Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library
YK-11: what the evidence says
At a glance
What it is: Caution Not a peptide. YK-11 is a synthetic steroid (a partial androgen receptor agonist) sold as a "myostatin-inhibiting SARM." It is listed here only because it is sold alongside research peptides. R1
What the evidence says: Animal cell studies only: it pushed mouse muscle cells (C2C12) to mature, partly by raising follistatin, R1 and boosted bone-cell (MC3T3-E1) growth. R2 Another study looked at gene control in breast-cancer cells. R3 No human study exists.
Biggest risks: unknown; it has never been tested for safety in people.
Rating
| Human Human evidence | None found |
| Animal Animal / lab evidence | Cell culture only R1, R2 |
| Regulatory | Not FDA-approved · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page R4, R5, R6 · named on WADA S1.2 R7 |
| Established human dose | No |
Evidence verdict: Any use in people: Unknown (no human studies)
This page reports what studies used. It is not dosing advice.
Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source
About the evidence: the "myostatin inhibitor" label comes from one cell study showing raised follistatin. There are no animal efficacy or human data.
What is it?
Related pages: enobosarm, lgd-4033, follistatin, ace-031.
Does it work?
- Animal C2C12 myoblasts: differentiation via follistatin. R1
- Animal MC3T3-E1 osteoblasts. R2
- Unknown Humans: none.
Is it safe?
- Unknown No safety data.
Gray-market vials: extra risks
A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.
Is it legal?
- US: not FDA-approved; no Drugs@FDA application found (openFDA searched Oct 26, 2026).
- Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. R4, R5, R6
- Sport: WADA 2026 S1.2 names it as a prohibited SARM, banned at all times R7.
Study details
Study details
These are amounts researchers used, not recommendations.
| Study | People / model | Route | Amount used | Follow-up | Reported | Citation |
|---|---|---|---|---|---|---|
| No human study | — | — | — | — | Cell studies only | — |
Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 27, 2026)
- R1 Kanno Y, et al. Biol Pharm Bull. 2013. PMID 23995658
- R2 Yatsu T, et al. Biol Pharm Bull. 2018. PMID 29491216
- R3 Kanno Y, et al. Exp Cell Res. 2022. PMID 36030969
- R4 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
- R5 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
- R6 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- R7 WADA. The 2026 Prohibited List, S1.2 Other anabolic agents. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
Disclaimer
This page is for education and harm reduction, not medical advice or a recommendation to use YK-11. This compound is not FDA-approved. Any product sold under this name in the US is unregulated. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).