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Background and Purpose Experimental Approach Key Results Conclusion and Implications Pathological retinal angiogenesis is a typical manifestation of vision‐threatening ocular diseases. Many patients exhibit poor response or resistance to anti‐vascular endothelial growth factor (VEGF) agents. Bruton's tyrosine kinase (BTK) controls the proliferation and function of immune cells. Therefore, we examined the anti‐inflammatory and anti‐angiogenic effects of BTK inhibition on retinal angiogenesis.Retinal neovascularisation and vascular leakage in oxygen‐induced retinopathy in C57/BL6J mice were assessed by whole‐mount retinal immunofluorescence. PLX5622 was used to deplete microglia and Rag1‐knockout mice were used to test the contribution of lymphocytes to the effects of BTK inhibition. The cytokines, activation markers, inflammatory and immune‐regulatory activities of retinal microglia/macrophages were detected using qRT‐PCR and immunofluorescence. NLRP3 was detected by western blotting, and the effects of BTK inhibition on the co‐culture of microglia and human retinal microvascular endothelial cells (HRMECs) were examined.BTK inhibition suppressed pathological angiogenesis and vascular leakage, and significantly reduced retinal inflammation, which involved microglia/macrophages but not lymphocytes. BTK inhibition increased anti‐inflammatory factors and reduced pro‐inflammatory cytokines that resulted from NLRP3 inflammasome activation. BTK inhibition suppressed the inflammatory activity of microglia/macrophages, and acted synergistically with anti‐VEGF without retinal toxicity. Moreover, the supernatant of microglia incubated with BTK‐inhibitor reduced the proliferation, tube formation and sprouting of HRMECs.BTK inhibition suppressed retinal neovascularisation and vascular leakage by modulating the inflammatory activity of microglia and macrophages. Our study suggests BTK inhibition as a novel and promising approach for alleviating pathological retinal angiogenesis. [ABSTRACT FROM AUTHOR]

Activation of Bruton's tyrosine kinase (BTK) has been shown to play a crucial role in the proinflammatory response of B cells and myeloid cells upon engagement with B cell, Fc, Toll‐like receptor, and distinct chemokine receptors. Previous reports suggest BTK actively contributes to the pathogenesis of multiple sclerosis (MS). The BTK inhibitor Evobrutinib has been shown to reduce the numbers of gadolinium‐enhancing lesions and relapses in relapsing–remitting MS patients. In vitro, BTK inhibition resulted in reduced phagocytic activity and modulated BTK‐dependent inflammatory signaling of microglia and macrophages. Here, we investigated the protein expression of BTK and CD68 as well as iron accumulation in postmortem control (n = 10) and MS (n = 23) brain tissue, focusing on microglia and macrophages. MS cases encompassed active, chronic active, and inactive lesions. BTK+ and iron+ cells positively correlated across all regions of interests and, along with CD68, revealed highest numbers in the center of active and at the rim of chronic active lesions. We then studied the effect of BTK inhibition in the human immortalized microglia‐like HMC3 cell line in vitro. In particular, we loaded HMC3 cells with iron‐dextran and subsequently administered the BTK inhibitor Evobrutinib. Iron treatment alone induced a proinflammatory phenotype and increased the expression of iron importers as well as the intracellular iron storage protein ferritin light chain (FTL). BTK inhibition of iron‐laden cells dampened the expression of microglia‐related inflammatory genes as well as iron‐importers, whereas the iron‐exporter ferroportin was upregulated. Our data suggest that BTK inhibition not only dampens the proinflammatory response but also reduces iron import and storage in activated microglia and macrophages with possible implications on microglial iron accumulation in chronic active lesions in MS. [ABSTRACT FROM AUTHOR]

This open‐label, phase 1 study was conducted with healthy adult participants to evaluate the potential drug‐drug interaction between rilzabrutinib and quinidine (an inhibitor of P‐glycoprotein [P‐gp] and CYP2D6) or rifampin (an inducer of CYP3A and P‐gp). Plasma concentrations of rilzabrutinib were measured after a single oral dose of rilzabrutinib 400 mg administered on day 1 and again, following a wash‐out period, after co‐administration of rilzabrutinib and quinidine or rifampin. Specifically, quinidine was given at a dose of 300 mg every 8 hours for 5 days from day 7 to day 11 (N = 16) while rifampin was given as 600 mg once daily for 11 days from day 7 to day 17 (N = 16) with rilzabrutinib given in the morning of day 10 (during quinidine dosing) or day 16 (during rifampin dosing). Quinidine had no significant effect on rilzabrutinib pharmacokinetics. Rifampin decreased rilzabrutinib exposure (the geometric mean of Cmax and AUC0‐∞ decreased by 80.5% and 79.5%, respectively). Single oral doses of rilzabrutinib, with or without quinidine or rifampin, appeared to be well tolerated. These findings indicate that rilzabrutinib is a substrate for CYP3A but not a substrate for P‐gp. [ABSTRACT FROM AUTHOR]

