MOTS-c: what the molecule is, what the cell, mouse and human studies measured, and where its regulatory status stands

What MOTS-c is: a peptide encoded in mitochondrial DNA#

MOTS-c stands for "mitochondrial open reading frame of the 12S rRNA type-c." Almost every peptide in a research catalog is encoded in the cell nucleus or designed in a laboratory. MOTS-c is neither: its coding sequence sits inside the mitochondrial genome, within the region that codes for the 12S ribosomal RNA ^[1]. It belongs to a small group called mitochondrial-derived peptides, and the earlier discovery of a mitochondrial open reading frame encoding humanin prompted the search that found it ^[1].

The peptide is 16 amino acids long. Its sequence is MRWQEMGYIFYPRKLR, or Met-Arg-Trp-Gln-Glu-Met-Gly-Tyr-Ile-Phe-Tyr-Pro-Arg-Lys-Leu-Arg in the three-letter form used in the FDA's 2026 briefing document ^[10]. The free peptide has the molecular formula C101H152N28O22S2, a molecular weight of 2,174.6 g/mol, CAS registry number 1627580-64-6 and UNII A5CV6JFB78 ^[10]. The acetate salt, which is what many suppliers ship, has a higher nominal molecular weight (2,234.64 g/mol for a one-to-one acetate) and no separate CAS number ^[10]. The two methionines and the tryptophan matter later, when we come to the COA, because methionine oxidizes readily during storage.

MOTS-c discovery: Lee et al. 2015 and the groups that studied it#

MOTS-c was reported in the March 2015 issue of Cell Metabolism by Changhan Lee, Pinchas Cohen and colleagues at the University of Southern California, with co-authors from UCLA and the National Institute on Aging ^[1]. The paper identified the short open reading frame inside the mitochondrial 12S rRNA gene, showed that the 16-residue peptide is actually made, and asked what it does in cells and mice. The abstract states that MOTS-c "regulates insulin sensitivity and metabolic homeostasis" and that "its primary target organ appears to be the skeletal muscle" ^[1].

Most of the mechanistic work since then has come from the same USC laboratories and their collaborators: the 2018 nuclear-translocation paper and the 2021 exercise paper are from Lee's group ^[2][3], and the 2021 genetics paper paired USC with Japanese cohorts ^[4]. Independent groups have mainly measured MOTS-c in human blood ^[5][6]. Readers should also know that Cohen co-founded, and Lee consulted for, CohBar, the company that tried to develop a MOTS-c analogue as a drug ^[15].

What the cell and mouse studies measured#

The table lists the primary studies with the system each used and what it measured; our guide to reading published peptide research explains why the model matters as much as the finding.

The cell work: folate cycle, AMPK and the nucleus#

The 2015 paper's mechanistic claim is metabolic: in cells, MOTS-c inhibited the folate cycle and the de novo purine synthesis that depends on it, and that inhibition activated AMPK, the enzyme cells switch on when fuel is short ^[1]. The 2018 follow-up asked where the peptide goes. In HEK293 cells under glucose restriction, serum deprivation or oxidative stress, MOTS-c moved into the nucleus; blocking AMPK stopped the movement and AMPK activators promoted it. There it bound antioxidant response elements in promoters such as NQO1 and HO-1, interacted with the transcription factor NRF2, and changed the expression of a broad set of genes ^[2]. These are cell-culture findings; the paper describes no live-animal experiments.

The mouse work: high-fat diets, aging and exercise#

In the 2015 study, mice given MOTS-c were protected from the insulin resistance that develops with age and with a high-fat diet, and from diet-induced obesity, with skeletal muscle as the apparent site of action ^[1]. The 2021 Nature Communications paper extended this to physical function. Mice treated at 2, 12 and 22 months performed better than untreated mice of the same age on a rotating rod and an accelerating treadmill, and a cohort treated three times a week from 23.5 months showed increased physical capacity and healthspan, measured by grip strength, stride length and a walking test ^[3][15]. The 2021 Aging paper added genetics: in high-fat-fed male mice the native peptide changed body mass and glucose tolerance while the K14Q variant did not; female mice were unaffected by either ^[4].

One caution applies to all of this: FDA's 2026 review of the nominated literature noted that these studies contained no assessments relating the amount given to the size of the effect, and that the peptide's molecular target is unknown ^[10].

Human data: circulating MOTS-c levels, not trials of the peptide#

Every human study of MOTS-c itself is observational: the peptide was measured in blood, muscle or the genome and associations were sought. None gave native MOTS-c to people.

• Exercise. In the 2021 Nature Communications study, sedentary healthy young men exercised on a stationary bicycle, with muscle and plasma sampled before, during and after exercise and after four hours of rest. MOTS-c in skeletal muscle rose nearly 12-fold and stayed partly elevated after rest; in plasma it rose about 50% and returned to baseline ^[3][15].
• Children and adolescents with obesity. A 2018 case-control study in Hubei Province, China (40 with obesity, 57 controls) found lower serum MOTS-c in the obese group (472.6 versus 561.6 ng/mL), a difference driven by boys and not significant in girls. In boys, MOTS-c correlated negatively with BMI, waist circumference, fasting insulin, HOMA-IR and HbA1c ^[5].
• Adults with type 2 diabetes. A 2019 cross-sectional study of 225 Qatari adults measured serum MOTS-c in controls, prediabetes and two type 2 diabetes groups. Levels differed across groups (ANOVA p = 0.007), but only controls versus poorly controlled diabetes survived post-hoc testing, and both patients and controls were overweight or obese ^[6].
• Genetics. A 2021 meta-analysis of 27,527 people in three cohorts found that men carrying the m.1382A>C variant, which changes lysine 14 to glutamine in MOTS-c, had a higher prevalence of type 2 diabetes, confined in the Japanese J-MICC cohort to the least physically active third ^[4].

