A phase 3 trial published in The Lancet on 29 September 2026 reports how retatrutide performed in adults with obesity and type 2 diabetes. In 1,152 randomised participants, average bodyweight change at week 80 ranged from -11.9% to -18.8% across the 4 mg, 9 mg and 12 mg study groups, compared with -5.1% for placebo. The paper also reports gastrointestinal adverse events and treatment discontinuations, so the headline result needs to be read with the full trial design and its limits.
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What did the TRIUMPH-2 trial study?
TRIUMPH-2 was a double-blind, parallel-group, randomised, placebo-controlled phase 3 trial. It ran at 92 medical and research centres and hospitals in eight countries. The participants were adults with a body-mass index of at least 27 kg/m2, type 2 diabetes and glycated haemoglobin between 6.5% and 10.5%. They were already using stable diabetes treatment, ranging from diet and exercise alone to up to three oral glucose-lowering medicines.
The trial is registered as NCT05929079. Between 11 July 2023 and 1 November 2024, 2,047 people were screened and 1,152 were randomised. The four groups received placebo or once-weekly retatrutide at 4 mg, 9 mg or 12 mg. The primary comparison was the percentage change in bodyweight at week 80 for the 9 mg and 12 mg groups against placebo. The 4 mg comparison was a key secondary endpoint.
What changed at week 80?
Using the treatment-regimen estimand, the mean percentage change from baseline in bodyweight at week 80 was -11.9% with 4 mg retatrutide, -16.8% with 9 mg, and -18.8% with 12 mg. The placebo group changed by -5.1%. The estimated differences versus placebo were -6.9 percentage points, -11.8 percentage points and -13.8 percentage points, respectively. The paper reports p values below 0.0001 for all three comparisons.
These figures describe the average outcome in this trial population. They do not predict an outcome for an individual, and they do not turn a research compound into a product for human use. Retatrutide remains under investigation. The study was funded by Eli Lilly and Company, which is relevant context when reading the results and the paper’s disclosures.
What safety findings did the authors report?
Gastrointestinal events were the most frequently reported adverse events and were more common in the retatrutide groups than in the placebo group. Diarrhoea was reported in 27% of participants in the 4 mg group, 34% in the 9 mg group, 34% in the 12 mg group and 13% in the placebo group. Nausea occurred in 14%, 21%, 28% and 8%, respectively.
The paper also reports differences in hypotension and dysesthesia, a disturbance of sensation. Permanent treatment discontinuation because of adverse events or death occurred in 4% of the 4 mg group, 12% of the 9 mg group, 8% of the 12 mg group and 5% of the placebo group. Seven deaths occurred across the groups, and investigators judged all of them unrelated to the study intervention.
How should the results be interpreted?
The study provides phase 3 evidence in adults with obesity and type 2 diabetes, not a general answer for every population. Its participants had a specific entry profile, the intervention was delivered within a controlled trial, and the follow-up reported here ends at week 80. The results therefore belong to this protocol and its analysis population.
The authors conclude that retatrutide produced substantial improvements in bodyweight and was associated with improved glycaemic control. They also describe a safety profile generally consistent with other molecules with GLP-1 receptor agonism. That conclusion should be kept separate from questions about regulatory approval, the research-use-only status of laboratory materials, and any claim about a Peptra Labs product.
Related on Peptra Labs
For background, see the retatrutide research guide and the retatrutide product page. The research-use-only boundaries guide explains why published findings and laboratory research materials must not be treated as medical advice or as an approved treatment.
References
- Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. The Lancet. 2026. PubMed PMID 42810372. DOI: 10.1016/S0140-6736(26)01861-1.
- ClinicalTrials.gov. NCT05929079, TRIUMPH-2. Trial record.
The products referenced on this site are supplied for laboratory research use only. They are not medicines and are not intended for human or veterinary use. This article summarises published research for informational purposes and is not medical advice. Statements about third-party studies belong to their authors.
