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- Phase 2 weight-loss trial (NEJM): primary and secondary endpoint weeks
- Body-composition substudy (DXA): measurement week
- Patient-reported appetite and eating-behaviour assessments: timing
- Phase 3 TRIUMPH program: what the protocol summary reports about timing
- Synthesis: commonly reported assessment windows across reviewed trials
- Reported study-design details from cited sources
- Limitations and research gaps
- Documentation checklist
- Related research supplies
- More Retatrutide research
- Sources and references
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This article summarizes published research and reported study designs. It is not medical advice, dosing guidance, or a personal-use recommendation.
This deep dive summarizes the specific assessment timepoints reported in reviewed clinical-trial records and journal publications for retatrutide (LY3437943), focusing on when key efficacy, physiologic, and patient-reported outcomes were measured.
Phase 2 weight-loss trial (NEJM): primary and secondary endpoint weeks
The Phase 2 randomized, double-blind, placebo-controlled trial published in NEJM prespecified the percentage change in body weight from baseline to Week 24 as the primary endpoint; percentage change in body weight from baseline to Week 48 was a key secondary endpoint. The trial administered once-weekly subcutaneous dosing for 48 weeks and reported that dose‑dependent increases in heart rate peaked at Week 24 and declined thereafter. [S1]
Body-composition substudy (DXA): measurement week
The Phase 2 body-composition substudy used DXA to assess percent change in total body fat mass from baseline to Week 36 as the prespecified primary substudy endpoint; efficacy analyses used on‑treatment data before drug discontinuation and compared results at baseline versus Week 36. [S4]
Patient-reported appetite and eating-behaviour assessments: timing
Pre-specified exploratory analyses of appetite and eating-behaviour questionnaires in adults with type 2 diabetes reported changes from baseline at Week 24 and at Week 36 during once-weekly retatrutide treatment; correlations between questionnaire changes and weight change were reported at Week 36. [S6]
Phase 3 TRIUMPH program: what the protocol summary reports about timing
The TRIUMPH Phase 3 program comprises four randomized, double-blind studies assessing once-weekly subcutaneous retatrutide across weight management and adiposity-related comorbidity baskets; the program description specifies primary endpoints (percent change in body weight for weight management, Apnea–Hypopnea Index for OSA, WOMAC pain subscore for knee OA) but the reviewed excerpt does not report the planned assessment weeks for these primary endpoints. [S3]
Synthesis: commonly reported assessment windows across reviewed trials
Across the reviewed Phase 2 publications, key efficacy and patient-reported outcomes were recurrently measured in the mid-range (Week 24) and later-range (Week 36 or Week 48) time windows: the NEJM Phase 2 trial used Week 24 (primary) and Week 48 (secondary) weight assessments, the Lancet Diabetes & Endocrinology substudy used Week 36 DXA for body-composition change, and the appetite/eating-behaviour analyses reported Weeks 24 and 36 measurements. [S1] [S4] [S6]
Reported study-design details from cited sources
The following table summarizes protocol details reported in cited studies. These details are provided as literature context only and are not recommendations or instructions.
| Source | Study Type | Model / Subject | Amount Reported | Route Reported | Frequency | Duration | Notes |
|---|---|---|---|---|---|---|---|
| [S1] | Phase 2 randomized, double-blind, placebo-controlled trial | Adults with obesity (BMI ≥30 or BMI 27– | Randomized to retatrutide 1 mg, 4 mg (initial 2 mg or 4 mg), 8 mg (initial 2 mg or 4 mg), 12 mg (initial 2 mg), or placebo | subcutaneous | once weekly | 48 weeks (treatment administered for 48 weeks) | Primary endpoint: percent change in body weight from baseline to Week 24; secondary endpoint: percent change in body weight to Week 48; heart-rate increases peaked at Week 24 and declined thereafter. |
| [S4] | Phase 2, double-blind, parallel-group, placebo-controlled, randomized trial (body-composition substudy) | Adults with type 2 diabetes (age 18–75 years; BMI 25–50 kg/m2) | Randomized to once-weekly placebo, dulaglutide 1.5 mg, or retatrutide 0.5 mg, 4 mg (2 mg initial dose), 4 mg (4 mg initial dose), 8 mg (2 mg initial dose), 8 mg (4 mg initial dose), or 12 mg | subcutaneous | once weekly | 36 weeks (primary substudy endpoint measured at Week 36) | Primary substudy endpoint: percent change from baseline to Week 36 in total fat mass measured by DXA; analyses used on-treatment data before drug discontinuation from participants with non-missing DXA scans. |
| [S6] | Phase 2 randomized, double-blind, clinical trial (pre-specified exploratory analyses) | Adults with type 2 diabetes (participants in exploratory appetite/eating-behaviour analyses) | Randomized to placebo, dulaglutide 1.5 mg, or retatrutide 0.5, 4, 8, or 12 mg | subcutaneous | once weekly | 36 weeks (questionnaire assessments at Weeks 24 and 36) | Appetite Visual Analogue Scale and Eating Inventory scores were compared versus placebo and dulaglutide at Weeks 24 and 36; correlations with weight change were reported at Week 36. |
| [S3] | Phase 3 program (TRIUMPH: four multicenter randomized, double-blind studies) | Adults with obesity and subpopulations (OSA, knee osteoarthritis, or CVD cohorts) planned for registrational studies | not reported in the reviewed source | subcutaneous | once weekly | not reported in the reviewed source | TRIUMPH will test percent change in body weight (weight management), Apnea–Hypopnea Index (OSA), and WOMAC pain subscore (knee OA) in a nested/basket design across >5800 participants; the reviewed excerpt does not specify planned assessment weeks for the primary endpoints. |
Limitations and research gaps
- Timing details for primary or secondary endpoint visits in the Phase 3 TRIUMPH program are not reported in the reviewed TRIUMPH summary excerpt.
