Anti-CD20 monoclonal antibodies: reviewing a revolution

The Evolution of Anti-CD20 Treatment for Multiple Sclerosis: Optimization of Antibody Characteristics and Function

B-cell depletion with CD20-targeted agents is commonly used for treatment of multiple sclerosis (MS), other autoimmune diseases, and certain hematologic malignancies. Initial apparent success with rituximab in MS and neuromyelitis optica spurred development of the anti-CD20 monoclonal antibody (mAb) therapies ocrelizumab, ofatumumab, and ublituximab as well as the anti-CD19 mAb inebilizumab. While each are effective at targeting and depleting B cells, structural differences translate into different mechanisms of action affecting maintenance of B-cell depletion and safety and tolerability. Although the anti-CD20 mAbs differ in degree of human versus mouse sequences as well as target CD20 epitope, these properties do not appear to substantially affect activity or tolerability. In contrast, an antibody-dependent cell-mediated cytotoxicity (ADCC) versus a complement-dependent cytotoxicity mechanism of action as well as subcutaneous versus intravenous administration may provide improved tolerability. Glycoengineering of the mAbs ublituximab and inebilizumab enhances ADCC and can overcome the reduced responses to mAb-mediated B-cell depletion associated with certain genetic polymorphisms. Other strategies for therapeutic targeting of CD20, including brain shuttle antibodies (e.g., RO7121932), bispecific antibodies, chimeric antigen receptor T-cell therapies, and antibody-drug conjugates, are in active clinical development and may be future treatment approaches in MS and other B-cell-mediated autoimmune diseases.

Delayed but successful development of immune memory against SARS-COV-2 after B cell-depleting monotherapy

PURPOSE

Patients receiving CD20-directed therapies are known to insufficiently develop neutralizing antibody titers against SARS-COV-2 after two vaccinations. We investigated the impact of a third and fourth vaccination, possibly deriving predictive factors.

METHODS

In a monocentric, prospective, non-interventional observational study patients who had received at least one administration of a monoclonal CD20 antibody (mCD20Ab) within 9 months prior to vaccination were included to receive mRNA-based third vaccination. SARS-COV-2 IgG titer was determined before and four weeks after immunisation. Patients without adequate humoral immune response proceeded to a fourth vaccination. Furthermore, tolerability and prespecified potentially influencing factors such as age, baseline lymphocyte counts and others were analysed.

RESULTS

Twenty-four patients were included and vaccination was well tolerated. Quantitative analysis of humoral response four weeks after third vaccination revealed a significant increase which, however, did not translate into a clinically relevant seroconversion rate. In the subgroup analysis, patients older than 65 years and mCD20Ab therapy longer than 6 months ago benefited. All evaluable patients on mCD20Ab monotherapy (n = 7) showed an immediate or delayed immune response after third vaccination, while all non-responders (n = 7) were on combination therapy. Clinical parameters such as lymphocyte count, immunoglobulin status and others did not appear to have any influence.

CONCLUSION

An interval of at least 6 months after the last mCD20Ab administration and mCD20Ab monotherapy appears to be favorable for humoral immune response to third vaccination. Furthermore, patients can be reassured that delayed immune responses are possible. Future studies should therefore also investigate seroconversion at later time points.

Subcutaneous immunotherapy in a patient taking ofatumumab for multiple sclerosis and upadacitinib for atopic dermatitis

Allergen-specific immunotherapy has not been well-studied in the setting of increasingly common immune system-targeting medications. Subcutaneous immunotherapy may not be contraindicated in patients taking anti-CD20 mAbs antibodies and/or Janus kinase inhibitors.

Development and Preclinical Evaluation of [64Cu]Cu-NOTA-ABDB6: A CD70 and Albumin Dual-Binding Tracer with Improved Pharmacokinetics

CD70 is an emerging biomarker for both solid tumors and hematologic malignancies, highlighting the urgent need for a molecular imaging tracer capable of visualizing CD70 with favorable pharmacokinetics. Methods: ABDB6 was prepared by fusing the albumin-binding domain ABD035 with the CD70-targeting single-domain antibody RCCB6, which we previously reported. The resulting ABDB6 was then conjugated to the bifunctional chelator p-SCN-NOTA and labeled with 64Cu to produce [64Cu]Cu-NOTA-ABDB6. Flow cytometry was used to screen 6 lymphoma cell lines with varying CD70 expression levels. Cell uptake and in vivo immuno-PET imaging studies were conducted to fully evaluate the pharmacokinetic properties and tumor-targeting efficacy of [64Cu]Cu-NOTA-ABDB6. An ABDB6 blocking study was performed to validate the targeting specificity of [64Cu]Cu-NOTA-ABDB6, followed by immunohistochemistry and fluorescent immunostaining studies to correlate tracer uptake with CD70 expression. Results: 64Cu labeling of ABDB6 achieved a high radiochemical yield and specific activity. Significant CD70 expression was observed in 5 lymphoma cell lines (TMD8, HBL1, OCI-LY10, LCL-EBV, and type III latency Burkitt lymphoma [BL] cells) but not in type I latency BL cells, which served as the negative control. [64Cu]Cu-NOTA-ABDB6 exhibited good affinity for CD70 protein at the nanomolar level (inhibitory concentration of 50%, 91.57 nM) and specificity in binding to human CD70. Immuno-PET imaging of [64Cu]Cu-NOTA-ABDB6 demonstrated excellent tumor uptake and retention in various CD70-positive lymphoma models (TMD8, type III latency BL, and LCL-EBV), with the highest tumor uptake values recorded as 24.67 ± 1.36, 18.02 ± 4.29, and 14.68 ± 1.20 percentage injected dose per gram of tissue (%ID/g) at 48 h after injection, respectively. These tumor uptake values were significantly higher than that of the CD70-negative type I latency BL tumor, which had an uptake of 3.59 ± 0.28 %ID/g at the same scanning time point (P < 0.05). In the TMD8 blocking group, tumor uptake was 5.99 ± 1.20 %ID/g at 48 h after injection, significantly lower than in the TMD8 control group (P < 0.01). Both biodistribution and histology results corroborated these imaging findings. Conclusion: [64Cu]Cu-NOTA-ABDB6 immuno-PET effectively visualized varying levels of CD70 in different lymphoma models. Its clinical potential may provide insights into CD70 expression in lymphoma patients.

Rituximab (monoclonal anti-CD20 antibody) induced posterior reversible encephalopathy syndrome (PRES): A case report and literature review

Posterior reversible encephalopathy syndrome (PRES) is an uncommon neurological condition characterized by reversible subcortical vasogenic edema that primarily affects the posterior areas of the brain. Subcortical vasogenic edema resulting from endothelial injury and hypertension is the pathogenesis. Here, we present a 23-year-old female patient with systemic lupus erythematosus (SLE) and lupus nephritis who developed PRES following Rituximab (a monoclonal anti-CD-20 antibody) administration. The patient initially presented with severe headaches, visual disturbances, and an altered mental status. Neurological examination revealed bilateral cortical blindness, hyperreflexia, and seizures. Brain imaging, including MRI, demonstrated characteristic findings of PRES, with symmetric hyperintensities involving the occipital and parietal lobes on T2-weighted and FLAIR sequences, consistent with vasogenic edema. Rituximab is promptly discontinued, and the patient was managed with supportive care, including antiepileptic drugs and blood pressure control. Within days of Rituximab cessation, the patient showed gradual improvement in symptoms, with resolution of cortical blindness and normalization of MRI findings. Follow-up assessments revealed complete neurological recovery without residual deficits. This instance emphasizes how crucial it is to take into account PRES as a possible side effect in patients receiving Rituximab therapy, especially if those individuals have sudden neurological symptoms. The offending agent must be located and eliminated immediately for the best outcomes. Clinicians should maintain a high index of suspicion for PRES in patients receiving monoclonal anti-CD20 antibody therapies, immunosuppressants, and corticosteroids, facilitating timely diagnosis and intervention to prevent potentially life-threatening complications. More studies are necessary to clarify the pathophysiological mechanisms causing the PRES produced by Rituximab and to improve therapeutic approaches.

CAR T-Cell Therapy for Rheumatic Diseases: What Does the Future Hold?

