Bruton's Tyrosine Kinase Inhibitors in Multiple Sclerosis: Pioneering the Path Towards Treatment of Progression?

Multiple sclerosis in China: the current state of diagnosis and management

PURPOSE OF REVIEW

This comprehensive overview summarized the latest advances of multiple sclerosis (MS) in China, including the diagnostic and treatment challenges, research and future directions under health policy recommendations.

RECENT FINDINGS

Given the rising prevalence of MS in China during the past decades, it has emerged as a significant public health concern due to the extensive population and pronounced disparities between urban and rural areas. The clinical manifestations of MS patients in China can be various due to the nation's diversity and evolving environmental factors. Advances in diagnostic practices, including the advances under 7T MRI radiological assessments, have enhanced the precision of MS diagnosis. Despite the introduction of disease-modifying therapeutic agents and the support of healthcare policies offering patients a wider range of treatment options, multiple ongoing research efforts and clinical trials will provide additional evidence. The ongoing China National Registry of Neuro-Inflammatory Diseases study (NCT05154370) holds promise for further enhancing the management of MS patients in China.

SUMMARY

Improved recognition and management of MS in China have been facilitated, encompassing both prompt diagnosis and diverse treatment options. Simultaneously, research efforts and large-scale cohort studies have significantly advanced the overall status in this field.

Evobrutinib mitigates neuroinflammation after ischemic stroke by targeting M1 microglial polarization via the TLR4/Myd88/NF-κB pathway

BACKGROUND

Evobrutinib, a third-generation Bruton's tyrosine kinase (BTK) inhibitor, shows great promise for treating neuroinflammatory diseases due to its small molecular size, ease of absorption, and ability to cross the blood-brain barrier. Although previous studies have confirmed significant BTK expression in microglia, the potential of Evobrutinib to treat ischemic stroke by modulating microglial function and its underlying mechanisms remain to be elucidated.

METHODS

Male C57BL/6 mice with cerebral ischemia was established to evaluate the effects of oral Evobrutinib treatment. Assessments included TTC staining, behavioral experiments, and pathological examinations were used to evaluate cerebral ischemic injury. Western Blot, flow cytometry, and qPCR were employed to monitor changes in BTK and pBTK expression in microglia and the impact of Evobrutinib on neuroinflammation following the stroke. In vitro, primary microglia were generated to determine the effects of Evobrutinib on the TLR4/ Myd88/NF-κB pathway and on the polarization of microglial subtypes.

RESULTS

The expression of BTK and pBTK is upregulated in microglia under conditions of cerebral ischemia and oxygen-glucose deprivation (OGD). Evobrutinib treatment not only reduced infarct volume in mice but also ameliorated pathological damage and facilitated neurological function recovery. Flow cytometry revealed that Evobrutinib decreased inflammatory cell infiltration and promoted M2 microglia polarization post-stroke. In vitro studies demonstrated that Evobrutinib downregulated the proportion of pro-inflammatory microglia and curtailed the secretion of inflammatory factors under OGD conditions. Mechanistically, Evobrutinib attenuated the OGD-induced upregulation of TLR4/Myd88/NF-κB expression, an effect that was further enhanced by the addition of the TLR4 pathway inhibitor TAK242.

CONCLUSIONS

Evobrutinib inhibits the expression and activation of BTK in microglia, reducing M1 microglia-mediated neuroinflammation and alleviating ischemic injury following stroke. This effect is mechanistically linked to the inhibition of TLR4/Myd88/NF-κB-mediated M1 polarization of microglia.

2-Hydroxy-4-n-octyloxybenzophenone induces developmental neurotoxicity and multiple sclerosis-like symptoms through cacna1a regulated Ca2 + inward flow and microglial activation

