Bruton's Tyrosine Kinase (BTK) Inhibitors and Autoimmune Diseases: Making Sense of BTK Inhibitor Specificity Profiles and Recent Clinical Trial Successes and Failures

Targeting autoimmune mechanisms by precision medicine in Myasthenia Gravis

Myasthenia Gravis (MG) is a chronic disabling autoimmune disease caused by autoantibodies to the neuromuscular junction (NMJ), characterized clinically by fluctuating weakness and early fatigability of ocular, skeletal and bulbar muscles. Despite being commonly considered a prototypic autoimmune disorder, MG is a complex and heterogeneous condition, presenting with variable clinical phenotypes, likely due to distinct pathophysiological settings related with different immunoreactivities, symptoms' distribution, disease severity, age at onset, thymic histopathology and response to therapies. Current treatment of MG based on international consensus guidelines allows to effectively control symptoms, but most patients do not reach complete stable remission and require life-long immunosuppressive (IS) therapies. Moreover, a proportion of them is refractory to conventional IS treatment, highlighting the need for more specific and tailored strategies. Precision medicine is a new frontier of medicine that promises to greatly increase therapeutic success in several diseases, including autoimmune conditions. In MG, B cell activation, antibody recycling and NMJ damage by the complement system are crucial mechanisms, and their targeting by innovative biological drugs has been proven to be effective and safe in clinical trials. The switch from conventional IS to novel precision medicine approaches based on these drugs could prospectively and significantly improve MG care. In this review, we provide an overview of key immunopathogenetic processes underlying MG, and discuss on emerging biological drugs targeting them. We also discuss on future direction of research to address the need for patients' stratification in endotypes according with genetic and molecular biomarkers for successful clinical decision making within precision medicine workflow.

Sequential immunotherapy: towards cures for autoimmunity

Despite major progress in the treatment of autoimmune diseases in the past two decades, most therapies do not cure disease and can be associated with increased risk of infection through broad suppression of the immune system. However, advances in understanding the causes of autoimmune disease and clinical data from novel therapeutic modalities such as chimeric antigen receptor T cell therapies provide evidence that it may be possible to re-establish immune homeostasis and, potentially, prolong remission or even cure autoimmune diseases. Here, we propose a 'sequential immunotherapy' framework for immune system modulation to help achieve this ambitious goal. This framework encompasses three steps: controlling inflammation; resetting the immune system through elimination of pathogenic immune memory cells; and promoting and maintaining immune homeostasis via immune regulatory agents and tissue repair. We discuss existing drugs and those in development for each of the three steps. We also highlight the importance of causal human biology in identifying and prioritizing novel immunotherapeutic strategies as well as informing their application in specific patient subsets, enabling precision medicine approaches that have the potential to transform clinical care.

Bruton tyrosine kinase inhibitors in multiple sclerosis: evidence and expectations

PURPOSE OF REVIEW

Despite availability of high-efficacy therapies for multiple sclerosis (MS), many patients experience significant disability worsening due to limited effects of currently available drugs on central nervous system (CNS)-compartmentalized inflammation. Bruton tyrosine kinase (BTK) is an intracellular signaling molecule involved in regulation of maturation, survival, migration, and activation of B cells and microglia, which are central players in the immunopathogenesis of progressive MS. Therefore, CNS-penetrant BTK inhibitors may better prevent disease progression by targeting immune cells on both sides of the blood-brain barrier. This review gives an overview on the preliminary results of clinical trials.

RECENT FINDINGS

Currently, the efficacy and safety of six BTK inhibitors are being evaluated in clinical trials in patients with relapsing and progressive MS. Evobrutinib, tolebrutinib and fenebrutinib have shown efficacy and safety in relapsing MS in phase 2 studies, and evobrutinib and tolebrutinib in their extension studies up to 3-5 years. However, evobrutinib failed to distinguish itself from the comparator drug teriflunomide in reduction of relapse rate (primary end point) in two phase 3 studies in relapsing MS.

SUMMARY

Inhibition of BTK has emerged as a promising therapeutic approach to target the CNS-compartmentalized inflammation. Results from phase 3 clinical trials will shed light on differences in efficacy and safety of BTK inhibitors and its potential role in the future MS landscape.

Interferon and B-cell Signatures Inform Precision Medicine in Lupus Nephritis

Introduction

Current therapeutic management of lupus nephritis (LN) fails to induce long-term remission in over 50% of patients, highlighting the urgent need for additional options.

Methods

We analyzed differentially expressed genes (DEGs) in peripheral blood from patients with active LN (n = 41) and active nonrenal lupus (n = 62) versus healthy controls (HCs) (n = 497) from the European PRECISESADS project (NTC02890121), and dysregulated gene modules in a discovery (n = 26) and a replication (n = 15) set of active LN cases.

Results

Replicated gene modules qualified for correlation analyses with serologic markers, and regulatory network and druggability analysis. Unsupervised coexpression network analysis revealed 20 dysregulated gene modules and stratified the active LN population into 3 distinct subgroups. These subgroups were characterized by low, intermediate, and high interferon (IFN) signatures, with differential dysregulation of the "B cell" and "plasma cells/Ig" modules. Drugs annotated to the IFN network included CC-motif chemokine receptor 1 (CCR1) inhibitors, programmed death-ligand 1 (PD-L1) inhibitors, and irinotecan; whereas the anti-CD38 daratumumab and proteasome inhibitor bortezomib showed potential for counteracting the "plasma cells/Ig" signature. In silico analysis demonstrated the low-IFN subgroup to benefit from calcineurin inhibition and the intermediate-IFN subgroup from B-cell targeted therapies. High-IFN patients exhibited greater anticipated response to anifrolumab whereas daratumumab appeared beneficial to the intermediate-IFN and high-IFN subgroups.

Conclusion

IFN upregulation and B and plasma cell gene dysregulation patterns revealed 3 subgroups of LN, which may not necessarily represent distinct disease phenotypes but rather phases of the inflammatory processes during a renal flare, providing a conceptual framework for precision medicine in LN.

Discovery and Preclinical Characterization of BIIB129, a Covalent, Selective, and Brain-Penetrant BTK Inhibitor for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic disease with an underlying pathology characterized by inflammation-driven neuronal loss, axonal injury, and demyelination. Bruton's tyrosine kinase (BTK), a nonreceptor tyrosine kinase and member of the TEC family of kinases, is involved in the regulation, migration, and functional activation of B cells and myeloid cells in the periphery and the central nervous system (CNS), cell types which are deemed central to the pathology contributing to disease progression in MS patients. Herein, we describe the discovery of BIIB129 (25), a structurally distinct and brain-penetrant targeted covalent inhibitor (TCI) of BTK with an unprecedented binding mode responsible for its high kinome selectivity. BIIB129 (25) demonstrated efficacy in disease-relevant preclinical in vivo models of B cell proliferation in the CNS, exhibits a favorable safety profile suitable for clinical development as an immunomodulating therapy for MS, and has a low projected total human daily dose.

