Anti-CS1 humanized monoclonal antibody HuLuc63 inhibits myeloma cell adhesion and induces antibody-dependent cellular cytotoxicity in the bone marrow milieu

Promising Antigens for the New Frontier of Targeted Immunotherapy in Multiple Myeloma

Simple Summary

Defining the specificity and biological sequalae induced by receptors differentiated expressed in multiple myeloma cells are critical for the development of effective immunotherapies based on monoclonal antibodies. Ongoing studies continue to discover new antigens with superior tumor selectivity and defined function in regulating the pathophysiology of myeloma cells directly or indirectly in the immunosuppressive bone marrow microenvironment. Meanwhile, it is urgent to identify mechanisms of immune resistance and design more potent immunotherapies, alone and/or with best combination partners to further prolong anti-MM immunity.

Abstract

The incorporation of novel agents in recent treatments in multiple myeloma (MM) has improved the clinical outcome of patients. Specifically, the approval of monoclonal antibody (MoAb) against CD38 (daratumumab) and SLAMF7 (elotuzumab) in relapsed and refractory MM (RRMM) represents an important milestone in the development of targeted immunotherapy in MM. These MoAb-based agents significantly induce cytotoxicity of MM cells via multiple effector-dependent mechanisms and can further induce immunomodulation to repair a dysfunctional tumor immune microenvironment. Recently, targeting B cell maturation antigen (BCMA), an even MM-specific antigen, has shown high therapeutic activities by chimeric antigen receptor T cells (CAR T), antibody-drug conjugate (ADC), bispecific T-cell engager (BiTE), as well as bispecific antibody (BiAb), with some already approved for heavily pretreated RRMM patients. New antigens, such as orphan G protein-coupled receptor class C group 5 member D (GPRC5D) and FcRH5, were identified and rapidly moved to ongoing clinical studies. We here summarized the pathobiological function of key MM antigens and the status of the corresponding immunotherapies. The potential challenges and emerging treatment strategies are also discussed.

Population pharmacokinetic and exposure-response analyses of elotuzumab plus pomalidomide and dexamethasone for relapsed and refractory multiple myeloma

Purpose

Elotuzumab plus pomalidomide/dexamethasone (E-Pd) demonstrated efficacy and safety in relapsed and refractory multiple myeloma (RRMM). The clinical pharmacology of elotuzumab [± lenalidomide/dexamethasone (Ld)] was characterized previously. These analyses describe elotuzumab population pharmacokinetics (PPK), the effect of Pd, and assess elotuzumab exposure–response relationships for efficacy and safety in patients with RRMM.

Methods

A previously established PPK model was updated with E-Pd data from the phase 2 ELOQUENT-3 study (NCT02654132). The dataset included 8180 serum concentrations from 440 patients with RRMM from 5 clinical trials. Elotuzumab PK parameter estimates were used to generate individual daily time-varying average concentrations (daily C_avg) for multi-variable time-to-event exposure–response analyses of progression-free survival (PFS) and time to the first occurrence of grade 3 + adverse events (AEs) in RRMM.

Results

Elotuzumab PK were well-described by a two-compartment model with parallel linear and Michaelis–Menten elimination from the central compartment (V_max) and non-renewable target-mediated elimination from the peripheral compartment (K_int). Co-administration with Pd resulted in a 19% and 51% decrease in elotuzumab linear clearance and K_int, respectively, versus Ld; steady-state exposures were similar. V_max increased with increasing serum M-protein. Hazard ratios (95% confidence intervals) for daily C_avg were 0.9983 (0.9969–0.9997) and 0.9981 (0.9964–0.9998) for PFS and grade 3 + AEs, respectively.

Conclusions

The PPK model adequately described the data and was appropriate for determining exposures for exposure–response analyses. There were no clinically relevant differences in elotuzumab exposures between Pd and Ld backbones. In ELOQUENT-3, increasing elotuzumab daily C_avg prolonged PFS without increasing grade 3 + AEs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-021-04365-4.

A phase 2 trial of the efficacy and safety of elotuzumab in combination with pomalidomide, carfilzomib and dexamethasone for high-risk relapsed/refractory multiple myeloma

High-risk multiple myeloma (MM) continues to have a poor prognosis and remains a therapeutic challenge. This phase 2 study evaluated the efficacy and safety of elotuzumab in combination with pomalidomide, carfilzomib, and low-dose dexamethasone for patients with high-risk relapsed/refractory (RR)MM (NCT03104270). Of 13 enrolled patients, 11 were evaluable for efficacy. Overall response rate and clinical benefit rate were 45.4% and 54.5%, respectively. Deep responses were observed including two complete responses. The novel quadruplet combination was overall well-tolerated, with clinically manageable adverse events. Common adverse events of ≥ grade 3 included lymphopenia (15%), anemia (15%), sepsis (15%), pneumonia (15%), and hypophosphatemia (15%). The novel combination showed promising efficacy and was well tolerated in this heavily pretreated MM population. Even though the study was terminated early prior to completion of enrollment, the results indicate that this may be a promising therapeutic approach for high-risk RRMM patients, which warrants further study.

CS1-specific single-domain antibodies labeled with Actinium-225 prolong survival and increase CD8+ T cells and PD-L1 expression in Multiple Myeloma

Multiple myeloma (MM) is a hematological malignancy characterized by the presence of clonal plasma cells in the bone marrow niche. Despite significant therapeutic advances, MM remains incurable for the majority of patients. Targeted radionuclide therapy (TRNT) has emerged as a promising treatment option to eradicate residual cancer cells. In this study, we developed and characterized single-domain antibodies (sdAbs) against the MM-antigen CS1 and evaluated its therapeutic potential in MM using TRNT. We first validated CS1 as potential target for TRNT. CS1 is expressed in normal and malignant plasma cells in different disease stages including progression and relapse. It is expressed in dormant as well as proliferating MM cells, while low expression could be observed in environmental cells. Biodistribution studies demonstrated the specific uptake of anti-CS1 sdAbs in tissues of 5TMM cell infiltration including bone, spleen and liver. TRNT using anti-CS1 sdAbs labeled with actinium-225 significantly prolonged survival of syngeneic, immunocompetent 5T33MM mice. In addition, we observed an increase in CD8⁺ T-cells and more overall PD-L1 expression on immune and non-immune cells, implying an interferon gamma signature using actinium-225 labeled CS1-directed sdAbs. In this proof-of-principle study, we highlight, for the first time, the therapeutic potential and immunomodulating effects of anti-CS1 radionuclide therapy to target residual MM cells.

Chromosomal 1q21 abnormalities in multiple myeloma: a review of translational, clinical research, and therapeutic strategies

INTRODUCTION

Multiple myeloma (MM) remains an incurable disease with a median overall survival of approximately 5 years. Gain or amplification of 1q21 (1q21+) occurs in around 40% of patients with MM and generally portends a poor prognosis. Patients with MM who harbor 1q21+ are at increased risk of drug resistance, disease progression, and death. New pharmacotherapies with novel modes of action are required to overcome the negative prognostic impact of 1q21+. Areas covered: This review discusses the detection, biology, prognosis, and therapeutic targeting of 1q21+ in newly diagnosed and relapsed MM. Patients with MM and 1q21+ tend to present with higher tumor burden, greater end-organ damage, and more co-occurring high-risk cytogenetic abnormalities than patients without 1q21+. The chromosomal rearrangements associated with 1q21+ result in dysregulation of genes involved in oncogenesis. Identification and characterization of the 1q21+ molecular targets are needed to inform on prognosis and treatment strategy. Clinical trial data are emerging that addition of isatuximab to combination therapies may improve outcomes in patients with 1q21+ MM. Expert opinion: In the next 5 years, the results of ongoing research and trials are likely to focus on the therapeutic impact and treatment decisions associated with 1q21+ in MM.

