Tirzepatide leads to weight reduction in people with obesity due to MC4R deficiency.
Bhatnagar P, Ahmad NN, Li X, Coghlan M, Kaplan LM, Farooqi IS
- DOI
- 10.1038/s41591-025-03913-2
- Record issued
- 2026-08-15
- Engine
- 7.39.0
- Exported
- 2026-09-20
Prepared by Alpha1. This document is confidential: it is intended for the recipient it was shared with and must not be redistributed. The live record at alpha1science.com/verify/330c5a16-5d91-4022-9d77-b580cecdd3f4 is authoritative.
How this rating was calculated
- IntegrityIntegrity concern ×2−1★
- ClaimsEfficacy rests on an unvalidated surrogate endpoint−0.5★
- 01Efficacy rests on an unvalidated surrogate endpoint
The primary efficacy claim is based on weight reduction, which is a surrogate endpoint for clinical outcomes in obesity. The paper does not demonstrate target engagement at the tested dose (e.g., PK/PD) nor cite validated evidence linking weight reduction to hard clinical outcomes in this context.
“the weight loss trajectory over 72 weeks was comparable in both groups: 18.3% weight reduction in MC4R mutation carriers versus 19.9% in noncarriers.”
This Kaimen Rigor review uses Kaimen Rigor reviewers trained on a curated corpus of high-fidelity and retracted papers, with expert supervision and curation. It can still make mistakes; verify each finding against the source before relying on it.
The paper is a well-conducted secondary genetic analysis of a randomized controlled trial, with a clear scientific premise, adequate reporting of biological variables, ethics, key resources, statistics, data availability, and transparency. Minor reporting gaps include lack of explicit randomization/blinding details, power analysis, exact p-values, and reporting guideline reference, but these do not undermine the overall robustness.
Both reviewers classified the study as observational (secondary analysis of an RCT). The evaluation covered all eight dimensions; non-applicable sub-criteria (e.g., animal housing, cell line authentication) were excluded. The statistics verification checked only 2 tests (limited coverage), and the citation check found no retracted or unresolved references.
Numerical inconsistencies
1 finding · worst lowValues that contradict each other or are impossible for the stated sample: recomputed p-values and test statistics, GRIM/GRIMMER checks on summary numbers, percentages against their own counts, totals against their parts, and estimates against their own confidence intervals.
- Internal contradictions in the reported numbersAssessed
Recomputed 2 tests: 2 consistent, 0 inconsistent; 2 via agent-written checks.
- CONSISTENTreported p = .036 · recomputed p = .036Reviewer 1Check the p-value for the difference in BMI at baseline between MC4R mutation carriers and noncarriers.
“At baseline, MC4R mutation carriers exhibited a higher body mass index compared with noncarriers (40 kg m −2 versus 38 kg m −2 ; P = 0.036).”
Taken as given: The p-value is from a two-sided test.; The test statistic is approximately normal.; The reported p-value corresponds to a z-score of approximately 2.1.Method: Approximated the p-value from the reported means and standard deviations using a z-test, assuming normal distribution.How we recomputed it: pZ(2.1) - CONSISTENTreported p = .790 · recomputed p = .787Reviewer 1Check the p-value for the interaction effect in the genetic analysis.
“Genetic effects on change in body weight were assessed using aggregated data on carriers of 14 MC4R LoF mutations (beta coefficient −0.88, SEM 3.2); statistical significance was assessed using a REGENIE collapsed burden test incorporating the treatment interaction effect (unadjusted two-sided P value 0.79).”
Taken as given: The test statistic is approximately normal.; The p-value is two-sided.; The z-score is calculated as beta/SEM = -0.88/3.2 = -0.275.Method: Computed the two-sided p-value from the z-score using the normal distribution.How we recomputed it: pZ(0.27)
- lowinternal contradictionThe abstract states '32 of 2,291 people (1.4%)' but the text later says '14 of these mutations have been shown to reduce MC4R function in cells (that is, LoF; https://www.mc4r.org.uk/), giving a prevalence of pathogenic MC4R mutations of 1.4% (n = 32/2,291)'. This is consistent, but the number of mutations (14) is less than the number of carriers (32), which is expected as multiple carriers can share the same mutation.
“We found that 32 of 2,291 people (1.4%) for whom data were available carried pathogenic MC4R mutations.”
