Preclinical characterization of the selective JAK1/2 inhibitor INCB018424: therapeutic implications for the treatment of myeloproliferative neoplasms

A Maximum-Use Trial of Ruxolitinib Cream in Adolescents and Adults with Atopic Dermatitis

BACKGROUND

Ruxolitinib cream is a topical formulation of ruxolitinib, an inhibitor of Janus kinase 1 and Janus kinase 2.

OBJECTIVE

We aimed to determine the safety, tolerability, and bioavailability of 1.5% ruxolitinib cream under maximum-use conditions in patients with atopic dermatitis. Efficacy was evaluated as an exploratory objective.

METHODS

Eligible patients aged ≥ 12-65 years with atopic dermatitis, an Investigator's Global Assessment score ≥ 2, and ≥ 25% affected body surface area were enrolled in an open-label, maximum-use phase I study conducted in the USA and Canada. Patients applied 1.5% ruxolitinib cream twice daily to lesions identified at baseline for the first 28 days and continued use only on active lesions for an additional 28 days (extension period). Safety was assessed by frequency, duration, and severity of treatment-emergent adverse events. Plasma concentrations of ruxolitinib and pharmacokinetic parameters were assessed as secondary endpoints.

RESULTS

Overall, 41 patients (median age, 17 years; 51% male) were enrolled and 37 (90.2%) entered the extension period, all of whom completed the study. Treatment-emergent adverse events were reported in 13 patients (31.7%). Treatment-related adverse events were reported in four patients (9.8%). The mean (standard deviation) steady-state plasma concentration was 104 (309) nM during the first 28 days, well below the half-maximal inhibitory concentration of Janus kinase-mediated myelosuppression in the bone marrow (281 nM), and decreased further during the extension period. Higher plasma concentrations were detected in a few patients who were treated for a very high affected body surface area. At day 56, 94.6% of patients achieved ≥ 75% improvement in the Eczema Area and Severity Index.

CONCLUSIONS

Under maximum-use conditions, ruxolitinib cream was generally well tolerated, with approximately one-third of patients experiencing treatment-emergent adverse events and few treatment-related adverse events. The mean steady-state plasma concentration of ruxolitinib was well below the level expected to affect bone marrow production of blood cells, with a small number of patients exhibiting higher plasma concentrations. In addition, ruxolitinib cream showed a high level of efficacy in patients with atopic dermatitis involving ≥ 25% affected body surface area.

CLINICALTRIALS

GOV IDENTIFIER

NCT03920852.

JAK inhibitors and COVID-19

During SARS-CoV-2 infection, the innate immune response can be inhibited or delayed, and the subsequent persistent viral replication can induce emergency signals that may culminate in a cytokine storm contributing to the severe evolution of COVID-19. Cytokines are key regulators of the immune response and virus clearance, and, as such, are linked to the—possibly altered—response to the SARS-CoV-2. They act via a family of more than 40 transmembrane receptors that are coupled to one or several of the 4 Janus kinases (JAKs) coded by the human genome, namely JAK1, JAK2, JAK3, and TYK2. Once activated, JAKs act on pathways for either survival, proliferation, differentiation, immune regulation or, in the case of type I interferons, antiviral and antiproliferative effects. Studies of graft-versus-host and systemic rheumatic diseases indicated that JAK inhibitors (JAKi) exert immunosuppressive effects that are non-redundant with those of corticotherapy. Therefore, they hold the potential to cut-off pathological reactions in COVID-19. Significant clinical experience already exists with several JAKi in COVID-19, such as baricitinib, ruxolitinib, tofacitinib, and nezulcitinib, which were suggested by a meta-analysis (Patoulias et al.) to exert a benefit in terms of risk reduction concerning major outcomes when added to standard of care in patients with COVID-19. Yet, only baricitinib is recommended in first line for severe COVID-19 treatment by the WHO, as it is the only JAKi that has proven efficient to reduce mortality in individual randomized clinical trials (RCT), especially the Adaptive COVID-19 Treatment Trial (ACTT-2) and COV-BARRIER phase 3 trials. As for secondary effects of JAKi treatment, the main caution with baricitinib consists in the induced immunosuppression as long-term side effects should not be an issue in patients treated for COVID-19.

We discuss whether a class effect of JAKi may be emerging in COVID-19 treatment, although at the moment the convincing data are for baricitinib only. Given the key role of JAK1 in both type I IFN action and signaling by cytokines involved in pathogenic effects, establishing the precise timing of treatment will be very important in future trials, along with the control of viral replication by associating antiviral molecules.

Arachidonic acid, a clinically adverse mediator in the ovarian cancer microenvironment, impairs JAK-STAT signaling in macrophages by perturbing lipid raft structures

Survival of ovarian carcinoma is associated with the abundance of immunosuppressed CD163^highCD206^high tumor‐associated macrophages (TAMs) and high levels of arachidonic acid (AA) in the tumor microenvironment. Here, we show that both associations are functionally linked. Transcriptional profiling revealed that high CD163 and CD206/MRC1 expression in TAMs is strongly associated with an inhibition of cytokine‐triggered signaling, mirrored by an impaired transcriptional response to interferons and IL‐6 in monocyte‐derived macrophages by AA. This inhibition of pro‐inflammatory signaling is caused by dysfunctions of the cognate receptors, indicated by the inhibition of JAK1, JAK2, STAT1, and STAT3 phosphorylation, and by the displacement of the interferon receptor IFNAR1, STAT1 and other immune‐regulatory proteins from lipid rafts. AA exposure led to a dramatic accumulation of free AA in lipid rafts, which appears to be mechanistically crucial, as the inhibition of its incorporation into phospholipids did not affect the AA‐mediated interference with STAT1 phosphorylation. Inhibition of interferon‐triggered STAT1 phosphorylation by AA was reversed by water‐soluble cholesterol, known to prevent the perturbation of lipid raft structure by AA. These findings suggest that the pharmacologic restoration of lipid raft functions in TAMs may contribute to the development new therapeutic approaches.

Functional stratification of cancer drugs through integrated network similarity

Drugs not only perturb their immediate protein targets but also modulate multiple signaling pathways. In this study, we explored networks modulated by several drugs across multiple cancer cell lines by integrating their targets with transcriptomic and phosphoproteomic data. As a result, we obtained 236 reconstructed networks covering five cell lines and 70 drugs. A rigorous topological and pathway analysis showed that chemically and functionally different drugs may modulate overlapping networks. Additionally, we revealed a set of tumor-specific hidden pathways with the help of drug network models that are not detectable from the initial data. The difference in the target selectivity of the drugs leads to disjoint networks despite sharing a similar mechanism of action, e.g., HDAC inhibitors. We also used the reconstructed network models to study potential drug combinations based on the topological separation and found literature evidence for a set of drug pairs. Overall, network-level exploration of drug-modulated pathways and their deep comparison may potentially help optimize treatment strategies and suggest new drug combinations.

Avian auditory hair cell regeneration is accompanied by JAK/STAT-dependent expression of immune-related genes in supporting cells

The avian hearing organ is the basilar papilla that, in sharp contrast to the mammalian cochlea, can regenerate sensory hair cells and thereby recover from deafness within weeks. The mechanisms that trigger, sustain and terminate the regenerative response in vivo are largely unknown. Here, we profile the changes in gene expression in the chicken basilar papilla after aminoglycoside antibiotic-induced hair cell loss using RNA-sequencing. We identified changes in gene expression of a group of immune-related genes and confirmed with single-cell RNA-sequencing that these changes occur in supporting cells. In situ hybridization was used to further validate these findings. We determined that the JAK/STAT signaling pathway is essential for upregulation of the damage-response genes in supporting cells during the second day after induction of hair cell loss. Four days after ototoxic damage, we identified newly regenerated, nascent auditory hair cells that express genes linked to termination of the JAK/STAT signaling response. The robust, transient expression of immune-related genes in supporting cells suggests a potential functional involvement of JAK/STAT signaling in sensory hair cell regeneration.

Ruxolitinib suppresses liver fibrosis progression and accelerates fibrosis reversal via selectively targeting Janus kinase 1/2

BACKGROUND

JAK1 and JAK2 have been implicated in fibrosis and cancer as a fibroblast-related marker; however, their role in liver fibrosis has not been elucidated. Here, we aim to determine the effect and underlying mechanism of JAK1/2 inhibition on liver fibrosis and hepatic stellate cells (HSCs) and further explore the therapeutic efficacy of Ruxolitinib, a JAK1/2 selective inhibitor, on preventing and reversing liver fibrosis in mice.

METHODS

Immunohistochemistry staining of JAK1 and JAK2 were performed on liver tissue in mice with hepatic fibrosis and human liver tissue microarray of liver cirrhosis and liver cancer. LX-2 cells treated with specific siRNA of JAK1 and JAK2 were used to analysis activation, proliferation and migration of HSCs regulated by JAK1/2. The effects of Ruxolitinib (JAK1/2 inhibitor) on liver fibrosis were studied in LX-2 cells and two progressive and reversible fibrosis animal models (carbon tetrachloride (CCl₄), Thioacetamide (TAA)).

