MOTS-c side effects are searched far more often than MOTS-c has been studied. The answer the record gives is short: no study has published a side effect of MOTS-c in a human, because no study has published giving MOTS-c to one. This page reports that absence with its sources and dates, sets out the one human injection record that exists for a MOTS-c-class molecule, and says what cannot be inferred from either. It is neither reassurance nor a warning; where a decision is involved, the person to make it with is a clinician. How brands appear on this site is set out on our disclosure page.
What FDA found when it looked
In May 2026 FDA's reviewers evaluated MOTS-c for the agency's Pharmacy Compounding Advisory Committee, which met on July 23–24 (FDA briefing document for MOTS-c-related bulk drug substances, evaluation dated 2026-05-11). The human-safety section is almost entirely a list of things that do not exist:
- Human exposure: "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. Therefore, potential safety risks associated with the use of MOTS-c-related BDSs in humans are unknown."
- Pharmacokinetics: no clinical study providing any.
- Adverse-event reports: two searches of FDA's database, through 2025-03-09, "retrieved no reports".
- Nonclinical toxicity: no data "to inform safety considerations for potential clinical uses".
- Immunogenicity: MOTS-c is a 16-amino-acid peptide proposed for injection; FDA wrote that it was concerned about antibody responses "due to the potential for aggregation, as well as potential peptide-related impurities", and that there were insufficient data to conclude those risks were absent.
On that basis FDA proposed that MOTS-c not be added to the list of substances 503A pharmacies may compound with. Its advisory committee then voted 7 to 5, with two abstentions, in favour of inclusion, as reported by PharmExec on 2026-07-24; the vote is advice, not a safety finding, and FDA had posted no minutes when we checked. Where MOTS-c sits on FDA's compounding lists today is on our 503A category 2 page.
We ran FDA's adverse-event database again on 2026-09-24 under three spellings (MOTS-C, MOTS C, MOTSC). It returned zero reports. FDA's own footnote explains why that number carries little weight: compounders under section 503A "generally do not report adverse events to FDA", and research-labelled vials have no manufacturer obliged to.
The one human injection record in the class
MOTS-c has a relative that has been injected into people under a registered protocol. CB4211 is an analogue of MOTS-c developed by CohBar, whose founder Pinchas Cohen was, in the company's words, among the discoverers of MOTS-c in 2012. Its phase 1a/1b trial (NCT03998514) gave single and then repeated subcutaneous doses to healthy volunteers and people with fatty liver disease: 88 participants listed, a 28-day part with 10 on drug and 10 on placebo planned, completed on 2021-04-19. Its primary outcomes were adverse events and injection-site assessments. No results have been posted to the registry, and PubMed returns no paper on CB4211 (the search's own warning line confirms the term was not found, rather than silently rewritten).
What is known comes from the company's filings with the Securities and Exchange Commission:
| Date | What CohBar reported | Source |
|---|---|---|
| 2018-11-05 | Trial "temporarily suspended in order to address mild injection site reactions that have been unexpectedly persistent"; "persistent painless bumps that can be felt under the skin"; "some of the CB4211 dose persists at the injection site" | Press release, SEC exhibit 99.1 |
| 2021-08-10 | "Well-tolerated and appeared safe with no serious adverse events"; "the only adverse events occurring in >10% of subjects receiving CB4211 in the four-week Phase 1b portion of the study were transient and generally mild to moderate injection site reactions"; 25 mg, 11 on drug and 9 on placebo | Press release, SEC exhibit 99.2 |
Two limits apply to that record, and both matter. CB4211 is not MOTS-c: it is a modified molecule designed partly to behave better as a drug, so its tolerability — good or bad — cannot be transferred to the native peptide as sold. And both statements are a sponsor's press releases, not a peer-reviewed adverse-event table; the numbers behind "only adverse events occurring in >10%" have not been published. The one thing the record does establish is that the first time a MOTS-c-class peptide was injected into people under observation, the issue that stopped the trial was at the injection site.
The one registered trial of MOTS-c itself
A registry search for MOTS-c on 2026-09-24 returned nine records. Eight measure MOTS-c in the blood as a marker inside studies of something else — exercise, anaesthesia, fasting, a newborn deafness-screening cohort. One administers it: NCT07505745, a phase 2a placebo-controlled study in 120 adults with prediabetes, recruiting, no results. Its sponsor's other seven registrations, and why they warrant reading before this one is cited as evidence, are set out on our MOTS-c dosage page. If it reports, it will be the first adverse-event table for MOTS-c in humans.
Where the side-effect lists come from
Any list of MOTS-c side effects that points to a human study is pointing at something this census did not find. Some questions are reasonable from what MOTS-c does in mice — it acts on glucose handling, so whether it lowers blood sugar in people is a fair question — and some are the generic list for any subcutaneous injection. A reasonable question is not a recorded effect. The mouse work behind the performance claims, and the commercial interests of the people who produced it, are set out on MuscleLedger's MOTS-c profile. How this site reads a side-effect record in general, and why a short or empty one is not a clean one, is on our peptide side effects page.
The contrast with a neighbouring compound is instructive. CJC-1295 also never reached approval, but it has two published trials with adverse-event tables and an FDA review that reads them line by line — see our CJC-1295 side effects page. MOTS-c has none of that; its review had nothing to read.
What the record does not contain
Any published administration of MOTS-c to a human; any pharmacokinetic figure in people; any nonclinical toxicity study; any adverse-event report in FDA's database; any peer-reviewed adverse-event table for its analogue CB4211; any data on repeated injection over months; and any analysis of research-market vials' purity or aggregation, which is where FDA's immunogenicity concern lives. MOTS-c is also prohibited at all times in sport under the World Anti-Doping Agency's list. Anyone deciding whether to use it, or whether a symptom is related to it, should take that question to a clinician who can see their history.
Sources and dates
Read 2026-09-24: FDA briefing document for MOTS-c-related bulk drug substances, Pharmacy Compounding Advisory Committee meeting of July 23–24, 2026 (evaluation dated 2026-05-11), human-safety, immunogenicity and conclusion sections, and the meeting's introductory briefing document listing FDA's proposals; ClinicalTrials.gov API v2 searches for MOTS-c (9 records) and CB4211 (1 record, NCT03998514, read in full); CohBar press releases of 2018-11-05 and 2021-08-10 as filed with the SEC; FAERS via the openFDA drug event endpoint (three spellings, zero results); PubMed search for CB4211 (zero, with the not-found warning). The committee vote is as reported by PharmExec on 2026-07-24; FDA had published no minutes when this page was written. Corrections go to the contact page.