Iguratimod suppresses plasma cell differentiation and ameliorates experimental Sjögren's syndrome in mice by promoting TEC kinase degradation

Primary Sjögren's syndrome (pSS) is a chronic inflammatory autoimmune disease with an unclear pathogenesis, and there is currently no approved drug for the treatment of this disease. Iguratimod, as a novel clinical anti-rheumatic drug in China and Japan, has shown remarkable efficacy in improving the symptoms of patients with pSS in clinical studies. In this study we investigated the mechanisms underlying the therapeutic effect of iguratimod in the treatment of pSS. Experimental Sjögren's syndrome (ESS) model was established in female mice by immunizing with salivary gland protein. After immunization, ESS mice were orally treated with iguratimod (10, 30, 100 mg·kg-1·d-1) or hydroxychloroquine (50 mg·kg-1·d-1) for 70 days. We showed that iguratimod administration dose-dependently increased saliva secretion, and ameliorated ESS development by predominantly inhibiting B cells activation and plasma cell differentiation. Iguratimod (30 and 100 mg·kg-1·d-1) was more effective than hydroxychloroquine (50 mg·kg-1·d-1). When the potential target of iguratimod was searched, we found that iguratimod bound to TEC kinase and promoted its degradation through the autophagy-lysosome pathway in BAFF-activated B cells, thereby directly inhibiting TEC-regulated B cells function, suggesting that the action mode of iguratimod on TEC was different from that of conventional kinase inhibitors. In addition, we found a crucial role of TEC overexpression in plasma cells of patients with pSS. Together, we demonstrate that iguratimod effectively ameliorates ESS via its unique suppression of TEC function, which will be helpful for its clinical application. Targeting TEC kinase, a new regulatory factor for B cells, may be a promising therapeutic option.

BTK signaling-a crucial link in the pathophysiology of chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is an inflammatory skin disorder that manifests with itchy wheals, angioedema, or both for more than 6 weeks. Mast cells and basophils are the key pathogenic drivers of CSU; their activation results in histamine and cytokine release with subsequent dermal inflammation. Two overlapping mechanisms of mast cell and basophil activation have been proposed in CSU: type I autoimmunity, also called autoallergy, which is mediated via IgE against various autoallergens, and type IIb autoimmunity, which is mediated predominantly via IgG directed against the IgE receptor FcεRI or FcεRI-bound IgE. Both mechanisms involve cross-linking of FcεRI and activation of downstream signaling pathways, and they may co-occur in the same patient. In addition, B-cell receptor signaling has been postulated to play a key role in CSU by generating autoreactive B cells and autoantibody production. A cornerstone of FcεRI and B-cell receptor signaling is Bruton tyrosine kinase (BTK), making BTK inhibition a clear therapeutic target in CSU. The potential application of early-generation BTK inhibitors, including ibrutinib, in allergic and autoimmune diseases is limited owing to their unfavorable benefit-risk profile. However, novel BTK inhibitors with improved selectivity and safety profiles have been developed and are under clinical investigation in autoimmune diseases, including CSU. In phase 2 trials, the BTK inhibitors remibrutinib and fenebrutinib have demonstrated rapid and sustained improvements in CSU disease activity. With phase 3 studies of remibrutinib ongoing, it is hoped that BTK inhibitors will present an effective, well-tolerated option for patients with antihistamine-refractory CSU, a phenotype that presents a considerable clinical challenge.

A review of Bruton's tyrosine kinase inhibitors in multiple sclerosis

Bruton's tyrosine kinase (BTK) inhibitors are an emerging class of therapeutics in multiple sclerosis (MS). BTK is expressed in B-cells and myeloid cells, key progenitors of which include dendritic cells, microglia and macrophages, integral effectors of MS pathogenesis, along with mast cells, establishing the relevance of BTK inhibitors to diverse autoimmune conditions. First-generation BTK inhibitors are currently utilized in the treatment of B-cell malignancies and show efficacy in B-cell modulation. B-cell depleting therapies have shown success as disease-modifying treatments (DMTs) in MS, highlighting the potential of BTK inhibitors for this indication; however, first-generation BTK inhibitors exhibit a challenging safety profile that is unsuitable for chronic use, as required for MS DMTs. A second generation of highly selective BTK inhibitors has shown efficacy in modulating MS-relevant mechanisms of pathogenesis in preclinical as well as clinical studies. Six of these BTK inhibitors are undergoing clinical development for MS, three of which are also under investigation for chronic spontaneous urticaria (CSU), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Phase II trials of selected BTK inhibitors for MS showed reductions in new gadolinium-enhancing lesions on magnetic resonance imaging scans; however, the safety profile is yet to be ascertained in chronic use. Understanding of the safety profile is developing by combining safety insights from the ongoing phase II and III trials of second-generation BTK inhibitors for MS, CSU, RA and SLE. This narrative review investigates the potential of BTK inhibitors as an MS DMT, the improved selectivity of second-generation inhibitors, comparative safety insights established thus far through clinical development programmes and proposed implications in female reproductive health and in long-term administration.

Managing multiple sclerosis in individuals aged 55 and above: a comprehensive review

Multiple Sclerosis (MS) management in individuals aged 55 and above presents unique challenges due to the complex interaction between aging, comorbidities, immunosenescence, and MS pathophysiology. This comprehensive review explores the evolving landscape of MS in older adults, including the increased incidence and prevalence of MS in this age group, the shift in disease phenotypes from relapsing-remitting to progressive forms, and the presence of multimorbidity and polypharmacy. We aim to provide an updated review of the available evidence of disease-modifying treatments (DMTs) in older patients, including the efficacy and safety of existing therapies, emerging treatments such as Bruton tyrosine kinase (BTKs) inhibitors and those targeting remyelination and neuroprotection, and the critical decisions surrounding the initiation, de-escalation, and discontinuation of DMTs. Non-pharmacologic approaches, including physical therapy, neuromodulation therapies, cognitive rehabilitation, and psychotherapy, are also examined for their role in holistic care. The importance of MS Care Units and advance care planning are explored as a cornerstone in providing patient-centric care, ensuring alignment with patient preferences in the disease trajectory. Finally, the review emphasizes the need for personalized management and continuous monitoring of MS patients, alongside advocating for inclusive study designs in clinical research to improve the management of this growing patient demographic.

Bruton's tyrosine kinase ablation inhibits B cell responses and antibody production for the prevention of chronic rejection in cardiac transplantation

Chronic rejection is the primary cause of late allograft failure, however, the current treatments for chronic rejection have not yielded desirable therapeutic effects. B cell activation and donor-specific antibody (DSA) production are the primary factors leading to chronic rejection. Bruton's tyrosine kinase (BTK) plays a key role in the activation and differentiation of B cells and in antibody production. This study investigated the efficacy of blocking BTK signalling in the prevention of chronic rejection. BTK signalling was blocked using the BTK inhibitor ibrutinib and gene knockout. In vitro assays were conducted to examine the consequences and underlying mechanisms of BTK blockade in regards to B cell activation, differentiation, and antibody secretion. Additionally, we established a cardiac transplantation mouse model of chronic rejection to explore the preventive effects and mechanisms of BTK ablation on chronic rejection. Ablating BTK signalling in vitro resulted in the inhibition of B cell activation, differentiation, and antibody production. In vivo experiments provided evidence that ablating BTK signalling alleviated chronic rejection, leading to reduced damage in myocardial tissue, neointimal hyperplasia, interstitial fibrosis, inflammatory cell infiltration, and C4d deposition. Allograft survival was prolonged, and B cell responses and DSA production were inhibited as a result. We confirmed that ablation of BTK signalling inhibited B cell response by blocking downstream PLCγ2 phosphorylation and inhibiting the NF-κB, NFAT, and ERK pathways. Our findings demonstrated that ablation of BTK signalling inhibited B cell activation and differentiation, reduced DSA production, and effectively prevented chronic rejection.

