The answer so far

The completed human study tested CB4211, a modified analogue of MOTS-c, not MOTS-c itself. Its sponsor reported preliminary changes in some liver and glucose markers, while liver fat fell in both groups. The short study does not establish the benefits or safety of a MOTS-c product.123

On this page
  1. What is an analogue?
  2. What did the study actually test?
  3. What did the early liver results show?
  4. Why do two sources give different numbers?
  5. What about reactions and safety?
  6. Why is the trial mentioned in US policy?
  7. What would answer the MOTS-c question?
  8. Sources
LINKED BUILDING BLOCKSAmino acids joined into a chainSequence and structure both matter
Conceptual schematic. Simplified and not to scale; not a scan, microscopy image or validated simulation.

What is an analogue?

An analogue is a related molecule deliberately changed from another. CB4211 was developed as an analogue of MOTS-c: related does not mean chemically identical or guaranteed to behave the same way in a person. A result for CB4211 can suggest a question to study, but it cannot establish the effects, quality or safety of a product labelled MOTS-c. Start with what MOTS-c is and why exercise research attracted interest.3

What did the study actually test?

The registered phase 1a/1b programme compared CB4211 with placebo in healthy adults and in adults with nonalcoholic fatty liver disease, a condition involving excess fat in the liver. Across its three parts, the registry records 88 participants and completion in April 2021. The sponsor’s presentation says 23 people entered the fatty-liver part and 20 completed the final assessment: 11 in the CB4211 group and nine in the placebo group. That is a small, short study of one investigational product, not 88 people completing the liver comparison.12

Follow the study, not just the nameA map of a preliminary trial; not a measurement of MOTS-c effects.
  • MOTS-cA mitochondrial-associated peptide discussed in exercise and metabolic research.
  • CB4211A modified analogue studied in the completed human programme.
  • 88 participantsThe registry records 88 across three parts, not 88 completing the liver comparison.
  • 20 final assessmentsThe sponsor reported 11 CB4211 and nine placebo participants in the final liver assessment.

What did the early liver results show?

The sponsor and conference abstract described changes in some blood markers, including liver enzymes and glucose, that favoured CB4211 in exploratory analyses. These were not the main safety outcomes and do not by themselves prove that liver disease improved or that complications were prevented. Liver fat measured by a scan fell in both groups during four weeks; participants stayed in a study unit and received a standardised diet. This makes the comparison important: improvement after treatment is not necessarily improvement caused by treatment. Explore tesamorelin’s separate liver-fat and biopsy study.23

Why do two sources give different numbers?

For one liver enzyme called AST, the 2021 company presentation reports an average change of −28% with CB4211 and −11% with placebo. The conference abstract reports −18% and −11% respectively. The reason for that difference is not clear from the sources checked. Both are preliminary reports, and the registry had no results posted when checked on 5 November 2026. A full clinical study report was not available among the sources reviewed; that limits independent interpretation. Neither value is a measure of fat loss or a finding about MOTS-c.231

What about reactions and safety?

The company reported that the earlier phase 1 portion was temporarily suspended in 2018 because of mild but unexpectedly persistent injection-site reactions. It later described changing the formulation and completing further cohorts. In 2021 it reported no serious adverse events in its topline account, while injection-site reactions were reported in 79% receiving CB4211 and 33% receiving placebo. “Serious” uses outcome-based criteria such as hospitalisation or a life-threatening event; it is different from how intense a reaction feels. A small early programme cannot rule out rare or delayed harms, and these findings describe the tested CB4211 formulations, not the safety profile of MOTS-c. For practical context, read about injection-site reactions.429

Why is the trial mentioned in US policy?

In its October 2026 draft interim enforcement-discretion policy, HHS cited a trial of a MOTS-c analogue as part of its rationale for its intention not to take enforcement action in specified circumstances when certain forms of MOTS-c acetate are compounded under Section 503A conditions. That is a policy position, not FDA approval or a finding that CB4211 and MOTS-c have the same safety or effects. The policy also cites product-characterisation and other conditions. See the MOTS-c overview for the wider regulatory context. For the conditions and the separate 2027 advisory discussion, see the US policy guide.5

What would answer the MOTS-c question?

