Epitope interactions of monoclonal antibodies targeting CD20 and their relationship to functional properties

Ocrelizumab for the Treatment of Multiple Sclerosis: Safety, Efficacy, and Pharmacology

The success of selective B-cells depleting therapies, as the anti-CD20 antibodies, in patients with multiple sclerosis (MS) has confirmed that B-cells are critical in the immune pathogenesis of the disease. Ocrelizumab, a humanized monoclonal antibody that selectively targets CD20+ B-cells, profoundly suppresses acute inflammatory disease activity, representing a highly effective therapy for relapsing-remitting multiple sclerosis (RRMS). It is also the first proven therapy able to slow disability progression in primary progressive multiple sclerosis (PPMS), particularly in patients with signs of acute radiological activity before being enrolled. Effectiveness has widely been demonstrated in randomized clinical trials (RCTs), and recently confirmed in open-label extension trials. Here, we review the role of B-cells in MS, the mechanism of action of ocrelizumab, its pharmacokinetics and pharmacodynamics, and the clinical data supporting its use, as well as safety data. We focus on issues related to the maintenance of immunocompetence, essential to ensure an immune response to either a primary infection or a vaccination. Lastly, we discuss about the possible role of ocrelizumab as an exit strategy from natalizumab-treated patients at risk of developing multifocal progressive leukoencephalopathy. In view of using ocrelizumab chronically, collecting long-term safety data and finding strategies to minimize adverse events will be extremely relevant.

Ectopic lymphoid follicles in progressive multiple sclerosis: From patients to animal models

Ectopic lymphoid follicles (ELFs), resembling germinal centre‐like structures, emerge in a variety of infectious and autoimmune and neoplastic diseases. ELFs can be found in the meninges of around 40% of the investigated progressive multiple sclerosis (MS) post‐mortem brain tissues and are associated with the severity of cortical degeneration and clinical disease progression. Of predominant importance for progressive neuronal damage during the progressive MS phase appears to be meningeal inflammation, comprising diffuse meningeal infiltrates, B‐cell aggregates and compartmentalized ELFs. However, the absence of a uniform definition of ELFs impedes reproducible and comparable neuropathological research in this field. In this review article, we will first highlight historical aspects and milestones around the discovery of ELFs in the meninges of progressive MS patients. In the next step, we discuss how animal models may contribute to an understanding of the mechanisms underlying ELF formation. Finally, we summarize challenges in investigating ELFs and propose potential directions for future research.

B-cell depletion therapy for multiple sclerosis

Since the initial observation of increased immunoglobulin concentrations in the cerebrospinal fluid of multiple sclerosis (MS) patients in the 1940s, B cells have been considered to participate in the pathology of MS through the production of autoantibodies reactive against central nervous system antigens. However, it is now recognized that B cells contribute to MS relapses via antibody-independent activities, including the presentation of antigens to T cells and the release of pro-inflammatory cytokines. In addition, the recent identification of B cell-rich follicle-like structures in the meninges of progressive MS patients suggests that the pathogenic roles of B cells also exist at the progressive phase of this disease. Recently, large-scale clinical trials have demonstrated the efficacy of B-cell depletion therapy using anti-CD20 antibodies in relapsing as well as primary progressive MS. B-cell depletion therapy has become an essential treatment option for MS based on its unique benefit to risk balance in relapsing MS, and because it is the only drug that has been shown to be effective in primary progressive MS to date.

Rituximab in Multiple Sclerosis: Are We Ready for Regulatory Approval?

Despite the availability of a lot of effective disease-modifying drugs, multiple sclerosis (MS) (in particular the progressive forms) still represents an important unmet medical need, because of issues in terms of effectiveness, duration of response, safety, and patient compliance. An increasing body of evidence from randomized clinical trials and real-world data suggest that rituximab is a highly effective alternative in both relapsing and progressive MS, with a low discontinuation rate, related to a good benefit/risk profile, and a good compliance. To date, the use of rituximab in patients with multiple sclerosis is not in accordance with the authorized product information (off-label use). However, the use of this medicine is widespread in several countries, and in some cases, it is the most commonly used disease-modifying drug for MS subtypes. This use could be officially recognized by national regulatory authorities, according to specific procedures, to ensure equal access for patients to a safe and effective option.

Bivalent binding on cells varies between anti-CD20 antibodies and is dose-dependent

Based on their mechanism of action, two types of anti-CD20 antibodies are distinguished: Type I, which efficiently mediate complement-dependent cytotoxicity, and Type II, which instead are more efficient in inducing direct cell death. Several molecular characteristics of these antibodies have been suggested to underlie these different biological functions, one of these being the manner of binding to CD20 expressed on malignant B cells. However, the exact binding model on cells is unclear. In this study, the binding mechanism of the Type I therapeutic antibodies rituximab (RTX) and ofatumumab (OFA) and the Type II antibody obinutuzumab (OBI) were established by real-time interaction analysis on live cells. It was found that the degree of bivalent stabilization differed for the antibodies: OFA was stabilized the most, followed by RTX and then OBI, which had the least amount of bivalent stabilization. Bivalency inversely correlated with binding dynamics for the antibodies, with OBI displaying the most dynamic binding pattern, followed by RTX and OFA. For RTX and OBI, bivalency and binding dynamics were concentration dependent; at higher concentrations the interactions were more dynamic, whereas the percentage of antibodies that bound bivalent was less, resulting in concentration-dependent apparent affinities. This was barely noticeable for OFA, as almost all molecules bound bivalently at the tested concentrations. We conclude that the degree of bivalent binding positively correlates with the complement recruiting capacity of the investigated CD20 antibodies.

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.

A Milestone in Multiple Sclerosis Therapy: Monoclonal Antibodies Against CD20-Yet Progress Continues

Multiple sclerosis (MS), which is a chronic inflammatory disease of the central nervous system, still represents one of the most common causes of persisting disability with an early disease onset. Growing evidence suggests B cells to play a crucial role in its pathogenesis and progression. Over the last decades, monoclonal antibodies (mabs) against the surface protein CD20 have been intensively studied as a B cell targeting therapy in relapsing MS (RMS) as well as primary progressive MS (PPMS). Pivotal studies on anti-CD20 therapy in RMS showed remarkable clinical and radiological effects, especially on acute inflammation and relapse biology. These results paved the way for further research on the implication of B cells in the pathogenesis of MS. Besides controlling relapse development in RMS, ocrelizumab (OCR) also showed clinical benefits in patients with PPMS and became the first approved drug for this disease course. In this review, we provide an overview of the current anti-CD20 mabs used or tested for the treatment of MS-namely rituximab (RTX), OCR, ofatumumab (OFA), and ublituximab (UB). Besides their effectiveness, we also discuss possible limitations and safety concerns especially in regard to long-term treatment, both for this class of drugs overall as well as for each anti-CD20 mab individually. Additionally, we elucidate to what extent anti-CD20 therapy may alter the function of other immune cells, both directly or indirectly. Finally, we cover the current knowledge on repopulation of CD20+ cells after cessation of anti-CD20 treatment and discuss future aspirations towards alternative, further developed B cell silencing therapies.

