MOTS-c won an FDA advisory vote. FDA’s own review found no study of it given to people.

Why this note exists

MOTS-c is one of the most widely stocked compounds in pepmg's index. In the index generated on September 8, 2026, 101 of 108 vendors carried it, across 210 listings; only three compounds were carried by more vendors.[17] The most common vial size was 10 mg, on 95 of the 210 listings.[17] It was also one of the six peptide families the July advisory committee backed, which pepmg covered in its note on the vote. That note gave MOTS-c one line. This one reads FDA's full review of it.

A note on what kind of evidence this is: almost nothing below is human data, and each paragraph says which species it is about. Mouse and rat results are labeled as animal results in the same sentence as the number. The one human drug trial discussed is of an analogue, CB4211, and is labeled as such every time.

The vote

What the committee was asked, and what FDA staff had proposed

MOTS-c reached the committee by an unusual route. Wells Pharmacy Network nominated it for the 503A Bulks List, then withdrew the nomination, and FDA chose to evaluate both MOTS-c free base and MOTS-c acetate "on its own initiative."[1] The nomination proposed 5 mg and 10 mg products for subcutaneous injection, for insulin resistance, obesity, osteoporosis, vascular calcification, muscle and fat metabolism and longevity.[1] The meeting considered it for two of those uses, obesity and osteoporosis.[2]

FDA's review, dated May 11, 2026, concluded that "a balancing of the criteria weighs against MOTS-c free base or MOTS-c acetate being placed on that list," and ended: "we propose not adding MOTS-c (free base) or MOTS-c acetate to the 503A Bulks List."[1] The committee disagreed. STAT reported a 7 to 5 vote to add MOTS-c for obesity and osteoporosis, and reported FDA experts as saying they had "no authority to require compounders to submit safety or efficacy data once a substance is added to the list."[3]

A recommendation is not a listing. The committee advises FDA, and FDA's briefing document says the agency "will not issue a final determination on the issues at hand until input from the advisory committee process has been considered and all reviews have been finalized."[1] FDA's 503A bulk substances page, content current as of May 14, 2026, did not list MOTS-c when checked on September 12, 2026, and the meeting page had posted no summary minutes or vote record.[5][2] FDA's safety-risk page still carries MOTS-c among withdrawn nominations, with the entry: "FDA has not identified any human exposure data on drug products containing MOTs-C administered via any route of administration."[4]

The review

What FDA looked for and did not find

Each figure is FDA's statement about what the nominator did not submit and FDA did not identify, from the May 11, 2026 evaluation.[1]

The human safety section is short because there was nothing to put in it. FDA writes that "the nomination did not include, and FDA has not identified, any clinical studies or human exposure data for MOTS-c via any route of administration," and that "potential safety risks associated with the use of MOTS-c-related BDSs in humans are unknown."[1] Its searches of the FDA Adverse Event Reporting System retrieved no reports, a result FDA itself qualifies: compounders under section 503A "generally do not report adverse events to FDA."[1] Outsourcing facilities reported compounding no MOTS-c products between January 2017 and December 2025.[1]

Two findings go to whether an injected vial could do anything at all. The only pharmacokinetic work FDA found was in vitro: when MOTS-c was incubated in human whole blood, a doping-control laboratory reported that it was broken down into shorter fragments, and FDA summarizes the authors as stating that this hydrolysis "was rapid."[1][14] FDA's conclusion: "It remains to be determined whether exogenous administration of MOTS-c to humans can generate pharmacologically active concentrations of the peptide over time."[1] Separately, FDA judged both forms "not well-characterized," because the certificates of analysis it reviewed reported purity but no results for impurities, aggregates or bacterial endotoxin, and it said it could not rule out immunogenicity when the peptide is injected.[1]

The animal record

Why anyone is interested: mice, rats and cells

Every result in this section is from rodents or cell culture. MOTS-c was described in 2015 as a 16-amino-acid peptide encoded in mitochondrial DNA.[11] In that first paper, as FDA summarizes it, male mice on a high-fat diet given 0.5 mg/kg/day by intraperitoneal injection for eight weeks weighed about 20% less than vehicle-treated mice at the end of treatment.[1][11] A 2021 study reported better treadmill performance in young, middle-aged and old mice; according to FDA's summary of it, mice started on intermittent treatment at 23.5 months had a median lifespan of 970 days against 912 on vehicle.[1][12] Two of that paper's authors declared that they were consultants and shareholders of CohBar, the company developing a MOTS-c analogue.[12] Other work FDA reviewed covered bone cells in culture, bone loss in a mouse skull model and vascular calcification in rats.[1]

FDA's reading of that literature is the sentence to keep: the findings "should be interpreted with caution because the nonclinical pharmacological studies of MOTS-c published to date have been restricted to rodent models and have not assessed dose-response relationships," and the molecular target "remain[s] unknown making it difficult to predict which organs are likely to be affected."[1]

The human literature

Studies in people measure the MOTS-c the body already makes

There is human MOTS-c research. It measures the body's own circulating peptide, not a synthetic one given as a drug. In one example, 30 people were randomized to endurance exercise, resistance exercise or rest; the authors reported that MOTS-c "showed a trend to increase" after endurance exercise, while a related peptide, humanin, rose significantly.[13] The 2021 mouse paper above also reported that in humans, "exercise induces endogenous MOTS-c expression in skeletal muscle and in circulation."[12] Measuring a peptide the body makes is a different experiment from injecting a synthetic one, and neither study gave anyone MOTS-c.