Chimeric antigen receptor (CAR) T-cell therapy, initially successful in treating hematological malignancies, is emerging as a potential treatment for autoimmune diseases, including rheumatic conditions. CAR T cells, engineered to target and eliminate autoreactive B cells, offer a novel approach to managing diseases like systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and inflammatory myopathies, where B cells play a pivotal role in disease pathology. Early case reports have demonstrated promising results, with patients achieving significant disease remission, normalization of serological markers, and the ability to discontinue traditional immunosuppressive therapies, which supported the initiation of several clinical trials. However, the application of CAR T-cell therapy in chronic inflammatory rheumatic disorders poses unique challenges, including patient heterogeneity, the risk of adverse effects such as cytokine release syndrome, and the high costs associated with the therapy. Despite these challenges, the potential for CAR T cells to provide long-term remission or even a cure in refractory autoimmune diseases is significant. Ongoing research aims to optimize CAR T-cell constructs and improve safety profiles, paving the way for broader application in rheumatic diseases. If these challenges can be addressed, CAR T-cell therapy could revolutionize the treatment landscape for chronic inflammatory rheumatic disorders, offering new hope for patients with severe, treatment-resistant conditions.

The evolution of cancer immunotherapy: a comprehensive review of its history and current perspectives

Cancer immunotherapy uses the body's immune system to combat cancer, marking a significant advancement in treatment. This review traces its evolution from the late 19th century to its current status. It began with William Coley's pioneering work using bacterial toxins to stimulate the immune system against cancer cells, establishing the foundational concept of immunotherapy. In the mid-20th century, cytokine therapies like interferons and interleukins emerged, demonstrating that altering the immune response could reduce tumors and highlighting the complex interplay between cancer and the immune system. The discovery of immune checkpoints, regulatory pathways that prevent autoimmunity but are exploited by cancer cells to evade detection, was a pivotal development. Another major breakthrough is CAR-T cell therapy, which involves modifying a patient's T cells to target cancer-specific antigens. This personalized treatment has shown remarkable success in certain blood cancers. Additionally, cancer vaccines aim to trigger immune responses against tumor-specific or associated antigens, and while challenging, ongoing research is improving their efficacy. The historical progression of cancer immunotherapy, from Coley's toxins to modern innovations like checkpoint inhibitors and CAR-T cell therapy, underscores its transformative impact on cancer treatment. As research delves deeper into the immune system's complexities, immunotherapy is poised to become even more crucial in oncology, offering renewed hope to patients globally.

A tetraspecific engager armed with a non-alpha IL-2 variant harnesses natural killer cells against B cell non-Hodgkin lymphoma

NK cells offer a promising alternative to T cell therapies in cancer. We evaluated IPH6501, a clinical-stage, tetraspecific NK cell engager (NKCE) armed with a non-alpha IL-2 variant (IL-2v), which targets CD20 and was developed for treating B cell non-Hodgkin lymphoma (B-NHL). CD20-NKCE-IL2v boosts NK cell proliferation and cytotoxicity, showing activity against a range of B-NHL cell lines, including those with low CD20 density. Whereas it presented reduced toxicities compared with those commonly associated with T cell therapies, CD20-NKCE-IL2v showed greater killing efficacy over a T cell engager targeting CD20 in in vitro preclinical models. CD20-NKCE-IL2v also increased the cell surface expression of NK cell-activating receptors, leading to activity against CD20-negative tumor cells. In vivo studies in nonhuman primates and tumor mouse models further validated its efficacy and revealed that CD20-NKCE-IL2v induces peripheral NK cell homing at the tumor site. CD20-NKCE-IL2v emerges as a potential alternative in the treatment landscape of B-NHL.

Hemophagocytic lymphohistiocytosis: current treatment advances, emerging targeted therapy and underlying mechanisms

Hemophagocytic lymphohistiocytosis (HLH) is a rapidly progressing, life-threatening syndrome characterized by excessive immune activation, often presenting as a complex cytokine storm. This hyperactive immune response can lead to multi-organ failure and systemic damage, resulting in an extremely short survival period if left untreated. Over the past decades, although HLH has garnered increasing attention from researchers, there have been few advancements in its treatment. The cytokine storm plays a crucial role in the treatment of HLH. Investigating the detailed mechanisms behind cytokine storms offers insights into targeted therapeutic approaches, potentially aiding in early intervention and improving the clinical outcome of HLH patients. To date, there is only one targeted therapy, emapalumab targeting interferon-γ, that has gained approval for primary HLH. This review aims to summarize the current treatment advances, emerging targeted therapeutics and underlying mechanisms of HLH, highlighting its newly discovered targets potentially involved in cytokine storms, which are expected to drive the development of novel treatments and offer fresh perspectives for future studies. Besides, multi-targeted combination therapy may be essential for disease control, but further trials are required to determine the optimal treatment mode for HLH.

Impact of Rituximab on Remission Rates in Granulomatosis With Polyangiitis: A Systematic Review

This systematic review evaluates the efficacy of rituximab in inducing and maintaining remission in patients with granulomatosis with polyangiitis (GPA). We conducted a comprehensive search across multiple databases, identifying 81 studies, of which 11 met our inclusion criteria after rigorous screening and assessment for relevance and quality. Our analysis shows that rituximab, compared to traditional treatments such as cyclophosphamide and azathioprine, significantly improves remission rates and reduces relapse frequency in GPA patients. Notably, rituximab's benefits extend across various patient demographics, including pediatric groups, and are evident in different dosing regimens, highlighting its versatility and potential as a first-line therapy. The review also underscores the importance of personalized medicine approaches in managing GPA, as rituximab's effectiveness was particularly pronounced in patients with relapsing disease forms. Future research should focus on long-term outcomes, optimal dosing strategies, and the economic implications of widespread rituximab use in clinical practice. Our findings advocate for the integration of rituximab into standard treatment protocols for GPA, offering new hope for patients afflicted with this challenging autoimmune disorder.

Reverse repurposing: Potential utility of cancer drugs in nonmalignant illnesses

Growth and immune process dysregulation can result in both cancer and nonmalignant disease (hereditary or acquired, with and without predisposition to malignancy). Moreover, perhaps unexpectedly, many nonmalignant illnesses harbor genomic alterations indistinguishable from druggable oncogenic drivers. Therefore, targeted compounds used successfully to treat cancer may have therapeutic potential for nonmalignant conditions harboring the same target. MEK, PI3K/AKT/mTOR, fibroblast growth factor receptor (FGFR), and NRG1/ERBB pathway genes have all been implicated in both cancer and noncancerous conditions, and several cognate antagonists, as well as Bruton's tyrosine kinase inhibitors, JAK inhibitors, and CD20-directed antibodies, have established or theoretical therapeutic potential to bridge cancer and benign diseases. Intriguingly, pharmacologically tractable cancer drivers characterize a wide spectrum of disorders without malignant potential, including but not limited to Alzheimer's disease and a variety of other neurodegenerative conditions, rheumatoid arthritis, achondroplastic dwarfism, and endometriosis. Expanded repositioning of oncology agents in order to benefit benign but serious medical illnesses is warranted.

What is novel in the clinical management of pemphigus vulgaris?

INTRODUCTION

Pemphigus, an uncommon autoimmune blistering disorder affecting the skin and mucous membranes, currently with mortality primarily attributed to adverse reactions resulting from treatment protocols. Additionally, the existing treatments exhibit a notable recurrence rate. The high incidence of relapse and the considerable adverse effects associated with treatment underscore the imperative to explore safer and more effective therapeutic approaches. Numerous potential therapeutic targets have demonstrated promising outcomes in trials or preliminary research stages. These encompass anti-CD-20 agents, anti-CD-25 agents, TNF-α inhibition, FAS Ligand Inhibition, FcRn inhibition, BAFF inhibition, Bruton's tyrosine kinase (BTK) inhibition, CAAR T Cells, JAK inhibition, mTOR inhibition, abatacept, IL-4 inhibition, IL-17 inhibition, IL-6 inhibition, polyclonal Regulatory T Cells, and autologous hematopoietic stem cell transplantation.

AREAS COVERED

The most significant studies regarding the impact and efficacy of the mentioned treatments on pemphigus were meticulously curated through a comprehensive search conducted on the PubMed database. Moreover, the investigations of interest cited in these studies were also integrated.