Patients with central nervous system (CNS) lymphoma face limited treatment options and poor treatment outcomes, emphasizing the urgent need for effective therapeutic strategies. One limiting factor contributing to the suboptimal efficacy is the inadequate penetration of most treatment drugs across the blood–brain barrier (BBB). Recent insights into the pathophysiology of CNS lymphoma have identified the Bruton's tyrosine kinase (BTK) signaling pathway as a potential target. Some clinical trials have shown impressive responses to BTK inhibitors in CNS lymphoma. However, currently approved BTK inhibitors have low BBB penetration rates, limiting their efficacy. In this study, we discovered that JDB175, a novel and highly selective BTK inhibitor, exhibits excellent BBB penetration capabilities and demonstrates favorable activity in a mouse model of CNS lymphoma while showing no significant signs of toxicity. JDB175 effectively inhibits the BTK signaling pathway in human lymphoma cells, suppressing their proliferation, inducing cell cycle arrest, and promoting apoptosis. The significance of this study lies in addressing the critical unmet medical need for effective treatments for CNS lymphoma. This finding indicates a promising avenue for improved treatments in CNS lymphoma, potentially opening doors for further clinical investigation and therapeutic advancements. [ABSTRACT FROM AUTHOR]

Background: Despite advances in the treatment of chronic urticaria, in a significant percentage of the patients symptoms are not fully controlled with conventional approaches. New strategies under development include blocking intracellular mediators of mast cell and basophil activation. Objective: We aim to investigate the effects of the Bruton's tyrosine kinase (BTK) inhibitor remibrutinib on human blood basophils and CD34+‐derived mast cells activation induced by serum obtained from chronic urticaria patients. Methods: Twenty‐two patients with chronic spontaneous urticaria (mean age 52 years, 27% women) and 22 patients with chronic inducible urticaria (46 years, 27% women) were included in the study together with a sex‐matched control group. Patients were classified as responders or non‐responders to anti‐IgE therapy on the basis of their clinical data, FcεR1a expression on blood basophils and total IgE levels. Changes on CD63 expression—as an activation marker‐, were used to evaluate in vitro the response of basophils and mast cells to serum exposure and the inhibitory effects of remibrutinib. Results: Remibrutinib inhibits degranulation induced by IgE cross‐linking in mast cells and basophils and also the activation triggered by factors present in the sera of spontaneous and inducible chronic urticaria patients. Patient's serum induces a greater degranulation of effector cells than controls. Activation of mast cells and basophils by patient sera and remibrutinib effects were not related to omalizumab responsiveness. Conclusion: Remibrutinib inhibits activation of human basophils and mast cells induced in vitro by exposure to the serum of chronic urticaria patients independently of their response to omalizumab. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (BTK) is a TEC kinase with a multifaceted role in B‐cell biology and function, highlighted by its position as a critical component of the B‐cell receptor signalling pathway. Due to its role as a therapeutic target in several haematological malignancies including chronic lymphocytic leukaemia, BTK has been gaining tremendous momentum in recent years. Within the immune system, BTK plays a part in numerous pathways and cells beyond B cells (i.e. T cells, macrophages). Not surprisingly, BTK has been elucidated to be a driving factor not only in lymphoproliferative disorders but also in autoimmune diseases and response to infection. To extort this role, BTK inhibitors such as ibrutinib have been developed to target BTK in other diseases. However, due to rising levels of resistance, the urgency to develop new inhibitors with alternative modes of targeting BTK is high. To meet this demand, an expanding list of BTK inhibitors is currently being trialled. In this review, we synopsize recent discoveries regarding BTK and its role within different immune cells and pathways. Additionally, we discuss the broad significance and relevance of BTK for various diseases ranging from haematology and rheumatology to the COVID‐19 pandemic. Overall, BTK signalling and its targetable nature have emerged as immensely important for a wide range of clinical applications. The development of novel, more specific and less toxic BTK inhibitors could be revolutionary for a significant number of diseases with yet unmet treatment needs. [ABSTRACT FROM AUTHOR]

Bruton′s tyrosine kinase (Btk) is a crucial signaling molecule in BCR signaling and a key regulator of B‐ cell differentiation and function. Btk inhibition has shown impressive clinical efficacy in various B‐cell malignancies. However, it remains unknown whether inhibition additionally induces changes in BCR signaling due to feedback mechanisms, a phenomenon referred to as BCR rewiring. In this report, we studied the impact of Btk activity on major components of the BCR signaling pathway in mice. As expected, NF‐κB and Akt/S6 signaling was decreased in Btk‐deficient B cells. Unexpectedly, phosphorylation of several proximal signaling molecules, including CD79a, Syk, and PI3K, as well as the key Btk‐effector PLCγ2 and the more downstream kinase Erk, were significantly increased. This pattern of BCR rewiring was essentially opposite in B cells from transgenic mice overexpressing Btk. Importantly, prolonged Btk inhibitor treatment of WT mice or mice engrafted with leukemic B cells also resulted in increased phosho‐CD79a and phospho‐PLCγ2 in B cells. Our findings show that Btk enzymatic function determines phosphorylation of proximal and distal BCR signaling molecules in B cells. We conclude that Btk inhibitor treatment results in rewiring of BCR signaling, which may affect both malignant and healthy B cells. [ABSTRACT FROM AUTHOR]

