The biological activity of human CD20 monoclonal antibodies is linked to unique epitopes on CD20

Cancer therapy with antibodies

The greatest challenge in cancer therapy is to eradicate cancer cells with minimal damage to normal cells. Targeted therapy has been developed to meet that challenge, showing a substantially increased therapeutic index compared with conventional cancer therapies. Antibodies are important members of the family of targeted therapeutic agents because of their extraordinarily high specificity to the target antigens. Therapeutic antibodies use a range of mechanisms that directly or indirectly kill the cancer cells. Early antibodies were developed to directly antagonize targets on cancer cells. This was followed by advancements in linker technologies that allowed the production of antibody-drug conjugates (ADCs) that guide cytotoxic payloads to the cancer cells. Improvement in our understanding of the biology of T cells led to the production of immune checkpoint-inhibiting antibodies that indirectly kill the cancer cells through activation of the T cells. Even more recently, bispecific antibodies were synthetically designed to redirect the T cells of a patient to kill the cancer cells. In this Review, we summarize the different approaches used by therapeutic antibodies to target cancer cells. We discuss their mechanisms of action, the structural basis for target specificity, clinical applications and the ongoing research to improve efficacy and reduce toxicity.

Different lymphocyte counts of multiple sclerosis patients treated with ofatumumab and ocrelizumab: A retrospective observational study

Introduction

Patients with Multiple Sclerosis (pwMS) treated with anti-CD20 (cluster of differentiation) monoclonal antibodies (mAbs) such as ocrelizumab (OCR) and ofatumumab (OFA) show a reduction mainly of B-lymphocytes, but also other lymphocyte subsets can be affected by these treatments. There is limited data on differences between lymphocyte subset counts of pwMS after treatment initiation with OCR or OFA.

Objective

To compare lymphocyte subset counts after treatment initiation in pwMS treated with OCR and OFA.

Methods

We analyzed 22 pwMS initiated on OFA and 56 sex-, age- and MS course matched pwMS initiated on OCR from 2 prospectively collected observational MS databases (Bern [n: OFA 14, OCR 44] and Vienna [n: OFA 8, OCR 12]) statistically comparing lymphocyte subset counts (Mann Whitney Test).

Results

We found that pwMS treated with OCR showed a stronger reduction of CD20 B-lymphocytes (P = .001), and a trend towards lower counts of CD8+ T cells (P = .056) compared to pwMS treated with OFA, whereas reduction of total lymphocyte, CD4+ lymphocyte and NK cell count was equally distributed between both treatments.

Conclusion

Different effects on lymphocyte subpopulations appear to be present in pwMS after treatment initiation with different anti-CD20 mAbs. Further studies are needed to determine potential effects on anti-CD20 treatment efficacy as well as treatment associated risks such as failed vaccinations and infections.

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.

Baseline immunoglobulin G and immune function in non-Hodgkin lymphoma: a retrospective analysis

Introduction

Non-Hodgkin's lymphoma (NHL) encompasses a diverse group of lymphoma subtypes with a wide range in disease course. Previous studies show that hypogammaglobulinemia in treatment-naïve patients is associated with poorer survival in high grade B-cell non-Hodgkin's lymphomas, though it is not known how this applies across all B-cell lymphoid malignancies.

Methods

We conducted a retrospective study of immunoglobulin levels and clinical outcomes including survival, hospitalization, and infection rates in patients diagnosed with B-cell non-Hodgkin lymphomas of all grades at our institution.

Results

Two-hundred twenty-three adults (aged = 18 years) with available pre-treatment IgG levels were selected, with hypogammaglobulinemia defined as IgG< 500 mg/mL. For this analysis, we grouped DLBCL (n=90), Primary CNS (n=5), and Burkitt lymphoma (n=1) together as high-grade, while CLL (n=52), mantle cell (n=20), marginal zone (n=25), follicular (n=21), and Waldenstrom macroglobulinemia (n=5) were low-grade. The incidence of hypogammaglobulinemia in our cohort of both high and low-grade lymphoma patients was 13.5% (n=30). Across all NHL subtypes, individuals with baseline IgG< 500 mg/dL showed an increased rate of hospitalization (4.453, CI: 1.955-10.54, p= 0.0005) and higher mortality (3.325, CI: 1.258, 8.491, p= 0.013), yet no association in number of infections when compared with those with IgG=500 mg/dL. There was a higher hospitalization rate (3.237, CI: 1.77-6.051, p=0.0017) in those with high-grade lymphoma with hypogammaglobulinemia when compared with low-grade. There was no statistically significant difference in individuals who were alive after three years in those with baseline IgG<500 mg/dL.

Discussion

Our study is the first to analyze incidence of hypogammaglobulinemia at the time of diagnosis of NHL as a potential biomarker of interest for future outcomes including hospitalization and infection.

Key characteristics of anti-CD20 monoclonal antibodies and clinical implications for multiple sclerosis treatment

The recent success of anti-CD20 monoclonal antibody therapies in the treatment of multiple sclerosis (MS) has highlighted the role of B cells in the pathogenesis of MS. In people with MS, the inflammatory characteristics of B-cell activity are elevated, leading to increased pro-inflammatory cytokine release, diminished anti-inflammatory cytokine production and an accumulation of pathogenic B cells in the cerebrospinal fluid. Rituximab, ocrelizumab, ofatumumab, ublituximab and BCD-132 are anti-CD20 therapies that are either undergoing clinical development, or have been approved, for the treatment of MS. Despite CD20 being a common target for these therapies, differences have been reported in their mechanistic, pharmacological and clinical characteristics, which may have substantial clinical implications. This narrative review explores key characteristics of these therapies. By using clinical trial data and real-world evidence, we discuss their mechanisms of action, routes of administration, efficacy (in relation to B-cell kinetics), safety, tolerability and convenience of use. Clinicians, alongside patients and their families, should consider the aspects discussed in this review as part of shared decision-making discussions to improve outcomes and health-related quality of life for people living with MS.

Drugs Targeting CD20 in Multiple Sclerosis: Pharmacology, Efficacy, Safety, and Tolerability

Currently, there are four monoclonal antibodies (mAbs) that target the cluster of differentiation (CD) 20 receptor available to treat multiple sclerosis (MS): rituximab, ocrelizumab, ofatumumab, and ublituximab. B-cell depletion therapy has changed the therapeutic landscape of MS through robust efficacy on clinical manifestations and MRI lesion activity, and the currently available anti-CD20 mAb therapies for use in MS are a cornerstone of highly effective disease-modifying treatment. Ocrelizumab is currently the only therapy with regulatory approval for primary progressive MS. There are currently few data regarding the relative efficacy of these therapies, though several clinical trials are ongoing. Safety concerns applicable to this class of therapeutics relate primarily to immunogenicity and mechanism of action, and include infusion-related or injection-related reactions, development of hypogammaglobulinemia (leading to increased infection and malignancy risk), and decreased vaccine response. Exploration of alternative dose/dosing schedules might be an effective strategy for mitigating these risks. Future development of biosimilar medications might make these therapies more readily available. Although anti-CD20 mAb therapies have led to significant improvements in disease outcomes, CNS-penetrant therapies are still needed to more effectively address the compartmentalized inflammation thought to play an important role in disability progression.

