Monoclonal and Bispecific Anti-BCMA Antibodies in Multiple Myeloma

Multi-omics reveal immune microenvironment alterations in multiple myeloma and its precursor stages

Tumor immune microenvironmental alterations occur early in multiple myeloma (MM) development. In this study, we aim to systematically characterize the tumor immune microenvironment (TME) and the tumor-immune interactions from precursor stages, i.e., monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM), to newly diagnosed MM, comparing these to healthy donors. Using CIBERSORT, mass cytometry (CyTOF), and single-cell RNA sequencing (scRNA-Seq), we examined innate and adaptive immune changes across these stages. We found a decrease in granulocytes in the TME predicts MM outcomes. HLA-DR is reduced in CD16+ monocytes and plasmacytoid dendritic cells, while myeloid dendritic cells show decreased expression of stress and immune-response genes. NK cells and CD8+ T cells shift from a GZMK+ to a GZMB+ cytotoxic phenotype in the TME, with increased inhibitory markers TIM3 and TIGIT. In paired samples, the proportion and gene expression pattern in patient-specific GZMB+CD8+ T cells remain largely unchanged despite MM progression. Our findings provide a comprehensive immune landscape of MM and its precursors, offering insights into therapeutic strategies. Enhancing neutrophil and NK cell cytotoxicity, tumor antigen presentation, and CD8+ T cell versatility in precursor stages may prevent MM progression.

Development of a Bispecific IgG1 Antibody Targeting BCMA and PDL1

We designed, produced, and purified a novel IgG1-like, bispecific antibody (bsAb) directed against B-cell maturation antigen (BCMA), expressed by multiple myeloma (MM) cells, and an immune checkpoint inhibitor (ICI), PDL1, expressed in the MM microenvironment. The BCMA×PDL1 bsAb was fully characterized in vitro. BCMA×PDL1 bound specifically and simultaneously, with nM affinity, to both native membrane-bound antigens and to the recombinant soluble antigen fragments, as shown by immunophenotyping analyses and surface plasmon resonance (SPR), respectively. The binding affinity of bsAb for PDL1 and BCMA was similar to each other, but PDL1 affinity was about 10-fold lower in the bsAb compared to parent mAb, probably due to the steric hindrance associated with the more internal anti-PDL1 Fab. The bsAb was also able to functionally block both antigen targets with IC50 in the nM range. The bsAb Fc was functional, inducing human-complement-dependent cytotoxicity as well as ADCC by NK cells in 24 h killing assays. Finally, BCMA×PDL1 was effective in 7-day killing assays with peripheral blood mononuclear cells as effectors, inducing up to 75% of target MM cell line killing at a physiologically attainable, 6 nM, concentration. These data provide the necessary basis for future optimization and in vivo testing of this novel bsAb.

Good Cop, Bad Cop: Profiling the Immune Landscape in Multiple Myeloma

Multiple myeloma (MM) is a dyscrasia of plasma cells (PCs) characterized by abnormal immunoglobulin (Ig) production. The disease remains incurable due to a multitude of mutations and structural abnormalities in MM cells, coupled with a favorable microenvironment and immune suppression that eventually contribute to the development of drug resistance. The bone marrow microenvironment (BMME) is composed of a cellular component comprising stromal cells, endothelial cells, osteoclasts, osteoblasts, and immune cells, and a non-cellular component made of the extracellular matrix (ECM) and the liquid milieu, which contains cytokines, growth factors, and chemokines. The bone marrow stromal cells (BMSCs) are involved in the adhesion of MM cells, promote the growth, proliferation, invasion, and drug resistance of MM cells, and are also crucial in angiogenesis and the formation of lytic bone lesions. Classical immunophenotyping in combination with advanced immune profiling using single-cell sequencing technologies has enabled immune cell-specific gene expression analysis in MM to further elucidate the roles of specific immune cell fractions from peripheral blood and bone marrow (BM) in myelomagenesis and progression, immune evasion and exhaustion mechanisms, and development of drug resistance and relapse. The review describes the role of BMME components in MM development and ongoing clinical trials using immunotherapeutic approaches.

Serum soluble BCMA can be used to monitor relapse of multiple myeloma patients after chimeric antigen receptor T-cell immunotherapy

PURPOSE

Chimeric antigen receptor T-cell (CAR-T) therapy has been proven very effective in treating hematologic malignancies. Ciltacabtagene autoleucel (cilta-cel), a second-generation CAR-T cell with double B cell maturation antigen (BCMA) targeting binding domains, showed an 88% overall response rate (ORR) in patients with relapsed/refractory multiple myeloma (MM), which were carried out in our institute. This study aimed to assess the prognostic potential of soluble BCMA (sBCMA) in serum as a biomarker in MM after CAR-T therapy.

