Rapid depletion of B lymphocytes by ultra-low-dose rituximab delivered intrathecally

Three cases with chronic obsessive compulsive disorder report gains in wellbeing and function following rituximab treatment

Immunological aetiology is supported for a subgroup with obsessive compulsive disorder (OCD) and conceptualized as autoimmune OCD. The longitudinal clinical course is detailed for three severely ill cases with OCD and indications of immunological involvement with off-label rituximab treatment every six months. All cases showed clear and sustained gains regarding symptom burden and function for over 2.5 years. Brief Psychiatric Rating Scale and Yale-Brown Obsessive-Compulsive Inventory Scale scores decreased 67-100% and 44-92%, respectively. These complex cases, prior to rituximab, had very low functioning and disease duration has been eight, nine and 16 years respectively. All three patients had been unsuccessfully treated with at least two antidepressants or anxiolytics, one neuroleptic and cognitive behavioural therapy. Clinical phenotypes and findings were suggestive of possible autoimmune OCD. Indirect immunohistochemistry detected cerebral spinal fluid (CSF) antibodies in all three cases including a novel anti-neuronal staining pattern against mouse thalamic cells. Exploratory analyses of CSF markers and proteomics identified elevated levels of sCD27 and markers indicative of complement pathway activation when compared to CSF from healthy controls. Multidisciplinary collaboration, advanced clinical investigations and rituximab treatment are feasible in a psychiatric setting. The case histories provide a proof of principle for the newly proposed criteria for autoimmune OCD. The findings suggest that clinical red flags and biological measures may predict rituximab response in chronic treatment-resistant OCD. The report provides orientation that may inform the hypotheses and design of future treatment trials.

Anti-CD20 monoclonal antibodies in multiple sclerosis: Rethinking the current treatment strategy

Anti-CD20 monoclonal antibodies are highly-effective B-cell-depleting therapies in multiple sclerosis (MS). These treatments have expanded the arsenal of highly effective disease-modifying therapies, and have changed the landscape in understanding the pathophysiology of MS and the natural course of the disease. Nevertheless, these treatments come at the cost of immunosuppression and risk of serious infections, diminished vaccination response and treatment-related secondary hypogammaglobulinemia. However, the COVID pandemic has given way to a possibility of readapting these therapies, with most notably extended dosing intervals. While these new strategies show efficacy in maintaining inflammatory MS disease control, and although it is tempting to speculate that tailoring CD20 therapies will reduce the negative outcomes of long-term immunosuppression, it is unknown whether they provide meaningful benefit in reducing the risk of treatment-related secondary hypogammaglobulinemia and serious infections. This review highlights the available anti-CD20 therapies that are available for treating MS patients, and sheds light on encouraging data, which propose that tailoring anti-CD20 monoclonal antibodies is the next step in rethinking the current treatment strategy.

Direct Cell Death Induced by CD20 Monoclonal Antibodies on B Cell Lymphoma Cells Revealed by New Protocols of Analysis

CD20 monoclonal antibodies (mAbs) eliminate B cells in several clinical contexts. At least two of these Abs, obinutuzumab (OBI) and rituximab (RTX), induce quick elimination of targets and put cancer patients at risk of tumor lysis syndrome (TLS) within 12-24 h of the first dose. The mechanisms of killing can require the recruiting of effector mechanisms from the patient's immune system, but they can induce direct killing as well. This can be more rapid than recruiting cellular effectors and/or complement. We showed here that OBI and RTX induce quick (<1 h) and high (up to 60% for OBI) killing of two different B cell lines. This was unveiled by using two different techniques that circumvent cell centrifugation steps: a Muse^® Cell Analyzer-based approach and a direct examination of the cells' physical properties by using forward scatter (FS) area and side scatter (SS) area by flow cytometry. These results excluded the presence of aggregates and were also confirmed by developing a normalized survival ratio based on the co-incubation of RTX- and OBI-sensitive cells with MOLM-13, an insensitive cell line. Finally, this normalized survival ratio protocol confirmed the RTX- and OBI-direct killing on primary tumor B cells from B cell chronic lymphocytic leukemia (B-CLL) and Non-Hodgkin's lymphoma (NHL) patients. Moreover, we unveiled that direct killing is higher than previously expected and absent in patients' samples at relapse. We also observed that these mAbs, prior to increasing intracellular calcium levels, decrease calcium entry, although manipulating calcium levels did not affect their cytotoxicity. Altogether, our results show that direct killing is a major mechanism to induce cell death by RTX and OBI mAbs.