CB4211: the one clinical trial, and what happened to the company#

The only interventional human study in this area did not use MOTS-c. It used CB4211, which its sponsor CohBar described as an analogue of MOTS-c ^[8]. CohBar was co-founded by Pinchas Cohen, senior author of the 2015 discovery paper ^[15]. The trial, NCT03998514, was a phase 1a/1b study sponsored by CohBar, Inc., with 88 participants, that began in July 2018 and was completed in April 2021 ^[7].

CohBar's August 10, 2021 announcement described the design. Phase 1a assessed single and multiple ascending amounts over one week in 65 healthy adults. Phase 1b gave CB4211 or placebo once daily for four weeks to 20 adults with obesity and non-alcoholic fatty liver disease (11 on CB4211, 9 on placebo). The primary endpoints were safety and tolerability; liver fat, body weight and metabolic markers were exploratory ^[8]. Liver fat by MRI-PDFF fell 5.03 percentage points with CB4211 and 4.88 with placebo, so there was no difference between groups. ALT fell 21% with CB4211 and rose 4% with placebo, which the company called statistically significant; AST and fasting glucose also differed. The only adverse events in more than 10% of CB4211 participants were transient, mostly mild-to-moderate reactions at the site of administration ^[8]. These are company-reported topline figures from a 20-person, four-week exploratory analysis, not a peer-reviewed publication.

The program did not continue. On November 1, 2023, CohBar announced its intention to liquidate and dissolve; the Form 8-K filed that month records the resignation of its chief executive, chief financial officer and most of its board ^[9]. FDA's 2026 review of MOTS-c itself identified no clinical studies and no registered trials of the native peptide ^[10].

MOTS-c regulatory status: FDA, the 503A bulks list and WADA#

MOTS-c is not a component of any FDA-approved drug, has no USP or NF monograph, does not appear in the European or Japanese Pharmacopoeia, and the European Medicines Agency lists no authorized product containing it. Outsourcing facilities reported no MOTS-c products to FDA between January 2017 and December 2025 ^[10].

The open question is whether MOTS-c will be placed on the FDA's 503A bulk drug substances list, which governs what state-licensed compounding pharmacies may use. FDA's Pharmacy Compounding Advisory Committee took up MOTS-c (free base and acetate) on July 23, 2026, alongside BPC-157, KPV and TB-500 ^[11]. FDA's briefing document proposed not adding either form, citing the absence of human exposure data, the unknown molecular target, the lack of standard nonclinical safety studies, and concern about immunogenicity from peptide aggregation and impurities ^[10]. The committee nonetheless voted 7 in favor, 5 against, with 2 abstentions, to recommend inclusion ^[12]. The recommendation is non-binding; FDA has not issued a final determination, and the rulemaking that would follow is expected to run into 2027 ^[12]. Until then MOTS-c is not approved, not on the bulks list, and under review.

What has not been studied#

• Native MOTS-c in people. No published interventional study and no registered trial of the peptide itself ^[10]; the one clinical trial used the analogue CB4211 ^[7][8].
• Human pharmacokinetics. The only human-related laboratory study measured how MOTS-c breaks down in human blood in vitro ^[10].
• Standard nonclinical safety studies ^[10].
• A receptor or binding partner. The molecular target is unknown; AMPK activation and NRF2 interaction are downstream observations in cells ^[2][10].
• Independent replication of the mouse physical-performance findings, which come from the discovering laboratory ^[3][15].
• Females. The 2021 genetics paper saw its association and mouse effect in males only ^[4]; the 2018 pediatric study found no difference in girls ^[5].
• A validated assay. Published circulating levels differ by more than an order of magnitude between immunoassay kits ^[5][6].

What a MOTS-c Certificate of Analysis has to show#

Renuvia's current MOTS-c lot, VB-2609-01-BR (10 mg vials), carries a supplier-provided certificate from KMD Analytical dated October 7, 2026, labelled as a supplier COA in the COA library. It reports an HPLC-DAD purity of 99.31%, a confirmed identity result, and a measured content of 11.17 mg, 111.7% of label ^[14]. Lots tested on Renuvia's behalf by Freedom Diagnostics Testing report HPLC-UV purity, LC-MS identity and measured content; pending lots show as pending. Whichever laboratory issued it, a MOTS-c COA should let you check:

1. Identity by mass spectrometry matching the 16-residue sequence. The free peptide's mass sits near 2,174 Da; an acetate salt dissociates in the instrument, so the spectrum should show the free peptide, not 2,235 Da ^[10]. A mass about 16 or 32 Da higher than expected points to methionine oxidation.
2. Purity by HPLC with the chromatogram shown. MOTS-c has two methionines and a tryptophan, all oxidation-prone, so adjacent peaks should be quantified rather than folded into a rounded figure. Our purity report guide explains the common misreadings.
3. Which form was tested. FDA treats MOTS-c free base and acetate as distinct substances with different molecular weights ^[10]; measured content in milligrams depends on which one it is.
4. Measured content stated separately from purity. Purity says how clean the peptide is; content says how much is in the vial.
5. The lot number matching the vial, the laboratory's name, and a report number you can check. Supplier-issued certificates should be labelled as such.
6. What is missing. FDA flagged that the nominated MOTS-c certificates lacked impurity, aggregate, bioburden and endotoxin data ^[10]. A research-grade COA usually covers purity, identity and content only.

The guides to reading a Certificate of Analysis, checking that a COA is genuine and HPLC and mass spectrometry walk through each section of a report, and the storage and stability guide covers why oxidation of a methionine-containing peptide shows up on a chromatogram over time.