A separate registry listing describes a MOTS-c study in adults with prediabetes, but we cannot verify that it is operating. Other records naming the same sponsor and site explicitly describe themselves as fictional or mock; the MOTS-c record does not. We previously described this listing as a planned trial, which was too certain. An unverified listing is not evidence of recruitment, a result or a reason to transfer the CB4211 findings to MOTS-c. For the broader question, see weight and appetite.678

Sources, kept close.

Selected supporting sources; this is not a complete literature review.

  1. A Phase 1a/1b study of CB4211 in healthy subjects and people with nonalcoholic fatty liver diseaseClinicalTrials.gov / US National Library of Medicine · Sponsor-submitted clinical trial registrationAccess checked 2026-11-05 · Source date: 2019-06 · 88 across three study parts; completed 2021; registry did not contain results when checked. Results were separately reported by the sponsor and a conference abstract.
  2. CB4211 phase 1a/1b topline data: August 2021 investor presentationCohBar / U.S. Securities and Exchange Commission · Sponsor investor presentationAccess checked 2026-11-05 · Source date: 2021-08-10 · Sponsor report: 23 enrolled in phase 1b, 20 completed final assessment; selected exploratory endpoints. Not a full independent clinical report.
  3. CB4211, a novel analog of MOTS-c: liver study abstract LP5Hepatology / American Association for the Study of Liver Diseases · Conference abstract with sponsor-affiliated authorAccess checked 2026-11-05 · Source date: 2021-12-01 · LP5: small 4-week exploratory cohort; abstract reports AST change −18% versus sponsor presentation −28%; cause of discrepancy unresolved.
  4. CohBar provides update on CB4211 clinical trialCohBar / U.S. Securities and Exchange Commission · Sponsor safety announcementAccess checked 2026-11-05 · Source date: 2018-11-05 · Sponsor announced temporary suspension due to mild but persistent injection-site reactions; a later presentation described formulation changes.
  5. HHS interim enforcement-discretion policy and Appendix BU.S. Department of Health and Human Services · Interim enforcement policy and substance-specific justificationAccess checked 2026-11-05 · Source date: 2026-10 · Appendix B identifies MOTS-c acetate and specified routes subject to policy conditions. HHS cites an analogue trial; policy is not FDA approval.
  6. Study of MOTS-c in adults with prediabetes and overweight or obesity (NCT07505745)ClinicalTrials.gov / US National Library of Medicine · Sponsor-submitted registry listing; operation unverifiedAccess checked 2026-11-05 · Record lists Hudson Biotech and the same site as other records explicitly labelled fictional or mock; this entry does not label itself that way. No independent confirmation of operation; no results posted when checked.
  7. TB-500 cardiovascular biomarkers listing (NCT07487363)ClinicalTrials.gov / U.S. National Library of Medicine · Sponsor-submitted registry record explicitly described as fictionalAccess checked 2026-11-05 · Source date: 2026-03-23 · The sponsor-submitted summary calls this record fictional; same sponsor and site as two other peptide listings. That association alone does not establish whether either other listing is fictional.
  8. Tesamorelin liver-fat listing: mock study (NCT07481734)ClinicalTrials.gov / U.S. National Library of Medicine · Sponsor-submitted registry record explicitly titled mock studyAccess checked 2026-11-05 · Source date: 2026-03-19 · Sponsor-submitted title calls this a mock study; same sponsor and site as two other peptide listings. It does not establish whether either other listing is fictional.
  9. Clinical Safety Data Management: Definitions and Standards for Expedited ReportingUS Food and Drug Administration · Regulatory guidance on adverse-event terminologyAccess checked 2026-11-06 · Distinguishes event intensity from regulatory seriousness criteria; does not establish whether an individual event was caused by treatment.

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