2-Hydroxy-4-n-octyloxybenzophenone (UV-531) is a UV absorber widely used in infrastructure, cosmetics, and rubber products. The previous study found that UV-531 exposure irritate the skin and interfere with androgen secretion. However, the developmental toxicity and neurotoxic effects of UV-531 are still at an exploratory stage, and the effects of UV-531 on the environment and living organisms need to be further explored. Here, we exposed zebrafish to environmental relevant doses of UV-531 (0.1, 0.2, 0.4, 0.8 and 1.6 μg/L) and observed no significant developmental toxicity, but significant neurotoxicity. We assessed locomotor ability and responsiveness of zebrafish by general locomotion and light/dark challenge. Changes in dopaminergic (DA) neurons were observed using transgenic zebrafish slc18a2:GFP. Changes in cerebral vessels and blood-brain barrier (BBB) were observed using transgenic zebrafish fli1:GFP. Gene expression was detected by transcriptome and real-time qPCR. The effect of UV-531 on calcium homeostasis was determined by measuring Ca2+ levels. Microglia status was assessed by in situ hybridization. It was observed that UV-531 treatment resulted in a reduced locomotor activity, DA neurons injury, cerebral vessels damage, BBB leakage, calcium homeostasis imbalance, and abnormal expression of genes related to neurodevelopment and function. RNA-seq results indicated that Ca2+ import across plasma membrane was highly associated with UV-531-induced developmental neurotoxicity and cacna1aa and cacna1ab were key regulators. These findings suggest that UV-531 induced calcium homeostasis imbalance caused by upregulating cacna1aa and cacna1ab may contribute to multiple sclerosis (MS). Accordingly, UV-531 exposure triggered neuroinflammation, injured myelin, ultimately leading to the development of MS-like symptoms, including decreased responsiveness to external stimuli, microglia activation, dysregulation of mbp and MS-related genes ahsg1, btg1, and grna. In summary, exposure to environmental relevant doses of UV-531 caused neurological damage and led to MS-like symptoms. Given the effects of UV-531 on the organisms, a safe dose range should be established.

A Window into New Insights on Progression Independent of Relapse Activity in Multiple Sclerosis: Role of Therapies and Current Perspective

In multiple sclerosis (MS), there is significant evidence indicating that both progression independent of relapse activity (PIRA) and relapse-related worsening events contribute to the accumulation of progressive disability from the onset of the disease and throughout its course. Understanding the compartmentalized pathophysiology of MS would enhance comprehension of disease progression mechanisms, overcoming the traditional distinction in phenotypes. Smoldering MS activity is thought to be maintained by a continuous interaction between the parenchymal chronic processes of neuroinflammation and neurodegeneration and the intrathecal compartment. This review provides a comprehensive and up-to-date overview of the neuropathological and immunological evidence related to the mechanisms underlying PIRA phenomena in MS, with a focus on studies investigating the impact of currently available therapies on these complex mechanisms.

[New pathogenic treatments for myasthenia gravis]

Myasthenia gravis (MG) is an autoimmune disease caused by the production of specific autoantibodies to various components of the neuromuscular synapse, leading to muscle weakness and disabling fatigue. Treatment of MG aims to stop the symptoms and inhibit the triggers of the autoimmune process. For a long time, MG treatment included anticholinesterase agents and nonspecific immunosuppressive and immunomodulatory therapies used alone or in combinations: glucocorticosteroids, cytostatics, plasmapheresis, and intravenous immunoglobulin. Despite the fact that the above drugs are widely used in the treatment of MG, they can cause unacceptable side effects with long-term use and also are not consistent in induction of remission. The search for new effective and safe therapies for MG, especially refractory types that do not respond to standard therapy, is an urgent task. Due to advances in biotechnology and the emergence of new types of drugs, monoclonal antibodies or fusion proteins, targeted MG immunotherapy has been developed for specific pathogenetic targets. The presented review describes targeted MG therapies that are already approved In Russia and other countries, as well as those at different stages of development. Most targeted agents have some advantages over traditional immunosuppressive therapy: rapid onset of action, long-term remission, and minimal side effects. Currently, eculizumab and ravulizumab are approved In Russia.

The emerging role of microglia in the development and therapy of multiple sclerosis

Microglia are innate immune cells that maintain homeostasis of the central nervous system (CNS) and affect various neurodegenerative diseases, especially multiple sclerosis (MS). MS is an autoimmune disease of the CNS characterized by persistent inflammation, diffuse axonal damage, and microglia activation. Recent studies have shown that microglia are extremely related to the pathological state of MS and play an important role in the development of MS. This article reviews the multiple roles of microglia in the progression of MS, including the regulatory role of microglia in inflammation, remyelination, oxidative stress, the influence of phagocytosis and antigen-presenting capacity of microglia, and the recent progress by using microglia as a target for MS therapy. Microglia modulation may be a potential way for better MS therapy.

