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Introduction: The history of treating chronic lymphocytic leukemia (CLL) inflected in 2014 with the Food and Drug Administration's (FDA) approval of ibrutinib, the first-in-class small molecule inhibitor of the Bruton's tyrosine kinase (BTK). Zanubrutinib is a 2nd generation covalent BTK inhibitor developed and manufactured by BeiGene. Areas covered: In this review, the authors trace the arc of zanubrutinib development from the preclinical phase through the two landmark phase 3 studies in the CLL space, ALPINE and SEQUOIA. The authors cover contemporary management strategies in CLL and highlight the areas of need that zanubrutinib was designed to mitigate. Expert opinion: Zanubrutinib entered a fray of novel, exciting therapies for CLL. As the second of two 2nd generation covalent BTK inhibitors its path to prominence in CLL management was narrow. Emphasis during development on kinase selectivity and enhanced bioavailability identified a molecule with superior efficacy and tolerability; hierarchical endpoints in trial design allowed for efficient acquisition of comparative data. Zanubrutinib is endorsed by the National Comprehensive Cancer Network as a preferred, category 1 recommended treatment choice for CLL. Future efforts in combination therapies and response-directed treatment breaks will hopefully lead to still further improvements in use. [ABSTRACT FROM AUTHOR]

Simple Summary: High overall response rates with durable remissions have led to most patients with chronic lymphocytic leukemia being treated sequentially with covalent Bruton's tyrosine kinase inhibitors and the B-cell lymphoma-2 inhibitor venetoclax as their first- and second-line therapies. Chronic lymphocytic leukemia remains a largely incurable disease, and double refractory patients will ultimately require additional treatment options. The non-covalent Bruton's tyrosine kinase inhibitor pirtobrutinib, as well as the chimeric antigen receptor T-cell therapy lisocabtagene maraleucel, are currently available treatment options for double refractory patients with chronic lymphocytic leukemia. There are additional treatment options currently in clinical development to treat double refractory patients, including bi-specific antibodies, second-generation B-cell lymphoma-2 inhibitors, additional non-covalent Bruton's tyrosine kinase inhibitors, and Bruton's tyrosine kinase degraders. Understanding resistance mechanisms to existing treatments can offer insight into a personalized approach to the treatment of double refractory chronic lymphocytic leukemia. The proliferation and survival of chronic lymphocytic leukemia (CLL) cells are heavily dependent on B-cell receptor (BCR) signaling and resistance to apoptosis. Approvals of multiple covalent Bruton's tyrosine kinas inhibitors (cBTKis) as well as the B-cell lymphoma-2 inhibitor (BCL2i) venetoclax targeting these pathways have revolutionized the treatment of CLL and small lymphocytic lymphoma (SLL). The superiority of these treatments over chemoimmunotherapy has been proven in phase III studies in both treatment-naïve and relapsed refractory settings, leading to the majority of patients with CLL being treated sequentially with cBTKis and the BCL2i venetoclax as their first- and second-line therapies. While most patients with CLL respond for many years to these sequenced treatments, they are unfortunately not curative. There remains an unmet need for effective treatment options for patients who progressed after treatment with both cBTKis and BCL2i, also referred to as double refractory patients. Treatment options for double refractory CLL has improved recently with the approval of the non-covalent BTK inhibitor (ncBTKi) pirtobrutinib as well as the CD19 targeted chimeric antigen receptor T-cell (CAR T-cell) therapy lisocabtagene maraleucel (liso-cel). These recently approved treatment options for patients with CLL with at least two prior lines of therapy have fortunately demonstrated efficacy for double refractory CLL. Additionally, there are several novel treatment options in clinical development, including bi-specific antibodies, second-generation BCL2is, new ncBTKis, and BTK degraders. Understanding resistance mechanisms to existing cBTKis and venetoclax can potentially inform us of the best utilization of available treatment options for double refractory CLL and provide a personalized approach for these patients. In this review, a challenging example of a double refractory patient with CLL will serve as the basis for a review of available literature on the treatment of double refractory CLL/SLL. [ABSTRACT FROM AUTHOR]

Simple Summary: Bruton's tyrosine kinase inhibitors (BTKi) have revolutionized the treatment of various B-cell lymphoid malignancies. However, acquisition of resistance to BTKi has emerged as an important clinical challenge. Herein, we provide a detailed review, describing the clinical trials that led to the FDA approval of the BTK inhibitors for management of Chronic Lymphocytic Leukemia (CLL), Mantle Cell Lymphoma, Marginal Zone Lymphoma (MZL), Follicular Lymphoma (FL) and Waldenstrom Macroglobulinemia (WM). We describe the mechanism of intrinsic and extrinsic resistance to the BTKi with main emphasis on the functional description of BTK mutations in CLL. Finally, we review the latest updates of the PROTACs BTK degraders, an evolving treatment modality for the management of the BTKi refractory B-cell malignancies. B-cell lymphoid malignancies are a heterogeneous group of hematologic cancers, where Bruton's tyrosine kinase (BTK) inhibitors have received FDA approval for several subtypes. The first-in-class covalent BTK inhibitor, Ibrutinib, binds to the C481 amino acid residue to block the BTK enzyme and prevent the downstream signaling. Resistance to covalent BTK inhibitors (BTKi) can occur through mutations at the BTK binding site (C481S) but also other BTK sites and the phospholipase C gamma 2 (PLCγ2) resulting in downstream signaling. To bypass the C481S mutation, non-covalent BTKi, such as Pirtobrutinib, were developed and are active against both wild-type and the C481S mutation. In this review, we discuss the molecular and genetic mechanisms which contribute to acquisition of resistance to covalent and non-covalent BTKi. In addition, we discuss the new emerging class of BTK degraders, which utilize the evolution of proteolysis-targeting chimeras (PROTACs) to degrade the BTK protein and constitute an important avenue of overcoming resistance. The moving landscape of resistance to BTKi and the development of new therapeutic strategies highlight the ongoing advances being made towards the pursuit of a cure for B-cell lymphoid malignancies. [ABSTRACT FROM AUTHOR]

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]

Considering the second-highest global death rate, Colorectal Cancer (CRC) is the second most prevalent form of cancer in women and the third most frequent cancer type in men. Bruton's Tyrosine Kinase (BTK) is a soluble tyrosine kinase that plays essential functions in B cell maturation, development, and signaling. It has been discovered that BTK controls cell migration, survival, and proliferation in a variety of B-cell malignancies. The category of short non-coding RNAs known as microRNAs (miRNAs) is involved in several biological processes, including the development and propagation of tumors. The current study was designed to measure the gene expression level of the BTK gene and miR-4516 in Iraqi CRC patients; 100 blood samples were collected, RNA extracted, converted into cDNA, and then expression levels were measured using quantitative real-time PCR. The results showed that there were statistically significant differences among the patients and the control with a P-value (=0.005) in the expression level of miR-4516, while the results of the BTK gene showed that there were no significant differences between the CRC patients and control groups of the current study. This study reveals that non-detectable levels of BTK secretion may be attributed to miR-4516 mediated suppression or due to BTK possessing a dual role in tumorigenesis, capable of either promoting tumor growth or inducing programmed cell death. Elevated levels of miR-4516 are believed to contribute to the development of CRC by regulating the expression of specific genes, including BTK, making it a promising target for both monitoring and therapeutic of the disease.

