D tier · weak
The entire evidence base is a small number of in vitro cell-culture papers from a single research group plus limited animal work, with no human trial of any kind and no human pharmacokinetic or safety data whatsoever.
yk-11
YK-11 is a synthetic steroidal compound characterised as a gene-selective partial agonist of the androgen receptor with reported effects on follistatin expression in cultured myoblasts. There are no published human trials, no human pharmacokinetic data and no human safety data, so nothing about its behaviour in people can be stated from evidence.
// we supply this one
available as a research reagent
≥ 98% HPLC · research solution · batch certificate published. Grade D above is our own and is not adjusted because we stock it.
the explanation
Everything known about YK-11 comes from cells in dishes and a small amount of animal work, mostly from one research group. Nobody has published a study of what it does in a human body, including how long it lasts or what it does to the liver.
regulatory status
Not approved by FDA or any regulator; never entered clinical development; WADA-prohibited; not a lawful dietary supplement ingredient
YK-11 has never been approved for any indication and has never entered formal clinical development; it is documented as a novel designer drug rather than an investigational medicine. FDA classifies SARMs in bodybuilding products as unapproved drugs and has issued public safety notifications naming liver injury and acute liver failure, heart attack and stroke; Health Canada has separately warned that SARMs are not authorised in Canada for any use and can pose serious risks including heart attack, stroke and liver damage, with unknown long-term effects. YK-11 is prohibited at all times in sport under the WADA anabolic agents category and is named in the NIH LiverTox SARMs chapter. The SARMs Control Act (S.2742, 2018; S.2895, 2019) proposed Schedule III placement for SARMs but was never enacted.
how it works · proposed mechanism
YK-11 is a synthetic steroidal androgen receptor partial agonist reported to act partly through follistatin induction.
Gene-selective partial AR agonism
YK-11 binds the androgen receptor but does not induce the N/C terminal interaction required for full receptor activation, producing a gene-selective transcriptional response. This distinguishes it mechanistically from full AR agonists such as testosterone.
Follistatin induction in myoblasts
In C2C12 mouse myoblast culture, YK-11 increased follistatin expression and promoted myogenic differentiation, and because follistatin antagonises myostatin this is the basis of the 'myostatin inhibitor' description. The finding is a cell-culture result and has not been demonstrated in any human tissue.
Steroidal scaffold
Unlike the non-steroidal aryl-propionamide SARMs, YK-11 retains a steroid nucleus, so assumptions about hepatic and endocrine handling derived from non-steroidal SARMs do not transfer to it. Its metabolic fate in humans is uncharacterised.
what’s reported
evidence shape
6 sourcesThe composition of the cited literature by study type. This describes the shape of the evidence, not its quality — and it does not by itself set the grade.
⚠ the catch
YK-11 is marketed as the most potent compound in this category on the strength of cell-culture potency comparisons against DHT, a claim that says nothing about what happens in a human body. It is also steroidal rather than non-steroidal, so the limited human safety data accumulated for other SARMs provides no read-across, leaving it with the thinnest evidence base of any compound in this index.
key published findings
- In vitro (Kanno et al., Biological & Pharmaceutical Bulletin, 2011): YK-11 was characterised as a partial agonist of the androgen receptor that does not induce the AR N/C terminal interaction required for full activation.
- In vitro (Kanno et al., Biological & Pharmaceutical Bulletin, 2013): YK-11 regulated myogenic differentiation of C2C12 mouse myoblasts through induction of follistatin expression, the finding underlying its description as a myostatin inhibitor.
- In vitro: YK-11 demonstrated anabolic activity in C2C12 myoblasts reported as greater than that of dihydrotestosterone, a cell-culture potency comparison with no established human correlate.
- Rodent: YK-11 has been investigated as a potential treatment for sepsis-induced muscle wasting in animal studies.
- Human: no clinical trial of YK-11 of any phase has been published; there is no human pharmacokinetic, endocrine or hepatic safety dataset, and the compound is documented in forensic literature as a novel designer drug rather than an investigational medicine.
limitations of the evidence
- There is no human data of any kind, so no statement about efficacy, dosing, exposure duration or safety in people can be evidence-based.
- The core mechanistic literature rests on a small number of in vitro papers from a single research group, without independent replication in the accessible record.
- Because YK-11 is steroidal rather than non-steroidal, safety inferences from the better-studied SARMs are not transferable, and its hepatic metabolism is uncharacterised.
documented safety signals
- Drug-induced liver injury: YK-11 is specifically named among the SARMs discussed in the NIH LiverTox chapter, which assigns the class a likelihood score of B — a likely cause of clinically apparent liver injury.
- The class hepatotoxicity phenotype is cholestatic jaundice with bilirubin often peaking above 30 mg/dL against only 2–5 × ULN ALT and near-normal alkaline phosphatase, latency typically 2–3 months, with occasional reversible renal dysfunction requiring temporary dialysis.
- The steroidal structure raises hepatotoxicity concerns distinct from the non-steroidal SARMs, and no human hepatic safety data exists to characterise them.
- As an AR-active compound it is expected to suppress the hypothalamic-pituitary-gonadal axis, but there is no human endocrine dataset to quantify the magnitude, threshold or reversibility of that suppression.
- Health Canada has warned that SARMs are not authorised for any use in Canada and can pose serious health risks including heart attack, stroke and liver damage, with unknown long-term effects.
- FDA public safety notification on SARM-containing bodybuilding products names heart attack, stroke, psychosis and hallucinations, sleep disturbance, sexual dysfunction, liver injury and acute liver failure, infertility, miscarriage and testicular shrinkage.
- The complete absence of human pharmacokinetic data means exposure accumulation and washout are unpredictable, and there is no basis for recognising or managing an adverse reaction.
- As a designer compound outside any regulated supply chain, product identity and purity are unverified, and analytical findings in this market routinely reveal misidentified or adulterated contents.
identity
| full name | YK-11 (myostine) |
| category | Anabolic & Receptor |
| modality | small molecule |
| formula | C25H34O6 |
| molar mass | 430.5 g/mol |
| cas | 1370003-76-1 |
laboratory handling
| storage | Reference material: store as a solid, desiccated and protected from light, at -20 °C for long-term stability; stock solutions typically stored at -80 °C with freeze-thaw cycles minimised. |
| solubility | Lipophilic steroidal small molecule; soluble in DMSO and ethanol, essentially insoluble in water. Lot-specific solubility should be taken from the certificate of analysis. |
Handling information describes laboratory practice for a research reagent. It is not a preparation guide for use in humans.
the receipts
5 citedLiverTox: Clinical and Research Information on Drug-Induced Liver Injury, NIDDK/NIH · 2024 · official
U.S. Food and Drug Administration · 2025 · official
Biological & Pharmaceutical Bulletin · 2013 · preclinical
Biological & Pharmaceutical Bulletin · 2011 · preclinical
Wikipedia (secondary compilation of primary sources) · 2025 · reviews
others in Anabolic & Receptor