Bruton's tyrosine kinase inhibition for the treatment of allergic disorders

IgE signaling through its high-affinity receptor FcεRI is central to the pathogenesis of numerous allergic disorders. Oral inhibitors of Bruton's tyrosine kinase (BTKis), which are currently Food and Drug Administration-approved for treating B cell malignancies, broadly inhibit the FcεRI pathway in human mast cells and basophils, and therefore may be effective allergen-independent therapies for a variety of allergic diseases. The application of these drugs to the allergy space was previously limited by the low kinase selectivity and subsequent toxicities of early-generation compounds. Fortunately, next-generation, highly selective BTKis in clinical development appear to have more favorable risk-benefit profiles, and their likelihood of being Food and Drug Administration-approved for an allergy indication is increasing. Recent clinical trials have indicated the remarkable and rapid efficacy of the second-generation BTKi acalabrutinib in preventing clinical reactivity to peanut ingestion in adults with peanut allergy. In addition, next-generation BTKis including remibrutinib effectively reduce disease activity in patients with antihistamine-refractory chronic spontaneous urticaria. Finally, several BTKis are currently under investigation in early clinical trials for atopic dermatitis and asthma. In this review, we summarize recent data supporting the use of these drugs as novel therapies in food allergy, anaphylaxis, urticaria, and other allergic disorders. We also discuss safety data derived from trials using both short-term and chronic dosing of BTKis.

Chronic Inflammatory Demyelinating Polyradiculoneuropathy: Current Therapeutic Approaches and Future Outlooks

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a treatable autoimmune disorder, for which different treatment options are available. Current first-line evidence-based therapies for CIDP include intravenous and subcutaneous immunoglobulins, corticosteroids and plasma exchanges. Despite lack of evidence, cyclophosphamide, rituximab and mycophenolate mofetil are commonly used in circumstances of refractoriness and, more debatably, of perceived overdependence on first-line therapies. Rituximab is currently the object of a randomized controlled trial for CIDP. Based on case series, and although rarely considered, haematopoietic autologous stem cell transplants may be effective in refractory disease, with low mortality and high remission rates. A new therapeutic option has appeared with efgartigimod, a neonatal Fc receptor blocker, recently shown to significantly lower relapse rate versus placebo, after withdrawal from previous immunotherapy. Other neonatal Fc receptor blockers, nipocalimab and batoclimab, are under study. The C1 complement-inhibitor SAR445088, acting in the proximal portion of the classical complement system, is currently the subject of a new study in treatment-responsive, refractory and treatment-naïve subjects. Finally, Bruton Tyrosine Kinase inhibitors, which exert anti-B cell effects, may represent another future research avenue. The widening of the therapeutic armamentarium enhances the need for improved evaluation of treatment effects and reliable biomarkers in CIDP.

Efficacy and safety of remibrutinib, a selective potent oral BTK inhibitor, in Sjögren's syndrome: results from a randomised, double-blind, placebo-controlled phase 2 trial

OBJECTIVES

To evaluate the safety and efficacy of remibrutinib in patients with moderate-to-severe Sjögren's syndrome (SjS) in a phase 2 randomised, double-blind trial (NCT04035668; LOUiSSE (LOU064 in Sjögren's Syndrome) study).

METHODS

Eligible patients fulfilling 2016 American College of Rheumatology/European League Against Rheumatism (EULAR) criteria for SjS, positive for anti-Ro/Sjögren's syndrome-related antigen A antibodies, with moderate-to-severe disease activity (EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) (based on weighted score) ≥ 5, EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI) ≥ 5) received remibrutinib (100 mg) either one or two times a day, or placebo for the 24-week study treatment period. The primary endpoint was change from baseline in ESSDAI at week 24. Key secondary endpoints included change from baseline in ESSDAI over time, change from baseline in ESSPRI over time and safety of remibrutinib in SjS. Key exploratory endpoints included changes to the salivary flow rate, soluble biomarkers, blood transcriptomic and serum proteomic profiles.

RESULTS

Remibrutinib significantly improved ESSDAI score in patients with SjS over 24 weeks compared with placebo (ΔESSDAI -2.86, p=0.003). No treatment effect was observed in ESSPRI score (ΔESSPRI 0.17, p=0.663). There was a trend towards improvement of unstimulated salivary flow with remibrutinib compared with placebo over 24 weeks. Remibrutinib had a favourable safety profile in patients with SjS over 24 weeks. Remibrutinib induced significant changes in gene expression in blood, and serum protein abundance compared with placebo.

CONCLUSIONS

These data show preliminary efficacy and favourable safety of remibrutinib in a phase 2 trial for SjS.

Registered trials on novel therapies for myasthenia gravis: a cross-sectional study on ClinicalTrials.gov

Novel biologics in MG therapy research is on the rise. This research aimed to investigate the characteristics of registered trials on novel therapies for myasthenia gravis on ClinicalTrials.gov. This cross-sectional study used a descriptive approach to assess the features of the included trials on ClinicalTrials.gov. We found 62 registered trials from 2007 to 2023 on ClinicalTrials.gov. The results showed a yearly rise in the number of registered trials (r = 0.76, p < 0.001). Following 2017, more industry-sponsored trials were conducted (91.5% [43] vs. 60% [9], p = 0.009), fewer results were released (10.6% [5] vs. 60% [9], p = 0.001), and more trials entered phase 3 (67.4% [31] vs. 20% [2], p = 0.001). The most researched novel medications were neonatal Fc receptor inhibitors (51.2% [21]), complement inhibitors (39.0% [16]), and B cell depletors (14.6% [6]). According to the website's data, the neonatal Fc receptor inhibitors and complement inhibitors were effective in treating myasthenia gravis patients in three trials (NCT03315130, NCT03669588, and NCT00727194). This study provides valuable insights into the profile of registered trials on novel therapies for myasthenia gravis. More clinical studies are needed in the future to prove the value of its application.

Safety, pharmacokinetics and pharmacodynamics of HWH486 capsules in healthy adults: A randomized, double-blind, placebo-controlled, phase I dose-escalation study

OBJECTIVES

HWH486 inhibits Bruton's tyrosine kinase and therefore shows promise as a treatment against rheumatoid arthritis and chronic spontaneous urticaria. This phase I trial assessed tolerability, safety, pharmacokinetics and pharmacodynamics of a single oral dose of HWH486 capsules in healthy adults.

METHODS

A single-center, randomized, double-blind, placebo-controlled, dose-escalation study from 10 to 800 mg was conducted in 96 healthy Chinese adults, of whom 80 received HWH486 and 16 received placebo.