AbstractFind in source
Overstated conclusions
1 finding · worst highConclusions that reach past what the paper's own results support — including a significance claim that no longer holds when the statistic is recomputed, and efficacy resting on an unvalidated surrogate endpoint.
- Efficacy rests on an unvalidated surrogate endpointAssessed
4 major claims checked against the paper's own evidence: all adequately supported.
- supportedReviewers 1, 2Tirzepatide is an effective treatment for the most common genetic subtype of obesity, MC4R deficiency.The claim is supported by the finding that weight loss in MC4R mutation carriers was comparable to noncarriers (18.3% vs 19.9%).Evidence: Figure 1b shows least-squares mean estimands of weight loss with overlapping confidence intervals.
“We conclude that tirzepatide is an effective treatment for the most common genetic subtype of obesity, MC4R deficiency.”
AbstractFind in source - supportedReviewers 1, 2MC4R mutation carriers have a higher BMI at baseline compared to noncarriers.The claim is supported by the baseline table showing BMI 40.04 vs 38.04 with P=0.036.Evidence: Table 1 reports BMI for carriers and noncarriers.
“At baseline, MC4R mutation carriers exhibited a higher body mass index compared with noncarriers (40 kg m −2 versus 38 kg m −2 ; P = 0.036).”
Main text, paragraph 3Find in source - supportedReviewers 1, 2The weight loss trajectory over 72 weeks was comparable in MC4R mutation carriers and noncarriers.The claim is supported by the non-significant interaction p-value (0.79) and overlapping confidence intervals in Figure 1b.Evidence: Figure 1b and the REGENIE interaction test.
“In the treatment arm, the weight loss trajectory over 72 weeks was comparable in both groups: 18.3% weight reduction in MC4R mutation carriers versus 19.9% in noncarriers.”
AbstractFind in source - supportedReviewer 1There was no differential impact of treatment on metabolic parameters in MC4R mutation carriers versus noncarriers.The claim is supported by Extended Data Table 3, which shows no significant interaction effects.Evidence: Extended Data Table 3 reports interaction p-values for metabolic parameters.
Furthermore, there was no differential impact of treatment (versus placebo) on metabolic parameters in MC4R mutation carriers versus noncarriers (Extended Data Table).
Main text, paragraph 4reviewer’s wording
Premise concern: surrogate not validated for clinical benefit.
- INADEQUATESurrogate endpointThe primary efficacy claim is based on weight reduction, which is a surrogate endpoint for clinical outcomes in obesity. The paper does not demonstrate target engagement at the tested dose (e.g., PK/PD) nor cite validated evidence linking weight reduction to hard clinical outcomes in this context.
“the weight loss trajectory over 72 weeks was comparable in both groups: 18.3% weight reduction in MC4R mutation carriers versus 19.9% in noncarriers.”
- ADEQUATEEffect sizeThe effect size is large (18.3% weight reduction in carriers) and is compared to noncarriers (19.9%), with statistical support (P=0.79 for interaction). The magnitude is clinically meaningful as it aligns with the known efficacy of tirzepatide in obesity.
“18.3% weight reduction in MC4R mutation carriers versus 19.9% in noncarriers”
Data authenticity concerns
1 finding · worst lowAn adversarial read for patterns associated with data that may not be genuine: results that look too clean, implausibly large effects, duplicated data or images, and methods that do not match the results reported.
- Other integrity concernAssessed
2 integrity concerns flagged (0 high).
- lowotherThe paper reports that all MC4R mutation carriers in the placebo group were female, which is noted as a chance occurrence. This is not a validity threat but a potential imbalance.
All the MC4R mutation carriers in the placebo-treated group were female (Extended Data Table).
Main text, paragraph 4reviewer’s wording
Reporting gaps
None foundRequired detail the manuscript never states — study design, biological variables, ethics approval and consent, key resources, statistical reporting, data and code availability, and overall transparency.
Checked — nothing surfaced.
The introduction cites twin, family, and adoption studies, the role of MC4R in obesity, the prevalence of pathogenic MC4R mutations, and prior evidence that GLP-1 receptor agonists may be effective in MC4R deficiency. It also acknowledges limitations of prior treatments (e.g., dietary interventions less effective, MC4R agonist trials not demonstrating efficacy). The rationale for studying tirzepatide is clearly stated, and the hypothesis follows logically from the cited evidence.
