Retatrutide Clinical Trials
Retatrutide (LY3437943) is studied in three Phase 3 programs: TRIUMPH (obesity), TRANSCEND (type 2 diabetes) and SYNERGY (MASLD/MASH). All four TRIUMPH obesity trials have reported, with up to 28.3% weight loss at 80 weeks, and TRIUMPH-1 and TRIUMPH-2 were published in the New England Journal of Medicine and The Lancet in September 2026. Some studies are still recruiting: find a trial site near you.
Development Program Overview
For a narrative walk-through of the Phase 3 programs see TRIUMPH, TRANSCEND and SYNERGY explained; for a sortable table of every registered trial see the clinical trial tracker; to see which studies are still enrolling and where, use Find a Trial.
Eli Lilly's retatrutide program spans three Phase 3 families: TRIUMPH (obesity/weight management), TRANSCEND (type 2 diabetes), and SYNERGY (MASLD/MASH liver disease). TRIUMPH-4 delivered the first Phase 3 readout in December 2025, showing 28.7% weight loss at 12 mg/68 weeks. All five pivotal readouts had reported by July 2026, the head-to-head TRANSCEND-T2D-2 trial against semaglutide reported in October 2026, and Lilly says it plans to file for approval no later than the first quarter of 2027.
Development Timeline
All Trials
TRIUMPH-1
TRIUMPH-1: Phase 3 Pivotal Obesity Trial of Retatrutide (Results-Published)
Retatrutide's main Phase 3 obesity trial (2,339 adults, 80 weeks): 28.3% average weight loss at 12 mg. Published in NEJM, September 2026.
TRIUMPH-9 (Dose Escalation Optimization)
Phase 3b Dosing Optimization Study for Retatrutide
Investigating different retatrutide dose escalation schemes to optimize efficacy-tolerability balance.
SYNERGY-OUTCOMES
SYNERGY-OUTCOMES Trial: Retatrutide for Liver Disease (MASH)
SYNERGY-OUTCOMES is a Phase 3 trial testing retatrutide and tirzepatide against placebo for preventing serious liver events in high-risk MASLD/MASH.
TRANSCEND-T2D-2
TRANSCEND-T2D-2: Retatrutide vs Semaglutide
First head-to-head trial vs semaglutide 2 mg (Ozempic), 1,298 adults with type 2 diabetes: A1C down 2.2 vs 1.8 points, weight down up to 20.9% vs 9.4%.
TRIUMPH-4
TRIUMPH-4: Obesity with Knee Osteoarthritis (First Phase 3 Readout)
The first Phase 3 retatrutide trial to report: 28.7% weight loss at 12 mg over 68 weeks and knee pain (WOMAC) down as much as 75.8% in obesity with knee OA.
Phase 1 Japan Study
Phase 1 Study in Japanese Subjects (NCT04823208)
A Phase 1 multiple-dose study (NCT04823208) of retatrutide's safety, blood levels and effects in Japanese adults with type 2 diabetes.
Phase 2 Body Composition Substudy
Phase 2 Body Composition Substudy
DXA scans from the Phase 2 type 2 diabetes trial: fat mass fell 26.1% on 8 mg and 23.2% on 12 mg at 36 weeks, vs 4.5% on placebo.
Phase 2 CKD Trial
Phase 2 Chronic Kidney Disease Trial (NCT05936151)
A Phase 2 trial (NCT05936151) of retatrutide in adults with chronic kidney disease and overweight or obesity, looking at kidney function and weight.
Phase 2 MASLD Substudy
Phase 2 MASLD/MASH Substudy (Liver Fat Analysis)
A planned substudy of the Phase 2 obesity trial that measured liver fat by MRI in people with fatty liver disease (MASLD). Results and what they mean.
TRANSCEND-T2D-1
TRANSCEND-T2D-1: Phase 3 Type 2 Diabetes Trial (Results-Published)
Phase 3 trial of retatrutide in 537 adults with type 2 diabetes, published in The Lancet in June 2026: A1C down 1.94 points and weight down 15.3% at 12 mg.
TRIUMPH-3
TRIUMPH-3: Retatrutide in Severe Obesity With Cardiovascular Disease
Phase 3, 1,949 adults with BMI 35+ and CVD, 80 weeks: -22.6% weight loss at 12 mg vs -3.2%, triglycerides -37%, hsCRP -51%; MACE-5 HR 0.82, not significant.
TRIUMPH-Outcomes
TRIUMPH-Outcomes: Cardiovascular Outcomes Trial (CVOT)
A large, still-running trial testing whether retatrutide lowers heart attacks, strokes and heart deaths in adults with obesity and cardiovascular disease.
TRIUMPH-2
TRIUMPH-2: Retatrutide in Obesity With Type 2 Diabetes (Results)
Phase 3, 1,152 adults, 80 weeks. Topline July 23, 2026: -20.8% weight loss and A1C -1.5 points at 12 mg vs -4.0% and -0.2 on placebo; dysesthesia 7.3%.
Phase 2 Type 2 Diabetes Trial
Phase 2 Type 2 Diabetes Trial of Retatrutide (NCT04867785)
Phase 2 trial (NCT04867785, 281 adults): A1C fell up to 2.02 points at 24 weeks and weight up to 16.9% at 36 weeks on 12 mg, vs placebo and dulaglutide.
Phase 1b MAD Trial
Phase 1b Multiple Ascending Dose Trial (NCT04143802)
Phase 1b trial (NCT04143802) in adults with type 2 diabetes: rising weekly doses of retatrutide vs placebo, testing safety, blood levels and glucose effects.
Phase 2 Obesity Trial
Retatrutide Phase 2 Obesity Trial: -24.2% Weight Loss
In the Phase 2 obesity trial (n=338), retatrutide produced up to -24.2% mean weight loss at 12 mg over 48 weeks. The headline result, doses, and safety data.
First-in-Human Study
Retatrutide Phase 1 Trial: First Human Study (2019)
Retatrutide's first human study began in 2019 and showed a half-life of about 6 days, allowing weekly dosing. Design, safety and early results.