Research notes
Retatrutide vs Semaglutide: Triple Agonist Against the Benchmark
Retatrutide vs semaglutide is a comparison between the compound that started the GLP-1 era and the one that may end it. Semaglutide, sold as Ozempic and Wegovy, is the most prescribed weight management medicine in the world and the benchmark every newer peptide is measured against. Retatrutide is Eli Lilly’s triple agonist, still in Phase 3, with Phase 2 results that beat semaglutide’s Phase 3 numbers in two thirds of the time. This article sets the two side by side: receptor profile, trial results, side effects, availability in Thailand, and what the difference means for research.
Reta Bangkok supplies retatrutide strictly for laboratory research. The clinical figures below come from published trials and appear here for reference only. Nothing on this page is medical advice.
The short version
- Semaglutide activates one receptor, GLP-1. Retatrutide activates three: GLP-1, GIP and glucagon.
- Semaglutide’s STEP 1 trial: 14.9 percent mean weight reduction at 68 weeks. Retatrutide’s Phase 2 trial: 24.2 percent at 48 weeks.
- Semaglutide is approved and available in Thailand through hospitals. Retatrutide is not approved anywhere and exists only as a research compound.
- Both are weekly peptides with similar handling. Retatrutide’s half life is about six days, semaglutide’s about seven.
- Semaglutide has years of safety data in millions of people. Retatrutide has a few hundred trial participants so far.
What each compound is
Semaglutide
Semaglutide is a Novo Nordisk analogue of human GLP-1, modified with a fatty diacid chain and two amino acid substitutions so it resists breakdown and lasts about a week. It was approved for type 2 diabetes in 2017 as Ozempic and for chronic weight management in 2021 as Wegovy. Its STEP and SUSTAIN trial programmes enrolled tens of thousands of participants, and it has since been used by millions of people worldwide, which makes its safety profile the best characterised in the class by a wide margin.
Retatrutide
Retatrutide (LY3437943) is an Eli Lilly peptide built on the GIP backbone and engineered to activate GLP-1, GIP and glucagon receptors together. The glucagon component is what no other compound in the class has: glucagon receptor activity raises energy expenditure and acts on the liver directly. It is weekly, with a half life of about six days, and is currently in the TRIUMPH Phase 3 programme. No regulator has approved it. For the full trial detail, see our summary of the retatrutide results.
Receptor profile: one target against three
| Semaglutide | Retatrutide | |
|---|---|---|
| GLP-1 receptor | Yes | Yes |
| GIP receptor | No | Yes |
| Glucagon receptor | No | Yes |
| Class | Single agonist | Triple agonist |
| Approximate half life | 7 days | 6 days |
| Developer | Novo Nordisk | Eli Lilly |
| Status | Approved (2017, 2021) | Phase 3, not approved |
GLP-1 agonism alone reduces appetite and slows gastric emptying, which is where semaglutide’s effect comes from. Adding GIP, as tirzepatide does, appears to improve tolerability and add further weight effect. Adding glucagon on top, as retatrutide does, brings a mechanism the other two lack: higher energy expenditure, so the compound works on both sides of the energy balance rather than only on intake. That is the mechanistic reason retatrutide’s trial numbers are larger, and it is why researchers are interested in it specifically rather than as another GLP-1 variant.
What the trials show
| Semaglutide 2.4 mg (STEP 1) | Retatrutide 12 mg (Phase 2) | |
|---|---|---|
| Participants | 1,961 | 338 |
| Duration | 68 weeks | 48 weeks |
| Mean weight reduction | 14.9% | 24.2% |
| Placebo | 2.4% | 2.1% |
| Lost at least 15% | 50.5% | About 83% |
| Curve at trial end | Plateaued | Still falling |
The headline gap is large: 24.2 percent against 14.9 percent, in 20 fewer weeks. The retatrutide 4 mg group alone, a third of the top amount, lost 17.1 percent, which exceeds semaglutide’s result at its full amount. Two caveats apply, and both matter. The semaglutide figure comes from a Phase 3 trial with nearly two thousand participants, and the retatrutide figure from a Phase 2 trial with a few hundred; smaller trials tend to show larger effects. And the two trials used different populations and durations, so the comparison is indicative rather than head to head. A direct comparison will exist only when Phase 3 reads out.
Side effects in the literature
Both compounds share the gastrointestinal profile of the class: nausea, diarrhoea, constipation and vomiting, concentrated in the early weeks and during escalation, mostly mild to moderate. Semaglutide’s profile is thoroughly mapped after years of use, including the rarer events that only appear at scale. Retatrutide’s Phase 2 data added two signals not typical of semaglutide: a transient increase in heart rate peaking around week 24, and skin sensitivity (dysesthesia) at higher amounts. Whether those hold up in thousands of participants is one of the questions Phase 3 exists to answer.
Availability in Thailand
This is where the two diverge completely. Semaglutide is a registered medicine in Thailand. Ozempic and Wegovy are available through private hospitals in Bangkok, Chiang Mai, Phuket and Pattaya with a consultation and prescription, at hospital pricing. Retatrutide has no approval anywhere, so there is no pharmacy or hospital route for it in Thailand or any other country. It is available only as a research compound, from suppliers that hold tested stock locally. Our retatrutide in Thailand page covers the regulatory position and the supply channels in detail.
What the difference means for research
Semaglutide is the reference compound for GLP-1 agonism: the mechanism is fully characterised, the data set is enormous and results reproduce. If a research question needs a known single agonist to compare against, semaglutide is the obvious control. Retatrutide is the compound of interest when the question involves the glucagon receptor, energy expenditure, hepatic fat, or the newest generation of multi receptor agonists before Phase 3 data arrives. Much of the current research interest sits in comparing them directly, which is the comparison the published literature does not yet contain.
Retatrutide at Reta Bangkok
We stock retatrutide in 10 mg, 20 mg, 30 mg, 40 mg and 60 mg vials, along with tirzepatide and a retatrutide and cagrilintide blend. An independent lab tests every batch and the certificate sits on each product page. Same day delivery in Bangkok before 3 pm, one to three days across Thailand. For the dual agonist comparison, see retatrutide vs tirzepatide.
References
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384:989-1002.
- Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity, a Phase 2 Trial. N Engl J Med. 2023;389:514-526.
- 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.