LGD-3303 Research Standard

LGD-3303 (CAS 917891-35-1) is an orally available nonsteroidal quinolinone-class selective androgen receptor modulator, supplied as a reference standard for androgen receptor pharmacology. It carries the single most useful mechanistic result in this compound class: an experiment that rules out the obvious alternative explanation for tissue selectivity.^[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.

• Selectivity is receptor-level, not distribution-driven. The intuitive explanation for a tissue-selective drug is that it simply reaches one tissue more than another. LGD-3303 rules that out. It has potent activity on levator ani muscle but is a partial agonist on prostate and preputial gland — yet measured local tissue concentrations were higher in prostate than in levator ani. The selectivity survives despite the distribution working against it.^[1]

• Route-independent. The same tissue-selective profile held whether dosed orally or by continuous infusion, two routes with markedly different exposure-versus-time curves. So the effect is not an artefact of peak concentration or dosing rhythm.^[1]

• A ceiling on prostate response. LGD-3303 never stimulated ventral prostate above intact levels despite rising plasma concentrations — behaviour characteristic of partial agonism at that tissue rather than of insufficient exposure.^[1]

• 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.^[4]

• 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.^[5]

Research Applications

Primary fields of in vitro and preclinical laboratory investigation include:

• PK/PD relationship studies pairing plasma and local tissue concentrations with functional endpoints.^[1]

• Partial-agonist characterisation across tissues in castrated-rodent models.^[1]

• In vitro metabolite identification — four phase I metabolites characterised in equine liver microsomes.^[2]

• Analytical and forensic method development. Reference material for chromatography-mass spectrometry identification, retention-time matching and metabolite characterisation.^[3]

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.