RESULTS

We found that JAK1/2 expression was positively correlated with the progression of HCC in humans and the levels of liver fibrosis in mice. Silencing of JAK1/2 down-regulated their downstream signaling and inhibited proliferation, migration, and activation of HSCs in vitro, while Ruxolitinib had similar effects on HSCs. Importantly, Ruxolitinib significantly attenuated fibrosis progression, improved cell damage, and accelerated fibrosis reversal in the liver of mice treated with CCl₄ or TAA.

CONCLUSIONS

JAK1/2 regulates the function of HSCs and plays an essential role in liver fibrosis and HCC development. Its inhibitor, Ruxolitinib, may be an effective drug for preventing and treating liver fibrosis.

Role of JAK inhibitors in myeloproliferative neoplasms: current point of view and perspectives

Classic Philadelphia-negative myeloproliferative neoplasms (MPN) include polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), classified as primary (PMF), or secondary to PV or ET. All MPN, regardless of the underlying driver mutation in JAK2/CALR/MPL, are invariably associated with dysregulation of JAK/STAT pathway. The discovery of JAK2V617F point mutation prompted the development of small molecules inhibitors of JAK tyrosine kinases (JAK inhibitors-JAKi). To date, among JAKi, ruxolitinib (RUX) and fedratinib (FEDR) are approved for intermediate and high-risk MF, and RUX is also an option for high-risk PV patients inadequately controlled by or intolerant to hydroxyurea. While not yet registered, pacritinib (PAC) and momelotinib (MMB), proved to be effective particularly in thrombocytopenic and anemic MF patients, respectively. In most cases, JAKi are effective in reducing splenomegaly and alleviating disease-related symptoms. However, almost 50% lose response by three years and dose-dependent toxicities may lead to suboptimal dosing or treatment discontinuation. To date, although not being disease-modifying agents, JAKi represent the therapeutic backbone particularly in MF patient. To optimize therapeutic strategies, many trials with drug combinations of JAKi with novel molecules are ongoing. This review critically discusses the role of JAKi in the modern management of patients with MPN.

Early Use of Low-Dose Ruxolitinib: A Promising Strategy for the Treatment of Acute and Chronic GVHD

Janus kinases (JAK) are a family of tyrosine kinases (JAK1, JAK2, JAK3, and TYK2) that transduce cytokine-mediated signals through the JAK–STAT metabolic pathway. These kinases act by regulating the transcription of specific genes capable of inducing biological responses in several immune cell subsets. Inhibition of Janus kinases interferes with the JAK–STAT signaling pathway. Besides being used in the treatment of cancer and inflammatory diseases, in recent years, they have also been used to treat inflammatory conditions, such as graft-versus-host disease (GVHD) and cytokine release syndrome as complications of allogeneic hematopoietic stem cell transplantation and cell therapy. Recently, the FDA approved the use of ruxolitinib, a JAK1/2 inhibitor, in the treatment of acute steroid-refractory GVHD (SR-aGVHD), highlighting the role of JAK inhibition in this immune deregulation. Ruxolitinib was initially used to treat myelofibrosis and true polycythemia in a high-dose treatment and caused hematological toxicity. Since a lower dosage often could not be effective, the use of ruxolitinib was suspended. Subsequently, ruxolitinib was evaluated in adult patients with SR-aGVHD and was found to achieve a rapid and effective response. In addition, its early low-dose use in pediatric patients affected by GVHD has proved effective, safe, and reasonably preventive. The review aims to describe the potential properties of ruxolitinib to identify new therapeutic strategies.

Transient Inhibition of the JAK/STAT Pathway Prevents B-ALL Development in Genetically Predisposed Mice

Preventing development of childhood B-cell acute lymphoblastic leukemia (B-ALL), a disease with devastating effects, is a longstanding and unsolved challenge. Heterozygous germline alterations in the PAX5 gene can lead to B-ALL upon accumulation of secondary mutations affecting the JAK/STAT signaling pathway. Preclinical studies have shown that this malignant transformation occurs only under immune stress such as exposure to infectious pathogens. Here we show in Pax5+/- mice that transient, early-life administration of clinically relevant doses of ruxolitinib, a JAK1/2 inhibitor, significantly mitigates the risk of B-ALL following exposure to infection; 1 of 29 animals treated with ruxolitinib developed B-ALL versus 8 of 34 untreated mice. Ruxolitinib treatment preferentially targeted Pax5+/- versus wild-type B-cell progenitors and exerted unique effects on the Pax5+/- B-cell progenitor transcriptional program. These findings provide the first in vivo evidence for a potential strategy to prevent B-ALL development.

SIGNIFICANCE

JAK/STAT inhibition suppresses tumorigenesis in a B-ALL-susceptible mouse model, presenting a novel approach to prevent B-ALL onset.

Preclinical studies of Flonoltinib Maleate, a novel JAK2/FLT3 inhibitor, in treatment of JAK2V617F-induced myeloproliferative neoplasms

Janus kinase 2 (JAK2) hyperactivation by JAK2V617F mutation leads to myeloproliferative neoplasms (MPNs) and targeting JAK2 could serve as a promising therapeutic strategy for MPNs. Here, we report that Flonoltinib Maleate (FM), a selective JAK2/FLT3 inhibitor, shows high selectivity for JAK2 over the JAK family. Surface plasmon resonance assays verified that FM had a stronger affinity for the pseudokinase domain JH2 than JH1 of JAK2 and had an inhibitory effect on JAK2 JH2V617F. The cocrystal structure confirmed that FM could stably bind to JAK2 JH2, and FM suppressed endogenous colony formation of primary erythroid progenitor cells from patients with MPNs. In several JAK2V617F-induced MPN murine models, FM could dose-dependently reduce hepatosplenomegaly and prolong survival. Similar results were observed in JAK2V617F bone marrow transplantation mice. FM exhibited strong inhibitory effects on fibrosis of the spleen and bone marrow. Long-term FM treatment showed good pharmacokinetic/pharmacodynamic characteristics with high drug exposure in tumor-bearing tissues and low toxicity. Currently, FM has been approved by the National Medical Products Administration of China (CXHL2000628), and this study will guide clinical trials for patients with MPNs.

Targeting Janus Kinase (JAK) for Fighting Diseases: The Research of JAK Inhibitor Drugs

Janus Kinase (JAK), a nonreceptor protein tyrosine kinase, has emerged as an excellent target through research and development since its discovery in the 1990s. As novel small-molecule targeted drugs, JAK inhibitor drugs have been successfully used in the treatment of rheumatoid arthritis (RA), myofibrosis (MF) and ulcerative colitis (UC). With the gradual development of JAK targets in the market, JAK inhibitors have also received very considerable feedback in the treatment of autoimmune diseases such as atopic dermatitis (AD), Crohn's disease (CD) and graft-versus host disease (GVHD). This article reviews the research progress of JAK inhibitor drugs: introducing the existing JAK inhibitors on the market and some JAK inhibitors in clinical trials currently. In addition, the synthesis of various types of JAK inhibitors were summarized, and the effects of different drug structures on drug inhibition and selectivity.

Circulating Endothelial Cell Levels Correlate with Treatment Outcomes of Splanchnic Vein Thrombosis in Patients with Chronic Myeloproliferative Neoplasms

Circulating endothelial cells (CECs) are viable, apoptotic or necrotic cells, identified by CD 146 surface antigen expression, considered a biomarker of thrombotic risk, given their active role in inflammatory, procoagulant and immune processes of the vascular compartment. Growing evidence establishes that CECs are also involved in the pathogenesis of several hematological and solid malignancies. The primary aim of this study was to verify if CEC levels could predict both the course and treatment responses of splanchnic vein thrombosis (SVT), either in patients affected by myeloproliferative neoplasms (MPNs) or liver disease. Thus, a retrospective multicenter study was performed; fifteen patients receiving anticoagulant oral treatment with vitamin k antagonists (VKA) for SVT were evaluated. Nine patients were affected by MPN, and all of them received cytoreduction in addition to anticoagulant therapy; four of these patients had primary myelofibrosis (PMF) and were treated with ruxolitinib (RUX), and one patient with primary myelofibrosis, two patients with essential thrombocythemia (ET), and two patients with polycythemia vera (PV) were treated with hydroxyurea (HU). Six patients affected by liver diseases (three with liver cirrhosis and three with hepatocellular carcinoma) were included as the control group. CECs were assayed by flow cytometry on peripheral blood at specific time points, for up to six months after enrollment. The CEC levels were related to C-reactive protein (CRP) levels, splenic volume reduction, and thrombus recanalization, mainly in MPN patients. In patients with liver cirrhosis (LC) and hepatocellular carcinoma (HCC), for which the mechanism of SVT development is quite different, the relationship between CEC and SV reduction was absent. In conclusion, the CEC levels showed a significant correlation with the extent of venous thrombosis and endothelial cell damage in myeloproliferative neoplasm patients with splanchnic vein thrombosis. Although preliminary, these results show how monitoring CEC levels during cytoreductive and anticoagulant treatments may be useful to improve SVT outcome in MPN patients.

