Primary entity: YK-11Also known as: YK11; (17α,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl esterClass: performance-adjacent literacy (see page)Cluster: Performance-adjacent
YK-11 is a synthetic steroidal selective androgen receptor modulator (SARM) studied in cell models for myogenic differentiation, including follistatin upregulation that can indirectly modulate myostatin/TGF-β signaling. It is not a peptide, not FDA-approved, and is explicitly named among SARMs on the WADA Prohibited List (S1.2 other anabolic agents). Forum “myostatin inhibitor” branding oversells cell-model mechanisms as proven human pharmacology.
YK-11 is not a peptide. It is a steroidal SARM acting at the androgen receptor. Peptide Tutorials covers it because SERP and shop aisles cluster it with research peptides — chemistry class must be corrected first.
Never FDA-approved as a medicine. WADA: listed as an example SARM under S1.2 Other Anabolic Agents (alongside ostarine, LGD-4033, RAD140, S-23) — prohibited at all times. Gray-market “research” products are not clinical supply.
Key takeaways
- Not a peptide — steroidal SARM / AR partial agonist.
- Not FDA-approved; no labeled human medicine.
- WADA-prohibited SARM (S1.2 example) — athletes: check GlobalDRO, not forums.
- “Myostatin inhibitor” folk claim traces to cell-model follistatin work — not proven human myostatin-drug status.
- No dosage chart and no buy links on this site.
Questions this page answers
Next questions we answer on this page (curiosity / AI-gap map):
- What is YK-11?
- Aliases / codes
- Classification — why on a peptide site
- What it is NOT
- Mechanism (AR / follistatin)
- Evidence ladder
- What has been studied
- Safety literacy
- Regulatory & WADA
- Why no dosages
- Related compounds
- Who for / not for
Who is this profile for — and who is it not for?
For: readers who need accurate SARM-vs-peptide literacy, follistatin/myostatin myth correction, and sport/regulatory context.
Not for: anyone seeking a buy link, a “myostatin cycle,” PCT protocol, or medical advice.
What is YK-11?
YK-11 is a steroidal SARM characterized in peer-reviewed cell work as an androgen-receptor partial agonist that can drive myogenic differentiation programs differently than DHT in C2C12 models — notably via follistatin (Fst) mRNA upregulation that antibodies against follistatin can blunt. That is cell biology, not an approved anti-myostatin therapy.
New to class literacy? See What are peptides? and sibling SARM profiles such as RAD-140 and Ostarine.
| Chemistry class | Steroidal SARM / AR partial agonist |
|---|---|
| Peptide? | No |
| Myostatin drug? | No — cell-model follistatin narrative only |
| U.S. approval | Never approved |
| Sport | WADA S1.2 SARM example |
Also known as
- YK-11 / YK11 — common research codes.
- Long IUPAC steroidal ester name in primary chemistry papers.
- Mis-tags: “YK-11 peptide,” “myostatin peptide,” “YK SARM peptide” — category errors.
It is not a peptide. Cell papers describe follistatin induction that can modulate myostatin-family signaling in myoblasts — that is not the same as an approved myostatin-neutralizing drug (those sit in a different WADA growth-factor class).
How is YK-11 classified?
Investigational / research SARM (steroidal) — not an approved drug, not a dietary supplement with an established performance monograph. On this site it sits in the performance-adjacent cluster with other SARM/exercise-mimetic literacy pages because of shared SERP demand with peptides — with an explicit not-a-peptide callout.
What is YK-11 not?
| YK-11 is not… | Why that matters |
|---|---|
| A peptide | Different chemistry (steroidal AR ligand) |
| FDA-approved | No U.S. drug approval |
| A proven human myostatin inhibitor | Follistatin cell narrative ≠ approved anti-myostatin medicine |
| Something we dose or source | Refusal |
| Harmless because “research only” | WADA-prohibited anabolic agent class; animal neurotoxicity signals exist in literature |
How is YK-11 thought to work?
Primary framing: androgen receptor partial agonism without classic N/C-terminal interaction patterns described for some SARMs. Secondary literacy point from C2C12 work: follistatin upregulation contributing to myogenic regulatory-factor expression. Mechanism interest ≠ safe or effective human use.