RESULTS

A total of 96 subjects were enrolled, and all completed the study. In the HWH486 group, mean Tmax ranged from 1.03 to 2.00 h, and mean T1/2 ranged from 0.85 to 8.67 h across the dose range from 10 to 800 mg. Mean Cmax increased linearly with dose, while mean AUC0-t increased non-linearly. Occupancy of Bruton's tyrosine kinase peaked within 0.50-4.00 h after administration across the dose groups, and the delay until peak occupancy decreased with increasing dose. Twenty-five subjects (31.25 %) in the HWH486 group experienced 35 treatment-emergent adverse events, while four subjects (25.00 %) in the placebo group experienced eight such events.

CONCLUSIONS

HWH486 is well tolerated and safe in healthy adults, in whom it can strongly bind Bruton's tyrosine kinase. These findings justify clinical studies of HWH486 efficacy against autoimmune diseases.

A Comprehensive Review of Small-Molecule Inhibitors Targeting Bruton Tyrosine Kinase: Synthetic Approaches and Clinical Applications

Bruton tyrosine kinase (BTK) is an essential enzyme in the signaling pathway of the B-cell receptor (BCR) and is vital for the growth and activation of B-cells. Dysfunction of BTK has been linked to different types of B-cell cancers, autoimmune conditions, and inflammatory ailments. Therefore, focusing on BTK has become a hopeful approach in the field of therapeutics. Small-molecule inhibitors of BTK have been developed to selectively inhibit its activity and disrupt B-cell signaling pathways. These inhibitors bind to the active site of BTK and prevent its phosphorylation, leading to the inhibition of downstream signaling cascades. Regulatory authorities have granted approval to treat B-cell malignancies, such as chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL), with multiple small-molecule BTK inhibitors. This review offers a comprehensive analysis of the synthesis and clinical application of conventional small-molecule BTK inhibitors at various clinical stages, as well as presents promising prospects for the advancement of new small-molecule BTK inhibitors.

Death by a thousand cuts through kinase inhibitor combinations that maximize selectivity and enable rational multitargeting

Kinase inhibitors are successful therapeutics in the treatment of cancers and autoimmune diseases and are useful tools in biomedical research. However, the high sequence and structural conservation of the catalytic kinase domain complicate the development of selective kinase inhibitors. Inhibition of off-target kinases makes it difficult to study the mechanism of inhibitors in biological systems. Current efforts focus on the development of inhibitors with improved selectivity. Here, we present an alternative solution to this problem by combining inhibitors with divergent off-target effects. We develop a multicompound-multitarget scoring (MMS) method that combines inhibitors to maximize target inhibition and to minimize off-target inhibition. Additionally, this framework enables optimization of inhibitor combinations for multiple on-targets. Using MMS with published kinase inhibitor datasets we determine potent inhibitor combinations for target kinases with better selectivity than the most selective single inhibitor and validate the predicted effect and selectivity of inhibitor combinations using in vitro and in cellulo techniques. MMS greatly enhances selectivity in rational multitargeting applications. The MMS framework is generalizable to other non-kinase biological targets where compound selectivity is a challenge and diverse compound libraries are available.

Efficacy and safety of Bruton's tyrosine kinase inhibitors in the treatment of pemphigus: A comprehensive literature review and future perspective

Bruton's tyrosine kinase (BTK) is a protein involved in B-cell-receptor signaling and B-cell proliferation. The pathophysiology of several autoimmune diseases, such as pemphigus disorder, relies on the BTK signaling pathway. Therefore, BTK inhibitors were found to be beneficial alternatives to conventional treatmentsThe current study aimed to assess the efficacy and safety of BTK inhibitors in treating pemphigus. A complete search was performed on databases including PubMed/MedLine, Scopus, Web of Science, as well as Google Scholar search engine for studies published by September 20th, 2023. The current review indicates that BTK inhibitors alone or in combination with conventional treatments are promising options in the management of pemphigus. The overall safety profile of BTK inhibitors has been acceptable, and the reported adverse reactions were not severe or life-threatening.

Protein kinases: drug targets for immunological disorders

Protein kinases play a major role in cellular activation processes, including signal transduction by diverse immunoreceptors. Given their roles in cell growth and death and in the production of inflammatory mediators, targeting kinases has proven to be an effective treatment strategy, initially as anticancer therapies, but shortly thereafter in immune-mediated diseases. Herein, we provide an overview of the status of small molecule inhibitors specifically generated to target protein kinases relevant to immune cell function, with an emphasis on those approved for the treatment of immune-mediated diseases. The development of inhibitors of Janus kinases that target cytokine receptor signalling has been a particularly active area, with Janus kinase inhibitors being approved for the treatment of multiple autoimmune and allergic diseases as well as COVID-19. In addition, TEC family kinase inhibitors (including Bruton's tyrosine kinase inhibitors) targeting antigen receptor signalling have been approved for haematological malignancies and graft versus host disease. This experience provides multiple important lessons regarding the importance (or not) of selectivity and the limits to which genetic information informs efficacy and safety. Many new agents are being generated, along with new approaches for targeting kinases.

Structural optimization of pyrrolopyrimidine BTK inhibitors based on molecular simulation

CONTEXT

BTK is a critical regulator involved in the proliferation, differentiation, and apoptosis of B cells. BTK inhibitors can effectively alleviate various diseases such as tumors, leukemia, and asthma. During this study, a range of novel BTK inhibitors were designed using 3D-QSAR, molecular docking, and molecular dynamics (MD) simulation.

METHODS

We selected 41 pyrrolopyrimidine derivatives as BTK inhibitors to structure a 3D-QSAR model. Comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) were adopted to research the connection between the pharmacological activities and chemical structures of the compounds. The CoMFA model (q2 = 0.519, R2 = 0.971), CoMSIA model (q2 = 0.512, R2 = 0.990), and external validation demonstrated excellent predictive performance and reliability of the 3D-QSAR model. We designed eight novel molecules with higher inhibitory activities according to the three-dimensional equipotential fields and explored the interactions between the compounds and BTK by molecular docking, which showed that the novel molecules had higher binding affinities with BTK than the template molecule 18. Then, the results of molecular docking were further verified by MD simulation, which showed that amino acid residues such as Leu528, Val416, and Met477 played vital parts in the interaction, and the binding free energy analysis showed that the novel molecules had higher stability with BTK. Finally, the ADME/T properties were predicted for all of the novel compounds, and the results showed that the majority of them had favorable pharmacokinetic properties. Therefore, this study provides strong support for the development of novel BTK inhibitors.

Polymorphonuclear myeloid-derived suppressor cells play a proinflammatory role via TNF-α+ B cells through BAFF/BTK/NF-κB signalling pathway in the pathogenesis of collagen-induced arthritis mice

Although various studies have been performed on the function of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) in RA, the results were conflicting. Here we were trying to clarify the role of PMN-MDSCs in the pathogenesis of RA and its specific mechanisms. We detected the frequencies and counts of PMN-MDSCs, TNF-α+ B cells and Ki67+ B cells in spleen and inflamed joints of collagen-induced arthritis (CIA) mice using flow cytometry. The pathological role of PMN-MDSCs was examined by anti-Ly6G neutralizing antibodies against PMN-MDSCs or adoptive transfer of PMN-MDSCs. And the modulation of PMN-MDSCs on B cells was conducted by coculture assays, RNA-Seq, RT-qPCR, and so on. The mechanism of BAFF regulating B cells was verified through western blot and flow cytometry. PMN-MDSCs accumulated in the spleen and joints of CIA mice. PMN-MDSCs depletion could alleviate the arthritis severity, which was accompanied by decreased TNF-α secretion and proliferation of B cells. And its adoptive transfer also facilitated disease progress. Furthermore, PMN-MDSCs from CIA mice had higher expression level of BAFF, which regulated TNF-α expression, proliferation and apoptosis of B cells in vitro. What's more, BAFF promoted phosphorylation of BTK/NF-κB signalling pathway. And Ibrutinib (BTK inhibitor) could reverse the effect of BAFF on TNF-α expression of B cells. Our study suggested that PMN-MDSCs enhanced disease severity of CIA and manipulated TNF-α expression, proliferation and apoptosis of B cells via BAFF, furthermore, BAFF promoted TNF-α expression through BTK/NF-κB signalling pathway, which demonstrated a novel pathogenesis of PMN-MDSCs in CIA.

