S-23

S-23 (Mastorin) Research Standard

S-23 (Mastorin) is a synthetic nonsteroidal selective androgen receptor modulator (SARM) belonging to the arylpropionamide chemical class. Originally developed for its potential as a male hormonal contraceptive, S-23 is distinguished by its high-affinity binding to the androgen receptor (AR) ligand-binding domain. In laboratory research, it serves as a robust tool for investigating tissue-differential androgen receptor pharmacology, the suppression of spermatogenesis, and the signaling pathways regulating bone mineral density and body composition.

Technical Specifications

Mechanism of Action & Research Context

S-23 acts as a high-affinity ligand for the androgen receptor (AR). Its research value is largely driven by its tissue-selective transcriptional activity.

• AR Binding Dynamics: With a binding affinity of $K_i approx 1.7 text{ nM}$, S-23 is one of the more potent arylpropionamide ligands currently characterized. It facilitates a conformational shift in the receptor that leads to selective downstream gene activation.

• Tissue-Differential Signaling: In preclinical models, S-23 exhibits varying agonist activity across different tissues. This profile is frequently studied to understand how AR ligands can be engineered to exert anabolic effects in muscle and bone while limiting activity in other tissues, such as the prostate.

• Reproductive Endocrinology: The compound is a benchmark for studying the negative feedback loops of the hypothalamic-pituitary-gonadal axis, specifically regarding the dose-dependent suppression of spermatogenesis in in vivo and ex vivo models.

Research Applications

S-23 is a specialized reagent used to explore AR-mediated signaling and analytical detection protocols.

Primary fields of in vitro laboratory investigation include:

• Reproductive Endocrinology: Modeling the suppression of spermatogenesis and studying the kinetics of hormonal recovery post-exposure.

• Androgen Receptor Pharmacology: Utilizing competitive binding and transactivation assays (e.g., CV-1 reporter systems) to map ligand-receptor interactions.

• Bone & Body Composition Research: Investigating the impact of high-affinity AR ligands on bone mineral density and anabolic signaling pathways.

• Analytical & Forensic Toxicology: Developing sensitive LC-MS/MS methods for the identification of urinary metabolites, supporting anti-doping forensic research.

• Structure-Activity Relationship (SAR) Studies: Comparing the activity of the 4-chloro-3-fluorophenoxy substitution pattern against other arylpropionamides like MK-2866.

Storage & Handling Guidelines

To maintain the chemical stability and experimental reliability of the compound:

• Long-Term Storage: Store in a dry, cool environment. Maintain at -20 °C for extended stability.

• Light Sensitivity: Protect strictly from direct light to prevent the degradation of the arylpropionamide scaffold.

• Environmental Control: Keep the container tightly sealed to prevent moisture ingress.

• Aseptic Technique: Use clean, non-reactive laboratory tools to prevent cross-contamination during weighing and solution preparation.

Regulatory & Research Note

S-23 is included on the World Anti-Doping Agency (WADA) Prohibited List. In the context of analytical chemistry research, it is treated as a high-priority analyte due to its increasing prevalence in anti-doping forensic studies. It is not approved for any human, veterinary, or clinical use, and all research must be conducted in compliance with applicable institutional and legal standards.

Research Use Disclaimer

Research Use Only Disclaimer: This product is developed and distributed strictly as a Research Use Only (RUO) laboratory reference chemical intended exclusively for non-clinical analytical and scientific investigation. It is not an FDA-approved drug, medical treatment, dietary supplement, or food ingredient, and is strictly prohibited for human or animal consumption. Kimera Chems supplies this high-purity research material solely to qualified institutions and professional investigators for authorized laboratory research.