Immunosuppressive drugs modes of action

The innate and adaptive immune systems work as a complex interplay between different cell types, involving cytokines and chemokines mediating extracellular and paracrine effects. At the intracellular level, the inflammatory cascade is mediated by multifaceted processes that have been better described in the last 10 years. Immunosuppressive agents available in clinical practice act at different points of those cascades at the intracellular or extracellular level. Those drugs can mediate their effects on one or more cell types finally limiting inflammation and immune responses to antigens. Every immunosuppressive agent is characterized by intrinsic toxicity and side effects that may be due to the same therapeutic pathways or to off-target secondary effect of each molecule. We will here review the mechanisms of action of the most widely used immunosuppressive agents in the field of solid organ transplantation and autoimmune disorders, describing the mechanisms underlying both the therapeutic and secondary effects.

De-escalation of anti-CD20 monoclonal antibody (Rituximab) protocols in Pemphigus Vulgaris - a systematic review

Introduction: This review assesses current evidence supporting dose de-escalated rituximab therapy in pemphigus vulgaris, compared to standard protocols. Primary outcome measures were remission and relapse rates. Adverse effects, cumulative steroid dosages, and serological markers of disease activity were also reported.Areas covered: A literature search was performed to look for reports describing the use of de-escalated rituximab therapy in pemphigus vulgaris. Results from heterogenous studies showed a large variation in remission and relapse rates. Complete remission rates from de-escalated treatment ranged from 41.7 to 100.0%, while rates in the control groups ranged from 60.0 to 90.9%. Relapse rates varied from 8.0 to 81.3% in the de-escalated group and from 0.0 to 72.4% in the control group. Of the 165 patients included in this report, only two major adverse effects were reported.Expert Opinion: Overall, dose de-escalated rituximab protocols reported to date appear effective and safe. However, it is unclear if treatment effect parallels that of standard regimens in regard to disease control in the long term. A lower limit of effective dosing for rituximab in pemphigus vulgaris has not yet been reached or defined. The role for and timing of repeated cycles of low-dose rituximab therapy require further exploration.

The Role of B Cells in Primary Progressive Multiple Sclerosis

The success of ocrelizumab in reducing confirmed disability accumulation in primary progressive multiple sclerosis (PPMS) via CD20-targeted depletion implicates B cells as causal agents in the pathogenesis of PPMS. This review explores the possible mechanisms by which B cells contribute to disease progression in PPMS, specifically exploring cytokine production, antigen presentation, and antibody synthesis. B cells may contribute to disease progression in PPMS through cytokine production, specifically GM-CSF and IL-6, which can drive naïve T-cell differentiation into pro-inflammatory Th1/Th17 cells. B cell production of the cytokine LT-α may induce follicular dendritic cell production of CXCL13 and lead indirectly to T and B cell infiltration into the CNS. In contrast, production of IL-10 by B cells likely induces an anti-inflammatory effect that may play a role in reducing neuroinflammation in PPMS. Therefore, reduced production of IL-10 may contribute to disease worsening. B cells are also capable of potent antigen presentation and may induce pro-inflammatory T-cell differentiation via cognate interactions. B cells may also contribute to disease activity via antibody synthesis, although it's unlikely the benefit of ocrelizumab in PPMS occurs via antibody decrement. Finally, various B cell subsets likely promulgate pro- or anti-inflammatory effects in MS.

Across scales: novel insights into kidney health and disease by structural biology

Over the past decades, structural biology methods such as X-ray crystallography and cryo-electron microscopy have been increasingly used to study protein functions, molecular interactions, physiological processes, and disease mechanisms. This review outlines a selection of structural biology methods, highlights recent examples of how structural analyses have contributed to a more profound understanding of the machinery of life, and gives a perspective on how these methods can be applied to investigate functions of kidney molecules and pathogenic mechanisms of renal diseases.

Determination of the Rituximab Binding Site to the CD20 Epitope Using SPOT Synthesis and Surface Plasmon Resonance Analyses

Antibodies not only play a major role in clinical diagnostics and biopharmaceutical analysis but also are a class of drugs that are regularly used to treat numerous diseases. The identification of antibody-epitope binding sites is then of great interest to many emerging medical and bioanalytical applications, particularly to design monoclonal antibodies (mAb) mimics taking advantage of amino acid residues involved in the binding. Among relevant antibodies, the monoclonal antibody rituximab has received significant attention as it is exploited to treat several cancers including non-Hodgkin's lymphoma and chronic lymphocytic leukemia, as well as some autoimmune disorders such as rheumatoid arthritis. The binding of rituximab to the targeted cells occurs via the recognition of the CD20 epitope. A crystallographic study has shown that the binding area, named paratope, is located at the surface of rituximab. Combining the SPOT method and the complementary surface plasmon resonance technique allowed us to detect an extended recognition domain buried in the pocket of the rituximab Fab formed by four β-sheets. More generally, the present study offers a comprehensive approach to identify antibody-epitope binding sites.

Risk of requiring a wheelchair in primary progressive multiple sclerosis: Data from the ORATORIO trial and the MSBase registry

Background and purpose

Reaching Expanded Disability Status Scale (EDSS) ≥7.0 represents the requirement for a wheelchair. Here we (i) assess the effect of ocrelizumab on time to EDSS ≥7.0 over the ORATORIO (NCT01194570) double‐blind and extended controlled periods (DBP+ECP), (ii) quantify likely long‐term benefits by extrapolating results, and (iii) assess the plausibility of extrapolations using an independent real‐world cohort (MSBase registry; ACTRN12605000455662).

Methods

Post hoc analyses assessing time to 24‐week confirmed EDSS ≥7.0 in two cohorts of patients with primary progressive multiple sclerosis (baseline EDSS 3.0–6.5) were investigated in ORATORIO and MSBase.

Results

In the ORATORIO DBP+ECP, ocrelizumab reduced the risk of 24‐week confirmed EDSS ≥7.0 (hazard ratio = 0.54, 95% confidence interval [CI]: 0.31–0.92; p = 0.022). Extrapolated median time to 24‐week confirmed EDSS ≥7.0 was 12.1 and 19.2 years for placebo and ocrelizumab, respectively (7.1‐year delay [95% CI: −4.3 to 18.4]). In MSBase, the median time to 24‐week confirmed EDSS ≥7.0 was 12.4 years.