Ofatumumab in Rituximab-Resistant and Rituximab-Intolerant Patients With Primary Membranous Nephropathy: A Case Series

RATIONALE & OBJECTIVE

Rituximab is the first-choice therapy for patients with primary membranous nephropathy (MN) and nephrotic syndrome. However, approximately 30% of patients are treatment-resistant or become treatment-intolerant with hypersensitivity reactions upon repeated drug exposures. We aimed to assess whether ofatumumab, a fully human second-generation anti-CD20 antibody, could be a valuable alternative to rituximab in this population.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

7 rituximab-intolerant and 10 rituximab-resistant patients with MN who consented to receive ofatumumab (50-300mg, single intravenous infusion) and were followed at the nephrology unit of Azienda Socio-Sanitaria Territoriale Papa Giovanni XXIII (Bergamo, Italy) between September 2015 and January 2019.

FINDINGS

Over a median (IQR) follow-up of 5.0 (3.0-9.8) months, all 7 rituximab-intolerant and 3 of the 10 rituximab-resistant patients exhibited complete (proteinuria<0.3g/d) or partial (proteinuria<3.5g/d with≥50% reduction vs baseline) remission of nephrotic syndrome. Circulating B cells were similarly depleted in all patients by 1 week, and serum anti-phospholipase A2 receptor antibody concentrations decreased to<2.7 relative units/mL in 3 of 4 rituximab-intolerant and 4 of 8 rituximab-resistant patients with phospholipase A2 receptor-related disease. Ofatumumab significantly reduced 24-hour urinary protein and immunoglobulin G excretion and increased serum albumin and immunoglobulin G levels. These effects were greater in rituximab-intolerant than in rituximab-resistant patients. Measured glomerular filtration rate significantly increased by an average of 13.4% at 24 months compared with baseline (P=0.036) among all patients in the series. There were 14 nonserious infusion-related adverse events in 9 patients that recovered with temporary infusion interruption.

LIMITATIONS

Retrospective design, limited number of patients.

CONCLUSIONS

Ofatumumab may represent an effective and safe treatment for rituximab-intolerant cases of MN. Larger prospective studies will be needed to validate these preliminary findings and explore the effectiveness of other second-generation anti-CD20 antibodies in this clinical setting.

PLAIN-LANGUAGE SUMMARY

Primary membranous nephropathy (MN) is one of the most frequent causes of nephrotic syndrome (NS) in adults. In this case series, we explored the efficacy of ofatumumab, a fully human second-generation anti-CD20 antibody, in 17 patients with MN and NS who were intolerant or unresponsive to rituximab. All 7 rituximab-intolerant patients exhibited complete or partial clinical remission, compared with only 3 of the 10 rituximab-resistant patients. Autoantibody levels decreased in all patients with phospholipase A2 receptor-related disease. Ofatumumab achieved a significant reduction in urinary protein and immunoglobulin G excretion while increasing serum albumin and immunoglobulin G levels. Ofatumumab may be a promising option for patients with MN who are rituximab-intolerant. Further investigations are warranted to validate these preliminary findings.

Determination of the clinical relevance of donor epitope-specific HLA-antibodies in kidney transplantation

In kidney transplantation, survival rates are still partly impaired due to the deleterious effects of donor specific HLA antibodies (DSA). However, not all luminex-defined DSA appear to be clinically relevant. Further analysis of DSA recognizing polymorphic amino acid configurations, called eplets or functional epitopes, might improve the discrimination between clinically relevant vs. irrelevant HLA antibodies. To evaluate which donor epitope-specific HLA antibodies (DESAs) are clinically important in kidney graft survival, relevant and irrelevant DESAs were discerned in a Dutch cohort of 4690 patients using Kaplan-Meier analysis and tested in a cox proportional hazard (CPH) model including nonimmunological variables. Pre-transplant DESAs were detected in 439 patients (9.4%). The presence of certain clinically relevant DESAs was significantly associated with increased risk on graft loss in deceased donor transplantations (p < 0.0001). The antibodies recognized six epitopes of HLA Class I, 3 of HLA-DR, and 1 of HLA-DQ, and most antibodies were directed to HLA-B (47%). Fifty-three patients (69.7%) had DESA against one donor epitope (range 1-5). Long-term graft survival rate in patients with clinically relevant DESA was 32%, rendering DESA a superior parameter to classical DSA (60%). In the CPH model, the hazard ratio (95% CI) of clinically relevant DESAs was 2.45 (1.84-3.25) in deceased donation, and 2.22 (1.25-3.95) in living donation. In conclusion, the developed model shows the deleterious effect of clinically relevant DESAs on graft outcome which outperformed traditional DSA-based risk analysis on antigen level.

Revolutionizing cancer immunotherapy: unleashing the potential of bispecific antibodies for targeted treatment

Recent progressions in immunotherapy have transformed cancer treatment, providing a promising strategy that activates the immune system of the patient to find and eliminate cancerous cells. Bispecific antibodies, which engage two separate antigens or one antigen with two distinct epitopes, are of tremendous concern in immunotherapy. The bi-targeting idea enabled by bispecific antibodies (BsAbs) is especially attractive from a medical standpoint since most diseases are complex, involving several receptors, ligands, and signaling pathways. Several research look into the processes in which BsAbs identify different cancer targets such angiogenesis, reproduction, metastasis, and immune regulation. By rerouting cells or altering other pathways, the bispecific proteins perform effector activities in addition to those of natural antibodies. This opens up a wide range of clinical applications and helps patients with resistant tumors respond better to medication. Yet, further study is necessary to identify the best conditions where to use these medications for treating tumor, their appropriate combination partners, and methods to reduce toxicity. In this review, we provide insights into the BsAb format classification based on their composition and symmetry, as well as the delivery mode, focus on the action mechanism of the molecule, and discuss the challenges and future perspectives in BsAb development.

The Development of Ofatumumab, a Fully Human Anti-CD20 Monoclonal Antibody for Practical Use in Relapsing Multiple Sclerosis Treatment

The importance of B cells in multiple sclerosis (MS) has been demonstrated through the advent of B-cell-depleting anti-CD20 antibody therapies. Ofatumumab is the first fully human anti-CD20 monoclonal antibody (mAb) developed and tested for subcutaneous (SC) self-administration at monthly doses of 20 mg, and has been approved in the US, UK, EU, and other regions and countries worldwide for the treatment of relapsing MS. The development goal of ofatumumab was to obtain a highly efficacious anti-CD20 therapy, with a safety and tolerability profile that allows for self-administration by MS patients at home and a positive benefit-risk balance for use in the broad relapsing MS population. This development goal was enabled by the unique binding site, higher affinity to B cells, and higher potency of ofatumumab compared to previous anti-CD20 mAbs; these properties of ofatumumab facilitate rapid B-cell depletion and maintenance with a low dose at a low injection volume (20 mg/0.4 ml). The high potency in turn enables the selective targeting of B cells that reside in the lymphatic system via subcutaneous (SC) administration. Through a comprehensive dose-finding program in two phase 2 studies (one intravenous and one SC) and model simulations, it was found that safety and tolerability can be further improved, and the risk of systemic injection-related reactions (IRRs) minimized, by avoiding doses ≥ 30 mg, and by reaching initial and rapid B-cell depletion via stepwise weekly administration of ofatumumab at Weeks 0, 1, and 2 (instead of a single high dose). Once near-complete B-cell depletion is reached, it can be maintained by monthly doses of 20 mg/0.4 ml. Indeed, in phase 3 trials (ASCLEPIOS I/II), rapid and sustained near-complete B-cell depletion (largely independent of body weight, race and other factors) was observed with this dosing regimen, which resulted in superior efficacy of ofatumumab versus teriflunomide on relapse rates, disability worsening, neuronal injury (serum neurofilament light chain), and imaging outcomes. Likely due to its fully human nature, ofatumumab has a low immunogenic risk profile-only 2 of 914 patients receiving ofatumumab in ASCLEPIOS I/II developed anti-drug antibodies-and this may also underlie the infrequent IRRs (20% with ofatumumab vs. 15% with the placebo injection in the teriflunomide arm) that were mostly (99.8%) mild to moderate in severity. The overall rates of infections and serious infections in patients treated with ofatumumab were similar to those in patients treated with teriflunomide (51.6% vs. 52.7% and 2.5% vs. 1.8%, respectively). The benefit-risk profile of ofatumumab was favorable compared to teriflunomide in the broad RMS population, and also in the predefined subgroups of both recently diagnosed and/or treatment-naïve patients, as well as previously disease-modifying therapy-treated patients. Interim data from the ongoing extension study (ALITHIOS) have shown that long-term treatment with ofatumumab up to 4 years is well-tolerated in RMS patients, with no new safety risks identified. In parallel to the phase 3 trials in which SC administration was carried out with a pre-filled syringe, an autoinjector pen for more convenient self-administration of the ofatumumab 20 mg dose was developed and is available for use in clinical practice.

