R406 free base (R406 (free base)) is a potent Syk inhibitor.

Syk:41 nM

In-vitro Fluorescence Polarization Kinase Assays: R406 is serially diluted in DMSO and then diluted to 1% DMSO in kinase buffer (20 mM HEPES, pH 7.4, 5 mM MgCl2, 2 mM MnCl2, 1 mM DTT, 0.1 mg/mL acetylated BGG). ATP and substrate in kinase buffer are added at room temperature, resulting in a final DMSO concentration on 0.2%. The kinase reactions are performed in a final volume of 20 μL containing 5 μM HS1 peptide substrate and 4 μM ATP and started by addition of 0.125 ng of Syk in kinase buffer. The reaction is allowed to proceed for 40 minutes at room temperature. The reaction is stopped by the addition of 20 μL of PTK quench mix containing EDTA/anti-phosphotyrosine antibody (1X final)/fluorescent phosphopeptide tracer (0.5X final) diluted in FP Dilution Buffer. The plate is incubated for 30 minutes in the dark at room temperature and then read on a Polarion fluorescence polarization plate reader. Data are converted to amount of phosphopeptide present using a calibration curve generated by competition with the phosphopeptide competitor provided in the Tyrosine Kinase Assay Kit. For IC50 determination, R406 is tested at eleven concentrations in duplicate and curve-fitting is performed by non-linear regression analysis using Prism GraphPad Software.

DLBCL cell lines are treated with serial dilutions of R406 (0.3, 0.6, 1.25, 2.5, or 5 μM) for 72 or 96 hours. Thereafter, cellular proliferation is determined by MTT assay, and cell apoptosis is assessed by using annexin V–FITC/propidium iodide (PI) staining. For the determination of caspase 9, 8, and 3, cells are lysed, size-fractionated by polyacrylamide gel electrophoresis (PAGE), and immunoblotted. (Only for Reference)

R406 (free base)

H2O: < 1 mg/mL (insoluble or slightly soluble)

DMSO: 38.5 mg/mL (81.84 mM), Sonication is recommended.

Ethanol: < 1 mg/mL (insoluble or slightly soluble)