Intrathecal delivery and its applications in leptomeningeal disease

Intrathecal delivery (IT) of opiates into the cerebrospinal fluid (CSF) for anesthesia and pain relief has been used clinically for decades, but this relatively straightforward approach of bypassing the blood-brain barrier has been underutilized for other indications because of its lack of utility in delivering small lipid-soluble drugs. However, emerging evidence suggests that IT drug delivery be an efficacious strategy for the treatment of cancers in which there is leptomeningeal spread of disease. In this review, we discuss CSF flow dynamics and CSF clearance pathways in the context of intrathecal delivery. We discuss human and animal studies of several new classes of therapeutic agents-cellular, protein, nucleic acid, and nanoparticle-based small molecules-that may benefit from IT delivery. The complexity of the CSF compartment presents several key challenges in predicting biodistribution of IT-delivered drugs. New approaches and strategies are needed that can overcome the high rates of turnover in the CSF to reach specific tissues or cellular targets.

Contribution of B cells to cortical damage in multiple sclerosis

Multiple sclerosis is associated with lesions not just in the white matter, but also involving the cortex. Cortical involvement has been linked to greater disease severity and hence understanding the factor underlying cortical pathology could help identify new therapeutic strategies for multiple sclerosis. The critical role of B cells in multiple sclerosis has been clarified by multiple pivotal trials of B cell depletion in people with multiple sclerosis. The presence of B cell rich areas of meningeal inflammation in multiple sclerosis has been identified at all stages of multiple sclerosis. Leptomeningeal inflammation is associated with greater extent of cortical demyelination and neuronal loss and with greater disease severity. Recent studies have identified several potential mechanisms by which B cells may mediate cortical injury including antibody production, extracellular vesicles containing neurotoxic substances and production of pro-inflammatory cytokines. Additionally, B cells may indirectly mediate cortical damage through effects on T cells, macrophages or microglia. Several animal models replicate the meningeal inflammation and cortical injury noted in people with multiple sclerosis. Studies in these models have identified BTK inhibition and type II anti-CD20 antibodies as potential agents that can impact meningeal inflammation. Trials of anti-CD20 monoclonal antibodies in people with multiple sclerosis have unsuccessfully attempted to eliminate B cells in the leptomeninges. New strategies to target B cells in multiple sclerosis include BTK inhibition and cell-based therapies aimed at B cells infected with Epstein Barr virus. Future studies will clarify the mechanisms by which B cells mediate cortical injury and treatment strategies that can target B cells in the leptomeninges and CNS parenchyma.

Antibody Therapies in Autoimmune Encephalitis

Autoimmune encephalitis (AE) comprises a heterogeneous group of disorders in which the host immune system targets self-antigens expressed in the central nervous system. The most conspicuous example is an anti-N-methyl-D-aspartate receptor encephalitis linked to a complex neuropsychiatric syndrome. Current treatment of AE is based on immunotherapy and has been established according to clinical experience and along the concept of a B cell-mediated pathology induced by highly specific antibodies to neuronal surface antigens. In general, immunotherapy for AE follows an escalating approach. When first-line therapy with steroids, immunoglobulins, and/or plasma exchange fails, one converts to second-line immunotherapy. Alkylating agents could be the first choice in this stage. However, due to their side effect profile, most clinicians give preference to monoclonal antibodies (mAbs) directed at B cells such as rituximab. Newer mAbs might be added as a third-line therapy in the future, or be given even earlier if shown effective. In this chapter, we will discuss mAbs targeting B cells (rituximab, ocrelizumab, inebulizumab, daratumumab), IL-6 (tocilizumab, satralizumab), the neonatal Fc receptor (FCRn) (efgartigimod, rozanolixizumab), and the complement cascade (eculizumab).