Abstract Bruton’s tyrosine kinase (BTK), a nonreceptor tyrosine kinase, plays a remarkable role in the transmission and amplification of extracellular signals to intracellular signaling pathways. Various types of cells use the BTK pathway to communicate, including hematopoietic cells particularly B cells and T cells. The BTK pathway plays a role in controlling the proliferation, survival, and functions of B cells as well as other myeloid cells. First, second, and third-generation BTK inhibitors are currently being evaluated for the treatment of immune-mediated diseases in addition to B cell malignancies. In this article, the available evidence on the action mechanisms of BTK inhibitors is reviewed. Then, the most recent data obtained from preclinical studies and ongoing clinical trials for the treatment of autoimmune diseases, such as pemphigus vulgaris, pemphigus foliaceus, bullous pemphigoid, systemic lupus erythematosus, Sjögren’s disease, rheumatoid arthritis, systemic sclerosis, multiple sclerosis, myasthenia gravis, and inflammatory diseases such as psoriasis, chronic spontaneous urticaria, atopic dermatitis, and asthma are discussed. In addition, adverse effects and complications associated with BTK inhibitors as well as factors predisposing patients to BTK inhibitors complications are discussed.

Introduction: In X-linked agammaglobulinemia (XLA), the diversity of BTK variants complicates the study of genotype-phenotype correlations. Since BTK negatively regulates toll-like receptors (TLRs), we investigated if distinct BTK mutation types selectively modulate TLR pathways, affecting disease expression. Methods: Using reverse transcription-quantitative polymerase chain reaction, we quantified ten TLR signaling-related genes in XLA patients with missense (n = 3) and nonsense (n = 5) BTK mutations and healthy controls (n = 17). Results: BTK, IRAK2, PIK3R4, REL, TFRC, and UBE2N were predominantly downregulated, while RIPK2, TLR3, TLR10, and TLR6 showed variable regulation. The missense XLA group exhibited significant downregulation of IRAK2, PIK3R4, REL, and TFRC and upregulation of TLR3 and/or TLR6. Conclusion: Hypo-expression of TLR3, TLR6, and TLR10 may increase susceptibility to infections, while hyper-expression might contribute to chronic inflammatory conditions like arthritis or inflammatory bowel disease. Our findings shed light on the important inflammatory component characteristic of some XLA patients, even under optimal therapeutic conditions.

Introduction: Bruton's tyrosine kinase (BTK) and interleukin (IL)-2 Inducible Tcell Kinase (ITK) inhibitors have anti-inflammatory properties. We investigated the therapeutic effect of ibrutinib, an orally bioavailable BTK/ITK inhibitor, in a mouse model of Graves' orbitopathy (GO). Methods: Genetic immunization was performed through intramuscular administration of the recombinant plasmid, pCMV6-hTSHR cDNA, to 8-weekold female BALB/c mice. Serum levels of T3, T4, and thyroid-stimulating hormone receptor (TSHR) antibodies (TRAbs) were quantified using enzymelinked immunosorbent assay. Histopathological changes in orbital tissues were examined using immunohistochemistry (IHC) staining for TSHR and various inflammatory markers. Following successful genetic immunization, ibrutinib was orally administered daily for 2 weeks in the GO model mice. After treatment, the mRNA and protein expression levels of BTK, ITK, IL-1b, and IL-6 in orbital tissues were evaluated using real-time PCR and Western blotting. Results: In total, 20 mice were sacrificed to confirm successful genetic immunization. The GO mouse group exhibited significantly increased serum T3, T4, and TRAb levels. IHC revealed increased expression of TSHR, IL-1b, IL-6, transforming growth factor-b1, interferon-g, CD40, CD4, BTK, and ITK in the GO mouse model. The orbital inflammation was significantly attenuated in ibrutinibtreated mice. The mRNA and protein expression levels of BTK, ITK, IL-1b, and IL-6 in orbital tissue were lower in ibrutinib-treated GO mouse group compared to the phosphate-buffered saline-treated GO mouse group. Conclusion: The GO mouse model demonstrated enhanced BTK and ITK expression. Ibrutinib, a BTK/ITK inhibitor, suppressed the inflammatory cytokine production. These findings highlight the potential involvement of BTK/ITK in the inflammatory pathogenesis of GO, suggesting its role as a novel therapeutic target. [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]

Obesity is associated with metabolic inflammation, which can contribute to insulin resistance, higher blood glucose, and higher insulin indicative of prediabetes progression. The nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is a metabolic danger sensor implicated in metabolic inflammation. Many features of metabolic disease can activate the NLRP3 inflammasome; however, it is not yet clear which upstream triggers to target, and there are no clinically approved NLRP3 inflammasome inhibitors for metabolic disease. Bruton's tyrosine kinase (BTK) mediates activation of the NLRP3 inflammasome. Ibrutinib is the most-studied pharmacological inhibitor of BTK, and it can improve blood glucose control in obese mice. However, inhibitors of tyrosine kinases are permissive, and it is unknown if BTK inhibitors require BTK to alter endocrine control of metabolism or metabolic inflammation. We tested whether ibrutinib and acalabrutinib, a new generation BTK inhibitor with higher selectivity, require BTK to inhibit the NLRP3 inflammasome, metabolic inflammation, and blood glucose in obese mice. Chronic ibrutinib administration lowered fasting blood glucose and improved glycemia, whereas acalabrutinib increased fasting insulin levels and increased markers of insulin resistance in high-fat diet-fed CBA/J mice with intact Btk. These metabolic effects of BTK inhibitors were absent in CBA/CaHN-Btkxid/J mice with mutant Btk. However, ibrutinib and acalabrutinib reduced NF-κB activity, proinflammatory gene expression, and NLRP3 inflammasome activation in macrophages with and without functional BTK. These data highlight that the BTK inhibitors can have divergent effects on metabolism and separate effects on metabolic inflammation that can occur independently of actions on BTK. NEW & NOTEWORTHY: Bruton's tyrosine kinase (BTK) is involved in immune function. It was thought that BTK inhibitors improve characteristics of obesity-related metabolic disease by lowering metabolic inflammation. However, tyrosine kinase inhibitors are permissive, and it was not known if different BTK inhibitors alter host metabolism or immunity through actions on BTK. We found that two BTK inhibitors had divergent effects on blood glucose and insulin via BTK, but inhibition of metabolic inflammation occurred independently of BTK in obese mice. [ABSTRACT FROM AUTHOR]