BCP-ALL of the XLA patients did not show a distinctive methylation profile. X-linked agammaglobulinemia, Bruton's tyrosine kinase, acute lymphoblastic leukemia, acute megakaryoblastic leukemia, tumor suppressor Keywords: X-linked agammaglobulinemia; Bruton's tyrosine kinase; acute lymphoblastic leukemia; acute megakaryoblastic leukemia; tumor suppressor EN X-linked agammaglobulinemia Bruton's tyrosine kinase acute lymphoblastic leukemia acute megakaryoblastic leukemia tumor suppressor 1277 1281 5 06/18/21 20210615 NES 210615 X-linked agammaglobulinemia (XLA) is an inborn error of immunity caused by pathogenic variants in I Bruton's tyrosine kinase i ( I BTK i ). Future studies in which many patients with XLA with leukemia are enrolled may be able to clarify the more detailed characteristics of leukaemic cells in XLA. [Extracted from the article]

This multicenter, open‐label, phase I study assessed the safety and antitumor activity of acalabrutinib in Japanese patients with relapsed/refractory (r/r) B‐cell malignancies. Parts 1 (dose confirmation) and 2 (dose expansion) of this three‐part study are reported. Treatment was a single dose of 100 mg acalabrutinib (day 1), followed by a washout period and then twice daily 100 mg acalabrutinib in part 1, or twice daily 100 mg acalabrutinib in part 2. Patients from parts 1 and 2 with r/r chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), and r/r mantle cell lymphoma (MCL) were assessed as r/r CLL/SLL and r/r MCL cohorts, respectively. Twenty‐five patients received treatment (part 1, n = 6). Median age was 71.0 years. Nine (one patient from part 1) and 13 (two patients from part 1) patients were included in the r/r CLL/SLL and r/r MCL cohorts, respectively. Treatment‐related adverse events (AEs) occurred in 88% of patients (grade ≥3, 36%); the most common were headache (28%) and purpura (24%), both grade 1/2. No AEs resulted in treatment discontinuation or death. Median duration of treatment was 31, 20, and 7 months for part 1, r/r CLL/SLL cohort, and r/r MCL cohort, respectively. Overall response rate (ORR) was 89% and 62% for the r/r CLL/SLL and r/r MCL cohorts, respectively. The median progression‐free survival (PFS) was not reached for the r/r CLL/SLL cohort and was 7 months for the r/r MCL cohort. Acalabrutinib (100 mg twice daily) was generally safe and well‐tolerated in adult Japanese patients with B‐cell malignancies. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the safety, pharmacokinetics and pharmacodynamics of single‐ and multiple‐rising doses (MRDs) of BI 705564 and establish proof of mechanism. Methods: BI 705564 was studied in 2 placebo‐controlled, Phase I clinical trials testing single‐rising doses (1–160 mg) and MRDs (1–80 mg) of BI 705564 over 14 days in healthy male volunteers. Blood samples were analysed for BI 705564 plasma concentration, Bruton's tyrosine kinase (BTK) target occupancy (TO) and CD69 expression in B cells stimulated ex vivo. A substudy was conducted in allergic, otherwise healthy, MRD participants. Safety was assessed in both studies. Results: All doses of BI 705564 were well tolerated. Geometric mean BI 705564 plasma terminal half‐life ranged from 10.1 to 16.9 hours across tested doses, with no relevant accumulation after multiple dosing. Doses ≥20 mg resulted in ≥85% average TO that was maintained for ≥48 hours after single‐dose administration. Functional effects of BTK signalling were demonstrated by dose‐dependent inhibition of CD69 expression. In allergic participants, BI 705564 treatment showed a trend in wheal size reduction in a skin prick test and complete inhibition of basophil activation. Mild bleeding‐related adverse events were observed with BI 705564; bleeding time increased in 1/12 participants (8.3%) who received placebo vs 26/48 (54.2%) treated with BI 705564. Conclusion: BI 705564 showed efficient target engagement through durable TO and inhibition of ex vivo B‐cell activation, and proof of mechanism through effects on allergic skin responses. Mild bleeding‐related adverse events were probably related to inhibition of platelet aggregation by BTK inhibition. [ABSTRACT FROM AUTHOR]

