ES 
EN 
DE 
A research-focused comparison of Melanotan II and PT-141, covering melanocortin receptor selectivity, evidence, safety signals and regulatory status.
This text compares data from the clinical literature. It does not contain recommendations or medical advice.
The comparison of retatrutide vs tirzepatide is a comparison of two consecutive steps in the evolution of incretin pharmacology. After GLP-1 receptor monoagonists (semaglutide, liraglutide), Eli Lilly developed two peptides with a broader receptor profile — first a GLP-1 + GIP dual agonist (tirzepatide, LY3298176), then a GLP-1 + GIP + glucagon tri-agonist (retatrutide, LY3437943).
Lead definition
Retatrutide (a GLP-1 / GIP / glucagon triple agonist) and tirzepatide (a GLP-1 / GIP dual agonist) are two Eli Lilly peptides representing consecutive steps in the evolution of incretin pharmacology. Tirzepatide is a registered medicine (Mounjaro, Zepbound) with full phase III data. Retatrutide remains in phase III of the TRIUMPH clinical trials.
Comparability of data — a head-to-head RCT of retatrutide vs tirzepatide has not been published. Every numerical comparison in this article must be read as an indirect literature-based comparison.
The sequence is not coincidental. GLP-1 and GIP are physiological partners in the incretin effect — together they account for over 60% of the insulin response to a meal. Adding GIP to GLP-1 (tirzepatide) was a logical complement to physiology. Adding glucagon (retatrutide) went beyond the classic incretin axis — glucagon is not an incretin hormone but an energy-mobilising hormone. A full overview of the incretin axis is provided in the article on the incretins GLP-1, GIP and glucagon.
Tirzepatide activates two incretin receptors simultaneously and is the first clinically advanced GIP/GLP-1 dual agonist (Coskun et al. 2018). Activity at GLP-1R is responsible for glucose-dependent insulin secretion, suppression of glucagon secretion, delayed gastric emptying and appetite reduction. Activity at GIPR brings a synergistic increase in insulin secretion as well as modulation of adipose tissue metabolism.
In a head-to-head trial with the monoagonist semaglutide (SURPASS-2, Frias et al. 2021), tirzepatide produced a stronger reduction in HbA1c and a greater body weight reduction with a comparable adverse-event profile. Available in the catalogue as GLP-1+GIP 5mg PEN.
Retatrutide retains activity at GLP-1R and GIPR while adding partial activation of the glucagon receptor (GCGR). The potencies published by Coskun et al. (2022): ~94% of the potency of native GLP-1 at GLP-1R, ~135% of native GIP at GIPR (stronger than the native ligand), ~52% of native glucagon at GCGR (weaker). The chosen proportions mean that the hypoglycaemic pathway (GLP-1 + GIP) more than compensates for the hyperglycaemic pathway (glucagon).
The informal shorthand used for retatrutide in online searches is explained in a separate entry: “reta”: where the name comes from.
In pharmacology, a partial GCGR agonist brings three effects desirable in obesity therapy that neither mono- nor dual-agonists provide:
In the One Peptides catalogue, available as Triple G 20mg PEN or as a separate lyophilisate.
On the basis of these data, tirzepatide obtained registration as Mounjaro (T2D, FDA and EMA 2022) and Zepbound (obesity, FDA 2023, EMA 2024).
The full phase III TRIUMPH programme, started in 2022, comprises multiple trials. At the time of writing, there are no full, peer-reviewed publications of phase III results.
Interpretative note — the numerical figures come from different phases of clinical trials. Retatrutide is described by phase II, tirzepatide by phase III + registration. The comparison is indirect in nature.