This review provides a comprehensive examination of ibrutinib (Ibr), highlighting its wide-ranging utilization in the treatment of diverse malignancies and its potential as a viable target for solid tumor therapy on account of its ability to inhibit numerous kinases, such as Bruton's tyrosine kinase (BTK), which is an essential component of the B-cell receptor signaling pathway and the microenvironment of cancer. The attention is directed toward the most recent developments in nanotechnology and its growing impact on the transformation of cancer therapeutics. The article examines the potential of nanotechnology in advancing approaches to enhance the efficacy of cancer treatments, overcome drug resistance, and enable the development of novel immunotherapies. An in-depth investigation into novel approaches, including nanoencapsulation and nanocarrier-mediated delivery, reveals their potential contributions to improving the therapeutic results of Ibr. The review is situated within a multidisciplinary framework. It highlights the potential uses of these emerging nanotechnological approaches to address obstacles, minimize adverse effects, and counteract potential resistance associated with Ibr treatment. This highlights nanotechnology's profound potential in precision oncology, particularly in enhancing the therapeutic environment for hematologic cancers. [ABSTRACT FROM AUTHOR]

One of the most successful and highly developed drug targets in cancer is Bruton's tyrosine kinase (BTK). Remarkable basic and translational studies have led to the clinical approval of several generations of small-molecule BTK inhibitors. Recent discovery of kinase-deficient BTK inhibitor resistance mutations sheds light on still undiscovered roles of BTK in B cell receptor signaling. Noncovalent BTK inhibitors represent potential future frontline treatment options in chronic lymphocytic leukemia (CLL). New dual-binding BTK inhibitors and BTK degraders represent the future of BTK targeting. Successful development of BTK inhibitors in cancer has led to new applications in other conditions such as autoimmune disease. Bruton's tyrosine kinase (BTK) inhibitors have revolutionized the treatment landscape for B cell lymphomas such as chronic lymphocytic leukemia (CLL). The first-in-class BTK inhibitor ibrutinib has recently been succeeded by covalent BTK inhibitors that are safer but still face challenges of resistance mutations. The noncovalent BTK inhibitor pirtobrutinib was recently approved for relapsed and refractory CLL, and whether noncovalent BTK inhibitors will supplant covalent BTK inhibitors as upfront treatment options either alone or in combination will be determined. Meanwhile, newer BTK inhibitors and BTK degraders are vying for their place in the potential future landscape of B cell cancers as well as autoimmune diseases. This review will cover the latest progress in BTK inhibitor development and where the field is moving in light of these recent discoveries. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (BTK) is pivotal in B-cell signaling and a target for potential anti-cancer and immunological disorder therapies. Improved selective reversible BTK inhibitors are in demand due to the absence of direct BTK engagement measurement tools. Promisingly, PET imaging can non-invasively evaluate BTK expression. In this study, radiolabeled BIO-2008846 ([11C]BIO-2008846-A), a BTK inhibitor, was used for PET imaging in NHPs to track brain biodistribution. Radiolabeling BIO-2008846 with carbon-11, alongside four PET scans on two NHPs each, showed a homogeneous distribution of [11C]BIO-2008846-A in NHP brains. Brain uptake ranged from 1.8% ID at baseline to a maximum of 3.2% post-pretreatment. The study found no significant decrease in regional VT values post-dose, implying minimal specific binding of [11C]BIO-2008846-A compared to free and non-specific components in the brain. Radiometabolite analysis revealed polar metabolites with 10% unchanged radioligand after 30 min. The research highlighted strong brain uptake despite minor distribution variability, confirming passive diffusion kinetics dominated by free and non-specific binding. [ABSTRACT FROM AUTHOR]

Inhibition of Bruton’s tyrosine kinase (BTK) has proven to be highly effective in the treatment of B-cell malignancies such as chronic lymphocytic leukemia (CLL), autoimmune disorders, and multiple sclerosis. Since the approval of the first BTK inhibitor (BTKi), Ibrutinib, several other inhibitors including Acalabrutinib, Zanubrutinib, Tirabrutinib, and Pirtobrutinib have been clinically approved. All are covalent active site inhibitors, with the exception of the reversible active site inhibitor Pirtobrutinib. The large number of available inhibitors for the BTK target creates challenges in choosing the most appropriate BTKi for treatment. Side-by-side comparisons in CLL have shown that different inhibitors may differ in their treatment efficacy. Moreover, the nature of the resistance mutations that arise in patients appears to depend on the specific BTKi administered. We have previously shown that Ibrutinib binding to the kinase active site causes unanticipated long-range effects on the global conformation of BTK (Joseph et al., 2020). Here, we show that binding of each of the five approved BTKi to the kinase active site brings about distinct allosteric changes that alter the conformational equilibrium of full-length BTK. Additionally, we provide an explanation for the resistance mutation bias observed in CLL patients treated with different BTKi and characterize the mechanism of action of two common resistance mutations: BTK T474I and L528W.

The discovery of the role of Bruton’s Tyrosine Kinase (BTK) in inflammation and autoimmunity has recently led to the development of BTK inhibitors for the treatment of autoimmune diseases, including pemphigus vulgaris. We herein present the case of a patient affected by pemphigus vulgaris, refractory to conventional immunosuppressive therapies and to multiple courses of rituximab, who was treated with rilzabrutinib and achieved disease control, but whose immunological profile switched from pemphigus vulgaris to pemphigus foliaceus after drug discontinuation. Furthermore, we review the literature in order to better characterize the phenotypic transitions from pemphigus vulgaris to pemphigus foliaceus reported so far. The factors underlying this transition are largely unknown, although it has been postulated that immunosuppressive therapies may be more effective against anti-desmoglein 3 antibodies compared to anti-desmoglein 1. However, further studies are needed to better define the effect of rilzabrutinib (and immunosuppressive therapies in general) on anti-desmoglein 1 and anti-desmoglein 3 antibodies.

