Pursuing a Curative Approach in Multiple Myeloma: A Review of New Therapeutic Strategies

CAR T therapies in multiple myeloma: unleashing the future

In recent years, the field of cancer treatment has witnessed remarkable breakthroughs that have revolutionized the landscape of care for cancer patients. While traditional pillars such as surgery, chemotherapy, and radiation therapy have long been available, a cutting-edge therapeutic approach called CAR T-cell therapy has emerged as a game-changer in treating multiple myeloma (MM). This novel treatment method complements options like autologous stem cell transplants and immunomodulatory medications, such as proteasome inhibitors, by utilizing protein complexes or anti-CD38 antibodies with potent complement-dependent cytotoxic effects. Despite the challenges and obstacles associated with these treatments, the recent approval of the second FDA multiple myeloma CAR T-cell therapy has sparked immense promise in the field. Thus far, the results indicate its potential as a highly effective therapeutic solution. Moreover, ongoing preclinical and clinical trials are exploring the capabilities of CAR T-cells in targeting specific antigens on myeloma cells, offering hope for patients with relapsed/refractory MM (RRMM). These advancements have shown the potential for CAR T cell-based medicines or combination therapies to elicit greater treatment responses and minimize side effects. In this context, it is crucial to delve into the history and functions of CAR T-cells while acknowledging their limitations. We can strategize and develop innovative approaches to overcome these barriers by understanding their challenges. This article aims to provide insights into the application of CAR T-cells in treating MM, shedding light on their potential, limitations, and strategies employed to enhance their efficacy.

Multiple Myeloma: A Personal Account of My Journey With the Disease and Response to Teclistamab

Multiple myeloma (MM) remains an incurable hematologic cancer leading to damage to the bone marrow that causes destructive bone lesions in addition to many other effects. I am a patient with MM who has undergone treatment to date since the diagnosis of this disease in December 2019. This paper reviews the treatments and observations made throughout this period. The salient results of such treatments are discussed in chronological order. During this period, my MM relapsed and then I was introduced to teclistamab treatment. The outcome of teclistamab treatment is quite promising, and I anticipate a longer life at a maintenance dose of this drug with a better quality of life. When writing this article, I am still receiving the teclistamab treatment cycles that maintain a constant normal level of my kappa-free light chain (FLC) and kappa/lambda ratio, with no significant side effects.

Practical management of disease-related manifestations and drug toxicities in patients with multiple myeloma

Multiple myeloma (MM) is a very heterogeneous disease with multiple symptoms and clinical manifestations. MM affects mainly elderly patients and is difficult to manage in the presence of comorbidities, polypharmacy, frailty and adverse events of disease-targeted drugs. The rapid changes in MM treatment resulting from constant innovations in this area, together with the introduction of numerous new drugs with distinct mechanisms of action and toxicity profiles, have led to an increased complexity in the therapeutic decision-making and patient management processes. The prolonged exposure to novel agents, sometimes in combination with conventional therapies, makes this management even more challenging. A careful balance between treatment efficacy and its tolerability should be considered for every patient. During treatment, a close monitoring of comorbidities, disease-related manifestations and treatment side effects is recommended, as well as a proactive approach, with reinforcement of information and patient awareness for the early recognition of adverse events, allowing prompt therapeutic adjustments. In this review, we discuss various issues that must be considered in the treatment of MM patients, while giving practical guidance for monitoring, prevention and management of myeloma-related manifestations and treatment-related toxicities.