Predicting binding between 55 cannabinoids and 4,799 biological targets by in silico methods

Recently, there has been an increase in cannabis-derived products being marketed as foods, dietary supplements, and other consumer products. Cannabis contains over a hundred cannabinoids, many of which have unknown physiological effects. Since there are large numbers of cannabinoids, and many are not commercially available for in vitro testing, an in silico tool (Chemotargets Clarity software) was used to predict binding between 55 cannabinoids and 4,799 biological targets (enzymes, ion channels, receptors, and transporters). This tool relied on quantitative structure activity relationships (QSAR), structural similarity, and other approaches to predict binding. From this screening, 827 cannabinoid-target binding pairs were predicted, which included 143 unique targets. Many cannabinoids sharing core structures (cannabinoid "types") had similar binding profiles, whereas most cannabinoids containing carboxylic acid groups were similar without regards to their core structure. For some of the binding predictions (43), in vitro binding data were available, and they agreed well with in silico binding data (median fourfold difference in binding concentrations). Finally, clinical adverse effects associated with 22 predicted targets were identified from an online database (Clarivate Off-X), providing important insights on potential human health hazards. Overall, in silico biological target predictions are a rapid means to identify potential hazards due to cannabinoid-target interactions, and the data can be used to prioritize subsequent in vitro and in vivo testing.

Epstein-Barr virus and genetic risk variants as determinants of T-bet+ B cell-driven autoimmune diseases

B cells expressing the transcription factor T-bet are found to have a protective role in viral infections, but are also considered major players in the onset of different types of autoimmune diseases. Currently, the exact mechanisms driving such 'atypical' memory B cells to contribute to protective immunity or autoimmunity are unclear. In addition to general autoimmune-related factors including sex and age, the ways T-bet+ B cells instigate autoimmune diseases may be determined by the close interplay between genetic risk variants and Epstein-Barr virus (EBV). The impact of EBV on T-bet+ B cells likely relies on the type of risk variants associated with each autoimmune disease, which may affect their differentiation, migratory routes and effector function. In this hypothesis-driven review, we discuss the lines of evidence pointing to such genetic and/or EBV-mediated influence on T-bet+ B cells in a range of autoimmune diseases, including systemic lupus erythematosus (SLE) and multiple sclerosis (MS). We provide examples of how genetic risk variants can be linked to certain signaling pathways and are differentially affected by EBV to shape T-bet+ B-cells. Finally, we propose options to improve current treatment of B cell-related autoimmune diseases by more selective targeting of pathways that are critical for pathogenic T-bet+ B-cell formation.

The mTORC1 pathway participate in hyper-function of B cells in immune thrombocytopenia

B cell hyper-function plays an important role in the pathogenesis of immune thrombocytopenia (ITP), but the molecular mechanisms underlying such changes remain unclear. We sought to identify regulators of B cell dysfunction in ITP patients through transcriptome sequencing and the use of inhibitors. B cells were isolated from PBMC of 25 ITP patients for B cell function test and transcriptome sequencing. For the potential regulatory factors identified by transcriptome sequencing, the corresponding protein inhibitors were used to explore the regulatory effect of the regulatory factors on B cell dysfunction in vitro. In this study, increased antibody production, enhanced terminal differentiation and highly expressed costimulatory molecules CD80 and CD86 were found in B cells of patients with ITP. In addition, RNA sequencing revealed highly activated mTOR pathway in these pathogenic B cells, indicating that the mTOR pathway may be involved in B cell hyper-function. Furthermore, mTOR inhibitors rapamycin or Torin1 effectively blocked the activation of mTORC1 in B cells, resulting in reduce antibody secretion, impaired differentiation of B cells into plasmablasts and downregulation of costimulatory molecules. Interestingly, as an unspecific inhibitor of mTORC2 besides mTORC1, Torin1 did not show a stronger capacity to modulate B cell function than rapamycin, suggesting that the regulation of B cells by Torin1 may depend on blockade of mTORC1 rather than mTORC2 pathway. These results indicated that the activation of mTORC1 pathway is involved in B cell dysfunction in patients with ITP, and inhibition of mTORC1 pathway might be a potential therapeutic approach for ITP.

Structure of BTK kinase domain with the second-generation inhibitors acalabrutinib and tirabrutinib

Bruton's tyrosine kinase (BTK) is the target of the therapeutic agent, Ibrutinib, that treats chronic lymphocyte leukemia (CLL), mantle cell lymphoma (MCL) and other B cell malignancies. Ibrutinib is a first in class, covalent BTK inhibitor that limits B-cell survival and proliferation. Designing new inhibitors of BTK has been an important objective for advancing development of improved therapeutic agents against cancer and autoimmune disorders. Based on the success of Ibrutinib, several second-generation irreversible BTK inhibitors have been developed that exhibit fewer off-target effects. However, the binding-mode and their interaction with Btk have not been experimentally determined and evaluated at atomic resolution. Here we determined the first crystal structure of the BTK kinase domain in complex with acalabrutinib. In addition, we report a structure of the BTK/tirabrutinib complex and compare these structures with previously solved structures. The structures provide insight in the superior selectivity reported for acalabrutinb and guide future BTK inhibitor development.

Future landscape for the management of membranous nephropathy

Among all glomerular diseases, membranous nephropathy (MN) is perhaps the one in which major progress has been made in recent decades, in both the understanding of the pathogenesis and treatment. Despite the overall significant response rates to these therapies-particularly rituximab and cyclical regimen based on corticosteroids and cyclophosphamide-cumulative experience over the years has shown, however, that 20%-30% of cases may confront resistant disease. Thus, these unmet challenges in the treatment of resistant forms of MN require newer approaches. Several emerging new agents-developed primarily for the treatment of hematological malignancies or rheumatoid diseases-are currently being evaluated in MN. Herein we conducted a narrative review on future therapeutic strategies in the disease. Among the different novel therapies, newer anti-CD20 agents (e.g. obinutuzumab), anti-CD38 (e.g. daratumumab, felzartamab), immunoadsorption or anti-complement therapies (e.g. iptacopan) have gained special attention. In addition, several technologies and innovations developed primarily for cancer (e.g. chimeric antigen receptor T-cell therapy, sweeping antibodies) seem particularly promising. In summary, the future therapeutic landscape in MN seems encouraging and will definitely move the management of this disease towards a more precision-based approach.