What human vs animal vs label evidence exists?
| Evidence type | What exists (summary) | Maturity |
|---|---|---|
| Human clinical development | No completed approval pathway / no approved label | None |
| Animal | Myogenic / toxicology-adjacent animal work (incl. hippocampal oxidative-stress models in published literature) | Animal |
| Cell | C2C12 myoblast differentiation / follistatin papers | Cell |
| Forum claims | Anecdote + “myostatin” marketing | None |
This page does not invent human hypertrophy percentages or “safe cycle” thresholds in evergreen copy.
What has YK-11 been studied for?
Peer-reviewed interest centers on myogenic differentiation and AR pharmacology in models. Anti-doping and toxicology-adjacent papers also appear. Studied ≠ approved.
What safety topics come up?
No approved prescribing-information safety profile. Animal literature includes oxidative stress / mitochondrial dysfunction themes in hippocampus models — literacy flags, not personalized risk scores. Unregulated products add identity/purity risk. Androgenic-class agents carry expected class concerns (HPTA, lipids, liver — discuss with clinicians; we do not publish PCT charts). Not medical advice.
What is YK-11's regulatory status?
- U.S.: Not FDA-approved. Not a lawful dietary-supplement SARM ingredient (FDA has warned against SARMs in supplements).
- WADA: Explicit SARM example under S1.2 (YK-11 named alongside ostarine, LGD-4033, RAD140, S-23)
- Sport education: USADA and peer agencies treat SARMs as prohibited anabolic agents — check GlobalDRO.
Why doesn't this page include a dosage chart?
No approved labeled dose; “YK-11 dosage / cycle” queries seek gray-market anabolic protocols. Publishing charts would amplify harm. Literacy refusal.
Related lab literacy
Peptide reconstitution pages are not applicable. For class literacy: What are peptides?.
Related compounds and comparisons
- RAD-140 · LGD-4033 · Ostarine · S-23 · ACP-105 — other SARM literacy pages.
- MK-677 — not a SARM (GH secretagogue); common shop miscategorization.
- Cardarine — not a SARM (PPARδ); often stacked in forums.
Frequently asked questions
Is YK-11 a peptide?
No. It is a steroidal SARM / androgen-receptor partial agonist.
Is YK-11 a myostatin inhibitor?
Marketing language oversells cell-model follistatin findings. It is not an approved myostatin-neutralizing medicine.
Is YK-11 FDA approved?
No.
Is YK-11 banned in sports?
WADA lists YK-11 among SARMs under S1.2. Athletes should verify the current list and GlobalDRO.
Why is this on a peptide tutorials site?
Search and shop demand cluster YK-11 with peptides. We publish chemistry-class correction and refuse protocols.
Why no dosage information?
YMYL policy and unapproved anabolic-agent context. We will not invent a cycle chart.
Not a peptide, not FDA-approved, WADA-relevant SARM, not medical advice. Disclaimer..
Sources
The sources below were checked against PubMed, DailyMed, or the official agency page on November 10, 2026 (America/Phoenix). Links go to the publisher, PubMed, or the agency record.
- Anti-doping / analytical Sobolevsky T, Kucherova Y, Ahrens B. Detection of selective androgen receptor modulator YK-11 in a doping control sample. Drug Test Anal. 2024. doi:10.1002/dta.3604. PMID: 37946705.
- Regulatory U.S. Food and Drug Administration. FDA Warns of Use of Selective Androgen Receptor Modulators (SARMs) Among Teens, Young Adults. Accessed November 10, 2026.
- Anti-doping World Anti-Doping Agency. The World Anti-Doping Code International Standard Prohibited List 2026. Accessed November 10, 2026. Confirm the current list and GlobalDRO before relying on sport status. The 2026 list names YK-11 as a SARM example under S1.2.
- Written by
- Peptide Tutorials Staff — a group of independent researchers & writers (not clinicians)
- Published · Updated
- Oct 7, 2026 · Oct 7, 2026 · Regulatory and sport-status wording checked November 10, 2026 against current FDA labels and the 2026 WADA Prohibited List · How we source & update
Educational disclaimer: Educational only. YK-11 is not a peptide and is not FDA-approved. Includes WADA literacy. No dosing or buy links. We don't sell peptides. Read our full disclaimers.