Rituximab for the treatment of multiple sclerosis: a review

In the last decades, evidence suggesting the direct or indirect involvement of B cells on multiple sclerosis (MS) pathogenesis has accumulated. The increased amount of data on the efficacy and safety of B-cell-depleting therapies from several studies has suggested the addition of these drugs as treatment options to the current armamentarium of disease modifying therapies (DMTs) for MS. Particularly, rituximab (RTX), a chimeric monoclonal antibody directed at CD20 positive B lymphocytes resulting in cell-mediated apoptosis, has been demonstrated to reduce inflammatory activity, incidence of relapses and new brain lesions on magnetic resonance imaging (MRI) in patients with relapsing-remitting MS (RRMS). Additional evidence also demonstrated that patients with progressive MS (PMS) may benefit from RTX, which also showed to be well tolerated, with acceptable safety risks and favorable cost-effectiveness profile.Despite these encouraging results, RTX is currently approved for non-Hodgkin's lymphoma, chronic lymphocytic leukemia, several forms of vasculitis and rheumatoid arthritis, while it can only be administered off-label for MS treatment. Between Northern European countries exist different rules for using not licensed drug for treating MS. The Sweden MS register reports a high rate (53.5%) of off-label RTX prescriptions in relation to other annually started DMTs to treat MS patients, while Danish and Norwegian neurologists have to use other anti-CD20 drugs, as ocrelizumab, in most of the cases.In this paper, we review the pharmacokinetics, pharmacodynamics, clinical efficacy, safety profile and cost effectiveness aspects of RTX for the treatment of MS. Particularly, with the approval of new anti-CD20 DMTs, the recent worldwide COVID-19 emergency and the possible increased risk of infection with this class of drugs, this review sheds light on the use of RTX as an alternative treatment option for MS management, while commenting the gaps of knowledge regarding this drug.

B cells in multiple sclerosis - from targeted depletion to immune reconstitution therapies

Increasing evidence indicates the involvement of B cells in the pathogenesis of multiple sclerosis (MS), but their precise roles are unclear. In this Review, we provide an overview of the development and physiological functions of B cells and the main mechanisms through which B cells are thought to contribute to CNS autoimmunity. In MS, abnormalities of B cell function include pro-inflammatory cytokine production, defective B cell regulatory function and the formation of tertiary lymphoid-like structures in the CNS, which are the likely source of abnormal immunoglobulin production detectable in the cerebrospinal fluid. We also consider the hypothesis that Epstein-Barr virus (EBV) is involved in the B cell overactivation that leads to inflammatory injury to the CNS in MS. We also review the immunological effects - with a focus on the effects on B cell subsets - of several successful therapeutic approaches in MS, including agents that selectively deplete B cells (rituximab, ocrelizumab and ofatumumab), agents that less specifically deplete lymphocytes (alemtuzumab and cladribine) and autologous haematopoietic stem cell transplantation, in which the immune system is unselectively ablated and reconstituted. We consider the insights that these effects on B cell populations provide and their potential to further our understanding and targeting of B cells in MS.

No Early Effect of Intrathecal Rituximab in Progressive Multiple Sclerosis (EFFRITE Clinical Trial)

Background

The progressive phase of multiple sclerosis (MS) is characterized by an intrathecal (IT) compartmentalization of inflammation, involving B-cells within meningeal follicles, and resisting all the available immunosuppressive treatments. A new therapeutic paradigm may be to target this inflammation by injecting immunosuppressive drugs inside the central nervous system compartment.

Methods

We designed a single-center, open-label, randomized, controlled, phase II study designed to evaluate the safety and efficacy of IT rituximab in progressive MS (EFFRITE trial; ClinicalTrial Registration NCT02545959). Patients were randomized into three arms (1 : 1 : 1): control group, IT rituximab (20 mg, IT) group, and intravenous+IT (IV+IT) group. The main outcome was a change in levels of CSF biomarkers of inflammation (osteopontin). Secondary outcomes were changes in levels of CSF biomarkers of axonal loss (neurofilament light chain) and clinical and MRI changes.

Results

Ten patients were included (2 : 4 : 4). No adverse event occurred. OPN level remained stable in CSF at each time point, whereas NFL had slightly decreased (-8.7%) at day 21 (p = 0.02). Clinical parameters remained stable and leptomeningeal enhancements remained unchanged.

Conclusion

Clinical outcome and biomarkers of inflammation were not dramatically modified after IT injection of rituximab, probably due to its limited efficiency in CSF. Drug issues for future studies are discussed.

Imaging meningeal inflammation in CNS autoimmunity identifies a therapeutic role for BTK inhibition