Genome-wide CRISPR-Cas9 screen identifies rationally designed combination therapies for CRLF2-rearranged Ph-like ALL

Acute lymphoblastic leukemia (ALL) harboring the IgH-CRLF2 rearrangement (IgH-CRLF2-r) exhibits poor clinical outcomes and is the most common subtype of Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL). While multiple chemotherapeutic regimens, including ruxolitinib monotherapy and/or its combination with chemotherapy, are being tested, their efficacy is reportedly limited. To identify molecules/pathways relevant for IgH-CRLF2-r ALL pathogenesis, we performed genome-wide CRISPR-Cas9 dropout screens in the presence or absence of ruxolitinib using 2 IgH-CRLF2-r ALL lines that differ in RAS mutational status. To do so, we employed a baboon envelope pseudotyped lentiviral vector system, which enabled, for the first time, highly efficient transduction of human B cells. While single-guide RNAs (sgRNAs) targeting CRLF2, IL7RA, or JAK1/2 significantly affected cell fitness in both lines, those targeting STAT5A, STAT5B, or STAT3 did not, suggesting that STAT signaling is largely dispensable for IgH-CRLF2-r ALL cell survival. We show that regulators of RAS signaling are critical for cell fitness and ruxolitinib sensitivity and that CRKL depletion enhances ruxolitinib sensitivity in RAS wild-type (WT) cells. Gilteritinib, a pan-tyrosine kinase inhibitor that blocks CRKL phosphorylation, effectively killed RAS WT IgH-CRLF2-r ALL cells in vitro and in vivo, either alone or combined with ruxolitinib. We further show that combining gilteritinib with trametinib, a MEK1/2 inhibitor, is an effective means to target IgH-CRLF2-r ALL cells regardless of RAS mutational status. Our study delineates molecules/pathways relevant for CRLF2-r ALL pathogenesis and could suggest rationally designed combination therapies appropriate for disease subtypes.

Kinases as Potential Therapeutic Targets for Anti-coronaviral Therapy

The global coronavirus disease-19 (COVID-19) has affected more than 140 million and killed more than 3 million people worldwide as of April 20, 2021. The novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been identified as an etiological agent for COVID-19. Several kinases have been proposed as possible mediators of multiple viral infections, including life-threatening coronaviruses like SARS-CoV-1, Middle East syndrome coronavirus (MERS-CoV), and SARS-CoV-2. Viral infections hijack abundant cell signaling pathways, resulting in drastic phosphorylation rewiring in the host and viral proteins. Some kinases play a significant role throughout the viral infection cycle (entry, replication, assembly, and egress), and several of them are involved in the virus-induced hyperinflammatory response that leads to cytokine storm, acute respiratory distress syndrome (ARDS), organ injury, and death. Here, we highlight kinases that are associated with coronavirus infections and their inhibitors with antiviral and potentially anti-inflammatory, cytokine-suppressive, or antifibrotic activity.

T Helper Cell Lineage-Defining Transcription Factors: Potent Targets for Specific GVHD Therapy?

Allogenic hematopoietic stem cell transplantation (allo-HSCT) represents a potent and potentially curative treatment for many hematopoietic malignancies and hematologic disorders in adults and children. The donor-derived immunity, elicited by the stem cell transplant, can prevent disease relapse but is also responsible for the induction of graft-versus-host disease (GVHD). The pathophysiology of acute GVHD is not completely understood yet. In general, acute GVHD is driven by the inflammatory and cytotoxic effect of alloreactive donor T cells. Since several experimental approaches indicate that CD4 T cells play an important role in initiation and progression of acute GVHD, the contribution of the different CD4 T helper (Th) cell subtypes in the pathomechanism and regulation of the disease is a central point of current research. Th lineages derive from naïve CD4 T cell progenitors and lineage commitment is initiated by the surrounding cytokine milieu and subsequent changes in the transcription factor (TF) profile. Each T cell subtype has its own effector characteristics, immunologic function, and lineage specific cytokine profile, leading to the association with different immune responses and diseases. Acute GVHD is thought to be mainly driven by the Th1/Th17 axis, whereas Treg cells are attributed to attenuate GVHD effects. As the differentiation of each Th subset highly depends on the specific composition of activating and repressing TFs, these present a potent target to alter the Th cell landscape towards a GVHD-ameliorating direction, e.g. by inhibiting Th1 and Th17 differentiation. The finding, that targeting of Th1 and Th17 differentiation appears more effective for GVHD-prevention than a strategy to inhibit Th1 and Th17 cytokines supports this concept. In this review, we shed light on the current advances of potent TF inhibitors to alter Th cell differentiation and consecutively attenuate GVHD. We will focus especially on preclinical studies and outcomes of TF inhibition in murine GVHD models. Finally, we will point out the possible impact of a Th cell subset-specific immune modulation in context of GVHD.

Pathological α-synuclein recruits LRRK2 expressing pro-inflammatory monocytes to the brain

BACKGROUND

Leucine rich repeat kinase 2 (LRRK2) and SNCA are genetically linked to late-onset Parkinson's disease (PD). Aggregated α-synuclein pathologically defines PD. Recent studies identified elevated LRRK2 expression in pro-inflammatory CD16+ monocytes in idiopathic PD, as well as increased phosphorylation of the LRRK2 kinase substrate Rab10 in monocytes in some LRRK2 mutation carriers. Brain-engrafting pro-inflammatory monocytes have been implicated in dopaminergic neurodegeneration in PD models. Here we examine how α-synuclein and LRRK2 interact in monocytes and subsequent neuroinflammatory responses.

METHODS

Human and mouse monocytes were differentiated to distinct transcriptional states resembling macrophages, dendritic cells, or microglia, and exposed to well-characterized human or mouse α-synuclein fibrils. LRRK2 expression and LRRK2-dependent Rab10 phosphorylation were measured with monoclonal antibodies, and myeloid cell responses to α-synuclein fibrils in R1441C-Lrrk2 knock-in mice or G2019S-Lrrk2 BAC mice were evaluated by flow cytometry. Chemotaxis assays were performed with monocyte-derived macrophages stimulated with α-synuclein fibrils and microglia in Boyden chambers.

RESULTS

α-synuclein fibrils robustly stimulate LRRK2 and Rab10 phosphorylation in human and mouse macrophages and dendritic-like cells. In these cells, α-synuclein fibrils stimulate LRRK2 through JAK-STAT activation and intrinsic LRRK2 kinase activity in a feed-forward pathway that upregulates phosphorylated Rab10. In contrast, LRRK2 expression and Rab10 phosphorylation are both suppressed in microglia-like cells that are otherwise highly responsive to α-synuclein fibrils. Corroborating these results, LRRK2 expression in the brain parenchyma occurs in pro-inflammatory monocytes infiltrating from the periphery, distinct from brain-resident microglia. Mice expressing pathogenic LRRK2 mutations G2019S or R1441C have increased numbers of infiltrating pro-inflammatory monocytes in acute response to α-synuclein fibrils. In primary cultured macrophages, LRRK2 kinase inhibition dampens α-synuclein fibril and microglia-stimulated chemotaxis.

CONCLUSIONS

Pathologic α-synuclein activates LRRK2 expression and kinase activity in monocytes and induces their recruitment to the brain. These results predict that LRRK2 kinase inhibition may attenuate damaging pro-inflammatory monocyte responses in the brain.

Innovation in the treatment of atopic dermatitis: Emerging topical and oral Janus kinase inhibitors

Atopic dermatitis (AD) is characterized by chronic, eczematous, severe pruritic skin lesions. The knowledge on the pathogenesis of AD is driving the development of new drugs. From the research results, it has been revealed that Th2 cell-mediated immunity, skin barrier dysfunction, and pruritus cause a vicious cycle of AD. On the other hand, the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway are one of the essential signaling pathways in various inflammatory diseases including AD. In particular, TSLP, IL-4, IL-13 and IL-22 occupy an important position for Th2 cell-mediated immune reaction. Moreover, experimentally pan-JAK inhibitor suppress the STAT3 activation and improved the skin barrier function. Furthermore TSLP, IL-4, IL-13 and IL-31 contribute a lot to chronic pruritus of AD, and transmitted via JAK-STAT pathway. Therefore, JAK inhibitors are promising candidates for the treatment of severe AD. Here we review clinical trials of topical dergocitinib; a pan-JAK inhibitor, ruxolitinib; a JAK1 and JAK2 inhibitor, and tofacitinib; a JAK1, JAK2, and JAK3 inhibitor and oral baricitinib; a JAK1 and JAK2 inhibitor, abrocitinib and upadacitinib; JAK1 inhibitor. Significant improvements in the symptoms were obtained by each drug with low frequency of adverse events. In particular, oral JAK inhibitors have the ability to improve the pruritus and skin symptoms quickly. Therefore, the emergence of these topical and oral JAK inhibitors would be regarded as an innovation in the treatment of atopic dermatitis.

