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Retatrutide: evidence brief

Selected primary studies, with the material tested, findings and limitations kept together. Follow each source to understand what it establishes.

Retatrutide: evidence brief

Trace the finding back to the study

Choose a source to connect the material tested, the population or model, and the reported outcome. Keep the study limits attached to the finding.

Brief version: 2026-10-05.1

Selected study: Jastreboff et al., 2026 · TRIUMPH-1 · PMID 42814954

Material tested
Study-supplied subcutaneous retatrutide (LY3437943), target arms 4/9/12 mg versus placebo.
Population or model
Adults without diabetes: BMI ≥30, or ≥27 with a weight-related complication.
Reported finding
Week-80 weight change, treatment-regimen/ITT estimate: −17.6/−23.7/−25.0% for 4/9/12 mg versus −3.9% placebo. Primary 9/12-mg differences: −19.8/−21.0 percentage points (both p<0.001).
Study design
TRIUMPH-1: phase 3, randomized, double-blind; 80 weeks. Primary weight comparisons: 9/12 mg versus placebo; additional subgroup pain and sleep-apnea endpoints.
Sample and comparison
Paper reports 2,339 randomized; official registry lists 2,335 enrolled. Difference unresolved; arm-level analysis counts not verified in the retrieved abstract.
Limits of this evidence
Pain and sleep-apnea primary results concern subgroups and different estimands, not the full weight population. Gastrointestinal events were most common; detailed methods and longer-term safety are not established by this abstract.

Source access: Primary journal and PubMed abstracts plus official registry inspected; full text and supplement could not be retrieved. Enrollment discrepancy remains unresolved.

Read primary source: Jastreboff et al., 2026 · TRIUMPH-1 · PMID 42814954 ↗Read the full study record: Jastreboff et al., 2026 · TRIUMPH-1 · PMID 42814954 ↓

A map of selected study conditions, not a molecular structure or a ranking of treatments. Different preparations, populations and endpoints are not interchangeable.

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What was actually studied

The phase 3 reports measured weight change with and without type 2 diabetes, or HbA1c change on diet and exercise alone. The liver report reused a subset of an earlier obesity trial. Different populations, endpoints and estimands prevent a ranking across these trials; imaging liver-fat reduction does not establish clinical liver outcomes.

Version
2026-10-05.1
Snapshot updated

Prepared by Peptides Codex. Independent review by a qualified subject specialist is pending.

Scope of this brief

Four selected primary reports identified through October 5, 2026, on study-supplied subcutaneous retatrutide (LY3437943), funded by Eli Lilly. Arm doses describe study conditions, not instructions or authentication of research powders. This is not an exhaustive review; qualified scientific review remains pending.

  1. Jastreboff et al., 2026 · TRIUMPH-1 · PMID 42814954

    Material tested
    Study-supplied subcutaneous retatrutide (LY3437943), target arms 4/9/12 mg versus placebo.
    Model or population
    Adults without diabetes: BMI ≥30, or ≥27 with a weight-related complication.
    Study design
    TRIUMPH-1: phase 3, randomized, double-blind; 80 weeks. Primary weight comparisons: 9/12 mg versus placebo; additional subgroup pain and sleep-apnea endpoints.
    Sample and comparison
    Paper reports 2,339 randomized; official registry lists 2,335 enrolled. Difference unresolved; arm-level analysis counts not verified in the retrieved abstract.
    Reported finding
    Week-80 weight change, treatment-regimen/ITT estimate: −17.6/−23.7/−25.0% for 4/9/12 mg versus −3.9% placebo. Primary 9/12-mg differences: −19.8/−21.0 percentage points (both p<0.001).
    Limits of this evidence
    Pain and sleep-apnea primary results concern subgroups and different estimands, not the full weight population. Gastrointestinal events were most common; detailed methods and longer-term safety are not established by this abstract.

    Source access: Primary journal and PubMed abstracts plus official registry inspected; full text and supplement could not be retrieved. Enrollment discrepancy remains unresolved.

    Primary source ↗: Jastreboff et al., 2026 · TRIUMPH-1 · PMID 42814954

  2. Bellido et al., 2026 · TRIUMPH-2 · PMID 42810372

    Material tested
    Study-supplied subcutaneous retatrutide (LY3437943), target arms 4/9/12 mg versus placebo.
    Model or population
    Adults with BMI ≥27 and type 2 diabetes, HbA1c 6.5–10.5%, on stable diet/exercise alone or up to three oral glucose-lowering medicines.
    Study design
    TRIUMPH-2: phase 3, randomized 1:1:1:1, double-blind, placebo-controlled; 80 weeks. Primary weight comparisons: 9/12 mg; 4 mg was a key secondary comparison.
    Sample and comparison
    1,152 randomized/analyzed: 292/284/287 versus 289; 965 completed study drug. Safety counts: 292/284/286 versus 287 who received drug. Primary missing values multiply imputed.
    Reported finding
    Primary week-80 weight change, treatment-regimen estimate: −16.8/−18.8% for 9/12 mg versus −5.1% placebo. Differences: −11.8/−13.8 percentage points (95% CI −13.7 to −9.8/−15.8 to −11.8; both p<0.0001).
    Limits of this evidence
    Placebo comparison in a selected diabetes population. Gastrointestinal events were more frequent with retatrutide; permanent discontinuation due to adverse events or death was 12/8% at 9/12 mg versus 5% placebo. No active-drug ranking or long-term safety conclusion.