Background and Purpose: There are no medications currently available to treat metabolic inflammation. Bruton's tyrosine kinase (BTK) is highly expressed in monocytes and macrophages and regulates NF-κB and NLRP3 inflammasome activity; both propagate metabolic inflammation in diet-induced obesity.Experimental Approach: Using an in vivo model of chronic inflammation, high-fat diet (HFD) feeding, in male C57BL/6J mice and in vitro assays in primary murine and human macrophages, we investigated if ibrutinib, an FDA approved BTK inhibitor, may represent a novel anti-inflammatory medication to treat metabolic inflammation.Key Results: HFD-feeding was associated with increased BTK expression and activation, which was significantly correlated with monocyte/macrophage accumulation in the liver, adipose tissue, and kidney. Ibrutinib treatment to HFD-fed mice inhibited the activation of BTK and reduced monocyte/macrophage recruitment to the liver, adipose tissue, and kidney. Ibrutinib treatment to HFD-fed mice decreased the activation of NF-κB and the NLRP3 inflammasome. As a result, ibrutinib treated mice fed HFD had improved glycaemic control through restored signalling by the IRS-1/Akt/GSK-3β pathway, protecting mice against the development of hepatosteatosis and proteinuria. We show that BTK regulates NF-κB and the NLRP3 inflammasome specifically in primary murine and human macrophages, the in vivo cellular target of ibrutinib.Conclusion and Implications: We provide "proof of concept" evidence that BTK is a novel therapeutic target for the treatment of diet-induced metabolic inflammation and ibrutinib may be a candidate for drug repurposing as an anti-inflammatory agent for the treatment of metabolic inflammation in T2D and microvascular disease. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (BTK) has a crucial role in multiple cell signaling pathways including B‐cell antigen receptor (BCR) and Fc receptor (FcR) signaling cascades, which has attracted much attention to find BTK inhibitors to treat autoimmune diseases. In this work, we constructed a Bayesian classification model for virtually seeking novel BTK inhibitors, which showed good performance in terms of screening efficiency and accuracy. Through searching for several chemical libraries including Chembl_17 (1,317,484 compounds), Chembridge (103,473 compounds), and Chemdiv (700,000 compounds) using this model followed by molecular docking and activity prediction, 52 compounds with novel scaffolds were acknowledged as potential BTK inhibitors, which could be promising starting points for further exploration. This study also provided a guide to construct an efficient and effective protocol for virtual screening by integrating machine learning methods. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (BTK) plays a central and pivotal role in controlling the pathways involved in the pathobiology of cancer, rheumatoid arthritis (RA), and other autoimmune disorders. ZYBT1 is a potent, irreversible, specific BTK inhibitor that inhibits the ibrutinib‐resistant C481S BTK with nanomolar potency. ZYBT1 is found to be a promising molecule to treat both cancer and RA. In the present report we profiled the molecule for in‐vitro, in‐vivo activity, and pharmacokinetic properties. ZYBT1 inhibits BTK and C481S BTK with an IC50 of 1 nmol/L and 14 nmol/L, respectively, inhibits the growth of various leukemic cell lines with IC50 of 1 nmol/L to 15 μmol/L, blocks the phosphorylation of BTK and PLCγ2, and inhibits secretion of TNF‐α, IL‐8 and IL‐6. It has favorable pharmacokinetic properties suitable for using as an oral anti‐cancer and anti‐arthritic drug. In accordance with the in‐vitro properties, it demonstrated robust efficacy in murine models of collagen‐induced arthritis (CIA) and streptococcal cell wall (SCW) induced arthritis. In both models, ZYBT1 alone could suppress the progression of the diseases. It also reduced the growth of TMD8 xenograft tumor. The results suggested that ZYBT1 has high potential for treating RA, and cancer. [ABSTRACT FROM AUTHOR]

Summary: Chronic lymphocytic leukaemia (CLL) cells are strongly influenced by microenvironmental signals through the activation of distinct membrane receptors including the B‐cell receptor and toll‐like receptors (TLR). Recapitulating TLR stimulation in vitro by treating CLL cells with the TLR9 ligand CpG can induce metabolic activation and protection from apoptosis. We hypothesized that interfering with TLR signalling may be beneficial for treating CLL, and we tested in preclinical studies the effect of a specific interleukin‐1 receptor‐associated kinase 4 (IRAK4) inhibitory small molecule on primary leukaemic cells isolated from the peripheral blood of patients. We observed that IRAK4, an upstream kinase of the TLR pathway, is expressed in patients with CLL, and lower IRAK4 mRNA levels associate with a better outcome. The specific IRAK4 inhibitor disrupted TLR signalling as assessed by reduction of the specific biomarkers NFKBIZ and interleukin‐6 mRNAs, and restrained the protective effect of in vitro TLR stimulation on cell viability. To note, IRAK4 inhibitor induced p53 and triggered apoptosis. Co‐treatment of CLL cells with increasing concentrations of IRAK4i and the Bruton tyrosine kinase inhibitor ibrutinib demonstrated a synergistic effect. Our results suggest that targetting IRAK4 may represent a novel approach in CLL and may be combined with other signalling inhibitors. [ABSTRACT FROM AUTHOR]

The Bruton's tyrosine kinase inhibitor ibrutinib abrogates bispecific antibody-mediated T-cell cytotoxicity Keywords: acute leukaemia; bispecific antibody; Bruton's tyrosine kinase; ibrutinib; IL-2-inducible T-cell kinase EN acute leukaemia bispecific antibody Bruton's tyrosine kinase ibrutinib IL-2-inducible T-cell kinase e9 e13 5 03/31/20 20200401 NES 200401 Bispecific antibodies (BiAbs) have emerged as promising therapeutics for haematologic malignancies, with the CD19/CD3 Bispecific T-cell Engager blinatumomab approved for patient application and many more investigational agents in clinical testing (Viardot & Bargou, [15]). On the other hand, also recently reported in this journal, broad-spectrum tyrosine kinase inhibitors can acutely abrogate cytotoxicity of T-cell-directed BiAbs and CAR T-cells I in vitro i (Fasslrinner I et al. i , [6]). BiAb-mediated T-cell cytotoxicity depends on both T-cell and tumour cell factors (Viardot & Bargou, [15]). [Extracted from the article]