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.

B cell depletion therapies in autoimmune diseases: Monoclonal antibodies or chimeric antigen receptor-based therapy?

Immune system detects foreign pathogens, distinguishes them from self-antigens and responds to defend human body. When this self-tolerance is disrupted, the overactive immune system attacks healthy tissues or organs and the autoimmune diseases develop. B cells and plasma cells contribute a lot to pathogenesis and persistence of autoimmune diseases in both autoantibody-dependent and autoantibody-independent ways. Accumulating data indicates that treatments aiming to eliminate antibody-secreting cells (B cells or plasma cells) are effective in a wide spectrum of autoimmune diseases. Monoclonal antibodies (mAbs) deplete B cell lineage or plasma cells by signaling disruption, complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). Engineered-T cells armed with chimeric antigen receptors (CARs) have been adopted from field of hematological malignancies as a method to eliminate B cells or plasma cells. In this review, we update our understanding of B cell depletion therapies in autoimmune diseases, review the mechanism, efficacy, safety and application of monoclonal antibodies and CAR-based immunotherapies, and discuss the strengths and weaknesses of these treatment options for patients.

Anti-CD20 therapies in multiple sclerosis: From pathology to the clinic

The immune system plays a significant role in multiple sclerosis. While MS was historically thought to be T cell-mediated, multiple pieces of evidence now support the view that B cells are essential players in multiple sclerosis pathogenic processes. High-efficacy disease-modifying therapies that target the immune system have emerged over the past two decades. Anti-CD20 monoclonal antibodies selectively deplete CD20+ B and CD20+ T cells and efficiently suppress inflammatory disease activity. These monotherapies prevent relapses, reduce new or active magnetic resonance imaging brain lesions, and lessen disability progression in patients with relapsing multiple sclerosis. Rituximab, ocrelizumab, and ofatumumab are currently used in clinical practice, while phase III clinical trials for ublituximab have been recently completed. In this review, we compare the four anti-CD20 antibodies in terms of their mechanisms of action, routes of administration, immunological targets, and pharmacokinetic properties. A deeper understanding of the individual properties of these molecules in relation to their efficacy and safety profiles is critical for their use in clinical practice.

Humoral Immune Responses to P. falciparum Circumsporozoite Protein (Pfcsp) Induced by the RTS, S Vaccine - Current Update

Malaria vaccines targeting the circumsporozoite protein (CSP) of the P. falciparum parasite have been overall relatively promising. RTS, S is a pre-erythrocytic recombinant protein-based malaria vaccine that targets CSP. RTS, S effectiveness shows some limited success regardless of its 58% efficacy for severe disease. P. falciparum circumsporozoite protein (Pfcsp) has stood to be the main candidate protein for most pre-erythrocytic stage vaccines. Studies on the structural and biophysical characteristics of antibodies specific to CSP (anti-CSP) are underway to achieve fine specificity with the CSP polymorphic regions. More recent studies have proposed the use of different kinds of monoclonal antibodies, the use of appropriate adjuvants, ideal vaccination dose and frequency, and improved targeting of particular epitopes for the robust production of functional antibodies and high complement-fixing activity as other potential methods for achieving long-lasting RTS, S. This review highlights recent findings regarding humoral immune responses to CSP elicited by RTS, S vaccine.

The diverse landscape of dermatologic toxicities of non-immune checkpoint inhibitor monoclonal antibody-based cancer therapy

BACKGROUND

Since their first approval 25 years ago, monoclonal antibodies (mAbs) have become important targeted cancer therapeutics. However, dermatologic toxicities associated with non-immune checkpoint inhibitor (non-ICI) mAbs may complicate the course of cancer treatment. Data on the incidence and types of these reactions are limited.

METHODS

A comprehensive review was conducted on dermatologic toxicities associated with different classes of non-ICI mAbs approved for treatment of solid tumors and hematologic malignancies. The review included prospective Phase 1, 2, and 3 clinical trials; retrospective literature reviews; systematic reviews/meta-analyses; and case series/reports.

RESULTS

Dermatologic toxicities were associated with several types of non-ICI mAbs. Inflammatory reactions were the most common dermatologic toxicities, manifesting as maculopapular, urticarial, papulopustular/acneiform, and lichenoid/interface cutaneous adverse events (cAEs) with non-ICI mAbs. Immunobullous reactions were rare and a subset of non-ICI mAbs were associated with the development of vitiligo cAEs.

CONCLUSION

Dermatologic toxicities of non-ICI mAbs are diverse and mostly limited to inflammatory reactions. Awareness of the spectrum of the histopathologic patterns of cAE from non-ICI mAbs therapy is critical in the era of oncodermatology and oncodermatopathology.

B cell depletion and inhibition in systemic lupus erythematosus

INTRODUCTION

Systemic lupus erythematosus (SLE) is characterized by autoantibody expression and aberrant autoreactive B cells contribute to disease progression; therefore, B cell inhibition has been an attractive target for novel therapies. However, after more than two decades of research and over 40 randomized clinical trials, only one such therapy, belimumab, has been approved for use in SLE.

AREAS COVERED

In this review, we discuss the evidence for B cell-targeted therapies in SLE and lupus nephritis. Belimumab has been successful in several large clinical trials and is approved in several countries for use in SLE and lupus nephritis. Despite a lack of supporting phase III evidence, rituximab is used off-label in SLE. Several other B cell-targeted therapies have failed to meet their end points in late-stage clinical trials. Successful phase II trials have recently been reported for obinutuzumab and telitacicept with larger confirmatory trials currently underway.

EXPERT OPINION

Refinements in pharmaceutical mechanisms of action, trial design, and patient selection have resulted in recent preliminary successes, offering renewed optimism for B-cell targeted therapeutics in SLE management.