Leptomeningeal inflammation in multiple sclerosis is associated with worse clinical outcomes and greater cortical pathology. Despite progress in identifying this process in multiple sclerosis patients using post-contrast fluid-attenuated inversion recovery imaging, early trials attempting to target meningeal inflammation have been unsuccessful. There is a lack of appropriate model systems to screen potential therapeutic agents targeting meningeal inflammation. We utilized ultra-high field (11.7 T) MRI to perform post-contrast imaging in SJL/J mice with experimental autoimmune encephalomyelitis induced via immunization with proteolipid protein peptide (PLP139-151) and complete Freund's adjuvant. Imaging was performed in both a cross-sectional and longitudinal fashion at time points ranging from 2 to 14 weeks post-immunization. Following imaging, we euthanized animals and collected tissue for pathological evaluation, which revealed dense cellular infiltrates corresponding to areas of contrast enhancement involving the leptomeninges. These areas of meningeal inflammation contained B cells (B220+), T cells (CD3+) and myeloid cells (Mac2+). We also noted features consistent with tertiary lymphoid tissue within these areas, namely the presence of peripheral node addressin-positive structures, C-X-C motif chemokine ligand-13 (CXCL13)-producing cells and FDC-M1+ follicular dendritic cells. In the cortex adjacent to areas of meningeal inflammation we identified astrocytosis, microgliosis, demyelination and evidence of axonal stress/damage. Since areas of meningeal contrast enhancement persisted over several weeks in longitudinal experiments, we utilized this model to test the effects of a therapeutic intervention on established meningeal inflammation. We randomized mice with evidence of meningeal contrast enhancement on MRI scans performed at 6 weeks post-immunization, to treatment with either vehicle or evobrutinib [a Bruton tyrosine kinase (BTK) inhibitor] for a period of 4 weeks. These mice underwent serial imaging; we examined the effect of treatment on the areas of meningeal contrast enhancement and noted a significant reduction in the evobrutinib group compared to vehicle (30% reduction versus 5% increase; P = 0.003). We used ultra-high field MRI to identify areas of meningeal inflammation and to track them over time in SJL/J mice with experimental autoimmune encephalomyelitis, and then used this model to identify BTK inhibition as a novel therapeutic approach to target meningeal inflammation. The results of this study provide support for future studies in multiple sclerosis patients with imaging evidence of meningeal inflammation.

Targeting B Cells to Modify MS, NMOSD, and MOGAD: Part 1

Ocrelizumab, rituximab, ofatumumab, ublituximab, inebilizumab, and evobrutinib are immunotherapies that target various B cell-related proteins. Most of these treatments have proven efficacy in relapsing and progressive forms of MS and neuromyelitis optica spectrum disease (NMOSD), or are in advanced stages of clinical development. Currently, ocrelizumab, ofatumumab, and inebilizumab are licensed for treatment of MS and NMOSD, respectively. This review focuses on the current state of knowledge about the role of B lymphocytes in immune-mediated pathophysiology and its implications for the mode of action. To understand the significance of this breakthrough in the context of the current MS therapeutic armamentarium, this review more closely examines the clinical development of CD20 depletion and the pioneering contribution of rituximab. Phase 3 and the recently published postmarketing studies will be highlighted to better understand the relevant efficacy data and safety aspects of long-term B-cell depletion.

[Ocrelizumab for treatment of multiple sclerosis]

Ocrelizumab ist ein monoklonaler Antikörper, der sich gegen das Differenzierungsantigen CD20 richtet und zu einer effektiven längerfristigen Depletion von Lymphozyten, insbesondere von B‑Zellen, führt. Unlängst publizierte Phase-3-Studien belegen, dass Ocrelizumab sowohl bei der Behandlung der schubförmigen als auch der primär progressiven Multiplen Sklerose (MS) wirksam ist. Darauf basierend wurde Ocrelizumab als erstes Medikament zur Behandlung der primär chronisch-progredienten MS zugelassen. Um diesen Durchbruch besser in den Kontext des heutigen MS-Therapiekanons einordnen zu können, lohnt sowohl ein Blick zurück auf die Entwicklung der antikörpervermittelten CD20-Depletion als auch auf die der Zulassung zugrunde liegenden Studien sowie deren Extensionsphasen. Diese Übersichtsarbeit diskutiert die verfügbaren Daten zur Wirksamkeit und Sicherheit der langfristigen B‑Zell-Depletion bei MS-Patienten und erörtert den aktuellen Kenntnisstand zur Rolle von B‑Lymphozyten in der Immunpathogenese der MS.

Immunological consequences of "immune reconstitution therapy" in multiple sclerosis: A systematic review

