Selective Janus associated kinase 1 inhibition as a therapeutic target in myelofibrosis

Novel Janus-kinase (JAK) Inhibitors in Myelofibrosis

INTRODUCTION

JAK inhibitors (JAKis), used in the treatment of myelofibrosis, have entered standard treatment, providing significant improvements in spleen size and symptom burden. Although splenomegaly provides a reduction and some improvement in cytopenia, there is still a way to go. Novel JAKis are being investigated to overcome barriers to treatment access, such as therapeutic challenges, intolerance, and unresponsiveness.

AREAS COVERED

This review includes the current status of JAKi treatment for myelofibrosis, mainly focusing on investigational JAKis; jaktinib, lestaurtinib, itacitinib, gandotinib, BMS-911543, ilginatinib, TQ05105, and flonoltinib maleate. MEDLINE and clinicaltrials.gov were screened to identify all completed or active studies on this topic. The outcomes of the preclinical studies and clinical trials are presented and discussed for each drug.

EXPERT OPINION

In patients with myelofibrosis, momelotinib was effective in treating anemia, whereas jaktinib was effective in both anemia and Total Symptom Score (TSS). More phase 3 studies are needed to provide more precise evidence. The increasing variety of JAKis will allow for more personalized treatment options for myelofibrosis in the future. The potential impact on disease progression, molecular responses, and the duration of this response will become important parameters for future evaluations of these drugs.

JAK inhibitors for the treatment of VEXAS syndrome

Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic (VEXAS) syndrome is a novel described autoinflammatory entity for which the diagnosis is defined by somatic mutations of the UBA1 X-linked gene in hematopoietic progenitor cells. The clinical manifestations are heterogeneous since they range from autoinflammatory symptoms to the presence of underlying hematologic disorders such as myelodysplastic syndromes. Response to treatment in VEXAS is very poor and to date, the therapeutic strategies adopted are only partially effective. However, recently described cohorts of subjects with VEXAS treated with Janus kinase inhibitors (JAK-I) proved that these drugs can be effective in the treatment of several manifestations related to the disease. Herein, we carried out a brief literature review that includes cohorts and single cases in which JAK-I were adopted as a promising strategy to manage VEXAS patients. Subsequently, we described our experience with JAK-I in VEXAS, illustrating the first case, to our knowledge, of a 65-year-old man who was successfully treated with the selective JAK-1 inhibitor filgotinib.

A Novel Morphological Parameter Predicting Fibrotic Evolution in Myeloproliferative Neoplasms: New Evidence and Molecular Insights

Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) represent a group of hematological disorders that are traditionally considered as indistinct slow progressing conditions; still, a subset of cases shows a rapid evolution towards myelofibrotic bone marrow failure. Specific abnormalities in the megakaryocyte lineage seem to play a central role in this evolution, especially in the bone marrow fibrosis but also in the induction of myeloproliferation. In this review, we analyze the current knowledge of prognostic factors of MPNs related to their evolution to myelofibrotic bone marrow failure. Moreover, we focused the role of the megakaryocytic lineage in the various stages of MPNs, with updated examples of MPNs in vitro and in vivo models and new therapeutic implications.

Anti-inflammatory effects of ruxolitinib on chronic neutrophilic leukemia harboring CSF3R-T618I mutation with bilateral renal abscesses

Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm (MPN) characterized by sustained mature neutrophilic leukocytosis. Recently, presence of colony-stimulating factor 3 receptor (CSF3R) mutations has been added to the diagnostic criteria for CNL. Anti-inflammatory effects of the JAK1/2 inhibitor ruxolitinib relieve constitutional symptoms associated with MPN, such as fatigue, night sweats, and fever. We present a case of CNL harboring CSF3R-T618I mutation exacerbated by concomitant bilateral renal abscesses, which was refractory to antibiotics, at the time of initial diagnosis. In this case, ruxolitinib rapidly improved not only CNL but the infection, due to its anti-inflammatory potency.

Current and Emerging Targeted Therapies for Acute Graft-Versus-Host Disease

Acute graft-versus-host disease (GVHD), the major complication after allogeneic hematopoietic cell transplant (HCT), develops in approximately 50% of patients. The primary treatment is high-dose systemic steroids, but treatment failure is common, and steroid-refractory (SR) GVHD is the leading cause of non-relapse mortality after allogeneic HCT. Ruxolitinib became the first treatment for SR GVHD to obtain US Food and Drug Administration approval, and other new treatments are actively being studied. We searched the literature using the PubMed database and clinical trials using ClinicalTrials.gov to identify the most promising new treatments for GVHD. In this review, we categorize potential new treatments for GVHD by their mechanism of action (e.g., antibodies that deplete T cells or prevent their trafficking to target tissues, proteasome inhibitors, tyrosine kinase inhibitors, and other agents) and summarize the results from clinical trials.

The BCR-ABL1-negative myeloproliferative neoplasms: a review of JAK inhibitors in the therapeutic armamentarium

INTRODUCTION

The classical BCR-ABL1-negative myeloproliferative neoplasms (MPN) include primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET). They are characterized by stem cell-derived clonal proliferation, harbor Janus kinase 2 (JAK2), or calreticulin (CALR), or myeloproliferative leukemia virus oncogene (MPL) driver mutations and exert an over activated JAK-signal transducer and activator of transcription (STAT) pathway. Therefore JAK inhibiting strategies have been successfully investigated in MPN clinical trials. Areas covered: The present review aims to provide a concise overview of the current and future role of JAK inhibitors in the therapeutic armamentarium of MPN. Expert opinion: The JAK1/JAK2 inhibitor ruxolitinib has clearly enriched the therapeutic armamentarium of MPN and is now licenced for more than five years in MF and over three years as second line in PV. Momelotinib, although of limited activity in MPN trials, demonstrated unique property of improving MF associated anemia. Less myelosuppressive or more selective JAK inhibitors like pacritinib, NS-01872 or Itacitinib are new promising agents tested in MF. JAK inhibition has become a cornerstone of MPN therapy and future efforts focus on ruxolitinib-based combinations and new JAK inhibitors.