Intravenous ofatumumab treatment of multiple sclerosis and related disorders: An observational study

BACKGROUND

Ofatumumab is an anti-CD20 monoclonal antibody approved for subcutaneous administration for the treatment of relapsing multiple sclerosis (MS), but intravenously administered ofatumumab has been investigated in a phase 2 trial and used off-label. The objective of the present study was to assess disease activity and side effects in relation to longer-term intravenous ofatumumab treatment of MS and related disorders.

METHODS

We conducted a retrospective study of patients treated off-label with intravenous ofatumumab for MS, neuromyelitis optica spectrum disease (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) at the Danish Multiple Sclerosis Center. Data was retrieved from the Danish Multiple Sclerosis Registry and through medical chart review.

RESULTS

Fifty patients were identified with a median treatment duration of 2.2 years. Annualized relapse rate decreased from 1.03 at baseline to 0.38 during ofatumumab treatment. At 24 months, the probability of having experienced a relapse was 55% and confirmed disability worsening 7%. Frequency of infusion-related reactions was 86% during the first infusion and 42% during the last infusion. Six experienced infections requiring hospitalization.

CONCLUSION

Our data indicate a reduction of relapse frequency, stabilization of disability worsening and an acceptable safety profile, although we observed a higher frequency of infusion reactions compared to data from other intravenously administered anti-CD20 monoclonal antibodies. The study supports a class effect of anti-CD20 monoclonal antibodies and the hypothesis that complement activation may be associated to a higher frequency of infusion related reactions.

Surgical, Dermatological and Morphopathological Considerations in the Diagnosis and Treatment of Cutaneous Lymphoproliferative Tumors, Primary CD4+

Primary cutaneous lymphomas are a heterogeneous group of T-cell (CTCL) and B-cell lymphomas (CBCL) developing in the skin and without signs of extracutaneous disease at the time of diagnosis. The term “primary small/medium CD4+ T-cell lymphoma” was changed to “primary small/medium cutaneous CD4+ lymphoproliferative disorder” due to its indolent clinical behavior and uncertain malignant potential. This paper presents a rare case of primary cutaneous lymphoma with small to medium CD4+ T-cells. A 37-year-old patient presented with a tumor in the frontal region that had occurred approximately 8–9 months earlier. The tumor had a diameter of about 8–9 mm, well demarcated macroscopically, it was round in shape, about 6–7 mm high, pink in color, firm in consistency and painless during palpation. Surgical excision of the tumor was performed with a margin of safety of 8 mm and deep to the level of the frontal muscle fascia. The histopathological examination supported the diagnosis of cutaneous lymphoproliferation with a nodular disposition in the reticular dermis and extension around the follicular epithelia and sweat glands, composed mainly of dispersed medium-large lymphocytes. Additional immunohistochemical examination was requested. Immunohistochemical examination confirmed the diagnosis of “primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder.” Patient monitoring was carried out through clinical dermatological controls at 3, 6, and 12 months. After one year, a cranio-cerebral MRI was performed. For the following 5 years, an annual dermatological examination accompanied by cranio-cerebral MRI, blood count, and pulmonary X-ray were recommended. Similarly to all solitary skin lesions, the prognosis is excellent in this case, the only treatment being surgical excision.

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.

Logic-gated antibody pairs that selectively act on cells co-expressing two antigens

The use of therapeutic monoclonal antibodies is constrained because single antigen targets often do not provide sufficient selectivity to distinguish diseased from healthy tissues. We present HexElect®, an approach to enhance the functional selectivity of therapeutic antibodies by making their activity dependent on clustering after binding to two different antigens expressed on the same target cell. lmmunoglobulin G (lgG)-mediated clustering of membrane receptors naturally occurs on cell surfaces to trigger complement- or cell-mediated effector functions or to initiate intracellular signaling. We engineer the Fc domains of two different lgG antibodies to suppress their individual homo-oligomerization while promoting their pairwise hetero-oligomerization after binding co-expressed antigens. We show that recruitment of complement component C1q to these hetero-oligomers leads to clustering-dependent activation of effector functions such as complement mediated killing of target cells or activation of cell surface receptors. HexElect allows selective antibody activity on target cells expressing unique, potentially unexplored combinations of surface antigens.

Antibody-mediated cell depletion therapies in multiple sclerosis

Development of disease-modifying therapies including monoclonal antibody (mAb)-based therapeutics for the treatment of multiple sclerosis (MS) has been extremely successful over the past decades. Most of the mAb-based therapies approved for MS deplete immune cell subsets and act through activation of cellular Fc-gamma receptors expressed by cytotoxic lymphocytes and phagocytes, resulting in antibody-dependent cellular cytotoxicity or by initiation of complement-mediated cytotoxicity. The therapeutic goal is to eliminate pathogenic immune cell components and to potentially foster the reconstitution of a new and healthy immune system. Ab-mediated immune cell depletion therapies include the CD52-targeting mAb alemtuzumab, CD20-specific therapeutics, and new Ab-based treatments which are currently being developed and tested in clinical trials. Here, we review recent developments in effector mechanisms and clinical applications of Ab-based cell depletion therapies, compare their immunological and clinical effects with the prototypic immune reconstitution treatment strategy, autologous hematopoietic stem cell transplantation, and discuss their potential to restore immunological tolerance and to achieve durable remission in people with MS.

Unmet Needs and Treatment of Relapsing-Remitting Multiple Sclerosis in Saudi Arabia: Focus on the Role of Ofatumumab

Treatment-pattern data suggest that some patients with multiple sclerosis (MS) in the Kingdom of Saudi Arabia (KSA) may not be receiving optimal treatment. A virtual meeting of ten expert Saudi neurologists, held on October 23, 2020, discussed unmet needs in relapsing-remitting MS (RRMS), and the role of ofatumumab as a suitable treatment in the KSA. Multiple unmet needs were identified: poor quality of life, with high rates of depression and anxiety; a negative impact of MS on work ability; treatment choices that may compromise efficacy for safety or vice versa; inconvenient or complex dosage regimens; and limited access to patient education and support. Early use of highly effective disease-modifying treatments (DMTs) results in better patient outcomes than starting with less effective treatments and downstream escalation, but this strategy may be underutilized in the KSA. B cells are important in MS pathogenesis, and treatments targeting these may improve clinical outcomes. Ofatumumab differs from other B cell-depleting therapies, being a fully human monoclonal antibody that binds to CD20 at a completely separate site from the epitope bound by ocrelizumab, and being administered by subcutaneous injection. When compared with teriflunomide in two randomized, phase 3 clinical trials in patients with RRMS, ofatumumab was associated with significant reductions in annualized relapse rates, rates of confirmed disability worsening, and active lesions on magnetic resonance imaging. The incidence of adverse events, including serious infections, was similar with the two treatments. Ofatumumab is a valuable first- or second-line treatment option for RRMS in the KSA, particularly for patients who would benefit from highly effective DMTs early in the disease course, and for those who prefer the convenience of self-injection. Future research will clarify the position of ofatumumab in RRMS treatment, and comparative cost data may support the broad inclusion of ofatumumab in formularies across the KSA.