A Novel ELISA-Based Peptide Biosensor Assay for Screening ABL1 Activity in vitro: A Challenge for Precision Therapy in BCR-ABL1 and BCR-ABL1 Like Leukemias

The pathogenic role of the overactivated ABL1 tyrosine kinase (TK) pathway is well recognized in some forms of BCR-ABL1 like acute lymphoblastic leukemia (ALL); TK inhibitors represent a useful therapeutic choice in these patients who respond poorly to conventional chemotherapy. Here we report a novel peptide biosensor (P_ABL)-ELISA assay to investigate ABL1 activity in four immortalized leukemic cell lines with different genetic background. The P_ABL sequence comprises an ABL1 tyrosine (Y) phosphorylation site and a targeting sequence that increases the specificity for ABL1; additional peptides (Y-site-mutated (P_ABL-_F) and fully-phosphorylated (P_PHOSPHO-_ABL) biosensors) were included in the assay. After incubation with whole cell lysates, average P_ABL phosphorylation was significantly increased (basal vs. P_ABL phosphorylation: 6.84 ± 1.46% vs. 32.44 ± 3.25%, p-value < 0.0001, two-way ANOVA, Bonferroni post-test, percentages relative to P_PHOSPHO-_ABL in each cell line). Cell lines expressing ABL1-chimeric proteins (K562, ALL-SIL) presented the higher TK activity on P_ABL; a lower signal was instead observed for NALM6 and REH (p < 0.001 and p < 0.05 vs. K562, respectively). Phosphorylation was ABL1-mediated, as demonstrated by the specific inhibition of imatinib (p < 0.001 for K562, NALM6, ALL-SIL and p < 0.01 for REH) in contrast to ruxolitinib (JAK2-inhibitor), and occurred on the ABL1 Y-site, as demonstrated by P_ABL-F whose phosphorylation was comparable to basal levels. In order to validate this novel P_ABL-ELISA assay on leukemic cells isolated from patient’s bone marrow aspirates, preliminary analysis on blasts derived from an adult affected by chronic myeloid leukaemia (BCR-ABL1 positive) and a child affected by ALL (BCR-ABL1 negative) were performed. Phosphorylation of P_ABL was specifically inhibited after the incubation of BCR-ABL1 positive cell lysates with imatinib, but not with ruxolitinib. While requiring further optimization and validation in leukemic blasts to be of clinical interest, the P_ABL-based ELISA assay provides a novel in vitro tool for screening both the aberrant ABL1 activity in BCR-ABL1 like ALL leukemic cells and their potential response to TK inhibitors.

Successful ruxolitinib administration for a patient with steroid-refractory idiopathic pneumonia syndrome following hematopoietic stem cell transplantation: A case report and literature review

Idiopathic pneumonia syndrome (IPS) is an acute lung complication observed after the early posthematopoietic stem cell transplantation (HSCT) period. Ruxolitinib was effective for a patient with myelodysplastic syndrome who developed severe IPS after second HSCT. No severe adverse effects were observed. Ruxolitinib may be an alternative choice for HSCT-related IPS.

A prenylated dsRNA sensor protects against severe COVID-19

Inherited genetic factors can influence the severity of COVID-19, but the molecular explanation underpinning a genetic association is often unclear. Intracellular antiviral defenses can inhibit the replication of viruses and reduce disease severity. To better understand the antiviral defenses relevant to COVID-19, we used interferon-stimulated gene (ISG) expression screening to reveal that 2′-5′-oligoadenylate synthetase 1 (OAS1), through ribonuclease L, potently inhibits severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We show that a common splice-acceptor single-nucleotide polymorphism (Rs10774671) governs whether patients express prenylated OAS1 isoforms that are membrane-associated and sense-specific regions of SARS-CoV-2 RNAs or if they only express cytosolic, nonprenylated OAS1 that does not efficiently detect SARS-CoV-2. In hospitalized patients, expression of prenylated OAS1 was associated with protection from severe COVID-19, suggesting that this antiviral defense is a major component of a protective antiviral response.

Second-Generation Jak2 Inhibitors for Advanced Prostate Cancer: Are We Ready for Clinical Development?

Simple Summary

Prostate Cancer (PC) is currently estimated to affect 1 in 9 men and is the second leading cause of cancer in men in the US. While androgen deprivation therapy, which targets the androgen receptor, is one of the front-line therapies for advanced PC and for recurrence of organ-confined PC treated with surgery, lethal castrate-resistant PC develops consistently in patients. PC is a multi-focal cancer with different grade carcinoma areas presenting simultaneously. Jak2-Stat5 signaling pathway has emerged as a potentially highly effective molecular target in PCs with positive areas for activated Stat5 protein. Activated Jak2-Stat5 signaling can be readily targeted by the second-generation Jak2-inhibitors that have been developed for myeloproliferative and autoimmune disorders and hematological malignancies. In this review, we analyze and summarize the Jak2 inhibitors that are currently in preclinical and clinical development.

Abstract

Androgen deprivation therapy (ADT) for metastatic and high-risk prostate cancer (PC) inhibits growth pathways driven by the androgen receptor (AR). Over time, ADT leads to the emergence of lethal castrate-resistant PC (CRPC), which is consistently caused by an acquired ability of tumors to re-activate AR. This has led to the development of second-generation anti-androgens that more effectively antagonize AR, such as enzalutamide (ENZ). However, the resistance of CRPC to ENZ develops rapidly. Studies utilizing preclinical models of PC have established that inhibition of the Jak2-Stat5 signaling leads to extensive PC cell apoptosis and decreased tumor growth. In large clinical cohorts, Jak2-Stat5 activity predicts PC progression and recurrence. Recently, Jak2-Stat5 signaling was demonstrated to induce ENZ-resistant PC growth in preclinical PC models, further emphasizing the importance of Jak2-Stat5 for therapeutic targeting for advanced PC. The discovery of the Jak2V617F somatic mutation in myeloproliferative disorders triggered the rapid development of Jak1/2-specific inhibitors for a variety of myeloproliferative and auto-immune disorders as well as hematological malignancies. Here, we review Jak2 inhibitors targeting the mutated Jak2V617F vs. wild type (WT)-Jak2 that are currently in the development pipeline. Among these 35 compounds with documented Jak2 inhibitory activity, those with potency against WT-Jak2 hold strong potential for advanced PC therapy.

Circulating Protein Disulfide Isomerase Is Associated with Increased Risk of Thrombosis in JAK2-Mutated Myeloproliferative Neoplasms

PURPOSE

Thromboembolic events (TE) are the most common complications of myeloproliferative neoplasms (MPN). Clinical parameters, including patient age and mutation status, are used to risk-stratify patients with MPN, but a true biomarker of TE risk is lacking. Protein disulfide isomerase (PDI), an endoplasmic reticulum protein vital for protein folding, also possesses essential extracellular functions, including regulation of thrombus formation. Pharmacologic PDI inhibition prevents thrombus formation, but whether pathologic increases in PDI increase TE risk remains unknown.

EXPERIMENTAL DESIGN

We evaluated the association of plasma PDI levels and risk of TE in a cohort of patients with MPN with established diagnosis of polycythemia vera (PV) or essential thrombocythemia (ET), compared with healthy controls. Plasma PDI was measured at enrollment and subjects followed prospectively for development of TE.

RESULTS

A subset of patients, primarily those with JAK2-mutated MPN, had significantly elevated plasma PDI levels as compared with controls. Plasma PDI was functionally active. There was no association between PDI levels and clinical parameters typically used to risk-stratify patients with MPN. The risk of TE was 8-fold greater in those with PDI levels above 2.5 ng/mL. Circulating endothelial cells from JAK2-mutated MPN patients, but not platelets, demonstrated augmented PDI release, suggesting endothelial activation as a source of increased plasma PDI in MPN.

CONCLUSIONS

The observed association between plasma PDI levels and increased risk of TE in patients with JAK2-mutated MPN has both prognostic and therapeutic implications.

Small Molecule Kinase Inhibitor Drugs (1995-2021): Medical Indication, Pharmacology, and Synthesis

The central role of dysregulated kinase activity in the etiology of progressive disorders, including cancer, has fostered incremental efforts on drug discovery programs over the past 40 years. As a result, kinase inhibitors are today one of the most important classes of drugs. The FDA approved 73 small molecule kinase inhibitor drugs until September 2021, and additional inhibitors were approved by other regulatory agencies during that time. To complement the published literature on clinical kinase inhibitors, we have prepared a review that recaps this large data set into an accessible format for the medicinal chemistry community. Along with the therapeutic and pharmacological properties of each kinase inhibitor approved across the world until 2020, we provide the synthesis routes originally used during the discovery phase, many of which were only available in patent applications. In the last section, we also provide an update on kinase inhibitor drugs approved in 2021.

