S-4 (Andarine) Research Standard

S-4, also indexed as andarine (CAS 401900-40-1), is a nonsteroidal arylpropionamide selective androgen receptor modulator, supplied as a reference standard for androgen receptor pharmacology and analytical method development. It is one of the better-characterised compounds in the class on pharmacokinetics, which is what makes it a practical internal comparator.^[1]

Mechanism of Action & Research Context

The molecular target is the androgen receptor (AR, NR3C4), a ligand-activated nuclear hormone receptor that functions as a transcription factor.

• Characterised rodent pharmacokinetics. Across intravenous and oral dosing in rats, clearance ranged 1.0–2.1 mL/min/kg and varied with dose, volume of distribution was approximately 0.448 L/kg across all groups, and half-life fell between 2.6 and 5.3 h. Oral bioavailability was dose-dependent, complete at the lower doses.^[1]

• Defined metabolic routes. In liver S9 incubations the main routes for arylpropionamide SARMs are monohydroxylation, nitro-reduction, dephenylation and demethylation; in vivo these combine with glucuronidation, sulfation and carboxylation. The intact parent remains the principal analyte, which is why methods target it.^[2]

• Purity is a real-world problem for this compound. Material sold outside controlled supply has been analysed and found to carry roughly 10% of a single impurity from poor purification. That is the practical argument for working from a lot with its own COA rather than an unverified source.^[3]

• Distinct genomic and non-genomic routes. Nonsteroidal SARMs and endogenous androgens engage AR through different signalling arms and assemble different AR/cofactor complexes at androgen-responsive enhancers, so the two ligand types are not interchangeable in mechanistic work.^[5]

• Coregulator recruitment and dimerisation. A SARM can drive AR transcriptional activity while producing markedly less AR homodimerisation than DHT and recruiting only a restricted subset of cofactors, with p160 coactivators SRC1, TIF2 and NCoA3 notably absent in yeast two-hybrid assays. Differential coregulator recruitment is the leading mechanistic account of tissue selectivity.^[6]

Research Applications

Primary fields of in vitro and preclinical laboratory investigation include:

• Pharmacokinetic modelling using published clearance, volume and half-life values as a benchmark.^[1]

• Metabolite identification in S9 and microsomal incubations.^[2]

• Purity and impurity profiling by LC-HRMS against reference material.^[3]

• Analytical and forensic method development. Reference material for chromatography-mass spectrometry identification, retention-time matching and metabolite characterisation.^[4]

Analytical Documentation

Purity and identity vary by manufacturing lot. Kimera Chems does not publish a single fixed purity figure for this item; refer to the batch-specific Certificate of Analysis (COA) issued for the lot received, which reflects third-party analytical testing for that lot.

Storage & Handling

Store at controlled room temperature. Keep tightly closed. Liquid formats: do not refrigerate or freeze. Cold storage may cause the solution to cloud or precipitate. If this occurs, return to room temperature and mix until clear.

Storage guidance is a house recommendation. Analytical documentation is per-lot release testing.