Mass spectrometry-based multi-attribute method for mutation analysis in the early development of therapeutic proteins

The early intervention is essential, and later development cannot compensate for this initial generation of an antibody drug. Especially for sequence variants (SVs), should cause concern during the early bioprocess development. The advancement of bioprocess development is paralleled by development of state-of-the-art analytical methods that will provide further information. In the present study, a mass spectrometry (MS)-based multi-attribute method (MAM) was used to simultaneously monitor the SVs and other quality attributes in the early bioprocess development of ofatumumab, and a sequence variant (SV) was detected by a subunit-based MAM. Subsequently, the variant was further identified by MS/MS and confirmed by adding a synthetic peptide. Furthermore, the content of the SV was detected via DNA sequencing. The levels of the variant (T175A mutant) in the light chain were demonstrate to be nearly consistent at the DNA and protein levels, suggesting that the mutation may have negligible effect on both the transcriptional and translational levels. Collectively, these results indicate that broad-spectrum, rapid, and accurate platform such as MS-based MAM should be implemented to quality control for the early development of therapeutic proteins, it will also be important to establish an effective and integrated MAM to control SVs during therapeutic proteins development.

Ocrelizumab quantitation by liquid chromatography-tandem mass spectrometry

Introduction

Ocrelizumab is a monoclonal anti-CD20 antibody approved for the treatment of multiple sclerosis (MS). The clinical value of therapeutic drug monitoring (TDM) for this antibody in treatment of MS is unknown, and an adequately specific and precise quantitation method for ocrelizumab in patient serum could facilitate investigation. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based quantitation methods have been shown to have higher analytic specificity and precision than enzyme-linked immunosorbent assays.

Objectives

To establish and validate an LC-MS/MS-based quantitation method for ocrelizumab.

Methods

We present an LC-MS/MS-based quantitation method using immunocapture purification followed by trypsinization and analysis by a triple quadrupole mass analyzer obtaining results within the same day.

Results

We found that the ocrelizumab peptide GLEWVGAIYPGNGDTSYNQK (Q1/Q3 Quantifier ion: 723.683+/590.77 y112+ Qualifier ion: 723.683+/672.30 y122+) can be used for quantitation and thereby developed a method for quantifying ocrelizumab in human serum with a quantitation range of 1.56 to 200 µg/mL. The method was validated in accordance with EMA requirements in terms of selectivity, carry-over, lower limit of quantitation, calibration curve, accuracy, precision and matrix effect. Ocrelizumab serum concentrations were measured in three MS patients treated with ocrelizumab, immediately before and after ocrelizumab infusion, with additional sampling after 2, 4, 8 and 12 weeks. Measured serum concentrations of ocrelizumab showed expected values for both Cmax and drug half-life over the sampled time period.

Conclusion

We have established a reliable quantitation method for serum ocrelizumab that can be applied in clinical studies, facilitating the evaluation of ocrelizumab TDM in MS.

Monoclonal antibodies: new chance in the management of B-cell acute lymphoblastic leukemia

OBJECTIVES

This review aims to see the progress of several clinically-used monoclonal antibodies in treating ALL patients and how they improved patients' outcomes.

METHODS

We searched Web of Science, Elsevier and PubMed for relevant published studies, and summarized eligible evidence on the management of newly-diagnosed and relapsed or refractory ALL with monoclonal antibodies. Ongoing trials were identified from ClinicalTrials.gov.

RESULTS

Rituximab, an anti-CD20 monoclonal antibody, prolonged patients' complete remission duration and overall survival when combined with hyper-CVAD regimen. Another anti-CD20 monoclonal antibody, Ofatumumab, was reported to have similar benefits. Blinatumomab allows endogenous CD3-positive cytotoxic T cells to target and eliminate CD19-positive blasts. FDA has approved its efficacy in patients with R/R B-ALL and eliminating minimal residual disease (MRD). It serves as a bridge to eradicate MRD before transplantation, and may also be a new choice for patients unable to undergo transplantation. An anti-CD22 monoclonal antibody named Inotuzumab Ozogamicin showed great improvement in patients' outcome, but its toxicity to liver is also worthy of our attention.

CONCLUSION

Monoclonal antibodies are proven to be a promising immunotherapeutic strategy to improve ALL patients' outcome in the long term. There's still a need for individualized treatment with effective and well-tolerated medicines.Trial registration: ClinicalTrials.gov identifier: NCT01363128.Trial registration: ClinicalTrials.gov identifier: NCT01466179.Trial registration: ClinicalTrials.gov identifier: NCT02013167.Trial registration: ClinicalTrials.gov identifier: NCT02000427.Trial registration: ClinicalTrials.gov identifier: NCT01564784.Trial registration: ClinicalTrials.gov identifier: NCT03677596.Trial registration: ClinicalTrials.gov identifier: NCT01363297.Trial registration: ClinicalTrials.gov identifier: NCT02981628.Trial registration: ClinicalTrials.gov identifier: NCT03094611.Trial registration: ClinicalTrials.gov identifier: NCT01371630.Trial registration: ClinicalTrials.gov identifier: NCT04224571.Trial registration: ClinicalTrials.gov identifier: NCT02458014.Trial registration: ClinicalTrials.gov identifier: NCT04546399.Trial registration: ClinicalTrials.gov identifier: NCT02879695.Trial registration: ClinicalTrials.gov identifier: NCT03913559.Trial registration: ClinicalTrials.gov identifier: NCT03441061.Trial registration: ClinicalTrials.gov identifier: NCT03739814.Trial registration: ClinicalTrials.gov identifier: NCT02877303.Trial registration: ClinicalTrials.gov identifier: NCT03698552.Trial registration: ClinicalTrials.gov identifier: NCT04601584.Trial registration: ClinicalTrials.gov identifier: NCT04684147.Trial registration: ClinicalTrials.gov identifier: NCT04681105.

A Method for the Elution of Anti-CD20 With an EDTA/Glycine Acid Solution for Accurate Immunophenotyping of B Lymphocytes Sensitized With Rituximab

OBJECTIVES

To assess the efficacy of a method to circumvent CD20-positive antigen masking by rituximab for flow cytometry analysis of B-cell malignancies in hematology patients.

METHODS

Mononuclear cells (MNCs) from 10 healthy individuals and 5 untreated patients with B-cell malignancies were sensitized with rituximab. Patients' diagnoses included chronic lymphocytic leukemia, hairy cell leukemia, and follicular lymphoma. MNCs were isolated by gradient density centrifugation. An EDTA/glycine acid (EGA) elution method was used to dissociate CD20-rituximab complexes; afterwards, CD20-positive immunoreactivity was assessed by flow cytometry. A saturation curve was built based on serial dilutions of rituximab. Median fluorescent intensities of CD20-positive signals were obtained before sensitization with rituximab and after its elution with EGA.

RESULTS

CD20-positive signals were not detectable by flow cytometry after rituximab sensitization of B cells. CD20-sensitized vs CD20-unsensitized, CD20-sensitized vs CD20-eluted, and CD20-eluted vs CD20-negative control (NC) MNC populations exhibited statistical differences (P = .001), while CD20-sensitized vs CD20-NC populations did not (P = .499), confirming CD20 antigen masking by rituximab.

CONCLUSIONS

Rituximab interfered with the flow cytometry protocol for CD20 determination on normal and neoplastic B cells. The EGA method efficiently eluted rituximab, allowing for accurate identification of CD20-positive B cells.