Conclusions

Compared with placebo, ocrelizumab significantly delayed time to 24‐week confirmed wheelchair requirement in ORATORIO. The plausibility of the extrapolated median time to reach this milestone in the placebo group was supported by observed real‐world data from MSBase. Extrapolated benefits for ocrelizumab over placebo could represent a truly meaningful delay in loss of ambulation and independence.

Biosimilar or Not: Physicochemical and Biological Characterization of MabThera and Its Two Biosimilar Candidates

The development of therapeutic biosimilar antibodies has become an important driving force of the modern biopharmaceutical industry. In this study, physiochemical characteristics (amino acid sequence, intact/subunit molecular weight, isoelectric point, post-translation modification, and disulfide linkage pattern), purity (charge variants, high and low molecular weight variants), antigen binding activity, Fc receptor binding affinity and Fc-effector function (CDC and ADCC) were analyzed by using an extensive set of state-of-the-art and orthogonal analytical technologies to provide a comprehensive characterization of the innovative product rituximab and two biosimilar candidates. The similarity study showed that biosimilar candidate 1 (BC1) and the reference product (RP) MabThera had an identical protein amino acid sequences and highly similar primary structures along with similar purity, heterogeneity profiles, antigen binding activity, Fc receptor binding affinity, and Fc-effector functions. Biosimilar candidate 2 (BC2), which had an amino acid replacement at a constant region, a different N-glycosylation profiling, and purity, was not analytically similar to RP. Although BC2 showed improvement such as an increased level of afucose, another IgG1 allotype, and similar biological activities, it was not recommended to be applied as a biosimilar compound in drug registration because the biosimilar manufacturer must first show that its primary structure was identical to that of RP. Our physicochemical characterizations and bioassay comparability study provided a deepened understanding of the structure-function relationship of quality attributes.

Insights into the role of B cells in the cortical pathology of Multiple sclerosis: evidence from animal models and patients

Multiple sclerosis (MS) is a chronic, immune-mediated disease of the central nervous system (CNS) that affects both white and gray matter. Although it has been traditionally considered as a T cell mediated disease, the role of B cell in MS pathology has become a topic of great research interest. Cortical lesions, key feature of the progressive forms of MS, are involved in cognitive impairment and worsening of the patients' outcome. These lesions present pathognomonic hallmarks, such as: absence of blood-brain barrier (BBB) disruption, limited inflammatory events, reactive microglia, neurodegeneration, demyelination and meningeal inflammation. B cells located in the meninges, either as part of diffuse inflammation or as part of follicle-like structures, are strongly associated with cortical damage. The function of CD20-expressing B cells in MS is further highlighted by the success of specific therapies using anti-CD20 antibodies. The possible roles of B cells in pathology go beyond their ability to produce antibodies, as they also present antigens to T cells, secrete cytokines (both pathogenic and protective) within the CNS to modulate T and myeloid cell functions, and are involved in meningeal inflammation. Here, we will review the contributions of B cells to the pathogenesis of meningeal inflammation and cortical lesions in MS patients as well as in preclinical animal models.

Ocrelizumab depletes T-lymphocytes more than rituximab in multiple sclerosis

BACKGROUND

We aim to directly compare changes in lymphocyte subpopulations between chimeric (rituximab) and humanised (ocrelizumab) anti-CD20 antibodies in multiple sclerosis (MS).

METHODS

In this retrospective analysis of prospectively collected data, we included 88 patients with MS, treated with rituximab (n=50) or ocrelizumab (n=38). We used flow cytometry in the peripheral blood to count total lymphocytes and lymphocytes expressing different phenotypic markers (CD4, CD8, CD19, CD20, CD4/CD8 ratio), before treatment and after 1, 3 and 6 months.

RESULTS

On linear mixed effect regression models, after 1, 3 and 6 months, patients treated with rituximab and with ocrelizumab were similar in total lymphocyte count, CD19 lymphocytes, CD20 lymphocytes and CD4/CD8 ratio. However, patients treated with ocrelizumab presented with lower CD4 T lymphocytes and CD8 T lymphocytes after 1, 3 and 6 months (all p<0.05). No between-treatment difference in EDSS progression was found.

DISCUSSION

B-cell levels in the peripheral blood were equally decreased by rituximab and ocrelizumab. On the contrary, CD4 and CD8 T lymphocyte reduction was more pronounced in ocrelizumab, when compared with rituximab, suggesting a broader immunomodulatory effect for the humanised antibody to be confirmed and correlated with clinical efficacy in the long term.

Comparison of the Efficacy and Safety of Anti-CD20 B Cells Depleting Drugs in Multiple Sclerosis

Rituximab, ocrelizumab, ofatumumab and ublituximab are disease modifying therapies (DMT) currently used in the treatment of multiple sclerosis (MS) or are in advanced stages of clinical trials. These monoclonal antibodies deplete B cells by targeting the cell surface protein CD20. This review highlights the similarities and major differences between the four agents. We summarize data from various clinical trials of each of these therapeutics and discuss their efficacy and safety. Additional considerations regarding the route of administration and cost are presented. Among the four therapeutics, only ocrelizumab is approved for primary progressive (PP) MS. Infusion/injection related reactions (IRRs) are the most common adverse events associated with all four therapeutics. In phase III trials of ocrelizumab and ofatumumab, the incidence of IRRs was lower with ofatumumab. Ofatumumab is unique among the four therapeutics due to its availability as a subcutaneous injection (SQ). Although SQ administration may be appealing for some patients it may raise concerns regarding medication compliance among physicians. Phase II trials studying ublituximab for the treatment of RMS yielded promising results. Phase III trials are currently comparing the efficacy of ublituximab to teriflunomide.

Engineering Anti-Tumor Monoclonal Antibodies and Fc Receptors to Enhance ADCC by Human NK Cells

Tumor-targeting monoclonal antibodies (mAbs) are the most widely used and characterized immunotherapy for hematologic and solid tumors. The significance of this therapy is their direct and indirect effects on tumor cells, facilitated by the antibody's antigen-binding fragment (Fab) and fragment crystallizable region (Fc region), respectively. The Fab can modulate the function of cell surface markers on tumor cells in an agonistic or antagonistic manner, whereas the Fc region can be recognized by an Fc receptor (FcR) on leukocytes through which various effector functions, including antibody-dependent cell-mediated cytotoxicity (ADCC), can be elicited. This process is a key cytolytic mechanism of natural killer (NK) cells. These innate lymphocytes in the human body recognize tumor-bound antibodies exclusively by the IgG Fc receptor CD16A (FcγRIIIA). Two allelic versions of CD16A bind IgG with either lower or higher affinity. Cancer patients homozygous for the higher affinity allele of CD16A have been reported to respond significantly better to mAb therapies for various malignancies. These studies revealed that mAb therapy efficacy positively correlates with higher affinity binding to CD16A. Approaches to enhance tumor antigen targeting by NK cells by modifying the Fc portion of antibodies or the FcR on NK cells are the focus of this review.