EXPERT OPINION

The efficacy and safety profiles of the other treatments under discussion do not exhibit the same level of robustness as anti-CD20 therapy, which is anticipated to endure as a critical element in pemphigus treatment well into the foreseeable future.

CD19/CD20 dual-targeted chimeric antigen receptor-engineered natural killer cells exhibit improved cytotoxicity against acute lymphoblastic leukemia

BACKGROUND

Chimeric antigen receptor natural killer (CAR-NK) cells represent a promising advancement in CAR cell therapy, addressing limitations observed in CAR-T cell therapy. However, our prior study revealed challenges in CAR-NK cells targeting CD19 antigens, as they failed to eliminate CD19+ Raji cells in NSG tumor-bearing mice, noting down-regulation or loss of CD19 antigen expression in some Raji cells. In response, this study aims to enhance CD19 CAR-NK cell efficacy and mitigate the risk of tumor recurrence due to target antigen escape by developing CD19 and CD20 (CD19/CD20) dual-targeted CAR-NK cells.

METHODS

Initially, mRNA encoding anti-CD19 CARs (FMC63 scFv-CD8α-4-1BB-CD3ζ) and anti-CD20 CARs (LEU16 scFv-CD8α-4-1BB-CD3ζ) was constructed via in vitro transcription. Subsequently, CD19/CD20 dual-targeted CAR-NK cells were generated through simultaneous electrotransfection of CD19/CD20 CAR mRNA into umbilical cord blood-derived NK cells (UCB-NK).

RESULTS

Following co-electroporation, the percentage of dual-CAR expression on NK cells was 86.4% ± 1.83%, as determined by flow cytometry. CAR expression was detectable at 8 h post-electric transfer, peaked at 24 h, and remained detectable at 96 h. CD19/CD20 dual-targeted CAR-NK cells exhibited increased specific cytotoxicity against acute lymphoblastic leukemia (ALL) cell lines (BALL-1: CD19+CD20+, REH: CD19+CD20-, Jurkat: CD19-CD20-) compared to UCB-NK, CD19 CAR-NK, and CD20 CAR-NK cells. Moreover, CD19/CD20 dual-targeted CAR-NK cells released elevated levels of perforin, IFN-γ, and IL-15. Multiple activation markers such as CD69 and cytotoxic substances were highly expressed.

CONCLUSIONS

The creation of CD19/CD20 dual-targeted CAR-NK cells addressed the risk of tumor escape due to antigen heterogeneity in ALL, offering efficient and safe 'off-the-shelf' cell products. These cells demonstrate efficacy in targeting CD20 and/or CD19 antigens in ALL, laying an experimental foundation for their application in ALL treatment.

Bendamustine impairs humoral but not cellular immunity to SARS-CoV-2 vaccination in rituximab-treated B-cell lymphoma-affected patients

Background

Patients with B-cell lymphoma are a fragile category of subjects, particularly exposed to infections and characterized by an impaired vaccination response due to the disease itself and, even more, to the chemotherapy regimen. For this reason, extensive knowledge of the immune response status of these subjects is of fundamental importance to obtain possible indications for a tailored immunization strategy.

Methods

We enrolled two cohorts of patients with B-cell lymphoma under rituximab treatment or 3-24 months after treatment. In all patients, we evaluated both humoral and cellular immunological memory toward SARS-CoV-2, after standard vaccination and upon one booster dose.

Results

We observed no Spike-specific IgG production in patients (n = 25) under anti-CD20 treatment, whereas patients (n = 16) vaccinated after the completion of chemotherapy showed a higher humoral response. Evaluating SARS-CoV-2-specific T-cell response, we found that patients in both cohorts had developed robust cellular immunity after vaccination. Of the 21 patients (51%) that experienced a breakthrough SARS-CoV-2 infection, only six patients developed severe disease. Interestingly, these six patients had all been treated with rituximab plus bendamustine. Notably, we observed that Spike-specific IgG levels in patients treated with rituximab plus bendamustine were absent or lower compared with those in patients treated with rituximab plus other chemotherapy, whereas Spike-specific T-cell response was not different based on chemotherapy regiment.

Discussion

Our results show that, in patients with B-cell lymphoma under rituximab therapy, anti-SARS-CoV-2 mRNA vaccination induces a weak or absent humoral response but a consistent T-cell response. In addition, chemotherapy regimens with bendamustine further reduce patients' ability to mount a Spike-specific humoral response even after a long time period from chemotherapy discontinuation. These results provide evidence that different chemotherapeutics display different immunosuppressive properties that could be taken in to account in the choice of the right drug regimen for the right patient. Moreover, they question whether immunocompromised patients, particularly those treated with bendamustine, need interventions to improve vaccine-induced immune response.

Autoantigen-selected B cells are bystanders in spontaneous T cell-driven experimental autoimmune hepatitis

Autoreactive B cells are considered pathogenic drivers in many autoimmune diseases; however, it is not clear whether autoimmune B cells are invariably pathogenic or whether they can also arise as bystanders of T cell-driven autoimmune pathology. Here, we studied the B cell response in an autoantigen- and CD4+ T cell-driven model of autoimmune hepatitis (AIH), the Alb-iGP_Smarta mouse in which expression of a viral model antigen (GP) in hepatocytes and its recognition by GP-specific CD4+ T cells causes spontaneous AIH-like disease. T cell-driven AIH in Alb-iGP_Smarta mice was marked by autoantibodies and hepatic infiltration of plasma cells and B cells, particularly of isotype-switched memory B cells, indicating antigen-driven selection and activation. Immunosequencing of B cell receptor repertoires confirmed B cell expansion selectively in the liver, which was most likely driven by the hepatic GP model antigen, as indicated by branched networks of connected sequences and elevated levels of IgG antibodies to GP. However, intrahepatic B cells did not produce increased levels of cytokines and their depletion with anti-CD20 antibody did not alter the CD4+ T cell response in Alb-iGP_Smarta mice. Moreover, B cell depletion did not prevent spontaneous liver inflammation and AIH-like disease in Alb-iGP_Smarta mice. In conclusion, selection and isotype-switch of liver-infiltrating B cells was dependent on the presence of CD4+ T cells recognizing liver antigen. However, recognition of hepatic antigen by CD4+ T cells and CD4+ T cell-mediated hepatitis was not dependent on B cells. Thus, autoreactive B cells can be bystanders and need not be drivers of liver inflammation in AIH.

Development of Stable CHO-K1 Cell Lines Overexpressing Full-Length Human CD20 Antigen

Background

CD20 is a differentiation-related antigen exclusively expressed on the membrane of B lymphocytes. CD20 amplification is observed in numerous immune-related disorders, making it an ideal target for immunotherapy of hematological malignancies and autoimmune diseases. MAb-based therapies targeting CD20 have a principal role in the treatment of several immune-related disordes and cancers, including CLL. Fc gamma receptors mediate CD20 internalization in hematopoietic cells; therefore, this study aimed to establish non-hematopoietic stable cell lines overexpressing full-length human CD20 antigen as an in vitro model for CD20-related studies.

Methods

CD20 gene was cloned into the transfer vector. The lentivirus system was transfected to packaging HEK 293T cells, and the supernatants were harvested. CHO-K1 cells were transduced using recombinant viruses, and a stable cell pool was developed by the antibiotic selection. CD20 expression was confirmed at the mRNA and protein levels.

Results

Simultaneous expression of GFP protein facilitated the detection of CD20-expressing cells. Immunophenotyping analysis of stable clones demonstrated expression of CD20 antigen. In addition, the mean fluorescence intensity was significantly higher in the CD20-CHO-K1 clones than the wild-type CHO-K1 cells.

Conclusion

This study is the first report on using second-generation lentiviral vectors for the establishment of a non-hematopoietic cell-based system, which stably expresses full-length human CD20 antigen. Results of stable CHO cell lines with different levels of CD20 antigen are well suited to be used for CD20-based investigations, including binding and functional assays.