Physiological Considerations for Modeling in vivo Antibody-Target Interactions

The number of therapeutic antibodies in development pipelines is increasing rapidly. Despite superior success rates relative to small molecules, therapeutic antibodies still face many unique development challenges. There is often a translational gap from their high target affinity and specificity to the therapeutic effects. Tissue microenvironment and physiology critically influence antibody-target interactions contributing to apparent affinity alterations and dynamic target engagement. The full potential of therapeutic antibodies will be further realized by contextualizing antibody-target interactions under physiological conditions. Here we review how local physiology such as physical stress, biological fluid, and membrane characteristics could influence antibody-target association, dissociation, and apparent affinity. These physiological factors in the early development of therapeutic antibodies are valuable toward rational antibody engineering, preclinical candidate selection, and lead optimization.

Epitope Mapping of the Anti-CD20 Monoclonal Antibodies (C20Mab-11 and 2H7) Using HisMAP Method

CD20, which is expressed on B lymphocytes, has been studied as a therapeutic target for B cell lymphomas and autoimmune disorders. Identifying the binding epitopes of monoclonal antibodies (mAbs) can contribute to our understanding of their functions. We have previously developed an anti-CD20 mAb (clone C₂₀Mab-11) using a Cell-Based Immunization and Screening (CBIS) method. In this study, we aimed to determine the binding epitopes of anti-CD20 mAbs, such as C₂₀Mab-11 and 2H7, using the His-tag insertion for epitope mapping (HisMAP). The results showed that ₁₇₁-NPSE-₁₇₄ and ₁₆₈-EPANPSE-₁₇₄ in the second loop of CD20 were essential for C₂₀Mab-11 binding and 2H7 binding, respectively. Although we developed many mAbs that recognize conformational epitopes using the CBIS method, there are many difficulties in epitope mapping for these mAbs. HisMAP could be useful for determining the conformational epitopes of other mAbs against membrane proteins.

In-Vivo Induced CAR-T Cell for the Potential Breakthrough to Overcome the Barriers of Current CAR-T Cell Therapy

Chimeric antigen receptor T cell (CAR-T cell) therapy has shown impressive success in the treatment of hematological malignancies, but the systemic toxicity and complex manufacturing process of current autologous CAR-T cell therapy hinder its broader applications. Universal CAR-T cells have been developed to simplify the production process through isolation and editing of allogeneic T cells from healthy persons, but the allogeneic CAR-T cells have recently encountered safety concerns, and clinical trials have been halted by the FDA. Thus, there is an urgent need to seek new ways to overcome the barriers of current CAR-T cell therapy. In-vivo CAR-T cells induced by nanocarriers loaded with CAR-genes and gene-editing tools have shown efficiency for regressing leukemia and reducing systemic toxicity in a mouse model. The in-situ programming of autologous T-cells avoids the safety concerns of allogeneic T cells, and the manufacture of nanocarriers can be easily standardized. Therefore, the in-vivo induced CAR-T cells can potentially overcome the abovementioned limitations of current CAR-T cell therapy. Here, we provide a review on CAR structures, gene-editing tools, and gene delivery techniques applied in immunotherapy to help design and develop new in-vivo induced CAR-T cells.

The impact of anti-CD20-based therapy on hypogammaglobulinemia in patients with follicular lymphoma

Although treatment with anti-CD20 monoclonal antibodies (mAb) has improved outcomes in B-cell malignancies, it's associated with increased risk of hypogammaglobulinemia (HG). Our study aimed to determine the effects of anti-CD20 mAb on serum immunoglobulins (Ig) in follicular lymphoma (FL). Ig concentrations, infectious complications, and need for intravenous Ig were evaluated by level of exposure to anti-CD20 mAb in 380 patients. Prevalence of HG significantly differed by level of treatment exposure (p < 0.001). Single course anti-CD20 mAb was associated with rising IgG (+10.3 mg/dL/year), whereas the addition of maintenance therapy (-7.4 mg/dL/year) or multiple courses of treatment (-10.3 mg/dL/year) was associated with declining IgG. Among patients treated with anti-CD20 mAb, 45.2% developed IgG-HG and 10.3% developed symptomatic IgG-HG. Pretreatment IgG levels gradually declined in all patients, suggesting tumor burden may contribute to HG. Baseline and periodic monitoring of serum Ig is appropriate in patients with FL, including those managed with active surveillance.

Epitope Mapping of Rituximab Using HisMAP Method

CD20 is expressed in the B lymphocyte, and an effective target for the detection and treatment of B cell lymphomas. Therefore, CD20 has been studied as a therapeutic target of B cell lymphomas and autoimmune disorders. Specific anti-CD20 monoclonal antibodies (mAbs), such as rituximab, ofatumumab, veltuzumab, and ocaratuzumab, have been developed. Revealing the recognition mechanism of antigen by mAbs could contribute to understanding the function of mAbs and could be useful for the development of vaccine. Rituximab is a mouse-human chimeric anti-CD20 mAb, which was developed and approved for the treatment of the B cell malignancies. Hence, the binding epitope of rituximab for CD20 has been studied. Some reports show that ₁₇₀-ANPS-₁₇₃, especially Ala170 and Pro172 of CD20 are important for rituximab binding. However, only phage display results showed that ₁₈₂-YCYSI-₁₈₆ of CD20 is also important for rituximab binding to CD20. In this study, we tried to determine the binding epitope of rituximab for CD20 using histidine-tag insertion for epitope mapping (HisMAP) method. The results showed that two regions of CD20 (₁₆₉-PANPSE-₁₇₄ and ₁₈₃-CYSIQ-₁₈₇) are important for rituximab-binding for CD20.

Insights into Modern Therapeutic Approaches in Pediatric Acute Leukemias

Pediatric cancers predominantly constitute lymphomas and leukemias. Recently, our knowledge and awareness about genetic diversities, and their consequences in these diseases, have greatly expanded. Modern solutions are focused on mobilizing and impacting a patient’s immune system. Strategies to stimulate the immune system, to prime an antitumor response, are of intense interest. Amid those types of therapies are chimeric antigen receptor T (CAR-T) cells, bispecific antibodies, and antibody–drug conjugates (ADC), which have already been approved in the treatment of acute lymphoblastic leukemia (ALL)/acute myeloid leukemia (AML). In addition, immune checkpoint inhibitors (ICIs), the pattern recognition receptors (PRRs), i.e., NOD-like receptors (NLRs), Toll-like receptors (TLRs), and several kinds of therapy antibodies are well on their way to showing significant benefits for patients with these diseases. This review summarizes the current knowledge of modern methods used in selected pediatric malignancies and presents therapies that may hold promise for the future.

Antibody Targets and Properties for Complement-Fixation Against the Circumsporozoite Protein in Malaria Immunity

The Plasmodium falciparum circumsporozoite protein (CSP) forms the basis of leading subunit malaria vaccine candidates. However, the mechanisms and specific targets of immunity are poorly defined. Recent findings suggest that antibody-mediated complement-fixation and activation play an important role in immunity. Here, we investigated the regions of CSP targeted by functional complement-fixing antibodies and the antibody properties associated with this activity. We quantified IgG, IgM, and functional complement-fixing antibody responses to different regions of CSP among Kenyan adults naturally exposed to malaria (n=102) and using a series of rabbit vaccination studies. Individuals who acquired functional complement-fixing antibodies had higher IgG, IgM and IgG1 and IgG3 to CSP. Acquired complement-fixing antibodies targeted the N-terminal, central-repeat, and C-terminal regions of CSP, and positive responders had greater antibody breadth compared to those who were negative for complement-fixing antibodies (p<0.05). Using rabbit vaccinations as a model, we confirmed that IgG specific to the central-repeat and non-repeat regions of CSP could effectively fix complement. However, vaccination with near full length CSP in rabbits poorly induced antibodies to the N-terminal region compared to naturally-acquired immunity in humans. Poor induction of N-terminal antibodies was also observed in a vaccination study performed in mice. IgG and IgM to all three regions of CSP play a role in mediating complement-fixation, which has important implications for malaria vaccine development.

