Retatrutide Results in the Clinical Trials

The short version

Retatrutide results from Phase 2 clinical trials show the largest weight reductions ever reported in a randomized drug trial: 24.2% mean body-weight reduction at 48 weeks at the highest dose ^[1]. Phase 3 data are now appearing: the first Phase 3 result in type 2 diabetes (TRANSCEND-T2D-1) confirms the signal with −15.3% body weight and −1.94% HbA1c at 40 weeks ^[12].

This page presents the retatrutide results precisely as the trials measured them. Every percentage, timepoint, and n-value is cited. The results also include the safety signals — because efficacy figures without safety context are half a picture — and the durability question: what the literature says about results after stopping, which is the defining open question for this compound class as of 2026.

Obesity Phase 2 results (48 weeks)

Trial: NCT04644640. n=338 adults. BMI ≥30 or 27–<30 with comorbidity. No T2D. Once-weekly subcutaneous, 48 weeks ^[1].

Secondary endpoints at 12 mg:

• Waist circumference: reduced approximately 19.6 cm.
• GI adverse events: nausea in up to 45%, dose-related, predominantly mild-to-moderate.
• Discontinuation due to AEs: 18% at 12 mg.
• Heart rate: dose-dependent increase, peaking approximately week 24.

A 2025 commentary characterizes the −24.2% figure as a step-change in the incretin-pharmacotherapy class — the largest weight reduction measured in a randomized drug trial to that point ^[6]. A 2024 review places the tri-agonist mechanism as the pharmacological basis for weight reductions approaching bariatric-surgery magnitude ^[11].

Type 2 diabetes Phase 2 results (36 weeks)

Trial: NCT04867785. n=281 adults with T2D, inadequate control on background therapy. Once-weekly subcutaneous with stepwise escalation, 36 weeks ^[2].

Primary results at 12 mg:

• HbA1c change at 24 weeks: −2.02% versus −0.01% for placebo.
• Body weight at 36 weeks: −16.94% versus −3.00% for placebo.
• GI AEs: mild-to-moderate in 35%.
• Severe hypoglycemia: none. Deaths: none.

The glycemic efficacy (−2.02% HbA1c) is among the largest reported for any antidiabetic agent. The weight effect in the diabetic population (−16.94%) is numerically lower than the obesity Phase 2 result (−24.2%), consistent with the metabolic context of T2D.

MASLD Phase 2a results (24–48 weeks)

Trial: NCT04881760 (substudy). n=98 participants with obesity/overweight and MASLD (≥10% liver fat by MRI-PDFF), without T2D. Once-weekly, 48 weeks ^[5].

Liver-fat reductions at 24 weeks by dose:

• 1 mg: −42.9%
• 4 mg: −57.0%
• 8 mg: −81.4%
• 12 mg: −82.4% (versus +0.3% for placebo)

At 12 mg, 86% of participants reached normal liver fat (<5%) by 24 weeks. Reductions were sustained and deepened to week 48 (−86.0% at 12 mg).

An incretin-therapy review identifies these liver-fat reductions as part of the broad cardiometabolic benefit profile of GIPR/GCGR/GLP-1R agonists ^[9].

Phase 3: TRANSCEND-T2D-1 results (40 weeks)

Trial: NCT05929066 (TRANSCEND-T2D-1). n=537 adults with T2D inadequately controlled with diet and exercise. Retatrutide 12 mg versus placebo, 40 weeks ^[12].

Primary results:

• HbA1c: −1.94% (retatrutide 12 mg) versus −0.81% (placebo).
• Body weight: −15.3% versus −2.6%.
• Adverse events: predominantly mild-to-moderate GI; discontinuation due to AEs in 8.3% of the retatrutide arm.
• Severe hypoglycemia: none reported.

The TRANSCEND-T2D-1 results provide the first Phase 3 confirmation that the Phase 2 efficacy signal replicates. They are the first entry in the regulatory evidence package Eli Lilly will need for approval submissions.

Retatrutide results after stopping: the durability record

No dedicated off-treatment follow-up trial for retatrutide has published results as of mid-2026. The durability question is answered, imperfectly, by the class literature.

A 2025 observational study documented substantial weight regain after interrupting liraglutide, semaglutide, and tirzepatide — all GLP-1-containing agents ^[7]. A 2026 review specifically identifies weight regain upon discontinuation as the principal limitation of the current incretin-therapy class, characterizes retatrutide's multi-receptor pharmacology as the most promising approach for improved durability, and acknowledges that clinical evidence for post-discontinuation durability advantage from the glucagon-receptor addition remains limited ^[13].

A mechanistic 2026 review of glucagon's role in obesity pharmacotherapy notes that the glucagon-receptor arm in triple agonists may theoretically drive more lasting metabolic adaptation through energy expenditure and hepatic lipid pathway changes — but frames this as a hypothesis requiring prospective data ^[15].

The TRIUMPH Phase 3 program includes trials designed to provide off-treatment follow-up. When those data are published, this page will reflect them. Until then, the retatrutide results record on discontinuation is: large Phase 2 on-treatment efficacy, open off-treatment question.