Short answer: Retatrutide (LY3437943) is a triple hormone receptor agonist (GIP + GLP-1 + glucagon) being developed by Eli Lilly to treat obesity and type 2 diabetes. In a Phase 2 clinical trial published in the NEJM, it produced an average weight loss of 24.2% over 48 weeks. However, retatrutide has NOT yet been APPROVED by the FDA, the EMA or the MHRA. The medicine is still in Phase 3 (TRIUMPH) trials. No retatrutide product sold on the market or online is legal or safe; buying or using it is strongly advised against.
What is retatrutide and how does it work?
Conventional GLP-1 medicines usually work through a single or dual hormone mechanism:
- Wegovy and Ozempic (semaglutide): Stimulate only GLP-1 receptors.
- Mounjaro and Zepbound (tirzepatide): Stimulate two receptors, both GIP and GLP-1.
- Retatrutide ("Reta"): Has a triple (triple agonist) mechanism: GIP + GLP-1 + glucagon.
What does adding a third hormone (glucagon) change?
Stimulating the glucagon receptor speeds up fat burning in the liver and increases the basal metabolic rate (energy expenditure). As a result, it does not just suppress appetite; it also raises the number of calories the body burns.
Clinical research data: the NEJM Phase 2 trial
Phase 2 trial results published in 2023 in the respected medical journal The New England Journal of Medicine (NEJM):
- Participants: 338 adult participants with a body mass index (BMI) of 30 or above.
- Result at 48 weeks: In the highest-dose 12 mg group, average body weight loss was 24.2% (about 26 kg).
- Fatty liver: In participants who had fatty liver at the start, liver fat fell to the normal range (below 5%) at 24 weeks in 86% of those on the 12 mg dose (Sanyal et al., Nature Medicine 2024).
Retatrutide FDA approval process and timeline
For a medicine to move from clinical trials to prescription sale in pharmacies, it must fully complete all 3 phases and obtain regulatory approval:
| Stage | Status | Date |
|---|---|---|
| Phase 1 (safety and dosing) | Completed | 2021 |
| Phase 2 (efficacy and dose range) | Completed (published in NEJM) | 2023 |
| Phase 3 (TRIUMPH programme) | Ongoing, results being reported | Ongoing |
| Marketing application | No approval anywhere yet | Check Eli Lilly and FDA, EMA or MHRA announcements |
| Launch and prescription sale | Not approved | Check Eli Lilly and FDA, EMA or MHRA announcements |
Retatrutide has no approval anywhere yet, and we do not predict dates. For the current status, check announcements from Eli Lilly and from the FDA, the EMA or the MHRA.
Critical medical and legal warning: why you should not buy it
Recently, products in vial or powder form have been seen for sale on websites, on social media and through illegal channels under names such as "retatrutide peptide" or "research chemical".
Health professionals and medical authorities give these vital warnings about such products:
- No licence and no legal sale: There is not yet an approved commercial retatrutide medicine in any country in the world.
- Sterility and purity risk: Heavy metal residues, bacterial contamination and incorrect dosing have been found in these substances, which are made in unregulated backstreet labs.
- Heart rate and arrhythmia risk: Activation of the glucagon receptor can cause temporary increases in heart rate. The long-term safety of this has not yet been established in Phase 3 trials. Using it without medical supervision can be life-threatening for the heart.
- Legal liability: Importing and selling unauthorised molecules is illegal.
Advice: During your weight-loss journey, choose only official medicines prescribed by your doctor and approved by the FDA, the EMA or the MHRA (Mounjaro, Wegovy, Ozempic, Saxenda and so on).
Frequently asked questions
When will retatrutide be available in pharmacies?
Retatrutide is not approved anywhere yet. Eli Lilly's Phase 3 TRIUMPH trials are ongoing and their results are being reported. No launch date can be given; for the current status, check announcements from Eli Lilly and from the FDA, the EMA or the MHRA.
Is retatrutide more effective than Mounjaro?
According to Phase 2 data, retatrutide produced an average weight loss of 24.2%, while Mounjaro (tirzepatide) produced an average weight loss of 20.9% over 72 weeks. However, Phase 3 trials involving thousands of patients need to be completed before these results can be confirmed.
Is it safe to take retatrutide now?
No, it is definitely not safe. The medicine has not been approved and there is no legal sale on the market. Forms sold online are unregulated and carry serious health risks.
Sources:
- Jastreboff AM, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. N Engl J Med 2023; 389:514-526. DOI: 10.1056/NEJMoa2301972
- Sanyal AJ, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nat Med 2024.
- U.S. National Library of Medicine. TRIUMPH-1 ClinicalTrials.gov Identifier: NCT05929066
