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S-23 — high-potency selective androgen receptor modulator (SARM), studied preclinically as a male contraceptive candidate
A high-potency oral SARM with ZERO human efficacy data — its only published animal work was as a reversible male contraceptive in rats, where it built muscle and bone while shutting down the HPTA and suppressing sperm to infertility. Sold grey-market for body composition, products may have unreliable identity, strength or quality, and it is banned by WADA. The human literature is limited to anti-doping detection, not benefit. It is described here to inform, not to recommend.
Research compound — not a dietary supplement
S-23 is a research compound, not a regulated dietary supplement. It is sold for research or off-label use. The evidence below is largely preclinical (animal and in-vitro) or early-stage, so no evidence score is assigned. This page is provided for transparency and education — it is not a recommendation to use. Consult a qualified healthcare provider, and be aware that purity, dosing, and legal status vary by jurisdiction.
What the evidence says
Most S-23 studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality studies published 2009–2025.
Based on 5 studies
Confidence
Low confidenceBy outcome
A high-potency, full-agonist SARM whose ONLY published efficacy evidence is a single rat study where it was developed as a reversible male contraceptive — building muscle and bone while suppressing LH/FSH and spermatogenesis to infertility. There is zero human efficacy or safety data; the human literature is limited to anti-doping detection. Products come from an unregulated grey market and may have unreliable identity, strength or quality, and S-23 is WADA-banned. Very low score: an interesting androgen pharmacology story with no human evidence and a body-composition use that is inseparable from full reproductive shutdown.
3 trials ongoing or recruiting · none completed on ClinicalTrials.gov
Registered trials show research momentum for S-23, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Nov 2026
S-23 ((2S)-N-(4-cyano-3-trifluoromethylphenyl)-3-(3-fluoro-4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide) is an arylpropionamide-derived selective androgen receptor modulator (SARM) — the same chemical family as ostarine and andarine.
It is notable for being unusually potent: in the foundational preclinical work (Jones, Chen, Hwang, Miller, Dalton, Endocrinology 2009) it bound the androgen receptor with high affinity (Ki ≈ 1.7 nM) and acted as a FULL agonist, more like testosterone than the partial-agonist SARMs.
Critically, S-23 was developed and studied as a candidate hormonal MALE CONTRACEPTIVE, not a muscle-building drug.
In intact male rats it suppressed LH and FSH, shrank the prostate, increased levator ani (muscle) mass, raised bone mineral density and lean mass, and reduced fat — but combined with estradiol benzoate it suppressed spermatogenesis to the point of azoospermia and zero pregnancies in mating trials.
That infertility was fully reversible after withdrawal. This is the honest, load-bearing framing: the single piece of efficacy evidence for S-23 is an animal contraception study whose 'benefits' (lean mass, bone) are inseparable from full shutdown of the reproductive axis.
There has never been a human efficacy or safety trial of S-23. S-23 has been on the World Anti-Doping Agency prohibited list for years and was responsible for multiple adverse analytical findings in athletes.
It is sold online as an unregulated 'research chemical' for body composition; an analysis of products sold to UK consumers as SARMs (Leaney 2021) found products with no active ingredient, products with undeclared prohibited substances, and measured amounts that differed from the label.
The score is very low: a high-potency androgen with promising rodent body-composition signals that are entirely entangled with reproductive shutdown, no human efficacy or safety data, a grey-market mislabeled supply chain, and a WADA ban.
S-23 binds the androgen receptor with high affinity (Ki ~1.7 nM in vitro) and acts as a full agonist — closer to testosterone than the partial-agonist SARMs. In castrated and intact male rats this drove tissue-selective anabolic effects (levator ani muscle, bone) at low doses. Demonstrated only in rat and in-vitro systems; no human pharmacodynamic data.
By agonizing the androgen receptor, S-23 suppressed pituitary LH and FSH in male rats, the same negative-feedback mechanism exploited deliberately to make it a male contraceptive. This suppression is why it shrank the prostate and, with estradiol, halted spermatogenesis. Established in rats; the magnitude and reversibility in humans are unstudied.
