Novel pyrrole carboxamide inhibitors of JAK2 as potential treatment of myeloproliferative disorders.

Compound 1, a hit from the screening of our chemical collection displaying activity against JAK2, was deconstructed for SAR analysis into three regions, which were explored. A series of compounds was synthesized leading to the identification of the potent and orally bioavailable JAK2 inhibitor 16 (NMS-P830), which showed an encouraging tumour growth inhibition in SET-2 xenograft tumour model, with evidence for JAK2 pathway suppression demonstrated by in vivo pharmacodynamic effects.

JAK2-V617F-mediated signalling is dependent on lipid rafts and statins inhibit JAK2-V617F-dependent cell growth.

Aberrant JAK2 signalling plays an important role in the aetiology of myeloproliferative neoplasms (MPNs). JAK2 inhibitors, however, do not readily eliminate neoplastic MPN cells and thus do not induce patient remission. Further understanding JAK2 signalling in MPNs may uncover novel avenues for therapeutic intervention. Recent work has suggested a potential role for cellular cholesterol in the activation of JAK2 by the erythropoietin receptor and in the development of an MPN-like disorder in mice. Our study demonstrates for the first time that the MPN-associated JAK2-V617F kinase localizes to lipid rafts and that JAK2-V617F-dependent signalling is inhibited by lipid raft disrupting agents, which target membrane cholesterol, a critical component of rafts. We also show for the first time that statins, 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors, widely used to treat hypercholesterolaemia, induce apoptosis and inhibit JAK2-V617F-dependent cell growth. These cells are more sensitive to statin treatment than non-JAK2-V617F-dependent cells. Importantly, statin treatment inhibited erythropoietin-independent erythroid colony formation of primary cells from MPN patients, but had no effect on erythroid colony formation from healthy individuals. Our study is the first to demonstrate that JAK2-V617F signalling is dependent on lipid rafts and that statins may be effective in a potential therapeutic approach for MPNs.

[Src kinases in the process of maturation megakryocyte progenitors]. / Kinazy src w procesie dojrzewania progenitorów megakariocytów.

Src family protein tyrosine kinases play key roles in cell morphology, proliferation, motility, and survival in megakaryocytopoiesis. Six of Src family kinases (Fyn, Lyn, Fgr, Hck, Src and Yes), are present in megakaryocytes (Mks). Src kinases are negative factors of megakaryocytopoiesis induced by thrombopoietin. The inhibitors of Src kinases might be useful as agents inducing maturation of Mks. The experiments with inhibitors of Src kinases used in culture of Mk progenitors and potential megakaryocyte cell lines gave new information about the role of Src kinases in the development of Mks. The pyrrolo-pyrimidyne reagents family and highly selective inhibitor, SU6656, are known and used inhibitors of Src kinases. The presence of inhibitor in ex vivo culture of Mk progenitors blocks proliferation and simultaneously induces the changes in cell morphology, phenotype and ploidy level, indicating the maturation of the cells. The inhibitors of Src kinases also might play the therapeutic role. Dasatinib, dual Bcr-Abl/Src kinase inhibitor, is of high activity and induces hematologic and cytogenetic responses in patients with chronic myelogenous leukaemia in blast crisis.