Uremic pruritus with elevated levels of calcium phosphate (CaP) in skin is a common symptom in patients with chronic kidney disease (CKD). In this study, we demonstrate that intradermal injection of CaP into mice triggered scratching by up-regulating the IL-6 in skin and phosphorylation of ERKs in dorsal root ganglion (DRG) in a dose-dependent manner. IL-6 is essential because the CaP-induced up-regulation of phosphorylated (p)-ERK in DRG was considerably reduced in the IL-6 knockout mice. Microarray analysis in conjunction with real-time PCR revealed a higher mRNA expression of Bruton's tyrosine kinase (BTK) gene in DRG after CaP injection. The inhibition of BTK by ibrutinib noticeably diminish the CaP-induced up-regulation of IL-6 and p-ERK in mice. A high amount of IL-6 was detected in itchy skin and blood of patients with CKD. The expressions of p-BTK and p-ERK in DRG primary cells reached maximum levels at 1 and 10 min, respectively, after treatment of recombinant IL-6 and were significantly reduced by treatment of IL-6 along with ibrutinib. The mechanism by which the CaP-induced pruritus mediated by the IL-6/p-BTK/p-ERK signaling was revealed. [ABSTRACT FROM AUTHOR]

As a cytoplasmic protein tyrosine kinase, Bruton's tyrosine kinase (Btk) is widely considered as a vital kinase in many aspects of different physiologic processes. It is engaged in many important signalling pathways related to the immune response, such as the B cell receptor pathway, pattern‐recognition receptor pathway, and triggering receptor expressed on myeloid cell pathway. Recent studies have increasingly focused on the important role of Btk in various inflammatory diseases, which are related to Btk expression in myeloid innate immune cells, such as macrophages, dendritic cells and neutrophils. Although some investigations have explored the role of Btk in microbial infections, many aspects remain elusive, and some of the results are opposite and controversial. Considering the complicated and multiple roles of Btk in the immune system, we summarized the engagement of Btk signalling in various pathogenic microorganism infections, the possible mechanisms involved and its therapeutic potential in the control of infectious diseases. [ABSTRACT FROM AUTHOR]

Background: Periodontitis is not only one of the most prevalent inflammatory diseases among adults, but also commonly linked to numerous systemic conditions including cardiovascular diseases, stroke, and diabetes. Although osteoclasts are responsible for the alveolar bone resorption during periodontitis pathogenesis, the development of pharmacologic strategies targeting these cells has not been vastly fruitful.Methods: Bone marrow macrophages were cultured in the presence of macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL) to examine the direct effect of acalabrutinib on osteoclastogenesis. Ca2+ oscillation and nuclear localization of NFATc1 in osteoclast precursors were examined to determine the precise molecular mechanism. LPS-induced alveolar bone loss model was employed for studying effect in in vivo bone resorption.Results: Acalabrutinib directly inhibited RANKL and LPS-induced in vitro osteoclast differentiation. In addition, acalabrutinib inhibited RANKL-induced phosphorylation of mitogen-activated protein kinases and reduced the expression of NF-κB. The inhibitory mechanism involved suppression of Ca2+ oscillation in osteoclast precursors resulting in the decreased NFATc1 expression and nuclear localization, which is a crucial prerequisite for osteoclastogenesis. The administration of acalabrutinib significantly reduced P. gingivalis lipopolysaccharide-induced alveolar bone erosion in mice.Conclusion: These data indicate that acalabrutinib is an effective inhibitor of osteoclastogenesis both in vitro and in vivo, with a potential for a novel strategy against bone destruction by periodontitis. [ABSTRACT FROM AUTHOR]

Aim To evaluate the safety, tolerability, and pharmacokinetics/pharmacodynamics of PRN1008, a novel Bruton's tyrosine kinase (BTK) inhibitor, in healthy volunteers, and thus determine the dose range for future clinical studies. Methods This was a two-part randomized, placebo controlled study in healthy volunteers using a liquid formulation. Part I was a single ascending dose design with dose levels of 50-1200 mg ( n = 6 active, two placebos per cohort); Part II was a multiple ascending dose design, with dose regimens ranging from 300 to 900 mg daily, either four times or twice daily for 10 days. Plasma pharmacokinetics, adverse events, vital signs, electrocardiograms and laboratory parameters were assessed. BTK occupancy in peripheral blood mononuclear cells was evaluated as a marker of target engagement. Results PRN1008 was rapidly absorbed following oral administration, and was safe and well tolerated in all dose regimens evaluated in both single and multiple doses. PRN1008 demonstrated a large volume of distribution, and a half-life of approximately 3-4 h. BTK occupancy of >90% was observed within 4 h after dosing in both single and multiple dose regimens, and was closely linked to maximum plasma concentration. BTK occupancy decay was slow (-1.6% h-1), and occupancy was sustained despite drug concentrations being undetectable. No severe or serious adverse events occurred, and the most common adverse events were gastrointestinal in nature. Conclusions PRN1008 was safe and well-tolerated following oral administration, and achieved high, sustained levels of BTK occupancy in peripheral blood mononuclear cells. [ABSTRACT FROM AUTHOR]

High-grade transformation of chronic lymphocytic leukaemia [Richter syndrome (RS)] is rare and represents a unique and uncommon clinical challenge. Clonally related diffuse large B cell type RS is a chemotherapy-resistant and devastating disease. Patients are typically elderly, immunosuppressed and present with a rapidly deteriorating performance status. Historical outcomes suggest a median overall survival of approximately 8 months. RS remains is an area of high unmet clinical need. The molecular profile and treatment needs of patients are likely to change over time with the advent of novel B cell receptor inhibitors, monoclonal antibodies and BH3 mimetics. Herein, we summarise what is known regarding the molecular drivers of RS and the existing clinical trial data, including the recently published CHOP- OR (cyclophosphamide, doxorubicin, vincristine, prednisolone and ofatumumab followed by ofatumumab maintenance in newly diagnosed RS) trial. We discuss novel agents in development with a focus on the second-generation Bruton tyrosine kinase inhibitor acalabrutinib, checkpoint inhibition and the potential role of precision medicine in future trials of RS. [ABSTRACT FROM AUTHOR]

The article presents a study regarding design and synthesis of novel pyrazolo[3,4-d]pyrimidin-1-yl piperidine derivatives as bruton's tyrosine kinase (BTK) inhibitors. Topics discussed include a novel series of pyrazolopyrimidine scaffold which have sulfone linkage to diphenyl moiety exhibits potent inhibitory activity almost equivalent to ibrutinib toward BTK enzyme and displayed potent antiproliferative activity in TMD8 cell-based assay.

