Research notes
Retatrutide vs Tirzepatide: What Is the Difference?
Retatrutide vs tirzepatide is the comparison researchers in Bangkok ask us about most, and the two peptides look almost identical on paper. Both come from the same developer, both arrive as lyophilised powder, and both need the same reconstitution and storage routine. However, they differ in three ways that matter: how many receptors each one targets, how far along the clinical research is, and what the published data shows. This article lays those differences out side by side.
Reta Bangkok supplies every product strictly for laboratory research. Nothing on this page is medical advice. The clinical figures below come from published trials and appear here for reference only.
The short version
- Tirzepatide is a dual agonist. It activates the GLP-1 and GIP receptors.
- Retatrutide is a triple agonist. In addition to GLP-1 and GIP, it also activates the glucagon receptor.
- Tirzepatide has completed Phase 3 and holds approval in many countries. Retatrutide, by contrast, remains in Phase 3 trials with no approval anywhere.
- In published trials, retatrutide produced larger reductions in body weight over a shorter period.
- Both peptides need the same lab handling: reconstitute with bacteriostatic water, refrigerate, and use within the usual window.
What each peptide is
Tirzepatide
Tirzepatide is a 39 amino acid synthetic peptide from Eli Lilly. Its designers started with the GIP sequence and then modified it so it also binds the GLP-1 receptor. A C20 fatty diacid chain extends its half life to around five days. The United States approved it in 2022 for type 2 diabetes and later for chronic weight management, under the names Mounjaro and Zepbound. As a result, tirzepatide is one of the most studied peptides of the last decade, with a large body of Phase 3 data from the SURPASS and SURMOUNT programmes.
Retatrutide
Retatrutide, also known by its development code LY3437943, is a newer Eli Lilly peptide that adds a third target. On top of GLP-1 and GIP, it also activates the glucagon receptor. That glucagon component is the interesting part for researchers, because glucagon receptor activity links to higher energy expenditure and to effects on liver fat, which GLP-1 and GIP agonism alone do not provide. Like tirzepatide, retatrutide carries a fatty diacid chain, and its half life is roughly six days. It is currently in the TRIUMPH Phase 3 programme, so no regulator has approved it yet.
Receptor profile: the real difference
| Tirzepatide | Retatrutide | |
|---|---|---|
| GLP-1 receptor | Yes | Yes |
| GIP receptor | Yes | Yes |
| Glucagon receptor | No | Yes |
| Class | Dual agonist | Triple agonist |
| Approximate half life | 5 days | 6 days |
| Development stage | Approved (2022) | Phase 3, not approved |
| Developer | Eli Lilly | Eli Lilly |
Tirzepatide leans towards GIP. It binds the GIP receptor about as strongly as native GIP does, while it binds the GLP-1 receptor several times more weakly than native GLP-1. Retatrutide uses a different balance: strongest at GIP, weaker at GLP-1, and weakest at glucagon. That order is deliberate. Too much glucagon activity raises blood glucose, so the designers kept the glucagon component low enough for the GLP-1 and GIP activity to more than offset it.
What the published trials show
The figures below come from peer reviewed trials. We include them so researchers can see how the two compounds have performed in the literature, not as a recommendation of any kind.
Tirzepatide: SURMOUNT-1
SURMOUNT-1 (New England Journal of Medicine, 2022) followed 2,539 adults with obesity for 72 weeks. At the highest weekly amount studied, participants lost a mean of 20.9 percent of their body weight, compared with 3.1 percent on placebo. Moreover, over half of that group lost at least 20 percent of their starting weight.
Retatrutide: Phase 2
The retatrutide Phase 2 obesity trial (New England Journal of Medicine, 2023) followed 338 adults for 48 weeks. At the highest weekly amount studied, participants lost a mean of 24.2 percent of their body weight, compared with 2.1 percent on placebo. In other words, retatrutide beat tirzepatide’s headline figure and did so in 24 fewer weeks. A separate Phase 2 study in participants with fatty liver disease also reported liver fat reductions of over 80 percent at the higher amounts, which researchers attribute to the glucagon receptor component.
The caveat is sample size. SURMOUNT-1 enrolled over seven times as many participants as the retatrutide Phase 2 trial, and tirzepatide now has years of post approval safety data behind it. Retatrutide’s Phase 3 results should arrive through 2026 and 2027. Until then, its profile looks promising but not yet established.
Side effect profile in the literature
Both peptides share the gastrointestinal effects common to the whole incretin class: nausea, reduced appetite, constipation and diarrhoea. These mostly appeared during the early weeks of each trial, and most cases were mild to moderate. Retatrutide’s Phase 2 data also recorded a small rise in heart rate that peaked around week 24 and then trended back down, as well as skin sensitivity (dysesthesia) at the higher amounts. Neither effect appeared at the same rate in the tirzepatide trials. Whether that reflects a real difference or simply the smaller sample will become clearer once the Phase 3 data lands.
Handling in the lab: no practical difference
For anyone working with these compounds, the handling is identical. Both arrive as a lyophilised white powder in a sealed vial. To reconstitute either one, add bacteriostatic water, swirl rather than shake, and then store the solution in the refrigerator at 2 to 8 °C. Unopened lyophilised vials stay stable for far longer, provided you keep them cold and out of light. Both peptides also have similar molecular weights (just under 5 kDa), similar solubility and similar sensitivity to heat and agitation. Our reconstitution guide covers the exact steps.
Which one is right for your research?
It depends on the question you are asking. Tirzepatide makes the better reference compound, because its mechanism is thoroughly characterised, its data set is enormous and its results reproduce well. So if you need a well understood dual agonist to compare something against, tirzepatide is the obvious choice. Retatrutide, on the other hand, is the compound of interest when your question involves the glucagon receptor, energy expenditure or hepatic fat, or when you want to study the newest generation of multi receptor agonists before the Phase 3 data arrives. For that reason, many researchers run both side by side.
Retatrutide and tirzepatide at Reta Bangkok
We stock Retatrutide in 10 mg, 20 mg, 30 mg, 40 mg and 60 mg vials, and Tirzepatide in 10 mg and 30 mg vials, with bacteriostatic water available as an add on. An independent lab tests every batch, and we publish the certificate of analysis on each product page. Finally, orders placed before 3 pm go out the same day in Bangkok, and we ship nationwide across Thailand.
References
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387:205-216. (SURMOUNT-1)
- Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity, a Phase 2 Trial. N Engl J Med. 2023;389:514-526.
- Sanyal AJ et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nat Med. 2024;30:2037-2048.
- Coskun T et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept. Cell Metab. 2022;34:1234-1247.
All products on Reta Bangkok are for laboratory research use only, not for human or veterinary use.