Immune reconstitution therapy (IRT) is an emerging concept for the treatment of multiple sclerosis (MS) that is given intermittently and can induce long-term remission of MS that is sustained in treatment-free periods. A systematic literature review was performed to identify and summarize current knowledge regarding the short- and long-term immunological consequences of different IRTs and CD20 depleting therapies on the cellular level in patients with MS. A total of 586 articles published between January 2010 and September 2019 were identified and screened; 44 studies met inclusion criteria for the review. All the treatments considered appeared to produce both qualitative and quantitative changes in the immune cell populations of patients with MS that resulted in a more anti-inflammatory immune profile. Autologous hematopoietic stem cell transplantation produced the longest-lasting and greatest effects on a wide range of immune cells. Many patients achieved prolonged depletion of the adaptive immune system when alemtuzumab and cladribine tablets were administered as short courses of therapy; however, a proportion of patients required retreatment to maintain these effects. Alemtuzumab may produce greater depletion of both CD4+ and CD8+ T cells than cladribine tablets, although both treatments similarly deplete B cells. Recovery of B cells before T cell recovery and hyperpopulation of B cells after alemtuzumab may contribute to secondary autoimmunity. Cladribine tablets had a greater effect on B cells than T cells, and no hyperpopulation of B cells was observed after treatment with cladribine tablets. Ocrelizumab and rituximab require regular repeated treatment every 6 months to maintain depletion of B and T cells. Effects of the drug treatments on the innate immune system were minor compared with those on the adaptive immune system. Additional characterization of the cellular changes occurring during IRT and CD20 depletion may lead to further improvement in the understanding of the pathogenesis of MS and the future development of therapies with even longer lasting effects. Although the treatments considered in this review improve quality of life and outcomes for patients with MS, a cure for this debilitating disease is not yet in sight.

Rituximab in the treatment of multiple sclerosis in the Hospital District of Southwest Finland

BACKGROUND

There are already numerous B-cell depleting monoclonal anti-CD20 antibodies which have been used to reduce the inflammatory burden associated with multiple sclerosis (MS). We describe here our experience of treating MS-patients with B-cell depleting rituximab.

PATIENTS AND METHODS

All MS-patients (n = 72) who had received rituximab treatment for at least six months by January 2019 were identified from the patient charts at the Turku University Hospital. Information about MS disease subtype, disease severity, MR-imaging outcomes and B-cell counts were collected from the charts.

RESULTS

Rituximab was well received and well tolerated by the patients. There were no serious infusion-related side effects. The most serious adverse event that led to treatment discontinuation was neutropenia. After rituximab initiation the annual number of relapses was decreased in the relapsing remitting and secondary progressive MS groups and the mean number of gadolinium-enhancing lesions was decreased in relapsing remitting MS. Our study confirms the usability of rituximab treatment for MS in the Finnish health care environment.

CONCLUSIONS

Off-label rituximab-treatment can be successfully used to reduce MS disease burden for the benefit of MS patients.

Progressive multiple sclerosis: from pathophysiology to therapeutic strategies

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system that involves demyelination and axonal degeneration. Although substantial progress has been made in drug development for relapsing-remitting MS, treatment of the progressive forms of the disease, which are characterized clinically by the accumulation of disability in the absence of relapses, remains unsatisfactory. This unmet clinical need is related to the complexity of the pathophysiological mechanisms involved in MS progression. Chronic inflammation, which occurs behind a closed blood-brain barrier with activation of microglia and continued involvement of T cells and B cells, is a hallmark pathophysiological feature. Inflammation can enhance mitochondrial damage in neurons, which, consequently, develop an energy deficit, further reducing axonal health. The growth-inhibitory and inflammatory environment of lesions also impairs remyelination, a repair process that might protect axons from degeneration. Moreover, neurodegeneration is accelerated by the altered expression of ion channels on denuded axons. In this Review, we discuss the current understanding of these disease mechanisms and highlight emerging therapeutic strategies based on these insights, including those targeting the neuroinflammatory and degenerative aspects as well as remyelination-promoting approaches.

Rituximab treatment for multiple sclerosis

Rituximab, a chimeric anti-CD20-antibody, attracts increasing attention as a treatment option for multiple sclerosis (MS). Apart from smaller controlled trials, an increasing number of studies in real-world populations indicate high efficacy based on clinical and neuroradiological outcomes for rituximab in relapsing-remitting MS patients. Additional evidence also demonstrates efficacy of rituximab with treatment of progressive MS phenotypes. In this topical review, we summarize and discuss current evidence on mechanisms of action, efficacy, safety, tolerance and other clinical aspects of rituximab in the treatment of MS. Finally, we will highlight current knowledge gaps and the need for comparative studies with other disease-modifying therapies in MS.

Inflammatory activity and vitamin D levels in an MS population treated with rituximab

Background

Most multiple sclerosis patients on disease-modifying treatment at Umeå University Hospital are treated with rituximab and the prevalence of vitamin D supplementation has increased over time. Follow-up studies of these off-label treatments are needed.

Objective

To study inflammatory activity and adverse effects in rituximab-treated multiple sclerosis patients, and associations with 25-hydroxy-vitamin D levels.