Chronic lymphocytic leukemia: 2022 update on diagnostic and therapeutic procedures

DISEASE OVERVIEW

Chronic lymphocytic leukemia (CLL) is one of the most frequent types of leukemia. It typically occurs in elderly patients and has a highly variable clinical course. Leukemic transformation is initiated by specific genomic alterations that interfere with the regulation of proliferation and of apoptosis in clonal B-cells.

DIAGNOSIS

The diagnosis is established by blood counts, blood smears, and immunophenotyping of circulating B-lymphocytes, which identify a clonal B-cell population carrying the CD5 antigen as well as typical B-cell markers.

PROGNOSIS AND STAGING

The clinical staging systems provide prognostic information by using the results of physical examination and blood counts. Various biological and genetic markers provide additional prognostic information. Deletions of the short arm of chromosome 17 (del[17p]) and/or mutations of the TP53 gene predict resistance to chemoimmunotherapy and a shorter time to progression with most targeted therapies. The CLL international prognostic index integrates genetic, biological, and clinical variables to identify distinct risk groups of patients with CLL.

THERAPY

Only patients with active or symptomatic disease or with advanced Binet or Rai stages require therapy. When treatment is indicated, several therapeutic options exist: a combination of the B-cell lymphoma 2 (BCL2) inhibitor venetoclax with obinutuzumab, monotherapy with inhibitors of Bruton tyrosine kinase (BTK) such as ibrutinib and acalabrutinib, or chemoimmunotherapy. At relapse, the initial treatment may be repeated, if the treatment-free interval exceeds 3 years. If the disease relapses earlier, therapy should be changed using an alternative regimen. Patients with a del(17p) or TP53 mutation are usually resistant to chemotherapy and should, therefore, be treated with targeted agents.

FUTURE CHALLENGES

Combinations of targeted agents are now being investigated to create efficient, potentially curative therapies of CLL with fixed duration. One of the most relevant questions currently addressed in clinical trials is the comparison of monotherapies with BTK inhibitors with fixed duration combination therapies. Moreover, the optimal sequencing of targeted therapies remains to be determined. Alternative therapies are needed for patients with BTK and BCL2 inhibitor double-refractory disease.

Revisiting an IgG Fc Loss-of-Function Experiment: the Role of Complement in HIV Broadly Neutralizing Antibody b12 Activity

The role of the complement system in HIV-1 immunity and pathogenesis is multifaceted, and an improved understanding of complement activities mediated by HIV-1-specific antibodies has the potential to inform and advance clinical development efforts. A seminal nonhuman primate challenge experiment suggested that complement was dispensable for the protective effect of the early broadly neutralizing antibody (bnAb) b12, but recent experiments have raised questions about the breadth of circumstances under which this conclusion may hold. Here, we reassess the original observation using Fc variants of IgG1 b12 that enhance complement activity and report that complement fixation on recombinant antigen, virions, and cells and complement-dependent viral and cellular lysis in vitro vary among bnAbs. Specifically, while the clinically significant V3 glycan-specific bnAb 10-1074 demonstrates activity, we found that b12 does not meaningfully activate the classical complement cascade. Consistent with avid engagement by C1q and its complex system of regulatory factors, these results suggest that complement-mediated antibody activities demonstrate a high degree of context dependence and motivate revisiting the role of complement in antibody-mediated prevention of HIV-1 infection by next-generation bnAbs in new translational studies in animal models.

On-target IgG hexamerisation driven by a C-terminal IgM tail-piece fusion variant confers augmented complement activation

The majority of depleting monoclonal antibody (mAb) drugs elicit responses via Fc-FcγR and Fc-C1q interactions. Optimal C1q interaction is achieved through hexameric Fc:Fc interactions at the target cell surface. Herein is described an approach to exploit the tailpiece of the naturally multimeric IgM to augment hexamerisation of IgG. Fusion of the C-terminal tailpiece of IgM promoted spontaneous hIgG hexamer formation, resulting in enhanced C1q recruitment and complement-dependent cytotoxicity (CDC) but with off-target complement activation and reduced in-vivo efficacy. Mutation of the penultimate tailpiece cysteine to serine (C575S) ablated spontaneous hexamer formation, but facilitated reversible hexamer formation after concentration in solution. C575S mutant tailpiece antibodies displayed increased complement activity only after target binding, in-line with the concept of 'on-target hexamerisation', whilst retaining efficient in-vivo efficacy and augmented target cell killing in the lymph node. Hence, C575S-tailpiece technology represents an alternative format for promoting on-target hexamerisation and enhanced CDC.

High-titre convalescent plasma therapy for an immunocompromised patient with systemic lupus erythematosus with protracted SARS-CoV-2 infection

A 39-year-old woman with systemic lupus erythematosus treated with anti-CD20 monoclonal antibody rituximab was admitted to our hospital with COVID-19 pneumonia. Despite receiving dexamethasone, she developed hypoxaemia and persistent lung opacities. As bronchoalveolar lavage was suggestive of cryptogenic organising pneumonia, high-dose corticosteroid was administered, and she received antimicrobial therapy for opportunistic infections without improvement. Reverse transcription PCR was repeatedly positive for SARS-CoV-2, and virus replication was confirmed in cell cultures. As no anti-SARS-CoV-2 antibodies were detected more than 100 days after symptom onset, she was treated with convalescent plasma with fast clinical improvement, returning home days later. Our case shows that persistent SARS-CoV-2 infection in an immunocompromised patient may be overturned with the appropriate treatment.

[Ofatumumab - a new drug for the treatment of multiple sclerosis]

Recently anti-B-cell therapy has been increasingly integrated into the treatment of multiple sclerosis (MS). This review is devoted to ofatumumab, a new drug of this line. Ofatumumab, an all-human monoclonal antibody used to treat chronic leukemia, binds to a different region than the binding site of other CD20 antibodies, including both a small and large loop in the CD20 receptor structure. This monoclonal antibody provides favorable results for MS by reducing the frequency of exacerbations and the risk of disability progression, significantly more pronounced when compared with teriflunomide. The drug can be used in patients with active relapsing MS and SPMS with exacerbations, with the ineffectiveness of first-line drugs as one of the options for second-line therapy, in patients with highly active MS, especially with a high risk of PML (transfer from natalizumab), as well as if there are difficulties in organizing intravenous courses in day hospitals (produced as outpatient injections).

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.

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.

Hyper-CVAD plus ofatumumab versus hyper-CVAD plus rituximab as frontline therapy in adults with Philadelphia chromosome-negative acute lymphoblastic leukemia: A propensity score analysis

BACKGROUND

The outcome of hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone plus ofatumumab hyper-CVAD + ofatumumab (hyper-CVAD + ofatumumab) has not been compared with the outcome of hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone plus ofatumumab hyper-CVAD plus rituximab (hyper-CVAD + Rituximab) in Philadelphia chromosome-negative acute lymphoblastic leukemia (ALL) in a randomized clinical trial.

