CYT387, a novel JAK2 inhibitor, induces hematologic responses and normalizes inflammatory cytokines in murine myeloproliferative neoplasms.
Activating alleles of Janus kinase 2 (JAK2) such as JAK2(V617F) are central to the pathogenesis of myeloproliferative neoplasms (MPN), suggesting that small molecule inhibitors targeting JAK2 may be therapeutically useful. We have identified an aminopyrimidine derivative (CYT387), which inhibits JAK1, JAK2, and tyrosine kinase 2 (TYK2) at low nanomolar concentrations, with few additional targets. Between 0.5 and 1.5muM CYT387 caused growth suppression and apoptosis in JAK2-dependent hematopoietic cell lines, while nonhematopoietic cell lines were unaffected. In a murine MPN model, CYT387 normalized white cell counts, hematocrit, spleen size, and restored physiologic levels of inflammatory cytokines. Despite the hematologic responses and reduction of the JAK2(V617F) allele burden, JAK2(V617F) cells persisted and MPN recurred upon cessation of treatment, suggesting that JAK2 inhibitors may be unable to eliminate JAK2(V617F) cells, consistent with preliminary results from clinical trials of JAK2 inhibitors in myelofibrosis. While the clinical benefit of JAK2 inhibitors may be substantial, not the least due to reduction of inflammatory cytokines and symptomatic improvement, our data add to increasing evidence that kinase inhibitor monotherapy of malignant disease is not curative, suggesting a need for drug combinations to optimally target the malignant cells.
Tyner
Jeffrey W
JW
Knight Cancer Institute, Oregon Health & Science University, Portland, OR 97239, USA.
Bumm
Thomas G
TG
Deininger
Jutta
J
Wood
Lisa
L
Aichberger
Karl J
KJ
Loriaux
Marc M
MM
Druker
Brian J
BJ
Burns
Christopher J
CJ
Fantino
Emmanuelle
E
Deininger
Michael W
MW
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics / Q000276:immunology; D001549:Benzamides / Q000494:pharmacology*; D045744:Cell Line, Tumor; D016207:Cytokines / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D004195:Disease Models, Animal; D004354:Drug Screening Assays, Antitumor; D019337:Hematologic Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D006410:Hematopoiesis / Q000187:drug effects* / Q000235:genetics / Q000276:immunology; D053613:Janus Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D020125:Mutation, Missense; D009196:Myeloproliferative Disorders / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*
D001549:Benzamides; D016207:Cytokines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; C546012:N-(cyanomethyl)-4-(2-((4-(4-morpholinyl)phenyl)amino)-4-pyrimidinyl)benzamide; C507905:Jak1 protein, mouse; C507926:Jak2 protein, mouse; D053613:Janus Kinase 1; D053614:Janus Kinase 2
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