Multiple myeloma: therapeutic delivery of antibodies and aptamers

Multiple myeloma is the second most common hematological malignancy in adults, accounting for 2% of all cancer-related deaths in the UK. Current chemotherapy-based regimes are insufficient, as most patients relapse and develop therapy resistance. This review focuses on current novel antibody- and aptamer-based therapies aiming to overcome current therapy limitations, as well as their respective limitations and areas of improvement. The use of computer modeling methods, as a tool to study and improve ligand-receptor alignments for the use of novel therapy development will also be discussed, as it has become a rapid, reliable and comparatively inexpensive method of investigation.

BCMA in Multiple Myeloma-A Promising Key to Therapy

Despite the discoveries of numerous agents including next generation proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies, multiple myeloma (MM) remains an incurable disease. The field of myeloma treatment in refractory or relapsed patients after standard therapy entered a new era due to the B-cell maturation antigen (BMCA) targeted approach. BCMA is a member of the tumor necrosis factor receptor family with high expression in mature B-lymphocytes and plasma cells. Given the understanding of BCMA mechanism of action in MM, BCMA plays a promising role as a therapeutic target. Several clinical trials are underway to evolve the current BCMA targeted treatment concept such as antibody-drug conjugates (ADCs), bispecific T cell engagers (BITEs) and chimeric antigen receptor (CAR) T cell therapy. Current results of representative BCMA trials may close the gap of the unmet clinical need to further improve the outcome of heavily pretreated MM patients with the potency to change the paradigm in newly diagnosed and refractory MM. This comprehensive review will give an update on various BMCA targeted treatment modalities (ADCs, BITEs, CAR T cell therapy) and its existing results on efficacy and safety from preclinical and clinical trials.

Current status and perspective of CAR-T and CAR-NK cell therapy trials in Germany

Chimeric antigen receptor (CAR)-T cell therapies are on the verge of becoming powerful immunotherapeutic tools for combating hematological diseases confronted with pressing medical needs. Lately, CAR-NK cell therapies have also come into focus as novel therapeutic options to address hurdles related to CAR-T cell therapies, such as therapy-induced side effects. Currently, more than 500 CAR-T and 17 CAR-NK cell trials are being conducted worldwide including the four CAR-T cell products Kymriah, Yescarta, Tecartus and Breyanzi, which are already available on the market. Most CAR-T cell-based gene therapy products that are under clinical evaluation consist of autologous enriched T cells, whereas CAR-NK cell-based approaches can be generated from allogeneic donors. Besides modification based on a second-generation CAR, more advanced CAR-immune cell therapeutics are being tested, which utilize precise insertion of genes to circumvent graft-versus-host disease (GvHD) or employ a dual targeting approach and adapter CARs in order to avoid therapy resistance caused by antigen loss. In this review, we are going to take a closer look at the commercial CAR-T cell therapies, as well as on CAR-T and CAR-NK cell products, which are currently under evaluation in clinical trials, that are being conducted in Germany.

On the road to eliminating long-lived plasma cells-"are we there yet?"

Central to protective humoral immunity is the activation of B cells and their terminal differentiation into antibody-secreting plasma cells. Long-lived plasma cells (LLPC) may survive for years to decades. Such long-lived plasma cells are also responsible for producing pathogenic antibodies that cause a variety of challenges such as autoimmunity, allograft rejection, and drug neutralization. Up to now, various therapeutic strategies aimed at durably eliminating pathogenic antibodies have failed, in large part due to their inability to efficiently target LLPCs. Several antibody-based therapies have recently gained regulatory approval or are in clinical phases of development for the treatment of multiple myeloma, a malignancy of plasma cells. We discuss the exciting potential of using these emerging cancer immunotherapies to solve the antibody problem.

Mechanisms of Action of the New Antibodies in Use in Multiple Myeloma

Monoclonal antibodies (mAbs) directed against antigen-specific of multiple myeloma (MM) cells have Fc-dependent immune effector mechanisms, such as complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP), but the choice of the antigen is crucial for the development of effective immuno-therapy in MM. Recently new immunotherapeutic options in MM patients have been developed against different myeloma-related antigens as drug conjugate-antibody, bispecific T-cell engagers (BiTEs) and chimeric antigen receptor (CAR)-T cells. In this review, we will highlight the mechanism of action of immuno-therapy currently available in clinical practice to target CD38, SLAMF7, and BCMA, focusing on the biological role of the targets and on mechanisms of actions of the different immunotherapeutic approaches underlying their advantages and disadvantages with critical review of the literature data.

Cancer therapies based on targeted protein degradation - lessons learned with lenalidomide

For decades, anticancer targeted therapies have been designed to inhibit kinases or other enzyme classes and have profoundly benefited many patients. However, novel approaches are required to target transcription factors, scaffolding proteins and other proteins central to cancer biology that typically lack catalytic activity and have remained mostly recalcitrant to drug development. The selective degradation of target proteins is an attractive approach to expand the druggable proteome, and the selective oestrogen receptor degrader fulvestrant served as an early example of this concept. Following a long and tragic history in the clinic, the immunomodulatory imide drug (IMiD) thalidomide was discovered to exert its therapeutic activity via a novel and unexpected mechanism of action: targeting proteins to an E3 ubiquitin ligase for subsequent proteasomal degradation. This discovery has paralleled and directly catalysed myriad breakthroughs in drug development, leading to the rapid maturation of generalizable chemical platforms for the targeted degradation of previously undruggable proteins. Decades of clinical experience have established front-line roles for thalidomide analogues, including lenalidomide and pomalidomide, in the treatment of haematological malignancies. With a new generation of 'degrader' drugs currently in development, this experience provides crucial insights into class-wide features of degraders, including a unique pharmacology, mechanisms of resistance and emerging therapeutic opportunities. Herein, we review these past experiences and discuss their application in the clinical development of novel degrader therapies.

NK cell surveillance of hematological malignancies. Therapeutic implications and regulation by chemokine receptors

NK cells are circulating innate lymphoid cells that constantly move from bloodstream into tissues, exerting several functions including tumor surveillance. For this reason, NK cells are considered attractive target for cancer immunotherapy. Several strategies are employed to harness NK cell efficacy especially in hematological tumors, including adoptive transfer, genetic manipulation to overexpress chimeric antigen receptors and cytokine or immunomodulatory drug treatments of ex-vivo cultivated and expanded NK cells. Several chemokine receptors support NK cell tissue homing and are required for efficient tumor infiltration. Nevertheless, chemokine receptor expression is often insufficient, or their respective ligands may not be expressed in the tumor microenvironment, thus limiting NK cell localization at the tumor site. Therefore, strategies to implement expression or promote the function of the correct chemokine receptor/ligand axes have been employed in the last years with promising results in preclinical models. In this review, we discuss how chemokine receptors and their ligands regulate the trafficking and localization of NK cells in hematological tumors and how the chemokine function can be manipulated to improve current therapeutic approaches.

Pathophysiology and Therapeutic Approaches to Cardiac Amyloidosis

Often considered a rare disease, cardiac amyloidosis is increasingly recognized by practicing clinicians. The increased rate of diagnosis is in part due the aging of the population and increasing incidence and prevalence of cardiac amyloidosis with advancing age, as well as the advent of noninvasive methods using nuclear scintigraphy to diagnose transthyretin cardiac amyloidosis due to either variant or wild type transthyretin without a biopsy. Perhaps the most important driver of the increased awareness is the elucidation of the biologic mechanisms underlying the pathogenesis of cardiac amyloidosis which have led to the development of several effective therapies with differing mechanisms of actions. In this review, the mechanisms underlying the pathogenesis of cardiac amyloidosis due to light chain (AL) or transthyretin (ATTR) amyloidosis are delineated as well as the rapidly evolving therapeutic landscape that has emerged from a better pathophysiologic understanding of disease development.

