MOTS-c

MOTS-c is a mitochondrial-derived peptide, a 16-amino-acid signaling molecule encoded not in the cell nucleus but in the 12S rRNA region of mitochondrial DNA. First described in 2015, it was reported to promote metabolic homeostasis and, in mice, to reduce diet-induced obesity and insulin resistance [1]. Because its blood levels rise with physical activity and its biology overlaps with the metabolic benefits of exercise, it is frequently marketed as an "exercise mimetic."

That marketing has run well ahead of the human evidence. MOTS-c has no FDA approval for any indication, and, verified directly against PubMed, no published human randomized controlled trial has ever tested MOTS-c as a weight-loss treatment. In a draft enforcement policy from October 28, 2026, HHS says it does not intend to bring enforcement action against licensed 503A pharmacies and physicians that compound MOTS-c acetate for subcutaneous or intramuscular use under ten conditions [7]. That alters the supply route, not the state of the evidence. The compelling metabolic and exercise-capacity findings come from mouse and cell studies; the human studies that exist measure circulating MOTS-c as a biomarker of exercise or aging, not as an administered drug. For the full evidence review, see our separate deep-dive: /research/mots-c-weight-loss-evidence.

MOTS-c has never been approved by FDA, for anything. HHS's draft enforcement-discretion policy of October 28, 2026 is interim, not final, and binding on neither HHS nor the public; comments close November 13, 2026. It fills the gap while FDA uses rulemaking to decide whether MOTS-c should be on the 503A bulk drug substances list. During that period, HHS says it does not intend to bring enforcement action against a State-licensed pharmacy, a licensed physician, or a Federal facility compounding MOTS-c acetate, as long as all ten conditions are met [7]. HHS also restates that compounded drugs are unapproved and that FDA gives them no review for safety, effectiveness, or quality.

Route limits: the policy covers MOTS-c acetate in subcutaneous or intramuscular injectable forms only [7]. Oral and nasal MOTS-c products fall outside it.

The policy's other conditions: a prescription for an individual patient, MOTS-c as the product's only active ingredient, and a 510(k)-cleared syringe as the only device in the package. The bulk peptide comes from an FDA-registered manufacturer and carries a certificate of analysis with results for identity, purity, potency, endotoxin, heavy metals, microbial limits and impurities. The compounder reports any serious adverse event or quality defect to FDA MedWatch and the states [7], and the label carries the policy's sentence: "This is a compounded drug product. Not for resale."

History: FDA kept MOTS-c in Category 2 starting September 29, 2023, and removed it on April 22, 2026. The Pharmacy Compounding Advisory Committee voted to list it over CDER's recommendation against [7]. HHS based its decision on new certificates of analysis that supply the impurity, residual-solvent, endotoxin and microbial data CDER had said were absent; on documented use, mostly of single-ingredient products; and on its interpretation of the safety record, which points to rodent studies without systemic toxicity and to a randomized, placebo-controlled trial of an analog of MOTS-c that found no serious adverse events [7]. We could not find a published report of that analog trial in PubMed, and a safety result for an analog is not a weight-loss result for MOTS-c.

The peptide is read off a short open reading frame tucked inside the mitochondrial 12S ribosomal RNA gene, distinguishing it from the vast majority of proteins encoded by nuclear DNA. Once produced, it can act locally in the mitochondria and also translocate to the cell nucleus under metabolic stress, where it is proposed to help regulate genes involved in metabolism and antioxidant defense [2].

In mouse studies, MOTS-c has been shown to help regulate adipose-tissue (fat) homeostasis and to protect against the metabolic dysfunction that follows ovariectomy [4], and a 2021 Nature Communications paper described it as an exercise-induced, mitochondrially encoded regulator of age-dependent physical decline and muscle homeostasis, though here too the headline results came from mice [3]. This is legitimate, actively studied mitochondrial biology; it is not the same thing as a demonstrated human weight-loss mechanism.

The founding 2015 paper in Cell Metabolism reported that MOTS-c improves insulin sensitivity and protects mice against diet-induced obesity [1]. Follow-up mouse work extended this to adipose-tissue regulation [4], and the 2021 Nature Communications study linked MOTS-c to exercise capacity and muscle homeostasis, also in mice [3]. These are the studies most often cited to sell MOTS-c online.

The human literature is real but answers a different question. A 2021 study found that a single bout of endurance exercise raises circulating levels of mitochondrial-derived peptides, including MOTS-c, in people [5]. That work establishes it as an exercise-responsive biomarker; it does not test whether administering it causes weight loss. A search of PubMed for a human randomized controlled trial of MOTS-c as a weight-loss therapy returns zero results as of this verification. Reviews of mitochondrial-derived peptides in aging describe MOTS-c as a promising research target whose levels decline with age, while noting the therapeutic case in humans remains unproven [6].

There is no established or clinically validated human dose. Because no human randomized trial has tested MOTS-c as a weight-loss or metabolic therapy, no dose has been shown to be safe or effective in people, and figures circulated on vendor sites and forums are not backed by clinical evidence. We do not publish a dosing protocol for this reason; a genuine dosing guide would imply a validated regimen that does not exist.

MOTS-c is not FDA-approved for any human indication and is not listed in DailyMed. Outside the HHS compounding policy, it is sold online as a "research use only, not for human consumption" research chemical, a disclaimer that lets vendors ship it while sidestepping drug-marketing rules. Because it is unregulated, no agency verifies the identity, purity, sterility, or actual dose of what is in the vial, and self-injecting an unverified compound carries real risk of contamination, infection, and unknown dosing, with no proven human efficacy to offset that risk.

A clinic that prescribes MOTS-c through a licensed clinician and a 503A pharmacy working under the HHS conditions (registered manufacturer, lot-level certificate of analysis, single-ingredient product, MedWatch reporting) is a material difference from the gray market [7]. It does not change the underlying evidence picture: even under a doctor's supervision, no human trial has shown MOTS-c causes weight loss, so treat it as an unproven, off-label compounded peptide and discuss the lack of efficacy data with your prescriber before starting it. Athletes should know that WADA's 2026 Prohibited List names MOTS-c under S4.4, metabolic modulators, prohibited at all times [8].