Novel Therapeutic Strategies in the Treatment of Systemic Sclerosis

Systemic sclerosis is a connective tissue disease of unknown origin and with an unpredictable course, with both cutaneous and internal organ manifestations. Despite the enormous progress in rheumatology and clinical immunology, the background of this disease is largely unknown, and no specific therapy exists. The therapeutic approach aims to treat and preserve the function of internal organs, and this approach is commonly referred to as organ-based treatment. However, in modern times, data from other branches of medicine may offer insight into how to treat disease-related complications, making it possible to find new drugs to treat this disease. In this review, we present therapeutic options aiming to stop the progression of fibrotic processes, restore the aberrant immune response, stop improper signalling from proinflammatory cytokines, and halt the production of disease-related autoantibodies.

Discovery of Novel Bruton's Tyrosine Kinase PROTACs with Enhanced Selectivity and Cellular Efficacy

Bruton's tyrosine kinase (BTK) is a target for treating B-cell malignancies and autoimmune diseases, and several BTK inhibitors are already approved for use in humans. Heterobivalent BTK protein degraders are also in development, based on the premise that proteolysis targeting chimeras (PROTACs) may provide additional therapeutic benefits. However, most BTK PROTACs are based on the BTK inhibitor ibrutinib raising concerns about their selectivity profiles, given the known off-target effects of ibrutinib. Here, we disclose the discovery and in vitro characterization of BTK PROTACs based on the selective BTK inhibitor GDC-0853 and the cereblon recruitment ligand pomalidomide. PTD10 is a highly potent BTK degrader (DC50 0.5 nM) that inhibited cell growth and induced apoptosis at lower concentrations than the two parent molecules, as well as three previously reported BTK PROTACs, and had improved selectivity compared to ibrutinib-based BTK PROTACs.

Regulatory Mechanism of M1/M2 Macrophage Polarization in the Development of Autoimmune Diseases

Macrophages are innate immune cells in the organism and can be found in almost tissues and organs. They are highly plastic and heterogeneous cells and can participate in the immune response, thereby playing a crucial role in maintaining the immune homeostasis of the body. It is well known that undifferentiated macrophages can polarize into classically activated macrophages (M1 macrophages) and alternatively activated macrophages (M2 macrophages) under different microenvironmental conditions. The directions of macrophage polarization can be regulated by a series of factors, including interferon, lipopolysaccharide, interleukin, and noncoding RNAs. To elucidate the role of macrophages in various autoimmune diseases, we searched the literature on macrophages with the PubMed database. Search terms are as follows: macrophages, polarization, signaling pathways, noncoding RNA, inflammation, autoimmune diseases, systemic lupus erythematosus, rheumatoid arthritis, lupus nephritis, Sjogren's syndrome, Guillain-Barré syndrome, and multiple sclerosis. In the present study, we summarize the role of macrophage polarization in common autoimmune diseases. In addition, we also summarize the features and recent advances with a particular focus on the immunotherapeutic potential of macrophage polarization in autoimmune diseases and the potentially effective therapeutic targets.

Evaluation of BMS-986142, a reversible Bruton's tyrosine kinase inhibitor, for the treatment of rheumatoid arthritis: a phase 2, randomised, double-blind, dose-ranging, placebo-controlled, adaptive design study

BACKGROUND

Bruton's tyrosine kinase (BTK) is a promising biological target for rheumatoid arthritis treatment. This study examined safety, efficacy, and pharmacokinetics of BMS-986142, an oral, reversible BTK inhibitor. The aim was to compare the efficacy of BMS-986142 with placebo on a background of methotrexate in patients with moderate-to-severe rheumatoid arthritis and inadequate response to methotrexate.

METHODS

This phase 2, randomised, double-blind, dose-ranging, placebo-controlled, adaptive design study was conducted across 14 countries and 79 clinical sites. We recruited people aged 18 years or older with a documented diagnosis of rheumatoid arthritis at least 16 weeks before screening with an inadequate response to methotrexate with or without inadequate response to up to two tumour necrosis factor inhibitors. Participants were randomly assigned (1:1:1:1) to oral BMS-986142 (100 mg, 200 mg, or 350 mg) or placebo once daily for 12 weeks. Randomisation was done using an interactive voice response system and stratified by prior treatment status and geographical region. All participants, care providers, investigators, and outcome assessors were masked to treatment allocation. Co-primary endpoints were 20% and 70% improvement in American College of Rheumatology criteria (ACR20 and ACR70) at week 12. Primary endpoints were assessed in the efficacy analysis population (all randomised patients who received at least one dose of the study drug and did not discontinue the study). Safety endpoints were analysed in the as-treated analysis population, which included all patients who received at least one dose of the study drug (patients were grouped according to the treatment they actually received vs the treatment to which they were randomised). This trial was registered with ClinicalTrials.gov, number NCT02638948.

FINDINGS

Between Feb 24, 2016 and May 3, 2018, 248 patients were randomised (73 in the BMS-986142 100 mg group, 73 in the 200 mg group, 26 in the 350 mg group, and 75 in the placebo group; one post-randomisation exclusion); mean age was 56·7 years (SD 12·7); 214 (87%) of 247 were women, 33 (13%) were men, and 188 (76%) were White. Pre-specified interim analysis resulted in discontinuation of the 350 mg BMS-986142 dose due to elevated liver enzymes and absence of benefit versus placebo. Co-primary endpoints were not met. Response rates for ACR20 (placebo: 23 [31%] of 75; 100 mg: 26 [36%] of 73; 200 mg: 31 [42%] of 73) and ACR70 (placebo: three [4%] of 75; 100 mg: three [4%] of 73; 200 mg: seven [10%] of 73) were not significantly different to placebo; estimate of difference versus placebo for ACR20 was 4·9 (95% CI -10·2 to 20·1; p=0·52) for 100 mg and 11·8 (-3·6 to 27·2; p=0·14) for 200 mg, and for ACR70 the estimate of difference was 0·1 (-16·0 to 16·5; nominal p=1·00) for 100 mg and 5·6 (-10·5 to 21·9; nominal p=0·21) for 200 mg. Six patients experienced serious adverse events (four in the placebo group [mouth ulceration, open globe injury, rheumatoid arthritis flare, and endometrial adenocarcinoma] and two in the BMS-986142 100 mg group [angina pectoris and intestinal obstruction]); there were no deaths.

INTERPRETATION

Further investigation of BMS-986142 in people with rheumatoid arthritis is not warranted. An absence of clinical benefit in this study, together with other study results, highlights the need for additional research on the extent of BTK inhibition, treatment duration, and adequacy of drug distribution to inflammation sites, to understand the potential utility of BTK inhibition as a therapeutic strategy for rheumatoid arthritis.

FUNDING

Bristol Myers Squibb.

Emerging treatment for Sjögren's disease: a review of recent phase II and III trials

INTRODUCTION

Sjögren's Disease, SjD, is a systemic autoimmune disorder characterized by reduced function of the salivary and lacrimal glands. Patients suffer from dryness, fatigue, and pain and may present with or without extra-glandular organ involvement. Symptoms limit SjD patients' quality of life and are the most difficult to improve with therapy. SjD patients are heterogeneous and clustering them into biologically similar subgroups might improve the efficacy of therapies. The need for therapies that address both the symptoms and extra glandular organ involvement of SjD presents an unmet opportunity that has recently attracted a growing interest in the pharmaceutical industry.