Future landscape for the management of membranous nephropathy

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

Pharmacogenomic Analyses Implicate B Cell Developmental Status and MKL1 as Determinants of Sensitivity toward Anti-CD20 Monoclonal Antibody Therapy

Monoclonal antibody (mAb) therapy directed against CD20 is an important tool in the treatment of B cell disorders. However, variable patient response and acquired resistance remain important clinical challenges. To identify genetic factors that may influence sensitivity to treatment, the cytotoxic activity of three CD20 mAbs: rituximab; ofatumumab; and obinutuzumab, were screened in high-throughput assays using 680 ethnically diverse lymphoblastoid cell lines (LCLs) followed by a pharmacogenomic assessment. GWAS analysis identified several novel gene candidates. The most significant SNP, rs58600101, in the gene MKL1 displayed ethnic stratification, with the variant being significantly more prevalent in the African cohort and resulting in reduced transcript levels as measured by qPCR. Functional validation of MKL1 by shRNA-mediated knockdown of MKL1 resulted in a more resistant phenotype. Gene expression analysis identified the developmentally associated TGFB1I1 as the most significant gene associated with sensitivity. qPCR among a panel of sensitive and resistant LCLs revealed immunoglobulin class-switching as well as differences in the expression of B cell activation markers. Flow cytometry showed heterogeneity within some cell lines relative to surface Ig isotype with a shift to more IgG⁺ cells among the resistant lines. Pretreatment with prednisolone could partly reverse the resistant phenotype. Results suggest that the efficacy of anti-CD20 mAb therapy may be influenced by B cell developmental status as well as polymorphism in the MKL1 gene. A clinical benefit may be achieved by pretreatment with corticosteroids such as prednisolone followed by mAb therapy.

Mechanisms of Action and Limitations of Monoclonal Antibodies and Single Chain Fragment Variable (scFv) in the Treatment of Cancer

Monoclonal antibodies are among the most effective tools for detecting tumor-associated antigens. The U.S. Food and Drug Administration (FDA) has approved more than 36 therapeutic antibodies for developing novel alternative therapies that have significant success rates in fighting cancer. However, some functional limitations have been described, such as their access to solid tumors and low interaction with the immune system. Single-chain variable fragments (scFv) are versatile and easy to produce, and being an attractive tool for use in immunotherapy models. The small size of scFv can be advantageous for treatment due to its short half-life and other characteristics related to the structural and functional aspects of the antibodies. Therefore, the main objective of this review was to describe the current situation regarding the mechanisms of action, applications, and limitations of monoclonal antibodies and scFv in the treatment of cancer.

Hypogammaglobulinemia, late-onset neutropenia, and infections following rituximab

Rituximab is a chimeric anti-CD20 monoclonal antibody that targets CD20-expressing B lymphocytes, has a well-defined efficacy and safety profile, and is broadly used to treat a wide array of diseases. In this review, we cover the mechanism of action of rituximab and focus on hypogammaglobulinemia and late-onset neutropenia-2 immune effects secondary to rituximab-and subsequent infection. We review risk factors and highlight key considerations for immunologic monitoring and clinical management of rituximab-induced secondary immune deficiencies. In patients treated with rituximab, monitoring for hypogammaglobulinemia and infections may help to identify the subset of patients at high risk for developing poor B cell reconstitution, subsequent infections, and adverse complications. These patients may benefit from early interventions such as vaccination, antibacterial prophylaxis, and immunoglobulin replacement therapy. Systematic evaluation of immunoglobulin levels and peripheral B cell counts by flow cytometry, both at baseline and periodically after therapy, is recommended for monitoring. In addition, in those patients with prolonged hypogammaglobulinemia and increased infections after rituximab use, immunologic evaluation for inborn errors of immunity may be warranted to further risk stratification, increase monitoring, and assist in therapeutic decision-making. As the immunologic effects of rituximab are further elucidated, personalized approaches to minimize the risk of adverse reactions while maximizing benefit will allow for improved care of patients with decreased morbidity and mortality.

Risk of Infections Secondary to the Use of Targeted Therapies in Hematological Malignancies

Concurrent infections in hematological malignancies (HM) are major contributors to adverse clinical outcomes, including prolonged hospitalization and reduced life expectancy. Individuals diagnosed with HM are particularly susceptible to infectious pathogens due to immunosuppression, which can either be inherent to the hematological disorder or induced by specific therapeutic strategies. Over the years, the treatment paradigm for HM has witnessed a tremendous shift, from broad-spectrum treatment approaches to more specific targeted therapies. At present, the therapeutic landscape of HM is constantly evolving due to the advent of novel targeted therapies and the enhanced utilization of these agents for treatment purposes. By initiating unique molecular pathways, these agents hinder the proliferation of malignant cells, consequently affecting innate and adaptive immunity, which increases the risk of infectious complications. Due to the complexity of novel targeted therapies and their associated risks of infection, it often becomes a daunting task for physicians to maintain updated knowledge in their clinical practice. The situation is further aggravated by the fact that most of the initial clinical trials on targeted therapies provide inadequate information to determine the associated risk of infection. In such a scenario, a cumulative body of evidence is paramount in guiding clinicians regarding the infectious complications that can arise following targeted therapies. In this review, I summarize the recent knowledge on infectious complications arising in the context of targeted therapies for HM.

Combination of High-Resolution Structures for the B Cell Receptor and Co-Receptors Provides an Understanding of Their Interactions with Therapeutic Antibodies

B cells are central to the adaptive immune response, providing long lasting immunity after infection. B cell activation is mediated by a cell surface B cell receptor (BCR) following recognition of an antigen. BCR signaling is modulated by several co-receptors including CD22 and a complex that contains CD19 and CD81. Aberrant signaling through the BCR and co-receptors promotes the pathogenesis of several B cell malignancies and autoimmune diseases. Treatment of these diseases has been revolutionized by the development of monoclonal antibodies that bind to B cell surface antigens, including the BCR and its co-receptors. However, malignant B cells can escape targeting by several mechanisms and until recently, rational design of antibodies has been limited by the lack of high-resolution structures of the BCR and its co-receptors. Herein we review recently determined cryo-electron microscopy (cryo-EM) and crystal structures of the BCR, CD22, CD19 and CD81 molecules. These structures provide further understanding of the mechanisms of current antibody therapies and provide scaffolds for development of engineered antibodies for treatment of B cell malignancies and autoimmune diseases.

Update on the Application of Monoclonal Antibody Therapy in Primary Membranous Nephropathy

When first introduced, rituximab (RTX), a chimeric anti-CD20 monoclonal antibody, brought about an alternative therapeutic paradigm for primary membranous nephropathy (PMN). Rituximab was shown to be effective and safe in PMN patients with kidney dysfunction, with. patients receiving second-line rituximab therapy achieving remission as effectively as those patients who had not previously received immunotherapy. No safety issues were reported. The B cell-driven protocol seems to be as efficient as the 375 mg/m² × 4 regimen or 1 g × 2 regimen in achieving B cell depletion and remission, but patients with high M-type phospholipase A2 receptor (PLA2R) antibody levels may benefit from a higher dose of rituximab. While rituximab added another therapeutic option to the treatment regimen, it does have limitations as 20 to 40% of patients do not respond. Not all patients respond to RTX therapy for lymphoproliferative disorders either, therefore further novel anti-CD20 monoclonal antibodies have been developed and these may provide alternative therapeutic options for PMN. Ofatumumab, a fully human monoclonal antibody, specifically recognizes an epitope encompassing both the small and large extracellular loops of the CD20 molecule, resulting in increased complement-dependent cytotoxic activity. Ocrelizumab binds an alternative but overlapping epitope region to rituximab and displays enhanced antibody-dependent cellular cytotoxic (ADCC) activities. Obinutuzumab is designed to have a modified elbow-hinge amino acid sequence, leading to increased direct cell death induction and ADCC activities. In PMN clinical studies, ocrelizumab and obinutuzumab showed promising results, while ofatumumab displayed mixed results. However, there is a lack of randomized controlled trials with large samples, especially direct head-to-head comparisons. Alternative molecular mechanisms have been suggested in this context to explore novel therapeutic strategies. B cell activator-targeted, plasma cell-targeted and complement-directed treatments may lead to novel therapy paradigms for PMN. Exploratory strategies for the use of drugs with different mechanisms, such as a combination of rituximab and cyclophosphamide and a steroid, a combination of rituximab and a calcineurin inhibitor, may provide more rapid and efficient remission, but the combination of standard immunosuppression with rituximab could increase infection risk.