Even the measurements carry a caveat. The laboratory that built the doping-control test reported that endogenous levels in 20 healthy people, measured by a commercial ELISA kit at 45.9 to 218.5 ng/mL, "could not be confirmed" by mass spectrometry, and that the two methods gave "considerable differences in measured MOTS-c levels."[14]

The analogue

CB4211: the one human drug trial, of a different molecule

The one drug trial we found in this family is of CohBar's CB4211, which the company described as "a novel and improved analog of MOTS-c."[6] Its phase 1a/1b study was randomized, double-blind and placebo-controlled, ran from July 2018 to April 2021, and lists an actual enrollment of 88; no results are posted on the registry.[7] Its primary outcomes were safety measures.[7] In the phase 1b stage, 20 obese people with nonalcoholic fatty liver disease received 25 mg of CB4211 or placebo by subcutaneous injection once a day for four weeks.[6]

The company's topline announcement said that exploratory endpoints in that stage showed "robust and significant reductions in key biomarkers of liver damage, ALT and AST, a significant decrease in glucose levels, and a trend towards lower body weight after four weeks of treatment," and reported no serious adverse events; the only adverse events in more than 10% of CB4211 recipients were injection site reactions.[6] On liver fat, the outcome a fatty-liver drug ultimately has to move, it said: "Both the CB4211 and placebo groups had substantial reductions in liver fat content compared to baseline."[6] A PubMed search for CB4211 returns no records.[9]

Then the program stopped. In an August 2023 merger filing, CohBar's board listed among its reasons "CohBar's belief that the formulation of CB4211 used in the Phase 1b stage of its trial is not suitable for further development, and efforts to develop an improved formulation have not been successful."[8] CB4211 is not MOTS-c, and four weeks of data on an analogue in 20 people cannot be carried over to the peptide vendors sell.

What comes next

The first placebo-controlled trial of MOTS-c itself

A ClinicalTrials.gov search for MOTS-c on September 12, 2026 returned nine records, and only one of them lists MOTS-c as an intervention.[16] That one, NCT07505745 (MOTS-MET), is a phase 2a, randomized, quadruple-masked, placebo-controlled trial sponsored by Hudson Biotech at Peking University Shenzhen Hospital, with an estimated 120 adults with prediabetes and overweight or obesity.[10] Participants receive MOTS-c or placebo by subcutaneous injection at a fixed dose once daily for 12 weeks, alongside lifestyle counseling; the registry does not state the dose.[10]

Its primary outcomes are change in the Matsuda index, an insulin-sensitivity measure from a glucose tolerance test, at 12 weeks, and treatment-emergent adverse events at 16 weeks; secondary outcomes include HbA1c, fasting glucose and anti-drug antibodies.[10] The listed start date is February 2, 2026, and the record was first submitted on March 14, 2026.[10]

When it reports, it will be the first controlled human evidence on MOTS-c itself, and it will be evidence about insulin sensitivity over 12 weeks in people with prediabetes. It will not be evidence about osteoporosis, the other use the committee voted on, or about longevity.

In sport, it is already prohibited

USADA reported that MOTS-c was added as an example to section S4, hormone and metabolic modulators, of the 2024 WADA Prohibited List, noting that it "is heavily marketed by wellness and anti-aging clinics and on social media as a weight loss peptide, even though it is an experimental peptide not approved for human therapeutic use."[15] FDA's review records the same status through the Global DRO database.[1] A mass-spectrometry test for MOTS-c in plasma, validated to WADA's laboratory standard, was published in 2019.[14]

Three things this note is not saying

First, it is not saying MOTS-c does not work. The honest statement is that its effect in people has not been measured, and absence of evidence runs in both directions.[1]

Second, it is not saying MOTS-c is dangerous. FDA's position is that the risks "are unknown," which is not the same as known to be harmful; the review names immunogenicity and product quality as concerns it could not rule out.[1]

Third, it is not saying the committee acted improperly. Advisory committees exist to give FDA an outside view, and FDA has not yet ruled.[2] What this note is saying is narrower: the peptide 101 of 108 tracked vendors list was recommended for compounding at a point when FDA could find no study of it given to people, no in vivo pharmacokinetic study in any species and no toxicology study, and the first trial that could change that is still recruiting.[1][10][17]

Questions people are asking