S-23 Capsules
10 mg per capsule of a nonsteroidal aryl-propionamide SARM, studied in rats as a hormonal male contraceptive. A small molecule, not a peptide. Each lot is tested in the manufacturer’s own laboratory.
| Compound | S-23, selective androgen receptor modulator |
|---|---|
| CAS number | 1010396-29-8 |
| Molecular formula | C18H13ClF4N2O3 |
| Contents | S-23: 10 mg per capsule |
| Form | Hard gelatin capsules containing the active substance blended with microcrystalline cellulose, packed in a sealed bottle |
| Storage, sealed | Store at room temperature (15–25 °C) in the tightly closed original container, dry and protected from light |
| Format | Capsules in a sealed bottle |
Sizes and lots
- 10 mg per capsule · 1 bottle — $58.99
- 10 mg per capsule · Kit of 10 — $524.42
S-23 is a nonsteroidal selective androgen receptor modulator (SARM) from the aryl-propionamide family, and a small molecule rather than a peptide. This listing is a bottle of hard gelatin capsules, each holding 10 mg of S-23 blended with microcrystalline cellulose. Nearly everything published on S-23 itself comes from one 2009 study in male rats, which tested it as part of a hormonal male contraceptive, so the research centres on the reproductive axis more than on any other tissue.
What is in each capsule
Each capsule holds 10 mg of S-23, about 2.5% of the capsule contents by weight, in a microcrystalline cellulose fill and a gelatin shell. The safety data sheet classifies S-23 as harmful if swallowed (H302), suspected of damaging fertility or the unborn child (H361) and liable to cause long-lasting harmful effects to aquatic life (H413). The last of these means unused capsules belong in chemical waste, handled as the sheet's disposal section describes. Store the bottle locked up, tightly closed at 15 to 25 °C, dry and protected from light.
What the research covers
The 2009 contraception study
Jones and colleagues characterised S-23 in male rats as a candidate for hormonal male contraception1. In vitro it bound the androgen receptor with an inhibitory constant of 1.7 nM and behaved as a full agonist1. In intact rats it suppressed luteinising hormone by more than half, with a smaller prostate and a larger levator ani muscle, the rodent muscle these studies use as a gauge of anabolic activity1. Paired with estradiol benzoate, which the rats needed to keep normal sexual behaviour, it suppressed LH and FSH and with them spermatogenesis1. In the main combination group, four of six animals had no sperm in the testis and none of six matings produced a pregnancy1. Fertility recovered fully once treatment stopped, with every mating producing a pregnancy after 100 days1. The same animals also showed higher bone mineral density and lean mass and lower fat mass1.
S-23 in the wider SARM literature
A 2007 review listed male contraception alongside osteoporosis, muscle wasting and diseases of the prostate as uses that SARMs might eventually serve2. That expectation has not turned into approved products: Christiansen and colleagues wrote in 2020 that no SARM had been approved by the FDA for any indication3.
What is not established
Frequently asked questions
Why was S-23 studied as a contraceptive?
Because in rats it suppressed LH and FSH, the pituitary hormones that drive sperm production, while acting as an androgen elsewhere. Combined with an estrogen it stopped sperm production in most treated animals, and fertility returned after treatment ended. All of that work was done in rats.
Is S-23 a peptide or a steroid?
Neither. It is a nonsteroidal small molecule, a propanamide that links a cyano- and trifluoromethyl-substituted phenyl ring to a chloro-fluorophenoxy group. It binds the androgen receptor but shares no structure with testosterone, and it contains no amino acids.
What does the safety data sheet say about S-23?
It lists three hazards: harmful if swallowed, suspected of harming fertility or the unborn child, and long-lasting harm to aquatic life. It asks for the bottle to be stored locked up, and unused material should go to chemical waste, not down a drain.
References
- Jones A, Chen J, Hwang DJ, et al. Preclinical characterization of a (S)-N-(4-cyano-3-trifluoromethyl-phenyl)-3-(3-fluoro, 4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide: a selective androgen receptor modulator for hormonal male contraception. Endocrinology. 2009;150(1):385-95. DOI · PubMed
- Gao W, Dalton JT. Expanding the therapeutic use of androgens via selective androgen receptor modulators (SARMs). Drug Discov Today. 2007;12(5-6):241-8. DOI · PubMed
- Christiansen AR, Lipshultz LI, Hotaling JM, et al. Selective androgen receptor modulators: the future of androgen therapy?. Transl Androl Urol. 2020;9(Suppl 2):S135-S148. DOI · PubMed
For laboratory research use only. Not for human or veterinary consumption. Products have not been evaluated by the U.S. Food and Drug Administration and are not intended to diagnose, treat, cure or prevent any disease.