Methods

Retrospectively collected data on repeated estimates of relapses, disability, side effects, magnetic resonance imaging, laboratory measures including 25-hydroxy-vitamin D levels and self-perceived health.

Results

In 272 multiple sclerosis patients with a mean follow-up of 43 months, we identified seven possible relapses during active rituximab treatment. On magnetic resonance imaging examination, new T2 lesions were seen in 1.3% (10 out of 792 scans), and 0.25% (two out of 785 scans) showed contrast enhancement. Adjusted 25-hydroxy-vitamin D levels in samples drawn close to all magnetic resonance images with new T2 lesions were lower compared to the remainder (62 vs. 81 nmol/l; P = 0.030). Levels of 25-hydroxy-vitamin D were associated with self-perceived health (r = 0.18, P = 0.041, n = 130) and C-reactive protein (r = -0.13, P = 0.042) but not with the risk of side effects.

Conclusion

The inflammatory activity in this rituximab-treated multiple sclerosis population that increasingly used vitamin D supplementation was extremely low. Higher 25-hydroxy-vitamin D levels were associated with beneficial outcomes.

B-Cell Therapies in Multiple Sclerosis

B cells play a vital function in multiple sclerosis (MS) pathogenesis through an array of effector functions. All currently approved MS disease-modifying therapies alter the frequency, phenotype, or homing of B cells in one way or another. The importance of this mechanism of action has been reinforced with the successful development and clinical testing of B-cell-depleting monoclonal antibodies that target the CD20 surface antigen. Ocrelizumab, a humanized anti-CD20 monoclonal antibody, was approved by the Food and Drug Administration (FDA) in March 2017 after pivotal trials showed dramatic reductions in inflammatory disease activity in relapsing MS as well as lessening of disability progression in primary progressive MS. These and other clinical studies place B cells at the center of the inflammatory cascade in MS and provide a launching point for development of therapies that target selective pathogenic B-cell populations.

The chronically inflamed central nervous system provides niches for long-lived plasma cells

Although oligoclonal bands in the cerebrospinal fluid have been a hallmark of multiple sclerosis diagnosis for over three decades, the role of antibody-secreting cells in multiple sclerosis remains unclear. T and B cells are critical for multiple sclerosis pathogenesis, but increasing evidence suggests that plasma cells also contribute, through secretion of autoantibodies. Long-lived plasma cells are known to drive various chronic inflammatory conditions as e.g. systemic lupus erythematosus, however, to what extent they are present in autoimmune central nervous system inflammation has not yet been investigated. In brain biopsies from multiple sclerosis patients and other neurological diseases, we could detect non-proliferating plasma cells (CD138⁺Ki67⁻) in the parenchyma. Based on this finding, we hypothesized that long-lived plasma cells can persist in the central nervous system (CNS). In order to test this hypothesis, we adapted the multiple sclerosis mouse model experimental autoimmune encephalomyelitis to generate a B cell memory response. Plasma cells were found in the meninges and the parenchyma of the inflamed spinal cord, surrounded by tissue areas resembling survival niches for these cells, characterized by an up-regulation of chemokines (CXCL12), adhesion molecules (VCAM-1) and survival factors (APRIL and BAFF). In order to determine the lifetime of plasma cells in the chronically inflamed CNS, we labeled the DNA of proliferating cells with 5-ethynyl-2′-deoxyuridine (EdU). Up to five weeks later, we could detect EdU⁺ long-lived plasma cells in the murine CNS. To our knowledge, this is the first study describing non-proliferating plasma cells directly in the target tissue of a chronic inflammation in humans, as well as the first evidence demonstrating the ability of plasma cells to persist in the CNS, and the ability of the chronically inflamed CNS tissue to promote this persistence. Hence, our results suggest that the CNS provides survival niches for long-lived plasma cells, similar to the niches found in other organs. Targeting these cells in the CNS offers new perspectives for treatment of chronic autoimmune neuroinflammatory diseases, especially in patients who do not respond to conventional therapies.

Deciphering the Role of B Cells in Multiple Sclerosis-Towards Specific Targeting of Pathogenic Function

B cells, plasma cells and antibodies may play a key role in the pathogenesis of multiple sclerosis (MS). This notion is supported by various immunological changes observed in MS patients, such as activation and pro-inflammatory differentiation of peripheral blood B cells, the persistence of clonally expanded plasma cells producing immunoglobulins in the cerebrospinal fluid, as well as the composition of inflammatory central nervous system lesions frequently containing co-localizing antibody depositions and activated complement. In recent years, the perception of a respective pathophysiological B cell involvement was vividly promoted by the empirical success of anti-CD20-mediated B cell depletion in clinical trials; based on these findings, the first monoclonal anti-CD20 antibody—ocrelizumab—is currently in the process of being approved for treatment of MS. In this review, we summarize the current knowledge on the role of B cells, plasma cells and antibodies in MS and elucidate how approved and future treatments, first and foremost anti-CD20 antibodies, therapeutically modify these B cell components. We will furthermore describe regulatory functions of B cells in MS and discuss how the evolving knowledge of these therapeutically desirable B cell properties can be harnessed to improve future safety and efficacy of B cell-directed therapy in MS.

