KDC-MN-268 – Kodiac biolabs

Plain-language summaryIntrigue 52 / 100

S-23 is a SARM developed by GTx that stands out as a full androgen receptor agonist (rather than the partial agonism of most SARMs), producing the strongest hormonal suppression in the class. Preclinical studies showed reversible suppression of sperm production in male rodents, and S-23 was investigated as a candidate component of a male hormonal contraceptive when paired with a progestin. It also shows the typical SARM profile of muscle and bone activity with reduced prostate effect. No human clinical trials have been published, so almost everything known about safety in people comes from anecdote. WADA-banned. 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 Kodiac editorial, not peer-reviewed.

Our opinion on this compoundSingle-lab provenance

37/100

A preclinical-only full AR agonist SARM with a genuinely niche contraceptive angle but zero human signal

Look, S-23 is an interesting edge case in the SARM landscape, and we want to be precise about why it’s interesting before we explain why it doesn’t score very high. Most SARMs are partial AR agonists by design; partial agonism is the whole trick that lets them claim tissue selectivity without full androgenic load. S-23 breaks from that pattern. It’s a full agonist at the androgen receptor, which means its HPG suppression is substantially more aggressive than anything else in the class. That distinction matters. Researchers studying male hormonal contraception have been circling the idea of a combined SARM-plus-progestin regimen for over a decade, and S-23 became one of the more studied candidates for that specific use case in rodent models precisely because of how reliably it shuts down spermatogenesis.

The problem is the evidence base is almost entirely preclinical, and a large fraction of what exists originated from the GTx research pipeline or closely affiliated academic groups. Replication outside that orbit is limited. There are no published human clinical trials at this writing, which isn’t automatically disqualifying for a research compound, but it does mean the translational signal is essentially absent. You have a plausible mechanism and a real rodent phenotype. What you don’t have is any confirmation that the rodent pharmacology translates to human HPG dynamics in the way the contraceptive story requires.

The bench utility is real but narrow. If you’re running an androgen receptor biology program, S-23 is a legitimate probe for studying full vs. partial agonism at the AR, and the HPG suppression phenotype gives you a clean endpoint to work with in small animal models. Thats a specific utility and we don’t want to dismiss it. But it’s not a broadly indispensable tool the way rapamycin is for mTOR work. It’s a specialist instrument for a specific set of questions.

What we dont like: the recreational use context creates a messy signal-to-noise problem for serious investigators, the recovery profile post-exposure is the worst in class, and the compound sits in a regulatory gray zone that complicates institutional research approvals. The SARM class is also crowded enough that the full-agonist angle, while genuinely differentiating, hasn’t attracted the multi-lab attention it would need to build a real evidence stack. Honestly, S-23 would be a more compelling library entry if even one well-designed Phase 1 contraception trial had been completed. As it stands, it’s a preclinical compound with an interesting story and a thin dossier.

Novelty: 38
Mechanism promise: 42
In-category differentiation: 50
Evidence quality: 22
Translational signal: 18
Research bench value: 45

Rationale S-23 earns modest differentiation within the SARM class by being the only full AR agonist with a documented contraceptive research track record in rodents, but the complete absence of human clinical data and the likely narrow origination of most preclinical work (GTx-adjacent) keeps evidence and translational scores very low. The SARM class itself is mature enough that novelty is constrained even with the HPG-suppression angle.

Selective androgen receptor modulator

A non-steroidal SARM with reported male contraceptive activity in preclinical studies; full agonist at the AR with strong HPG suppression.

Abstract

S-23 (CAS 1010396-29-8; molecular formula C18H13ClF4N2O3; molecular weight 416.76) is a non-steroidal SARM developed by GTx. Distinct among SARMs as a full AR agonist (rather than a partial agonist), producing more pronounced HPG axis suppression alongside strong anabolic activity. Preclinical studies in male rodents demonstrated reversible spermatogenesis suppression; the compound was investigated as a candidate for male hormonal contraception via combined progestin and SARM regimen. Tissue-selective effects: full agonism in muscle and bone with reduced prostate activity relative to testosterone. The strong HPG suppression makes S-23 the most stringent SARM in terms of post-cycle endocrine recovery. No human clinical trials at this writing. Used recreationally despite the suppressive profile.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

Tag: KDC-MN-268

S-23

Abstract

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