Is There a Future for Anti-CD38 Antibody Therapy in Systemic Autoimmune Diseases?

Therapeutic tactics for targeting B lymphocytes in autoimmunity and cancer

B lymphocytes have become a very popular therapeutic target in a number of autoimmune indications due to their newly appreciated roles, and approachability, in these diseases. Many of the therapies now applied in autoimmunity were initially developed to deplete malignant B cells. These strategies have also been found to benefit patients suffering from such autoimmune diseases as multiple sclerosis, type I diabetes, systemic lupus erythematosus, and rheumatoid arthritis, to name a few. These observations have supported the expansion of research addressing the mechanistic contributions of B cells in these diseases, as well as blossoming of therapeutics that target them. This review seeks to summarize cutting-edge modalities for targeting B cells, including monoclonal antibodies, bispecific antibodies, antibody-drug conjugates, chimeric antigen receptor-T cells, and small molecule inhibitors. Efforts to refine B-cell targeted therapy to eliminate only pathogenic autoreactive cells will be addressed as well as the potential for future B-cell-based cellular therapeutics. Finally, we also address approaches that seek to silence B-cell function without depletion.

B Cell Tolerance and Targeted Therapies in SLE

Systemic Lupus Erythematosus (SLE) is a chronic systemic autoimmune disease of high clinical and molecular heterogeneity, and a relapsing-remitting pattern. The disease is currently without cure and more prevalent in women. B cell tolerance and production of autoantibodies are critical mechanisms that drive SLE pathophysiology. However, how the balance of the immune system is broken and how the innate and adaptive immune systems are interacting during lupus-specific autoimmune responses are still largely unknown. Here, we review the latest knowledge on B cell development, maturation, and central versus peripheral tolerance in connection to SLE and treatment options. We also discuss the regulation of B cells by conventional T cells, granulocytes, and unconventional T cells, and how effector B cells exert their functions in SLE. We also discuss mechanisms of action of B cell-targeted therapies, as well as possible future directions based on current knowledge of B cell biology.

Novel Therapeutic Strategies in the Treatment of Systemic Sclerosis

Systemic sclerosis is a connective tissue disease of unknown origin and with an unpredictable course, with both cutaneous and internal organ manifestations. Despite the enormous progress in rheumatology and clinical immunology, the background of this disease is largely unknown, and no specific therapy exists. The therapeutic approach aims to treat and preserve the function of internal organs, and this approach is commonly referred to as organ-based treatment. However, in modern times, data from other branches of medicine may offer insight into how to treat disease-related complications, making it possible to find new drugs to treat this disease. In this review, we present therapeutic options aiming to stop the progression of fibrotic processes, restore the aberrant immune response, stop improper signalling from proinflammatory cytokines, and halt the production of disease-related autoantibodies.

The potential of CD38 protein as a target for autoimmune diseases

Cluster of differentiation 38 (CD38) is a multifunctional cell surface protein involved in nicotinamide adenine dinucleotide (NAD⁺) homeostasis in types of cells and tissues, which can be found in many immune cells and non-immune cells. Previous studies have shown that CD38 plays an important role in regulating innate immunity. Recently, many studies have revealed the importance of CD38 in autoimmune diseases, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), type 1 diabetes (T1D) and inflammatory bowel disease, among others. In this report, we will briefly discuss the complex immunological functions of CD38 and focus on recent advances in the role of CD38 in the development and pathogenesis of autoimmune diseases, as well as their potential as therapeutic targets for systemic diseases, intending to make a comprehensive understanding of CD38 and its promising therapeutic potential in these systemic diseases.

Autoantibodies as Biomarker and Therapeutic Target in Systemic Sclerosis

Systemic sclerosis (SSc) is a rare connective tissue disorder characterized by immune dysregulation evoking the pathophysiological triad of inflammation, fibrosis and vasculopathy. In SSc, several alterations in the B-cell compartment have been described, leading to polyclonal B-cell hyperreactivity, hypergammaglobulinemia and autoantibody production. Autoreactive B cells and autoantibodies promote and maintain pathologic mechanisms. In addition, autoantibodies in SSc are important biomarkers for predicting clinical phenotype and disease progression. Autoreactive B cells and autoantibodies represent potentially promising targets for therapeutic approaches including B-cell-targeting therapies, as well as strategies for unselective and selective removal of autoantibodies. In this review, we present mechanisms of the innate immune system leading to the generation of autoantibodies, alterations of the B-cell compartment in SSc, autoantibodies as biomarkers and autoantibody-mediated pathologies in SSc as well as potential therapeutic approaches to target these.

