How Long Were Participants on Retatrutide in the Trials?
Trial durations for retatrutide by arm, from the 48-week phase 2 study to the 80- and 104-week phase 3 records, and what registry entries plan next.
Research use only. This page provides scientific background and community-report context. Every compound sold here is supplied strictly for in-vitro research. Nothing on this page is a protocol, a recommendation, or medical advice.
TL;DR: published results, extension reports, and registry plans
Research question: How long were participants treated in the retatrutide trials, and what is the longest documented exposure?
What the published data say: the longest peer-reviewed retatrutide result covers 48 weeks in the phase 2 trial enrolling adults with obesity. [PMID 37366315]
Limits of the documented evidence: indefinite exposure is outside the time frames documented here; the longest registry window is a plan for approximately 248 weeks without results. [NCT06383390]
What research communities report: In the Reddit corpus we track, 152 question posts in 12 months and 6 in the 4 to 12 September 2026 window matched this question pattern. These are reports, not evidence of frequency or an appropriate treatment duration.
How long did the published trials run?
The longest peer-reviewed retatrutide exposure was 48 weeks in the phase 2 trial enrolling adults with obesity; the longest peer-reviewed phase 3 exposure was 40 weeks in participants with type 2 diabetes. The trial phase describes the development stage, so the later phase does not automatically mean longer observation. [PMID 37366315; PMID 42250575]
Jastreboff's trial included 338 adults and compared once-weekly subcutaneous retatrutide study arms spanning 1 to 12 mg with placebo over 48 weeks. These are the study arms of the cited trials, not an application protocol for research vials. Its primary endpoint was at week 24, while the week-48 body-weight endpoint was secondary. Calling it a 24-week study alone leaves out the later observation period. [PMID 37366315; NCT04881760]
- Retatrutide observation window
- 48 weeks; primary endpoint at week 24
- Comparator
- Placebo
- Evidence source
- PMID 37366315
- Retatrutide observation window
- 40 weeks
- Comparator
- Placebo
- Evidence source
- PMID 42250575
Bajaj's phase 3 publication reports 537 randomized participants. That count belongs to the published trial, while the phase 2 count belongs to Jastreboff's report. Neither publication documents an exposure extending to the longer windows described in the later registry records. [PMID 42250575; PMID 37366315]
What is the longest documented exposure?
The longest reported exposure is the TRIUMPH-1 extension at week 104, described in a company release that is not peer reviewed. The registry separates the primary body-weight endpoint at week 80 from the extension endpoint at week 104 and describes an additional 24 weeks after the placebo-controlled period. [Eli Lilly, 21 May 2026; NCT05929066]
The company release reports 2,339 randomized participants and an extension subset of 532 participants with baseline BMI of at least 35. In that extension subset with baseline BMI of at least 35, the company release, not peer reviewed, reports a mean body-weight reduction of 30.3% in the subcutaneous retatrutide 12 mg study arm at week 104. These are the study arms of the cited trials, not an application protocol for research vials. The extension result concerns that subset, rather than the full randomized population. [Eli Lilly, 21 May 2026; NCT05929066]
As of 13 September 2026, no peer-reviewed publication reports the TRIUMPH-1 week-80 or week-104 outcomes. The dated PubMed search for retatrutide or LY3437943 with TRIUMPH or TRIUMPH-1 returned 6 records, checked as designs, reviews, or correspondence. The registry has no posted results either; its endpoint fields document the study design. [PubMed search, 13 September 2026; NCT05929066]
What durations do registry records plan?
The longest registry window is approximately 248 weeks in the event-driven cardiovascular and kidney outcomes trial, and it remains a plan without results. This is a planned study-completion window, not a completed exposure result. [NCT06383390]
Other records also contain plans without posted results: TRIUMPH-2 and TRIUMPH-3 specify body-weight endpoints at week 80. The maintenance study specifies an 80-week lead-in followed by a 36-week randomized comparison, with its primary endpoint at week 116. Those durations describe different designs and cannot be combined into an observed treatment history. [NCT05929079; NCT05882045; NCT06859268]
The liver outcomes trial plans about 224 weeks. A separate dose escalation study lists a week-104 endpoint and about 113 weeks of overall participation. Endpoint timing and total participation are distinct fields; neither supplies a completed long-term result here. These are registry plans without results. [NCT07165028; NCT07357415]
The ClinicalTrials.gov check on 13 September 2026 found posted results in only two of 34 retatrutide studies. The longest treatment period among those posted results was 48 weeks. A registry entry can therefore extend the map of planned research without extending the observed evidence. [ClinicalTrials.gov search; NCT04867785; NCT04881760]
What do the off-treatment comparisons show?
The registered retatrutide maintenance study plans a continued-treatment versus placebo-switch comparison after its 80-week lead-in, but it has no results to report. Its subsequent 36-week randomized period asks a different question from an extension in which treatment continues. [NCT06859268]
The semaglutide STEP 1 extension and tirzepatide SURMOUNT-4 supply class comparison context on withdrawal; their findings belong to those medicines and study designs. Class regain data are covered in Weight regain after stopping GLP-1. [PMID 35441470; PMID 38078870]
Marshall's observational study separately reports one-year persistence on marketed GLP-1 products among insured members without diabetes. Persistence describes treatment continuation in that population, not retatrutide trial exposure, and the paper does not establish reasons for discontinuation. [PMID 41760566]
PeptidesDirect does not sell tirzepatide. PeptidesDirect does not sell semaglutide.
Does any label state a duration?
No approved label states a retatrutide duration because retatrutide has no marketing authorization in the EU or the US. The checks dated 13 September 2026 found no approved application in Drugs@FDA and no retatrutide entry in the EMA medicines table. [openFDA; EMA medicines output table, 13 September 2026]
The FDA directory records identified in that check were categorized as “BULK INGREDIENT”. Such directory records do not supply an approved treatment duration. The durations above remain publication findings, company-reported observations, or registry plans, each bounded by its source. [openFDA, 13 September 2026]
Products mentioned
Retatrutide (LY3437943) is a synthetic 39-amino-acid peptide that acts on three receptors at once: GLP-1, GIP and glucagon. Supplied as a lyophilized powder for in-vitro research, with a batch-specific third-party certificate of analysis.
Sources
- Jastreboff AM, 2023. Phase 2 obesity trial. N Engl J Med 389(6):514-526. PMID 37366315; NCT04881760.
- Bajaj HS, 2026. TRANSCEND-T2D-1. Lancet 407(10546):2402-2413. PMID 42250575; NCT06354660.
- Wilding JPH, 2022. STEP 1 extension. Diabetes Obes Metab 24(8):1553-1564. PMID 35441470; NCT03548935.
- Aronne LJ, 2024. SURMOUNT-4. JAMA 331(1):38-48. PMID 38078870; NCT04660643.
- Marshall LZ, 2026. Real-world one-year persistence. J Manag Care Spec Pharm 32(3):281-291. PMID 41760566.
- ClinicalTrials.gov, checked 13 September 2026. Retatrutide study records: NCT04881760, NCT04867785, NCT06354660, NCT05929066, NCT05929079, NCT05882045, NCT06859268, NCT06383390, NCT07165028, NCT07357415.
- Eli Lilly and Company, 21 May 2026. TRIUMPH-1 topline release. Company release, not peer reviewed.
- openFDA, 13 September 2026. Drugs@FDA API and NDC directory API.
- EMA, 13 September 2026. Medicines output table.
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