MOTS-c

MOTS-c is a 16-amino-acid peptide associated with mitochondrial genetic information and studied as a signal linking cellular stress with metabolism. Cell experiments connect it with adaptation to limited fuel, and mouse interventions have changed insulin-related responses and physical capacity. Human investigators have mainly measured the body's own MOTS-c around exercise or compared circulating measurements across groups. Reading those experiments together helps explain the peptide's role in metabolic adaptation and why the model and measurement determine the meaning of each finding. Lee and colleagues (2015), Reynolds and colleagues (2021).

Overview

Molecular profile

Form: MOTS-c free-base parent peptide; acetate salt listed separately Source
Sequence: MRWQEMGYIFYPRKLR Source
Length: 16 amino-acid residues Source
Molecular formula: C101H152N28O22S2 (free base) Source
Molecular mass: 2174.6 g/mol (free base) Source
Genetic context: Short open reading frame within mitochondrial 12S rRNA region Source

Forms and derivatives

MOTS-c acetate

An acetate salt retaining the MOTS-c parent sequence, with acetate-associated composition dependent on salt stoichiometry.

CB4211

A modified development candidate derived from MOTS-c, identified in CohBar's own filings and separately studied in a phase1a/1b program.

MOTS-c stands for mitochondrial open reading frame of the 12S rRNA-c. Its sequence is MRWQEMGYIFYPRKLR. The name refers to a short reading frame within the mitochondrial 12S ribosomal-RNA region. Lee and colleagues' discovery paper showed that the cytoplasmic genetic code could yield the 16-residue peptide, whereas applying the mitochondrial code to the same information produced a different start/stop pattern. Thus, mitochondrial genetic origin and the machinery that translates a peptide are separate parts of the identity. Lee and colleagues (2015).

FDA's 2026 identity table distinguishes MOTS-c free base from MOTS-c acetate. An acetate salt retains the parent sequence while adding salt-associated composition. The molecular fields here describe the free base. FDA MOTS-c briefing document.

Native MOTS-c and CB4211

CB4211 is a development analogue originating from the MOTS-c program. CohBar's own filings identify it as a modified candidate and describe a completed phase 1a/1b study, with company-reported biomarker findings. Its formulation and clinical outcomes belong to that candidate. CB4211's relationship to MOTS-c explains its place in this literature; chemical modification makes it a distinct material for exposure and treatment assessment. CohBar annual report (2021).

Uses and research areas

Metabolic experiments ask how MOTS-c affects the response to insulin and the handling of glucose and lipids. The discovery study included mice exposed to high-fat diets or age-associated changes in insulin sensitivity. Later experiments examined circulating metabolites after a short intervention in diet-induced obese mice. These models provide complementary information about the tissues and metabolic processes that respond. Lee and colleagues (2015), Kim and colleagues (2019).

Exercise research explores a related stress response. Investigators measure endogenous peptide in blood and muscle around exertion and separately test whether added peptide changes performance in animals. Combining muscle samples with circulating measurements shows where the body's response appears, while animal experiments test whether added peptide changes a defined physical task. Reynolds and colleagues (2021).

Mechanism of action

In cultured cells, the discovery experiments connected MOTS-c with changes in the folate cycle and new purine synthesis. These pathways help cells move small carbon-containing units and produce building blocks for genetic material. The investigators observed accumulation of AICAR, a metabolic intermediate associated with activation of AMPK. AMPK is an energy-sensing signaling system that helps cells adjust how they obtain and use fuel. This is a candidate explanation for part of the observed metabolic response. Lee and colleagues (2015).

Kim, Son, Benayoun and Lee subsequently examined communication between mitochondria and the nucleus. Under metabolic stress, MOTS-c moved into the nucleus in an AMPK-dependent manner and influenced adaptive gene expression. The experiments implicated stress-responsive transcription factors, including NRF2. A transcription factor regulates how genetic instructions are read; changing this activity can help a cell adjust to its environment. The work adds a spatial explanation to the metabolic findings by showing how a peptide-associated signal can reach nuclear regulation in the tested cell systems. Kim, Son, Benayoun and Lee (2018).

