S23 has emerged as one of the most potent selective androgen receptor modulators (SARMs) studied to date. Originally developed by GTX Inc., this nonsteroidal compound demonstrates exceptionally high androgen receptor binding affinity — surpassing many other SARMs currently under investigation. For researchers studying body composition, androgen pharmacology, and male reproductive biology, S23 represents a compound of significant scientific interest.
What Is S23?
S23 (chemical name: (2S)-3-(4-chloro-3-fluorophenyl)-2-[3-(trifluoromethyl)-4-nitrophenoxy]propanoic acid) is a nonsteroidal SARM with full agonist activity at the androgen receptor. It was developed as part of GTX’s SARM research program and has been investigated in preclinical models for both anabolic applications and male hormonal contraception. Unlike earlier-generation SARMs, S23 exhibits near-complete suppression of endogenous testosterone when administered at higher doses, making it unique among compounds in this class.
The injectable S23 50mg/mL formulation studied at combatresearch.is provides researchers with a concentrated, bioavailable preparation suited for subcutaneous administration protocols.
Research Overview
Peer-reviewed research on S23 remains primarily preclinical, conducted in rodent models. The foundational GTX studies published in Endocrinology and the Journal of Medicinal Chemistry established its pharmacodynamic profile:
- Jones et al. (2009) — Demonstrated S23’s high AR binding affinity (Ki = 1.7 nM) and tissue selectivity in castrated rat models. PubMed
- Yin et al. (2003) — Original characterization of S23 as a full AR agonist with selective anabolic activity. Google Scholar
- Male contraceptive studies — Research published in Journal of Clinical Endocrinology & Metabolism examined S23’s ability to suppress gonadotropins (LH/FSH) and reduce sperm production as a reversible male contraceptive candidate. PubMed
Community discussion of S23 research protocols can be found on r/PeptideScience and r/sarmssourcetalk, where researchers share observations from ongoing investigations.
Potential Benefits Studied in Preclinical Research
- Increased lean muscle mass — Rodent models consistently show statistically significant lean mass gains at doses of 0.1–1 mg/kg/day
- Decreased fat mass — Studies note concurrent fat reduction alongside lean mass accretion, suggesting favorable body composition changes
- Bone mineral density — S23 has demonstrated androgenic effects on bone tissue, with potential applications in osteoporosis research
- Male hormonal contraception — At higher doses, S23 suppresses LH and FSH to near-zero, dramatically reducing sperm count in a reversible manner
- Muscle preservation during caloric deficit — Preliminary data suggests anti-catabolic properties that may be relevant to cachexia research
- Prostate-sparing profile — Unlike testosterone, S23 demonstrates tissue selectivity with reduced stimulation of prostate tissue in rat models
Dosage & Administration
Preclinical research has employed a range of doses depending on the endpoint studied. In rodent models, anabolic effects have been observed at 0.1–1 mg/kg/day administered subcutaneously, while contraceptive suppression required doses in the 0.5–3 mg/kg/day range.
The injectable S23 50mg/mL formulation allows for precise volume-based dosing in research settings. Subcutaneous administration is the standard route used in published preclinical protocols. Given S23’s reported half-life of approximately 12 hours, twice-daily administration has been used in some research designs to maintain more consistent plasma levels.
Researchers should note that S23 is significantly more suppressive of the hypothalamic-pituitary-gonadal (HPG) axis than other SARMs such as Ostarine or LGD-4033. Post-cycle recovery of endogenous testosterone in rodent models was observed but required time.
Where to Find S23 50MG/ML for Research
Researchers sourcing S23 for laboratory investigation can find the injectable 50mg/mL formulation at combatresearch.is. Combat Research supplies research-grade compounds with third-party verification for use in legitimate research settings.
Conclusion
S23 stands out in the SARM landscape due to its exceptional AR binding affinity, potent anabolic effects in preclinical models, and its dual investigation as both a performance-relevant compound and a male hormonal contraceptive candidate. As research in selective androgen receptor modulation continues to advance, S23’s unique pharmacological profile makes it a compelling subject for researchers studying body composition, reproductive endocrinology, and androgen pharmacology.
Disclaimer
This article is intended for educational and research purposes only. S23 is not approved by the FDA for human use. All information presented here is derived from preclinical research and should not be interpreted as medical advice. Combat Research compounds are sold strictly for laboratory and research use.