    Source access: Primary PubMed abstract and official registry inspected; publisher full text could not be retrieved. Analysis populations and imputation are stated in the abstract; detailed methods were not read.

    Primary source ↗: Bellido et al., 2026 · TRIUMPH-2 · PMID 42810372

  3. Bajaj et al., 2026 · TRANSCEND-T2D-1 · PMID 42250575

    Material tested
    Study-supplied subcutaneous retatrutide (LY3437943), target arms 4/9/12 mg versus placebo.
    Model or population
    Adults with type 2 diabetes inadequately controlled by diet/exercise alone, HbA1c 7.0–9.5% and BMI ≥23.
    Study design
    TRANSCEND-T2D-1: phase 3, randomized 1:1:1:1, double-blind, placebo-controlled; 40 weeks. Primary endpoint: HbA1c change.
    Sample and comparison
    537 randomized: 134/133/136 versus 134 placebo. 490 completed the treatment period on drug; 504 completed the study. Abstract does not detail analysis-set exclusions.
    Reported finding
    Primary week-40 HbA1c change, treatment-regimen estimate: −1.69/−1.86/−1.94 percentage points for 4/9/12 mg versus −0.81 placebo. Adjusted differences: −0.88/−1.04/−1.12 points (all p<0.0001); not relative percent changes.
    Limits of this evidence
    Monotherapy population and 40-week glycemic endpoint; not a cardiovascular-outcomes trial. Gastrointestinal events were common; adverse-event discontinuations were 2–5% versus 0% placebo. Full estimand implementation and long-term safety remain unverified here.

    Source access: Primary PubMed abstract and official registry inspected; publisher full text could not be retrieved. Detailed missing-data methods and analysis-set counts were not available in the abstract.

    Primary source ↗: Bajaj et al., 2026 · TRANSCEND-T2D-1 · PMID 42250575

  4. Sanyal et al., 2024 · MASLD substudy · PMID 38858523

    Material tested
    Study-supplied subcutaneous retatrutide (LY3437943), 1/4/8/12 mg versus matching placebo, with lifestyle counseling. Starting-dose subgroups pooled at 4/8 mg.
    Model or population
    Adults without diabetes in an obesity trial, with baseline MRI liver fat ≥10%; selected MASLD substudy.
    Study design
    Phase 2a substudy of randomized, double-blind NCT04881760; 48-week treatment, primary liver-fat endpoint at 24 weeks. Efficacy estimand excludes post-discontinuation data; continuous-outcome mixed model without imputation.
    Sample and comparison
    98 of the parent trial's 338 participants: 20/19/22/18 versus 19 placebo. Week-24 MRIs available for 77: 16/15/17/15 versus 14. Shared cohort, not independent replication.
    Reported finding
    Primary relative MRI-PDFF liver-fat change at week 24: −42.9/−57.0/−81.4/−82.4% for 1/4/8/12 mg versus +0.3% placebo (all p<0.001). These are relative reductions, not absolute liver-fat percentage-point changes.
    Limits of this evidence
    Small selected subset, missing imaging and exclusion of data after intercurrent events; no multiplicity adjustment. Imaging fat reduction does not demonstrate biopsy-confirmed MASH resolution, fibrosis regression or clinical liver benefit. Sponsor participated in design, analysis and report writing.

    Source access: Primary Nature Medicine full text inspected, including Methods, Results, figure counts and limitations; parent registry corroborated. Supplementary files and individual participant data not reviewed.

    Primary source ↗: Sanyal et al., 2024 · MASLD substudy · PMID 38858523

A finding applies to the material, model and conditions studied. It does not establish safety or effectiveness in other settings.

Help review this exact version

Qualified scientific review is pending. Source-backed corrections are welcome; a correction submission does not itself constitute expert approval.

Review reference: retatrutide · 2026-10-05.1

What a reviewer should check
  1. Does the reported material match the preparation actually studied?
  2. Do population, participant counts and analysis denominators match the source?
  3. Are estimates, endpoints, uncertainty and missing-data methods represented accurately?
  4. Do limitations, source-access boundaries and English/French text preserve the same conclusion?

Study records in this version

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