Suppression of multiple anti‐apoptotic BCL2 family proteins recapitulates the effects of JAK2 inhibitors in JAK2V617F driven myeloproliferative neoplasms

AbstractPhiladelphia chromosome-negative myeloproliferative neoplasms are hematopoietic stem cell disorders characterized by dysregulated proliferation of mature myeloid blood cells. They can present as polycythemia vera, essential thrombocythemia, or myelofibrosis and are characterized by constitutive activation of JAK2 signaling. They share a propensity for thrombo-hemorrhagic complications and the risk of progression to acute myeloid leukemia. Attention has also been drawn to JAK2 mutant clonal hematopoiesis of indeterminate potential as a possible precursor state of MPN. Insight into the pathogenesis as well as options for the treatment of MPN has increased in the last years thanks to modern sequencing technologies and functional studies. Mutational analysis provides information on the oncogenic driver mutations in JAK2, CALR, or MPL in the majority of MPN patients. In addition, molecular markers enable more detailed prognostication and provide guidance for therapeutic decisions. While JAK2 inhibitors represent a standard of care for MF and resistant/refractory PV, allogeneic hematopoietic stem cell transplantation remains the only therapy with a curative potential in MPN so far but is reserved to a subset of patients. Thus, novel concepts for therapy are an important need, particularly in MF. Novel JAK2 inhibitors, combination therapy approaches with ruxolitinib, as well as therapeutic approaches addressing new molecular targets are in development. Current standards and recent advantages are discussed in this review.

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

European Journal Of Haematology ◽

10.1111/j.1600-0609.2010.01480.x ◽

2010 ◽

Vol 85 (3) ◽

pp. 192-199 ◽

Cited By ~ 19

Author(s):

Elena Mishchenko ◽

Ayalew Tefferi

Keyword(s):

Transjugular Intrahepatic Portosystemic Shunt ◽

Myeloproliferative Neoplasms ◽

Treatment Options ◽

Portosystemic Shunt ◽

Refractory Disease ◽

Intrahepatic Portosystemic Shunt ◽

Jak2 Inhibitors

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Weight Loss, Splenomegaly, and Hypocholesterolemia in Myeloproliferative Neoplasms: Patterns and Relevance from the Pre JAK2 Inhibitor Era.

Blood ◽

10.1182/blood.v114.22.3918.3918 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3918-3918 ◽

Cited By ~ 7

Author(s):

Ruben A. Mesa ◽

Susan Schwager ◽

Jocelin Huang ◽

Animesh D. Pardanani ◽

Kebede Hussein ◽

...

Keyword(s):

