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JAK2 Inhibitors (jak2 + inhibitor)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	50%

Selected Abstracts

TG101209, a novel JAK2 inhibitor, has significant in vitro activity in multiple myeloma and displays preferential cytotoxicity for CD45+ myeloma cells,

AMERICAN JOURNAL OF HEMATOLOGY, Issue 9 2010
Vijay Ramakrishnan
Interaction of myeloma cells with the bone marrow microenvironment is mediated in large part through different cytokines, especially VEGF and IL6. These cytokines, especially IL6, leads to upregulation of the JAK/STAT pathway in myeloma cell, contributing to increased proliferation, decreased apoptosis, and acquired drug resistance. Here, we examined the preclinical activity of a novel JAK2 inhibitor TG101209. TG101209 induced dose- and time-dependent cytotoxicity in a variety of multiple myeloma (MM) cell lines. The induction of cytotoxicity was associated with inhibition of cell cycle progression and induction of apoptosis in myeloma cell lines and patient-derived plasma cells. Evaluation of U266 cell lines and patient cells, which have a mix of CD45 positive and negative cells, demonstrated more profound cytotoxicity and antiproliferative activity of the drug on the CD45+ population relative to the CD45, cells. Exploring the mechanism of action of TG101209 indicated downregulation of pJak2, pStat3, and Bcl-xl levels with upregulation of pErk and pAkt levels indicating cross talk between signaling pathways. TG101209, when used in combination with the PI3K inhibitor LY294002, demonstrated synergistic cytotoxicity against myeloma cells. Our results provide the rationale for clinical evaluation of TG101209 alone or in combination with PI3K/Akt inhibitors in MM. Am. J. Hematol., 2010. © 2010 Wiley-Liss, Inc. [source]

Treatment options for hydroxyurea-refractory disease complications in myeloproliferative neoplasms: JAK2 inhibitors, radiotherapy, splenectomy and transjugular intrahepatic portosystemic shunt

EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 3 2010
Elena Mishchenko
Abstract Clinical care of patients with polycythemia vera, essential thrombocythemia and myelofibrosis (MF) requires not only a broad understanding of general treatment principles but also familiarity with the management of hydroxyurea-refractory disease complications. The latter include progressive splenomegaly, symptomatic portal hypertension (e.g. ascites, variceal bleeding), pulmonary hypertension, bone pain, intractable pruritus, constitutional symptoms (e.g. fatigue, night sweats) and cachexia (i.e. loss of lean body mass, general ill health, poor appetite). Some of these symptoms are directly or indirectly related to extramedullary hematopoiesis (EMH) and others to proinflammatory cytokine excess. Results from recent clinical trials of JAK inhibitors suggest remarkable activity in MF-associated constitutional symptoms, cachexia, pruritus and hydroxyurea-refractory splenomegaly. Involved-field radiotherapy is best utilized in the setting of EMH-associated symptoms, including ascites, bone (extremity) pain and pulmonary hypertension. Splenectomy is indicated in the presence of drug-refractory splenomegaly and frequent red cell transfusion requirement. Transjugular intrahepatic portosystemic shunt is used to alleviate symptoms of portal hypertension. [source]

CXCR4-independent rescue of the myeloproliferative defect of the gata1low myelofibrosis mouse model by Aplidin®,

JOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2010
Maria Verrucci
The discovery of JAK2 mutations in Philadelphia-negative myeloproliferative neoplasms has prompted investigators to evaluate mutation-targeted treatments to restore hematopoietic cell functions in these diseases. However, the results of the first clinical trials with JAK2 inhibitors are not as promising as expected, prompting a search for additional drugable targets to treat these disorders. In this paper, we used the hypomorphic Gata1low mouse model of primary myelofibrosis (PMF), the most severe of these neoplasms, to test the hypothesis that defective marrow hemopoiesis and development of extramedullary hematopoiesis in myelofibrosis is due to insufficient p27Kip1 activity and is treatable by Aplidin®, a cyclic depsipeptide that activates p27Kip1 in several cancer cells. Aplidin® restored expression of Gata1 and p27Kip1 in Gata1low hematopoietic cells, proliferation of marrow progenitor cells in vitro and maturation of megakaryocytes in vivo (reducing TGF-,/VEGF levels released in the microenvironment by immature Gata1low megakaryocytes). Microvessel density, fibrosis, bone growth, and marrow cellularity were normal in Aplidin®-treated mice and extramedullary hematopoiesis did not develop in liver although CXCR4 expression in Gata1low progenitor cells remained low. These results indicate that Aplidin® effectively alters the natural history of myelofibrosis in Gata1low mice and suggest this drug as candidate for clinical evaluation in PMF. J. Cell. Physiol. 225: 490,499, 2010. © 2010 Wiley-Liss, Inc. [source]

Exposure of glia to pro-oxidant agents revealed selective Stat1 activation by H2O2 and Jak2-independent antioxidant features of the Jak2 inhibitor AG490

GLIA, Issue 13 2007
Roser Gorina
Abstract The JAK/STAT pathway is activated in response to cytokines and growth factors. In addition, oxidative stress can activate this pathway, but the causative pro-oxidant forms are not well identified. We exposed cultures of rat glia to H2O2, FeSO4, nitroprussiate, or paraquat. We assessed oxidative stress by measuring reactive oxygen species (ROS) and oxidated proteins, we determined phosphorylated Stat1 (pStat1), and we evaluated the effect of antioxidants (trolox, propyl gallate, and N -acetylcysteine) and of Jak2 (Janus tyrosine kinases) inhibitors (AG490 and Jak2-Inhibitor-II). Pro-oxidant agents induced ROS and protein oxidation, excluding nitroprussiate that induced protein nitrosylation. H2O2, and to a lesser extent FeSO4, increased the level of pStat1, whereas nitroprussiate and paraquat did not. Trolox and propyl gallate strongly prevented ROS formation but they did not abolish H2O2 -induced pStat1. In contrast, NAC did not reduce the level of ROS but it prevented the increase of pStat1 induced by H2O2, evidencing a differential effect on ROS formation and on Stat1 phosphorylation. H2O2 induced pStat1 in mixed glia cultures and, to a lesser extent, in purified astroglia, but not in microglia. Jak2 inhibitors reduced H2O2 -induced pStat1, suggesting the involvement of this kinase in the increased phosphorylation of Stat1 by peroxide. Unexpectedly, AG490, but not Jak2-Inhibitor-II, reduced ROS formation, and it abrogated lipid peroxidation in microsomal preparations. Furthermore, AG490 reduced ROS in glial cells that were transfected with siRNA to silence Jak2 expression. These findings reveal previously unrecognized Jak2-independent antioxidant properties of AG490, and show that Jak2-dependent Stat1 activation by peroxide is dissociated from ROS generation. © 2007 Wiley-Liss, Inc. [source]