Carfilzomib Enhances the Suppressive Effect of Ruxolitinib in Myelofibrosis

As the first FDA-approved tyrosine kinase inhibitor for treatment of patients with myelofibrosis (MF), ruxolitinib improves clinical symptoms but does not lead to eradication of the disease or significant reduction of the mutated allele burden. The resistance of MF clones against the suppressive action of ruxolitinib may be due to intrinsic or extrinsic mechanisms leading to activity of additional pro-survival genes or signalling pathways that function independently of JAK2/STAT5. To identify alternative therapeutic targets, we applied a pooled-shRNA library targeting ~5000 genes to a JAK2^V617F-positive cell line under a variety of conditions, including absence or presence of ruxolitinib and in the presence of a bone marrow microenvironment-like culture medium. We identified several proteasomal gene family members as essential to HEL cell survival. The importance of these genes was validated in MF cells using the proteasomal inhibitor carfilzomib, which also enhanced lethality in combination with ruxolitinib. We also showed that proteasome gene expression is reduced by ruxolitinib in MF CD34⁺ cells and that additional targeting of proteasomal activity by carfilzomib enhances the inhibitory action of ruxolitinib in vitro. Hence, this study suggests a potential role for proteasome inhibitors in combination with ruxolitinib for management of MF patients.

Targets in MPNs and potential therapeutics

Philadelphia-negative classical Myeloproliferative Neoplasms (MPNs), including Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF), are clonal hemopathies that emerge in the hematopoietic stem cell (HSC) compartment. MPN driver mutations are restricted to specific exons (14 and 12) of Janus kinase 2 (JAK2), thrombopoietin receptor (MPL/TPOR) and calreticulin (CALR) genes, are involved directly in clonal myeloproliferation and generate the MPN phenotype. As a result, an increased number of fully functional erythrocytes, platelets and leukocytes is observed in the peripheral blood. Nevertheless, the complexity and heterogeneity of MPN clinical phenotypes cannot be solely explained by the type of driver mutation. Other factors, such as additional somatic mutations affecting epigenetic regulators or spliceosomes components, mutant allele burdens and modifiers of signaling by driver mutants, clonal architecture and the order of mutation acquisition, signaling events that occur downstream of a driver mutation, the presence of specific germ-line variants, the interaction of the neoplastic clone with bone marrow microenvironment and chronic inflammation, all can modulate the disease phenotype, influence the MPN clinical course and therefore, might be useful therapeutic targets.

PARP7 negatively regulates the type I interferon response in cancer cells and its inhibition triggers antitumor immunity

PARP7 is a monoPARP that catalyzes the transfer of single units of ADP-ribose onto substrates to change their function. Here, we identify PARP7 as a negative regulator of nucleic acid sensing in tumor cells. Inhibition of PARP7 restores type I interferon (IFN) signaling responses to nucleic acids in tumor models. Restored signaling can directly inhibit cell proliferation and activate the immune system, both of which contribute to tumor regression. Oral dosing of the PARP7 small-molecule inhibitor, RBN-2397, results in complete tumor regression in a lung cancer xenograft and induces tumor-specific adaptive immune memory in an immunocompetent mouse cancer model, dependent on inducing type I IFN signaling in tumor cells. PARP7 is a therapeutic target whose inhibition induces both cancer cell-autonomous and immune stimulatory effects via enhanced IFN signaling. These data support the targeting of a monoPARP in cancer and introduce a potent and selective PARP7 inhibitor to enter clinical development.

Ruxolitinib exposure in patients with acute and chronic graft versus host disease in routine clinical practice-a prospective single-center trial

Purpose

Knowledge on Ruxolitinib exposure in patients with graft versus host disease (GvHD) is scarce. The purpose of this prospective study was to analyze Ruxolitinib concentrations of GvHD patients and to investigate effects of CYP3A4 and CYP2C9 inhibitors and other covariates as well as concentration-dependent effects.

Methods

262 blood samples of 29 patients with acute or chronic GvHD who were administered Ruxolitinib during clinical routine were analyzed. A population pharmacokinetic model obtained from myelofibrosis patients was adapted to our population and was used to identify relevant pharmacokinetic properties and covariates on drug exposure. Relationships between Ruxolitinib exposure and adverse events were assessed.

Results

Median of individual mean trough serum concentrations was 39.9 ng/mL at 10 mg twice daily (IQR 27.1 ng/mL, range 5.6–99.8 ng/mL). Applying a population pharmacokinetic model revealed that concentrations in our cohort were significantly higher compared to myelofibrosis patients receiving the same daily dose (p < 0.001). Increased Ruxolitinib exposure was caused by a significant reduction in Ruxolitinib clearance by approximately 50%. Additional comedication with at least one strong CYP3A4 or CYP2C9 inhibitor led to a further reduction by 15% (p < 0.05). No other covariate affected pharmacokinetics significantly. Mean trough concentrations of patients requiring dose reduction related to adverse events were significantly elevated (p < 0.05).

Conclusion

Ruxolitinib exposure is increased in GvHD patients in comparison to myelofibrosis patients due to reduced clearance and comedication with CYP3A4 or CYP2C9 inhibitors. Elevated Ruxolitinib trough concentrations might be a surrogate for toxicity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-021-04351-w.

AXL Inhibition Represents a Novel Therapeutic Approach in BCR-ABL Negative Myeloproliferative Neoplasms

BCR-ABL negative myeloproliferative neoplasms (MPNs) consist of essential thrombocythemia, polycythemia vera, and myelofibrosis. The majority of patients harbor the JAK2-activating mutation V617F. JAK2 inhibitors were shown to reduce symptom burden and splenomegaly in MPN patients. However, treatment options are limited after failure of JAK2 inhibitors. AXL, a member of the TAM family of receptor tyrosine kinases, mediates survival and therapy resistance of different myeloid cancers including acute myeloid leukemia and chronic myeloid leukemia. We studied the relevance of AXL as a target in MPN using primary patient cells and preclinical disease models. We found that AXL is abundantly activated in MPN cells and that its ligand growth arrest-specific gene 6 is upregulated in MPN patients. Pharmacologic and genetic blockade of AXL impaired viability, decreased proliferation and increased apoptosis of MPN cells. Interestingly, ruxolitinib treatment induced increased phosphorylation of AXL indicating that activation of AXL might mediate resistance to ruxolitinib. Consistently, the AXL inhibitor bemcentinib exerted additive effects with ruxolitinib via impaired STAT3, STAT5, and AKT signaling. Both agents had activity when employed alone and exerted an additive effect on survival and splenomegaly in vivo. Moreover, bemcentinib treatment normalized red blood cell count and hemoglobin levels in vivo. Thus, our data indicate that AXL inhibition represents a novel treatment option in MPN warranting clinical investigation.

Structural Basis of Inhibition of DCLK1 by Ruxolitinib

Given the functional attributes of Doublecortin-like kinase 1 (DCLK1) in tumor growth, invasion, metastasis, cell motility, and tumor stemness, it is emerging as a therapeutic target in gastrointestinal cancers. Although a series of specific or nonspecific ATP-competitive inhibitors were identified against DCLK1, different types of scaffolds that can be utilized for the development of highly selective inhibitors or structural understanding of binding specificities of the compounds remain limited. Here, we present our work to repurpose a Janus kinase 1 inhibitor, ruxolitinib as a DCLK1 inhibitor, showing micromolar binding affinity and inhibitory activity. Furthermore, to gain an insight into its interaction mode with DCLK1, a crystal structure of the ruxolitinib-complexed DCLK1 has been determined and analyzed. Ruxolitinib as a nonspecific DCLK1 inhibitor characterized in this work is anticipated to provide a starting point for the structure-guided discovery of selective DCLK1 inhibitors.

Small molecule inhibition of deubiquitinating enzyme JOSD1 as a novel targeted therapy for leukemias with mutant JAK2

Mutations in the Janus Kinase 2 (JAK2) gene resulting in constitutive kinase activation represent the most common genetic event in myeloproliferative neoplasms (MPN), a group of diseases involving overproduction of one or more kinds of blood cells, including red cells, white cells, and platelets. JAK2 kinase inhibitors, such as ruxolitinib, provide clinical benefit, but inhibition of wild-type (wt) JAK2 limits their clinical utility due to toxicity to normal cells, and small molecule inhibition of mutated JAK2 kinase activity can lead to drug resistance. Here, we present a strategy to target mutated JAK2 for degradation, using the cell's intracellular degradation machinery, while sparing non-mutated JAK2. We employed a chemical genetics screen, followed by extensive selectivity profiling and genetic studies, to identify the deubiquitinase (DUB), JOSD1, as a novel regulator of mutant JAK2. JOSD1 interacts with and stabilizes JAK2-V617F, and inactivation of the DUB leads to JAK2-V617F protein degradation by increasing its ubiquitination levels, thereby shortening its protein half-life. Moreover, targeting of JOSD1 leads to the death of JAK2-V617F-positive primary acute myeloid leukemia (AML) cells. These studies provide a novel therapeutic approach to achieving selective targeting of mutated JAK2 signaling in MPN.