Towards Treating Multiple Sclerosis Progression

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS). In most patients, the disease starts with an acute onset followed by a remission phase, subsequent relapses and a later transition to steady chronic progression. In a minority of patients, this progressive phase develops from the beginning. MS relapses are characterized predominantly by the de novo formation of an inflammatory CNS lesion and the infiltration of immune cells, whereas the pathological features of MS progression include slowly expanding lesions, global brain atrophy and an inflammatory response predominantly mediated by macrophages/microglia. Importantly, this CNS-intrinsic pathophysiology appears to initiate early during the relapsing-remitting disease phase, while it turns into the key clinical MS feature in later stages. Currently approved disease-modifying treatments for MS are effective in modulating peripheral immunity by dampening immune cell activity or preventing the migration of immune cells into the CNS, resulting in the prevention of relapses; however, they show limited success in halting MS progression. In this manuscript, we first describe the pathological mechanisms of MS and summarize the approved therapeutics for MS progression. We also review the treatment options for progressive MS (PMS) that are currently under investigation. Finally, we discuss potential targets for novel treatment strategies in PMS.

Primary Progressive Multiple Sclerosis-A Key to Understanding and Managing Disease Progression

Primary progressive multiple sclerosis (PPMS), the least frequent type of multiple sclerosis (MS), is characterized by a specific course and clinical symptoms, and it is associated with a poor prognosis. It requires extensive differential diagnosis and often a long-term follow-up before its correct recognition. Despite recent progress in research into and treatment for progressive MS, the diagnosis and management of this type of disease still poses a challenge. Considering the modern concept of progression "smoldering" throughout all the stages of disease, a thorough exploration of PPMS may provide a better insight into mechanisms of progression in MS, with potential clinical implications. The goal of this study was to review the current evidence from investigations of PPMS, including its background, clinical characteristics, potential biomarkers and therapeutic opportunities. Processes underlying CNS damage in PPMS are discussed, including chronic immune-mediated inflammation, neurodegeneration, and remyelination failure. A review of potential clinical, biochemical and radiological biomarkers is presented, which is useful in monitoring and predicting the progression of PPMS. Therapeutic options for PPMS are summarized, with approved therapies, ongoing clinical trials and future directions of investigations. The clinical implications of findings from PPMS research would be associated with reliable assessments of disease outcomes, improvements in individualized therapeutic approaches and, hopefully, novel therapeutic targets, relevant for the management of progression.

Novel and Emerging Treatments to Target Pathophysiological Mechanisms in Various Phenotypes of Multiple Sclerosis

The objective is to comprehensively review novel pharmacotherapies used in multiple sclerosis (MS) and the possibilities they may carry for therapeutic improvement. Specifically, we discuss pathophysiological mechanisms worth targeting in MS, ranging from well known targets, such as autoinflammation and demyelination, to more novel and advanced targets, such as neuroaxonal damage and repair. To set the stage, a brief overview of clinical MS phenotypes is provided, followed by a comprehensive recapitulation of both clinical and paraclinical outcomes available to assess the effectiveness of treatments in achieving these targets. Finally, we discuss various promising novel and emerging treatments, including their respective hypothesized modes of action and currently available evidence from clinical trials. SIGNIFICANCE STATEMENT: This comprehensive review discusses pathophysiological mechanisms worth targeting in multiple sclerosis. Various promising novel and emerging treatments, including their respective hypothesized modes of action and currently available evidence from clinical trials, are reviewed.

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.

BTK inhibition limits microglia-perpetuated CNS inflammation and promotes myelin repair

In multiple sclerosis (MS), persisting disability can occur independent of relapse activity or development of new central nervous system (CNS) inflammatory lesions, termed chronic progression. This process occurs early and it is mostly driven by cells within the CNS. One promising strategy to control progression of MS is the inhibition of the enzyme Bruton's tyrosine kinase (BTK), which is centrally involved in the activation of both B cells and myeloid cells, such as macrophages and microglia. The benefit of BTK inhibition by evobrutinib was shown as we observed reduced pro-inflammatory activation of microglia when treating chronic experimental autoimmune encephalomyelitis (EAE) or following the adoptive transfer of activated T cells. Additionally, in a model of toxic demyelination, evobrutinib-mediated BTK inhibition promoted the clearance of myelin debris by microglia, leading to an accelerated remyelination. These findings highlight that BTK inhibition has the potential to counteract underlying chronic progression of MS.