The cell pathway should be read beside the animal measurements. In the 2019 diet-induced obesity experiment, skeletal-muscle messenger RNA for MTR, an enzyme connecting folate metabolism with production of the amino acid methionine, did not change. Measured methionine-related intermediates also remained unchanged, while plasma folate was below the assay's detection limit. The authors therefore found a different metabolic emphasis in that model. Tissue conditions and the measurement chosen can change which part of the proposed mechanism is visible. Kim and colleagues (2019).

Pharmacokinetics

The available exposure-related evidence concerns peptide breakdown in blood under laboratory conditions. FDA's 2026 evaluation identified that study and found no in-vivo pharmacokinetic or toxicokinetic study of the nominated native peptide. FDA (2026), pharmacokinetic assessment.

Knoop, Thomas and Thevis developed a mass-spectrometry method for detecting MOTS-c and investigated degradation products in blood. Shorter fragments included forms beginning at residues 2, 3, 4 and 5. This analytical work distinguishes the parent peptide from products formed after it breaks down. The loss of residues from one end of the chain provides a concrete description of susceptibility to blood peptidases, the enzymes that cleave peptides. Quantifying exposure after administration additionally requires measurements of absorption, tissue distribution and elimination in a living organism. Knoop, Thomas and Thevis (2019).

An exercise-associated rise and fall in endogenous measurements can reflect production, release and clearance together. It describes a physiological response to exertion. Estimating a drug's elimination half-life requires following its administered molecular species with an appropriate assay.

Research findings

Mouse interventions and the meaning of metabolic outcomes

Lee and colleagues reported that MOTS-c improved the response to insulin and protected against diet-associated obesity in the tested mouse models. The experiments measured how glucose was removed from blood after insulin stimulation and how much entered skeletal muscle, providing complementary views of glucose handling. Different experiments used their own animal groups, so these measurements should not be treated as a continuous sequence observed in the same mice. Lee and colleagues (2015).

The 2019 study compared blood metabolites after a three-day intervention in 14 male mice made obese by their diet, seven per group; the metabolite analysis used six per group. Blood glucose was lower after MOTS-c, and several groups of fat-related metabolites differed between groups. The study did not establish differences in body-weight change or food intake. Insulin and leptin were numerically lower, but those comparisons were also uncertain. The short experiment therefore showed a blood-glucose response without establishing corresponding changes in weight or these hormones. Kim and colleagues (2019).

Human exercise responses and separate animal performance experiments

Reynolds and colleagues studied ten sedentary healthy young men undergoing exercise and recovery sampling. Muscle and circulating MOTS-c measurements increased, with a transient blood response. The participants received no MOTS-c peptide. Separate experiments in the same publication administered peptide to mice and found improved physical capacity at several ages. Those animal interventions and human measurements answer related questions, each with a distinct material and design. Reynolds and colleagues (2021).

An independent study by von Walden and colleagues randomized 30 participants to endurance exercise, resistance exercise or control, with ten in each group. It found a significant circulating humanin response after endurance exercise and only a trend toward increased MOTS-c. Baseline peptide levels did not correlate with the tested fitness measures. Differences in the exercise task, sampling and assay are relevant when comparing the two papers. The independent result supports a more measured interpretation of the general claim that exercise reliably raises MOTS-c. von Walden and colleagues (2021).

Childhood-obesity measurements

Du and colleagues compared 40 children and adolescents with obesity with 57 controls in Hubei, China. Circulating MOTS-c was lower in the male obesity subgroup and correlated with several metabolic measures. The smaller female comparison showed no significant difference. Sex, age and the immunoassay define the population and measurement to which the result applies. Because the groups were measured at one time, the direction of the relationship with obesity remains unresolved. Du and colleagues (2018).

Liao and colleagues' 2026 atrial-fibrillation study compared plasma measurements in 39 affected patients and 39 sinus-rhythm controls. Lower MOTS-c measurements accompanied atrial fibrillation and correlated with a heart-stress marker. Separate mouse experiments tested MOTS-c and found reduced rhythm-disturbance inducibility and atrial remodeling. The human association and the animal intervention supply different views of the proposed cardiac role. Liao and colleagues (2026).