Development of a novel, highly sensitive assay for quantification of minimal residual B cells in autoimmune disease and comparison to traditional methods across B-cell-depleting agents

Targeted B-cell depletion is a useful therapy for many diseases, including autoimmune disorders and certain cancers. We developed a sensitive blood B-cell depletion assay, MRB 1.1, compared its performance with the T-cell/B-cell/NK-cell (TBNK) assay, and assessed B-cell depletion with different therapies. The empirically defined lower limit of quantification (LLOQ) for CD19+ cells in the TBNK assay was 10 cells/μL, and 0.441 cells/μL for the MRB 1.1 assay. The TBNK LLOQ was used to compare differences between B-cell depletion in similar lupus nephritis patient populations who received rituximab (LUNAR), ocrelizumab (BELONG), or obinutuzumab (NOBILITY). After 4 weeks, 10% of patients treated with rituximab retained detectable B cells vs 1.8% with ocrelizumab and 1.7% for obinutuzumab; at 24 weeks 93% of patients who received obinutuzumab remained below LLOQ vs 63% for rituximab. More-sensitive measurements of B cells may reveal differences in potency among anti-CD20 agents, which may associate with clinical outcomes.

Implications of rituximab pharmacokinetic and pharmacodynamic alterations in various immune-mediated glomerulopathies and potential anti-CD20 therapy alternatives

The specific B-cell depleting anti-CD20 monoclonal antibody rituximab (RTX) is effective in terms of the treatment of various immune-mediated glomerulopathies. The administration of RTX has been shown to be reliable and highly effective particularly in patients with ANCA-associated vasculitis, which is manifested predominantly with non-nephrotic proteinuria. Stable long-term B-cell depletion is usually readily attained in such patients using standard dosing regimens. However, in patients with nephrotic syndrome and non-selective proteinuria, the RTX pharmacokinetics is altered profoundly and RTX does not maintain high enough levels for a sufficiently long period, which may render RTX treatment ineffective. Since complement-derived cytotoxicity is one of the important modes of action of RTX, hypocomplementemia, frequently associated with systemic lupus erythematodes, may act to hamper the efficacy of RTX in the treatment of patients with lupus nephritis. This review provides a description of RTX pharmacokinetics and pharmacodynamics in several selected glomerulopathies, as well as the impact of proteinuria, anti-drug antibodies and other clinical variables on the clearance and volume of distribution of RTX. The impact of plasmapheresis and peritoneal dialysis on the clearance of RTX is also discussed in the paper. A review is provided of the potential association between pharmacokinetic and pharmacodynamic alterations in various kidney-affecting glomerular diseases, the sustainability of B-cell depletion and the clinical efficacy of RTX, with proposals for potential dosing implications. The role of therapeutic drug monitoring in treatment tailoring is also discussed, and various previously tested RTX dosing schedules are compared in terms of their clinical and laboratory treatment responses. Since alternative anti-CD20 molecules may prove effective in RTX unresponsive patients, their pharmacokinetics, pharmacodynamics and current role in the treatment of glomerulopathies are also mentioned.

Chicken-derived CD20 antibodies with potent B-cell depletion activity

We report four novel anti-human CD20 (hCD20) monoclonal antibodies (mAbs) discovered from a phylogenetically distant species-chickens. The chicken-human chimaeric antibodies exhibit at least 10-fold enhanced antibody-dependent cellular cytotoxicity (ADCC) and 4-8-fold stronger complement-dependent cytotoxicity (CDC) relative to the clinically used mouse-human chimaeric anti-hCD20 antibody rituximab (RTX). Thus, to our knowledge these mAbs are the first to significantly outperform RTX in both Fc-mediated mechanisms of action. The antibodies show 20-100-fold superior depletion of B cells in whole blood from healthy humans relative to RTX and retain efficacy in vivo. One of the mAbs, AC1, can bind mouse CD20, indicating specificity for a novel hCD20 epitope inaccessible to current (mouse-derived) anti-hCD20 mAbs. A humanized version of one antibody, hAC11-10, was created by complementarity-determining region (CDR) grafting into a human variable region framework and this molecule retained the ADCC, in vitro human whole-blood B-cell depletion, and in vivo lymphoma cell depletion activities of the parent. These mAbs represent promising monotherapy candidates for improving upon current less-than-ideal clinical outcomes in lymphoid malignancies and provide an arsenal of biologically relevant molecules for the development of next-generation CD20-mediated immunotherapies including bispecific T-cell engagers (BiTE), antibody-drug conjugates (ADC) and chimaeric antigen receptor-engineered T (CAR-T) cells.

Polyneuropathy Associated with IgM Monoclonal Gammopathy; Advances in Genetics and Treatment, Focusing on Anti-MAG Antibodies

With increasing age, the chances of developing either MGUS or polyneuropathy increase as well. In some cases, there is a causative relationship between the IgM M-protein and polyneuropathy. In approximately half of these cases, IgM targets the myelin-associated glycoprotein (MAG). This results in chronic polyneuropathy with slowly progressive, predominantly sensory neurological deficits and distally demyelinating features in nerve conduction studies. Despite the disease being chronic and developing slowly, it can cause considerable impairment. We reviewed English medical publications between 1980 and May 2022 on IgM gammopathy-associated polyneuropathy, with special attention to studies addressing the pathophysiology or treatment of anti-MAG polyneuropathy. Treatment options have been limited to a temporizing effect of intravenous immunoglobulins in some patients and a more sustained effect of rituximab but in only 30 to 55 percent of patients. An increase in our knowledge concerning genetic mutations, particularly the MYD88L265P mutation, led to the development of novel targeted treatment options such as BTK inhibitors. Similarly, due to the increasing knowledge of the pathophysiology of anti-MAG polyneuropathy, new treatment options are emerging. Since anti-MAG polyneuropathy is a rare disease with diverse symptomatology, large trials with good outcome measures are a challenge.

Rituximab in Myasthenia Gravis- Experience from a Low- and Middle-Income Country (LMIC) Setting

BACKGROUND

Myasthenia gravis (MG) is an immune-mediated disorder of the neuromuscular junction. About 10% are refractory to immunosuppressive therapy.

AIMS

To analyze the response of patients with generalized MG to rituximab.

METHODS AND MATERIALS

A retrospective review of patients with MG who received rituximab was carried out (n = 13, M:F = 6:7, mean age: 44.84 ± 15.73 years). Myasthenia Gravis Foundation of America (MGFA), MGFA post-intervention status (MGFA-PIS), and Myasthenia Gravis Status and Treatment Intensity (MGSTI) were assessed before and after rituximab.

RESULTS

The duration of MG was 104.07 ± 92.25 months. Before rituximab, the MGFA was IIA/IIB/IIIA/IIIB/IVB/V in 1/1/2/6/2/1 patients and MGSTI was four in eight patients and six in three patients. The mean duration of follow up was 20.92 ± 14.06 months (range, 4 to 42 months). Dose reduction or discontinuation of cholinesterase inhibitors could be achieved 12 patients. Complete stable remission (CSR) and pharmacologic remission (PR) were achieved in one and four patients respectively and five patients had minimal manifestations. Most patients attained level 0, 1 or 2 MGSTI at last follow up. No rituximab infusion-related adverse events were noted. Three patients had exacerbation of MG between one to five weeks after rituximab administration. Three patients died, one each due to a cardiac event unrelated to MG or treatment, complications related to myasthenic crisis, and coronavirus disease.

CONCLUSIONS

Rituximab was effective in bringing about remission in MG and can be considered as a first-line agent. However, it has to be administered under close supervision as some patients develop exacerbation of MG akin to steroid-induced worsening.