Targeted Therapies for Multiple Myeloma

Multiple myeloma continues to be a challenging disorder to treat despite improved therapies and the widespread use of proteasome inhibitors and immunomodulatory drugs. Although patient outcomes have improved, the disease continues to invariably relapse, and in the majority of cases, a cure remains elusive. In the last decade, there has been an explosion of novel drugs targeting cellular proteins essential for malignant plasma cell proliferation and survival. In this review, we focus on novel druggable targets leading to the development of monoclonal antibodies and cellular therapies against surface antigens (CD38, CD47, CD138, BCMA, SLAMF7, GPRC5D, FcRH5), inhibitors of epigenetic regulators such as histone deacetylase (HDAC), and agents targeting anti-apoptotic (BCL-2), ribosomal (eEF1A2) and nuclear export (XPO1) proteins.

CARAMBA: a first-in-human clinical trial with SLAMF7 CAR-T cells prepared by virus-free Sleeping Beauty gene transfer to treat multiple myeloma

Clinical development of chimeric antigen receptor (CAR)-T-cell therapy has been enabled by advances in synthetic biology, genetic engineering, clinical-grade manufacturing, and complex logistics to distribute the drug product to treatment sites. A key ambition of the CARAMBA project is to provide clinical proof-of-concept for virus-free CAR gene transfer using advanced Sleeping Beauty (SB) transposon technology. SB transposition in CAR-T engineering is attractive due to the high rate of stable CAR gene transfer enabled by optimized hyperactive SB100X transposase and transposon combinations, encoded by mRNA and minicircle DNA, respectively, as preferred vector embodiments. This approach bears the potential to facilitate and expedite vector procurement, CAR-T manufacturing and distribution, and the promise to provide a safe, effective, and economically sustainable treatment. As an exemplary and novel target for SB-based CAR-T cells, the CARAMBA consortium has selected the SLAMF7 antigen in multiple myeloma. SLAMF7 CAR-T cells confer potent and consistent anti-myeloma activity in preclinical assays in vitro and in vivo. The CARAMBA clinical trial (Phase-I/IIA; EudraCT: 2019-001264-30) investigates the feasibility, safety, and anti-myeloma efficacy of autologous SLAMF7 CAR-T cells. CARAMBA is the first clinical trial with virus-free CAR-T cells in Europe, and the first clinical trial that uses advanced SB technology worldwide.

Antibody-Based Treatment Approaches in Multiple Myeloma

PURPOSE OF REVIEW

The field of multiple myeloma treatment has entered a new era with antibody-based approaches in clinical practice. In this review, we focus on the clinical approaches of utilizing antibody-based modality, specifically monoclonal antibodies, antibody-drug conjugates, and bispecific T-cell antibodies in the treatment of multiple myeloma.

RECENT FINDINGS

Three monoclonal antibodies (daratumumab, isatuximab, elotuzumab) and one anti-BCMA (B-cell maturation antigen) antibody-drug conjugate (belantamab mafodotin) have been approved by the FDA in the last 5 years for the treatment of multiple myeloma. There are many ongoing clinical trials using novel targets and constructs, including bispecific antibodies against BCMA, GPRC5D, and FCRH5. In addition to exploring efficacy, there are ongoing efforts to overcome the resistance to therapy. Antibody-based therapy has improved the outcomes of patients with multiple myeloma and has been incorporated in the standard of care. We expect to see novel targets and constructs that can achieve a deeper and more durable response while minimizing toxicity, as well as better strategies for toxicity management for existing agents. We also expect that antibody-based strategies will be used in earlier lines of therapy in the future.

Facts and Hopes in Multiple Myeloma Immunotherapy

Among the hallmarks of cancer is the ability of neoplastic cells to evade and suppress immune surveillance to allow their growth and evolution. Nowhere is this as apparent as in multiple myeloma, a cancer of antibody-producing plasma cells, where a complex interplay between neoplastic cells and the immune microenvironment is required for the development and progression of disease. Decades of research has led to the discovery of a number of therapeutic agents, from cytotoxic drugs to genetically engineered cells that mediate their antimyeloma effects at least partially through altering these immune interactions. In this review, we discuss the history of immunotherapy and current practices in multiple myeloma, as well as the advances that promise to one day offer a cure for this deadly disease.

A Review of Chimeric Antigen Receptor T-Cell Therapy for Myeloma and Lymphoma

Collectively, hematological malignancies account for the fourth most common malignancy. Myeloma and lymphoma are the most common types of hematological malignancies. Unfortunately, the management of refractory myeloma and lymphoma remains challenging. The discovery of new immunological therapies, namely chimeric antigen receptors T cells (CAR-T), outlined unprecedented B cell malignancies results. In this context, the CAR-T-based approach has led to the proliferation of many clinical studies. In this review, we will deal with the CAR-T structure, and we will summarize the primary clinical studies assessing the risks and benefits of CAR-T cell therapy. We will also deal with the adverse events and management of cytokine release syndromes/immune effector cell-associated neurotoxicity syndrome (ICANS). Subsequently, we will review potential future improvements to overcome refractoriness and improve expansion while decreasing CAR-T's off-target effects. The advances in the CAR-T platform represent a step forward with promising unlimited future possibilities that made it a paradigm-shifting for the management of B cell malignancies.

Immune System Alterations in Multiple Myeloma: Molecular Mechanisms and Therapeutic Strategies to Reverse Immunosuppression

Simple Summary

A common characteristic of multiple myeloma (MM) is the dysfunction of patients’ immune system, a condition termed immunosuppression. This state is mainly due to alterations in the number and functionality of the principal immune populations. In this setting, immunotherapy has acquired high relevance in the last years and the investigation of agents that boost the immune system represent a field of interest. In the present review, we will summarize the main cellular and molecular alterations observed in MM patients’ immune system. Furthermore, we will describe the mechanisms of action of the four immunotherapeutic drugs approved so far for the treatment of MM, which are part of the group of monoclonal antibodies (mAbs). Finally, the immune-stimulating effects of several therapeutic agents are described due to their potential role in reversing immunosuppression and, therefore, in favoring the efficacy of immunotherapy drugs, such as mAbs, as part of future pharmacological combinations.

Abstract

Immunosuppression is a common feature of multiple myeloma (MM) patients and has been associated with disease evolution from its precursor stages. MM cells promote immunosuppressive effects due to both the secretion of soluble factors, which inhibit the function of immune effector cells, and the recruitment of immunosuppressive populations. Alterations in the expression of surface molecules are also responsible for immunosuppression. In this scenario, immunotherapy, as is the case of immunotherapeutic monoclonal antibodies (mAbs), aims to boost the immune system against tumor cells. In fact, mAbs exert part of their cytotoxic effects through different cellular and soluble immune components and, therefore, patients’ immunosuppressive status could reduce their efficacy. Here, we will expose the alterations observed in symptomatic MM, as compared to its precursor stages and healthy subjects, in the main immune populations, especially the inhibition of effector cells and the activation of immunosuppressive populations. Additionally, we will revise the mechanisms responsible for all these alterations, including the interplay between MM cells and immune cells and the interactions among immune cells themselves. We will also summarize the main mechanisms of action of the four mAbs approved so far for the treatment of MM. Finally, we will discuss the potential immune-stimulating effects of non-immunotherapeutic drugs, which could enhance the efficacy of immunotherapeutic treatments.

The Landscape of Signaling Pathways and Proteasome Inhibitors Combinations in Multiple Myeloma

Multiple myeloma is a malignancy of terminally differentiated plasma cells, characterized by an extreme genetic heterogeneity that poses great challenges for its successful treatment. Due to antibody overproduction, MM cells depend on the precise regulation of the protein degradation systems. Despite the success of PIs in MM treatment, resistance and adverse toxic effects such as peripheral neuropathy and cardiotoxicity could arise. To this end, the use of rational combinatorial treatments might allow lowering the dose of inhibitors and therefore, minimize their side-effects. Even though the suppression of different cellular pathways in combination with proteasome inhibitors have shown remarkable anti-myeloma activities in preclinical models, many of these promising combinations often failed in clinical trials. Substantial progress has been made by the simultaneous targeting of proteasome and different aspects of MM-associated immune dysfunctions. Moreover, targeting deranged metabolic hubs could represent a new avenue to identify effective therapeutic combinations with PIs. Finally, epigenetic drugs targeting either DNA methylation, histone modifiers/readers, or chromatin remodelers are showing pleiotropic anti-myeloma effects alone and in combination with PIs. We envisage that the positive outcome of patients will probably depend on the availability of more effective drug combinations and treatment of early MM stages. Therefore, the identification of sensitive targets and aberrant signaling pathways is instrumental for the development of new personalized therapies for MM patients.

