8-[3,5-Difluoro-4-(4-morpholinylmethyl)phenyl]-2-[1-(4-piperidinyl)-1H-pyrazol-4-yl]quinoxaline dihydrochloride

Janus kinases (JAKs) are non-receptor tyrosine kinases that mediate signaling through cytokine receptors, often to members of the signal transducer and activator of transcription (STAT) family. A point mutation of JAK2, V617F, activates signaling through STAT5 and drives certain forms of cancer. NVP-BSK805 is a potent inhibitor of JAK2 that also inhibits the JAK2^V617F mutant enzyme (IC₅₀s for both enzymes ~ 0.5 nM). It displays at least 20-fold selectivity against other JAK enzymes and a panel of serine/threonine and tyrosine kinases. This ATP-competitive inhibitor is orally bioavailable and has a long half-life in vivo, suppressing leukemic cell spreading and splenomegaly in JAK2^V617F cell-driven disease in mice. NVP-BSK805 suppresses recombinant human erythropoietin-induced polycythemia and extramedullary erythropoiesis in mice and rats. NVP-BSK805 can be used to study the molecular mechanisms involved in JAK2^V617F signaling in cells.