Combined with estradiol benzoate, S-23 suppressed sperm production to azoospermia in most treated male rats, producing zero pregnancies in mating trials — fully reversible after withdrawal. This is the central published 'efficacy' result for S-23, and it is a fertility-suppression effect, not a performance benefit. Rat-only; never tested in humans.
How S-23 works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Avoid — there are no human trials. The rodent evidence (for a contraceptive) does not justify human self-experimentation.
Avoid — S-23 was designed to suppress sperm production; fertility effects in humans are unstudied.
Avoid — S-23 is WADA-banned and detectable in urine for weeks after a single dose.
Contraindicated — an androgen; entirely unstudied and unsafe in pregnancy.
Stacking androgens compounds HPTA suppression and androgenic load. No human interaction data exist; combined SARM/steroid use is unstudied and the toxicity of stacks is unknown.
There are no human drug-interaction data of any kind. As a hepatically metabolized androgen-receptor agonist, interactions cannot be predicted from the available animal and detection studies.
Tip: S-23 suppressed LH/FSH and spermatogenesis to infertility in rats. In humans the magnitude, time-course, and reversibility are unstudied — there is no way to make this safe.
Tip: As a full androgen-receptor agonist, S-23 is expected to exert androgenic effects; reviews note SARM abuse may raise cardiovascular risk. No human safety characterization exists.
Tip: Grey-market SARM products frequently contain the wrong compound, wrong dose, or undeclared analytes. Identity, purity, and sterility are not guaranteed.
S-23 has an evidence score of 3/10 — emerging evidence based on 5 indexed studies. A high-potency oral SARM with ZERO human efficacy data — its only published animal work was as a reversible male contraceptive in rats, where it built muscle and bone while shutting down the HPTA and suppressing sperm to infertility. Sold grey-market for body composition, products may have unreliable identity, strength or quality, and it is banned by WADA. The human literature is limited to anti-doping detection, not benefit. It is described here to inform, not to recommend. Representative study: PMID 18772237.
Dosing for S-23: No recommended dose — S-23 is a grey-market research chemical with no human efficacy or safety data and no quality control. We do NOT provide a dosing protocol. The only systematic dosing is in rats (sub-milligram per day, by the route used in those studies), and it was studied to SUPPRESS fertility. Human anti-doping studies have given microgram-to-low-milligram single or repeated oral doses purely to characterize detection, not to establish a safe or effective dose.
Timing is flexible for S-23 — consistent daily use matters more than the time of day. There is no validated human dosing schedule because the compound has never been tested for efficacy or safety in humans.
No consumer dose of S-23 is endorsed, so there is no dose at which it can be called safe. Talk to a healthcare provider before taking it. Reported side effects include animal reproductive suppression, androgenic effects (prostate, lipids, virilization), harm from an unregulated, mislabeled product. How often they occur is not established for all of them. Use caution if any of these apply to you: Grey-market research chemical; do not self-source; No human efficacy or safety data exists — every safety conclusion would be an extrapolation from rats; Anyone trying to conceive or preserve fertility — S-23 was developed to suppress spermatogenesis.
Caffeine
Probably helpsBlocks adenosine receptors to boost alertness, reaction time, and endurance — an umbrella review of 21 meta-analyses found it ergogenic for endurance, strength and power.
CoQ10
Likely helpsA lipid-soluble antioxidant central to mitochondrial energy production, with the strongest trial support for fertility/IVF outcomes and heart failure.
Sodium Bicarbonate
Likely helpsErgogenic aid that buffers metabolic acid. An umbrella review of meta-analyses found it improves peak anaerobic power and efforts lasting about 45 seconds to 8 minutes, on moderate to low quality evidence.
Alpha-GPC
Too few graded studiesA choline source that crosses the blood-brain barrier. Trials show cognitive gains in people with dementia or after stroke. In healthy adults the data are a few small, short studies.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 5 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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