Elotuzumab for the treatment of extramedullary myeloma: a retrospective analysis of clinical efficacy and SLAMF7 expression patterns

Extramedullary disease (EMD) represents a high-risk state of multiple myeloma (MM) associated with poor prognosis. While most anti-myeloma therapeutics demonstrate limited efficacy in this setting, some studies exploring the utility of chimeric antigen receptor (CAR)-modified T cells reported promising results. We have recently designed SLAMF7-directed CAR T cells for the treatment of MM. SLAMF7 is a transmembrane receptor expressed on myeloma cells that plays a role in myeloma cell homing to the bone marrow. Currently, the only approved anti-SLAMF7 therapeutic is the monoclonal antibody elotuzumab, but its efficacy in EMD has not been investigated thoroughly. Thus, we retrospectively analyzed the efficacy of elotuzumab-based combination therapy in a cohort of 15 patients with EMD. Moreover, since the presence of the target antigen is an indispensable prerequisite for effective targeted therapy, we investigated the SLAMF7 expression on extramedullary located tumor cells before and after treatment. We observed limited efficacy of elotuzumab-based combination therapies, with an overall response rate of 40% and a progression-free and overall survival of 3.8 and 12.9 months, respectively. Before treatment initiation, all available EMD tissue specimens (n = 3) demonstrated a strong and consistent SLAMF7 surface expression by immunohistochemistry. Furthermore, to investigate a potential antigen reduction under therapeutic selection pressure, we analyzed samples of de novo EMD (n = 3) outgrown during elotuzumab treatment. Again, immunohistochemistry documented strong and consistent SLAMF7 expression in all samples. In aggregate, our data point towards a retained expression of SLAMF7 in EMD and encourage the development of more potent SLAMF7-directed immunotherapies, such as CAR T cells.

A simple method to distinguish residual elotuzumab from monoclonal paraprotein in immunofixation assays for multiple myeloma patients

Negative immunofixation electrophoresis (IFE) of serum and/or urine is a diagnostic marker for determining a complete response (CR) after immunotherapy for multiple myeloma (MM). However, residual therapeutic antibodies such as elotuzumab (IgG-κ), can compromise IFE evaluation when the affected immunoglobulins belong to the same IgG-κ subclass. We thus sought to develop a simple and rapid method to treat patient serum before IFE to distinguish the residual elotuzumab. Serum samples from patients receiving elotuzumab were treated with a predetermined amount of soluble signaling lymphocyte activation molecule F7 (SLAMF7) protein and then subjected to conventional IFE testing. We tested our method in samples from 12 patients. The IgG-κ band in IFE disappeared or shifted after elotuzumab treatment in four patients with no bone marrow minimal residual disease and normalized free light chain, whereas seven patients with any sign of residual MM showed a remaining IgG-κ band after treatment. One-hour incubation of samples with 6-9 molar excess soluble SLAMF7 before IFE was sufficient to distinguish residual elotuzumab in 11 of 12 samples. This simple method does not require special reagents, can be performed in most clinical laboratories, and enables differentiation between patients with a CR and those requiring further treatment.

Harnessing the Immune System Against Multiple Myeloma: Challenges and Opportunities

Multiple myeloma (MM) is an incurable malignancy of plasma cells that grow within a permissive bone marrow microenvironment (BMM). The bone marrow milieu supports the malignant transformation both by promoting uncontrolled proliferation and resistance to cell death in MM cells, and by hampering the immune response against the tumor clone. Hence, it is expected that restoring host anti-MM immunity may provide therapeutic benefit for MM patients. Already several immunotherapeutic approaches have shown promising results in the clinical setting. In this review, we outline recent findings demonstrating the potential advantages of targeting the immunosuppressive bone marrow niche to restore effective anti-MM immunity. We discuss different approaches aiming to boost the effector function of T cells and/or exploit innate or adaptive immunity, and highlight novel therapeutic opportunities to increase the immunogenicity of the MM clone. We also discuss the main challenges that hamper the efficacy of immune-based approaches, including intrinsic resistance of MM cells to activated immune-effectors, as well as the protective role of the immune-suppressive and inflammatory bone marrow milieu. Targeting mechanisms to convert the immunologically “cold” to “hot” MM BMM may induce durable immune responses, which in turn may result in long-lasting clinical benefit, even in patient subgroups with high-risk features and poor survival.

Elotuzumab in the treatment of relapsed and refractory multiple myeloma

Multiple myeloma (MM) is still considered an incurable disease. However, drugs with different mechanisms of action that can improve the efficiency of treatment offer hope. Still, there are concerns about an unacceptable increase in toxicity with such regimens. The results of recently published clinical studies of elotuzumab in combination with lenalidomide/dexamethasone or pomalidomide/dexamethasone confirm previous hopes to improve the effect of that treatment. Humanized monoclonal antibodies aimed at SLAMF7 stimulate natural killer cells to fight against MM cells. Elotuzumab used in combination with lenalidomide/dexamethasone or with pomalidomide/dexamethasone is approved by the US FDA to treat patients with relapsed and/or refractory MM. The article is a summary of the recent knowledge about the possibility of using elotuzumab in the treatment of relapsed and/or refractory MM and shows its potential uses in the future.

Immune Functions of Signaling Lymphocytic Activation Molecule Family Molecules in Multiple Myeloma

Simple Summary

Multiple myeloma (MM) is an incurable hematological malignancy characterized by an increase in abnormal plasma cells. Disease progression, drug resistance, and immunosuppression in MM are associated with immune-related molecules, such as immune checkpoint and co-stimulatory molecules, present in the tumor microenvironment. Novel agents targeting these cell-surface molecules are currently under development, including monoclonal antibodies, bispecific monoclonal antibodies, and chimera antigen receptor T-cell therapies. In this review, we focus on the signaling lymphocytic activation molecule family receptors and provide an overview of their biological functions and novel therapies in MM.

Abstract

The signaling lymphocytic activation molecule (SLAM) family receptors are expressed on various immune cells and malignant plasma cells in multiple myeloma (MM) patients. In immune cells, most SLAM family molecules bind to themselves to transmit co-stimulatory signals through the recruiting adaptor proteins SLAM-associated protein (SAP) or Ewing’s sarcoma-associated transcript 2 (EAT-2), which target immunoreceptor tyrosine-based switch motifs in the cytoplasmic regions of the receptors. Notably, SLAMF2, SLAMF3, SLAMF6, and SLAMF7 are strongly and constitutively expressed on MM cells that do not express the adaptor proteins SAP and EAT-2. This review summarizes recent studies on the expression and biological functions of SLAM family receptors during the malignant progression of MM and the resulting preclinical and clinical research involving four SLAM family receptors. A better understanding of the relationship between SLAM family receptors and MM disease progression may lead to the development of novel immunotherapies for relapse prevention.

An update on B-cell maturation antigen-targeted therapies in Multiple Myeloma

Introduction: B-cell maturation antigen (BCMA) targeted therapy (BCMA-TT) has emerged as a promising treatment for Multiple Myeloma (MM). the three most common treatment modalities for targeting BCMA are antibody-drug conjugates (ADCs), bispecific antibody constructs, including BiTE (bispecific T-cell engager) immuno-oncology therapies, and chimeric antigen receptor (CAR)-modified T-cell therapy.Areas covered: The review provides an overview of the main published studies on clinical and pre-clinical data from trials using BCMA-TT.Expert opinion: Despite progresses in survival outcomes and the availability of new drugs, MM remains an incurable disease. ADC is a promising antibody-based treatment and Belantamab mafodotin showed an anti-myeloma effect alone or in combination with other drugs. The major issue of ADC is the occurrence of events interfering with the efficacy and the off-target cytotoxicity. Bispecific antibody constructs are off-the-shelf therapies characterized by a potential rapid availability. The most critical limitation of bispecific antibody constructs is their short half-life necessitating prolonged intravenous infusion. CAR-T cells produced unprecedented results in heavily pretreated RRMM. The most common toxicities include neurologic toxicity and cytokine release syndrome, B-cell aplasia, cytopenias, and hypogammaglobulinemia. Further studies are needed to detect which are the eligible patients who could benefit from one treatment more than another.