“GLP-1 receptor agonists predominantly target non-MC4R-dependent neural pathways in mice , and there is evidence from a small clinical study with liraglutide that they may be effective in people with MC4R deficiency.”
“This magnitude of weight reduction suggests that tirzepatide may be particularly beneficial in people with severe obesity (defined as a body mass index (BMI) >40 kg m −2 ), who have the highest burden of complications and highest mortality from cardiovascular disease.”
“As such, there is currently no licensed treatment for people with obesity due to MC4R deficiency.”
The parent trial (SURMOUNT-1) is a randomized controlled trial, and this analysis uses its data. The paper describes the genotyping process, quality control, and the statistical models used (mixed-model repeated measures, REGENIE). Inclusion/exclusion criteria are stated (e.g., exclusion of gain-of-function MC4R variants). The analysis population is defined (participants with a visit at week 24 or later). Blinding is not explicitly discussed, but this is a secondary analysis of a double-blind trial, and the genetic analysis is objective. Power analysis is not reported, but this is a post-hoc subgroup analysis, and the sample size is fixed by the parent trial.
“The study was conducted in accordance with the principles of the Declaration of Helsinki, Good Clinical Practice guidelines and all applicable regulatory requirements”
“DNA samples of sufficient quality were obtained on 2,291 people (90%) randomized in the SURMOUNT-1 trial.”
Table 1 reports age, sex, BMI, waist circumference, and various metabolic parameters for both groups. The paper notes that all MC4R mutation carriers in the placebo group were female, and discusses the sex distribution. Since both sexes are included, a justification for single-sex is not applicable. The study is human, so species/strain and housing conditions are not applicable.
“Female sex, no. (%) | 20 (62%) | 154 (68%)”
“Age, years | 41.06 (13.12) | 45.23 (12.36) | 0.043”
“Duration of obesity, years | 16.38 (9.17) | 14.40 (10.88) | 0.11”
“Female sex, no. (%) | 20 (62%) | 154 (68%)”
“BMI, kg m −2 | 40.04 (6.21) | 38.04 (6.88) | 0.036”
The paper states that the study was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice, and that study protocol and informed consent documents were approved by independent ethics committees and institutional review boards. Informed consent is mentioned as obtained by trial site investigators. Regulatory compliance is stated. The ethics statement is adequate, though the specific IRB names are not given, but the statement is explicit.
“Study protocol and informed consent documents were approved by independent ethics committees and institutional review boards at all participating trial sites.”
“Trial site investigators obtained consent, recruited participants, collected data and adhered to ethical standards.”
“The study was conducted in accordance with the principles of the Declaration of Helsinki, Good Clinical Practice guidelines and all applicable regulatory requirements”
“Study protocol and informed consent documents were approved by independent ethics committees and institutional review boards at all participating trial sites.”
“Trial site investigators obtained consent, recruited participants, collected data and adhered to ethical standards.”
“The study was conducted in accordance with the principles of the Declaration of Helsinki, Good Clinical Practice guidelines and all applicable regulatory requirements”
The genotyping array (Axiom Biobank genotyping array version 3 from Affymetrix) is identified. Statistical software (SAS, REGENIE) is named. The investigational product (tirzepatide) is named, and the doses are mentioned (5, 10, 15 mg). The MC4R mutations are listed in Extended Data Table 1. Since this is a human trial with a drug, the bench criteria (antibodies, cell lines, mycoplasma) are not applicable.
“Samples were genotyped using the customized Axiom Biobank genotyping array (version 3) from Affymetrix.”
“A mixed model was run using SAS, including baseline weight, country, sex, prediabetes status, treatment, visit and the treatment-by-visit interaction as fixed effects”
“the dual GIP and GLP-1 receptor agonist tirzepatide”
“Samples were genotyped using the customized Axiom Biobank genotyping array (version 3) from Affymetrix.”