Clinical Perspectives on the Molecular and Pharmacological Attributes of Anti-CD20 Therapies for Multiple Sclerosis

Anti-CD20 therapies have demonstrated considerable efficacy in the treatment of relapsing multiple sclerosis, constituting a high-efficacy treatment approach for reducing relapse risk and mitigating disability progression. These therapies have been shown to strongly deplete circulating B cells and small subsets of CD3+ CD4 and CD8 T cells that express low levels of CD20. While the clinical profiles of the various anti-CD20 monoclonal antibodies used in treating multiple sclerosis are well-described in the literature, greater understanding of the implications of their distinct molecular and pharmacological attributes is needed. In this review, we focus on four anti-CD20 monoclonal antibodies-rituximab, ocrelizumab, ofatumumab, and ublituximab-that are currently used, approved, or in late-stage clinical development for the treatment of multiple sclerosis. We provide clinical perspectives on the potential implications of differences in molecular structures, target epitopes, dosing regimens, mechanisms and impact on B-cell depletion and reconstitution, immunogenicity, administration-related reactions, and infection risks.

Anti-CD20 monoclonal antibodies in Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is an autoimmune inflammatory condition with a wide spectrum of disease manifestations and severities, resulting in significant morbidity and mortality. The aetiopathogenesis of SLE is complex. Young women and certain ethnicities are commonly affected, suggesting a significant hormonal and genetic influence. Diverse immunological abnormalities have been described. A characteristic abnormality is the presence of autoantibodies, implicating a central role for B cells in disease pathogenesis and/or perpetuation. Whilst conventional therapies have improved outcomes, a great unmet need remains. Recently, biological therapies are being explored. B-cell depletion therapy with rituximab has been in use off-label for nearly two decades. Inconsistent results between uncontrolled and controlled studies have raised doubts about its efficacy. In this review, we will focus on B cell abnormalities and the rationale behind B-cell depletion therapy with anti-CD20 monoclonal antibody (mAb), rituximab, will be explored including an evaluation of clinical and trial experience. Finally, we will discuss the mechanistic basis for considering alternative anti-CD20 mAbs.

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 in relapsing and primary progressive multiple sclerosis: Pharmacokinetic and pharmacodynamic analyses of OPERA I, OPERA II and ORATORIO

Aims

Ocrelizumab is a humanized monoclonal antibody that selectively targets CD20‐positive B cells and is indicated for treatment of patients with relapsing forms of multiple sclerosis (RMS) or primary progressive multiple sclerosis (PPMS). The pharmacokinetics and pharmacodynamics of ocrelizumab in patients with RMS or PPMS were assessed.

Methods

A population pharmacokinetic model was developed based on data from the Phase II study and the Phase III studies OPERA I and OPERA II in patients with RMS. Data from the ORATORIO Phase III study in patients with PPMS became available after model finalization and was used for external model evaluation.

Results

The ocrelizumab serum concentration vs time course was accurately described by a 2‐compartment model with time‐dependent clearance. Body weight was found to be the main covariate. The area under the concentration–time curve over the dosing interval was estimated to be 26% higher for patients with RMS weighing <60 kg and 21% lower for patients weighing >90 kg when compared with the 60–90 kg group. The terminal half‐life of ocrelizumab was estimated as 26 days. The extent of B‐cell depletion in blood, as the pharmacodynamic marker, was greater with increasing ocrelizumab exposure.

Conclusion

The pharmacokinetics of ocrelizumab was described with pharmacokinetic parameters typical for an immunoglobulin G1 monoclonal antibody, with body weight as the main covariate. The pharmacokinetics and B‐cell depletion in blood were comparable across the RMS and PPMS trials, and the extent of blood B‐cell depletion was greater with higher exposure.

Novel Therapies for Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a severe chronic autoimmune blistering disease that affects the skin and mucous membranes. It is characterized by suprabasal acantholysis due to disruption of desmosomal connections between keratinocytes. Autoantibodies against desmosomal cadherins, desmoglein 3 and 1, have been shown to induce disease. Certain human leukocyte antigen (HLA) types and non-HLA foci confer genetic susceptibility. Until the discovery of corticosteroids in the 1950s, PV was 75% fatal. Since then, multiple PV treatments, such as systemic corticosteroids and adjunctive therapy with immunosuppressive medications (mycophenolate mofetil, azathioprine, cyclophosphamide, cyclosporine, methotrexate, gold, and others) have been introduced; however, none have led to long-term remissions and many have undesired adverse effects. Our growing understanding of the pathophysiologic mechanisms in PV is leading to development of new targeted therapies, such as intravenous immunoglobulin, anti-CD20 monoclonal antibodies, inhibitors of Bruton tyrosine kinase and neonatal Fc receptors, and adoptive cellular transfer, that may result in lasting control of this life-threatening disease.

Second-generation immunotherapeutics in multiple sclerosis: can we discard their precursors?

Options for disease-modifying therapies in multiple sclerosis have increased over the past two decades. Among these innovations are interferon-β, glatiramer acetate, fumaric acid and dihydroorotate dehydrogenase inhibitors, an antibody targeting the migration of immune cells, a compound that traps immune cells in lymphoid organs by sphingosine 1-phosphate receptor (S1PR) modulation and immune-reconstitution therapies. Second-generation drugs such as pegylated interferon-β, advanced CD20 depleting antibodies, more-specific S1PR modulators and new formulations have been developed to achieve higher efficacy while exhibiting fewer side effects. In this review, we address the shortcomings of the parent drugs, present the pros and cons of the second-generation therapies and summarize upcoming developments in the field of immunotherapy for multiple sclerosis.