Bortezomib, lenalidomide, and dexamethasone with or without elotuzumab in patients with untreated, high-risk multiple myeloma (SWOG-1211): primary analysis of a randomised, phase 2 trial

BACKGROUND

The introduction of immunomodulatory agents, proteasome inhibitors, and autologous haematopoietic stem-cell transplantation has improved outcomes for patients with multiple myeloma, but patients with high-risk multiple myeloma have a poor long-term prognosis. We aimed to address optimal treatment for these patients.

METHODS

SWOG-1211 is a randomised phase 2 trial comparing eight cycles of lenalidomide (25 mg orally on days 1-14 every 21 days), bortezomib (1·3 mg/m² subcutaneously on days 1, 4, 8, and 11 every 21 days), and dexamethasone (20 mg orally on days 1, 2, 4, 5, 8, 9, 11, and 12 every 21 days; RVd) induction followed by dose-attenuated RVd maintenance (bortezomib 1 mg/m² subcutaneously on days 1, 8, and 15; lenalidomide 15 mg orally on days 1-21; dexamethasone 12 mg orally on days 1, 18, and 15 every 28 days) until disease progression with or without elotuzumab (10 mg/kg intravenously on days 1, 8, and 15 for cycles 1-2, on days 1 and 11 for cycles 3-8, and on days 1 and 15 during maintenance). Patients were randomly assigned (1:1) to either RVd or RVd-elotuzumab. High-risk multiple myeloma was defined by one of the following: gene expression profiling high risk (GEP^hi), t(14;16), t(14;20), del(17p) or amp1q21, primary plasma cell leukaemia and elevated serum lactate dehydrogenase (two times the upper limit of normal or more). The primary endpoint was progression-free survival, and all analyses were done on intention-to-treat basis among eligible patients who were evaluable for response. This study is registered with ClinicalTrials.gov, NCT01668719.

FINDINGS

100 (RVd n=52, RVd-elotuzumab n=48) patients were enrolled between Oct 27, 2013, and May 15, 2016, across 26 cooperative group institutions in the USA. Median age was 64 years (IQR 57-70, range 36-85). 74 (75%) of 99 had International Staging System stage II or stage III disease, 47 (47%) of 99 had amp1q21, 37 (37%) of 100 had del17p, 11 (11%) of 100 had t(14;16), eight (9%) of 90 were GEP^hi, seven (7%) of 100 had primary plasma cell leukaemia, five (5%) of 100 had t(14;20), four (4%) of 100 had elevated serum lactate dehydrogenase, and 17 (17%) had two or more features. With a median follow-up of 53 months (IQR 46-59), no difference in median progression-free survival was observed (RVd 33·64 months [95% CI 19·55-not reached], RVd-elotuzumab 31·47 months [18·56-53·98]; hazard ratio 0·968 [80% CI 0·697-1·344]; one-sided p=0·45]. 37 (71%) of 52 patients in the RVd group and 37 (77%) of 48 in the RVd-elotuzumab group had grade 3 or worse adverse events. No significant differences in the safety profile were observed, although some notable results included grade 3-5 infections (four [8%] of 52 in the RVd group, eight [17%] of 48 in the RVd-elotuzumab group), sensory neuropathy (four [8%] of 52 in the RVd group, six [13%] of 48 in the RVd-elotuzumab group), and motor neuropathy (one [2%] of 52 in the RVd group, four [8%] of 48 in the RVd-elotuzumab group). There were no treatment-related deaths in the RVd group and one death in the RVd-elotuzumab group for which study treatment was listed as possibly contributing by the investigator.

INTERPRETATION

In the first randomised study of high-risk multiple myeloma reported to date, the addition of elotuzumab to RVd induction and maintenance did not improve patient outcomes. However, progression-free survival in both study groups exceeded the original statistical assumptions and supports the role for continuous proteasome inhibitors and immunomodulatory drug combination maintenance therapy for this patient population.

FUNDING

National Institutes of Health, National Cancer Institute, Bristol Myers Squibb, Celgene, Leukemia and Lymphoma Society.

Methylation of the Promoter Region of the Tight Junction Protein-1 by DNMT1 Induces EMT-like Features in Multiple Myeloma

The molecular alterations that initiate the development of multiple myeloma (MM) are not fully understood. Our results revealed that TJP1 was downregulated in MM and positively related to the overall survival of MM patients in The Cancer Genome Atlas (TCGA) database and patient samples. In parallel, cell adhesion capacity representing MM metastasis was decreased in MM patients compared with healthy samples, together with the significantly activated epithelial-to-mesenchymal transition (EMT) transcriptional-like patterns of MM cells. Further analyses demonstrated that TJP1 negatively regulated EMT and consequently positively regulated cell adhesion in MM from TCGA database and MM1s cells. Furthermore, the methylation level of each CpG site on the TJP1 promoter was negatively correlated with TJP1 expression levels. Quantitative real-time PCR and western blot assays demonstrated that methylase DNMT1 regulated the methylation of TJP1. Finally, treatment with a combination of the MM clinical medicine bortezomib, methylation inhibitor, or TJP1 overexpression significantly suppressed the viability and progression of tumor cells of MM orthotopic models. In summary, our results indicate that DNMT1 promotes the methylation of TJP1 promoter, thereby decreasing its expression and regulating the development of EMT-inhibited MM cell adhesion. Therefore, methylation of TJP1 is a potential therapeutic agent to prevent the progression of MM disease.

Cytotoxic T Cell Responses Induced by CS1/CRT Fusion DNA Vaccine in a Human Plasmacytoma Model

To date, multiple myeloma remains an incurable disease. Immunotherapy is an encouraging option in the development of multiple myeloma (MM) therapy. CS1 is a specific myeloma antigen, which is highly expressed in myeloma cells. Calreticulin (CRT) is a key determinant of cell death, which can influence antigen presentation and promote cellular phagocytic uptake. In the current study, we constructed a DNA vaccine encoding both CS1 and CRT. Our results show that the PcDNA3.1-CS1/CRT vaccine was able to induce cytotoxic T cell responses against myeloma cells in vivo, and the tumor growth was significantly suppressed in mice immunized with this vaccine. Therefore, our findings indicate that the CS1/CRT fusion DNA vaccine may represent a promising novel myeloma therapy, and the potential for combining the CS1/CRT vaccine with other myeloma treatments.

Development of [89Zr]DFO-elotuzumab for immunoPET imaging of CS1 in multiple myeloma

PURPOSE

Multiple myeloma (MM) is a bone marrow malignancy that remains mostly incurable. Elotuzumab is an FDA-approved therapeutic monoclonal antibody targeted to the cell surface glycoprotein CS1, which is overexpressed in MM cells. Identifying patients who will respond to CS1-targeted treatments such as elotuzumab requires the development of a companion diagnostic to assess the presence of CS1. Here, we evaluated [⁸⁹Zr]DFO-elotuzumab as a novel PET tracer for imaging CS1 expression in preclinical MM models.

