 2026 retatrutide was still in Phase 3 and had no approval.