PATIENTS AND METHODS

Serum samples (n = 44) from MM patients were collected before and after CAR-T therapy. The level of sBCMA was analyzed by enzyme-linked immunosorbent assay (ELISA). Additionally, three patients' long-term longitudinal analysis were performed.

RESULTS

Serum sBCMA level was correlated with the percentage of malignant plasma cells in bone marrow (r = 0.613). After CAR-T infusion, the sBCMA level in serum of MM patients decreased markedly (median: 508,513 pg/mL before CAR-T infusion, 89,198 pg/mL in the first month, 8448 pg/mL in the second months, and 6010 pg/mL in the third month after CAR-T infusion). In patients who obtained objective response (≥ PR), re-elevated sBCMA indicated the possibility of disease recurrence. At a cutoff 69,326.27 pg/mL, sBCMA shows high sensitivity (87.5%) and specificity (88.5%) for identifying relapse of MM after CAR-T therapy.

CONCLUSION

Our results suggested that serum sBCMA level changes in response to the clinical status of MM patients after anti-BCMA CAR-T therapy. Furthermore, sBCMA may be a auxiliary biomarker for disease monitoring in MM patients after CAR-T therapy.

Innovation in BCMA CAR-T therapy: Building beyond the Model T

Autologous chimeric antigen receptor T-cell (CAR-T) therapies targeting B-cell maturation antigen (BCMA) have revolutionized the field of multiple myeloma in the same way that the Ford Model T revolutionized the original CAR world a century ago. However, we are only beginning to understand how to improve the efficacy and usability of these cellular therapies. In this review, we explore three automotive analogies for innovation with BCMA CAR-T therapies: stronger engines, better mileage, and hassle-free delivery. Firstly, we can build stronger engines in terms of BCMA targeting: improved antigen binding, tools to modulate antigen density, and armoring to better reach the antigen itself. Secondly, we can improve "mileage" in terms of response durability through ex vivo CAR design and in vivo immune manipulation. Thirdly, we can implement hassle-free delivery through rapid manufacturing protocols and off-the-shelf products. Just as the Model T set a benchmark for car manufacturing over 100 years ago, idecabtagene vicleucel and ciltacabtagene autoleucel have now set the starting point for BCMA CAR-T therapy with their approvals. As with any emerging technology, whether automotive or cellular, the best in innovation and optimization is yet to come.

Targeting the Microenvironment for Treating Multiple Myeloma

Multiple myeloma (MM) is a malignant, incurable disease characterized by the expansion of monoclonal terminally differentiated plasma cells in the bone marrow. MM is consistently preceded by an asymptomatic monoclonal gammopathy of undetermined significance, and in the absence of myeloma defining events followed by a stage termed smoldering multiple myeloma (SMM), which finally progresses to active myeloma if signs of organ damage are present. The reciprocal interaction between tumor cells and the tumor microenvironment plays a crucial role in the development of MM and the establishment of a tumor-promoting stroma facilitates tumor growth and myeloma progression. Since myeloma cells depend on signals from the bone marrow microenvironment (BMME) for their survival, therapeutic interventions targeting the BMME are a novel and successful strategy for myeloma care. Here, we describe the complex interplay between myeloma cells and the cellular components of the BMME that is essential for MM development and progression. Finally, we present BMME modifying treatment options such as anti-CD38 based therapies, immunomodulatory drugs (IMiDs), CAR T-cell therapies, bispecific antibodies, and antibody-drug conjugates which have significantly improved the long-term outcome of myeloma patients, and thus represent novel therapeutic standards.

Current State of the Art and Prospects of T Cell-Redirecting Bispecific Antibodies in Multiple Myeloma

Multiple myeloma (MM) patients eventually develop multi-drug-resistant disease with poor survival. Hence, the development of novel treatment strategies is of great importance. Recently, different classes of immunotherapeutic agents have shown great promise in heavily pre-treated MM, including T cell-redirecting bispecific antibodies (BsAbs). These BsAbs simultaneously interact with CD3 on effector T cells and a tumor-associated antigen on MM cells, resulting in redirection of T cells to MM cells. This leads to the formation of an immunologic synapse, the release of granzymes/perforins, and subsequent tumor cell lysis. Several ongoing phase 1 studies show substantial activity and a favorable toxicity profile with BCMA-, GPRC5D-, or FcRH5-targeting BsAbs in heavily pre-treated MM patients. Resistance mechanisms against BsAbs include tumor-related features, T cell characteristics, and impact of components of the immunosuppressive tumor microenvironment. Various clinical trials are currently evaluating combination therapy with a BsAb and another agent, such as a CD38-targeting antibody or an immunomodulatory drug (e.g., pomalidomide), to further improve response depth and duration. Additionally, the combination of two BsAbs, simultaneously targeting two different antigens to prevent antigen escape, is being explored in clinical studies. The evaluation of BsAbs in earlier lines of therapy, including newly diagnosed MM, is warranted, based on the efficacy of BsAbs in advanced MM.