Development of New Drugs for Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is a rare disorder characterized by the autoantibody-mediated destruction of red blood cells, and treatments for it still remain challenging. Traditional first-line immunosuppressive therapy, which includes corticosteroids and rituximab, is associated with adverse effects as well as treatment failures, and relapses are common. Subsequent lines of therapy are associated with higher rates of toxicity, and some patients remain refractory to currently available treatments. Novel therapies have become promising for this vulnerable population. In this review, we will discuss the mechanism of action, existing data, and ongoing clinical trials of current novel therapies for AIHA, including B-cell-directed therapy, phagocytosis inhibition, plasma cell-directed therapy, and complement inhibition.

Systemic Sclerosis: From Pathophysiology to Novel Therapeutic Approaches

Systemic sclerosis (SSc) is a systemic, immune-mediated chronic disorder characterized by small vessel alterations and progressive fibrosis of the skin and internal organs. The combination of a predisposing genetic background and triggering factors that causes a persistent activation of immune system at microvascular and tissue level is thought to be the pathogenetic driver of SSc. Endothelial alterations with subsequent myofibroblast activation, excessive extracellular matrix (ECM) deposition, and unrestrained tissue fibrosis are the pathogenetic steps responsible for the clinical manifestations of this disease, which can be highly heterogeneous according to the different entity of each pathogenic step in individual subjects. Although substantial progress has been made in the management of SSc in recent years, disease-modifying therapies are still lacking. Several molecular pathways involved in SSc pathogenesis are currently under evaluation as possible therapeutic targets in clinical trials. These include drugs targeting fibrotic and metabolic pathways (e.g., TGF-β, autotaxin/LPA, melanocortin, and mTOR), as well as molecules and cells involved in the persistent activation of the immune system (e.g., IL4/IL13, IL23, JAK/STAT, B cells, and plasma cells). In this review, we provide an overview of the most promising therapeutic targets that could improve the future clinical management of SSc.

Dysregulated B cell function and disease pathogenesis in systemic sclerosis

Systemic sclerosis (SSc) is a complex, immune-mediated rheumatic disease characterised by excessive extracellular matrix deposition in the skin and internal organs. B cell infiltration into lesional sites such as the alveolar interstitium and small blood vessels, alongside the production of defined clinically relevant autoantibodies indicates that B cells play a fundamental role in the pathogenesis and development of SSc. This is supported by B cell and fibroblast coculture experiments revealing that B cells directly enhance collagen and extracellular matrix synthesis in fibroblasts. In addition, B cells from SSc patients produce large amounts of profibrotic cytokines such as IL-6 and TGF-β, which interact with other immune and endothelial cells, promoting the profibrotic loop. Furthermore, total B cell counts are increased in SSc patients compared with healthy donors and specific differences can be found in the content of naïve, memory, transitional and regulatory B cell compartments. B cells from SSc patients also show differential expression of activation markers such as CD19 which may shape interactions with other immune mediators such as T follicular helper cells and dendritic cells. The key role of B cells in SSc is further supported by the therapeutic benefit of B cell depletion with rituximab in some patients. It is notable also that B cell signaling is impaired in SSc patients, and this could underpin the failure to induce tolerance in B cells as has been shown in murine models of scleroderma.

Expression of CD38 in Mast Cells: Cytological and Histotopographic Features

The biological significance of the CD38 molecule goes beyond metabolic, enzymatic, and proliferative functions. CD38 possesses the functions of an exoenzyme and receptor, and is actively involved in the mechanisms of adhesion, migration, intercellular signaling, formation of immune synapses, and modulation of the activity of a wide range of immune and non-immune cells. The aim of this study was the immunohistochemical assessment of the cytological and histotopographic characteristics of CD38 expression in mast cells. CD38 expression was found in a minority of the mast cell population. It is characterized by wide variability from low to high levels. The intensity of CD38 expression in mast cells has organ-specific features and depends on the development of pathological processes in a specific tissue microenvironment. The mechanisms of intercellular interaction between mast cells and CD38+ cells foster new understanding of the protumorigenic or antitumor potential of tryptase.

Bortezomib: a proteasome inhibitor for the treatment of autoimmune diseases

Autoimmune diseases (ADs) are conditions in which the immune system cannot distinguish self from non-self and, as a result, tissue injury occurs primarily due to the action of various inflammatory mediators. Different immunosuppressive agents are used for the treatment of patients with ADs, but some clinical cases develop resistance to currently available therapies. The proteasome inhibitor bortezomib (BTZ) is an approved agent for first-line therapy of people with multiple myeloma. BTZ has been shown to improve the symptoms of different ADs in animal models and ameliorated symptoms in patients with systemic lupus erythematous, rheumatoid arthritis, myasthenia gravis, neuromyelitis optica spectrum disorder, Chronic inflammatory demyelinating polyneuropathy, and autoimmune hematologic diseases that were nonresponsive to conventional therapies. Proteasome inhibition provides a potent strategy for treating ADs. BTZ represents a proteasome inhibitor that can potentially be used to treat AD patients resistant to conventional therapies.

