NVP-BSK805 2HCl (1092499-93-8(free base)) (BSK 805)(IC50=0.5 nM), a specific and effective ATP-competitive JAK2 inhibitor, is more than 20-fold specificity over JAK1, JAK3 and TYK2.

NVP-BSK805 is found to potently inhibit JAK2, whereas displaying more than 20-fold selectivity towards JAK1, JAK3, and TYK2. NVP-BSK805 causes half-maximal inhibition of full-length JAK2V617F and JAK2 wild-type enzymes at 0.5 nM. NVP-BSK805 blocks the growth of JAK2V617F cells (Ba/F3) and induces apoptosis with a GI50 at concentrations ＜100 nM. As constitutive STAT5 phosphorylation in dependent on JAK2, NVP-BSK805 is found to potently suppress STAT5 phophorylation at ≥ 100 nM concentrations in the JAK2 V617F -mutant cell lines, like MB-02. Incubation of SET-2 cells with 150 nM and 1 μM of NVP-BSK805, which corresponds to concentration yielding 75% and 95% growth inhibition, respectively, for 24, 48, and 72 hours lead to concentration- and time- dependent induction of apoptosis. These results are evidenced by the detection of cleaved PARP, reduced Bcl-xL expression, and a strong increase in the number of cells with less than 2N DNA content. [1] NVP-BSK805 triggered cell death requires activation of caspase cascades and is overcome by caspase inhibition in both SET-2 and MB-02 cells. NVP-BSK805 modulates the post-translational modification of Bim and levels of Mcl-1 in JAK2V617F cells, SET-2 and MB-02 cells. [2]

Oral bioavailability of NVP-BSK805 in mice is estimated to be 45%, while it is 50% in rats. Oral administration of NVP-BSK805 at 150 mg/kg suppresses STAT5 phosphorylation, splenomegaly, and leukemic cell spreading in a Ba/F3 JAK2V617F cell–driven mouse model. NVP-BSK805 suppresses rhEpo-induced STAT5 phosphorylation as well as rhEpo-mediated polycythemia and splenomegaly in BALB/c mice at doses of 25, 50, and 100 mg/kg orally. [1]

The anti-proliferative activity of JAK2 inhibitors is determined by incubating cells for 72 hours with an 8-point concentration range of compound and cell proliferation relative to DMSO-treated cells is measured using the colorimetric WST-1 (Roche Diagnostics GmbH) cell viability readout. Of each triplicate treatment, the mean is calculated and these data are plotted in XLfit 4 (ID Business Solutions, Ltd.) to determine the half-maximal growth inhibition (GI50) values.(Only for Reference)