- Some published summaries report outcome magnitudes at specific weeks (24, 36, 48) but do not provide a complete schedule of all assessment visits or interim timepoints in the reviewed excerpts.
- The reviewed sources do not provide raw visit-level data or all scheduled measurement timepoints beyond those explicitly reported (e.g., Week 24, Week 36, Week 48).
Documentation checklist
- Identify which trial(s) you are examining and match endpoints to their reported measurement weeks.
- Differentiate primary vs secondary endpoints and note their prespecified assessment timepoints.
- For body-composition outcomes, confirm the imaging modality and the specific visit/week used for analysis (e.g., DXA at week 36).
- For patient-reported outcomes (appetite, eating-behaviour scales), record the exact weeks when questionnaires were administered (e.g., Weeks 24 and 36).
- When reviewing ongoing Phase 3 programs, note if scheduling/timing of primary assessments is not reported in the available protocol summary.
Related research supplies
- ClinicalTrials.gov record pages for the cited trials (trial identifiers reported in the sources)
- DXA imaging center documentation and machine calibration logs for body-composition assessments
- Questionnaire administration protocols (e.g., Appetite VAS and Eating Inventory) used to capture patient-reported outcomes
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Sources and references
- [S1] Jastreboff AM, Kaplan LM, Frías JP, Wu Q, Du Y, Gurbuz S. Triple-Hormone-Receptor Agonist Retatrutide for Obesity – A Phase 2 Trial.. The New England journal of medicine. 2023. PMID: 37366315. DOI: 10.1056/NEJMoa2301972
- [S2] Locatelli JC, Costa JG, Haynes A, Naylor LH, Fegan PG, Yeap BB. Incretin-Based Weight Loss Pharmacotherapy: Can Resistance Exercise Optimize Changes in Body Composition?. Diabetes care. 2024. PMID: 38687506. DOI: 10.2337/dci23-0100
- [S3] Giblin K, Kaplan LM, Somers VK, Le Roux CW, Hunter DJ, Wu Q. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials.. Diabetes, obesity & metabolism. 2026. PMID: 41090431. DOI: 10.1111/dom.70209
- [S4] Coskun T, Wu Q, Schloot NC, Haupt A, Milicevic Z, Khouli C. Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial.. The lancet. Diabetes & endocrinology. 2025. PMID: 40609566. DOI: 10.1016/S2213-8587(25)00092-0
- [S5] Katsi V, Koutsopoulos G, Fragoulis C, Dimitriadis K, Tsioufis K. Retatrutide-A Game Changer in Obesity Pharmacotherapy.. Biomolecules. 2025. PMID: 40563436. DOI: 10.3390/biom15060796
- [S6] Kanu C, Boye KS, Poon JL, Goetz I, Williamson S, Lou J. Appetite, eating attitudes, and eating behaviours during treatment with retatrutide in adults with type 2 diabetes: Results of a phase 2 study.. Diabetes, obesity & metabolism. 2025. PMID: 40916752. DOI: 10.1111/dom.70097
- [S7] Ma J, Hu X, Zhang W, Tao M, Wang M, Lu W. Comparison of the effects of Liraglutide, Tirzepatide, and Retatrutide on diabetic kidney disease in db/db mice.. Endocrine. 2025. PMID: 39212900. DOI: 10.1007/s12020-024-03998-8
- [S8] Drucker DJ. Efficacy and Safety of GLP-1 Medicines for Type 2 Diabetes and Obesity.. Diabetes care. 2024. PMID: 38843460. DOI: 10.2337/dci24-0003
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