Transcriptomics-Based Phenotypic Screening Supports Drug Discovery in Human Glioblastoma Cells

Simple Summary

Glioblastoma (GBM) remains a particularly challenging cancer, with an aggressive phenotype and few promising treatment options. Future therapy will rely heavily on diagnosing and targeting aggressive GBM cellular phenotypes, both before and after drug treatment, as part of personalized therapy programs. Here, we use a genome-wide drug-induced gene expression (DIGEX) approach to define the cellular drug response phenotypes associated with two clinical drug candidates, the phosphodiesterase 10A inhibitor Mardepodect and the multi-kinase inhibitor Regorafenib. We identify genes encoding specific drug targets, some of which we validate as effective antiproliferative agents and combination therapies in human GBM cell models, including HMGCoA reductase (HMGCR), salt-inducible kinase 1 (SIK1), bradykinin receptor subtype B2 (BDKRB2), and Janus kinase isoform 2 (JAK2). Individual, personalized treatments will be essential if we are to address and overcome the pharmacological plasticity that GBM exhibits, and DIGEX will play a central role in validating future drugs, diagnostics, and possibly vaccine candidates for this challenging cancer.

Abstract

We have used three established human glioblastoma (GBM) cell lines—U87MG, A172, and T98G—as cellular systems to examine the plasticity of the drug-induced GBM cell phenotype, focusing on two clinical drugs, the phosphodiesterase PDE10A inhibitor Mardepodect and the multi-kinase inhibitor Regorafenib, using genome-wide drug-induced gene expression (DIGEX) to examine the drug response. Both drugs upregulate genes encoding specific growth factors, transcription factors, cellular signaling molecules, and cell surface proteins, while downregulating a broad range of targetable cell cycle and apoptosis-associated genes. A few upregulated genes encode therapeutic targets already addressed by FDA approved drugs, but the majority encode targets for which there are no approved drugs. Amongst the latter, we identify many novel druggable targets that could qualify for chemistry-led drug discovery campaigns. We also observe several highly upregulated transmembrane proteins suitable for combined drug, immunotherapy, and RNA vaccine approaches. DIGEX is a powerful way of visualizing the complex drug response networks emerging during GBM drug treatment, defining a phenotypic landscape which offers many new diagnostic and therapeutic opportunities. Nevertheless, the extreme heterogeneity we observe within drug-treated cells using this technique suggests that effective pan-GBM drug treatment will remain a significant challenge for many years to come.

Interleukin-27 promotes autophagy in human serum-induced primary macrophages via an mTOR- and LC3-independent pathway

Interleukin-27 (IL-27) is a cytokine that suppresses human immunodeficiency virus (HIV)-1 infection in macrophages and is considered as an immunotherapeutic reagent for infectious diseases. It is reported that IL-27 suppresses autophagy in Mycobacterium tuberculosis-infected macrophages; however, a role for IL-27 on autophagy induction has been less studied. In this study, we investigated the impact of IL-27 in both autophagy induction and HIV-1 infection in macrophages. Primary human monocytes were differentiated into macrophages using human AB serum (huAB) alone, macrophage-colony stimulating factor (M-CSF) alone, or a combination of IL-27 with huAB or M-CSF. Electron microscopy and immunofluorescence staining demonstrated that a 20-fold increase in autophagosome formation was only detected in IL-27 + huAB-induced macrophages. Western blot analysis indicated that the autophagosome induction was not linked to either dephosphorylation of the mammalian target of rapamycin (mTOR) or lipidation of microtubule-associated protein 1A/1B-light chain 3 (LC3), an autophagosomal marker, implying that IL-27 can induce autophagy through a novel non-canonical pathway. Here we show for the first time that IL-27 induces autophagy during monocyte-to-macrophage differentiation in a subtype-dependent manner.

The signal pathways and treatment of cytokine storm in COVID-19

The Coronavirus Disease 2019 (COVID-19) pandemic has become a global crisis and is more devastating than any other previous infectious disease. It has affected a significant proportion of the global population both physically and mentally, and destroyed businesses and societies. Current evidence suggested that immunopathology may be responsible for COVID-19 pathogenesis, including lymphopenia, neutrophilia, dysregulation of monocytes and macrophages, reduced or delayed type I interferon (IFN-I) response, antibody-dependent enhancement, and especially, cytokine storm (CS). The CS is characterized by hyperproduction of an array of pro-inflammatory cytokines and is closely associated with poor prognosis. These excessively secreted pro-inflammatory cytokines initiate different inflammatory signaling pathways via their receptors on immune and tissue cells, resulting in complicated medical symptoms including fever, capillary leak syndrome, disseminated intravascular coagulation, acute respiratory distress syndrome, and multiorgan failure, ultimately leading to death in the most severe cases. Therefore, it is clinically important to understand the initiation and signaling pathways of CS to develop more effective treatment strategies for COVID-19. Herein, we discuss the latest developments in the immunopathological characteristics of COVID-19 and focus on CS including the current research status of the different cytokines involved. We also discuss the induction, function, downstream signaling, and existing and potential interventions for targeting these cytokines or related signal pathways. We believe that a comprehensive understanding of CS in COVID-19 will help to develop better strategies to effectively control immunopathology in this disease and other infectious and inflammatory diseases.

Crucial role of hematopoietic JAK2 V617F in the development of aortic aneurysms

JAK2 V617F is the most frequent driver mutation in myeloproliferative neoplasms (MPN) and is associated with vascular complications. However, the impact of hematopoietic JAK2 V617F on aortic aneurysms (AA) remains unknown. Our cross-sectional study indicated that nine (23%) of 39 MPN patients with JAK2 V617F exhibited the presence of AA. In order to clarify whether the hematopoietic JAK2 V617F contributes to the AA, we applied bone marrow transplantation (BMT) with the donor cells from Jak2 V617F transgenic (JAK2^V617F) mice or control wild-type (WT) mice into lethally irradiated apolipoprotein E-deficient mice. Five weeks after BMT, the JAK2^V617F-BMT mice and WT-BMT mice were subjected to continuous angiotensin II infusion to induce AA formation. Four weeks after angiotensin II infusion, the abdominal aorta diameter in the JAK2^V617F-BMT mice was significantly enlarged compared to that in the WT-BMT mice. Additionally, the abdominal AA-free survival rate was significantly lower in the JAK2^V617F-BMT mice. Hematopoietic JAK2 V617F accelerated aortic elastic lamina degradation as well as activation of matrix metalloproteinase (MMP)-2 and MMP-9 in the abdominal aorta. The numbers of infiltrated macrophages were significantly upregulated in the abdominal aorta of the JAK2^V617F-BMT mice accompanied by STAT3 phosphorylation. The accumulation of BM-derived hematopoietic cells carrying JAK2 V617F in the abdominal aorta was confirmed by use of the reporter green fluorescent proteintransgene. BM-derived macrophages carrying JAK2 V617F showed increases in mRNA expression levels of Mmp2, Mmp9, and Mmp13. Ruxolitinib decreased the abdominal aorta diameter and the incidence of abdominal AA in the JAK2^V617F-BMT mice. Our findings provide a novel feature of vascular complications of AA in MPN with JAK2 V617F.

Uncoupling of IL-6 signaling and LC3-associated phagocytosis drives immunoparalysis during sepsis

Immune deactivation of phagocytes is a central event in the pathogenesis of sepsis. Herein, we identify a master regulatory role of IL-6 signaling on LC3-associated phagocytosis (LAP) and reveal that uncoupling of these two processes during sepsis induces immunoparalysis in monocytes/macrophages. In particular, we demonstrate that activation of LAP by the human fungal pathogen Aspergillus fumigatus depends on ERK1/2-mediated phosphorylation of p47phox subunit of NADPH oxidase. Physiologically, autocrine IL-6/JAK2/Ninein axis orchestrates microtubule organization and dynamics regulating ERK recruitment to the phagosome and LC3⁺ phagosome (LAPosome) formation. In sepsis, loss of IL-6 signaling specifically abrogates microtubule-mediated trafficking of ERK, leading to defective activation of LAP and impaired killing of bacterial and fungal pathogens by monocytes/macrophages, which can be selectively restored by IL-6 supplementation. Our work uncovers a molecular pathway linking IL-6 signaling with LAP and provides insight into the mechanisms underlying immunoparalysis in sepsis.

Pharmacokinetics of Ruxolitinib in Patients with Atopic Dermatitis Treated With Ruxolitinib Cream: Data from Phase II and III Studies

BACKGROUND

Pathogenesis of atopic dermatitis (AD) involves the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway. A cream formulation of ruxolitinib, a potent selective JAK1/JAK2 inhibitor, was developed for topical delivery.

METHOD

Pharmacokinetic data were obtained from three double-blind, vehicle-controlled studies in patients with AD: a phase II study with ruxolitinib cream 0.15%, 0.5%, or 1.5% once daily or 1.5% twice daily (BID), and two phase III studies with 0.75% or 1.5% BID. Effects of baseline characteristics on pharmacokinetics were examined. Correlations were attempted between plasma concentrations and change in hematological parameters over time.