METHODS

Conjugation of desferrioxamine-p-benzyl-isothiocyanate (DFO-Bz-NCS) to elotuzumab enabled zirconium-89 radiolabeling. MM.1S-CG cells were intravenously injected in NOD SCID gamma (NSG) mice. Small animal PET imaging with [⁸⁹Zr]DFO-elotuzumab (1.11 MBq/mouse, 7 days post-injection), [⁸⁹Zr]DFO-IgG (1.11 MBq/mouse, 7 days post-injection), and [¹⁸F]FDG (7-8 MBq, 1 h post-injection) was performed. Additionally, biodistribution of [⁸⁹Zr]DFO-elotuzumab post-imaging at 7 days was also done. In vivo specificity of [⁸⁹Zr]DFO-elotuzumab was further evaluated with a blocking study and ex vivo autoradiography.

RESULTS

[⁸⁹Zr]DFO-elotuzumab was produced with high specific activity (56 ± 0.75 MBq/nmol), radiochemical purity (99% ± 0.5), and yield (93.3% ± 1.5). Dissociation constant of 40.4 nM and receptor density of 126 fmol/mg was determined in MM.1S-CG cells. Compared to [⁸⁹Zr]DFO-IgG, [⁸⁹Zr]DFO-elotuzumab localized with a significantly higher standard uptake value in tumor-bearing bone tissue (8.59 versus 4.77). Blocking with unlabeled elotuzumab significantly reduced (P < 0.05) uptake of [⁸⁹Zr]DFO-elotuzumab in the bones. Importantly, while [¹⁸F]FDG demonstrated similar uptake in the bone and muscle, [⁸⁹Zr]DFO-elotuzumab showed > 3-fold enhanced uptake in bones.

CONCLUSION

These data demonstrate the feasibility of [⁸⁹Zr]DFO-elotuzumab as a companion diagnostic for CS1-targeted therapies.

VIS832, a novel CD138-targeting monoclonal antibody, potently induces killing of human multiple myeloma and further synergizes with IMiDs or bortezomib in vitro and in vivo

Therapeutically targeting CD138, a define multiple myeloma (MM) antigen, is not yet approved for patients. We here developed and determined the preclinical efficacy of VIS832, a novel therapeutic monoclonal antibody (MoAb) with differentiated CD138 target binding to BB4 that is anti-CD138 MoAb scaffold for indatuximab ravtansine (BT062). VIS832 demonstrated enhanced CD138-binding avidity and significantly improved potency to kill MM cell lines and autologous patient MM cells regardless of resistance to current standard-of-care therapies, via robust antibody-dependent cellular cytotoxicity and phagocytosis mediated by NK and macrophage effector cells, respectively. Specifically, CD38-targeting daratumumab-resistant MM cells were highly susceptible to VIS832 which, unlike daratumumab, spares NK cells. Superior maximal cytolysis of VIS832 vs. daratumumab corresponded to higher CD138 vs. CD38 levels in MM cells. Furthermore, VIS832 acted synergistically with lenalidomide or bortezomib to deplete MM cells. Importantly, VIS832 at a sub-optimal dose inhibited disseminated MM1S tumors in vivo as monotherapy (P < 0.0001), and rapidly eradicated myeloma burden in all mice concomitantly receiving bortezomib, with 100% host survival. Taken together, these data strongly support clinical development of VIS832, alone and in combination, for the therapeutic treatment of MM in relapsed and refractory patients while pointing to its potential therapeutic use earlier in disease intervention.

Monoclonal Antibodies to Treat Multiple Myeloma: A Dream Come True

Immunotherapy is increasingly used in the treatment of multiple myeloma (MM). Monoclonal antibodies (mAbs) are safe and effective ways to elicit immunotherapeutic responses. In 2015, daratumumab has become the first mAb approved by the Food and Drug Administration for clinical use in MM and, in the last 5 years, a lot of clinical and preclinical research has been done to optimize the use of this drug class. Currently, mAbs have already become part of standard-of-care combinations for the treatment of relapsed/refractory MM and very soon they will also be used in the frontline setting. The success of simple mAbs ('naked mAbs') prompted the development of new types of molecules. Antibody-drug conjugates (ADCs) are tumor-targeting mAbs that release a cytotoxic payload into the tumor cells upon antigen binding in order to destroy them. Bispecific antibodies (BiAbs) are mAbs simultaneously targeting a tumor-associated antigen and an immune cell-associated antigen in order to redirect the immune cell cytotoxicity against the tumor cell. These different constructs produced solid preclinical data and promising clinical data in phase I/II trials. The aim of this review article is to summarize all the recent developments in the field, including data on naked mAbs, ADCs and BiAbs.

Monoclonal antibodies as an addition to current myeloma therapy strategies

INTRODUCTION

Immunotherapy has emerged as a major class in the therapeutic arsenal of multiple myeloma. Cell-based immunotherapy (CAR T-cells) and monoclonal antibody-based immunotherapy (naked monoclonal antibodies, antibody-drug conjugates, and bispecific T-cell engagers) are the two cornerstones of this novel approach for myeloma patients. Among numerous targets evaluated in the previous decade; CD38, SLAMF7, and, more recently, BCMA stand as the most promising.

AREAS COVERED

This review presents and discusses the currently available data regarding monoclonal antibodies in the treatment of multiple myeloma.

EXPERT OPINION

Anti-CD38-naked monoclonal antibodies have become a standard-of-care in multiple myeloma, greatly improving the depth and duration of response when combined with conventional therapy. Elotuzumab is approved in the relapse setting in combination with pomalidomide and maybe an interesting option in patients whose disease became refractory to anti-CD38 monoclonal antibodies. Anti-BCMA drug conjugates and bispecific T-cell engager antibodies are promising new molecules in the multiple myeloma armamentarium.

Development of CAR T Cells Expressing a Suicide Gene Plus a Chimeric Antigen Receptor Targeting Signaling Lymphocytic-Activation Molecule F7

Chimeric antigen receptors (CARs) are fusion proteins that contain antigen-recognition domains and T cell signaling domains. Signaling lymphocytic-activation molecule F7 (SLAMF7) is a promising target for CAR T cell therapies of the plasma cell malignancy multiple myeloma (MM) because SLAMF7 is expressed by MM but not normal nonhematopoietic cells. We designed CARs targeting SLAMF7. We transduced human T cells with anti-SLAMF7 CARs containing either CD28 or 4-1BB costimulatory domains. T cells expressing CD28-containing CARs or 4-1BB-containing CARs recognized SLAMF7 in vitro. SLAMF7-specific cytokine release was higher for T cells expressing CARs with CD28 versus 4-1BB domains. In murine solid tumor and disseminated tumor models, anti-tumor activity of T cells was superior with CD28-containing CARs versus 4-1BB-containing CARs. Because of SLAMF7 expression on some normal leukocytes, especially natural killer cells that control certain viral infections, the inclusion of a suicide gene with an anti-SLAMF7 CAR is prudent. We designed a construct with a CD28-containing anti-SLAMF7 CAR and a suicide gene. The suicide gene encoded a dimerization domain fused to a caspase-9 domain. T cells expressing the anti-SLAMF7 CAR plus suicide-gene construct specifically recognized SLAMF7 in vitro and eliminated tumors from mice. T cells expressing this construct were eliminated on demand by administering the dimerizing agent AP1903 (rimiducid).

Old and new generation immunomodulatory drugs in multiple myeloma

INTRODUCTION

Over the last two decades, the outcomes of patients with multiple myeloma (MM), a malignant plasma cells dyscrasia, have dramatically improved. The development and the introduction of the immunomodulatory drugs (IMiDs) which include thalidomide, lenalidomide, and pomalidomide, have contributed significantly to these improvements.

EVIDENCE ACQUISITION

The IMiDs have been shown a multitude of mechanisms of action, including antiangiogenic, cytotoxic and immunomodulatory. The more recent discoveries that the IMiDs bind to cereblon and thus regulate the ubiquitination of key transcription factors including IKZF1 and IKZF3, have provided new insight about their activities.

EVIDENCE SYNTHESIS

The IMIDs are widely used in the treatment of the different setting of MM patients and particularly lenalidomide represents the backbone in the therapy of newly diagnosed transplant eligible and transplant ineligible patients, in the maintenance setting post-transplant and in the relapsed/refractory setting, while pomalidomide is currently utilized in the relapsed/refractory setting.

