# YK-11

> Steroidal partial androgen-receptor agonist studied in myostatin-related research

All products are sold strictly for laboratory research use only. Not for human or veterinary use.

- Web page: https://peptidemedixeu.com/en/products/yk-11/
- Brand: Peptide Medix EU
- Category: [SARMs](https://peptidemedixeu.com/en/collections/sarms/)
- Purity: ≥98% by HPLC; lot-matched COA available
- CAS number: 1370003-76-1
- from €55 (EUR)

## Sizes and prices (EUR)

| Size | Price | SKU |
| --- | --- | --- |
| 10 mg · 60 capsules | €55 | YK-11-10-MG-60-CAPSULES |
| 30 mL liquid · 20 mg/mL | €68 | YK-11-30-ML-LIQUID-20-MG-ML |

_Catalog prices at build time; the web page and checkout are authoritative._

## Specifications

- **CAS number:** 1370003-76-1
- **Molecular formula:** C25H34O6
- **Molecular weight:** 430.54 g/mol
- **Form:** Oral capsules in a sealed bottle, or research liquid in a dropper bottle
- **Purity:** ≥98% by HPLC; lot-matched COA available
- **Solubility:** Poorly water soluble; DMSO or ethanol used for concentrated stocks
- **Available options:** 10 mg × 60 capsules; 30 mL liquid at 20 mg/mL
- **Compound class:** Steroidal selective androgen receptor modulator (partial agonist)
- **Core structure:** 5α-androstane nucleus with a gem-dimethyl malonate ester at C-17
- **Molecular target:** Androgen receptor; downstream follistatin expression studied in myotubes
- **Research areas:** Androgen receptor partial agonism, follistatin and myostatin signalling, myotube differentiation
- **Storage (capsules and solid):** Room temperature, sealed with desiccant, away from light, heat and humidity
- **Storage (research liquid):** Cool and dark, closure tight; refrigerate for extended study windows
- **Regulatory status:** Not an approved drug; not a lawful dietary ingredient in the US; prohibited by WADA

## Description

YK-11 is a synthetic research compound usually filed with the SARMs, yet it differs from the rest of that group in one key respect: it has a steroid structure. Its framework is a 5α-androstane skeleton derived from dihydrotestosterone, carrying a gem-dimethyl malonate ester at C-17 (C25H34O6, 430.54 g/mol, CAS 1370003-76-1). Compounds like RAD-140 or LGD-4033, by contrast, contain no steroid nucleus whatsoever.

Yuichiro Kanno and co-workers in Japan first described it around 2011, characterising it as a partial agonist of the androgen receptor. The findings that attracted most interest followed soon after: cultured C2C12 myotubes treated with the compound reportedly produced more follistatin, a natural antagonist of myostatin. This single strand of cell-culture evidence is where the common description of YK-11 as a “myostatin inhibitor” comes from — a label that the published data support only loosely and only in vitro.

We offer YK-11 as 10 mg capsules in bottles of 60 and as a 30 mL research liquid at 20 mg/mL, HPLC-tested to ≥98% with a certificate of analysis for each lot. It is not an approved medicine anywhere, may not be sold as a food supplement in the EU or as a dietary ingredient in the United States, and is supplied strictly for laboratory research.

## Frequently asked questions

### Should YK-11 really be called a SARM?

It is marketed and discussed as one, but chemically it is a steroid — a dihydrotestosterone derivative with a gem-dimethyl malonate ester at C-17 — whereas RAD-140 and LGD-4033 lack any steroid nucleus. “Steroidal partial androgen-receptor agonist” describes it more accurately.

### Is YK-11 a myostatin inhibitor?

Not directly, based on published evidence. Studies in C2C12 myotubes reported higher expression of follistatin, a natural myostatin antagonist — an indirect, in-vitro observation that is the only basis for the myostatin-inhibitor label usually attached to it.

### What does “partial agonist” mean for YK-11?

It binds the androgen receptor but triggers a smaller maximum transcriptional response than a full agonist such as DHT. Where a full agonist is already present, a partial agonist can compete for the binding pocket and lower the overall signal — so the direction of the observed effect depends on context.

### How is purity confirmed, and is there a COA?

HPLC analysis to ≥98% with identity checked against the expected 430.54 g/mol, for every lot. The certificate matching the lot number on your bottle can be requested at any time before or after purchase.

### Capsules or liquid — which suits my study?

Capsules give a fixed 10 mg unit with no preparation, ideal for repeated-unit protocols. The 30 mL liquid at 20 mg/mL is easier when amounts vary or dilution into a vehicle is needed, since you measure volume directly instead of opening several capsules.

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All products offered on this website are intended solely for in-vitro laboratory research and development by qualified professionals. They are not drugs, foods, cosmetics or dietary supplements, and are not intended to diagnose, treat, cure or prevent any disease. Products must not be introduced into humans or animals in any manner. By purchasing, you confirm that you are a qualified researcher and accept full responsibility for handling and storage in accordance with applicable laws.

Peptide Medix EU · https://peptidemedixeu.com/en/products/yk-11/