Belumosudil (Rezurock) is an orally available, and specific ROCK2 inhibitor (IC50/Ki: 60/41 nM).

ROCK2:41 nM(Ki), ROCK2:60 nM

Belumosudil down-regulates the IL-17 and IL-21 secretion in human PBMCs, and leads to down-regulation of STAT3 phosphorylation, IRF4, and RORγt expression in CD4+ T cells. [2] Belumosudil inhibits the secretion of IL-21, IL-17, and IFNγ along with decreasing phosphorylated STAT3 and reduced protein expression of IRF4 and BCL6 in human peripheral blood mononuclear cells. [3]

In mice, Belumosudil (200 mg/kg, p.o.) inhibits ROCK activity in brain and heart, as measured by the degree of MYPT1 phosphorylation. Belumosudil (200 mg/kg, p.o.) significantly reduces the area of perfusion defect, and reduces tissue loss in the ipsilateral hemisphere. [1] In a collagen-induced arthritis (CIA) mouse model, Belumosudil (200 mg/kg, i.p.) downregulates the progression of collagen-induced arthritis via targeting of the Th17-mediated pathway. [2] Belumosudil ()150 mg/kg, i.p. or p.o.) effectively ameliorates cGVHD in a full MHC-mismatch model of multi-organ system cGVHD with bronchiolitis obliterans syndrome and a minor MHC-mismatch model of sclerodermatous GVHD. [3]

Cell-free enzyme assays are performed to determine the selective inhibition of ROCK1 and ROCK2 by SLx-2119. Reactions are performed on non-binding surface microplates. Four mU of human ROCK1 and ROCK2 are used to phosphorylate 30 μM of the synthetic ROCK peptide substrate S6 Long, prepared at American Peptide with the addition of 10 μM ATP, containing?33P-ATP in the presence of 10 mM Mg2+, 50 mM Tris, pH 7.5, 0.1 mM EGTA and 1 mM DTT at room temperature. One unit is the amount of kinase needed to catalyze the transfer of 1 nmol phosphate/min to the peptide. The reactions are allowed to proceed for 45 minutes and then stopped with 3% phosphoric acid to a final concentration of 1%. The reactions are captured on phospho cellulose filtration microplates and washed with 75 mM phosphoric acid and methanol using a vacuum manifold. Phosphorylation is measured on a Perkin-Elmer MicroBeta 1450.

SLx-2119 is dissolved in DMSO to obtain a stock solution of 20 mM. Western blots are used to determine whether HMVEC, NHDF and PASMC express ROCK1 and ROCK2. The cells are incubated for 24 hours in 3 mL culture media containing SLx-2119. All cells are collected at passage 3 and lysed on ice in 25 mM Tris-HCl pH 7.5, 150 mM NaCl, 0.5% tritonX-100, 10% glycerol, 10 mM NaF and a protease inhibitor cocktail. Protein concentration is determined using a BCA protein assay reagent. Cell lysates (35 μg) are separated on 7.5% or 12.5% SDS-PAGE polyacrylamide gels and transferred to PVDF membrane filters. Membranes are blocked in 5% non-fat milk in TBS containing 0.1% Tween 20. Blots are probed with antibodies to ROCK1, ROCK2 or actin and washed well before incubation with HRP-conjugated secondary antibodies and visualization with an enhanced chemiluminescence (ECL) kit.