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.

CART-Cell Therapy: Recent Advances and New Evidence in Multiple Myeloma

Despite the improvement in survival outcomes, multiple myeloma (MM) remains an incurable disease. Chimeric antigen receptor (CAR) T-cell therapy targeting B-cell maturation antigen (BCMA) represents a new strategy for the treatment of relapsed/refractory MM (R/R). In this paper, we describe several recent advances in the field of anti-BCMA CAR T-cell therapy and MM. Currently, available data on anti-BCMA CART-cell therapy has demonstrated efficacy and manageable toxicity in heavily pretreated R/R MM patients. Despite this, the main issues remain to be addressed. First of all, a significant proportion of patients eventually relapse. The potential strategy to prevent relapse includes sequential or combined infusion with CAR T-cells against targets other than BCMA, CAR T-cells with novel dual-targeting vector design, and BCMA expression upregulation. Another dark side of CART therapy is safety. Cytokine release syndrome (CRS) andneurologic toxicity are well-described adverse effects. In the MM trials, most CRS events tended to be grade 1 or 2, with fewer patients experiencing grade 3 or higher. Another critical point is the extended timeline of the manufacturing process. Allo-CARs offers the potential for scalable manufacturing for on-demand treatment with shorter waiting days. Another issue is undoubtedly going to be access to this therapy. Currently, only a few academic centers can perform these procedures. Recognizing these issues, the excellent response with BCMA-targeted CAR T-cell therapy makes it a treatment strategy of great promise.

Immunotherapy in Acute Myeloid Leukemia: Where We Stand

In the past few years, our improved knowledge of acute myeloid leukemia (AML) pathogenesis has led to the accelerated discovery of new drugs and the development of innovative therapeutic approaches. The role of the immune system in AML development, growth and recurrence has gained increasing interest. A better understanding of immunological escape and systemic tolerance induced by AML blasts has been achieved. The extraordinary successes of immune therapies that harness the power of T cells in solid tumors and certain hematological malignancies have provided new stimuli in this area of research. Accordingly, major efforts have been made to develop immune therapies for the treatment of AML patients. The persistence of leukemia stem cells, representing the most relevant cause of relapse, even after allogeneic stem cell transplant (allo-SCT), remains a major hurdle in the path to cure for AML patients. Several clinical trials with immune-based therapies are currently ongoing in the frontline, relapsed/refractory, post-allo-SCT and minimal residual disease/maintenance setting, with the aim to improve survival of AML patients. This review summarizes the available data with immune-based therapeutic modalities such as monoclonal antibodies (naked and conjugated), T cell engagers, adoptive T-cell therapy, adoptive-NK therapy, checkpoint blockade via PD-1/PD-L1, CTLA4, TIM3 and macrophage checkpoint blockade via the CD47/SIRPa axis, and leukemia vaccines. Combining clinical results with biological immunological findings, possibly coupled with the discovery of biomarkers predictive for response, will hopefully allow us to determine the best approaches to immunotherapy in AML.

Novel Experimental Drugs for Treatment of Multiple Myeloma

Multiple myeloma (MM) is the second most frequent hematological malignancy characterized by bone marrow aberrant plasma cells proliferation leading to a genetic complex and heterogeneous disease, with a median survival ranging from two to more than 10 years. By using new drugs such as proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), monoclonal antibodies (mAbs) in different combinations and high-dose therapy followed by auto-transplantation, there has been an amazing improvement in the outcome of this disease in recent years. Despite this, MM is still considered an incurable disease, characterized by remission periods alternated with relapse/progression episodes finally leading to resistant disease. In particular, patients who become refractory to PIs, IMiDs and mAbs have a very poor outcome. Moreover, to overcome resistant residual disease, a large combination of drugs will be increasingly used in early lines of therapy; this further reduces the therapeutic options at each relapse. This natural history means that MM always needs new drugs/strategies to overcome the incoming resistance. New combinations of naked mAbs are becoming the therapy of choice for patients refractory to lenalidomide and/or PI; conjugated mAbs will be useful in triple- and more-refractory patients; CAR-T cells and bispecific mAbs have shown relevant results in very advanced stages of disease. In this review, we reported the results of these new therapies and explored their potential applications. Personalized and precision medicine seem to be the new frontier of cancer treatment. Although no single or few factors have been identified as disease drivers in MM, recurrent gene mutations were recognized and specific compounds targeting these alterations were developed and studied. Therefore, we reviewed these targeted drugs to try to understand what the best therapeutic strategy in MM is.