CHZ868 is a type II JAK inhibitor with potential antitumor activity that reverses the persistence of type I JAK inhibitors and can be used to study leukemia.

JAK2:110 nM, CMK cells:378 nM (GI50), SET2 cells:59 nM (GI50)

CHZ868 effectively inhibits constitutive phosphorylation of JAK2 and STAT5 in JAK2V617F SET2 cells. The compound demonstrates potent inhibition of SET2 cell proliferation (GI50=59nM) and exhibits 6-fold lower growth inhibitory activity against CMK cells (GI50=378nM)[1]. At a concentration of 100 nM, CHZ868 shows activity against 26 kinases, including JAK2 and TYK2. It is believed that CHZ868 interacts with the hinge region of JAK2 through two hydrogen bonds, formed between the amino-pyridine of CHZ868 and the backbone-NH/CO of L932, while the pyridine occupies the adenine pocket of the ATP binding site. CHZ868 effectively suppresses the growth of CRLF2-rearranged human B-ALL cells and disrupts JAK2 signaling[1].

Characterized by high passive permeability, good metabolic stability, and low water solubility, CHZ868 also exhibits moderate blood clearance and good oral bioavailability, rendering it suitable for in vivo applications. In mice with human or murine B-ALL, CHZ868 enhances survival. When used in combination with dexamethasone, CHZ868 synergistically induces apoptosis in JAK2-dependent B-ALLs, leading to improved survival compared to CHZ868 alone[1].

CHZ868 is dissolved in DMSO to make 10 mM stock solution and diluted in culture media. Cells are treated with CHZ868 (0, 0.05, 0.1, 0.2 μM) or vehicle (DMSO). After 48 hr (Ba/F3 cells) or 72 hr (MHH-CALL4 and PDX cells), CellTiter-Glo Luminescent Cell Viability Assay is added (10 μL undiluted or 25 μL of a 1:2 dilution in each well) and plates are read [2].

CHZ868 is reconstituted in 0.5% methylcellulose / 0.5% Tween-80 and administered at doses of 10 or 30 mg/kg/day by oral gavage. Pharmacokinetic/pharmacodynamic and efficacy studies in the mouse model of rhEpo-induced polycythemia are carried out essentially. Detection of STAT5 phosphorylation in spleen lysates by Meso Scale Discovery is performed [2].