Sources checked October 18, 2026. This page describes research and access documents, not a treatment recommendation, dosing schedule or safety assessment.
What is retatrutide peptide?
Retatrutide, also identified as LY3437943, is one molecule rather than a mixture of three medicines. The three receptor names are glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1 and glucagon. Lilly's September 29, 2026 announcement describes its ongoing phase 3 development program.[19]
The published TRIUMPH-1 trial used once-weekly injections under the skin. The amounts named below identify research groups, not a starting dose, escalation plan or recommendation for self-administration.[18]
When will retatrutide be available?
Lilly's September 29, 2026 announcement calls retatrutide investigational and says it plans to submit a Biologics License Application to the FDA in the first quarter of 2027. That is a sponsor's planned submission window, not an approval or pharmacy launch date.[19]
ClinicalTrials.gov also carries a separate Lilly pre-approval expanded-access record, NCT07629401. Its August 6, 2026 update lists the program as available and describes individual requests initiated by a treating physician. The record makes access dependent on geography, supply and an individual eligibility assessment; its status does not mean access is available to every reader.[30]
These are distinct routes: a clinical trial follows a study protocol, while the named expanded-access record describes requests outside an ongoing trial. A peptide clinic listing is neither a trial enrollment record nor confirmation of access to this investigational molecule.[30]
What have retatrutide trials measured?
The studies below answer different questions in different populations. Percent weight change, HbA1c percentage-point change and relative liver-fat change are separate measures. The selected results retain the comparison group and follow-up period instead of combining them into one headline.
Phase 2 obesity: 48-week weight measurements
Jastreboff and colleagues' June 2023 NEJM report randomized 338 adults. At week 48, the reported mean weight reduction ranged from 8.7% to 24.2% across retatrutide groups, compared with 2.1% for placebo. The 24.2% figure belongs to the 12-mg research arm; it is not an individual prediction. The primary endpoint was at week 24, not week 48.[1]
Phase 2 diabetes: HbA1c and weight were separate endpoints
Rosenstock and colleagues' June 2023 Lancet report randomized 281 adults with type 2 diabetes; 275 entered the efficacy analysis. At week 24, the 12-mg research arm had a mean HbA1c reduction of 2.02 percentage points, versus 0.01 with placebo and 1.41 with dulaglutide. At week 36, weight reduction in that arm was 16.94%, versus 3.00% and 2.02%, respectively. The HbA1c and weight observations have different units and time points.[2]
Liver-fat substudy: a subset, not another independent trial
Sanyal and colleagues' June 2024 Nature Medicine paper examined 98 participants already included in the phase 2 obesity trial. In the 12-mg group, mean relative liver-fat change was -82.4% at week 24, versus +0.3% with placebo. These are relative MRI liver-fat changes, not body-weight changes. Only 43 participants had week-48 MRI observations, and the study did not measure liver histology. The substudy should not be added to the parent trial's participant count.[3]
TRIUMPH-1: the published 80-week obesity result
The September 29, 2026 NEJM report describes 2,339 randomized adults with obesity without diabetes. At week 80, mean weight change was -17.6%, -23.7% and -25.0% in the 4-, 9- and 12-mg research groups, versus -3.9% with placebo, using the treatment-regimen analysis. Its knee-osteoarthritis and sleep-apnea subgroups overlap the parent population.[18]
The registry currently lists 2,335 enrolled, while the publication says 2,339 randomized. This page preserves the publication's denominator and notes the unresolved difference rather than silently substituting one for the other.[13][18]
TRIUMPH-2: adults with type 2 diabetes
Bellido and colleagues' September 29, 2026 Lancet report randomized 1,152 adults with type 2 diabetes and overweight or obesity. At week 80, the treatment-regimen mean weight changes were -11.9%, -16.8% and -18.8% in the 4-, 9- and 12-mg groups, versus -5.1% with placebo. The analysis included all randomized participants with imputation for missing values; the 965 people who completed study drug were not the analysis denominator.[5]
TRANSCEND-T2D-1: a 40-week diabetes trial