Weight Loss ◽

Conflicts Of Interest ◽

Myeloproliferative Neoplasms ◽

Prognostic Score ◽

Univariate Analysis ◽

The Body ◽

Costal Margin ◽

Additional Time ◽

Jak2 Inhibitor ◽

Jak2 Inhibitors

Abstract Abstract 3918 Poster Board III-854 BACK GROUND We have previously demonstrated that the myeloproliferative neoplasms (MPNs) of primary myelofibrosis (PMF), polycythemia vera (PV), and essential thrombocythemia (ET) can lead to weight loss, splenomegaly and constitutional symptoms (Cancer 2007;109:68–76). Additionally we have demonstrated that hypocholesterolemia in MPN patients is associated with decreased survival (Blood 2007;110:a2548). Given that current JAK2 inhibitor trials are demonstrating the ability to reverse MPN associated splenomegaly (Haematologica 2009;94(Suppl 2)439 a1088) and cachexia (Blood 2008;112(11):a1760) we sought to determine the baseline natural history for these variables in patients treated prior to the JAK2 inhibitor era. METHODS We analyzed the Mayo MPN database for patients (not treated with JAK2 inhibitors) with information on disease prognosis, presentation, therapies, height and weight at diagnosis, and outcomes. Additionally, when available, we analyzed additional weights during the clinical course, the body mass index (BMI- (weight/(height*height)), spleen size, and peripheral blood studies including lipids. Results: Patients 783 patients with MPNs (followed for a median of 51 months (range 1-871 months); 60% having expired) were identified for the analysis (PV=158, ET=255, PMF=370) with 541 (69%) having a weight at the time of diagnosis, the remainder had a weight obtained a median of 7.8 months after diagnosis. Additionally, 508 patients (65%) had a weight value available from 1–3 additional time points during the course of their disease. Corresponding measurements of splenomegaly, or absence thereof, were noted in 766 cases (98%). Lipid panels (obtained within 18 months of diagnosis) were available in 264 patients. Results by MPN disease type are listed in the Table. Impact on prognosis Univariate analysis of variables discussed which negatively impacted survival included the subtype of MPN (not surprisingly worse for PMF p<0.001), weight loss of greater than 10% during the course of follow-up (P<0.001), or development of splenomegaly of >10 cm below the left costal margin (p=0.004) whereas hypocholesterolemia was significant only for the subset of PMF patients (P=0.03). The IWG-MRT International Prognostic Score (IPSS - Cervantes et. al. Blood 2009) was the only variable prognostically relevant in multivariate analysis (P<0.001). Conclusions Progressive splenomegaly, weight loss, and hypocholesterolemia are common across all MPNs but are most prognostically detrimental in PMF. Ongoing and future trials of JAK2 inhibitors will answer whether reversal of these latter hypercatabolic and proliferative manifestations of disease will improve outcomes for MPN patients. Disclosures: No relevant conflicts of interest to declare.

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Combination Treatment with JAK2 and PI3K Inhibitors in Myeloproliferative Neoplasms

Blood ◽

10.1182/blood.v120.21.180.180 ◽

2012 ◽

Vol 120 (21) ◽

pp. 180-180

Author(s):

Meng Ling Choong ◽

Christian Pecquet ◽

Shi Jing Tai ◽

Jacklyn WY Yong ◽

Vishal Pendharkar ◽

...

Keyword(s):

