A Phase 3b, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate Retatrutide Treatment in the Maintenance of Weight Reduction in Individuals With Obesity

ClinicalTrials3 Mar 2026·Phase 3● 7/10i

A Phase 3b, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate Retatrutide Treatment in the Maintenance of Weight Reduction in Individuals With Obesity

Eli Lilly and Company

Phase 3b trial evaluates retatrutide's ability to maintain weight loss in people with obesity through an 80-week open-label lead-in followed by 36-week randomized withdrawal to placebo or continued treatment. The study enrolls 643 participants with completion expected in April 2028, testing two retatrutide doses against placebo switch. This addresses a critical commercial question for Eli Lilly: whether people can maintain weight loss after achieving it, a key payer concern for obesity drugs. The withdrawal design mirrors successful maintenance studies that supported Wegovy's market access positioning.

Strategic signal

Weight maintenance data will be essential for Eli Lilly's retatrutide market access strategy, as payers increasingly demand evidence that obesity drugs provide sustained benefit beyond initial weight loss. The withdrawal design provides the strongest possible evidence framework, following the precedent set by Wegovy's STEP trials that demonstrated weight regain after discontinuation. Success here positions retatrutide against tirzepatide's existing obesity franchise by demonstrating differentiated durability, while failure could limit formulary placement regardless of initial efficacy data.

Weight lossGLP-1Eli Lilly

Original Abstract

This is a study of retatrutide in participants with obesity. The main purpose is to learn more about how retatrutide maintains body weight loss. The study will have two treatment phases: an 80 week lead-in phase in which all participants will take retatrutide dose 1 and a 36 week randomized, double-blinded phase in which participants will either take retatrutide dose 1, retatrutide dose 2, or switch to placebo. Participation in the study will last around 125 weeks. | Condition(s): Obesity | Primary endpoint(s): Percent Change from Baseline in Body Weight | Enrollment: 643 (estimated) | Phase: Phase 3 | Sponsor: Eli Lilly and Company | Expected completion: 2028-04 | Status: Active Not Recruiting | Last update: 2026-03-03

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