AREAS COVERED

The goal of this report is to review recent phase II/III studies in SjD. To accomplish our goal, we performed a literature search for phase II/III studies and abstracts recently presented at conferences.

EXPERT OPINION

This review allows updates the reader on the multitude of recent phase II/III clinical trials. We speculate on how subtypes of SjD will drive future therapeutic targeting and inform pathogenesis.

Bruton tyrosine kinase inhibitors for multiple sclerosis

Current therapies for multiple sclerosis (MS) reduce both relapses and relapse-associated worsening of disability, which is assumed to be mainly associated with transient infiltration of peripheral immune cells into the central nervous system (CNS). However, approved therapies are less effective at slowing disability accumulation in patients with MS, in part owing to their lack of relevant effects on CNS-compartmentalized inflammation, which has been proposed to drive disability. Bruton tyrosine kinase (BTK) is an intracellular signalling molecule involved in the regulation of maturation, survival, migration and activation of B cells and microglia. As CNS-compartmentalized B cells and microglia are considered central to the immunopathogenesis of progressive MS, treatment with CNS-penetrant BTK inhibitors might curtail disease progression by targeting immune cells on both sides of the blood-brain barrier. Five BTK inhibitors that differ in selectivity, strength of inhibition, binding mechanisms and ability to modulate immune cells within the CNS are currently under investigation in clinical trials as a treatment for MS. This Review describes the role of BTK in various immune cells implicated in MS, provides an overview of preclinical data on BTK inhibitors and discusses the (largely preliminary) data from clinical trials.

Synthesis and Preclinical Evaluation of a Novel Fluorine-18-Labeled Tracer for Positron Emission Tomography Imaging of Bruton's Tyrosine Kinase

Bruton's tyrosine kinase (BTK) is a target for treating B-cell malignancies and autoimmune diseases. To aid in the discovery and development of BTK inhibitors and improve clinical diagnoses, we have developed a positron emission tomography (PET) radiotracer based on a selective BTK inhibitor, remibrutinib. [18F]PTBTK3 is an aromatic, 18F-labeled tracer that was synthesized in 3 steps with a 14.8 ± 2.4% decay-corrected radiochemical yield and ≥99% radiochemical purity. The cellular uptake of [18F]PTBTK3 was blocked up to 97% in JeKo-1 cells using remibrutinib or non-radioactive PTBTK3. [18F]PTBTK3 exhibited renal and hepatobiliary clearance in NOD SCID (non-obese diabetic/severe combined immunodeficiency) mice, and the tumor uptake of [18F]PTBTK3 in BTK-positive JeKo-1 xenografts (1.23 ± 0.30% ID/cc) was significantly greater at 60 min post injection compared to the tumor uptake in BTK-negative U87MG xenografts (0.41 ± 0.11% ID/cc). In the JeKo-1 xenografts, tumor uptake was blocked up to 62% by remibrutinib, indicating the BTK-dependent uptake of [18F]PTBTK3 in tumors.

Bruton's Tyrosine Kinase Inhibitors (BTKIs): Review of Preclinical Studies and Evaluation of Clinical Trials

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.

Discovery of structural diverse reversible BTK inhibitors utilized to develop a novel in vivo CD69 and CD86 PK/PD mouse model

For the past two decades, BTK a tyrosine kinase and member of the Tec family has been a drug target of significant interest due to its potential to selectively treat various B cell-mediated diseases such as CLL, MCL, RA, and MS. Owning to the challenges encountered in identifying drug candidates exhibiting the potency block B cell activation via BTK inhibition, the pharmaceutical industry has relied on the use of covalent/irreversible inhibitors to address this unmet medical need. Herein, we describe a medicinal chemistry campaign to identify structurally diverse reversible BTK inhibitors originating from HITS identified using a fragment base screen. The leads were optimized to improve the potency and in vivo ADME properties resulting in a structurally distinct chemical series used to develop and validate a novel in vivo CD69 and CD86 PD assay in rodents.

Discovery of orally active 1,4,5,6,8-pentaazaacenaphthylens as novel, selective, and potent covalent BTK inhibitors for the treatment of rheumatoid arthritis

Bruton's tyrosine kinase (BTK) plays a crucial role in adaptive and immune responses by modulating B-cell, Fc, toll-like, and chemokine receptor signaling pathways. BTK inhibition is a promising therapeutic approach for the treatment of inflammatory and autoimmune diseases. The development of novel, highly selective, and less toxic BTK inhibitors may be beneficial for the treatment of autoimmune diseases with unmet medical needs. In this study, structure-based drug design was used to discover a series of novel, potent, and selective covalent BTK inhibitors with a 1,4,5,6,8-pentaazaacenaphthylen scaffold. Among them, compound 36R exhibited high kinase selectivity, long target occupancy time, appropriate pharmacokinetic properties, and dose-dependent efficacy in a rat model of collagen-induced arthritis. Therefore, 36R is a novel BTK inhibitor requiring further development for the treatment of autoimmune diseases.

ASK120067 potently suppresses B-cell or T-cell malignancies in vitro and in vivo by inhibiting BTK and ITK

Hyperactivation of Bruton's tyrosine kinase (BTK) or interleukin-2-inducible T cell kinase (ITK) has been attributed to the pathogenesis of B-cell lymphoma or T-cell leukemia, respectively, which suggests that Bruton's tyrosine kinase and interleukin-2-inducible T cell kinase are critical targets for the treatment of hematological malignancies. We identified a novel third-generation epidermal growth factor receptor (EGFR) inhibitor, ASK120067 (limertinib) in our previous research, which has been applied as a new drug application against non-small cell lung cancer in China. In this work, we found that ASK120067 displayed potent in vitro inhibitory efficacy against Bruton's tyrosine kinase protein and interleukin-2-inducible T cell kinase protein via covalent binding. In cell-based assays, ASK120067 dose-dependently suppressed Bruton's tyrosine kinase phosphorylation and exhibited anti-proliferation potency by inducing apoptosis in numerous B-lymphoma cells. Meanwhile, it caused growth arrest and induced the apoptosis of T-cell leukemia cells by attenuating interleukin-2-inducible T cell kinase activation. Oral administration of ASK120067 led to significant tumor regression in B-cell lymphoma and T-cell leukemia xenograft models by weakening Bruton's tyrosine kinase and interleukin-2-inducible T cell kinase signaling, respectively. Taken together, our studies demonstrated that ASK120067 exerted preclinical anti-tumor activities against B-/T-cell malignancy by targeting BTK/ITK.

Existing and Investigational Medications for Refractory Chronic Spontaneous Urticaria: Safety, Adverse Effects, and Monitoring

Treatment of chronic spontaneous urticaria (CSU) is responsive to H1 antihistamines administered up to four times the recommended US Food and Drug Administration dose in approximately 50% of patients. However, when patients do not respond to these first-line agents, evidence-based guidelines using Grading of Recommendations, Assessment, Development, and Evaluations methodology have provided direction for second- and third-line treatments that can effectively treat patients with CSU. Some patients remain refractory to these advanced treatments; therefore, alternative treatments with a lower certainty of evidence may be necessary. Regardless of the therapies used to treat CSU patients, it is essential for clinicians to be knowledgeable about the mechanism of action, efficacy, and safety and monitoring recommendations of the treatments prescribed. This review provides a comprehensive review of the adverse effects and monitoring recommendations for agents in use for CSU treatment as well as those currently undergoing investigation for CSU treatment.

