Research notes
Retatrutide Results: What the Clinical Trials Show
Retatrutide results are the reason this peptide gets more attention than anything else in the incretin class. In its Phase 2 trial, participants on the highest amount lost an average of 24.2 percent of their body weight in 48 weeks, and the curve had not flattened when the trial ended. No other compound with published data has matched that in the same timeframe. This article goes through what the trials actually measured: weight, blood sugar, liver fat, side effects, and what is still unknown while Phase 3 runs.
Reta Bangkok supplies retatrutide strictly for laboratory research. The figures below come from peer reviewed trials and appear here for reference only. Nothing on this page is medical advice.
The short version
- Phase 2 obesity trial: 24.2 percent mean weight reduction at 48 weeks on the highest amount, against 2.1 percent on placebo.
- Weight loss had not plateaued at 48 weeks, which suggests the full effect is larger than the trial captured.
- Phase 2 type 2 diabetes trial: HbA1c fell by up to about 2 percentage points, with weight loss of up to 16.9 percent at 36 weeks.
- Liver fat trial: over 80 percent reduction in liver fat at the higher amounts, and most participants’ liver fat returned to the normal range.
- Side effects were mainly gastrointestinal and dose dependent, plus a transient rise in heart rate and some skin sensitivity.
- Phase 3 (the TRIUMPH programme) is running now. Nothing is approved yet.
What retatrutide is, in one paragraph
Retatrutide (LY3437943) is an Eli Lilly peptide that activates three receptors at once: GLP-1, GIP and glucagon. Semaglutide hits one of those, tirzepatide hits two. The glucagon component is what sets retatrutide apart, because glucagon receptor activity raises energy expenditure and acts directly on the liver, which the other two pathways do not. It is given once weekly and has a half life of about six days. For the receptor detail, see our retatrutide vs tirzepatide comparison.
Phase 2 obesity trial: the headline results
The trial most people mean when they talk about retatrutide results was published in the New England Journal of Medicine in 2023. It enrolled 338 adults with a BMI of 30 or above, or 27 with at least one weight related condition, and ran for 48 weeks. Participants received weekly retatrutide at 1 mg, 4 mg, 8 mg or 12 mg, or placebo.
| Weekly amount | Mean weight change at 24 weeks | Mean weight change at 48 weeks |
|---|---|---|
| Placebo | -1.6% | -2.1% |
| 1 mg | -7.2% | -8.7% |
| 4 mg | -12.9% | -17.1% |
| 8 mg | -17.3% | -22.8% |
| 12 mg | -17.5% | -24.2% |
Three details matter beyond the headline number. First, the response was broad: every participant in the 8 mg and 12 mg groups lost at least 5 percent of their body weight, and roughly 83 percent of the 12 mg group lost 15 percent or more. Second, the weight curves were still falling at week 48. The trial stopped, the effect had not. Third, the 4 mg group, a quarter of the top amount, still lost 17.1 percent, which is in the range tirzepatide reached at its highest amount over a longer trial.
Phase 2 type 2 diabetes trial
A separate Phase 2 trial, published in The Lancet in 2023, tested retatrutide in 281 adults with type 2 diabetes over 36 weeks, against both placebo and dulaglutide. HbA1c, the standard measure of blood sugar control, fell by up to about 2 percentage points at the higher amounts, compared with a fall of 1.4 points on dulaglutide. Weight fell by up to 16.9 percent in the same period. People with type 2 diabetes typically lose less weight on incretin drugs than people without it, so 16.9 percent in 36 weeks in that population was a notable figure.
Liver fat trial
A sub study published in Nature Medicine in 2024 looked at participants from the obesity trial who also had fatty liver disease (MASLD), using MRI to measure liver fat. At 48 weeks, liver fat fell by more than 80 percent in the 8 mg and 12 mg groups, and around 85 to 90 percent of participants in those groups reached a normal liver fat level. Researchers attribute much of this to the glucagon receptor component, because glucagon signalling acts on the liver directly. This is the result that distinguishes retatrutide from the GLP-1 and GIP compounds most clearly.
Side effects reported in the trials
The pattern matches the rest of the incretin class, with two additions. Gastrointestinal effects were the most common: nausea, diarrhoea, vomiting and constipation, mostly mild to moderate, mostly early, and more frequent at higher amounts and with faster escalation. Discontinuation because of side effects ranged from 6 to 16 percent across the retatrutide groups, with the faster escalation schedules at the top of that range.
The two additions: heart rate rose by a few beats per minute, peaked around week 24, and trended back towards baseline by week 48. Some participants also reported dysesthesia, a skin sensitivity or tingling, which was more common at the higher amounts and not typical of the GLP-1 drugs. Both are being watched closely in Phase 3.
How retatrutide compares
| Compound | Trial | Duration | Mean weight reduction |
|---|---|---|---|
| Retatrutide 12 mg | Phase 2 | 48 weeks | 24.2% |
| Tirzepatide 15 mg | SURMOUNT-1 | 72 weeks | 20.9% |
| Semaglutide 2.4 mg | STEP 1 | 68 weeks | 14.9% |
| Cagrilintide + semaglutide | REDEFINE 1 | 68 weeks | 22.7% |
The comparison is indicative, not head to head: different trials, different populations, different durations. The point is the direction. Retatrutide reached a larger reduction in a shorter time than anything else in the table, and it did so in a Phase 2 trial with a few hundred participants rather than a Phase 3 with thousands. That is both the promise and the caveat.
What is still unknown
Phase 2 answers “does it work and roughly how well”. Phase 3 answers “in whom, for how long, and at what cost”. The TRIUMPH programme is running several trials in parallel, in obesity with and without diabetes, with knee osteoarthritis, and with sleep apnoea, in thousands of participants over longer periods. The questions it will settle: whether the 48 week curve keeps falling and where it plateaus, whether the heart rate and dysesthesia signals matter at scale, how much weight is lean mass, and what happens on stopping. Until those read out, retatrutide is a compound with exceptional early data and an incomplete safety picture, which is exactly why it is a research compound and not a medicine.
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. Our retatrutide in Thailand page covers availability and pricing in more detail.
References
- Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity, a Phase 2 Trial. N Engl J Med. 2023;389:514-526.
- Rosenstock J et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial. Lancet. 2023;402:529-544.
- 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.
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387:205-216.
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384:989-1002.
- Garvey WT et al. Coadministered Cagrilintide and Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2025.
All products on Reta Bangkok are for laboratory research use only, not for human or veterinary use.