What is retatrutide?
Retatrutide (development code LY3437943) is an investigational peptide substance in clinical development. It is not an approved medicine.
Biologically it is described as a triple agonist: it activates the GIP receptor, the glucagon receptor and a third gut hormone receptor. All three take part in regulating glucose and energy metabolism, which is why the substance is studied mainly on metabolic parameters.
What did the published studies show?
The published clinical development data (as of October 2026) include, among others, the following randomised, placebo-controlled trials:
- Phase 2 (Jastreboff et al., NEJM 2023, PMID 37366315): 338 adults with an elevated body mass index, 48 weeks. Primary end point: change in body weight at 24 weeks.
- TRIUMPH-1, phase 3 (Jastreboff et al., NEJM 2026, PMID 42814954): 2,339 adults with an elevated body mass index without diabetes, 80 weeks. Primary end points: change in body weight, plus knee pain in a subgroup with osteoarthritis and the apnoea-hypopnoea index in a subgroup with obstructive sleep apnoea.
- TRIUMPH-2, phase 3 (Bellido et al., Lancet 2026, PMID 42810372): 1,152 adults with an elevated body mass index and type 2 diabetes, 80 weeks. Primary end point: change in body weight at week 80.
According to the authors, in each of the three trials the primary end point of change in body weight differed significantly from placebo. The trials were funded by the sponsoring company. Detailed results for all end points are in the publications.
For a secondary analysis of cardiovascular markers, see the article on cardiovascular markers.
What side effects were reported in the clinical trials?
The adverse events recorded in the trials were mainly gastrointestinal.
In TRIUMPH-2 (PMID 42810372), in the retatrutide groups compared with placebo: • diarrhoea: 27–34% vs 13% • nausea: 14–28% vs 8% • hypotension: 1–6% vs less than 1% • dysaesthesia (altered skin sensation): 4–7% vs 1% • permanent discontinuation due to adverse events: 4–12% vs 5%
The ranges correspond to the different groups of the trial; values per group are in the publication.
In the phase 2 trial (PMID 37366315) an increase in heart rate was recorded, peaking at 24 weeks and declining afterwards.
These data come from controlled clinical trials. Data outside controlled trials are self-reported and cannot be linked to a known product composition.
Is retatrutide sold in pharmacies in Greece?
Not as an approved medicine. The European Medicines Agency (EMA) medicines database has no entry for retatrutide (checked 25/10/2026), and the US FDA approved-drugs database has no entry either (checked 25/10/2026).
Is retatrutide a medicine?
No. It is not listed in the approved-medicines databases of the EMA or the US FDA (checked 25/10/2026). It is an investigational substance in clinical development.
What stage are the studies at?
Phase 3 trials, including TRIUMPH-1 and TRIUMPH-2, were published in 2026. The clinical development programme includes further trials. The substance remains investigational.
Independent analysis of products sold as "retatrutide"
An independent analysis of products sold as "retatrutide" in Australia (Piatkowski et al., Drug Alcohol Rev 2026, PMID 42559975) examined whether their contents matched the label. The analysis covered a small sample of products, submitted voluntarily and anonymously, and does not generalise to other markets.
What a certificate of analysis (COA) records is the identity of the substance by mass spectrometry, the purity by HPLC and the batch number the analysis refers to.
Sources
- Jastreboff AM et al. N Engl J Med. 2023. PMID 37366315 · DOI 10.1056/NEJMoa2301972 · NCT04881760
- Jastreboff AM et al. N Engl J Med. 2026. PMID 42814954 · DOI 10.1056/NEJMoa2604169 · NCT05929066
- Bellido V et al. Lancet. 2026. PMID 42810372 · DOI 10.1016/S0140-6736(26)01861-1 · NCT05929079
- Piatkowski T et al. Drug Alcohol Rev. 2026. PMID 42559975 · DOI 10.1111/dar.70231
Note
An informational text summarising published research. It is not medical advice or usage guidance.