On May 21, 2026, Eli Lilly released Phase 3 results from the TRIUMPH-1 trial. Retatrutide — a triple hormone receptor agonist targeting GLP-1, GIP, and glucagon receptors simultaneously — delivered an average 28.3% body weight loss at the highest dose (12mg) over 80 weeks. Among the 2,339 participants, 45.3% lost 30% or more of their body weight, a threshold previously achievable only through bariatric surgery.
How Retatrutide Compares
| Medication | Targets | Avg Weight Loss | Trial Duration | Status |
|---|---|---|---|---|
| Retatrutide 12mg | GLP-1 + GIP + Glucagon | 28.3% | 80 weeks | Phase 3 complete, not yet approved |
| Tirzepatide 15mg | GLP-1 + GIP | ~21% | 72 weeks | FDA-approved (Zepbound) |
| Semaglutide 2.4mg | GLP-1 | ~15% | 68 weeks | FDA-approved (Wegovy) |
| Foundayo 36mg | GLP-1 (small molecule) | ~12% | 72 weeks | FDA-approved (oral) |
| Retatrutide 4mg | GLP-1 + GIP + Glucagon | 19.0% | 80 weeks | Phase 3 complete, not yet approved |
The Third Receptor: What Glucagon Adds
Current GLP-1 medications target one receptor (semaglutide) or two (tirzepatide). Retatrutide adds glucagon receptor activation — the hormone that raises blood sugar and promotes fat breakdown. In combination with GLP-1 and GIP, glucagon activation appears to accelerate fat oxidation and increase energy expenditure beyond what dual-receptor drugs achieve.
This triple mechanism explains both the higher weight loss and some concerns: glucagon raises blood sugar, which creates a delicate balance in patients with type 2 diabetes. The TRANSCEND-T2D-1 trial (March 2026) showed 16.8% weight loss in diabetic patients at 40 weeks, suggesting efficacy is maintained but may be moderated.
The Extension Data: 30% at Two Years
A subset of 532 participants with severe obesity (BMI ≥35) who continued retatrutide in a study extension lost up to 30.3% of body weight — an average of 85 pounds — at 104 weeks. This two-year data point is significant because it suggests the weight loss trajectory doesn't plateau as sharply as with current medications.
When Will Retatrutide Be Available?
Eli Lilly is expected to file for FDA approval later in 2026, with potential market availability in 2027. Additional TRIUMPH trials are expected to report throughout 2026, including data from the American Diabetes Association Scientific Sessions in June.
What This Means for You Today
Retatrutide isn't available yet. If you're considering GLP-1 treatment now, today's options — semaglutide and tirzepatide — remain highly effective. Don't wait for a future drug when proven treatments can help you now.
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