Bajaj and colleagues' June 2026 Lancet report randomized 537 adults whose type 2 diabetes was managed with diet and exercise alone. At week 40, the treatment-regimen mean HbA1c changes were -1.69, -1.86 and -1.94 percentage points in the three retatrutide groups, versus -0.81 with placebo. Weight change was a secondary endpoint. This population and follow-up differ from TRIUMPH-2, so the trials are not interchangeable comparisons.[6]
TRIUMPH-3: sponsor-reported results in severe obesity
Lilly's July 23, 2026 release described 1,949 randomized participants with severe obesity and cardiovascular disease, with or without type 2 diabetes. At week 80, efficacy-estimand mean weight changes were -21.6% and -22.6% for the two retatrutide groups, versus -3.2% with placebo. These observations come from a sponsor release, not a full outcome paper reviewed for this page. The registry lists 1,946 enrolled; that difference remains unresolved.[20][27]
TRIUMPH-4: sponsor-reported weight and knee-pain endpoints
Lilly's December 11, 2025 release described 445 participants with overweight or obesity and knee osteoarthritis, without diabetes. At 68 weeks, efficacy-estimand weight changes were -26.4% and -28.7%, versus -2.1% with placebo. The corresponding treatment-regimen figures were -20.0% and -23.7%, versus -4.6%. Weight change and WOMAC knee-pain score change were co-primary endpoints. The headline 28.7% therefore represents one analysis in one selected population, not a general expected result.[24]
Why do retatrutide weight-loss percentages differ?
An estimand specifies the question an analysis is trying to answer, including how it handles events such as stopping treatment. Lilly's TRIUMPH-1 efficacy estimand assumes participants continued assigned treatment without prohibited weight-management treatments. Its treatment-regimen estimand includes those events.[22]
That distinction explains why TRIUMPH-1 can have a sponsor-reported 28.3% reduction and a published 25.0% reduction for the same research arm. They are not two independent trials. A separate 104-week extension selected eligible completers and changed treatment assignments; its headline is not a placebo-controlled result for everyone originally randomized.[18][22]
TRIUMPH-2 similarly has a sponsor-reported efficacy-estimand reduction of 20.8%, while its published treatment-regimen figure is 18.8%. Comparing headline percentages without the population, time point and analysis definition can compare different questions.[5][19]
How does retatrutide compare with tirzepatide?
A direct comparison is registered as TRIUMPH-5, NCT06662383. The July 20, 2026 registry update describes retatrutide versus tirzepatide in adults with obesity, with estimated enrollment of 800 and estimated completion in December 2026. The record retrieved for this page had no posted results.[31]
Estimated enrollment is a plan, not a reported analysis population. The absence of results in this record does not establish that no report exists elsewhere; it means this registry cannot supply a completed head-to-head result. Separate placebo-controlled trials do not settle that comparison.[31]
What remains unanswered by these sources?
This is a bounded review of original abstracts, the full liver substudy, registry records and named Lilly releases. Full published methods were not accessible for every trial. Sponsor releases are labeled separately rather than presented as independent journal review.
The named studies do not establish an outcome for an individual, an approved prescribing schedule, or equivalence between a research medicine and an online product carrying the same name. This page does not infer a clinical verdict from selected endpoints.
What can the Peptide Therapy directory tell you?
Regenerated.com's September 2026 export of 9,042 US clinic records contains 2,743 records listing Peptide Therapy, across 49 states plus Washington, DC. Source: the September 2026 clinic export, counted in the directory-facts snapshot generated October 17, 2026. This measures our category coverage, not the number of retatrutide prescribers, trial sites or expanded-access providers.
Browse the Peptide Therapy clinic directory to compare recorded services and locations. The same export includes 341 Peptide Therapy records in Florida and 322 in Texas; the Florida Peptide Therapy directory and Texas Peptide Therapy directory provide geographic browsing. Live counts can differ from the dated export.
For a provider conversation, distinguish the exact substance from a broad peptide-service label. Ask whether a discussion concerns a registered trial, a physician-initiated expanded-access request, or another service. Request the specific study identifier or access documentation rather than treating a directory listing as evidence of eligibility. A listing is not an endorsement.