Isolation and characterization of human anti-CD20 single-chain variable fragment (scFv) from a Naive human scFv library

CD20 is a receptor expressed on B cells with anonymous functions. The receptor is the target of some food and drug administration (FDA) approved monoclonal antibodies (mAb), such as Rituximab and Obinutuzumab. Blocking CD20 using the aforementioned mAbs has improved Non-Hodgkin Lymphoma (NHL) therapy. All commercial mAbs on the market were raised in non-human animal models. Antibody humanization is inevitable to mitigate immune response. In order to keep the affinity of antibody intact, humanizations are only applied to frameworks which do not eliminate immune response to foreign CDRs sequences. To address this issue, human monoclonal antibody deemed imperative. Herein, we report the isolation and characterization of a fully human single-chain variable fragment (scFv) against the large loop of CD20 from naïve human antibody library. After three rounds of phage display, a library of enriched anti-CD20 scFv was obtained. The polyclonal phage ELISA demonstrated that after each round of phage display, the population of anti-CD20 scFv became dominant. The scFv, G7, with the most robust interaction with CD20 was selected for further characterization. The specificity of G7 scFv was evaluated by ELISA, western blot, and flow cytometry. Detecting CD20 in western blot showed that G7 binds to a linear epitope on CD20 large loop. Next, G7 scFv was also bound to Raji cell (CD20⁺) while no interaction was recorded with K562 cell line (CD20^—). This data attested that the epitope recognized by G7 scFv is accessible on the cell membrane. The affinity of G7 scFv was estimated to be 63.41 ± 3.9 nM. Next, the sensitivity was evaluated to be 2 ng/ml. Finally, G7 scFv tertiary structure was modeled using Graylab software. The 3D structure illustrated two domains of variable heavy (V_H) and variable light (V_L) connected through a linker. Afterward, G7 scFv and CD20 were applied to in-silico docking using ClusPro to illustrate the interaction of G7 with the large loop of CD20. As the selected scFv from the human antibody library is devoid of interspecies immunogenic amino acids sequences, no humanization or any other modifications are required prior to clinical applications.

Immunoglobulin treatment for B-cell immunodeficiencies

This article aims to describe the rationale and utility of immunoglobulin therapies in patients with B-cell immunodeficiency states. We describe the historical perspective, mechanism of actions, and indications for use in this population. We then focus upon management pearls and special considerations for its utility. Finally, we elaborate upon the important economic implications for these patients and the need to develop individualized management strategies in this vulnerable population.

Cumulative SARS-CoV-2 mutations and corresponding changes in immunity in an immunocompromised patient indicate viral evolution within the host

Different scenarios explaining the emergence of novel variants of concern (VOC) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported, including their evolution in scarcely monitored populations, in animals as alternative hosts, or in immunocompromised individuals. Here we report SARS-CoV-2 immune escape mutations over a period of seven months in an immunocompromised patient with prolonged viral shedding. Signs of infection, viral shedding and mutation events are periodically analyzed using RT-PCR and next-generation sequencing based on naso-pharyngeal swabs, with the results complemented by immunological diagnostics to determine humoral and T cell immune responses. Throughout the infection course, 17 non-synonymous intra-host mutations are noted, with 15 (88.2%) having been previously described as prominent immune escape mutations (S:E484K, S:D950N, S:P681H, S:N501Y, S:del(9), N:S235F and S:H655Y) in VOCs. The high frequency of these non-synonymous mutations is consistent with multiple events of convergent evolution. Thus, our results suggest that specific mutations in the SARS-CoV-2 genome may represent positions with a fitness advantage, and may serve as targets in future vaccine and therapeutics development for COVID-19.

Structural Characterization of the Full-Length Anti-CD20 Antibody Rituximab

Rituximab, a murine–human chimera, is the first monoclonal antibody (mAb) developed as a therapeutic agent to target CD20 protein. Its Fab domain and its interaction with CD20 have been extensively studied and high-resolution atomic models obtained by X-ray diffraction or cryo-electron microscopy are available. However, the structure of the full-length antibody is still missing as the inherent protein flexibility hampers the formation of well-diffracting crystals and the reconstruction of 3D microscope images. The global structure of rituximab from its dilute solution is here elucidated by small-angle X-ray scattering (SAXS). The limited data resolution achievable by this technique has been compensated by intensive computational modelling that led to develop a new and effective procedure to characterize the average mAb conformation as well as that of the single domains. SAXS data indicated that rituximab adopts an asymmetric average conformation in solution, with a radius of gyration and a maximum linear dimension of 52 Å and 197 Å, respectively. The asymmetry is mainly due to an uneven arrangement of the two Fab units with respect to the central stem (the Fc domain) and reflects in a different conformation of the individual units. As a result, the Fab elbow angle, which is a crucial determinant for antigen recognition and binding, was found to be larger (169°) in the more distant Fab unit than that in the less distant one (143°). The whole flexibility of the antibody has been found to strongly depend on the relative inter-domain orientations, with one of the Fab arms playing a major role. The average structure and the amount of flexibility has been studied in the presence of different buffers and additives, and monitored at increasing temperature, up to the complete unfolding of the antibody. Overall, the structural characterization of rituximab can help in designing next-generation anti-CD20 antibodies and finding more efficient routes for rituximab production at industrial level.

Effects of a Fully Humanized Type II Anti-CD20 Monoclonal Antibody on Peripheral and CNS B Cells in a Transgenic Mouse Model of Multiple Sclerosis

Successful therapy with anti-CD20 monoclonal antibodies (mAbs) has reinforced the key role of B cells in the immunopathology of multiple sclerosis (MS). This study aimed to determine the effects of a novel class of anti-CD20 mAbs on vascular and extravascular central nervous system (CNS)-infiltrating B cells in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Male hCD20xhIgR3 mice and wild-type C57BL/6 (B6) mice were immunized with human myelin oligodendrocyte glycoprotein (MOG)_1–125 to induce EAE. While hCD20xhIgR3 mice were injected intravenously with an anti-human CD20 mAb (5 mg/kg) (rituximab (a type I anti-CD20 mAb) or obinutuzumab (a type II anti-CD20 mAb), B6 mice received the anti-mouse CD20 antibody 18B12. Neither mAb affected clinical disease or serum antibody levels. Obinutuzumab and rituximab had an impact on splenic and CNS-infiltrated B cells with slightly differential depletion efficacy. Additionally, obinutuzumab had beneficial effects on spinal cord myelination. B cell depletion rates in the 18B12/B6 model were comparable with those observed in obinutuzumab-treated hCD20xhIgR3 mice. Our results demonstrate the usefulness of anti-CD20 mAbs for the modulation of B cell-driven peripheral immune response and CNS pathology, with type II antibodies potentially being superior to type I in the depletion of tissue-infiltrating B cells.

Characterization of the canine CD20 as a therapeutic target for comparative passive immunotherapy

Anti-CD20 therapies have revolutionized the treatment of B-cell malignancies. Despite these advances, relapsed and refractory disease remains a major treatment challenge. The optimization of CD20-targeted immunotherapies is considered a promising strategy to improve current therapies. However, research has been limited by the scarcity of preclinical models that recapitulate the complex interaction between the immune system and cancers. The addition of the canine lymphoma (cNHL) model in the development of anti-CD20 therapies may provide a clinically relevant approach for the translation of improved immunotherapies. Still, an anti-CD20 therapy for cNHL has not been established stressing the need of a comprehensive target characterization. Herein, we performed an in-depth characterization on canine CD20 mRNA transcript and protein expression in a cNHL biobank and demonstrated a canine CD20 overexpression in B-cell lymphoma samples. Moreover, CD20 gene sequencing analysis identified six amino acid differences in patient samples (C77Y, L147F, I159M, L198V, A201T and G273E). Finally, we reported the use of a novel strategy for the generation of anti-CD20 mAbs, with human and canine cross-reactivity, by exploring our rabbit derived single-domain antibody platform. Overall, these results support the rationale of using CD20 as a target for veterinary settings and the development of novel therapeutics and immunodiagnostics.

New and Old Anti-CD20 Monoclonal Antibodies for Nephrotic Syndrome. Where We Are?