The article presents a study of chronic lymphocytic leukaemia patients treated with ibrutinib below the U.S. Food and Drug Administration-recommended starting dose to compare efficacy between the various dosing schedules. Topics discussed include the lack of significant differences in baseline characteristics between the standard-dose and reduced dose cohorts and reasons for ibrutinib dose reduction including gastrointestinal toxicity, bleeding and pharmacokinetic considerations.

Aims Ibrutinib, an inhibitor of Bruton's tyrosine kinase, is used in the treatment of mantle cell lymphoma or chronic lymphocytic leukaemia. Ibrutinib undergoes extensive rapid oxidative metabolism mediated by cytochrome P450 3A both at the level of first pass and clearance, which might result in low oral bioavailability. The present study was designed to investigate the absolute bioavailability (F) of ibrutinib in the fasting and fed state and assess the effect of grapefruit juice (GFJ) on the systemic exposure of ibrutinib in order to determine the fraction escaping the gut (Fg) and the fraction escaping hepatic extraction (Fh) in the fed state. Methods All participants received treatment A [560 mg oral ibrutinib, under fasting conditions], B (560 mg PO ibrutinib, fed, administered after drinking glucose drink) and C (140 mg oral ibrutinib, fed, with intake of GFJ before dosing). A single intravenous (i.v.) dose of 100 μg 13C6-ibrutinib was administered 2 h after each oral dose. Results The estimated 'F' for treatments A, B and C was 3.9%, 8.4% and 15.9%, respectively. Fg and Fh in the fed state were 47.0% and 15.9%, respectively. Adverse events were mild to moderate in severity (Grade 1-2) and resolved without sequelae by the end of the study. Conclusion The absolute oral bioavailability of ibrutinib was low, ranging from 3.9% in the fasting state to 8.4% when administered 30 min before a standard breakfast without GFJ and 15.9% with GFJ. Ibrutinib was well tolerated following a single oral and i.v. dose, under both fasted and fed conditions and regardless of GFJ intake status. [ABSTRACT FROM AUTHOR]

Plasmacytoid dendritic cells (PDCs) represent a key cell type for both innate and adaptive immunity. PDCs express both TLR7 and TLR9 and the recognition of nucleic acids by these two receptors triggers the production of a large amount of type-I IFN and the induction of PDC maturation into APCs. This unique feature of PDCs is at the basis of clinical development of both TLR7 and TLR9 agonists for infectious diseases, allergy, cancer, and asthma. However, TLR7 and TLR9 recognition of self-nucleic acids is linked to many autoimmune diseases including lupus, and a better understanding of the signaling pathways of these two receptors in PDCs is thus important. We have identified Bruton's tyrosine kinase (Btk) as an important player for TLR9 but not TLR7 signaling in human PDCs. Blocking Btk using a specific inhibitor leads to the reduction of all TLR9-induced responses in PDCs, including cytokine production and expression of costimulatory molecules, while this has no impact on the TLR7 response. This identifies Btk as a key molecule in TLR9 signaling in PDCs and is the first demonstration that the TLR7 and TLR9 pathways can be dissociated in human PDCs. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase has emerged as a potential target for the treatment for B-cell malignancies and autoimmune diseases. Discovery of Bruton's tyrosine kinase inhibitors has thus attracted much attention recently. In this investigation, we introduced a hybrid protocol of virtual screening methods including support vector machine model-based virtual screening, pharmacophore model-based virtual screening and docking-based virtual screening for retrieving new Bruton's tyrosine kinase inhibitors from commercially available chemical databases. Performances of the hybrid virtual screening approach were evaluated against a test set, which results showed that the hybrid virtual screening approach significantly shortened the overall screening time, and considerably increased the hit rate and enrichment factor compared with the individual method (SB-VS, PB-VS and DB-VS) or their combinations by twos. This hybrid virtual screening approach was then applied to screen several chemical databases including Specs (202 408 compounds) and Enamine (980 000 compounds) databases. Thirty-nine compounds were selected from the final hits and have been shifted to experimental studies. [ABSTRACT FROM AUTHOR]

The control of cellular signaling cascades is of utmost importance in regulating the immune response. Exquisitely precise protein–protein interactions and chemical modification of substrates by enzymatic catalysis are the fundamental components of the signals that alert immune cells to the presence of a foreign antigen. In particular, the phosphorylation events induced by protein kinase activity must be spatially and temporally regulated by specific interactions to maintain a normal and effective immune response. High resolution structures of many protein kinases along with supporting biochemical data are providing significant insight into the intricate regulatory mechanisms responsible for controlling cellular signaling. The Tec family kinases are immunologically important kinases for which regulatory details are beginning to emerge. This review focuses on bringing together structural insights gained over the years to develop an understanding of how domain interactions both within the Tec kinases and between the Tec kinases and other signaling molecules control immune cell function. [ABSTRACT FROM AUTHOR]