Targeting B cells in relapsing-remitting multiple sclerosis: from pathophysiology to optimal clinical management

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease that is caused by an autoimmune response against central nervous system (CNS) structures. Traditionally considered a T-cell-mediated disorder, the contribution of B cells to the pathogenesis of MS has long been debated. Based on recent promising clinical results from CD20-depleting strategies by three therapeutic monoclonal antibodies in clinical phase II and III trials (rituximab, ocrelizumab and ofatumumab), targeting B cells in MS is currently attracting growing interest among basic researchers and clinicians. Many questions about the role of B and plasma cells in MS remain still unanswered, ranging from the role of specific B-cell subsets and functions to the optimal treatment regimen of B-cell depletion and monitoring thereafter. Here, we will assess our current knowledge of the mechanisms implicating B cells in multiple steps of disease pathology and examine current and future therapeutic approaches for the treatment of MS.

CD20 therapies in multiple sclerosis and experimental autoimmune encephalomyelitis - Targeting T or B cells?

MS is widely considered to be a T cell-mediated disease although T cell immunotherapy has consistently failed, demonstrating distinct differences with experimental autoimmune encephalomyelitis (EAE), an animal model of MS in which T cell therapies are effective. Accumulating evidence has highlighted that B cells also play key role in MS pathogenesis. The high frequency of oligoclonal antibodies in the CSF, the localization of immunoglobulin in brain lesions and pathogenicity of antibodies originally pointed to the pathogenic role of B cells as autoantibody producing plasma cells. However, emerging evidence reveal that B cells also act as antigen presenting cells, T cell activators and cytokine producers suggesting that the strong efficacy of anti-CD20 antibody therapy observed in people with MS may reduce disease progression by several different mechanisms. Here we review the evidence and mechanisms by which B cells contribute to disease in MS compared to findings in the EAE model.

Insufficient disease inhibition by intrathecal rituximab in progressive multiple sclerosis

Objective

Inaccessibility of the inflammation compartmentalized to the central nervous system (CNS) may underlie the lack of efficacy of immunomodulatory treatments in progressive multiple sclerosis (MS). The double blind combination of Rituximab by IntraVenous and IntraThecAl injection versus placebo in patients with Low‐Inflammatory SEcondary progressive MS (RIVITALISE; NCT01212094) trial was designed to answer: (1) Whether an induction dose of intravenous and intrathecal rituximab efficiently depletes CNS B cells? and (2) If so, whether this leads to global inhibition of CNS inflammation and slowing of CNS tissue destruction?

Methods

Patients aged 18–65 years were randomly assigned to rituximab or placebo. Protocol‐stipulated interim analysis quantified the efficacy of B‐cell depletion.

Results

The efficacy on cerebrospinal fluid (CSF) biomarkers failed to reach criteria for continuation of the trial. B‐cell‐related CSF biomarkers (sCD21 and B‐cell activating factor) changed only in the active‐treatment arm. While CSF B cells were killed robustly (median −79.71%, P = 0.0176), B cells in CNS tissue were depleted inadequately (~−10–20%, P < 0.0001). Consequently, the T‐cell‐specific CSF biomarker sCD27 decreased slightly (−10.97%, P = 0.0005), while axonal damage marker, neurofilament light chain did not change. Insufficient saturation of CD20, lack of lytic complement, and paucity of cytotoxic CD56^dimNK cells contribute to decreased efficacy of rituximab in the CNS.

Interpretation

Biomarker studies reliably quantified complementary pharmacodynamic effects of rituximab in the CNS, exposed causes for poor efficacy and determined that RIVITALISE trial would be underpowered to measure efficacy on clinical outcomes. Identified mechanisms for poor efficacy are applicable to all CNS‐inflammation targeting monoclonal antibodies.

