Retatrutide's first phase 3 results: about a quarter of body weight lost
The TRIUMPH-1 trial of Eli Lilly's triple-hormone drug reported up to 25% average weight loss over 80 weeks. It isn't approved yet, and FDA has warned companies selling it online.
The result
In TRIUMPH-1, 2,339 adults with obesity (but without diabetes) took a weekly retatrutide injection or a placebo for 80 weeks. Average weight loss was 17.6%, 23.7% and 25.0% on the three doses, compared with 3.9% on placebo. In people who also had knee osteoarthritis or sleep apnea, knee pain and breathing interruptions improved too. Stomach-related side effects were the most common.
What happens next
Lilly says its data package is complete and plans to apply for FDA approval in the first quarter of 2027. Until then, retatrutide is an investigational drug.
About the versions sold online
Retatrutide isn’t approved for any use, and FDA says it can’t legally be compounded. FDA has warned companies selling it as “for research purposes” or “not for human consumption,” and no regulator has checked what’s actually in those products. It’s also banned in sport as a drug still in development.
Learn more
Our Retatrutide guide covers all the trials, side effects and open questions.
Sources
- Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1), N Engl J Med, 2026 · PubMed (U.S. National Library of Medicine)
- Lilly Reports Second-Quarter 2026 Financial Results (Form 8-K exhibit, Aug 5, 2026) · Eli Lilly and Company, via U.S. Securities and Exchange Commission
- FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss · U.S. Food and Drug Administration