Mast cell mediator release represents a pivotal event in the initiation of inflammatory reactions associated with allergic disorders. These responses follow antigen-mediated aggregation of immunoglobulin E (IgE)-occupied high-affinity receptors for IgE (FcεRI) on the mast cell surface, a response which can be further enhanced following stem cell factor-induced ligation of the mast cell growth factor receptor KIT (CD117). Activation of tyrosine kinases is central to the ability of both FcεRI and KIT to transmit downstream signaling events required for the regulation of mast cell activation. Whereas KIT possesses inherent tyrosine kinase activity, FcεRI requires the recruitment of Src family tyrosine kinases and Syk to control the early receptor-proximal signaling events. The signaling pathways propagated by these tyrosine kinases can be further upregulated by the Tec kinase Bruton’s tyrosine kinase and downregulated by the actions of the tyrosine Src homology 2 domain-containing phosphatase 1 (SHP-1) and SHP-2. In this review, we discuss the regulation and role of specific members of this tyrosine kinase network in KIT and FcεRI-mediated mast cell activation. [ABSTRACT FROM AUTHOR]

Background: X-linked agammaglobulinemia (XLA), characterized by the early onset of recurrent bacterial infections, profound hypogammaglobulinemia, and a markedly diminished number of peripheral B lymphocytes, is caused by mutations in the Bruton’s tyrosine kinase ( BTK) gene. The >600 unique mutations identified to date include single base pair substitutions, small insertions or deletions, and gross deletions. A few cases, however, have been found to have no mutations in the coding region even with reduced BTK mRNA or protein expression. Mutations in intron 1 positions +5 (G→A) and +6 (T→G) of the BTK gene have been identified, and these changes were associated with reduced transcriptional activity. Methods: In the present study a novel mutation in intron 1 position +5 (G→T) was identified in a Japanese patient with XLA. The reporter constructs containing these mutations were made, and the reporter activities were measured using a luciferase assay. Results: All the mutant constructs were demonstrated to have reduced transcriptional activity. Conclusions: Positions +5 and +6 in intron 1 of the BTK gene are critical for transcriptional activity, and defects in these regions cause XLA. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (Btk), a member of the Tec family of tyrosine kinases, plays an important role in the differentiation and activation of B cells. Mutations affecting Btk cause immunodeficiency in both humans and mice. In this study we set out to investigate the potential role of Btk in Toll-like receptor 9 (TLR9) activation and the production of pro-inflammatory cytokines such as interleukin (IL)-6, tumour necrosis factor (TNF)-α and IL-12p40. Our data show that Btk-deficient B cells respond more efficiently to CpG-DNA stimulation, producing significantly higher levels of pro-inflammatory cytokines but lower levels of the inhibitory cytokine IL-10. The quantitative reverse transcription–polymerase chain reaction (RT-PCR) analysis presented in this work shows that mRNA production of one of the important new members of the IL-12 family, IL-27, was significantly increased in Btk-deficient B cells after CpG-DNA stimulation. In this study, we demonstrate significant differences in CpG responsiveness between transitional 1 (T1) and T2 B cells for survival and maturation. Furthermore, TLR9 expression, measured both as protein and as mRNA, was increased in Btk-defective cells, especially after TLR9 stimulation. Collectively, these data provide evidence in support of the theory that Btk regulates both TLR9 activation and expression in mouse splenic B cells. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (BTK) was previously demonstrated to be a mediator of oxidative stress-induced apoptosis in irradiated neoplastic B-cells and B-cell precursors. Defective BTK expression in leukaemic B-cell precursors from infants with t(4;11) acute lymphoblastic leukaemia has been associated with radiation resistance. The present study examined whether BTK mediates apoptosis during oxidative stress by interfering with the anti-apoptotic function of signal transducer and activator of transcription 3 (STAT3). BTK physically associated with and tyrosine phosphorylated STAT3; this association was promoted by pervanadate (PV)-induced oxidative stress. The BTK/STAT3 interaction appeared to prevent STAT3 response to oxidative stress, because PV-induced STAT3 activation was markedly enhanced in DT40 chicken lymphoma B-cells that were rendered BTK-deficient by targeted disruption of the btk gene as well as in BTK-deficient RAMOS-1 human lymphoma B-cells. These BTK-deficient cells were highly resistant to oxidative stress-induced apoptosis triggered by PV treatment. Reconstitution of BTK-deficient DT40 cells with wild-type human BTK gene eliminated the amplification of the STAT3 response and restored the PV-induced apoptotic signal. Similarly, while the BTK-positive NALM-6 human leukaemic B-cell precursor cell line showed no STAT3 activation after PV treatment and was exquisitely sensitive to PV-induced apoptosis, PV failed to induce apoptosis in BTK-deficient RAMOS-1 human lymphoma B-cells that showed a robust STAT3 response. These results provide unprecedented biochemical and genetic evidence for a unique mode of cross-talk that occurs between BTK and STAT3 pathways during oxidative stress, whereby BTK may trigger apoptosis via negative regulation of the anti-apoptotic STAT3 activity. [ABSTRACT FROM AUTHOR]