RESULTS

Ruxolitinib plasma concentrations at steady-state (Css) increased with cream strength in a less-than-dose-proportional manner. In the phase III studies, overall mean (standard deviation [SD]) Css after ruxolitinib cream 0.75% and 1.5% BID (23.8 [35.0] and 35.7 [55.0] nM) were a fraction of the half-maximal inhibitory concentration for thrombopoietin-stimulated phosphorylated STAT3 inhibition (281 nM), a JAK/STAT signaling marker. Three covariates were identified for Css: dose, percent body surface area (%BSA) treated, and baseline Investigator's Global Assessment score. Mean (SD) bioavailability of ruxolitinib cream 1.5% BID was 6.22% (7.66%). There were no correlations between Css and any hematological changes except for a transient increase in platelets at week 2.

CONCLUSIONS

Plasma ruxolitinib concentrations after treatment with topical ruxolitinib cream in patients with up to 20% BSA affected by AD are not expected to lead to systemic plasma concentrations that may be associated with adverse effects commonly associated with oral JAK inhibitors. CLINICALTRIALS.GOV: NCT03011892; NCT03745638; NCT03745651.

Scaffold compound L971 exhibits anti-inflammatory activities through inhibition of JAK/STAT and NFκB signalling pathways

JAK/STAT and NFκB signalling pathways play essential roles in regulating inflammatory responses, which are important pathogenic factors of various serious immune-related diseases, and function individually or synergistically. To find prodrugs that can treat inflammation, we performed a preliminary high-throughput screening of 18 840 small molecular compounds and identified scaffold compound L971 which significantly inhibited JAK/STAT and NFκB driven luciferase activities. L971 could inhibit the constitutive and stimuli-dependent activation of STAT1, STAT3 and IκBα and could significantly down-regulate the proinflammatory gene expression in mouse peritoneal macrophages stimulated by LPS. Gene expression profiles upon L971 treatment were determined using high-throughput RNA sequencing, and significant differentially up-regulated and down-regulated genes were identified by DESeq analysis. The bioinformatic studies confirmed the anti-inflammatory effects of L971. Finally, L971 anti-inflammatory character was further verified in LPS-induced sepsis shock mouse model in vivo. Taken together, these data indicated that L971 could down-regulate both JAK/STAT and NFκB signalling activities and has the potential to treat inflammatory diseases such as sepsis shock.

Human Metapneumovirus Induces IRF1 via TANK-Binding Kinase 1 and Type I IFN

The innate immune and host-protective responses to viruses, such as the airway pathogen human metapneumovirus (HMPV), depend on interferons (IFNs) that is induced through TANK-binding kinase 1 (TBK1) and IFN regulatory factors (IRFs). The transcription factor IRF1 is important for host resistance against several viruses and has a key role in induction of IFN-λ at mucosal surfaces. In most cell types IRF1 is expressed at very low levels, but its mRNA is rapidly induced when the demand for IRF1 activity arises. Despite general recognition of the importance of IRF1 to antiviral responses, the molecular mechanisms by which IRF1 is regulated during viral infections are not well understood. Here we identify the serine/threonine kinase TBK1 and IFN-β as critical regulators of IRF1 mRNA and protein levels in human monocyte-derived macrophages. We find that inhibition of TBK1 activity either by the semi-selective TBK1/IKKε inhibitor BX795 or by siRNA-mediated knockdown abrogates HMPV-induced expression of IRF1. Moreover, we show that canonical NF-κB signaling is involved in IRF1 induction and that the TBK1/IKKε inhibitor BX795, but not siTBK1 treatment, impairs HMPV-induced phosphorylation of the NF-κB subunit p65. At later time-points of the infection, IRF1 expression depended heavily on IFN-β-mediated signaling via the IFNAR-STAT1 pathway. Hence, our results suggest that TBK1 activation and TBK1/IKKε-mediated phosphorylation of the NF-κB subunit p65 control transcription of IRF1. Our study identifies a novel mechanism for IRF1 induction in response to viral infection of human macrophages that could be relevant not only to defense against HMPV, but also to other viral, bacterial and fungal pathogens.

Signal transducer and activator of transcription (STAT) 1 and STAT3 are expressed in the human ovary and have Janus kinase 1-independent functions in the COV434 human granulosa cell line

Ovarian granulosa cells are fundamental for oocyte maintenance and maturation. Recent studies have demonstrated the importance of members of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signalling pathway in the granulosa cell population of mouse and horse ovaries, with perturbation of JAK1 signalling in the mouse shown to impair oocyte maintenance and accelerate primordial follicle activation. The presence and role of the JAK/STAT pathway in human granulosa cells has yet to be elucidated. In this study, expression of JAK1, STAT1 and STAT3 was detected in oocytes and granulosa cells of human ovarian sections from fetal (40 weeks gestation) and premenopausal ovaries (34-41 years of age; n=3). To determine the effects of JAK1 signalling in granulosa cells, the human granulosa-like cell line COV434 was used, with JAK1 inhibition using ruxolitinib. Chemical inhibition of JAK1 in COV434 cells with 100nM ruxolitinib for 72h resulted in significant increases in STAT3 mRNA (P=0.034) and p-Y701-STAT1 protein (P=0.0117), demonstrating a role for JAK1 in modulating STAT in granulosa cells. This study implicates a conserved role for JAK/STAT signalling in human ovary development, warranting further investigation of this pathway in human granulosa cell function.

Mixed results with baricitinib in biological-resistant adult-onset Still's disease and undifferentiated systemic autoinflammatory disease

This clinical case series describes our experience with the use of Janus kinase 1/2 inhibitor baricitinib in two patients suffering from refractory adult-onset Still’s disease (AOSD) as well as in one case suffering from AOSD-like autoinflammatory disease in the context of myelodysplastic syndrome. All patients suffered from disease non-responsive to conventional Disease-modifying antirheumatic drugs (DMARDs) as well as biological therapies including interleukin (IL)-1 and IL-6 blockade, relying instead on high daily doses of prednisolone. We also report the first case of Pneumocystis jirovecii infection following baricitinib use.

The Next Generation of JAK Inhibitors: an Update on Fedratinib, Momelotonib, and Pacritinib

PURPOSE OF REVIEW

Ruxolitinib is the first FDA-approved JAK inhibitor for the treatment of myeloproliferative neoplasms and is an effective means of controlling symptom burden and improving splenomegaly. However, a majority of patients will develop disease progression with long-term use. Fedratinib, momelotinib, and pacritinib are three newer-generation JAK inhibitors being prospectively evaluated and we will discuss their roles in the treatment of myeloproliferative neoplasms.

RECENT FINDINGS

Fedratinib has a role in both JAK-inhibitor naive intermediate-/high-risk myelofibrosis patients and in patients that have previously received ruxolitinib. It has recently received FDA approval for these indications as well. Momelotinib does not appear to have an advantage over ruxolitinib with regards to improving splenomegaly in intermediate-/high-risk JAK-inhibitor naive myelofibrosis. However, increased rates of transfusion independence have been noted with momelotinib. Pacritinib has been studied in myelofibrosis patients with significant baseline anemia and thrombocytopenia; these trials support the use of pacritinib in myelofibrosis patients with significant thrombocytopenia. While ruxolitinib is effective in reducing the symptom burden and splenomegaly of patients with myeloproliferative neoplasms, a majority of patients will ultimately progress on therapy. Newer-generation JAK inhibitors including fedratinib, momelotinib, and pacritinib are being prospectively evaluated to determine their appropriate roles in the management of myeloproliferative neoplasms. In addition, both combination therapies with JAK inhibitors and novel investigational therapies are being actively explored.

Clinical diagnostics and treatment strategies for Philadelphia chromosome-like acute lymphoblastic leukemia

Philadelphia chromosome-like B-cell acute lymphoblastic leukemia (Ph-like ALL) accounts for 15% to 30% of B-cell acute lymphoblastic leukemia in older children, adolescents, and adults and is associated with high rates of conventional treatment failure and relapse. Current clinical trials are assessing the efficacy of the addition of tyrosine kinase inhibitors (TKIs) to chemotherapy for children and adults with Ph-like ALL harboring ABL class translocations or CRLF2 rearrangements and other JAK pathway alterations. However, real-time diagnosis of patients can be quite challenging given the genetic heterogeneity of this disease and the often cytogenetically cryptic nature of Ph-like ALL-associated alterations. In this review, we discuss the complex biologic and clinical features of Ph-like ALL across the age spectrum, available diagnostic testing modalities, and current clinical treatment strategies for these high-risk patients. We further propose a practical and step-wise approach to Ph-like ALL genetic testing to facilitate the identification and allocation of patients to appropriate clinical trials of TKI-based therapies or commercially available drugs. Although the majority of patients with Ph-like ALL can be successfully identified via current clinical assays by the end of induction chemotherapy, increasing diagnostic efficiency and sensitivity and decreasing time to test resulting will facilitate earlier therapeutic intervention and may improve clinical outcomes for these high-risk patients.