Effects of CD20 antibodies and kinase inhibitors on B-cell receptor signalling and survival of chronic lymphocytic leukaemia cells

Recently, clinical trial results have established inhibitors of B-cell receptor (BCR)-associated kinase (BAKi), with or without CD20 moniclonal antibodies (mAbs), as the preferred first-line treatment for most chronic lymphocytic leukaemia (CLL) patients. Using phosphospecific flow cytometry, we showed that in leukaemic cells from CLL patients the CD20 therapeutic antibodies - rituximab, ofatumumab, and obinutuzumab - inhibited BCR signalling pathways targeting preferentially pBTK^Y551 - but not BTK^Y223 - and pAKT. On the contrary, ibrutinib and idelalisib reduced pBTK^Y223 to a higher extent than pBTK^Y551 . The strong reduction of pAKT induced by idelalisib was enhanced by its combination with rituximab or ofatumumab. Moreover, CD20 mAbs and BAKi induced the death of leukaemia cells that was significantly potentiated by their combination. Analysis of the enhancement of cell death in these combinations revealed an approximately additive enhancement induced by rituximab or obinutuzumab combined with ibrutinib or idelalisib. Taken together, our data identified negative regulatory effects of CD20 mAbs and their combinations with BAKi on BCR signalling and cell survival in CLL. In conclusion, this study advances our understanding of mechanisms of action of CD20 mAbs as single agents or in combination with BAKi and could inform on the potential of combined therapies in ongoing and future clinical trials in patients with CLL.

Fc-Engineering for Modulated Effector Functions-Improving Antibodies for Cancer Treatment

The majority of monoclonal antibody (mAb) therapeutics possess the ability to engage innate immune effectors through interactions mediated by their fragment crystallizable (Fc) domain. By delivering Fc-Fc gamma receptor (FcγR) and Fc-C1q interactions, mAb are able to link exquisite specificity to powerful cellular and complement-mediated effector functions. Fc interactions can also facilitate enhanced target clustering to evoke potent receptor signaling. These observations have driven decades-long research to delineate the properties within the Fc that elicit these various activities, identifying key amino acid residues and elucidating the important role of glycosylation. They have also fostered a growing interest in Fc-engineering whereby this knowledge is exploited to modulate Fc effector function to suit specific mechanisms of action and therapeutic purposes. In this review, we document the insight that has been generated through the study of the Fc domain; revealing the underpinning structure-function relationships and how the Fc has been engineered to produce an increasing number of antibodies that are appearing in the clinic with augmented abilities to treat cancer.

Anti-CD20 treatment for B-cell malignancies: current status and future directions

INTRODUCTION

The introduction of anti-CD20 monoclonal antibody therapy with rituximab in the 1990s greatly improved outcomes for patients with B-cell malignancies. Disease resistance or relapse after successful initial therapy and declining efficacy of subsequent rounds of treatment were the basis for the development of alternative anti-CD20-based antibody therapies.

AREAS COVERED

The novel anti-CD20 antibodies of atumumab, ublituximab, and obinutuzumab were developed to be differentiated via structural and mechanistic features over rituximab. We provide an overview of preclinical and clinical data, and demonstrate ways in which the pharmacodynamic properties of these novel agents translate into clinical benefit for patients.

EXPERT OPINION

Of the novel anti-CD20 antibodies, only obinutuzumab has shown consistently improved efficacy over rituximab in randomized pivotal trials in indolent non-Hodgkin lymphoma and chronic lymphocytic leukemia. The Phase 3 GALLIUM trial demonstrated significant improvements in progression-free survival with obinutuzumab-based immunochemotherapy over rituximab-based immunochemotherapy. Novel combinations of obinutuzumab, including with chemotherapy-free options are being explored, such as with the newly approved combinations of obinutuzumab with venetoclax, ibrutinib, or acalabrutinib. The biggest unmet need remains in the treatment of diffuse large B-cell lymphoma; emerging options in this field include the use of CAR-T cells and T-cell bispecific antibodies.

Anti-CD20 Agents for Multiple Sclerosis: Spotlight on Ocrelizumab and Ofatumumab

Until recently, in the pathogenesis of Multiple Sclerosis (MS), the contribution of B cells has been largely underestimated, and the disease was considered a T-cell-mediated disorder. However, newer evidence shows that B cells play a crucial role in the pathogenesis of MS via antigen-driven autoantibody responses and through the cross regulation of T-helper cells. As B cells express the surface molecule CD20 at all points of differentiation, it provides a specific target for monoclonal antibodies, and the development and clinical testing of anti-CD20 antibody treatments for MS have been successful. After some observations, some small clinical trials found positive effects for the first anti-CD20 therapeutic rituximab in MS; newer agents have been specifically evaluated, resulting in the development of ocrelizumab and ofatumumab. Ocrelizumab, a humanized anti-CD20 monoclonal antibody, was approved in March 2017 by the Food and Drug Administration (FDA) and is also the first proven therapy to reduce disability progression in primary progressive MS. This is particularly significant considering that disease-modifying treatment options are few for both primary and secondary progressive MS. Ofatumumab, a fully human anti-CD20 monoclonal antibody, that binds a distinct epitope, has been further investigated in phase 3 trials for relapsing forms of MS. In this review, we discuss in detail these two anti-CD20 agents and their advent for treatment of MS.

A comparative study of tolerability and effects on immunoglobulin levels and CD19 cell counts with ocrelizumab vs low dose of rituximab in multiple sclerosis

Background

Rituximab (RTX) and ocrelizumab (OCR) are two anti-CD20 biologics used in MS; however, comparisons on safety and efficacy are rare.

Objective

To compare treatment outcomes over the first year with RTX and OCR.

Methods

Retrospective cohort study comprising MS patients initiating RTX at the Karolinska University Hospital (Sweden; n = 311) and OCR at Rocky Mountain MS Clinic (Utah, USA; n = 161), respectively.

Results

Levels of immunoglobulin G measured in blood dropped 0.16 g/L (95% confidence interval 0.01 to 0.31) with each OCR infusion, but remained stable with RTX. In contrast, levels of immunoglobulin M decreased to a similar extent with both drugs. Ten and 15% of patients discontinued treatment with RTX and OCR, respectively (n.s), however, adverse events leading to treatment discontinuation were more common with OCR (6.8% vs 2.6%; p = 0.026). Only 3.1 and 1.6% discontinued OCR and RTX, respectively, due to lack of effect (n.s). The degree of B cell depletion was superior with OCR.

Conclusion

Overall, differences between the two treatments were small. Although the study design precludes robust conclusions regarding the risk-benefit with the studied therapies, our findings indicate that the tolerability and safety with RTX is not inferior to OCR.

Successful treatment of PLA2R1-antibody positive membranous nephropathy with ocrelizumab

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in adults. The disease is induced by antibodies, which are directed against the podocyte protein phospholipase A₂ receptor 1 (PLA₂R1-ab) in 80% of cases. B cell depleting treatments, most notably rituximab, a chimeric CD20-antibody, are often effective for treatment of MN. However, in 35–40% of patients rituximab fails to induce remission of disease and relapses after rituximab-induced remission are frequent. Therefore, alternative treatment options are necessary. Over the past years optimized antibodies targeting CD20 were designed to overcome side effects or sensitization to the murine fractions of rituximab and potentially improve B cell depletion. Ocrelizumab is a humanized B cell depleting antibody, approved for treatment of multiple sclerosis (MS). Here, we report the case of a patient who was diagnosed with MS and, 8 years later, developed PLA₂R1-associated MN. Treatment for MS was switched to the CD20-antibody ocrelizumab, which was expected to deplete B cells and potentially induce remission of MN. After treatment with ocrelizumab PLA₂R1-ab disappeared from the circulation and the patient developed remission of proteinuria. Ocrelizumab might be an efficacious treatment alternative for patients with MN who fail to achieve remission or are immunologically sensitized to rituximab.