A 5-yr-old Caucasian boy with a new mutation in Bruton's tyrosine kinase (BTK) is described. Full sequencing of the BTK gene revealed a point mutation in exon 17 resulting in an amino acid change from tryptophan to serine at location 581 of the tyrosine kinase domain. Clinically the child presented with chronic gingivitis and had no prior history of bacterial infections. Whereas serum immunoglobulin M (IgM) levels were undetectable, IgG levels were in the low normal range. The gingivitis completely resolved after intravenous immunoglobulin therapy. Lymphocyte phenotyping revealed 0.05% B cells in his peripheral blood, which were IgG−, IgM+, IgD+, CD38+, CD20+, CD27−. However, 40% of the B cells also expressed CD5. This subpopulation of B cells has not previously been described in X-linked agammaglobulinaemia (XLA) patients. We suggest that the occurrence of CD5+ B cells could correlate with a late onset and mild clinical presentations of XLA. [ABSTRACT FROM AUTHOR]

Abstract: Drosophila type 2 Btk29A reveals the highest homology to Btk among mammalian Tec kinases. In Btk29A ficP mutant males, the apodeme holding the penis split into two pieces. Human Btk rescued this phenotype in 39% of Btk29A ficP males, while the Drosophila transgenes did so in 90–100% of mutants. The Btk29A ficP mutation reduced adult longevity to 11% that of wild-type. This effect was counteracted by Drosophila type 2, yielding 76% of the wild-type lifespan. Human Btk extended the lifespan of Btk29A ficP mutants only to 20% that of wild-type. Thus human Btk can partially replace Drosophila Btk29A + in male genital development and survival. [Copyright &y& Elsevier]

X-linked agammaglobulinaemia (XLA) is a primary immunodeficiency caused by mutations in the gene coding for Bruton's tyrosine kinase (Btk) and is characterized by an arrest of B-cell development. We analysed Btk protein expression in platelets using flow cytometry and found that normal platelets express large amounts of Btk. Assessment of affected males from 45 unrelated XLA families revealed that platelets of the majority of the patients (37 out of 45 families) had decreased or absent Btk expression, and that platelets from carrier females of these families had both normal and mutated Btk expression, indicating that megakaryocytes in XLA carriers undergo random X-chromosome inactivation. These observations demonstrate that Btk is not crucial for maturation of megakaryocytes and the production of platelets. No correlation between Btk expression in platelets and clinical phenotype was observed in this study. Flow cytometric evaluation using platelets is a simple and rapid method to test Btk expression. It may be used as a screening test for XLA and for carrier detection, followed, if necessary, by more expensive mutation analyses. [ABSTRACT FROM AUTHOR]

Objective: Molecular analysis of the Bruton’s tyrosine kinase (Btk) gene in two unrelated families, with a combined total of seven boys, affected by X-linked agammaglobulinaemia (XLA). Methods: Protein electrophoresis and western blotting were used for the examination of Btk protein synthesis in blood leucocytes. Isolation of the coding sequence of the Btk gene was performed by amplification using the reverse transcription–polymerase chain reaction (RT-PCR) technique. Sequence alterations were screened for by the single-stranded conformation polymorphism (SSCP) method and characterized by standard sequencing protocols. Results: Western blotting revealed Btk protein to be absent in leucocytes of affected males from both families. A novel 3 b.p. deletion in exon 3 of the Btk gene was found to be responsible for the XLA phenotype in the affected proband in one family (kindred I). A diagnostic PCR assay was established to detect this mutation in other affected male siblings and carrier females. For the second family (kindred II), the coding sequence of the Btk gene and the promoter region were found to be normal. Conclusions: The present study has demonstrated genetic heterogeneity in the Btk gene in South African XLA patients and has identified a novel mutation in this gene in the largest of the affected kindreds. The gene mutation in the second kindred was undetermined and may be indicative of a defect in some other gene associated with Btk function or stability. Western blotting was found to be informative in establishing a deficiency of Btk protein in both probands and is recommended as a frontline procedure in the molecular diagnosis and work-up of XLA. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (Btk) is a non-receptor protein tyrosine kinase (PTK) that is expressed in all haemopoietic lineages except mature T cells and plasma cells. Despite the broad range of expression, mutations that inactivate this molecule affect primarily the development of the B-cell lineage. As a PTK, Btk could potentially be involved directly or indirectly in the processes that relate to the malignant transformation of all the cell lineages where this molecule is expressed. Previous studies have failed to demonstrate mutations in patients with B-cell origin acute lymphoblastic leukaemia (ALL). We have utilized a recently developed method that enables the rapid and convenient detection of mutations at the cDNA level, namely, the non-isotopic RNase cleavage assay (NIRCA) to analyse Btk sequences from 27 patients with different types of acute myeloid leukaemia (AML). The only alteration that we observed was a polymorphism at position 2031. This polymorphism has already been seen in previous studies. Furthermore, using the same methodology, we identified the Btk mutations in six XLA (X-linked agammaglobulinaemia) patients. Our results, although they do not exclude the involvement of Btk mutations in the development or progression of some type of AML, nevertheless suggest that such mutations do not constitute a major co-factor in the development of myeloid malignancies. [ABSTRACT FROM AUTHOR]