YK-11 is sold as a SARM but works differently from the rest of the class: it is studied in early cell-based research as a partial androgen-receptor agonist that also appears to inhibit myostatin, a natural brake on muscle growth. Human data is essentially nonexistent.
Animal/cell data only
YK-11 is a synthetic steroidal SARM, mechanistically distinct from other SARMs in this batch: it's reported to inhibit myostatin (a negative regulator of muscle growth) by inducing follistatin expression.
C2C12 mouse myoblast cell study: YK-11 (but not DHT) induced follistatin expression, and this follistatin induction was shown to be responsible for YK-11's myogenic (muscle-differentiation) effect — blocking follistatin with an antibody reversed the effect. Kanno et al., Biol Pharm Bull, 2013 This is cell-culture data, not even a whole-animal study, and there is no human trial.
Is YK-11 a true SARM?+
It is marketed as one, but its proposed myostatin-inhibiting activity is mechanistically distinct from the receptor-selective mechanism that defines most SARMs.
Is YK-11 FDA-approved?+
No, and it has no published human trial data — the available research is limited to cell-culture (in-vitro) studies.
Is YK-11 banned in sport?+
Yes, it is treated as an anabolic agent under WADA's S1.2 class-wide prohibition.
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