BACKGROUND: Primary immunodeficiency diseases (PIDDs) are clinically and immunologically diverse and require a wide array of clinical and laboratory modalities to make specific diagnosis. Serum immunoglobulin levels and T cell, B cell and NK (Natural killer) cell immunophenotyping are routine laboratory investigations advised to diagnose the PIDD cases in Bangladesh. Along with T-B-NK markers, use of Naïve (CD45RA+) and memory (CD45RO+) T cell, switched memory B cell (CD27+IgD-) markers, detection of intracellular BTK (Bruton’s tyrosine kinase), LRBA (Lipopolysaccharide-responsive beige-like anchor), DOCK8 (Dedicator of cytokinesis 8) protein expression and DHR123 (Dihydro-rhodamine 123) assay of neutrophil can increase the PIDD cases detection in Bangladesh. METHODS: The study was conducted in the Department of Microbiology and Immunology, Bangabandhu Sheikh Mujib Medical University (BSMMU) during the time period of March, 2021 to February, 2022. Seventy clinically suspected PIDD cases were enrolled in this study on the basis of clinical findings and peripheral venous blood was collected from all patients to perform immunophenotyping. Routine T-B-NK cell, naïve and memory T cell with switched memory B cell markers were detected by flow-cytometry. Serum immunoglobulins (IgG, IgM, IgA & IgE) were estimated by Nephelometry and by Chemiluminescence. Intracellular BTK, LRBA and DOCK8 protein expression was detected by flow-cytometry in suspected X-linked agammaglobulinemia (XLA), LRBA and DOCK8 deficiency patients respectively. DHR123 assay was performed in suspected Chronic granulomatous disease (CGD) patients. RESULTS: Among the 70 clinically suspected PIDD cases, 9 (12.9%) were diagnosed as patients of PIDDs on the basis of laboratory evidence. Five (55.55%) cases were diagnosed as predominantly antibody deficiencies (PADs), 3 (33.33%) were patients of combined immunodeficiency (CID) and 1 (11.11%) was CGD patient. Among the diagnosed PIDD cases, 2 (22.22%) were diagnosed by T-B-NK cell immunophenotyping with serum immunoglobulin levels and 7 (77.77%) cases were diagnosed by additional CD45RA+, CD45RO+, CD27+IgD- markers, BTK protein expression detection and DHR123 assay. LRBA and DOCK8 deficiency cases could not found in this study. CONCLUSION: The use of additional markers (CD45RA+, CD45RO+, CD27+IgD-) with BTK, LRBA, DOCK8 intracellular protein expression evaluation and DHR123 assay by flow-cytometry can increase rate of specific diagnosis of the PIDD cases in Bangladeshi paediatric population.

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]

Background: Evobrutinib – an oral, central nervous system (CNS)-penetrant, and highly selective Bruton's tyrosine kinase inhibitor – has shown efficacy in a 48-week, double-blind, Phase II trial in patients with relapsing MS. Objective: Report results of the Phase II open-label extension (OLE; up to week 192 from randomisation) and a cerebrospinal fluid (CSF) sub-study. Methods: In the 48-week double-blind period (DBP), patients received evobrutinib 25 mg once-daily, 75 mg once-daily, 75 mg twice-daily or placebo (switched to evobrutinib 25 mg once-daily after week 24). Patients could then enter the OLE, receiving evobrutinib 75 mg once-daily (mean (± standard deviation (SD)) duration = 50.6 weeks (±6.0)) before switching to 75 mg twice-daily. Results: Of 164 evobrutinib-treated patients who entered the OLE, 128 (78.0%) completed ⩾192 weeks of treatment. Patients receiving DBP evobrutinib 75 mg twice-daily: annualised relapse rate at week 48 (0.11 (95% confidence interval (CI) = 0.04-0.25)) was maintained with the OLE twice-daily dose up to week 192 (0.11 (0.05–0.22)); Expanded Disability Status Scale score remained stable; serum neurofilament light chain fell to levels like a non-MS population (Z -scores); T1 gadolinium-enhancing lesion numbers remained low. No new safety signals were identified. In the OLE, evobrutinib was detected in the CSF of all sub-study patients. Conclusion: Long-term evobrutinib treatment was well tolerated and associated with a sustained low level of disease activity. Evobrutinib was present in CSF at concentrations similar to plasma. [ABSTRACT FROM AUTHOR]

Bruton’s tyrosine kinase (BTK) is a key protein in B cell antigen receptor (BCR) signaling pathway, and is a research hotspot in the clinical treatment of B cell tumors and B cell immune diseases. In this article, based on the structure of Ibrutinib, a series of novel irreversible BTK inhibitors with the scaffolding of 1H-pyrazolo [3, 4-d] pyrimidin-4-amine were designed and synthesized. All the compounds showed a moderate to potent inhibitory activity against BTK. Among them, compound 6b showed the best BTK kinase inhibitory activity with the IC50 value of 1.2 nM. The ADME/T properties performed by pkCSM demonstrated that compound 6b possesses a good druglikeness. Further druggability evaluation showed that 6b exhibited good water solubility and acceptable pharmacokinetic properties. Therefore, compound 6b provided a promising lead compound for developing novel irreversible BTK inhibitors.

Abstract Background Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory autoimmune disease of the central nervous system that involves B-cell receptor signaling as well as astrocyte–microglia interaction, which both contribute to evolution of NMOSD lesions. Main body Through transcriptomic and flow cytometry analyses, we found that Bruton’s tyrosine kinase (BTK), a crucial protein of B-cell receptor was upregulated both in the blood and cerebrospinal fluid of NMOSD patients. Blockade of BTK with zanubrutinib, a highly specific BTK inhibitor, mitigated the activation and maturation of B cells and reduced production of causal aquaporin-4 (AQP4) autoantibodies. In a mouse model of NMO, we found that both BTK and pBTK expression were significantly increased in microglia. Transmission electron microscope scan demonstrated that BTK inhibitor ameliorated demyelination, edema, and axonal injury in NMO mice. In the same mice colocalization of GFAP and Iba-1 immunofluorescence indicated a noticeable increase of astrocytes–microglia interaction, which was alleviated by zanubrutinib. The smart-seq analysis demonstrated that treatment with BTK inhibitor instigated microglial transcriptome changes including downregulation of chemokine-related genes and genes involved in the top 5 biological processes related to cell adhesion and migration, which are likely responsible for the reduced crosstalk of microglia and astrocytes. Conclusions Our results show that BTK activity is enhanced both in B cells and microglia and BTK inhibition contributes to the amelioration of NMOSD pathology. These data collectively reveal the mechanism of action of BTK inhibition and corroborate BTK as a viable therapeutic target.

BACKGROUND: Primary immunodeficiency diseases (PIDDs) are clinically and immunologically diverse and require a wide array of clinical and laboratory modalities to make specific diagnosis. Serum immunoglobulin levels and T cell, B cell and NK (Natural killer) cell immunophenotyping are routine laboratory investigations advised to diagnose the PIDD cases in Bangladesh. Along with T-B-NK markers, use of Naïve (CD45RA+) and memory (CD45RO+) T cell, switched memory B cell (CD27+IgD-) markers, detection of intracellular BTK (Bruton's tyrosine kinase), LRBA (Lipopolysaccharide-responsive beige-like anchor), DOCK8 (Dedicator of cytokinesis 8) protein expression and DHR123 (Dihydro-rhodamine 123) assay of neutrophil can increase the PIDD cases detection in Bangladesh. METHODS: The study was conducted in the Department of Microbiology and Immunology, Bangabandhu Sheikh Mujib Medical University (BSMMU) during the time period of March, 2021 to February, 2022. Seventy clinically suspected PIDD cases were enrolled in this study on the basis of clinical findings and peripheral venous blood was collected from all patients to perform immunophenotyping. Routine T-B-NK cell, naïve and memory T cell with switched memory B cell markers were detected by flow-cytometry. Serum immunoglobulins (IgG, IgM, IgA & IgE) were estimated by Nephelometry and by Chemiluminescence. Intracellular BTK, LRBA and DOCK8 protein expression was detected by flow-cytometry in suspected X-linked agammaglobulinemia (XLA), LRBA and DOCK8 deficiency patients respectively. DHR123 assay was performed in suspected Chronic granulomatous disease (CGD) patients. RESULTS: Among the 70 clinically suspected PIDD cases, 9 (12.9%) were diagnosed as patients of PIDDs on the basis of laboratory evidence. Five (55.55%) cases were diagnosed as predominantly antibody deficiencies (PADs), 3 (33.33%) were patients of combined immunodeficiency (CID) and 1 (11.11%) was CGD patient. Among the diagnosed PIDD cases, 2 (22.22%) were diagnosed by T-B-NK cell immunophenotyping with serum immunoglobulin levels and 7 (77.77%) cases were diagnosed by additional CD45RA+, CD45RO+, CD27+IgD- markers, BTK protein expression detection and DHR123 assay. LRBA and DOCK8 deficiency cases could not found in this study. CONCLUSION: The use of additional markers (CD45RA+, CD45RO+, CD27+IgD-) with BTK, LRBA, DOCK8 intracellular protein expression evaluation and DHR123 assay by flow-cytometry can increase rate of specific diagnosis of the PIDD cases in Bangladeshi paediatric population. [ABSTRACT FROM AUTHOR]