Primary analysis of a phase II open-label trial of INCB039110, a selective JAK1 inhibitor, in patients with myelofibrosis

Combined Janus kinase 1 (JAK1) and JAK2 inhibition therapy effectively reduces splenomegaly and symptom burden related to myelofibrosis but is associated with dose-dependent anemia and thrombocytopenia. In this open-label phase II study, we evaluated the efficacy and safety of three dose levels of INCB039110, a potent and selective oral JAK1 inhibitor, in patients with intermediate- or high-risk myelofibrosis and a platelet count ≥50×10⁹/L. Of 10, 45, and 32 patients enrolled in the 100 mg twice-daily, 200 mg twice-daily, and 600 mg once-daily cohorts, respectively, 50.0%, 64.4%, and 68.8% completed week 24. A ≥50% reduction in total symptom score was achieved by 35.7% and 28.6% of patients in the 200 mg twice-daily cohort and 32.3% and 35.5% in the 600 mg once-daily cohort at week 12 (primary end point) and 24, respectively. By contrast, two patients (20%) in the 100 mg twice-daily cohort had ≥50% total symptom score reduction at weeks 12 and 24. For the 200 mg twice-daily and 600 mg once-daily cohorts, the median spleen volume reductions at week 12 were 14.2% and 17.4%, respectively. Furthermore, 21/39 (53.8%) patients who required red blood cell transfusions during the 12 weeks preceding treatment initiation achieved a ≥50% reduction in the number of red blood cell units transfused during study weeks 1-24. Only one patient discontinued for grade 3 thrombocytopenia. Non-hematologic adverse events were largely grade 1 or 2; the most common was fatigue. Treatment with INCB039110 resulted in clinically meaningful symptom relief, modest spleen volume reduction, and limited myelosuppression.

Janus kinase inhibition lessens inflammation and ameliorates disease in murine models of hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) comprises an emerging spectrum of inherited and noninherited disorders of the immune system characterized by the excessive production of cytokines, including interferon-γ and interleukins 2, 6, and 10 (IL-2, IL-6, and IL-10). The Janus kinases (JAKs) transduce signals initiated following engagement of specific receptors that bind a broad array of cytokines, including those overproduced in HLH. Based on the central role for cytokines in the pathogenesis of HLH, we sought to examine whether the inhibition of JAK function might lessen inflammation in murine models of the disease. Toward this end, we examined the effects of JAK inhibition using a model of primary (inherited) HLH in which perforin-deficient (Prf1(-∕-)) mice are infected with lymphocytic choriomeningitis virus (LCMV) and secondary (noninherited) HLH in which C57BL/6 mice receive repeated injections of CpG DNA. In both models, treatment with the JAK1/2 inhibitor ruxolitinib significantly lessened the clinical and laboratory manifestations of HLH, including weight loss, organomegaly, anemia, thrombocytopenia, hypercytokinemia, and tissue inflammation. Importantly, ruxolitinib treatment also significantly improved the survival of LCMV-infectedPrf1(-∕-)mice. Mechanistic studies revealed that in vivo exposure to ruxolitinib inhibited signal transducer and activation of transcription 1-dependent gene expression, limited CD8(+)T-cell expansion, and greatly reduced proinflammatory cytokine production, without effecting degranulation and cytotoxic function. Collectively, these findings highlight the JAKs as novel, druggable targets for mitigating the cytokine-driven hyperinflammation that occurs in HLH. These observations also support the incorporation of JAK inhibitors such as ruxolitinib into future clinical trials for patients with these life-threatening disorders.

Cytokine Regulation of Microenvironmental Cells in Myeloproliferative Neoplasms

The term myeloproliferative neoplasms (MPN) refers to a heterogeneous group of diseases including not only polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), but also chronic myeloid leukemia (CML), and systemic mastocytosis (SM). Despite the clinical and biological differences between these diseases, common pathophysiological mechanisms have been identified in MPN. First, aberrant tyrosine kinase signaling due to somatic mutations in certain driver genes is common to these MPN. Second, alterations of the bone marrow microenvironment are found in all MPN types and have been implicated in the pathogenesis of the diseases. Finally, elevated levels of proinflammatory and microenvironment-regulating cytokines are commonly found in all MPN-variants. In this paper, we review the effects of MPN-related oncogenes on cytokine expression and release and describe common as well as distinct pathogenetic mechanisms underlying microenvironmental changes in various MPN. Furthermore, targeting of the microenvironment in MPN is discussed. Such novel therapies may enhance the efficacy and may overcome resistance to established tyrosine kinase inhibitor treatment in these patients. Nevertheless, additional basic studies on the complex interplay of neoplastic and stromal cells are required in order to optimize targeting strategies and to translate these concepts into clinical application.

Inflammation as a Driver of Clonal Evolution in Myeloproliferative Neoplasm

Our understanding of inflammation's role in the pathogenesis of myeloproliferative neoplasm (MPN) is evolving. The impact of chronic inflammation, a characteristic feature of MPN, likely goes far beyond its role as a driver of constitutional symptoms. An inflammatory response to the neoplastic clone may be responsible for some pathologic aspects of MPN. Moreover, JAK2V617F mutated hematopoietic stem and progenitor cells are resistant to inflammation, and this gives the neoplastic clone a selective advantage allowing for its clonal expansion. Because inflammation plays a central role in MPN inflammation is a logical therapeutic target in MPN.