METHODS

The authors compared the outcomes of 69 patients treated with hyper-CVAD + ofatumumab and 95 historical-control patients treated with hyper-CVAD + Rituximab. Historical-control patients were treated with hyper-CVAD + Rituximab if they had CD20 expression ≥ 20%. Ofatumumab (day 1 of course 1, 300 mg intravenously; subsequent doses, 2000 mg intravenously) was administered on days 1 and 11 of courses 1 and 3 and on days 1 and 8 of courses 2 and 4 for a total of 8 doses. A propensity score analysis with inverse probability of treatment weighting (IPTW) was performed to adjust for baseline covariates between groups.

RESULTS

The median event-free survival with stem cell transplantation (SCT) censoring was 33 and 65 months with hyper-CVAD + Rituximab and hyper-CVAD + ofatumumab, respectively (crude P = .064; IPTW P = .054). The median overall survival with SCT censoring was 52 months and not reached, respectively (crude P = .087; IPTW P = .097).

CONCLUSIONS

Hyper-CVAD + ofatumumab was associated with better outcomes than hyper-CVAD + Rituximab among patients with newly diagnosed Philadelphia chromosome-negative ALL.

Epstein-Barr virus-associated post-transplant lymphoproliferative disorders: beyond chemotherapy treatment

Post-transplant lymphoproliferative disorder (PTLD) is a rare but life-threatening complication of both allogeneic solid organ (SOT) and hematopoietic cell transplantation (HCT). The histology of PTLD ranges from benign polyclonal lymphoproliferation to a lesion indistinguishable from classic monoclonal lymphoma. Most commonly, PTLDs are Epstein-Barr virus (EBV) positive and result from loss of immune surveillance over EBV. Treatment for PTLD differs from the treatment for typical non-Hodgkin lymphoma because prognostic factors are different, resistance to treatment is unique, and there are specific concerns for organ toxicity. While recipients of HCT have a limited time during which they are at risk for this complication, recipients of SOT have a lifelong requirement for immunosuppression, so approaches that limit compromising or help restore immune surveillance are of high interest. Furthermore, while EBV-positive and EBV-negative PTLDs are not intrinsically resistant to chemotherapy, the poor tolerance of chemotherapy in the post-transplant setting makes it essential to minimize potential treatment-related toxicities and explore alternative treatment algorithms. Therefore, reduced-toxicity approaches such as single-agent CD20 monoclonal antibodies or bortezomib, reduced dosing of standard chemotherapeutic agents, and non-chemotherapy-based approaches such as cytotoxic T cells have all been explored. Here, we review the chemotherapy and non-chemotherapy treatment landscape for PTLD.

A phase 3 randomized study (HOMER) of ofatumumab vs rituximab in iNHL relapsed after rituximab-containing therapy

Because of high relapse rates with rituximab combinations, there is an unmet need for new therapeutic agents for treatment of indolent B-cell non-Hodgkin lymphoma (iNHL) or follicular lymphoma (FL). In previous trials, ofatumumab in combination with chemotherapy showed good results in relapsed/refractory FL pretreated with rituximab. This phase 3 trial evaluated the efficacy and safety of single-agent ofatumumab vs single-agent rituximab in rituximab-sensitive relapsed FL that relapsed at least 6 months after completing the last prior treatment with single-agent rituximab or a rituximab-containing regimen. Patients were randomized 1:1 to receive either ofatumumab (1000 mg) or rituximab (375 mg/m2) every week for 4 weeks for the induction phase, followed by once every 2 months for 4 additional doses. The primary endpoint, progression-free survival (PFS) and secondary endpoints, overall response rate (ORR) and overall survival (OS), were evaluated. Overall, 438 patients were assigned to receive ofatumumab (n = 219) and rituximab (n = 219). Baseline characteristics were similar in both arms. The independent review committee assessed whether median PFS was shorter in the ofatumumab arm than in the rituximab arm (16.33 vs 21.29 months), with no significant difference (hazard ratio, 1.15; 95% confidence interval, 0.89-1.49; P = .29) and also showed a lower ORR (50%) compared with the rituximab arm (66%). At the time of analysis, data were not matured for OS results. The number of grade >3 adverse events was higher in the ofatumumab arm (37%) than the rituximab arm (28%). Ofatumumab showed no superiority over rituximab in patients with FL who had relapsed after a rituximab-containing therapy. This study was registered at www.clinicaltrials.gov as #NCT01200589.

A phase 3, randomized study of ofatumumab combined with bendamustine in rituximab-refractory iNHL (COMPLEMENT A + B study)

The standard of care for indolent non-Hodgkin lymphoma (iNHL) is rituximab, an anti-CD20 antibody, with/without chemotherapy. However, multiple relapses are common in these patients. This phase 3, randomized study compared outcomes of a combination of ofatumumab (a second-generation anti-CD20 antibody) and bendamustine, with bendamustine alone in patients unresponsive to prior rituximab-based treatment. Overall, 346 patients were randomized to receive either the combination or bendamustine alone. Bendamustine was given for ≤8 cycles and ofatumumab for ≤12 cycles. The primary end-point was progression-free survival (PFS) after 215 protocol-defined events assessed by independent review committee (IRC). Median IRC-assessed PFS was 16·7 and 13·8 months in the combination and monotherapy arms respectively [hazard ratio (HR) = 0·82; P = 0·1390]. Median overall survival (OS) was 58·2 and 51·8 months in the combination and monotherapy arms respectively (HR = 0·89, P = 0·4968). The safety profile was consistent with previous reports. Overall, 73% and 80% of patients in the combination and monotherapy arms, respectively, experienced a ≥grade 3 adverse event. The study did not meet its primary end-point. No significant improvement in PFS and OS was seen with the combination of ofatumumab and bendamustine as compared with bendamustine alone in rituximab-refractory iNHL (NCT01077518).

Hydrogen deuterium exchange mass spectrometry identifies the dominant paratope in CD20 antigen binding to the NCD1.2 monoclonal antibody

A comparative canine–human therapeutics model is being developed in B-cell lymphoma through the generation of a hybridoma cell that produces a murine monoclonal antibody specific for canine CD20. The hybridoma cell produces two light chains, light chain-3, and light chain-7. However, the contribution of either light chain to the authentic full-length hybridoma derived IgG is undefined. Mass spectrometry was used to identify only one of the two light chains, light chain-7, as predominating in the full-length IgG. Gene synthesis created a recombinant murine–canine chimeric monoclonal antibody expressing light chain-7 that reconstituted the IgG binding to CD20. Using light chain-7 as a reference sequence, hydrogen deuterium exchange mass spectrometry was used to identify the dominant CDR region implicated in CD20 antigen binding. Early in the deuteration reaction, the CD20 antigen suppressed deuteration at CDR3 (V_H). In later time points, deuterium suppression occurred at CDR2 (V_H) and CDR2 (V_L), with the maintenance of the CDR3 (V_H) interaction. These data suggest that CDR3 (V_H) functions as the dominant antigen docking motif and that antibody aggregation is induced at later time points after antigen binding. These approaches define a methodology for fine mapping of CDR contacts using nested enzymatic reactions and hydrogen deuterium exchange mass spectrometry. These data support the further development of an engineered, synthetic canine–murine monoclonal antibody, focused on CDR3 (V_H), for use as a canine lymphoma therapeutic that mimics the human–murine chimeric anti-CD20 antibody Rituximab.