| Characteristic | Retatrutide | Tirzepatide |
|---|---|---|
| Internal designation | LY3437943 | LY3298176 |
| Pharmacological class | Tri-agonist (GLP-1R + GIPR + GCGR) | Dual-agonist (GLP-1R + GIPR) |
| Architecture | 39 aa peptide, once/week, s.c. | 39 aa peptide, once/week, s.c. |
| Manufacturer | Eli Lilly | Eli Lilly |
| Half-life | ~6 days | ~5 days |
| Registration status | Phase III TRIUMPH (not registered) | Registered medicine — Mounjaro, Zepbound |
| Effect on the liver (MASLD) | Hepatic lipolysis via GCGR agonism | Modulation via GIP |
| Energy expenditure | Increase via GCGR thermogenesis | No direct thermogenesis |
| Heart rate | Greater increase (GCGR) | Slight increase |
| Gastrointestinal profile | Higher nausea at higher doses (25–60%) | Nausea 25–31% in phase III |
| Head-to-head profile | No head-to-head with tirzepatide | Head-to-head with semaglutide (SURPASS-2) |
Tirzepatide has a mature safety profile from phase III + registration. Gastrointestinal adverse events predominate (nausea, diarrhoea, vomiting). Rare signals: pancreatitis, gallbladder disease, contraindication in people with a personal or family history of medullary thyroid carcinoma.
Retatrutide has a profile described on the basis of phase II. The Jastreboff 2023 data indicate higher nausea at higher doses (25–60%), a greater increase in heart rate (mechanism: GCGR) and a signal of a slight increase in glycaemia in some subgroups.
What we do not know: there is no head-to-head RCT of retatrutide vs tirzepatide; the long-term cardiovascular profile of retatrutide requires multi-year observation; full phase III TRIUMPH data — publications expected from 2025.
An indirect comparison points to a slightly higher body weight reduction with retatrutide (~24.2% in phase II, 48 weeks) than with tirzepatide (~22.5% in phase III SURMOUNT-1, 72 weeks). The figures come from different phases of clinical trials. A head-to-head RCT has not been published to date.
Partial GCGR activation in retatrutide brings three effects: increased energy expenditure (thermogenesis), hepatic lipolysis (relevant in MASLD/MASH) and additional appetite modulation.
Tirzepatide — a full phase III programme (SURPASS, SURMOUNT), registration in two indications (Mounjaro 2022, Zepbound 2023). Retatrutide has a phase II from 2023 and the phase III TRIUMPH programme in progress.
After completion of the main phase III TRIUMPH trials, publication of the results, and submission of a registration application to the FDA and EMA — realistically in 2027–2028 (a pathway analogous to tirzepatide).
RUO note — Research Use Only
Both peptides in the One Peptides catalogue function as research reagents intended for laboratory research use only. They are not medicines, they are not dietary supplements and they are not intended for use in humans.
In the research-reagent catalogue, retatrutide is available as Triple G 20mg PEN or as a separate lyophilisate, and tirzepatide as GLP-1+GIP PEN. Catalogue standards: HPLC ≥ 98%, MS, COA for every batch, cold chain. A full description is given in quality testing and certificates.
A separate lyophilized product is Retatrutide (Triple G) 5 mg, offered exclusively as a Research Use Only reagent.
The comparison of retatrutide vs tirzepatide is a comparison of two consecutive steps in the evolution of incretin pharmacology — from dual agonism to tri-agonism. Adding GCGR activity in retatrutide brings increased energy expenditure, hepatic lipolysis and additional appetite modulation.
The most significant asymmetry in the comparison is the different stage of clinical development: tirzepatide has a full phase III + registration, while retatrutide has a phase II and the phase III TRIUMPH programme in progress. The indirect comparison of the figures (~24.2% vs ~22.5% weight reduction) is cautious and does not replace a head-to-head RCT.
Final disclaimer
One-Peptides products are reagents for laboratory research (Research Use Only). They are not medicines, dietary supplements or products for human consumption. Tirzepatide is a registered medicine (Mounjaro, Zepbound) — it requires a medical prescription. Retatrutide is in phase III TRIUMPH; at the time of writing it is not registered. This text is educational and review in nature.
A research-focused comparison of Melanotan II and PT-141, covering melanocortin receptor selectivity, evidence, safety signals and regulatory status.
A research comparison of MK-677 and ipamorelin, focusing on GHS-R1a signaling, selectivity, administration route, human evidence and WADA status.
We offer a wide selection of peptides tailored to a range of laboratory analytical needs.
Every batch is tested for identity and purity (HPLC, MS) and comes with a certificate of analysis.
We invest in analytical testing and full batch documentation for every product.
Nuestras numerosas reseñas positivas reflejan la satisfacción de nuestros clientes que siguen regresando por más.
¡Suscríbete al boletín!
Obtén un 10% de descuento en tu primera compra
One-Peptides.com
Información
© 2026 ONE-PEPTIDES.COM