Targeting B cell dysregulation with emerging therapies in autoimmune demyelinating disorders

The depletion of B cells has proven to be beneficial in the treatment of autoimmune demyelinating disorders. The high efficacy of these therapies has highlighted the importance of B cells in autoimmunity and prompted investigations into specific B cell subsets that may be aberrant. Recently, a rise in the trialling of alternative B cell-targeting therapies that inhibit targets such as Bruton's tyrosine kinase, interleukin-6 receptor and fragment crystallisable neonatal receptor has also been observed. These agents interfere with specific dysregulated functions of B cells in contrast to the broad removal of many B cell subsets with depletion agents. The therapeutic benefit of these emerging agents will help delineate the contributions of B cells in demyelinating disorders and holds great potential for future treatment.

Epigenetic regulation of B cells and its role in autoimmune pathogenesis

B cells play a pivotal role in the pathogenesis of autoimmune diseases. Although previous studies have shown many genetic polymorphisms associated with B-cell activation in patients with various autoimmune disorders, progress in epigenetic research has revealed new mechanisms leading to B-cell hyperactivation. Epigenetic mechanisms, including those involving histone modifications, DNA methylation, and noncoding RNAs, regulate B-cell responses, and their dysregulation can contribute to the pathogenesis of autoimmune diseases. Patients with autoimmune diseases show epigenetic alterations that lead to the initiation and perpetuation of autoimmune inflammation. Moreover, many clinical and animal model studies have shown the promising potential of epigenetic therapies for patients. In this review, we present an up-to-date overview of epigenetic mechanisms with a focus on their roles in regulating functional B-cell subsets. Furthermore, we discuss epigenetic dysregulation in B cells and highlight its contribution to the development of autoimmune diseases. Based on clinical and preclinical evidence, we discuss novel epigenetic biomarkers and therapies for patients with autoimmune disorders.

Current Perspectives: Evidence to Date on BTK Inhibitors in the Management of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system leading to demyelination and neurodegeneration. Basic and translational studies have shown that B cells and myeloid cells are critical players for the development and course of the disease. Bruton’s tyrosine kinase (BTK) is essential for B cell receptor-mediated B cell activation and for normal B cell development and maturation. In addition to its role in B cells, BTK is also involved in several functions of myeloid cells. Although significant number of disease-modifying treatments (DMTs) have been approved for clinical use in MS patients, novel targeted therapies should be studied in refractory patients and patients with progressive forms of the disease. On the basis of its role in B cells and myeloid cells, BTK inhibitors can provide attractive therapeutic benefits for MS. In this article, we review the main effects of BTK inhibitors on different cell types involved in the pathogenesis of MS and summarise recent advances in the development of BTK inhibitors as novel therapeutic approaches in different MS clinical trials. Available data regarding the efficacy and safety of these drugs are described.

BTK inhibitors in the treatment of hematological malignancies and inflammatory diseases: mechanisms and clinical studies

Bruton's tyrosine kinase (BTK) is an essential component of multiple signaling pathways that regulate B cell and myeloid cell proliferation, survival, and functions, making it a promising therapeutic target for various B cell malignancies and inflammatory diseases. Five small molecule inhibitors have shown remarkable efficacy and have been approved to treat different types of hematological cancers, including ibrutinib, acalabrutinib, zanubrutinib, tirabrutinib, and orelabrutinib. The first-in-class agent, ibrutinib, has created a new era of chemotherapy-free treatment of B cell malignancies. Ibrutinib is so popular and became the fourth top-selling cancer drug worldwide in 2021. To reduce the off-target effects and overcome the acquired resistance of ibrutinib, significant efforts have been made in developing highly selective second- and third-generation BTK inhibitors and various combination approaches. Over the past few years, BTK inhibitors have also been repurposed for the treatment of inflammatory diseases. Promising data have been obtained from preclinical and early-phase clinical studies. In this review, we summarized current progress in applying BTK inhibitors in the treatment of hematological malignancies and inflammatory disorders, highlighting available results from clinical studies.

Safety and efficacy of tyrosine kinase inhibitors for the treatment of multiple sclerosis: A systematic review and meta-analysis from randomized controlled trials

Background

Multiple sclerosis (MS), an autoimmune disease, is characterized by inflammatory demyelinating lesions in the white matter of the central nervous system. Drugs targeting tyrosine kinase, a critical component of immune cell receptor signaling, have been developed to treat MS. However, the exact efficacy and safety of tyrosine kinase inhibitors (TKIs) are still controversial, and comprehensive analysis with a high level of evidence is needed.

Methods

Medline, Embase, Cochrane Library, and Clinicaltrials.gov for randomized controlled trials (RCTs) evaluating TKIs versus placebo for MS were searched up to April 1st, 2022. The risk ratio (RR) and mean difference (MD) or standard mean difference (SMD) were analyzed using dichotomous outcomes and continuous outcomes, respectively, with a random effect model.

Results

A total of 1,043 patients derived from four clinical trials were included to investigate the efficacy and safety of TKI therapy for MS. According to our analysis, TKIs decreased the cumulative number of gadolinium-enhancing lesions on T1-weighted MRI with the application of high dose (SMD = −0.61, 95% CI: −0.93 to −0.30, P = 0.0001). Meanwhile, TKIs prevented the expanded disability status scale (EDSS) from rising (MD = −0.10, 95% CI: −0.19 to −0.00, P = 0.046). In terms of MS relapse, TKIs have not revealed an obvious statistical difference compared with placebo (RR = 0.96, 95% CI: 0.55–1.65, P = 0.8755). However, more adverse events seem to occur in the TKIs group, both for adverse events (RR = 1.12, 95% CI: 1.05–1.19, P = 0.0009) and serious adverse events (RR = 1.91, 95% CI: 1.30–2.81, P = 0.001).

Conclusion

Tyrosine kinase inhibitors have shown promise in treating MS. Generally, TKIs that attain the effective dose demonstrate definite efficacy and have tolerable side effects. More clinical trials and validation are needed, and we anticipate that TKIs will be a viable alternative for MS patients.

Current therapeutic strategies and perspectives in refractory ITP: What have we learned recently?

Immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder featured by increased platelet destruction and deficient megakaryocyte maturation. First-line treatments include corticosteroids, intravenous immunoglobulin and intravenous anti-D immunoglobulin. Second-line treatments consist of rituximab, thrombopoietin receptor agonists and splenectomy. Although most patients benefit from these treatments, an individualized treatment approach is warranted due to the large heterogeneity among ITP patients. In addition, ITP patients may relapse and there remains a subset of patients who become refractory to treatments. The management of these refractory patients is still a challenge. This review aims to summarize emerging therapeutic approaches for refractory ITP in several categories according to their different targets, including macrophages, platelets/megakaryocytes, T cells, B cells, and endothelial cells. Moreover, current management strategies and combination regimens of refractory ITP are also discussed.