Background: Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory autoimmune disease of the central nervous system that involves B-cell receptor signaling as well as astrocyte–microglia interaction, which both contribute to evolution of NMOSD lesions. Main body: Through transcriptomic and flow cytometry analyses, we found that Bruton's tyrosine kinase (BTK), a crucial protein of B-cell receptor was upregulated both in the blood and cerebrospinal fluid of NMOSD patients. Blockade of BTK with zanubrutinib, a highly specific BTK inhibitor, mitigated the activation and maturation of B cells and reduced production of causal aquaporin-4 (AQP4) autoantibodies. In a mouse model of NMO, we found that both BTK and pBTK expression were significantly increased in microglia. Transmission electron microscope scan demonstrated that BTK inhibitor ameliorated demyelination, edema, and axonal injury in NMO mice. In the same mice colocalization of GFAP and Iba-1 immunofluorescence indicated a noticeable increase of astrocytes–microglia interaction, which was alleviated by zanubrutinib. The smart-seq analysis demonstrated that treatment with BTK inhibitor instigated microglial transcriptome changes including downregulation of chemokine-related genes and genes involved in the top 5 biological processes related to cell adhesion and migration, which are likely responsible for the reduced crosstalk of microglia and astrocytes. Conclusions: Our results show that BTK activity is enhanced both in B cells and microglia and BTK inhibition contributes to the amelioration of NMOSD pathology. These data collectively reveal the mechanism of action of BTK inhibition and corroborate BTK as a viable therapeutic target. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (BTK) plays a key role in the B-cell receptor (BCR) signaling pathway and confers anti-apoptotic and proliferative properties to malignant B-cells in chronic lymphocytic leukemia (CLL). Small molecule BTK inhibitors were designed to bind BTK's active site and block downstream signaling. These drugs have now been used in the treatment of thousands of patients with CLL, the most common form of leukemia in the western hemisphere. However, adverse effects of early generations of BTK inhibitors and resistance to treatment have led to the development of newer, more selective and non-covalent BTK inhibitors. As the use of these newer generation BTK inhibitors has increased, novel BTK resistance mutations have come to light. This review aims to discuss previously known and novel BTK mutations, their mechanisms of resistance, and their relationship with patient treatment. Also discussed here are future studies that are needed to investigate the underlying cause allowing these mutations to occur and how they incite resistance. New treatments on the horizon that attempt to maneuver around these resistance mutations can be met with new resistance mutations, creating an unmet need for patients with CLL. Novel therapies and combinations that address all forms of resistance are discussed. [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: Inhibition of Bruton's tyrosine kinase (BTK) is an emerging multiple sclerosis (MS) therapy. BTK inhibitors (BTKi) cross the blood-brain barrier and modulate B cells and microglia, major cellular players in active and chronic active lesions. Objective: To assess potential lesional and cellular targets of BTKi, we examined BTK expression in different type of MS white matter (WM) lesions, in unmanipulated CNS resident cells, and in a degenerative MS model associated with microglia activation in vivo. Methods: We examined BTK expression by next-generation RNA-sequencing in postmortem 25 control WM, 19 NAWM, 6 remyelinating, 18 active, 13 inactive and 17 chronic active lesions. Presence of B cells and microglia were examined by immunohistochemistry. CNS resident cells were isolated from the mouse brain by magnetic sorting. BTK expression was examined by quantitative PCR in isolated cells and dissected corpus callosum from mice treated with cuprizone (CPZ). Results: BTK expression was significantly increased in active and chronic active lesions with upregulated complement receptors and Fcg receptors. Active lesions contained high number of perivascular B cells, microglia, and macrophages. Chronic active lesions were characterized by microglia/macrophages in the rim. Microglia expressed BTK at high level (120-fold) in contrast to other CNS cell types (2-4-fold). BTK expression was increasing during CPZ treatment reaching significance after stopping CPZ. Conclusion: Considering BTK expression in MS lesions and resident cells, BTKi may exert effect on B cells, microglia/macrophages in active lesions, and limit microglia activation in chronic active lesions, where tissue damage propagates. [ABSTRACT FROM AUTHOR]

Background: Bruton's tyrosine kinase (BTK) is a cytoplasmic protein involved in the B cell development. X-linked agammaglobulinemia (XLA) is caused by mutation in the BTK gene, which results in very low or absent B cells. Affected males have markedly reduced immunoglobulin levels, which render them susceptible to recurrent and severe bacterial infections. Methods: Patients suspected with Xlinked agammaglobulinemia were enrolled during the period of 2010-2018. Clinical summary, and immunological profiles of these patients were recorded. Peripheral blood samples were collected for monocyte BTK protein expression detection and BTK genetic analysis. The medical records between January 2020 and June 2023 were reviewed to investigate COVID-19 in XLA. Results: Twenty-two patients (from 16 unrelated families) were molecularly diagnosed as XLA. Genetic testing revealed fifteen distinct mutations, including four splicing mutations, four missense mutations, three nonsense mutations, three short deletions, and one large indel mutation. These mutations scattered throughout the BTK gene and mostly affected the kinase domain. All mutations including five novel mutations were predicted to be pathogenic or deleterious by in silico prediction tools. Genetic testing confirmed that eleven mothers and seven sisters were carriers for the disease, while three mutations were de novo. Flow cytometric analysis showed that thirteen patients had minimal BTK expression (0-15%) while eight patients had reduced BTK expression (16-64%). One patient was not tested for monocyte BTK expression due to insufficient sample. Pneumonia (n=13) was the most common manifestation, while Pseudomonas aeruginosa was the most frequently isolated pathogen from the patients (n=4). Mild or asymptomatic COVID-19 was reported in four patients. Conclusion: This report provides the first overview of demographic, clinical, immunological and genetic data of XLA in Malaysia. The combination of flow cytometric assessment and BTK genetic analysis provides a definitive diagnosis for XLA patients, especially with atypical clinical presentation. In addition, it may also allow carrier detection and assist in genetic counselling and prenatal diagnosis. [ABSTRACT FROM AUTHOR]

