YK-11 is an unusual SARM developed in Japan that, unlike most SARMs, retains a steroid-like backbone (modified androstane). In cell-culture studies it acts as a partial androgen receptor agonist and was reported to induce follistatin, a protein that blocks myostatin (the muscle-growth brake). The combination, in theory, would drive both androgen-receptor and myostatin-pathway muscle growth. The follistatin data come almost entirely from a single Japanese laboratory and have not been independently replicated in vivo. There are no human trials, no pharmacokinetic data, and persistent reports of liver-enzyme elevation in users. Treat the muscle-growth claims as hypothesis, not established fact. Not stocked by Kodiac. This monograph is provided for research and educational reference.
Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.
SARM with myostatin-related activity
A non-steroidal SARM with reported follistatin-inducing and myostatin-modulating activity beyond AR agonism.
Abstract
YK-11 (17-alpha,20E-(((((4-methoxyphenyl)sulfonyl)methylene)-bisoxy))-17-beta-(methoxycarbonyl)methyl-androst-1,4-dien-3-one; molecular formula C25H34O6; molecular weight 430.54) is a structurally novel SARM developed in Japan and described initially by the Yale-Kanno group at Toho University. Distinct from aryl propionamide SARMs by retaining a steroidal scaffold (modified androstane); the compound was reported as a tissue-selective AR partial agonist with concurrent induction of follistatin in C2C12 myoblast cultures, theoretically producing additive muscle hypertrophy through myostatin pathway inhibition. The follistatin-inducing claim is supported by a single research group and has not been independently replicated. No clinical trials. The compound is widely used recreationally as a high-potency SARM-class agent. Plasma half-life and pharmacokinetic data are sparse.
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