Lilly's Retatrutide Achieves 16.8% Weight Loss and A1C Reductions in Phase 3 Diabetes Trial, Comparable to Mounjaro

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Eli Lilly's retatrutide, a triple hormone agonist (GLP-1, GIP, glucagon), met primary endpoints in the 40-week TRANSCEND-T2D-1 phase 3 trial for type 2 diabetes, with A1C reductions of 1.7% (4mg), 1.9% (9mg), and 1.9% (12mg) doses124.

Patients on the 12mg dose lost 16.8% body weight (efficacy estimand) or 15.3% (all patients), outperforming placebo (2.5-2.6%) with no plateau observed124.

Results are competitive with Mounjaro (tirzepatide), showing similar A1C efficacy and notable weight loss in diabetes patients where it's typically harder14.

Common side effects were gastrointestinal (nausea, diarrhea, vomiting), with 5.1% discontinuation at 12mg dose12.

Lilly plans obesity regulatory submission by end-2026, diabetes in 2027; full data at ADA 202613.

Sources:

1. https://www.fiercebiotech.com/biotech/eli-lilly-retatrutide-type-2-diabetes-weight-loss-ph-3-data

2. https://www.techtarget.com/pharmalifesciences/news/366640348/Lillys-triple-G-agonist-shows-unique-promise-in-late-stage-diabetes-trial

3. https://www.clinicaltrialsarena.com/news/lillys-triple-g-agonist-succeeds-in-phase-iii-diabetes-trial/

4. https://www.statnews.com/2026/03/19/eli-lilly-triple-g-retatrutide-results/