Daratumumab: Beyond Multiple Myeloma

Daratumumab (DARA) is the biological name of an Immunoglobulin G1k human monoclonal antibody. DARA the first-in-class therapy targeting CD38 expressing- plasma cells (PC) and plasma blasts. It has been approved for the treatment of multiple myeloma. It is also being examined in the setting of other hematologic malignancies. As DARA targets PCs, it could potentially be used to treat many other disease processes that are antibody mediated. In fact, several case reports and case series report experiences of using DARA to treat a variety of antibody-mediated disorderss. The aim of this review is to present a summary of the literature thus far regarding the application of DARA beyond its uses in multiple myeloma and other hematologic diseases. Specifically, we address uses of DARA as an immunologic modulator in various antibody mediated processes.

Case Report: Resetting the Humoral Immune Response by Targeting Plasma Cells With Daratumumab in Anti-Phospholipid Syndrome

Introduction

Monoclonal antibodies (mAb) targeting plasma cells are malignant gammopathy designed and approved therapies. In recent years, these antibodies have also been increasingly introduced for non-malignant conditions such as autoimmune-mediated diseases. The Anti-Phospholipid Syndrome (APS) is an immune-mediated disorder in which autoantibodies against phospholipid associated proteins could elicit the activation of the coagulation cascade in specific situations. Therefore, the mainstream treatment for APS patients is the use of anticoagulant therapy. However, there are refractory patients who would benefit from targeting the antibodies rather than their effects. Rituximab, a B-cell depleting mAb, and intravenous immunoglobulins (IVIG) have been used in APS patients without showing a clear beneficial effect or a significant drop in anti-phospholipid antibody (aPL) levels.

Clinical case

We present our first APS case treated with daratumumab, an anti-CD38 mAb, in a 21-year-old patient with APS who presented with recurrent venous thromboembolic events despite adequate anticoagulant therapy. She tested positive for lupus anticoagulant, anti-cardiolipin IgG, anti-beta-2-glycoprotein-I IgG and anti-phosphatidylserine/prothrombin IgG and IgM. She was administered one dose weekly of daratumumab for 4 weeks. The treatment showed an adequate safety profile and was well tolerated. The patient was discharged after undergoing a clinically significant improvement. After the therapy, her levels of positive aPL declined significantly and most continued to decrease during the next three months. The patient experienced a new thrombotic episode two years after the therapy associated with poor adherence to antithrombotic therapy.

Conclusions

The treatment with daratumumab showed an adequate safety profile, was well tolerated and led to a significant clinical improvement. Levels of aPL lowered on therapy and the next three months and then rose again during follow-up. Further investigation is needed to better elucidate the role and optimal timing and doses of daratumumab in treatment of refractory APS.

Impact of new myeloma agents on the transfusion laboratory

Monoclonal antibody (mAb) therapy targeting CD38 and CD47 antigens expressed on cancer cells has transformed therapy options for patients with multiple myeloma as well as other haematological and non-haematological malignancies. While the on target effects of these new drugs highlight the promise of precision cancer therapeutics, the unintended, off target binding of drugs to red blood cells (RBCs) and platelets has required transfusion service laboratories (TSL) and immunohaematology reference laboratories (IRL) to innovate and rapidly set up processes and testing protocols to overcome the significant interference in routine pre-transfusion tests caused by these agents. Binding of anti-CD38 and anti-CD47 drugs to reagent RBCs leads to false positive pan-agglutination during the antihuman globulin phase of testing, making it difficult to rule out underlying alloantibodies, and leading to delays in setting up compatible units for RBC transfusion. Anti-CD47 agents can also interfere with ABO/Rh typing studies. Several methods to successfully mitigate interference have been described, such as treatment of reagent RBCs with reducing agents or enzymes, allogeneic RBC adsorption studies and drug specific neutralisation assays; all methods have limitations. TSLs should select an approach that best fits their workflow and expertise and takes into consideration their level of access to specialised outside testing, local blood supplier capabilities, and the type of patient population served. For platelet refractory patients, samples should be tested by platelet antibody assays that are known to be unaffected by drug therapy. RBC transfusion support for multiple myeloma patients receiving anti-CD38 or anti-CD47 drugs can be optimised by establishing good communication between the clinical teams and TSLs, building electronic notification processes, and ensuring timely completion of baseline pre-transfusion testing and RBC phenotype/genotype prior to starting therapy. Staff education, standardisation of laboratory mitigation measures, and implementation of testing algorithms that consider mAb-induced interference when working up a pan-agglutinin help to significantly decrease delays that would otherwise result if standard methods were employed to complete antibody identification studies.