Fedratinib in myelofibrosis

Following the discovery of the JAK2V617F mutation in myeloproliferative neoplasms in 2005, fedratinib was developed as a small molecular inhibitor of JAK2. It was optimized to yield low-nanomolar activity against JAK2 (50% inhibitory concentration = 3 nM) and was identified to be selective for JAK2 relative to other JAK family members (eg, JAK1, JAK3, and TYK2). It quickly moved into clinical development with a phase 1 clinical trial opening in 2008, where a favorable impact on spleen and myelofibrosis (MF) symptom responses was reported. A phase 3 trial in JAK2 inhibitor treatment-naive MF patients followed in 2011 (JAKARTA); a phase 2 trial in MF patients resistant or intolerant to ruxolitinib followed in 2012 (JAKARTA-2). Clinical development suffered a major setback between 2013 and 2017 when the US Food and Drug Administration (FDA) placed fedratinib on clinical hold due to the development of symptoms concerning for Wernicke encephalopathy (WE) in 8 of 608 subjects (1.3%) who had received the drug. It was ultimately concluded that there was no evidence that fedratinib directly induces WE, but clear risk factors (eg, poor nutrition, uncontrolled gastrointestinal toxicity) were identified. In August 2019, the FDA approved fedratinib for the treatment of adults with intermediate-2 or high-risk MF. Notably, approval includes a "black box warning" on the risk of serious and fatal encephalopathy, including WE. FDA approval was granted on the basis of the JAKARTA studies in which the primary end points (ie, spleen and MF symptom responses) were met in ∼35% to 40% of patients (JAKARTA) and 25% to 30% of patients (JAKARTA-2), respectively.

Combination Therapies in Chronic Myeloid Leukemia for Potential Treatment-Free Remission: Focus on Leukemia Stem Cells and Immune Modulation

Although tyrosine Kinase Inhibitors (TKI) has revolutionized the treatment of chronic myeloid leukemia (CML), patients are not cured with the current therapy modalities. Also, the more recent goal of CML treatment is to induce successful treatment-free remission (TFR) among patients achieving durable deep molecular response (DMR). Together, it is necessary to develop novel, curative treatment strategies. With advancements in understanding the biology of CML, such as dormant Leukemic Stem Cells (LSCs) and impaired immune modulation, a number of agents are now under investigation. This review updates such agents that target LSCs, and together with TKIs, have the potential to eradicate CML. Moreover, we describe the developing immunotherapy for controlling CML.

Generation of a chemical genetic model for JAK3

Janus Kinases (JAKs) have emerged as an important drug target for the treatment of a number of immune disorders due to the central role that they play in cytokine signalling. 4 isoforms of JAKs exist in mammalian cells and the ideal isoform profile of a JAK inhibitor has been the subject of much debate. JAK3 has been proposed as an ideal target due to its expression being largely restricted to the immune system and its requirement for signalling by cytokine receptors using the common γ-chain. Unlike other JAKs, JAK3 possesses a cysteine in its ATP binding pocket and this has allowed the design of isoform selective covalent JAK3 inhibitors targeting this residue. We report here that mutating this cysteine to serine does not prevent JAK3 catalytic activity but does greatly increase the IC50 for covalent JAK3 inhibitors. Mice with a Cys905Ser knockin mutation in the endogenous JAK3 gene are viable and show no apparent welfare issues. Cells from these mice show normal STAT phosphorylation in response to JAK3 dependent cytokines but are resistant to the effects of covalent JAK3 inhibitors. These mice therefore provide a chemical-genetic model to study JAK3 function.

Efficacy and safety of ruxolitinib cream for the treatment of atopic dermatitis: Results from 2 phase 3, randomized, double-blind studies

BACKGROUND

Ruxolitinib (RUX) cream demonstrated potent anti-inflammatory and antipruritic efficacy in a phase 2 study in adults with atopic dermatitis (AD).

OBJECTIVE

To evaluate 8-week efficacy and safety in 2 phase 3 studies of RUX cream in patients with AD.

METHODS

Topical Ruxolitinib Evaluation in Atopic Dermatitis Study 1 (NCT03745638) and Study 2 (NCT03745651) enrolled patients aged ≥12 years with AD for ≥2 years, an Investigator's Global Assessment score of 2/3, and 3%-20% affected body surface area. Patients were randomized 2:2:1 to twice-daily 0.75% RUX cream, 1.5% RUX cream, or vehicle cream for 8 continuous weeks. The primary endpoint was Investigator's Global Assessment treatment success at week 8 (Investigator's Global Assessment score of 0/1 and ≥2-grade improvement from baseline).

RESULTS

In the Topical Ruxolitinib Evaluation in Atopic Dermatitis Study 1 and 2, 631 and 618 patients were randomized (631/577 analyzed for efficacy). Significantly more patients achieved Investigator's Global Assessment treatment success with 0.75% RUX cream (50.0%/39.0%) and 1.5% RUX cream (53.8%/51.3%) versus vehicle (15.1%/7.6%; P < .0001) at week 8. Significant itch reductions versus vehicle were reported within 12 hours of first application of 1.5% RUX (P < .05). Application site reactions were infrequent (<1%) and lower with RUX versus vehicle; none were clinically significant.

LIMITATIONS

Longer-term safety data are not yet available.

CONCLUSIONS

RUX cream showed anti-inflammatory and prompt antipruritic effects with superior efficacy versus vehicle and was well tolerated.

The Natural Compound Notopterol Binds and Targets JAK2/3 to Ameliorate Inflammation and Arthritis

The traditional Chinese medicinal herb Notopterygium incisum Ting ex H.T. Chang has anti-rheumatism activity, and a mass spectrometry assay of patients' serum after administration of the herb revealed that notopterol is the most abundant component enriched. However, the functions of notopterol and its molecular target in rheumatoid arthritis (RA) treatment remain unknown. Here, we show in different RA mouse strains that both oral and intraperitoneal administration of notopterol result in significant therapeutic effects. Mechanistically, notopterol directly binds Janus kinase (JAK)2 and JAK3 kinase domains to inhibit JAK/signal transducers and activators of transcription (JAK-STAT) activation, leading to reduced production of inflammatory cytokines and chemokines. Critically, combination therapy using both notopterol and tumor necrosis factor (TNF) blocker results in enhanced therapeutic effects compared to using TNF blocker alone. We demonstrate that notopterol ameliorates RA pathology by targeting JAK-STAT signaling, raising the possibility that notopterol could be effective in treating other diseases characterized by aberrant JAK-STAT signaling pathway.

Activation of plasmacytoid dendritic cells promotes AML-cell fratricide

Acute myeloid leukemia (AML) is characterized by the proliferation of immature myeloid blasts and a suppressed immune state. Interferons have been previously shown to aid in the clearance of AML cells. Type I interferons are produced primarily by plasmacytoid dendritic cells (pDCs). However, these cells exist in a quiescent state in AML. Because pDCs express TLR 7–9, we hypothesized that the TLR7/8 agonist R848 would be able to reprogram them toward a more active, IFN-producing phenotype. Consistent with this notion, we found that R848-treated pDCs from patients produced significantly elevated levels of IFNβ. In addition, they showed increased expression of the immune-stimulatory receptor CD40. We next tested whether IFNβ would influence antibody-mediated fratricide among AML cells, as our recent work showed that AML cells could undergo cell-to cell killing in the presence of the CD38 antibody daratumumab. We found that IFNβ treatment led to a significant, IRF9-dependent increase in CD38 expression and a subsequent increase in daratumumab-mediated cytotoxicity and decreased colony formation. These findings suggest that the tolerogenic phenotype of pDCs in AML can be reversed, and also demonstrate a possible means of enhancing endogenous Type I IFN production that would promote daratumumab-mediated clearance of AML cells.

Ruxolitinib, a JAK1/2 Inhibitor, Ameliorates Cytokine Storm in Experimental Models of Hyperinflammation Syndrome

Hyperinflammatory syndromes comprise a heterogeneous group of disorders characterized by severe inflammation, multiple organ dysfunction, and potentially death. In response to antigenic stimulus (e.g., SARS-CoV-2 infection), overactivated CD8+ T-cells and macrophages produce high levels of proinflammatory cytokines, such as IFN-γ, TNF-α, IL-6, and IL-12. Multiple inflammatory mediators implicated in hyperinflammatory syndromes utilize the Janus kinase–signal transducers and activators of transcription (JAK-STAT) cascade to propagate their biological function. Our findings demonstrate that oral ruxolitinib dosing designed to mimic clinically relevant JAK-STAT pathway inhibition significantly reduces the harmful consequences of immune overactivation in multiple hyperinflammatory models. In contrast to monoclonal antibody therapies targeting a single cytokine, ruxolitinib effectively downregulates the functional effect of multiple cytokines implicated in hyperinflammatory states, without broad immunosuppression.