Dissecting and targeting noncanonical functions of EZH2 in multiple myeloma via an EZH2 degrader

Multiple myeloma (MM) is the second most common hematological malignancy with poor prognosis. Enhancer of zeste homolog 2 (EZH2) is the enzymatic subunit of polycomb repressive complex 2 (PRC2), which catalyzes trimethylation of histone H3 lysine 27 (H3K27me3) for transcriptional repression. EZH2 have been implicated in numerous hematological malignancies, including MM. However, noncanonical functions of EZH2 in MM tumorigenesis are not well understood. Here, we uncovered a noncanonical function of EZH2 in MM malignancy. In addition to the PRC2-mediated and H3K27me3-dependent canonical function, EZH2 interacts with cMyc and co-localizes with gene activation-related markers, promoting MM tumorigenesis in a PRC2- and H3K27me3-independent manner. Both canonical EZH2-PRC2 and noncanonical EZH2-cMyc complexes can be effectively depleted in MM cells by MS177, an EZH2 degrader we reported previously, leading to profound activation of EZH2-PRC2-associated genes and simultaneous suppression of EZH2-cMyc oncogenic nodes. The MS177-induced degradation of both canonical EZH2-PRC2 and noncanonical EZH2-cMyc complexes also reactivated immune response genes in MM cells. Phenotypically, targeting of EZH2's both canonical and noncanonical functions by MS177 effectively suppressed the proliferation of MM cells both in vitro and in vivo. Collectively, this study uncovers a new noncanonical function of EZH2 in MM tumorigenesis and provides a novel therapeutic strategy, pharmacological degradation of EZH2, for treating EZH2-dependent MM.

Assessing Pretransplant and Posttransplant Therapy Response in Multiple Myeloma Patients

Multiple myeloma (MM) is a hematologic cancer defined by an abnormal development of clonal plasma cells in the bone marrow, releasing vast quantities of immunoglobulins and different proteins. In the majority of patients, MM remains incurable despite decades of medical improvement and a number of treatment breakthroughs. Frontline standard-of-care has little long-term success, with the majority of patients eventually relapsing, although the overall progression-free survival (PFS) has improved significantly in the last ten years. Patients who are eligible for a transplant have the highest PFS rate at 5 years, depending on medication response and other various factors that are yet to be discovered. Therefore, the current study aimed to evaluate the response to VCD (bortezomib, cyclophosphamide, dexamethasone) and VTD (bortezomib, thalidomide, dexamethasone) used as pretransplant regimens, as well as to compare responses between thalidomide and lenalidomide used as maintenance therapy posttransplant. This retrospective study was performed on a group of 105 hospitalized patients in the Hematology Department of the Timisoara Municipal Emergency Clinical Hospital between January 2016 and December 2021. Data was collected from the paper records of patients with MM who were under-followed. The treatment regimens used as induction therapy were either VCD or VTD if cyclophosphamide was contraindicated. Of the 105 patients, 27 became eligible for bone marrow transplantation. Furthermore, they received maintenance therapy which was based on either lenalidomide with dexamethasone or thalidomide with dexamethasone. Of the 62 patients treated with VTD, 17.7% were in complete remission before stem cell transplantation. Of the 43 patients treated with VCD, 37.2% were in complete remission. The 5-year mean progression-free survival (PFS) in the entire cohort was better in the group treated with the VTD regimen (31.6 vs. 27.2 months). However, in the 27 patients undergoing maintenance after ASCT, the PFS with thalidomide was 35.5 months (95% CI = 27-42), while the PFS rate in those receiving maintenance treatment with lenalidomide was 46.1 months (95% CI = 20-73). VCD proved to be superior to VTD in inducing complete pretransplant responses. Regarding maintenance therapy, patients from the lenalidomide group had superior responses compared with those under thalidomide.

Clinical Utility of Next-Generation Flow-Based Minimal Residual Disease Assessment in Patients with Multiple Myeloma

Background

Minimal residual disease (MRD) is an important prognostic factor for evaluating a deeper treatment response in patients with multiple myeloma (MM). We evaluated the clinical utility of next-generation flow (NGF)-based MRD assessment in a heterogeneous MM patient population.

Methods

Patients with suspected morphological remission after or during MM treatment were prospectively enrolled. In total, 108 bone marrow samples from 90 patients were analyzed using NGF-based MRD assessment according to the EuroFlow protocol, and progression-free survival (PFS) was evaluated according to the International Myeloma Working Group response status, cytogenetic risk, and MRD status.