Background: Evobrutinib is an oral, central nervous system (CNS)-penetrant and highly selective covalent Bruton's tyrosine kinase inhibitor under clinical development for patients with relapsing multiple sclerosis (RMS). Objective: To investigate the effect of evobrutinib on immune responses in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinated patients with RMS from a Phase II trial (NCT02975349). Methods: A post hoc analysis of patients with RMS who received evobrutinib 75 mg twice daily and SARS-CoV-2 vaccines during the open-label extension (n = 45) was conducted. Immunoglobulin (Ig)G anti-S1/S2-specific SARS-CoV-2 antibodies were measured using an indirect chemiluminescence immunoassay. Results: In the vaccinated subgroup, mean/minimum evobrutinib exposure pre-vaccination was 105.2/88.7 weeks. In total, 43 of 45 patients developed/increased S1/S2 IgG antibody levels post-vaccination; one patient's antibody response remained negative post-vaccination and the other had antibody levels above the upper limit of detection, both pre- and post-vaccination. Most patients (n = 36/45), regardless of pre-vaccination serostatus, had a 10–100-fold increase of antibody levels pre- to post-vaccination. Antibody levels post-booster were higher versus post-vaccination. Conclusion: These results suggest evobrutinib, an investigational drug with therapeutic potential for patients with RMS, acts as an immunomodulator, that is, it inhibits aberrant immune cell responses in patients with RMS, while responsiveness to foreign de novo and recall antigens is maintained. [ABSTRACT FROM AUTHOR]

Bruton's tyrosine kinase (BTK) inhibitors represent a class of drugs that have demonstrated their efficacy and safety in patients with chronic lymphocytic leukemia and non-Hodgkin's lymphomas who were considered refractory to any previously used type of therapy. BTK plays a key role in all stages of B lymphocyte development, but in recent years, there have been data indicating that BTK is also involved in the activation of myeloid cells.The aim of this study is to analyze and systematize all published materials on the immunomodulatory effects of BTK inhibitors (ibrutinib, acalabrutinib, etc.).A systematic review of the scientific literature was performed using a step-by-step search process in electronic databases (PubMed, Web of Science, ScienceDirect, and Scopus). The following keywords were used in the database search: “CLL”, “BTK”, “ibrutinib”, “COVID-19”, “allergy”, “inflammation.” The search for studies was conducted from the time of the first BTK inhibitor drug (ibrutinib) appearance in 2009 until December 2022.The results of the study on the influence of BTK inhibitors on the functional state of B and T lymphocytes, neutrophils, and monocytes/macrophages are presented. The immunomodulatory effects of ibrutinib on adaptive and innate immune system cells, including CD4+ and CD8+T lymphocytes and NK cells, are described. Since BTK inhibitors alter the functional activity of phagocytic cells and the ratio of T cell populations, there is a suggestion about the possibility of using these drugs for the treatment of other nosological forms, not only B cell malignancies, which is currently being studied in clinical trials. Data on the use of BTK inhibitors to combat hyperacute inflammation and to suppress allergic reactions, including anaphylaxis, are summarized. In addition, the expediency of short-term use of BTK inhibitors to reduce the risk of side effects during oral immunotherapy and for desensitization to drugs is discussed.The presented data indicate that BTK inhibitors are promising drugs with immunomodulatory effects. However, BTK inhibitors need to increase selectivity to reduce off-target effects on other kinases.

Immune thrombocytopenic purpura (ITP) is an acquired antibody or cell-mediated platelet damage or decreased platelet production. Steroids, IV immunoglobulins (IVIG), and Rho-anti-D antibodies are the commonly used initial treatments for ITP. However, many ITP patients either do not respond or do not maintain a response to initial therapy. Splenectomy, rituximab, and thrombomimetics are the commonly used second-line treatment. More treatment options include tyrosine kinases inhibitors (TKI), including spleen tyrosine kinase (Syk) and Bruton’s tyrosine kinase (BTK) inhibitors. This review aims to assess the safety and efficacy of TKIs. Methods: Literature was searched on PubMed, Embase, WOS, and clinicaltrials.gov using keywords, “tyrosine kinase” and “idiopathic thrombocytopenic purpura”. PRISMA guidelines were followed. Results: In total, 4 clinical trials were included with 255 adult patients with relapsed/refractory ITP. In all, 101 (39.6%) patients were treated with fostamatinib, 60 (23%) patients with rilzabrutinib, and 34 (13%) with HMPL-523. Patients treated with fostamatinib achieved a stable response (SR) and overall response (OR) in 18/101 (17.8%) and 43/101 (42.5%) of the patients, respectively, while SR and OR were achieved in 1/49 (2%) and 7/49 (14%) of the patients, respectively, in the placebo group. Patients treated with HMPL-523 (300 mg dose expansion) achieved an SR and OR in 5/20 (25%) and 11/20 (55%) of the patients, respectively, while SR and OR were achieved in 1/11 (9%) of the patients treated with the placebo. Patients treated with rilzabrutinib achieved an SR in 17/60 (28%) patients. Dizziness (1%), hypertension (2%), diarrhea (1%), and neutropenia (1%) were serious adverse events in fostamatinib patients. Rilzabrutinib or HMPL-523 patients did not require a dose reduction due to drug-related adverse effects. Conclusions: Rilzabrutinib, fostamatinib, and HMPL-523 were safe and effective in the treatment of relapsed/refractory ITP.

X-linked agammaglobulinemia (XLA) is a rare hereditary primary immunodeficiency disorder caused by mutation in the Bruton's tyrosine kinase (BTK) gene located in the Xq22 region of the X chromosome. It is characterized by absolute or marked deficiency of matured B-cells in circulation as well as decreased in all immunoglobulin (Ig) classes. We have reported one case who is a 48-month-old boy and suffering from recurrent pneumonia, skin abscess, otitis media, and swelling of the left knee joint. His serum Ig levels showed an IgM level of

Abstract 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.