Safety and tolerability

Native MOTS-c free base and acetate are not components of an FDA-approved drug, according to FDA's 2026 review. That evaluation identified major gaps in administered-human safety and nonclinical toxicity information. The current compounding-risk page raises concerns about immune reactions, peptide impurities and characterization. An endogenous biomarker study cannot determine the safety of a manufactured product delivered through a different route or at a different exposure. FDA 2026 evaluation, Current compounding-risk record.

FDA's July 2026 committee materials concern evaluation for the compounding bulk-substances list. Advisory deliberation and product approval are different regulatory processes. The selected human exercise and obesity studies provide no adverse-event estimate for native peptide administration because none was administered in those experiments. FDA meeting record.

What the research means

MOTS-c research illustrates a developing view of mitochondria as sources of signals as well as sites of energy metabolism. Its cell studies offer a mechanistic route from metabolic stress to nuclear adaptation. The mouse interventions show that supplying the peptide can change selected metabolic and performance outcomes in those models, including experiments with meaningful null findings.

Human observations connect peptide-associated measurements with exercise, metabolism and disease, while the variability between studies helps identify which conditions need closer examination. Clinical development requires a characterized native preparation, measured exposure, an appropriate comparator and a meaningful functional or disease outcome. Published results in the selected native-peptide literature have yet to establish such a human treatment benefit. Any derivative enters that assessment with its own molecular identity.

FAQs

Was MOTS-c administered to the ten men in the exercise paper?

The human arm measured endogenous muscle and circulating MOTS-c around exercise. The same publication's administered-peptide interventions took place in separate animal and cell experiments. Reynolds and colleagues (2021).

Does a lower blood level establish a replacement need?

The childhood-obesity comparison found a lower male-subgroup measurement and no significant female-subgroup difference. Its cross-sectional design cannot resolve whether the association is a cause, consequence or adaptation. It defines no validated replacement target. Du and colleagues (2018).

Does every exercise study show the same MOTS-c response?

The ten-person study reported an increase, while a separate randomized exercise study found only a trend toward increased circulating MOTS-c after endurance exercise. The exercise task, sampling and assay help interpret this variation. Reynolds and colleagues (2021), von Walden and colleagues (2021).

Can CB4211 findings establish native MOTS-c treatment effects?

CB4211 is a modified candidate with its own formulation and clinical program. Native MOTS-c would require its own exposure, outcome and safety measurements. CohBar annual report (2021).

What does blood-incubation breakdown reveal?

It identifies shorter peptide products formed after MOTS-c is added to blood in a laboratory. A living person's absorption, distribution and clearance require a separate in-vivo study. Knoop, Thomas and Thevis (2019).

Humanin offers another mitochondrial-derived peptide example, with a stronger emphasis on cell survival and different human biomarker patterns. Elamipretide targets mitochondrial membrane biology through a distinct molecular structure and indication-specific clinical program. AOD-9604 provides a comparison for distinguishing a preclinical metabolic hypothesis from outcomes in human weight-management studies.

References

The bibliography credits original metabolic, localization, exercise, biomarker and analytical studies. FDA records supply current identity and safety context, and the sponsor filing identifies the separate CB4211 development candidate.