Clinical trials for progressive multiple sclerosis: progress, new lessons learned, and remaining challenges

Despite the success of disease-modifying treatments in relapsing multiple sclerosis, for many individuals living with multiple sclerosis, progressive disability continues to accrue. How to interrupt the complex pathological processes underlying progression remains a daunting and ongoing challenge. Since 2014, several immunomodulatory approaches that have modest but clinically meaningful effects have been approved for the management of progressive multiple sclerosis, primarily for people who have active inflammatory disease. The approval of these drugs required large phase 3 trials that were sufficiently powered to detect meaningful effects on disability. New classes of drug, such as Bruton tyrosine-kinase inhibitors, are coming to the end of their trial stages, several candidate neuroprotective compounds have been successful in phase 2 trials, and innovative approaches to remyelination are now also being explored in clinical trials. Work continues to define intermediate outcomes that can provide results in phase 2 trials more quickly than disability measures, and more efficient trial designs, such as multi-arm multi-stage and futility approaches, are increasingly being used. Collaborations between patient organisations, pharmaceutical companies, and academic researchers will be crucial to ensure that future trials maintain this momentum and generate results that are relevant for people living with progressive multiple sclerosis.

Clinical and Treatment Considerations for the Pediatric and Aging Patients with Multiple Sclerosis

Chronologic aging is associated with multiple pathologic and immunologic changes that impact the clinical course of multiple sclerosis (MS). Clinical phenotypes evolve across the lifespan, from a highly inflammatory course in the very young to a predominantly neurodegenerative phenotype in older patients. Thus, unique clinical considerations arise for the diagnosis and management of the two age extremes of pediatric and geriatric MS populations. This review covers epidemiology, diagnosis, and treatment strategies for these populations with nuanced discussions on therapeutic approaches to effectively care for patients living with MS at critical transition points during their lifespan.

[Current and innovative Approaches to Multiple Sclerosis Therapy]

The landscape of immunotherapies in the management of Multiple Sclerosis (MS) is currently particularly dynamic. Over 21 immunotherapeutic options are approved by the European Meidcines Agency (EMA), Food and Drug Administration (FDA) and newer approaches are ongoing in clinical trials. With advancements in the understanding of MS pathophysiology and further development of diagnosis criteria, newer and more specific disease-modifying therapies (DMTs) have emerged in recent years. The selection and timing of proper therapeutic approaches is increasingly complex. We provide an overview of the available immunotherapies for a personalized MS treatment and discuss practical insights into their application. The importance of early intervention, distinction between escalation and induction approaches, and consideration of high-efficacy treatments for specific patient groups are in discussed. We emphasize the significance of a patient-centered approach, taking into account various factors such as comorbidities, family planning, administration preferences and potential side effects in treatment decision-making.

Toward identifying key mechanisms of progression in multiple sclerosis

A major therapeutic goal in the treatment of multiple sclerosis (MS) is to prevent the accumulation of disability over an often decades-long disease course. Disability progression can result from acute relapses as well as from CNS intrinsic parenchymal disintegration without de novo CNS lesion formation. Research focus has shifted to progression not associated with acute inflammation, as it is not sufficiently controlled by currently available treatments. This review outlines how recent advances in the understanding of the pathogenesis of progressive MS have been facilitated by the development of more precise, less static pathogenetic concepts of progressive MS, as well as by new techniques for the analysis of region-specific proteomic and transcriptomic signatures in the human CNS. We highlight key drivers of MS disease progression and potential targets in its treatment.

Resisting the Resistance: Navigating BTK Mutations in Chronic Lymphocytic Leukemia (CLL)

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.