Bone Marrow ◽

Combination Treatment ◽

Kinase Inhibitors ◽

Myeloproliferative Neoplasms ◽

Jak2 V617f ◽

Pi3k Inhibitor ◽

Spleen Weight ◽

Pi3k Inhibitors ◽

Jak2 Inhibitor ◽

Jak2 Inhibitors

Abstract Abstract 180 Background and Aims. The main pathogenic molecular events associated with myeloproliferative neoplasms (Polycythemia Vera, Essential Thrombocytosis, and Primary Myelofibrosis) are mutations in Janus kinase 2 (JAK2) or in the thrombopoietin receptor that arise in the hematopoietic stem/progenitor cells. Both type of mutations lead to constitutive activation of the JAK2 signaling pathways. The approved JAK2 inhibitor (Ruxolitinib) is not expected to be selective for the mutant JAK2/receptor signaling or to completely suppress the multiple signaling pathways activated by the aberrant JAK2 signaling. We postulate that myeloproliferative neoplasms can be treated more effectively if we target the constitutive JAK2 signaling by a JAK2 inhibitor together with another kinase inhibitor targeting a specific pathway that is co-activated by the aberrant JAK2 signaling. This should increase targeting specificity, reduce JAK2 inhibitor dosages, and minimize potential side effects of these drugs. To this end, we constructed cell line models of myeloproliferative neoplasms and tested the models using a JAK2 inhibitor in combination with a panel of kinase inhibitors to identify combination pairs that give the best synergism. The synergistic pair was further confirmed in mouse models of myeloproliferative neoplasms. Methods. Mouse Ba/F3 cells were engineered to express either JAK2 WT, or JAK2 V617F, or TpoR W515L, or TpoR JAK2 WT, or TpoR JAK2 V617F, or Bcr-Abl. The effect of two JAK2 inhibitors (Ruxolitinib and TG101348) in combination with a panel of 15 various kinase inhibitors (one JNK, one B-Raf, one ROCK-1, one TIE-2, one PI3K, two CDK, two MAPK, three p38, and three mTOR inhibitors). An 8×8 constant ratio Latin square design were used for testing inhibition of cell proliferation/survival in these cell line models. Calculations were carried out using the Chou-Talalay method to determine which drug-pair demonstrated synergism in inhibiting cell growth. Further eight PI3K inhibitors were acquired and tested when we found strong synergism between the JAK2 inhibitors and the PI3K inhibitor ZSTK474 in the first panel. The engineered Ba/F3 cells were also inoculated into female BALB/c nude mice to generate the JAK2 mutant mouse model. These mice were treated intravenously with Ruxolitinib and the PI3K inhibitor GDC0941. Blood profile and physical parameters of the mice were measured for 14 days post treatment. Bone marrow cells from mice reconstituted with bone marrow from JAK2 V617F knock-in mice were plated for colony formation in the presence or absence of Ruxolitinib and the PI3K inhibitor GDC0941. Primary Epo-independent colonies from CD34+ cells of one PV patient were assessed in two independent experiments in the presence or absence of combination drugs. Results. Out of 15 kinase inhibitors tested, three PI3K inhibitors (ZSTK474, GDC0941 and BEZ235), synergized with JAK2 inhibitors (Ruxolitinib and TG101348) in inhibiting cell growth. The combination index was less than 0.5 in all 8×8 dose combination ratios. The JAK2-PI3K inhibitors combination was specific for JAK2 signaling as growth of Ba/F3 cells expressing Bcr-Abl (at equivalent STAT5 activation levels) was unaffected by this combination treatment. Balb/c mice inoculated with Ba/F3 cells expressing TpoR JAK2 V617F were found to have increased spleen weight due to proliferation of autonomous cells. Our combination treatment using Ruxolitinib and GDC0941 could drastically reduce spleen weight compared to treatment with either compound alone. Endogenous erythroid colony forming unit (CFU-E) and burst forming unit (BFU-E) formation from JAK2 V617F knock-in bone marrow cells was reduced significantly by the combined use of Ruxolitinib and GDC0941 compared to individual drugs. Similarly, Epo-independent BFU-E colony formation from peripheral CD34+ cells of one JAK2 V617F-positive PV patient was reduced significantly by the drug combination. Conclusions. Our findings of strong synergy between the JAK2 inhibitors and PI3K inhibitors suggested that we may be able to administer these drugs at lower concentrations than when the drugs are used individually. It provides a framework for combination trials using compounds in these two classes in patients with myeloproliferative neoplasms. Disclosures: No relevant conflicts of interest to declare.

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Therapeutic Advances in Myeloproliferative Neoplasms: The Role of New-Small Molecule Inhibitors

American Society of Clinical Oncology Educational Book ◽

10.14694/edbook_am.2012.32.175 ◽

2012 ◽

pp. 406-410 ◽

Cited By ~ 2

Author(s):

Srdan Verstovsek

Keyword(s):

Molecular Mechanisms ◽

Therapeutic Potential ◽

Myeloproliferative Neoplasms ◽

Janus Kinase ◽

Treatment Focus ◽

Rational Combination ◽

Short And Long Term ◽

Jak2 Inhibitors

Overview: The discovery that a somatic point mutation (JAK2V617F) in the Janus kinase 2 ( JAK2) is highly prevalent in patients with myeloproliferative neoplasms (MPNs) has been a crucial breakthrough in our understanding of the underlying molecular mechanisms of these diseases. Therefore, preclinical and clinical research in recent years has focused intensely on the development of new therapies targeted to JAK2. These efforts culminated in recent approval of ruxolitinib as the first official therapy for patients with intermediate- or high-risk myelofibrosis (MF). Therapy with JAK2 inhibitors substantially improves quality of life and reduces organomegaly in MF with or without JAKV617F mutation. Recent results suggest that patients with advanced MF may live longer when receiving therapy with ruxolitinib. However, JAK2 inhibitors do not eliminate the disease and new medications are needed to expand on the benefits seen with JAK2 inhibitors. Although many agents are still in the early stages of development, the wealth of publications and presentations has continued to support our growing understanding of the pathophysiology of MF as well as the potential short- and long-term outcomes of these new and diverse approaches to treatment. Focus of ongoing efforts is particularly on the improvements in anemia and fibrosis, as well as on rational combination trials of JAK2 inhibitors and other potentially active agents. Therapeutic potential and limitations of JAK2 inhibitors and other novel medications in clinical studies are reviewed.

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