The potential role for ocrelizumab in the treatment of multiple sclerosis: current evidence and future prospects

B cells play a central role in the pathogenesis in multiple sclerosis (MS), being involved in the activation of proinflammatory T cells, secretion of proinflammatory cytokines, and production of autoantibodies directed against myelin. Hence, the usage of B-cell-depleting monoclonal antibodies as therapy for autoimmune diseases including MS lay near at hand. Rituximab was the first therapeutic B-cell-depleting chimeric monoclonal antibody to be used successfully in MS. Ocrelizumab, a second-generation humanized anti-CD20 antibody, was explored in a large phase II, randomized, placebo-controlled multicentre trial in patients with relapsing-remitting disease. Compared with placebo, two doses of ocrelizumab (600 and 2000 mg on days 1 and 15) showed a pronounced effect on disease activity seen in magnetic resonance imaging (MRI) as gadolinium-enhanced lesions (89% and 96% relative reduction, both p < 0.001) and also had a significant effect on relapses. In exploratory analyses, both doses of ocrelizumab had better effect on gadolinium-enhanced lesions than interferon beta-1a intramuscularly that was used as a reference arm. Adverse effects were mainly infusion-related reactions, in particular during the first infusion. Serious infections occurred at similar rates in ocrelizumab and placebo-treated patients, and no opportunistic infections were reported. However, progressive multifocal leukoencephalopathy (PML) has been reported in patients treated with anti-CD20 monoclonal antibodies for other indications. Other anti-CD20 monoclonal antibodies have been tested as treatments for MS, including ofatumumab that has shown beneficial results in placebo-controlled phase II trials in patients with relapsing-remitting MS. Ocrelizumab is now in phase III development for the treatment of relapsing-remitting MS, as well as primary progressive MS, and the results of ongoing clinical trials are eagerly awaited and will determine the place of ocrelizumab in the armamentarium of MS therapies.

The effects of intrathecal rituximab on biomarkers in multiple sclerosis

OBJECTIVES

Clinical trials of IV-rituximab have proved successful. It is unclear whether intrathecal (IT)-rituximab is more efficacious at lower doses. We examine its effects on B-cell biomarkers.

METHODS

MS patients received IT-rituximab at 3 time-points. CSF and serum samples were obtained at up to 5 time-points (days 0, 7, 14, 56 and 112). Serum and CSF BAFF and CXCL13, and CSF kappa and lambda free light chains (FLC) were measured. Flow cytometry was performed, examining effects on lymphocytes, CD3-19+ and CD3-20+ cells.

RESULTS

CSF BAFF fell following rituximab (p=0.0091 absolute values, p=0.0284 change from baseline) whilst serum BAFF increased across time-points 1-4 (p=0.0005 absolute values, p=0.0017 change from baseline). There were significant reductions in CD20+ and CD19+ cells in blood from baseline (p<0.0001) but not in CSF. CSF kappa FLC levels significantly increased (p=0.0480).

CONCLUSIONS

BAFF levels fall in CSF but increase in serum following IT-rituximab. Rituximab appears to act peripherally with dramatic decreases in peripheral CD20+ and CD19+ cells. It is likely that CSF B-cell counts were too low to enable differences to be seen. The rapid reduction in B-cells suggests rituximab has immediate effects. The profound depletion of B-cells, despite low doses of rituximab, underlines rituximab's efficacy.

Anti-B-Cell Therapies in Autoimmune Neurological Diseases: Rationale and Efficacy Trials

B cells have an ever-increasing role in the etiopathology of a number of autoimmune neurological disorders, acting as antibody-producing cells and, most importantly, as sensors, coordinators, and regulators of the immune response. B cells, among other functions, regulate the T-cell activation process through their participation in antigen presentation and production of cytokines. The availability of monoclonal antibodies or fusion proteins against B-cell surface molecules or B-cell trophic factors bestows a rational approach for treating autoimmune neurological disorders, even when T cells are the main effector cells. This review summarizes basic aspects of B-cell biology, discusses the role(s) of B cells in neurological autoimmunity, and presents anti-B-cell drugs that are either currently on the market or are expected to be available in the near future for treating neurological autoimmune disorders.

The Ins and Outs of B Cells in Multiple Sclerosis

B cells play a central role in multiple sclerosis (MS) pathology. B and plasma cells may contribute to disease activity through multiple mechanisms: antigen presentation, cytokine secretion, or antibody production. Molecular analyses of B cell populations in MS patients have revealed significant overlaps between peripheral lymphoid and clonally expanded central nervous system (CNS) B cell populations, indicating that B cell trafficking may play a critical role in driving MS exacerbations. In this review, we will assess our current knowledge of the mechanisms and pathways governing B cell migration into the CNS and examine evidence for and against a compartmentalized B cell response driving progressive MS pathology.