Retatrutide Clinical Trials: Phase 1, Phase 2 and Phase 3

How to read the clinical program

This page organizes the clinical development of LY3437943. It is not a schedule table or a “best arm” summary. Phases answer different questions: Phase 1 explores early safety and pharmacology; Phase 2 estimates effect and tolerability in defined populations; Phase 3 enlarges that question in larger, often registrational, trials.

Detailed 2026 announcement figures are in what the TRIUMPH studies have reported. The index is the Retatrutide research hub.

Early development and proof of concept

Coskun and colleagues, in Cell Metabolism (2022), follow LY3437943 from discovery through a clinical proof of concept. That publication is peer-reviewed primary research. It places the peptide in early human evaluation within the same discovery account, not as a Phase 3 registry record.¹

Phase 1b — Urva et al., 2022

Population: people with type 2 diabetes. Typical Phase 1b purpose: safety, tolerability, pharmacokinetics, and pharmacodynamic signals in a limited number of participants. Publication: The Lancet, 2022. The paper includes authors affiliated with Lilly.²

Limits: it is not a Phase 3 trial and is not an authorization. Study arms, if consulted in the paper, are protocol conditions. This page does not reproduce them as a use guide.

Phase 2 obesity — Jastreboff et al., 2023

Registry: NCT04881760. Participants: 338 adults. Duration reported in the paper: 48 weeks, with a primary endpoint of percent body-weight change at 24 weeks. The trial was funded by Eli Lilly.^3,5

What was studied: effect and safety in that population, versus placebo, under a Phase 2 protocol. What is not concluded here: a use schedule, a comparison with TRIUMPH, or an authorization. Percentages from that trial belong to that population and duration.

Phase 2 type 2 diabetes — Rosenstock et al., 2023

Registry: NCT04867785. Participants: 281. This trial is distinct from Jastreboff’s: different population, different registry ID, different journal. They should not be merged into “the Phase 2 trial.”^4,6

Why the distinction matters: a reader who cites only NEJM 2023 omits Phase 2 evidence in type 2 diabetes. A reader who treats both trials as one study loses inclusion criteria and endpoints.

TRIUMPH Phase 3 program

Phase 3 usually seeks confirmation in larger populations and, in many programs, support for a regulatory application. Completing or announcing a Phase 3 trial is not that authorization. TRIUMPH is Lilly’s Phase 3 program name for retatrutide in obesity and related conditions. Protocols are on ClinicalTrials.gov.

A ClinicalTrials.gov record typically includes title, phase, criteria, endpoints, enrollment, and status. It is useful for seeing what was planned and how the protocol stood on the review date. It does not replace a paper: it does not supply a journal’s full statistical analysis or limitations discussion.

TRIUMPH-1

NCT05929066. A randomized, double-blind, placebo-controlled trial in participants without type 2 diabetes who have obesity or overweight, including knee osteoarthritis and obstructive sleep apnea subsets. The registry lists actual enrollment of 2,335 participants and a primary endpoint of percent body-weight change at week 80.⁷

Registry status as reviewed September 1, 2026: Completed. Additional evidence: Lilly announced topline results on May 21, 2026. View NCT05929066.^7,11

TRIUMPH-2

NCT05929079. A trial in participants with type 2 diabetes who have obesity or overweight, including an obstructive sleep apnea subset. The registry lists actual enrollment of 1,152 participants and a primary endpoint of percent body-weight change at week 80.⁸

Registry status as reviewed September 1, 2026: Active, not recruiting. Additional evidence: Lilly announced topline results on July 23, 2026. Those two statements are not contradictory. View NCT05929079.^8,12

TRIUMPH-3

NCT05882045. A trial in participants with severe obesity and established cardiovascular disease. The registry lists actual enrollment of 1,946 participants and a primary endpoint of percent body-weight change at week 80.⁹

Registry status as reviewed September 1, 2026: Active, not recruiting. Additional evidence: Lilly announced topline results on July 23, 2026. View NCT05882045.^9,12

TRIUMPH-Outcomes

NCT06383390. A cardiovascular and kidney outcomes trial in adults with obesity. The registry lists estimated enrollment of 10,000 participants and an estimated primary completion in 2029.¹⁰

Registry status as reviewed September 1, 2026: Active, not recruiting. In the reviewed sources there is no completed outcomes result. View NCT06383390.¹⁰

Trial table

Registry status versus topline result

ClinicalTrials.gov describes recruitment and administrative protocol status. A Lilly release describes an initial results summary. A journal article describes a peer-reviewed analysis. TRIUMPH-2 and TRIUMPH-3 illustrate the difference: sponsor topline results exist and, as of this review, the registry records remain Active, not recruiting.^8,9,12

Registry status is not inferred from the release. Peer-reviewed publication is not inferred from a Completed status.

Finished or positive research versus approval

A trial can finish, meet its primary endpoint, or be announced as positive and still not exist as an authorized medicine. Retatrutide remains an investigational compound and is not currently approved by the FDA. A completed clinical phase or a positive result is not a regulatory authorization.¹³