Results

The overall MRD-positive rate was 31.5% (34/108 samples), and MRD-positive patients showed a lower PFS than MRD-negative patients (P=0.005). MRD-positive patients showed inferior PFS than MRD-negative in patients with stringent complete remission (sCR)/complete remission (P=0.014) and high-risk cytogenetic abnormalities (P=0.016). MRD was assessed twice in 18 patients with a median interval of 12 months. Sustained MRD negativity was only observed in patients with sustained sCR, and their PFS was superior to that of patients who were not MRD-negative (P=0.035).

Conclusions

Clinical application of NGF-based MRD assessment can provide valuable information for predicting disease progression in patients with MM in remission, including those with high-risk cytogenetic abnormalities.

Opportunities for Participation in Randomized Controlled Trials for Patients with Multiple Myeloma: Trial Access Depends on Restrictive Eligibility Criteria and Patient Expectations

Simple Summary

Over the past decade, randomized controlled trials as an established instrument of evidence-based medicine have contributed fundamentally to the development and approval of new substances. However, it has been frequently shown that less than 5% of adult cancer patients enroll in clinical trials. Barriers to trial participation have been extensively studied, but the rate of trial participation has not changed substantially. In this retrospective analysis, we found that 53% of newly diagnosed multiple myeloma patients met the eligibility criteria, while only 38% of relapsed refractory patients were eligible. Moreover, our data show for the first time that eligible patients tend to become more reluctant to participate over the course of the disease, with 42% of newly diagnosed patients consenting, and only 7% of relapsed/refractory patients consenting. Thus, our results may assist with trial design improvements and address patient expectations and priorities in order to increase enrollment.

Abstract

Randomized controlled trials (RCT) are the driver of therapeutic innovations. However, it has been frequently shown that less than 5% of adult cancer patients enroll in clinical trials, although 70% of patients are considered as being willing to participate. Barriers to trial participation have been extensively studied. Although there is evidence that trial participation correlates with improved survival and reduced mortality, the rate of participation has not changed substantially. We provide retrospective data from a single-center analysis of 411 patients with multiple myeloma (MM) who were treated at the University Hospital Duesseldorf in Germany between January 2014 and December 2016. Each patient was analyzed for the real-world possibility of participating in a clinical study, based on the inclusion and exclusion (I/E) criteria and the recruiting period of open studies. The overall rate of study participation was 19%. A total of 53% of NDMM patients were eligible for first-line studies (GMMG-HD6, LenaMain). Of these, 80% consented to enrolment (42% of all). In contrast, only 38% of the RRMM population was eligible (GMMG-Relapse, Castor, Tourmaline, Admyre). Of these, only 22% (7% of all) consented. This was confirmed by virtual analysis, showing that only 29% of all RRMM patients would have been eligible for six internationally recruiting trials leading to later drug approval. The majority of cases were rendered ineligible by only one I/E criterion. The most common criteria were study-specific (prior therapies or refractory disease to a specific drug), kidney disease, and previous malignancy, followed by internal, neurologic, and infectious disease. In summary, this single-center analysis showed that I/E criteria permit study participation for most NNDM patients, with a dramatic decrease in the RRMM population. This is aggravated by the fact that the willingness for study participation also significantly declines in RRMM. Thus, addressing patient expectations and priorities seems to be the most promising approach to increasing patient enrollment in clinical trials.

Risk Stratification Before and During Treatment in Newly Diagnosed Multiple Myeloma: From Clinical Trials to the Real-World Setting