The Pharmacogenetics of Rituximab: Potential Implications for Anti-CD20 Therapies in Multiple Sclerosis

There are a broad range of disease-modifying therapies (DMTs) available in relapsing-remitting multiple sclerosis (RRMS), but limited biomarkers exist to personalise DMT choice. All DMTs, including monoclonal antibodies such as rituximab and ocrelizumab, are effective in preventing relapses and preserving neurological function in MS. However, each agent harbours its own risk of therapeutic failure or adverse events. Pharmacogenetics, the study of the effects of genetic variation on therapeutic response or adverse events, could improve the precision of DMT selection. Pharmacogenetic studies of rituximab in MS patients are lacking, but pharmacogenetic markers in other rituximab-treated autoimmune conditions have been identified. This review will outline the wider implications of pharmacogenetics and the mechanisms of anti-CD20 agents in MS. We explore the non-MS rituximab literature to characterise pharmacogenetic variants that could be of prognostic relevance in those receiving rituximab, ocrelizumab or other monoclonal antibodies for MS.

Analytical comparability study of anti-CD20 monoclonal antibodies rituximab and obinutuzumab using a stability-indicating orthogonal testing protocol: Effect of structural optimization and glycoengineering

Glycoengineering and biosimilarity are the key factors for growing, promising and progressive approaches in monoclonal antibodies development. In this study, the physicochemical stability of anti-CD20 rituximab (RTX); originator and biosimilar was compared to its glycoengineered humanized version; obinutuzumab (OBZ). An orthogonal stability-indicating protocol using a set of validated bioanalytical techniques; size exclusion high performance liquid chromatography (SE-HPLC), reversed phase liquid chromatography (RP-HPLC), quantitative gel electrophoresis by TapeStation, receptor binding assay and dynamic light scattering (DLS) was used to investigate the effect of different stress factors on the pattern and kinetics of degradation. SE-HPLC results supported with spectral purity showed similar degradation extent with a different pattern of degradation between RTX and OBZ. A lower tendency to form degraded fragments and a relatively higher favorability for degradation through aggregate formation has been revealed in case of OBZ. Results were in agreement with those of DLS and receptor binding assay which showed specificity to the intact antibodies in the presence of their degradation products. Furthermore, results were additionally confirmed through denaturing quantitative gel electrophoresis which suggested reducible covalent bonds as the mechanism for aggregates formation. RP-HPLC results showed two oxidized forms via excessive oxidation of RTX and OBZ with nearly the same degradation percent. Comparability data of RTX and OBZ using the applied methodologies showed that although glycoengineering; carried out to enhance the therapeutic and biological activity of OBZ altered the pattern of degradation but did not significantly affect the overall stability. Results showed also consistent stability profile between the biosimilar and its originator RTX products.

Adverse event profile differences between rituximab and ocrelizumab: Findings from the FDA Adverse Event Reporting Database

BACKGROUND

Rituximab and ocrelizumab are anti-CD20 monoclonal antibodies that have shown a marked reduction in multiple sclerosis (MS) inflammatory activity. However, their real-world safety profile has not been adequately compared.

OBJECTIVE

To investigate the adverse event (AE) profile of rituximab and ocrelizumab reported to the Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHODS

The FAERS database was filtered by indication (MS) and drug (rituximab or ocrelizumab). Disproportionality analyses including but not limited to reporting odds ratio (ROR) were conducted to identify drug-AE associations. A signal was detected if the lower limit of the 95% confidence interval of ROR (ROR₀₂₅) exceeded 1.

RESULTS

There were 623 and 7948 reports for rituximab and ocrelizumab, respectively. The most frequent AEs with rituximab and ocrelizumab were infusion-related reaction (4.82%) and urinary tract infection (10.52%), respectively. The strongest drug-AE association for rituximab and ocrelizumab were ear pruritus (ROR₀₂₅: 47.53) and oral herpes (ROR₀₂₅: 38.99), respectively. Ocrelizumab was associated with an almost two times higher frequency of infections than rituximab (21.93% vs 11.05%, respectively).

CONCLUSION

This study revealed differences in reporting AEs between rituximab and ocrelizumab. Infections were reported more frequently with ocrelizumab. Although speculative, a potentially different or more extensive B-cell depletion by ocrelizumab might explain these findings. Additional pharmacovigilance studies need to be performed to better characterize differences in the AE profile in B-cell-depleting therapies.

Affinity for the Interface Underpins Potency of Antibodies Operating In Membrane Environments

The contribution of membrane interfacial interactions to recognition of membrane-embedded antigens by antibodies is currently unclear. This report demonstrates the optimization of this type of antibodies via chemical modification of regions near the membrane but not directly involved in the recognition of the epitope. Using the HIV-1 antibody 10E8 as a model, linear and polycyclic synthetic aromatic compounds are introduced at selected sites. Molecular dynamics simulations predict the favorable interactions of these synthetic compounds with the viral lipid membrane, where the epitope of the HIV-1 glycoprotein Env is located. Chemical modification of 10E8 with aromatic acetamides facilitates the productive and specific recognition of the native antigen, partially buried in the crowded environment of the viral membrane, resulting in a dramatic increase of its capacity to block viral infection. These observations support the harnessing of interfacial affinity through site-selective chemical modification to optimize the function of antibodies that target membrane-proximal epitopes.

Binding mechanisms of therapeutic antibodies to human CD20

Monoclonal antibodies (mAbs) targeting human antigen CD20 (cluster of differentiation 20) constitute important immunotherapies for the treatment of B cell malignancies and autoimmune diseases. Type I and II therapeutic mAbs differ in B cell binding properties and cytotoxic effects, reflecting differential interaction mechanisms with CD20. Here we present 3.7- to 4.7-angstrom cryo–electron microscopy structures of full-length CD20 in complexes with prototypical type I rituximab and ofatumumab and type II obinutuzumab. The structures and binding thermodynamics demonstrate that upon binding to CD20, type II mAbs form terminal complexes that preclude recruitment of additional mAbs and complement components, whereas type I complexes act as molecular seeds to increase mAb local concentration for efficient complement activation. Among type I mAbs, ofatumumab complexes display optimal geometry for complement recruitment. The uncovered mechanisms should aid rational design of next-generation immunotherapies targeting CD20.