CONCLUSIONS

Here the mechanisms of action, the clinical efficacy and the management of side effects are reviewed as well as the new classes of cereblon E3 ligase modulator (CELMoD) and their promising clinical data are described.

Chimeric Antigen Receptor T-cell Therapy for Multiple Myeloma

Relapsed/refractory multiple myeloma (MM) remains a significant clinical challenge, despite a wide array of approved therapeutic agents. Immunotherapy offers an advantage in this setting. Chimeric antigen receptor (CAR) modified T-cells have transformed care for patients with hematologic malignancies. CAR-T cells targeting CD-19 B-cell lymphoma cells have shown prominent activity in lymphoma and acute lymphoblastic leukemia. Recently, the CAR-T cell platform for MM demonstrated therapeutic benefit. Hence, it is rapidly progressing. The most commonly tested target for MM is the B-cell maturation antigen. Complexities involved in the generation and use of CAR-T cells for MM include the identification of appropriate target antigens that are specific, and tumor type restricted, in addition to the optimization of CAR constructs to mitigate toxicities including cytokine release syndrome. CAR-T cells hold immense promise as a therapeutic modality for the treatment of MM. In this article, we provide an updated review of clinical trials of MM-specific CAR-T cells.

Elotuzumab, lenalidomide, and dexamethasone in RRMM: final overall survival results from the phase 3 randomized ELOQUENT-2 study

Prolonging overall survival (OS) remains an unmet need in relapsed or refractory multiple myeloma (RRMM). In ELOQUENT-2 (NCT01239797), elotuzumab plus lenalidomide/dexamethasone (ERd) significantly improved progression-free survival (PFS) versus lenalidomide/dexamethasone (Rd) in patients with RRMM and 1–3 prior lines of therapy (LoTs). We report results from the pre-planned final OS analysis after a minimum follow-up of 70.6 months, the longest reported for an antibody-based triplet in RRMM. Overall, 646 patients with RRMM and 1–3 prior LoTs were randomized 1:1 to ERd or Rd. PFS and overall response rate were co-primary endpoints. OS was a key secondary endpoint, with the final analysis planned after 427 deaths. ERd demonstrated a statistically significant 8.7-month improvement in OS versus Rd (median, 48.3 vs 39.6 months; hazard ratio, 0.82 [95.4% Cl, 0.68–1.00]; P = 0.0408 [less than allotted α of 0.046]), which was consistently observed across key predefined subgroups. No additional safety signals with ERd at extended follow-up were reported. ERd is the first antibody-based triplet regimen shown to significantly prolong OS in patients with RRMM and 1–3 prior LoTs. The magnitude of OS benefit was greatest among patients with adverse prognostic factors, including older age, ISS stage III, IMWG high-risk disease, and 2–3 prior LoTs.

Novel Approaches to Improve Myeloma Cell Killing by Monoclonal Antibodies

The monoclonal antibodies (mAbs) have significantly changed the treatment of multiple myeloma (MM) patients. However, despite their introduction, MM remains an incurable disease. The mAbs currently used for MM treatment were developed with different mechanisms of action able to target antigens, such as cluster of differentiation 38 (CD38) and SLAM family member 7 (SLAMF7) expressed by both, MM cells and the immune microenvironment cells. In this review, we focused on the mechanisms of action of the main mAbs approved for the therapy of MM, and on the possible novel approaches to improve MM cell killing by mAbs. Actually, the combination of anti-CD38 or anti-SLAMF7 mAbs with the immunomodulatory drugs significantly improved the clinical effect in MM patients. On the other hand, pre-clinical evidence indicates that different approaches may increase the efficacy of mAbs. The use of trans-retinoic acid, the cyclophosphamide or the combination of anti-CD47 and anti-CD137 mAbs have given the rationale to design these types of combinations therapies in MM patients in the future. In conclusion, a better understanding of the mechanism of action of the mAbs will allow us to develop novel therapeutic approaches to improve their response rate and to overcome their resistance in MM patients.

Antibody-drug conjugates for multiple myeloma

Introduction: Antibody-drug conjugates (ADC) are a new class of treatment for multiple myeloma (MM) patients, delivering a potent cytotoxic agent directly to the myeloma cell. The target is defined by the specificity of the monoclonal antibody which is linked to the cytotoxic agent. This mechanism of action minimizes bystander cell injury and allows a favorable therapeutic window.Areas covered: This review describes the rationale, pre- and clinical data for ADCs that have been and are currently in development for MM. As the treatment landscape for MM rapidly evolves, the treatment paradigm and a description of novel agents in development including immunotherapies are provided to understand how ADCs may fit in the pathway.Expert opinion: ADCs have a significant potential for the treatment for MM. As they are 'off the shelf' treatments, they can be used across nearly all MM treatment centers and to a wide range of patients. Some ADCs have specific adverse events that may require specialist input to optimally manage. The most clinically advanced ADC is belantamab mafodotin which has demonstrated clinically meaningful responses in patients with heavily pre-treated MM. Additionally, it is being combined with standard of care agents and at earlier lines of treatment.

A novel BCMA PBD-ADC with ATM/ATR/WEE1 inhibitors or bortezomib induce synergistic lethality in multiple myeloma

To target mechanisms critical for multiple myeloma (MM) plasma cell adaptations to genomic instabilities and further sustain MM cell killing, we here specifically trigger DNA damage response (DDR) in MM cells by a novel BCMA antibody-drug conjugate (ADC) delivering the DNA cross-linking PBD dimer tesirine, MEDI2228. MEDI2228, more effectively than its anti-tubulin MMAF-ADC homolog, induces cytotoxicity against MM cells regardless of drug resistance, BCMA levels, p53 status, and the protection conferred by bone marrow stromal cells and IL-6. Distinctly, prior to apoptosis, MEDI2228 activates DDRs in MM cells via phosphorylation of ATM/ATR kinases, CHK1/2, CDK1/2, and H2AX, associated with expression of DDR-related genes. Significantly, MEDI2228 synergizes with DDR inhibitors (DDRi s) targeting ATM/ATR/WEE1 checkpoints to induce MM cell lethality. Moreover, suboptimal doses of MEDI2228 and bortezomib (btz) synergistically trigger apoptosis of even drug-resistant MM cells partly via modulation of RAD51 and accumulation of impaired DNA. Such combination further induces superior in vivo efficacy than monotherapy via increased nuclear γH2AX-expressing foci, irreversible DNA damages,  and tumor cell death, leading to significantly prolonged host survival. These results indicate leveraging MEDI2228 with DDRi s or btz as novel combination strategies, further supporting ongoing clinical development of MEDI2228 in patients with relapsed and refractory MM.

CAR T-Cells in Multiple Myeloma: State of the Art and Future Directions

Despite recent therapeutic advances, the prognosis of multiple myeloma (MM) patients remains poor. Thus, new strategies to improve outcomes are imperative. Chimeric antigen receptor (CAR) T-cell therapy has changed the treatment landscape of B-cell malignancies, providing a potentially curative option for patients who are refractory to standard treatment. Long-term remissions achieved in patients with acute lymphoblastic leukemia and Non-Hodgkin Lymphoma encouraged its further development in MM. B-cell maturation antigen (BCMA)-targeted CAR T-cells have established outstanding results in heavily pre-treated patients. However, several other antigens such as SLAMF7 and CD44v6 are currently under investigation with promising results. Idecabtagene vicleucel is expected to be approved soon for clinical use. Unfortunately, relapses after CAR T-cell infusion have been reported. Hence, understanding the underlying mechanisms of resistance is essential to promote prevention strategies and to enhance CAR T-cell efficacy. In this review we provide an update of the most recent clinical and pre-clinical data and we elucidate both, the potential and the challenges of CAR T-cell therapy in the future.