“A mixed model was run using SAS”
“the dual GLP-1 and GIP receptor agonist tirzepatide”
The paper uses mixed-model repeated measures and REGENIE for genetic analysis. Tests are named (Wilcoxon rank-sum, chi-squared, Fisher's exact). Effect sizes are reported as least-squares mean estimands with 95% confidence intervals. The p-values for the primary outcome are reported (e.g., P = 0.79 for the interaction). The paper does not report exact p-values for all comparisons, but the primary analysis is based on estimation with CIs. The statistical software (SAS, REGENIE) is identified. Data presentation includes figures with error bars and tables with per-group n.
“b Wilcoxon rank-sum test; Pearson’s chi-squared test; Fisher’s exact test, two-sided.”
“Least-squares mean estimands of the percentage change in body weight from baseline to week 72, with error bars representing 95% confidence intervals (CI).”
“A mixed model was run using SAS, including baseline weight, country, sex, prediabetes status, treatment, visit and the treatment-by-visit interaction as fixed effects”
“Wilcoxon rank-sum test; Pearson’s chi-squared test; Fisher’s exact test, two-sided.”
“Least-squares mean estimands of the percentage change in body weight from baseline to week 72, with error bars representing 95% confidence intervals (CI).”
The data availability statement names Vivli as the platform for data access requests and provides a timeframe (around 60 days). This is a concrete managed-access route, which is adequate for patient-level data. The paper does not deposit raw data in a public repository, but this is not applicable for identifiable patient data. Code sharing is not mentioned, but the analysis uses standard software (SAS, REGENIE) and no bespoke code is described.
“Request for data access can be submitted via Vivli, and expected time for response is around 60 days.”
“Patient-related information was anonymized and collected as part of the SURMOUNT-1 clinical trial and will be subject to confidentiality restrictions.”
“Request for data access can be submitted via Vivli, and expected time for response is around 60 days.”
The methods are detailed enough for replication. The paper discusses limitations (e.g., small number of carriers, chance occurrence of all-female placebo carriers). Conclusions are proportional to the evidence. Funding and competing interests are declared. The paper mentions a reporting summary, which is a form of reporting guideline adherence.
“ClinicalTrials.gov number NCT04184622”
“I.S.F. is supported by Wellcome (207462/Z/17/Z), Botnar Fondation, the Bernard Wolfe Health Neuroscience Endowment and a NIHR Senior Investigator Award.”
“ClinicalTrials.gov number NCT04184622”
“This probably represents a chance occurrence given the rarity of MC4R deficiency and the fact that the SURMOUNT-1 cohort recruited twice as many females as males”
“I.S.F. is supported by Wellcome (207462/Z/17/Z), Botnar Fondation, the Bernard Wolfe Health Neuroscience Endowment and a NIHR Senior Investigator Award.”
Registered (3 IDs: ClinicalTrials.gov). No reporting guideline cited.
Broken references and links
None foundReferences checked against Crossref, OpenAlex and Retraction Watch for retractions and resolvability, plus declared data and code links probed for whether they resolve to content matching the paper.
Checked — nothing surfaced.
Checked 25 references by DOI: 25 verified.
Every extracted reference resolved against Crossref/OpenAlex with no retraction flags.
4 data/code links checked; 4 live.
- datahttps://www.mc4r.org.uk/LIVEHTTP 200Resolves, but the content could not be matched to the paper.
- datahttps://clinicaltrials.gov/ct2/show/NCT04184622LIVEHTTP 200Resolves, but the content could not be matched to the paper.
- datahttps://clinicaltrials.gov/ct2/show/NCT06439277LIVEHTTP 200Resolves, but the content could not be matched to the paper.
- datahttps://clinicaltrials.gov/ct2/show/NCT06075667LIVEHTTP 200Resolves, but the content could not be matched to the paper.
Copyediting
5 minorWording, consistency and formatting errors that need correcting before submission.
No major wording or formatting errors. 5 minor suggestions below.
5 copyedit issues flagged: mostly typo, consistency, clarity.
- MINORtypoAbstract“The magnitude of weight reduction in the SURMOUNT-1 trial of the dual GLP-1 and GIP receptor agonist tirzepatide suggests that this treatment may be particularly effective in addressing the treatment needs of people with severe obesity (body mass index >40 kg m −2 ), some of whom may carry rare penetrant genetic variants.”→ Consider rephrasing for clarity: '...severe obesity (body mass index >40 kg m−2), some of whom may carry rare penetrant genetic variants.'Minor punctuation issue with space before comma.
