Decernotinib (VRT-831509)(VX-509; VRT-831509) is a potent and selective Janus kinase 3 (JAK3) inhibitor with Ki of 2.5 nM; IC50 is 50-170 nM in cellular assays.

GSK-3β:1.8 μM (Ki), JAK1:11 nM (Ki), JAK2:13 nM (Ki), Tyk2:11 nM (Ki), CDK2-CyclinA:2.6 μM (Ki), PknB:8 μM, FLT3:1 μM (Ki), ROCK1:1.5 μM (Ki), JAK3:2.5 nM(Ki)

In HT-2 cells, Decernotinib inhibits IL-2–stimulated HT-2 STAT-5 phosphorylation, human T-cell blast proliferation, and CD40L/IL-4–induced B-cell proliferation. [1]

In a rat model of collagen-induced arthritis, Decernotinib(50 mg/kg, p.o.) results in dose-dependent reduction in ankle swelling and paw weight and improved paw histopathology scores. In a mouse model of oxazolone-induced delayed-type hypersensitivity, Decernotinib(50 mg/kg, p.o.) significantly suppresses ear edema. [1] In a rat HvG model, Decernotinib(50 mg/kg, p.o.) results in dose-dependent inhibition of popletial lymph node (PLN) hyperplasia. [2]

Kinase Activity Assays: The effect of VX-509 on JAK3 activity is assessed by measuring the residual kinase activity of the recombinantly expressed JAK3 kinase domain using a radiometric assay. The final concentrations of the components in the assay are as follows: 100 mM HEPES (pH 7.5), 10 mM MgCl2, 1 mM dithiothreitol (DTT), 0.01% BSA, 0.25 nM JAK3, 0.25 mg/ml polyE4Y, and 5 μM 33P-γ-ATP (200 μCi/μMol). A 10 mM stock solution of VX-509 is prepared in DMSO, from which additional dilutions are prepared. A substrate mixture (100 mM HEPES, 10 mM MgCl2, 0.5 mg/ml polyE4Y, and 10 μM 33P-γ-ATP) is added and mixed with VX-509 stock solution. The reaction is initiated by the addition of an enzyme mixture [100 mM HEPES (pH 7.5), 10 mM MgCl2, 2 mM DTT, 0.02% BSA, 0.5 nM JAK3]. After 15 minutes, the reaction was quenched with 20% trichloroacetic acid (TCA). The quenched reaction was transferred to the GF/B filter plates and washed three times with 5% TCA. Following the addition of Ultimate Gold scintillant (50 μl), the samples were counted in a Packard TopCount gamma counter (PerkinElmer). In this procedure, the radioactivity trapped is a measure of the residual JAK3 kinase activity. From the activity versus concentration of VX-509 titration curve, the Ki value was determined by fitting the data to an equation for competitive tight binding inhibition kinetics using Prism software.

Frozen purified human B cells atr thawed, washed, and resuspended in complete medium. Cells are plated onto a 96-well plate at a density of 2 × 105 cells/well. VX-509 is added, and plates are incubated for 30 minutes at 37°C, followed by stimulation with a combination of 10 ng/ml IL-4 and 1 μg/ml CD40L. DMSO alone is added to the top two rows, one of which is stimulated with IL-4 or CD40L (negative control) and the other of which served as a proliferation control. The plates are incubated at 37°C for 6 days. On day 6, cells are pulsed with [3H]thymidine for 7 hours and harvested onto filters for radioactive determination using a PerkinElmer-Wallace beta counter (1205 Betaplate Beta Liquid Scintillation Counter). Data are analyzed with Softmax pro software to generate an IC50 value.(Only for Reference)