Nephrotic proteinuria is the hallmark of several glomerulonephritis determined by different pathogenetic mechanisms, including autoimmune, degenerative and inflammatory. Some conditions such as Minimal Change Nephropathy (MCN) and Focal Segmental Glomerulosclerosis (FSGS) are of uncertain pathogenesis. Chimeric anti-CD20 monoclonal antibodies have been used with success in a part of proteinuric conditions while some are resistant. New human and humanized monoclonal anti-CD 20 antibodies offer some advantages based on stronger effects on CD20 cell subtypes and have been already administered in hematology and oncology areas as substitutes of chimeric molecules. Here, we revised the literature on the use of human and humanized anti-CD 20 monoclonal antibodies in different proteinuric conditions, resulting effective in those conditions resistant to rituximab. Literature on the use of human anti-CD 20 monoclonal antibodies in different proteinuric diseases is mainly limited to ofatumumab, with several protocols and doses. Studies already performed with ofatumumab given in standard doses of 1,500 mg 1.73m² suggest no superiority compared to rituximab in children and young adults with steroid dependent nephrotic syndrome. Ofatumumab given in very high doses (300 mg/1.73m² followed by five infusion 2,000 mg/1.73 m²) seems more effective in patients who are not responsive to common therapies. The question of dose remains unresolved and the literature is not concordant on positive effects of high dose ofatumumab in patients with FSGS prior and after renal transplantation. Obinutuzumab may offer some advantages. In the unique study performed in patients with multidrug dependent nephrotic syndrome reporting positive effects, obinutuzumab was associated with the anti-CD38 monoclonal antibody daratumumab proposing the unexplored frontier of combined therapies. Obinutuzumab represent an evolution also in the treatment of autoimmune glomerulonephritis, such as membranous nephrotahy and lupus nephritis. Results of randomized trials, now in progress, are awaited to add new possibilities in those cases that are resistant to other drugs. The aim of the present review is to open a discussion among nephrologists, with the hope to achieve shared approaches in terms of type of antibodies and doses in the different proteinuric renal conditions.

BMFPs, a versatile therapeutic tool for redirecting a preexisting Epstein-Barr virus antibody response toward defined target cells

Industrial production of therapeutic monoclonal antibodies is mostly performed in eukaryotic-based systems, allowing posttranslational modifications mandatory for their functional activity. The resulting elevated product cost limits therapy access to some patients. To address this limitation, we conceptualized a novel immunotherapeutic approach to redirect a preexisting polyclonal antibody response against Epstein-Barr virus (EBV) toward defined target cells. We engineered and expressed in bacteria bimodular fusion proteins (BMFPs) comprising an Fc-deficient binding moiety targeting an antigen expressed at the surface of a target cell, fused to the EBV-P18 antigen, which recruits circulating endogenous anti-P18 IgG in EBV⁺ individuals. Opsonization of BMFP-coated targets efficiently triggered antibody-mediated clearing effector mechanisms. When assessed in a P18-primed mouse tumor model, therapy performed with an anti-huCD20 BMFP significantly led to increased survival and total cancer remission in some animals. These results indicate that BMFPs could represent potent and useful therapeutic molecules to treat a number of diseases.

Role of Rituximab in the Treatment of Pemphigus Vulgaris: Patient Selection and Acceptability

Anti-CD20 monoclonal antibody rituximab is an approved adjuvant treatment, in combination with oral corticosteroids, for patients with pemphigus vulgaris, a severe and potentially life-threatening autoimmune blistering skin disorder. Updated approaches to the management of pemphigus vulgaris support rituximab as a first-line adjuvant treatment to induce remission early in the course of disease; however, its feasibility in the clinical setting is often reduced by a series of limitations, including high cost of this biological drug, physician and patient concern for the risk of adverse reactions, and uncertainty regarding the optimum dosing and schedule of administration. The standard approved rituximab dosages, which are derived from lymphoma protocols, have been recognized to exceed the effective dose required for inducing B cell depletion, since the B cell burden in pemphigus vulgaris is much lower than in lymphoproliferative disorders. To overcome these limitations, recent research has investigated alternative regimens of rituximab, using lower doses of the drug. Moreover, differences in patient and disease characteristics that are highlighted in the literature strongly suggest that therapy should be tailored individually on a case-by-case basis: personalized treatment schedules may be necessary to optimize response to treatment and tolerability in different subjects, with the possibility of repeated infusions for severe forms and in case of relapse. Finally, low-dose regimens of rituximab were suggested to be favorable during the COVID-19 pandemic by providing a lesser degree of immune cell depletion while retaining a sufficient response. In conclusion, the current literature suggests that lower-dose regimens of rituximab are not only tolerable and cost-effective but may also be associated with a positive response in pemphigus vulgaris, comparable to that achieved with higher doses especially in early disease. Further evidence from rigorous clinical trials will be required to optimize lower-dose regimens of RTX and establish their position within the treatment scenario of pemphigus vulgaris.

Maintained partial protection against Streptococcus pneumoniae despite B-cell depletion in mice vaccinated with a pneumococcal glycoconjugate vaccine

OBJECTIVES

Anti-CD20 monoclonal antibody therapy rapidly depletes > 95% of CD20⁺ B cells from the circulation. B-cell depletion is an effective treatment for autoimmune disease and B-cell malignancies but also increases the risk of respiratory tract infections. This effect on adaptive immunity could be countered by vaccination. We have used mouse models to investigate the effects of B-cell depletion on pneumococcal vaccination, including protection against infection and timing of vaccination in relation to B-cell depletion.

METHODS

C57BL/6 female mice were B-cell depleted using anti-CD20 antibody and immunized with two doses of Prevnar-13 vaccine either before or after anti-CD20 treatment. B-cell repertoire and Streptococcus pneumoniae-specific IgG levels were measured using whole-cell ELISA and flow cytometry antibody-binding assay. Protection induced by vaccination was assessed by challenging the mice using a S. pneumoniae pneumonia model.

RESULTS

Antibody responses to S. pneumoniae were largely preserved in mice B-cell depleted after vaccination resulting in full protection against pneumococcal infections. In contrast, mice vaccinated with Prevnar-13 while B cells were depleted (with > 90% reduction in B-cell numbers) had decreased circulating anti-S. pneumoniae IgG and IgM levels (measured using ELISA and flow cytometry antibody binding assays). However, some antibody responses were maintained, and, although vaccine-induced protection against S. pneumoniae infection was impaired, septicaemia was still prevented in 50% of challenged mice.

CONCLUSIONS

This study showed that although vaccine efficacy during periods of profound B-cell depletion was impaired some protective efficacy was preserved, suggesting that vaccination remains beneficial.

Nanomedicines in B cell-targeting therapies

B cells play multiple roles in immune responses related to autoimmune diseases as well as different types of cancers. As such, strategies focused on B cell targeting attracted wide interest and developed intensively. There are several common mechanisms various B cell targeting therapies have relied on, including direct B cell depletion, modulation of B cell antigen receptor (BCR) signaling, targeting B cell survival factors, targeting the B cell and T cell costimulation, and immune checkpoint blockade. Nanocarriers, used as drug delivery vehicles, possess numerous advantages to low molecular weight drugs, reducing drug toxicity, enhancing blood circulation time, as well as augmenting targeting efficacy and improving therapeutic effect. Herein, we review the commonly used targets involved in B cell targeting approaches and the utilization of various nanocarriers as B cell-targeted delivery vehicles. STATEMENT OF SIGNIFICANCE: As B cells are engaged significantly in the development of many kinds of diseases, utilization of nanomedicines in B cell depletion therapies have been rapidly developed. Although numerous studies focused on B cell targeting have already been done, there are still various potential receptors awaiting further investigation. This review summarizes the most relevant studies that utilized nanotechnologies associated with different B cell depletion approaches, providing a useful tool for selection of receptors, agents and/or nanocarriers matching specific diseases. Along with uncovering new targets in the function map of B cells, there will be a growing number of candidates that can benefit from nanoscale drug delivery.

Comprehensive phenotyping of human peripheral blood B lymphocytes in pathological conditions

Several diseases are associated with alterations of the B-cell compartment. Knowing how to correctly identify by flow cytometry the distribution of B-cell populations in the peripheral blood is important to help in the early diagnosis. In the accompanying article we describe how to identify the different B-cell subsets in the peripheral blood of healthy donors. Here we show a few examples of diseases that cause dysregulation of the B-cell compartment.

Non Hodgkin lymphoma in Lebanon: a retrospective epidemiological study between 1984 and 2019

BACKGROUND

Lymphomas are ranked as the fifth most common cancer in Lebanon. There is concern about the need of information regarding the prevalence of lymphoid neoplasm particularly Non-Hodgkin lymphoma (NHL) subtypes in the Lebanese population. This study intended to establish a descriptive status of NHL histological subtypes distribution in Lebanon thus identifying the most common types, knowing that the literature is poor regarding the distribution of lymphoid malignancies particularly NHLs in Lebanon.