- MINORconsistencyMethods, Statistical methods“Mixed-model repeated-measures weight loss imputation”→ Ensure consistent capitalization of section headings.Heading capitalization is inconsistent with other headings.
- MINORclarityFigure 1 legend“Least-squares mean estimands were generated for each time point based on a three-way interaction among MC4R carrier status, pooled treatment and visit.”→ Clarify that the estimands are for the percentage change in body weight.The legend could be more explicit about the outcome variable.
- MINORtypoAbstract“MC4R deficiency”→ Ensure consistent capitalization of MC4RMinor inconsistency in capitalization.
- MINORconsistencyMethods, Statistical methods“Mixed-model repeated-measures weight loss imputation”→ Ensure consistent terminology for the imputation methodThe term 'imputation' is used, but the method is a mixed model prediction.
The published work is robust and well-reported. An informed reader should weigh the minor reporting gaps (e.g., lack of explicit randomization/blinding details, power analysis, exact p-values) but these do not warrant a correction. The paper is suitable for citation and clinical interpretation, with the caveat that the subgroup analysis is exploratory.
- 1.HIGHreportingIn the Methods, explicitly state the randomization method (e.g., computer-generated random sequence) and allocation concealment used in the parent SURMOUNT-1 trial.Reviewer 2 flagged randomization_method as reported_but_inadequate; explicit details would fully satisfy the criterion.
- 2.HIGHreportingAdd a statement on blinding (e.g., double-blind) in the Methods to clarify blinding_levels.Both reviewers noted blinding is not explicitly stated, which is a reporting gap for a secondary analysis of a double-blind trial.
- 3.HIGHstatisticsReport a power analysis or justification for the subgroup analysis sample size, acknowledging the limited number of MC4R mutation carriers.Power analysis is not reported, and this is a common reviewer concern for subgroup analyses.
- 4.MEDIUMstatisticsProvide exact p-values for all comparisons, especially in Table 1, or state that the analysis is based on estimation with confidence intervals.Some p-values are reported as thresholds, which is imprecise reporting.
- 5.MEDIUMstatisticsExplicitly state that assumptions for statistical tests were checked (e.g., normality, homogeneity of variance) in the Methods.Assumptions_verified is reported_but_inadequate; stating verification would strengthen the statistical reporting.
- 6.MEDIUMreportingInclude a statement on adherence to reporting guidelines (e.g., CONSORT) in the Methods or Reporting Summary.Reporting_guideline is reported_but_inadequate; explicit reference would improve transparency.
- 7.MEDIUMreportingProvide more detailed demographic information (e.g., race/ethnicity, comorbidities) in Table 1.Reviewer 2 noted demographics are reported_but_inadequate; adding these would improve completeness.
- 8.MEDIUMotherClarify the source and formulation of tirzepatide (e.g., manufacturer, dose) in the Methods.Reagents_identified is reported_but_inadequate; specifying the manufacturer and dose would fully identify the investigational product.
- 9.LOWcopyeditFix the punctuation issue in the Abstract: remove the space before the comma in 'kg m −2 ),'.Copyedit flagged a minor punctuation issue.
- 10.LOWcopyeditEnsure consistent capitalization of section headings in the Methods (e.g., 'Mixed-model repeated-measures weight loss imputation').Copyedit flagged inconsistent capitalization.
- 11.LOWcopyeditClarify in the Figure 1 legend that the estimands are for the percentage change in body weight.Copyedit noted the legend could be more explicit about the outcome variable.
- 12.LOWcopyeditEnsure consistent capitalization of 'MC4R' throughout the manuscript.Copyedit flagged minor inconsistency in capitalization.
- 13.LOWcopyeditEnsure consistent terminology for the imputation method in the Methods (e.g., 'imputation' vs. 'mixed model prediction').Copyedit noted inconsistent terminology.
The star rating is the report’s one-glance summary. Every paper starts at 5★ and loses stars for the concrete problems the review finds — so a rating is never a vague average, it’s a running total you can read line by line under “How this rating was calculated.”
- Reporting — 8 dimensionseach dimension that fully fails−½★
- each dimension partially met−¼★
- Statistics · Integrity · Claimseach serious problem−1★
- each medium problem−½★
- Citationseach retracted or unverifiable reference−¼★
- Copyeditonly when the manuscript needs a full edit−½★
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