Lee C, Zeng J, Drew BG, Sallam T, Martin-Montalvo A, Wan J, Kim SJ, Mehta H, Hevener AL, de Cabo R, Cohen P. The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance. Cell metabolism. 2015;21(3):443–454. DOI: 10.1016/j.cmet.2015.02.009.
Identifies the 16-residue reading frame and examines folate/purine-related signaling and mouse insulin-related responses.
Kim KH, Son JM, Benayoun BA, Lee C. The Mitochondrial-Encoded Peptide MOTS-c Translocates to the Nucleus to Regulate Nuclear Gene Expression in Response to Metabolic Stress. Cell Metabolism. 2018;28. DOI: 10.1016/j.cmet.2018.06.008.
Examines stress-associated nuclear localization and adaptive gene regulation in cell systems, including AMPK dependence and NRF2 interaction.
Kim SJ, Miller B, Mehta HH, Xiao J, Wan J, Arpawong TE, Yen K, Cohen P. The mitochondrial-derived peptide MOTS-c is a regulator of plasma metabolites and enhances insulin sensitivity. Physiological Reports. 2019;7(13):e14171. DOI: 10.14814/phy2.14171.
Reports short mouse metabolic changes, unchanged weight/food intake, insulin/leptin trends and a different folate-cycle response from the cell model.
Reynolds JC, Lai RW, Woodhead JST, Joly JH, Mitchell CJ, Cameron-Smith D, Lu R, Cohen P, Graham NA, Benayoun BA, Merry TL, Lee C. MOTS-c is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis. Nature Communications. 2021;12:470. DOI: 10.1038/s41467-020-20790-0.
Combines endogenous exercise measurements in ten men with separately labeled cell and mouse peptide interventions.
Du C, Zhang C, Wu W, Liang Y, Wang A, Wu S, Zhao Y, Hou L, Ning Q, Luo X. Circulating MOTS-c levels are decreased in obese male children and adolescents and associated with insulin resistance. Pediatric diabetes. 2018. DOI: 10.1111/pedi.12685.
Compares 40 obesity and 57 control participants, retaining lower male-subgroup measurements and the female-subgroup null finding.
von Walden F, Fernandez-Gonzalo R, Norrbom J, Emanuelsson EB, Figueiredo VC, Gidlund EK, Norrbrand L, Liu C, Sandström P, Hansson B, Wan J, Cohen P, Alkner B. Acute endurance exercise stimulates circulating levels of mitochondrial-derived peptides in humans. Journal of Applied Physiology. 2021;131(3):1035–1042. DOI: 10.1152/japplphysiol.00706.2019.
Randomizes 30 participants across endurance, resistance and control conditions; reports a significant humanin response and a MOTS-c trend after endurance exercise.
Liao Y, Xu J, Jiao Y, Sun X, Gao M, Ding Y, Cai D, Shen Y, Zhou X, Han W. Humanin and MOTS-c Attenuate Atrial Fibrillation by Suppressing Fibrosis and Mitochondrial Dysfunction. Biomedicines. 2026;14(5):1048. DOI: 10.3390/biomedicines14051048.
Combines endogenous human measurements with separate HNG/MOTS-c mouse and cell interventions; its human arm does not test peptide treatment.
Knoop A, Thomas A, Thevis M. Development of a mass spectrometry based detection method for the mitochondrion-derived peptide MOTS-c in plasma samples for doping control purposes. Rapid Communications in Mass Spectrometry. 2019;33(4):371–380. DOI: 10.1002/rcm.8337.
Develops peptide-specific detection and identifies in-vitro blood breakdown products, providing analytical context for exposure measurements.
CohBar, Inc. Annual Report on Form 10-K for the fiscal year ended 31 December 2021. U.S. Securities and Exchange Commission filing, 2022. CB4211 program section.
Sponsor filing identifies CB4211 as a modified MOTS-c candidate and describes historical clinical development; native-peptide evidence remains separate.
U.S. Food and Drug Administration, Center for Drug Evaluation and Research. FDA Briefing Document: MOTS-c-Related Bulk Drug Substances (MOTS-c free base and MOTS-c acetate). Pharmacy Compounding Advisory Committee, 23–24 July 2026.
Records free-base sequence/formula/mass and reviews missing in-vivo exposure and safety evidence plus the in-vitro degradation study.
U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Current agency webpage, accessed 13 October 2026.
Identifies substance-specific gaps in safety, aggregation, impurities and characterization for compounded peptide products.
U.S. Food and Drug Administration. July 23–24, 2026: Meeting of the Pharmacy Compounding Advisory Committee. Meeting webpage, accessed 13 October 2026.
Identifies the bulk-substance review context and explains the advisory status of committee recommendations.

Glossary

Mitochondrial-derived peptide: A peptide associated with a small reading frame within mitochondrial genetic information.
AMPK: An energy-sensing signaling system helping cells adjust how they obtain and use fuel.
AICAR: A purine-pathway intermediate associated with AMPK activation in the discovery experiments.
Folate cycle: A set of reactions moving small carbon-containing units used in cellular metabolism.
Transcription factor: A protein that regulates how genetic instructions are read.
Endogenous: Produced within the organism rather than added as an experimental intervention.
Metabolomics: Measurement of many small metabolic molecules to characterize a biological sample.
ELISA: An antibody-based measurement of a target-associated signal.