METHODS

A bicenter retrospective descriptive study was performed. Patients aged above 18, diagnosed with NHL between January 1984 and March 2019 and registered in two Lebanese Medical centers were included in this study; 699 medical files were reviewed and the baseline characteristics of the disease were collected. Histological classification was based on the Working Formulation (WF) and World Health Organization (WHO) classification systems, whereas staging was based on the Ann Arbor system. Disease status was monitored with imaging studies.

RESULTS

The mean age at diagnosis was 53.52 ± 17.46 years in the studied population, with 380 (54.4%) males and 319 (45.6%) females. B-cell lymphoma (BCL) accounted for 86.3% while T-cell neoplasms accounted for 13.7%. The most common subtype was diffuse large B-cell lymphoma (DLBCL) (54%) followed by follicular lymphoma (FL) (17.2%). Mantle cell lymphoma (MCL) represented 3% of all BCL and small lymphocytic lymphoma (SLL) comprised less than 2%. Mucosa-associated lymphoid tissue (MALT) and Burkitt's lymphomas represented 3 and 1.7% respectively. 36.5% of the patients had extranodal disease at diagnosis. High-grade tumor represented 80.1% with 33.1% stage IV disease.

CONCLUSION

These observations indicate that the epidemiological patterns of NHLs in Lebanon were comparable to Western countries. Aggressive lymphomas account for the majority of NHLs in Lebanon.

Immune inactivation of anti-simian immunodeficiency virus chimeric antigen receptor T cells in rhesus macaques

Chimeric antigen receptor (CAR) T cell therapies are being investigated as potential HIV cures and designed to target HIV reservoirs. Monoclonal antibodies (mAbs) targeting the simian immunodeficiency virus (SIV) envelope allowed us to investigate the potency of single-chain variable fragment (scFv)-based anti-SIV CAR T cells. In vitro, CAR T cells expressing the scFv to both the variable loop 1 (V1) or V3 of the SIV envelope were highly potent at eliminating SIV-infected T cells. However, in preclinical studies, in vivo infusion of these CAR T cells in rhesus macaques (RMs) resulted in lack of expansion and no detectable in vivo antiviral activity. Injection of envelope-expressing antigen-presenting cells (APCs) 1 week post-CAR T cell infusion also failed to stimulate CAR T cell expansion in vivo. To investigate this in vitro versus in vivo discrepancy, we examined host immune responses directed at CAR T cells. A humoral immune response against the CAR scFv was detected post-infusion of the anti-SIV CAR T cells; anti-SIV IgG antibodies present in plasma of SIV-infected animals were associated with inhibited CAR T cell effector functions. These data indicate that lack of in vivo expansion and efficacy of CAR T cells might be due to antibodies blocking the interaction between the CAR scFv and its epitope.

The future of antibody therapy in chronic lymphocytic leukemia

INTRODUCTION

Outcomes in chronic lymphocytic leukemia (CLL) have been dramatically improved with the addition of anti-CD20 antibodies to chemotherapy, defining a new standard of care for many years. More recently, therapies targeting fundamental signaling and anti-apoptotic pathways within the CLL cell have demonstrated dramatic clinical responses, including in patients with high-risk prognostic markers, thus emerging as preferred therapy for many patients. While the addition of anti-CD20 antibodies to traditional chemotherapy resulted in significant improvements in outcomes, the role of monoclonal antibodies in the era of targeted agents remains an active area of investigation. Furthermore, since the advent of next-generation anti-CD20 antibodies, the role of specific anti-CD20 antibodies remains an open question.

AREAS COVERED

In this review, we highlight the important role that anti-CD20 antibody therapy has had in the field of CLL, both when used with chemotherapy and in combination with targeted therapy, as well as the current studies that are further exploring this treatment paradigm in the modern era.

EXPERT OPINION

While anti-CD20 antibodies have played a pivotal role in the treatment of CLL, additional studies will be required to determine the optimal application of these therapies in combination with targeted therapy.

Flow cytometric myeloma measurable residual disease testing in the era of targeted therapies

Therapies in myeloma are rapidly advancing with a host of new targeted therapies coming to market. While these drugs offer significant survival benefits and better side-effect profiles compared with conventional chemotherapeutics, they raise significant difficulties in monitoring post-therapy disease status by flow cytometry due to assay interference and/or selection of phenotypically different sub-clones. The principal culprit, anti-CD38 monoclonal antibodies, limits the ability to detect plasma cells based on classical CD38/CD45 gating. Other markers, such as CD138, are known to be suboptimal by flow cytometry. Various techniques have been proposed to overcome this problem. The most promising of these techniques has been the marker VS38c, a monoclonal antibody targeting an endoplasmic reticulum protein which has shown high sensitivity for plasma cells. Alternative techniques for gating plasma cells, while variably effective in the near term are already the subject of several targeted therapies rendering their usefulness limited in the longer term. Likewise, future targets of these therapies may render present aberrancy markers ineffective in MRD testing. These therapies pose challenges that must be overcome with new markers and novel panels in order for flow cytometric MRD testing to remain relevant.

Targeting Immune Modulators in Glioma While Avoiding Autoimmune Conditions

Communication signals and signaling pathways are often studied in different physiological systems. However, it has become abundantly clear that the immune system is not self-regulated, but functions in close association with the nervous system. The neural-immune interface is complex; its balance determines cancer progression, as well as autoimmune disorders. Immunotherapy remains a promising approach in the context of glioblastoma multiforme (GBM). The primary obstacle to finding effective therapies is the potent immunosuppression induced by GBM. Anti-inflammatory cytokines, induction of regulatory T cells, and the expression of immune checkpoint molecules are the key mediators for immunosuppression in the tumor microenvironment. Immune checkpoint molecules are ligand-receptor pairs that exert inhibitory or stimulatory effects on immune responses. In the past decade, they have been extensively studied in preclinical and clinical trials in diseases such as cancer or autoimmune diseases in which the immune system has failed to maintain homeostasis. In this review, we will discuss promising immune-modulatory targets that are in the focus of current clinical research in glioblastoma, but are also in the precarious position of potentially becoming starting points for the development of autoimmune diseases like multiple sclerosis.

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.

Efficacy and safety of new anti-CD20 monoclonal antibodies versus rituximab for induction therapy of CD20+ B-cell non-Hodgkin lymphomas: a systematic review and meta-analysis

Rituximab combined with chemotherapy is the first-line induction therapy of CD20 positive B-cell non-Hodgkin lymphomas (CD20+ B-NHL). Recently new anti-CD20 monoclonal antibodies (mAbs) have been developed, but their efficacy and safety compared with rituximab are still controversial. We searched MEDLINE, Embase, and Cochrane Library for eligible randomized controlled trials (RCTs) that compared new anti-CD20 mAbs with rituximab in induction therapy of B-NHL. The primary outcomes are progression-free survival (PFS) and overall survival (OS), additional outcomes include event-free survival (EFS), disease-free survival (DFS), overall response rate (ORR), complete response rate (CRR) and incidences of adverse events (AEs). Time-to-event data were pooled as hazard ratios (HRs) using the generic inverse-variance method and dichotomous outcomes were pooled as odds ratios (ORs) using the Mantel-Haenszel method with their respective 95% confidence interval (CI). Eleven RCTs comprising 5261 patients with CD20+ B-NHL were included. Compared with rituximab, obinutuzumab significantly prolonged PFS (HR 0.84, 95% CI 0.73-0.96, P = 0.01), had no improvement on OS, ORR, and CRR, but increased the incidences of serious AEs (OR 1.29, 95% CI 1.13-1.48, P < 0.001). Ofatumumab was inferior to rituximab in consideration of ORR (OR 0.73, 95% CI 0.55-0.96, P = 0.02), and had no significant differences with rituximab in regard to PFS, OS and CRR. 131I-tositumomab yielded similar PFS, OS, ORR and CRR with rituximab. 90Y-ibritumomab tiuxetan increased ORR (OR 3.07, 95% CI 1.47-6.43, P = 0.003), but did not improve PFS, DFS, OS and CRR compared with rituximab. In conclusion, compared with rituximab in induction therapy of CD20+ B-NHL, obinutuzumab significantly improves PFS but with higher incidence of AEs, ofatumumab decreases ORR, 90Y-ibritumomab tiuxetan increases ORR.