(1) Background: Heart failure (HF) is the final stage of multiple cardiac diseases, which have now become a severe public health problem worldwide. β-Adrenergic receptor (β-AR) overactivation is a major pathological factor associated with multiple cardiac diseases and mediates cardiac fibrosis and inflammation. Previous research has demonstrated that Bruton's tyrosine kinase (BTK) mediated cardiac fibrosis by TGF-β related signal pathways, indicating that BTK was a potential drug target for cardiac fibrosis. Zanubrutinib, a second-generation BTK inhibitor, has shown anti-fibrosis effects in previous research. However, it is unclear whether Zanubrutinib can alleviate cardiac fibrosis induced by β-AR overactivation; (2) Methods: In vivo: Male C57BL/6J mice were treated with or without the β-AR agonist isoproterenol (ISO) to establish a cardiac fibrosis animal model; (3) Results: In vivo: Results showed that the BTK inhibitor Zanubrutinib (ZB) had a great effect on cardiac fibrosis and inflammation induced by β-AR. In vitro: Results showed that ZB alleviated β-AR-induced cardiac fibroblast activation and macrophage pro-inflammatory cytokine production. Further mechanism studies demonstrated that ZB inhibited β-AR-induced cardiac fibrosis and inflammation by the BTK, STAT3, NF-κB, and PI3K/Akt signal pathways both in vivo and in vitro; (4) Conclusions: our research provides evidence that ZB ameliorates β-AR-induced cardiac fibrosis and inflammation. [ABSTRACT FROM AUTHOR]

1. Evobrutinib is a highly selective, covalent, central nervous system-penetrant Bruton's tyrosine kinase (BTK) inhibitor, currently in Phase III trials for the treatment of relapsing multiple sclerosis. One major circulating metabolite of evobrutinib has been previously identified as the racemic dihydrodiol M463-2 (MSC2430422) in a Phase I human mass balance study. 2. Phenotyping experiments were conducted to confirm the metabolic pathway of evobrutinib to M463-2. Ratio of the enantiomers was determined by enantioselective liquid chromatography with tandem mass spectrometry analysis of plasma samples from humans and preclinical species. Drugdrug interaction (DDI) characterisation, evaluation of pharmacological activity on BTK, and off-target screening experiments followed assessing safety of the metabolite. 3. The biotransformation of evobrutinib to M463-2 was determined to be a two-step process with a CYP-mediated oxidation acting to form an epoxide intermediate, which was further hydrolysed by soluble and mitochondrial epoxide hydrolase. Only the (S)-enantiomer was determined to be a major metabolite, the (R)-enantiomer was minor. In vitro studies demonstrated the (S)-enantiomer lacked clinically relevant pharmacological activity, off-target effects and DDIs. 4. The biotransformation of evobrutinib to its major metabolite has been elucidated, with the major (S)-enantiomer being shown to pose no on/off target or DDI risks. [ABSTRACT FROM AUTHOR]

Simple Summary: Non-covalent Bruton's tyrosine kinase inhibitors (ncBTKi) are being investigated for the treatment of B-cell malignancies, including chronic lymphocytic leukemia (CLL). These agents hold promise for the treatment of CLL, especially CLL requiring treatment after prior discontinuation of covalent Bruton's tyrosine kinase inhibitors such as ibrutinib, acalabrutinib and zanubrutinib for either intolerance or progression of disease. This review outlines current preclinical and clinical data for the use of ncBTKi in CLL. Recently reported data has shown durable responses for the ncBTKi pirtobrutinib in CLL patients previously treated with a covalent BTKi with a median PFS of 19.6 months. We also discuss recently discovered mechanisms of resistance to ncBTKis, including acquired mutations in the BTK protein not in the C481 position. In addition, we highlight ongoing clinical trials that are incorporating ncBTKis in CLL as monotherapy or in combination therapies with other agents. The results of these trials as well as ongoing research regarding mechanisms of resistance to ncBTKi and covalent Bruton's Tyrosine Kinase inhibitors will be important to determine where ncBTKi may fit into the treatment of CLL. Covalent Bruton's tyrosine kinase inhibitors (cBTKi) have led to a paradigm shift in the treatment of chronic lymphocytic leukemia (CLL). These targeted oral therapies are administered as standard treatments in both the front-line and relapsed and/or refractory settings. Given their administration as a continuous therapy with a "treat-to-progression" strategy, limitations of their use include discontinuation due to toxicity or from progression of the disease. Non-covalent Bruton's tyrosine kinase inhibitors (ncBTKi) distinguish themselves by binding reversibly to the BTK target, which may address the limitations of toxicity and acquired resistance seen with cBTKi. Several ncBTKis have been studied preclinically and in clinical trials, including pirtobrutinib and nemtabrutinib. Pirtobrutinib, which is now FDA approved for relapsed and/or refractory mantle cell lymphoma (MCL), has shown outstanding safety and preliminary efficacy in CLL in phase 1 and 2 clinical trials, with phase 3 trials underway. This agent may fill an unmet medical need for CLL patients requiring treatment after a cBTKi. Pirtobrutinib is particularly promising for the treatment of "double exposed" CLL, defined as CLL requiring treatment after both a cBTKi and venetoclax. Some patients have now developedacquired resistance to pirtobrutinib, and resistance mechanisms (including novel acquired mutations in BTK outside of the C481 position) have been recently described. Further study regarding the mechanisms of resistance to pirtobrutinib in patients without prior cBTKi exposure, as well as the potential for cross-resistance between cBTKi and ncBTKis, may be important to help inform where ncBTKis will ultimately fit in the treatment sequencing paradigm for CLL. An emerging clinical challenge is the treatment of CLL after ncBTKi discontinuation. Novel therapeutic strategies are being investigated to address the treatment of patients following disease progression on ncBTKis. Such strategies include novel agents (BTK degraders, bispecific antibody therapy, CAR T-cell therapy, PKC-beta inhibitors) as well as combination approaches incorporating a ncBTKi (e.g., pirtobrutinib and venetoclax) that may help overcome this acquired resistance. [ABSTRACT FROM AUTHOR]

X-linked agammaglobulinemia (XLA) is a rare hereditary primary immunodeficiency disorder caused by mutation in the Bruton's tyrosine kinase (BTK) gene located in the Xq22 region of the X chromosome. It is characterized by absolute or marked deficiency of matured B-cells in circulation as well as decreased in all immunoglobulin (Ig) classes. We have reported one case who is a 48-month-old boy and suffering from recurrent pneumonia, skin abscess, otitis media, and swelling of the left knee joint. His serum Ig levels showed an IgM level of <0.169 g/l, IgG 2.43 g/l, and IgA <0.256 g/l. Immunophenotyping of lymphocyte subsets showed an absence of B-cells. Intracellular BTK protein expression in monocytes by flow cytometry showed a markedly reduced mean fluorescence index which confirmed the diagnosis of XLA. Antibiotics with intravenous Ig therapy were started. [ABSTRACT FROM AUTHOR]

Abstract Vitreoretinal lymphoma (VRL) is strongly linked to central nervous system (CNS) progression with no standard treatment approaches. Commonly used strategies include repeated intraocular injections of low-dose methotrexate or local radiotherapy, with great inconvenience, long-term side effects, and high risk of CNS relapse. In this study, we evaluated the efficacy and safety of bruton’s tyrosine kinase inhibitors (BTKi) in the treatment of VRL. This prospective single-center study enrolled patients with relapsed or newly diagnosed VRL between October 2020 and April 2022. Patients received BTKi monotherapy until disease progression or unacceptable toxicity. The primary endpoint was the disease control (DC) rate after one month of treatment; secondary endpoints include toxicity, overall survival (OS), and progression-free survival (PFS). Ten consecutive patients with VRL were enrolled into this study. After 1-month treatment, 9 patients (90%) achieved a DC, with 7 patients (70%) achieving a complete response (CR). With a median follow-up of 8.3 (2.5–21.4) months, 4 patients were confirmed to have disease progression, with a PFS of 1.2, 7.5, 9.1, and 11.6 months, respectively. The remaining 6 patients have durable control of disease and were still on treatment at time of the analysis. BTKi were well-tolerated and no patients discontinued the drug because of adverse events. In conclusion, targeting BTK in VRL is viable, and our findings could pave the way for a paradigm change in VRL therapy choices. Further large-scale studies, however, are required to give stronger evidence about the efficacy and safety.