Five years of ocrelizumab in relapsing multiple sclerosis: OPERA studies open-label extension

OBJECTIVE

To assess over 3 years of follow-up the effects of maintaining or switching to ocrelizumab (OCR) therapy on clinical and MRI outcomes and safety measures in the open-label extension (OLE) phase of the pooled OPERA: I/II studies in relapsing multiple sclerosis.

METHODS

After 2 years of double-blind, controlled treatment, patients continued OCR (600 mg infusions every 24 weeks) or switched from interferon (IFN)-β-1a (44 μg 3 times weekly) to OCR when entering the OLE phase (3 years). Adjusted annualized relapse rate, time to onset of 24-week confirmed disability progression (CDP)/improvement (CDP), brain MRI activity (gadolinium-enhanced and new/enlarging T2 lesions), and percentage brain volume change were analyzed.

RESULTS

Of patients entering the OLE phase, 88.6% completed year 5. The cumulative proportion with 24-week CDP was lower in patients who initiated OCR earlier vs patients initially receiving IFN-β-1a (16.1% vs 21.3% at year 5; p = 0.014). Patients continuing OCR maintained and those switching from IFN-β-1a to OCR attained near complete and sustained suppression of new brain MRI lesion activity from years 3-5. Over the OLE phase, patients continuing OCR exhibited less whole brain volume loss from double-blind study baseline vs those switching from IFN-β-1a (-1.87% vs -2.15% at year 5; p < 0.01). Adverse events were consistent with past reports and no new safety signals emerged with prolonged treatment.

CONCLUSION

Compared with patients switching from IFN-β-1a, earlier and continuous OCR treatment up to 5 years provided sustained benefit on clinical and MRI measures of disease progression.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that earlier and continuous treatment with OCR provided sustained benefit on clinical and MRI outcomes of disease activity and progression compared with patients switching from IFN-β-1a. The study is rated Class III because of the initial treatment randomization disclosure that occurred after inclusion in OLE.

CLINICAL TRIAL IDENTIFIERS

NCT01247324/NCT01412333.

Highly active RRMS and ocrelizumab after failure of alemtuzumab therapy

Background

A high multiple sclerosis activity while on alemtuzumab is rather uncommon compared to moderate-efficacy drugs. The purpose of this case report is to present a case of a 37-year-old female patient with bronchial asthma and no other medical history, whose disease activity required switching from dimethyl fumarate to fingolimod, then to alemtuzumab and finally to ocrelizumab.

Case presentation

In our patient, two severe attacks were observed and treated after administration of the first pulse of alemtuzumab. After six months of therapy, patient’s immunological profile showed the expected decrease in CD4+ and CD8+ T-cells and, markedly increased values of CD19+ B-cells. Surprisingly memory B-cells, which typically repopulate very slowly following alemtuzumab treatment, were above baseline levels. Regular administration of ocrelizumab based on a standardised scheme, after the alemtuzumab therapy failure, resulted in the stabilisation of the patient’s condition both clinically and radiologically.

Conclusion

Thus, when the alemtuzumab treatment is unsuccessful, the authors recommend testing T- and B-cell levels and proceeding with an early switch to ocrelizumab if high B-cell counts are found.

Use of anti-CD20 therapy in follicular and marginal zone lymphoma: a review of the literature

The identification of the CD20 antigen in 1979 was the first step in what would become a therapeutic milestone opening the use of immunotherapy in hematological diseases. This protein is expressed on the surface of developing B cells, but not the early progenitors or mature plasma cells. In 1997, rituximab was approved by the Food and Drug Administration, and since then it has revolutionized the treatment of B-cell malignancies. It is used as a monotherapy and in combination, at induction, at relapsed, and also in maintenance. Indolent non-Hodgkin lymphomas are characterized by a long and non-aggressive course. In this group of lymphomas, rituximab represented a great therapeutic improvement, achieving lasting responses with few adverse effects. Nowadays, second-generation molecules are emerging that may have important advantages compared to rituximab, as well as biosimilars that represent an important cost-effective option.

Design of a non-interventional post-marketing study to assess the long-term safety and effectiveness of ocrelizumab in German real world multiple sclerosis cohorts - the CONFIDENCE study protocol

BACKGROUND

Multiple sclerosis (MS) is a chronic disease that requires lifelong treatment. A highly effective drug not only for relapsing but also for progressive forms of MS with a favorable safety profile is needed to further improve overall patient outcomes. Ocrelizumab, a recombinant humanized monoclonal antibody that selectively targets CD20-expressing B-cells, is the first drug indicated for the treatment of adult patients with relapsing forms of MS (RMS) and primary progressive MS (PPMS). Its safety and effectiveness profile has yet to be studied in a large, real-world setting. CONFIDENCE aims to further characterize the safety profile of ocrelizumab in routine clinical practice. In addition, real-world effectiveness data will be collected to complement the efficacy data documented in the pivotal clinical trials.

METHODS

CONFIDENCE is a non-interventional, prospective, multicenter, long-term study collecting primary data from 3000 RMS and PPMS patients newly treated with ocrelizumab and 1500 patients newly treated with other selected MS disease-modifying therapies (DMTs). Treatment must be in accordance with the local label and follow routine practice. Data will be collected at approximately 250 neurological centers and practices across Germany. The recruitment period of 30 months started in April 2018. The observation period per patient is planned 7.5 to 10 years, depending on the date of inclusion, regardless of whether patients discontinue treatment. Visits follow routine practice and will be documented approximately every 6 months. The primary endpoint is the incidence and type of uncommon adverse events and death. Statistical analyses will be mainly descriptive and exploratory.

DISCUSSION

CONFIDENCE is a large, non-interventional, post-authorization safety study that assesses long-term safety and effectiveness of ocrelizumab and other DMTs in a real-world setting. Data collected in CONFIDENCE will also be integrated into studies that have been developed to fulfil international regulatory requirements.

Anti-CD20 Monoclonal Antibodies for Relapsing and Progressive Multiple Sclerosis

Multiple sclerosis (MS) was previously thought to be a T-cell-mediated, demyelinating disease of the central nervous system. Disease-modifying therapies targeting T cells have, indeed, shown remarkable efficacy in patients with relapsing-remitting MS. However, these therapies do also target B cells, and a B-cell-depleting monoclonal antibody (ocrelizumab) has recently been approved for MS therapy and is efficacious not only in relapsing forms of MS but also in some patients with primary progressive MS. This suggests that B cells may play a more important role in the pathogenesis of MS than previously appreciated. We review the potential roles of B cells, which are the precursors of antibody-secreting plasma cells in the pathogenesis of MS. Furthermore, we provide an overview of the characteristics and clinical data for the four monoclonal antibodies (ocrelizumab, ofatumumab, rituximab, and ublituximab) that have been approved, are currently been used off-label or are being investigated as treatments for MS. These antibodies all target the cluster of differentiation (CD)-20 molecule and bind to distinct or overlapping epitopes on B cells and a subset of T cells that express CD20. This leads to B-cell depletion and, possibly, to depletion of CD20-positive T cells. The net result is strong suppression of clinical and radiological disease activity as well as slowing of the development of persisting neurological impairment.

