Combined Inhibition of Janus Kinase 1/2 for the Treatment of JAK2V617F-Driven Neoplasms: Selective Effects on Mutant Cells and Improvements in Measures of Disease Severity

Abstract

Purpose: Deregulation of the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway is a hallmark for the Philadelphia chromosome-negative myeloproliferative diseases polycythemia vera, essential thrombocythemia, and primary myelofibrosis. We tested the efficacy of a selective JAK1/2 inhibitor in cellular and in vivo models of JAK2-driven malignancy. Experimental Design: A novel inhibitor of JAK1/2 was characterized using kinase assays. Cellular effects of this compound were measured in cell lines bearing the JAK2V617F or JAK1V658F mutation, and its antiproliferative activity against primary polycythemiavera patient cells was determined using clonogenic assays. Antineoplastic activity in vivo was determined using a JAK2V617F-driven xenograft model, and effects of the compound on survival, organomegaly, body weight, and disease-associated inflammatory markers were measured. Results: INCB16562 potently inhibited proliferation of cell lines and primary cells from PV patients carrying the JAK2V617F or JAK1V658F mutation by blocking JAK-STAT signaling and inducing apoptosis. In vivo, INCB16562 reduced malignant cell burden, reversed splenomegaly and normalized splenic architecture, improved body weight gains, and extended survival in a model of JAK2V617F-driven hematologic malignancy. Moreover, these mice suffered from markedly elevated levels of inflammatory cytokines, similar to advanced myeloproliferative disease patients, which was reversed upon treatment. Conclusions: These data showed that administration of the dual JAK1/2 inhibitor INCB16562 reduces malignant cell burden, normalizes spleen size and architecture, suppresses inflammatory cytokines, improves weight gain, and extends survival in a rodent model of JAK2V617F-driven hematologic malignancy. Thus, selective inhibitors of JAK1 and JAK2 represent a novel therapy for the patients with myeloproliferative diseases and other neoplasms associated with JAK dysregulation. ( The myeloproliferative diseases (MPD) are clonal proliferative disorders of hematopoietic progenitor cells with unique pathobiologies. Their clinical presentations include an increase in circulating functional, differentiated myeloid cell lineages that largely define the particular MPD. Broadly, the MPDs can be categorized into those that that are Philadelphia chromosome negative or positive, the latter of which defines nearly all cases of chronic myeloid leukemia (CML; refs. 1, 2). The seminal discovery that the Philadelphia chromosome resulted from a 9;22 translocation and produces the BCR-ABL fusion oncoprotein defined the first MPD-associated mutant allele (reviewed in ref.3).

Efficacy of NS-018, a potent and selective JAK2/Src inhibitor, in primary cells and mouse models of myeloproliferative neoplasms

“…35, 36, 37 In this study, NS-018 seemed as effective as these inhibitors in this model (Figure 4). These results demonstrate the in vivo potency of NS-018.…”

Efficacy of the JAK2 inhibitor INCB16562 in a murine model of MPLW515L-induced thrombocytosis and myelofibrosis

“…Both INCB16562 and INCB18424, the clinical compound used in PMF patient trials, inhibit JAK2 most potently, followed by JAK1 (INCB16562 is 5-fold less potent against JAK1 compared with JAK2 in enzyme-based assays versus 2-fold for INCB18424), TYK2 (14-fold less potent versus 7-fold for INCB18424), and then JAK3 (30-fold less potent versus 150-fold for INCB18424). We believe therefore that the observations made regarding the effects of JAK2 inhibition with INCB16562 in our in vitro and in vivo studies are relevant to clinical experiences with INCB18424 (and Li and colleagues 38 ) and with other JAK2 inhibitors (TG101348, CEP701). 28,29 We demonstrate that treatment once daily with doses of INCB16562 that inhibit JAK-STAT signaling in vivo, markedly improve survival in the MPLW515L murine model.…”

mTOR Inhibitors Alone and in Combination with JAK2 Inhibitors Effectively Inhibit Cells of Myeloproliferative Neoplasms

“…In preclinical models, ATP-competitive JAK2 inhibitors prevented the proliferation of JAK2 V617F mutant cells in vitro and mitigated myeloproliferation in JAK2 V617F transgenic animals [20], [21]. When employed in clinical trials, JAK2 inhibitors produced significant clinical improvement in patients with myelofibrosis [22], [23] or hydroxyurea-resistant PV or ET [24] at such an extent that the JAK1 and JAK2 inhibitor ruxolitinib has been approved recently by FDA for the treatment of patients with intermediate and high risk myelofibrosis based on the results of two large phase III trials [25], [26] demonstrating rapid and sustained reduction of splenomegaly and improvement of constitutional symptoms.…”