LGD-3303

Chemical identity

LGD-3303 comes from the Ligand Pharmaceuticals programme that also produced LGD-2226 and, later, the compound now widely known as LGD-4033. It is built on a quinolinone core rather than the aryl-propionamide scaffold, placing it in a different chemical series from the SARMs most commonly encountered.

Unlike ACP-105, LGD-3303 behaves as a full agonist in muscle tissue in the published models while retaining partial-agonist character in prostate — a different route to the same dissociation goal.

Mechanism in research models

The compound binds the androgen receptor with high affinity and drives the canonical genomic pathway. Its distinguishing feature in the published work is behaviour in bone: rodent studies report increased bone mineral density and improved biomechanical strength in ovariectomised models, an endpoint where many SARMs perform less convincingly.

The reported anabolic-to-androgenic dissociation is substantial in rat assays, with levator ani response approaching that of testosterone at doses producing markedly less prostate weight gain.

Combination work with bisphosphonates has been published in osteoporosis models, examining whether an anabolic androgen signal and an antiresorptive agent produce additive effects on bone. That study design is the most distinctive part of this compound's literature.

What the literature establishes

The bone literature is the strongest element and is reasonably well documented in peer-reviewed journals from the originating programme era. Muscle endpoints are covered in the same body of work.

Development did not proceed to published human trials, and there is no clinical pharmacokinetic or safety data. Everything known about this compound comes from rodent studies.

LGD-3303 is prohibited in sport under WADA S1.2 and is included in anti-doping screening panels. It has been identified in analytical surveys of mislabelled consumer products, which is worth noting when assessing supply-chain claims.

Handling, storage and solubility

Solids of this class are typically held sealed at −20 °C, protected from light and moisture; the validated condition and the physical form are the ones stated on the lot documentation.

Insoluble in water; soluble in DMSO and ethanol. Prepare concentrated stocks in DMSO and dilute into assay buffer at the point of use. Vehicle-matched controls are essential.

Aliquot DMSO stocks to avoid repeated freeze–thaw and moisture uptake. Where a compound precipitates on dilution into aqueous medium, the effective concentration is not what the calculation says — inspect visually and consider a co-solvent or cyclodextrin approach.

Analytical documentation

Require HPLC purity, NMR and mass confirmation. The quinolinone scaffold has a distinctive aromatic region in the proton spectrum that makes NMR a straightforward identity check.

Because several structurally related Ligand-series compounds share close molecular weights, mass spectrometry alone is not sufficient to confirm which member of the series you have received.

References and authoritative sources

Chemical identity, regulatory status and anti-doping classification should be confirmed against primary sources rather than against this page. The records below are the ones to check first.

1. PubChem compound record (US National Library of Medicine)
2. PubMed indexed literature

These are database and regulatory sources. Citations to specific primary papers are being added to this page as part of ongoing scientific review; until they appear, treat the mechanism and literature sections above as a summary to verify rather than a citation of record.