Retatrutide Phase 3: Up to 28 % weight loss in TRIUMPH

The triple agonist retatrutide (LY3437943) from Eli Lilly has demonstrated the strongest weight reduction ever recorded in a randomized Phase 3 trial of a GLP-1-class compound. Results from December 2025 and May 2026 mark a milestone in obesity research.

What are the specific TRIUMPH trial results?

TRIUMPH-1 (May 2026) enrolled 2,339 participants with obesity or overweight. At 80 weeks, patients on 12 mg weekly retatrutide lost an average of 28.3 % of their body weight (approx. 31.9 kg / 70.3 lbs), those on 9 mg lost 25.9 %, and those on 4 mg lost 19.0 %. The placebo group lost only 2.2 %. Earlier, TRIUMPH-4 (December 2025) showed a 28.7 % weight loss in participants with knee osteoarthritis, alongside a 75.8 % reduction in knee pain (WOMAC score). More than 1 in 8 patients were completely pain-free by the end of the trial.

What other endpoints were achieved?

Beyond weight loss, retatrutide showed significant improvements in secondary endpoints:

• Prediabetes reversal: 72 % of affected participants normalized their blood sugar status.
• LDL cholesterol: Reduction of approximately 20 %.
• Liver fat: In the Phase 2 extension, 93 % of participants on 12 mg achieved normalized liver fat content at 48 weeks.
• Type 2 diabetes (TRANSCEND-T2D-1): HbA1c reduction of 1.7–2.0 % and 16.8 % weight loss (approx. 16.6 kg) at 40 weeks.

What is the safety profile?

The most common adverse events were gastrointestinal (nausea, vomiting, diarrhea), typical for GLP-1 agonists. Discontinuation rates due to adverse events were 11.3 % on 12 mg, 6.9 % on 9 mg, and 4.1 % on 4 mg (placebo: 4.9 %). Dysesthesia (skin sensations) occurred in up to 20.9 % of the 12 mg group, were generally mild, and rarely led to discontinuation.

When can approval be expected?

Retatrutide is not FDA or EMA approved. An NDA submission to the FDA is expected in Q4 2026, with a decision realistically in 2027 or later. Seven additional Phase 3 readouts are expected in 2026, including trials for obstructive sleep apnea and MASLD (metabolic fatty liver disease).

For detailed information on the mechanism of action and evidence level, visit our retatrutide peptide page. A comparison with the dual agonist tirzepatide is available on the tirzepatide article.

Not medical advice. This article is for informational purposes only about the current state of clinical research. Retatrutide is not an approved medication and should not be used without medical supervision.