Model-Based Determination of Elotuzumab Pharmacokinetics in Japanese Patients With Multiple Myeloma Incorporating Time-Varying M Protein

A population pharmacokinetic model was developed to evaluate the effects of Japanese ethnicity, prior line of therapy (0 or ≥1), time-varying M protein, and maintenance dosing regimens (10 mg/kg intravenously every 2 weeks or 20 mg/kg intravenously every 4 weeks beginning in cycle 19) on the pharmacokinetics of elotuzumab in patients with multiple myeloma treated with elotuzumab plus lenalidomide/dexamethasone. Elotuzumab pharmacokinetics were characterized by a 2-compartment model with parallel linear (nonspecific) and Michaelis-Menten elimination from the central compartment and target-mediated elimination from the peripheral compartment. Asian race on nonspecific clearance (CL) and central volume of distribution, prior line of therapy on CL, and maximum target-mediated elimination rate (V_max ) were statistically significant but not considered clinically relevant (magnitude < 20%). Time-varying M protein on V_max was statistically significant, and the magnitude was >20%; however, clinical implications in the setting of combination therapy were not expected. Model-predicted steady-state elotuzumab exposure in cycle 12 were similar in Japanese and non-Japanese patients and in Japanese patients with 0 and ≥1 prior lines of therapy. Elotuzumab 20 mg/kg intravenously every 4 weeks beginning in cycle 19 produced time-averaged concentrations similar to elotuzumab 10 mg/kg intravenously every 2 weeks, although maximum and minimum concentrations after elotuzumab 20 mg/kg intravenous every-4-week dosing were slightly higher and lower, respectively. In conclusion, the current analysis demonstrates that Japanese ethnicity, prior line of therapy, time-varying M protein, and change in elotuzumab dosing regimen in cycle 19 have no clinically meaningful impact on elotuzumab pharmacokinetics and exposure in Japanese patients with multiple myeloma.

Roles of NK Cell Receptors 2B4 (CD244), CS1 (CD319), and LLT1 (CLEC2D) in Cancer

Natural killer (NK) cells play a pivotal role in the immune system, especially in the recognition and clearance of cancer cells and infected cells. Their effector function is controlled by a delicate balance between the activating and inhibitory signals. We have identified 2B4 (CD244, SLAMF4) and CS1 (CD319, SLAMF7) as NK cell receptors regulating NK cell cytotoxicity. Lectin-like transcript 1 (LLT1), a member of the C-type lectin-like domain family 2 (CLEC2D), induced IFN-γ production but did not directly regulate cytolytic activity. Interestingly, LLT1 expressed on other cells acts as a ligand for an NK cell inhibitory receptor NKRP1A (CD161) and inhibits NK cytolytic function. Extensive research has been done on novel therapies that target these receptors to increase the effector function of NK cells. The 2B4 receptor is involved in the rejection of melanoma cells in mice. Empliciti, an FDA-approved monoclonal antibody, explicitly targets the CS1 receptor and enhances the NK cell cytotoxicity against multiple myeloma cells. Our studies revealed that LLT1 is expressed on prostate cancer and triple-negative breast cancer cells and allows them to evade NK-cell-mediated killing. In this review, we describe NK cell receptors 2B4, CS1, and LLT1 and their potential in targeting cancer cells for NK-cell-mediated immunotherapy. New cancer immunotherapies like chimeric antigen receptor T (CAR-T) and NK (CAR-NK) cells are showing great promise in the treatment of cancer, and CAR cells specific to these receptors would be an attractive therapeutic option.

Checkpoint Inhibitors and Engineered Cells: New Weapons for Natural Killer Cell Arsenal Against Hematological Malignancies

Natural killer (NK) cells represent one of the first lines of defense against malignant cells. NK cell activation and recognition are regulated by a balance between activating and inhibitory receptors, whose specific ligands can be upregulated on tumor cells surface and tumor microenvironment (TME). Hematological malignancies set up an extensive network of suppressive factors with the purpose to induce NK cell dysfunction and impaired immune-surveillance ability. Over the years, several strategies have been developed to enhance NK cells-mediated anti-tumor killing, while other approaches have arisen to restore the NK cell recognition impaired by tumor cells and other cellular components of the TME. In this review, we summarize and discuss the strategies applied in hematological malignancies to block the immune check-points and trigger NK cells anti-tumor effects through engineered chimeric antigen receptors.

Role of the Bone Marrow Milieu in Multiple Myeloma Progression and Therapeutic Resistance

Multiple myeloma (MM) is a cancer of the plasma cells within the bone marrow (BM). Studies have shown that the cellular and noncellular components of the BM milieu, such as cytokines and exosomes, play an integral role in MM pathogenesis and progression by mediating drug resistance and inducing MM proliferation. Moreover, the BM microenvironment of patients with MM facilitates cancer tolerance and immune evasion through the expansion of regulatory immune cells, inhibition of antitumor effector cells, and disruption of the antigen presentation machinery. These are of special relevance, especially in the current era of cancer immunotherapy. An improved understanding of the supportive role of the MM BM microenvironment will allow for the development of future therapies targeting MM in the context of the BM milieu to elicit deeper and more durable responses. In the present review, we have discussed our current understanding of the role of the BM microenvironment in MM progression and resistance to therapy and discuss novel potential approaches to alter its pro-MM function.

BCMA-Targeting Therapy: Driving a New Era of Immunotherapy in Multiple Myeloma

The treatment of multiple myeloma (MM) has entered into a new era of immunotherapy. Novel immunotherapies will significantly improve patient outcome via simultaneously targeting malignant plasma cell (PC) and reversing immunocompromised bone marrow (BM) microenvironment. B-cell maturation antigen (BCMA), selectively expressed in PCs and a key receptor for A proliferation-inducing ligand (APRIL), is highly expressed in MM cells from patients at all stages. The APRIL/BCMA signal cascades promote the survival and drug resistance of MM cells and further modulate immunosuppressive BM milieu. Impressively, anti-BCMA immunotherapeutic reagents, including chimeric antigen receptor (CAR), antibody-drug conjugate (ADC) and bispecific T cell engager (BiTE) have all shown high response rates in their first clinical trials in relapse and refractory patients with very limited treatment options. These results rapidly inspired numerous development of next-generation anti-BCMA biotherapeutics, i.e., bispecific molecule, bispecific or trispecific antibodies, a novel form of CAR T/NK cells and T Cell Antigen Coupler (TAC) receptors, antibody-coupled T cell receptor (ACTR) as well as a cancer vaccine. We here highlight seminal preclinical and clinical studies on novel BCMA-based immunotherapies as effective monotherapy and discuss their potential in combination with current anti-MM and novel checkpoint drugs in earlier disease stages to further achieve durable responses in patients.

Preclinical Characterization of an Antibody-Drug Conjugate Targeting CS-1 and the Identification of Uncharacterized Populations of CS-1-Positive Cells

Multiple myeloma is a hematologic cancer that disrupts normal bone marrow function and has multiple lines of therapeutic options, but is incurable as patients ultimately relapse. We developed a novel antibody-drug conjugate (ADC) targeting CS-1, a protein that is highly expressed on multiple myeloma tumor cells. The anti-CS-1 mAb specifically bound to cells expressing CS-1 and, when conjugated to a cytotoxic pyrrolobenzodiazepine payload, reduced the viability of multiple myeloma cell lines in vitro In mouse models of multiple myeloma, a single administration of the CS-1 ADC caused durable regressions in disseminated models and complete regression in a subcutaneous model. In an exploratory study in cynomolgus monkeys, the CS-1 ADC demonstrated a half-life of 3 to 6 days; however, no highest nonseverely toxic dose was achieved, as bone marrow toxicity was dose limiting. Bone marrow from dosed monkeys showed reductions in progenitor cells as compared with normal marrow. In vitro cell killing assays demonstrated that the CS-1 ADC substantially reduced the number of progenitor cells in healthy bone marrow, leading us to identify previously unreported CS-1 expression on a small population of progenitor cells in the myeloid-erythroid lineage. This finding suggests that bone marrow toxicity is the result of both on-target and off-target killing by the ADC.