Structure of CD20 in complex with the therapeutic monoclonal antibody rituximab

Cluster of differentiation 20 (CD20) is a B cell membrane protein that is targeted by monoclonal antibodies for the treatment of malignancies and autoimmune disorders but whose structure and function are unknown. Rituximab (RTX) has been in clinical use for two decades, but how it activates complement to kill B cells remains poorly understood. We obtained a structure of CD20 in complex with RTX, revealing CD20 as a compact double-barrel dimer bound by two RTX antigen-binding fragments (Fabs), each of which engages a composite epitope and an extensive homotypic Fab:Fab interface. Our data suggest that RTX cross-links CD20 into circular assemblies and lead to a structural model for complement recruitment. Our results further highlight the potential relevance of homotypic Fab:Fab interactions in targeting oligomeric cell-surface markers.

STIM1 knock-down decreases the affinity of obinutuzumab for CD20 by altering CD20 localization to Triton-soluble membrane

Obinutuzumab is thought to exert its effects through its high antibody-dependent cellular cytotoxicity (ADCC) via glyco-engineering of the Fc region. In addition, obinutuzumab causes direct binding-induced cell death (DCD) only by specifically binding to its target CD20, a Ca²⁺ channel. However, the specific features of CD20 related to obinutuzumab binding-induction of cell death are not clearly understood. In this study, we evaluated the relationship between the Ca²⁺ channel features of CD20 as a store-operated Ca²⁺ channel (SOC) and obinutuzumab binding-induced cell death. Ca²⁺ channel function and biochemical analysis revealed that CD20 is an Orai1- and stromal interaction molecule (STIM1)-dependent Ca²⁺ pore. However, binding of obinutuzumab on CD20 did not have any effect on Ca²⁺ influx activity of CD20; the direct cell death rate mediated by obinutuzumab binding was almost equivalent with or without the extracellular Ca²⁺ condition. Given the apparent interaction between STIM1 and CD20, we observed Triton-X solubilized obinutuzumab-bound CD20 accompanied by STIM1. Subsequently, obinutuzumab binding and cell death were decreased by STIM1 knock-down in Ramos B cells. Thus, STIM1 directly contributes to cell death by increasing the affinity of cells for obinutuzumab by transferring CD20 to the Triton-soluble membrane region.

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.

CD16 pre-ligation by defucosylated tumor-targeting mAb sensitizes human NK cells to γc cytokine stimulation via PI3K/mTOR axis

Obinutuzumab is a glycoengineered tumor-targeting anti-CD20 mAb with a modified crystallizable fragment (Fc) domain designed to increase the affinity for the FcγRIIIA/CD16 receptor, which was recently approved for clinical use in CLL and follicular lymphoma. Here we extend our previous observation that, in human NK cells, the sustained CD16 ligation by obinutuzumab-opsonized targets leads to a markedly enhanced IFN-γ production upon a subsequent cytokine re-stimulation. The increased IFN-γ competence in response to IL-2 or IL-15 is attributable to post-transcriptional regulation, as it does not correlate with the upregulation of IFN-γ mRNA levels. Different from the reference molecule rituximab, we observe that the stimulation with obinutuzumab promotes the upregulation of microRNA (miR)-155 expression. A similar trend was also observed in NK cells from untreated CLL patients stimulated with obinutuzumab-opsonized autologous leukemia. miR-155 upregulation associates with reduced levels of SHIP-1 inositol phosphatase, which acts in constraining PI3K-dependent signals, by virtue of its ability to mediate phosphatidylinositol 3,4,5-trisphosphate (PIP3) de-phosphorylation. Downstream of PI3K, the phosphorylation status of mammalian target of rapamycin (mTOR) effector molecule, S6, results in amplified response to IL-2 or IL-15 stimulation in obinutuzumab-experienced cells. Importantly, NK cell treatment with the PI3K or mTOR inhibitors, idelalisib and rapamycin, respectively, prevents the enhanced cytokine responsiveness, thus, highlighting the relevance of the PI3K/mTOR axis in CD16-dependent priming. The enhanced IFN-γ competence may be envisaged to potentiate the immunoregulatory role of NK cells in a therapeutic setting.

Considerations for the Design of Antibody-Based Therapeutics

Antibody-based proteins have become an important class of biologic therapeutics, due in large part to the stability, specificity, and adaptability of the antibody framework. Indeed, antibodies not only have the inherent ability to bind both antigens and endogenous immune receptors but also have proven extremely amenable to protein engineering. Thus, several derivatives of the monoclonal antibody format, including bispecific antibodies, antibody-drug conjugates, and antibody fragments, have demonstrated efficacy for treating human disease, particularly in the fields of immunology and oncology. Reviewed here are considerations for the design of antibody-based therapeutics, including immunological context, therapeutic mechanisms, and engineering strategies. First, characteristics of antibodies are introduced, with emphasis on structural domains, functionally important receptors, isotypic and allotypic differences, and modifications such as glycosylation. Then, aspects of therapeutic antibody design are discussed, including identification of antigen-specific variable regions, choice of expression system, use of multispecific formats, and design of antibody derivatives based on fragmentation, oligomerization, or conjugation to other functional moieties. Finally, strategies to enhance antibody function through protein engineering are reviewed while highlighting the impact of fundamental biophysical properties on protein developability.

Antibody Structure and Function: The Basis for Engineering Therapeutics

Antibodies and antibody-derived macromolecules have established themselves as the mainstay in protein-based therapeutic molecules (biologics). Our knowledge of the structure–function relationships of antibodies provides a platform for protein engineering that has been exploited to generate a wide range of biologics for a host of therapeutic indications. In this review, our basic understanding of the antibody structure is described along with how that knowledge has leveraged the engineering of antibody and antibody-related therapeutics having the appropriate antigen affinity, effector function, and biophysical properties. The platforms examined include the development of antibodies, antibody fragments, bispecific antibody, and antibody fusion products, whose efficacy and manufacturability can be improved via humanization, affinity modulation, and stability enhancement. We also review the design and selection of binding arms, and avidity modulation. Different strategies of preparing bispecific and multispecific molecules for an array of therapeutic applications are included.