How myeloid cells shape experimental autoimmune encephalomyelitis: At the crossroads of outside-in immunity

Experimental autoimmune encephalomyelitis (EAE) is an animal model of central nervous system (CNS) autoimmunity. It is most commonly used to mimic aspects of multiple sclerosis (MS), a demyelinating disorder of the human brain and spinal cord. The innate immune response displays one of the core pathophysiological features linked to both the acute and chronic stages of MS. Hence, understanding and targeting the innate immune response is essential. Microglia and other CNS resident MUs, as well as infiltrating myeloid cells, diverge substantially in terms of both their biology and their roles in EAE. Recent advances in the field show that antigen presentation, as well as disease-propagating and regulatory interactions with lymphocytes, can be attributed to specific myeloid cell types and cell states in EAE lesions, following a distinct temporal pattern during disease initiation, propagation and recovery. Furthermore, single-cell techniques enable the assessment of characteristic proinflammatory as well as beneficial cell states, and identification of potential treatment targets. Here, we discuss the principles of EAE induction and protocols for varying experimental paradigms, the composition of the myeloid compartment of the CNS during health and disease, and systematically review effects on myeloid cells for therapeutic approaches in EAE.

Investigation of Fenebrutinib Metabolism and Bioactivation Using MS3 Methodology in Ion Trap LC/MS

Fenebrutinib is an orally available Bruton tyrosine kinase inhibitor. It is currently in multiple phase III clinical trials for the management of B-cell tumors and autoimmune disorders. Elementary in-silico studies were first performed to predict susceptible sites of metabolism and structural alerts for toxicities by StarDrop WhichP450™ module and DEREK software; respectively. Fenebrutinib metabolites and adducts were characterized in-vitro in rat liver microsomes (RLM) using MS3 method in Ion Trap LC-MS/MS. Formation of reactive and unstable intermediates was explored using potassium cyanide (KCN), glutathione (GSH) and methoxylamine as trapping nucleophiles to capture the transient and unstable iminium, 6-iminopyridin-3(6H)-one and aldehyde intermediates, respectively, to generate a stable adducts that can be investigated and analyzed using mass spectrometry. Ten phase I metabolites, four cyanide adducts, five GSH adducts and six methoxylamine adducts of fenebrutinib were identified. The proposed metabolic reactions involved in formation of these metabolites are hydroxylation, oxidation of primary alcohol to aldehyde, n-oxidation, and n-dealkylation. The mechanism of reactive intermediate formation of fenebrutinib can provide a justification of the cause of its adverse effects. Formation of iminium, iminoquinone and aldehyde intermediates of fenebrutinib was characterized. N-dealkylation followed by hydroxylation of the piperazine ring is proposed to cause the bioactivation to iminium intermediates captured by cyanide. Oxidation of the hydroxymethyl group on the pyridine moiety is proposed to cause the generation of reactive aldehyde intermediates captures by methoxylamine. N-dealkylation and hydroxylation of the pyridine ring is proposed to cause formation of iminoquinone reactive intermediates captured by glutathione. FBB and several phase I metabolites are bioactivated to fifteen reactive intermediates which might be the cause of adverse effects. In the future, drug discovery experiments utilizing this information could be performed, permitting the synthesis of new drugs with better safety profile. Overall, in silico software and in vitro metabolic incubation experiments were able to characterize the FBB metabolites and reactive intermediates using the multistep fragmentation capability of ion trap mass spectrometry.

B cell targeted therapies in inflammatory autoimmune disease of the central nervous system

Cumulative evidence along several lines indicates that B cells play an important role in the pathological course of multiple sclerosis (MS), neuromyelitisoptica spectrum disorders (NMOSD) and related CNS diseases. This has prompted extensive research in exploring the utility of targeting B cells to contain disease activity in these disorders. In this review, we first recapitulate the development of B cells from their origin in the bone marrow to their migration to the periphery, including the expression of therapy-relevant surface immunoglobulin isotypes. Not only the ability of B cells to produce cytokines and immunoglobulins seems to be essential in driving neuroinflammation, but also their regulatory functions strongly impact pathobiology. We then critically assess studies of B cell depleting therapies, including CD20 and CD19 targeting monoclonal antibodies, as well as the new class of B cell modulating substances, Bruton´s tyrosinekinase (BTK) inhibitors, in MS, NMOSD and MOGAD.