Bruton's tyrosine kinase (Btk) and spleen tyrosine kinase (Syk) are major signaling proteins in human platelets that are implicated in atherothrombosis and thrombo-inflammation, but the mechanisms controlling their activities are not well understood. Previously, we showed that Syk becomes phosphorylated at S297 in glycoprotein VI (GPVI)-stimulated human platelets, which limits Syk activation. Here, we tested the hypothesis that protein kinases C (PKC) and A (PKA) and protein phosphatase 2A (PP2A) jointly regulate GPVI-induced Btk activation in platelets. The GPVI agonist convulxin caused rapid, transient Btk phosphorylation at S180 (pS180↑), Y223 and Y551, while direct PKC activation strongly increased Btk pS180 and pY551. This increase in Btk pY551 was also Src family kinase (SFK)-dependent, but surprisingly Syk-independent, pointing to an alternative mechanism of Btk phosphorylation and activation. PKC inhibition abolished convulxin-stimulated Btk pS180 and Syk pS297, but markedly increased the tyrosine phosphorylation of Syk, Btk and effector phospholipase Cγ2 (PLCγ2). PKA activation increased convulxin-induced Btk activation at Y551 but strongly suppressed Btk pS180 and Syk pS297. PP2A inhibition by okadaic acid only increased Syk pS297. Both platelet aggregation and PLCγ2 phosphorylation with convulxin stimulation were Btk-dependent, as shown by the selective Btk inhibitor acalabrutinib. Together, these results revealed in GPVI-stimulated platelets a transient Syk, Btk and PLCγ2 phosphorylation at multiple sites, which are differentially regulated by PKC, PKA or PP2A. Our work thereby demonstrated the GPVI–Syk–Btk signalosome as a tightly controlled protein kinase network, in agreement with its role in atherothrombosis. [ABSTRACT FROM AUTHOR]

Context: Squamous cell carcinoma (SCC) is the second most common type of skin cancer caused by malignant keratinocytes. Multiple studies have shown that protein mutations have a significant impact on the development and progression of cancer, including SCC. We attempted to decode the effect of single amino acid mutations in the Bruton's tyrosine kinase (BTK) protein in this study. Molecular dynamic (MD) simulations were performed on selected deleterious mutations of the BTK protein, revealing that the variants adversely affect the protein, indicating that they may contribute to the prognosis of SCC by making the protein unstable. Then, we investigated the interaction between the protein and its mutants with ibrutinib, a drug designed to treat SCC. Even though the mutations have deleterious effects on protein structure, they bind to ibrutinib similarly to their wild type counterpart. This study demonstrates that the effect of detected missense mutations is unfavorable and can result in function loss, which is severe for SCC, but that ibrutinib-based therapy can still be effective on them, and the mutations can be used as biomarkers for Ibrutinib-based treatment. Methods: Seven different computational techniques were used to compute the effect of SAVs in accordance with the experimental requirements of this study. To understand the differences in protein and mutant dynamics, MD simulation and trajectory analysis, including RMSD, RMSF, PCA, and contact analysis, were performed. The free binding energy and its decomposition for each protein-drug complex were determined using docking, MM-GBSA, MM-PBSA, and interaction analysis (wild and mutants). [ABSTRACT FROM AUTHOR]

Ibrutinib is a first-generation inhibitor of Bruton tyrosine kinase (BTK) that is currently approved to treat patients with B-cell malignancies, including Waldenström macroglobulinemia (WM), relapsed/refractory (R/R) mantle cell lymphoma (MCL), R/R marginal zone lymphoma (MZL), and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Off-target adverse effects, such as atrial fibrillation, hypertension, and bleeding, have been observed and may limit a patient's tolerance for treatment. Currently, there is no well-established treatment regimen for patients who cannot tolerate ibrutinib. Approaches to address such patients include managing ibrutinib side effects with supportive care or dose reductions, switching to an alternative covalent BTK inhibitor, or abandoning covalent BTK inhibitors for alternative forms of treatment. Here we review the literature and provide guidance on treating ibrutinib-intolerant patients with B-cell malignancies. [ABSTRACT FROM AUTHOR]

Humans with dysfunctional Bruton’s tyrosine kinase (Btk) are highly susceptible to bacterial infections. Compelling evidence indicates that Btk is essential for B cell-mediated immunity, whereas its role in myeloid cell-mediated immunity against infections is controversial. In this study, we determined the contribution of Btk in B cells and neutrophils to host defense against the extracellular bacterial pathogen Klebsiella pneumoniae, a common cause of pulmonary infections and sepsis. Btk−/− mice were highly susceptible to Klebsiella infection, which was not reversed by Btk re-expression in B cells and restoration of natural antibody levels. Neutrophil-specific Btk deficiency impaired host defense against Klebsiella to a similar extent as complete Btk deficiency. Neutrophil-specific Btk deficiency abolished extracellular reactive oxygen species production in response to Klebsiella. These data indicate that expression of Btk in neutrophils is crucial, while in B cells, it is dispensable for in vivo host defense against K. pneumoniae.

In the last few decades, there has been a growing interest in Bruton's tyrosine kinase (BTK) and the compounds that target it. BTK is a downstream mediator of the B-cell receptor (BCR) signaling pathway and affects B-cell proliferation and differentiation. Evidence demonstrating the expression of BTK on the majority of hematological cells has led to the hypothesis that BTK inhibitors (BTKIs) such as ibrutinib can be an effective treatment for leukemias and lymphomas. However, a growing body of experimental and clinical data has demonstrated the significance of BTK, not just in B-cell malignancies, but also in solid tumors, such as breast, ovarian, colorectal, and prostate cancers. In addition, enhanced BTK activity is correlated with autoimmune disease. This gave rise to the hypothesis that BTK inhibitors can be beneficial in the therapy of rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), Sjögren's syndrome (SS), allergies, and asthma. In this review article, we summarize the most recent findings regarding this kinase as well as the most advanced BTK inhibitors that have been developed to date and their clinical applications mainly in cancer and chronic inflammatory disease patients. [ABSTRACT FROM AUTHOR]