Retatrutide Phase 3 Trials: The TRANSCEND Program Explained

Medically reviewed by Dr. Sarah Chen, PharmD, BCPS

Retatrutide is advancing through one of the most comprehensive Phase 3 clinical trial programs in obesity and diabetes history. This article maps out the TRANSCEND and TRIUMPH trial programs, their designs, endpoints, and what results mean for potential FDA approval.

The Road to FDA Approval

Following the remarkable Phase 2 results, Eli Lilly launched an extensive Phase 3 clinical development program for retatrutide. This program encompasses multiple large-scale trials designed to confirm efficacy and safety across different patient populations and conditions. Understanding these trials provides insight into when retatrutide might reach the market and for which indications.

The TRANSCEND Program

TRANSCEND (Triple Receptor Agonist iN cardiometabolic Syndromes, Cardiovascular Endpoints, aNd Diabetes) is the umbrella name for retatrutide's core Phase 3 trials.

TRANSCEND-T2D-1 (Type 2 Diabetes)

Status: First results announced March 2026

This was the first Phase 3 trial to report results. It evaluated retatrutide in adults with type 2 diabetes who were inadequately controlled on metformin alone or metformin plus a second oral diabetes medication.

Key results:

Primary endpoint met: A1C reduction of 1.7% to 2.0% across doses at 40 weeks

Weight loss: Up to 16.8% (approximately 36.6 pounds) at the 12 mg dose

All retatrutide doses were superior to placebo for A1C reduction

These results confirm the Phase 2 findings and position retatrutide as a highly effective option for type 2 diabetes management [1].

TRANSCEND-OB (Obesity)

Status: Results expected 2026

This trial evaluates retatrutide in adults with obesity (BMI ≥30) or overweight (BMI ≥27) with at least one weight-related comorbidity, but without type 2 diabetes. The primary endpoint is percentage change in body weight from baseline.

This is the pivotal trial for an obesity indication and will determine whether retatrutide can replicate the ~24% weight loss seen in Phase 2 in a larger, more diverse population.

TRANSCEND-CV (Cardiovascular Outcomes)

ClinicalTrials.gov: NCT06383390

This is a large cardiovascular outcomes trial (CVOT) designed to determine whether retatrutide can reduce the incidence of major adverse cardiovascular events (MACE) — heart attack, stroke, and cardiovascular death — in people with obesity and established cardiovascular disease.

CVOTs are increasingly important for obesity drugs, as the FDA and payors want evidence that weight loss translates into reduced cardiovascular risk. Semaglutide's SELECT trial demonstrated cardiovascular benefit, setting a precedent that retatrutide will need to match or exceed.

TRANSCEND-OB+CV (Obesity with Cardiovascular Disease)

ClinicalTrials.gov: NCT05882045

This trial specifically evaluates retatrutide in adults with obesity AND established cardiovascular disease, focusing on both weight loss efficacy and cardiovascular safety in this high-risk population.

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The TRIUMPH Program

Beyond the core TRANSCEND trials, Eli Lilly has launched the TRIUMPH program to evaluate retatrutide in obesity-related comorbidities:

TRIUMPH (Obesity Comorbidities)

ClinicalTrials.gov: Referenced in design paper [2]

The TRIUMPH registrational program evaluates retatrutide for specific obesity-related conditions:

Obstructive Sleep Apnea (OSA): Testing whether retatrutide-induced weight loss can reduce the severity of sleep apnea, potentially eliminating the need for CPAP therapy

Knee Osteoarthritis: Evaluating whether weight loss with retatrutide improves knee pain and function in people with obesity-related osteoarthritis

These indication-specific trials are important because they could lead to FDA approvals for retatrutide in these specific conditions, expanding its market beyond general obesity treatment.

Weight Maintenance Trial

ClinicalTrials.gov: NCT06859268

A separate trial is evaluating retatrutide's ability to maintain weight loss over extended periods. Weight regain after discontinuation is a significant concern with all anti-obesity medications, and this trial will provide critical data on long-term weight maintenance strategies.

Timeline to Market

Based on the current trial program:

2026-2027: Phase 3 results expected from major trials

2027-2028: Potential FDA submission (New Drug Application)

2028-2029: Potential FDA approval (if trials are successful)

However, timelines can shift based on trial results, regulatory requirements, and manufacturing considerations. Eli Lilly has stated that retatrutide is a priority program.

What Approval Could Mean

If approved, retatrutide would enter a rapidly growing market alongside semaglutide and tirzepatide. Its unique triple-agonist mechanism and potentially superior efficacy for weight loss and liver fat reduction could differentiate it from existing options. The liver fat reduction data, in particular, could position retatrutide as the preferred option for patients with concurrent obesity and fatty liver disease.

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References

Eli Lilly Press Release. "Lilly's triple agonist, retatrutide, demonstrated significant reductions in A1C and weight in first Phase 3 trial for treatment of type 2 diabetes." March 2026. Source

"Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational program." Obesity. 2025. PubMed: 41090431

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