YK-11

YK-11 is a synthetic, steroidal selective androgen receptor modulator (SARM) structurally derived from dihydrotestosterone (DHT). It is currently classified as an experimental compound and has not been approved for medical use in humans. Despite this, it has been widely researched in preclinical settings for its potent anabolic effects on muscle cells.

YK-11

Clinical data
Other names	Myostine; YK-11; 17α-methyl-δ2-17β-hydroxyestra-4,9-dien-3-one
Identifiers
IUPAC name Methyl (2E)-2-[(8R,9S,10R,13S,14S,17S)-2'-methoxy-2',13-dimethyl-3-oxospiro[1,2,6,7,8,9,10,11,12,14,15,16-dodecahydrocyclopenta[a]phenanthrene-17,5'-1,3-dioxolane]-4'-ylidene]acetate
CAS Number	1370003-76-1
PubChem CID	119058028
ChemSpider	52085570
UNII	Z9748J6B0R
CompTox Dashboard (EPA)	DTXSID301107018
Chemical and physical data
Formula	C25H34O6
Molar mass	430.541 g·mol−1
3D model (JSmol)	Interactive image
SMILES C[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@@]24/C(=C\C(=O)OC)/OC(O4)(C)OC)CCC5=CC(=O)CC[C@H]35
InChI InChI=1S/C25H34O6/c1-23-11-9-18-17-8-6-16(26)13-15(17)5-7-19(18)20(23)10-12-25(23)21(14-22(27)28-3)30-24(2,29-4)31-25/h13-14,17-20H,5-12H2,1-4H3/b21-14+/t17-,18+,19+,20-,23-,24?,25+/m0/s1 Key:KCQHQCDHFVGNMK-PQUNLUOYSA-N

Overview

YK-11 is distinct among SARMs due to its steroidal structure, setting it apart from most non-steroidal SARMs like Ostarine or LGD-4033. It binds to the androgen receptor (AR), similar to anabolic steroids, but its downstream activity differs significantly.

Mechanism of action

YK-11 functions as a partial agonist of the androgen receptor. It activates the receptor but not to the full extent like natural androgens such as testosterone or DHT. It does not promote the typical N/C-terminal interaction within the AR, which is required for full transcriptional activation.^[1]

Instead, YK-11 induces muscle growth through a secondary mechanism: it significantly increases the expression of follistatin, a potent inhibitor of myostatin—a protein that suppresses muscle growth.^[2]

In vitro and animal studies

Laboratory studies on mouse and human myoblasts (muscle precursor cells) have shown that:

• YK-11 increases muscle cell differentiation and growth more potently than DHT.^[2]
• It exhibits strong anabolic activity without stimulating androgenic effects on non-muscle tissue (though this has only been evaluated in vitro so far).
• In animal models, it has demonstrated protective effects against muscle wasting due to sepsis, suggesting potential therapeutic uses.^[3]

See also

• Selective androgen receptor modulators
• Myostatin inhibitors
• Ostarine
• LGD-4033
• MK-4541
• S42 (selective androgen receptor modulator)