Multiple Myeloma (MM) is a hematologic malignancy characterized by a wide clinical and biological heterogeneity leading to different patient outcomes. Various prognostic tools to stratify newly diagnosed (ND)MM patients into different risk groups have been proposed. At baseline, the standard-of-care prognostic score is the Revised International Staging System (R-ISS), which stratifies patients according to widely available serum markers (i.e., albumin, β 2-microglobulin, lactate dehydrogenase) and high-risk cytogenetic abnormalities detected by fluorescence in situ hybridization. Though this score clearly identifies a low-risk and a high-risk population, the majority of patients are categorized as at “intermediate risk”. Although new prognostic factors identified through molecular assays (e.g., gene expression profiling, next-generation sequencing) are now available and may improve risk stratification, the majority of them need specialized centers and bioinformatic expertise that may preclude their broad application in the real-world setting. In the last years, new tools to monitor response and measurable residual disease (MRD) with very high sensitivity after the start of treatment have been developed. MRD analyses both inside and outside the bone marrow have a strong prognostic impact, and the achievement of MRD negativity may counterbalance the high-risk behavior identified at baseline. All these techniques have been developed in clinical trials. However, their efficient application in real-world clinical practice and their potential role to guide treatment-decision making are still open issues. This mini review will cover currently known prognostic factors identified before and during first-line treatment, with a particular focus on their potential applications in real-world clinical practice.

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.

Solid Organ Transplantation and Survival among Individuals with a History of Cancer

BACKGROUND

The success of immunotherapy highlights a possible role for immunity in controlling cancer during remission for patients with cancer in the general population. A prior cancer diagnosis is common among solid organ transplant candidates, and immunosuppressive medications administered to transplant recipients may increase recurrence risk.

METHODS

Using linked data from the United States solid organ transplant registry and 13 cancer registries, we compared overall and cancer-specific survival among patients with cancer who did versus did not receive subsequent transplantation. We used Cox regression in cohort and matched analyses, controlling for demographic factors, cancer stage, and time since cancer diagnosis.

RESULTS

The study included 10,524,326 patients with cancer, with 17 cancer types; 5,425 (0.05%) subsequently underwent solid organ transplantation. The median time from cancer diagnosis to transplantation was 5.7 years. Transplantation was associated with reduced overall survival for most cancers, especially cervical, testicular, and thyroid cancers [adjusted hazard ratios (aHR) for overall mortality, 3.43-4.88]. In contrast, transplantation was not associated with decreased cancer-specific survival for any cancer site, and we observed inverse associations for patients with breast cancer (aHRs for cancer-specific mortality, 0.65-0.67), non-Hodgkin lymphoma (0.50-0.51), and myeloma (0.39-0.42).

CONCLUSIONS

Among U.S. patients with cancer, subsequent organ transplantation was associated with reduced overall survival, likely due to end-stage organ disease and transplant-related complications. However, we did not observe adverse associations with cancer-specific survival, partly reflecting careful candidate selection.

IMPACT

These results do not demonstrate a detrimental effect of immunosuppression on cancer-specific survival and support current management strategies for transplant candidates with previous cancer diagnoses.

Minimal residual disease assessment by multiparameter flow cytometry in transplant-eligible myeloma in the EMN02/HOVON 95 MM trial

Minimal residual disease (MRD) by multiparameter flow cytometry (MFC) is the most effective tool to define a deep response in multiple myeloma (MM). We conducted an MRD correlative study of the EMN02/HO95 MM phase III trial in newly diagnosed MM patients achieving a suspected complete response before maintenance and every 6 months during maintenance. Patients received high-dose melphalan (HDM) versus bortezomib-melphalan-prednisone (VMP) intensification, followed by bortezomib-lenalidomide-dexamethasone (VRd) versus no consolidation, and lenalidomide maintenance. Bone marrow (BM) samples were processed in three European laboratories, applying EuroFlow-based MFC protocols (eight colors, two tubes) with 10-4-10-5 sensitivity. At enrollment in the MRD correlative study, 76% (244/321) of patients were MRD-negative. In the intention-to-treat analysis, after a median follow-up of 75 months, 5-year progression-free survival was 66% in MRD-negative versus 31% in MRD-positive patients (HR 0.39; p < 0.001), 5-year overall survival was 86% versus 69%, respectively (HR 0.41; p < 0.001). MRD negativity was associated with reduced risk of progression or death in all subgroups, including ISS-III (HR 0.37) and high-risk fluorescence in situ hybridization (FISH) patients (HR 0.38;). In the 1-year maintenance MRD population, 42% of MRD-positive patients at pre-maintenance became MRD-negative after lenalidomide exposure. In conclusion, MRD by MFC is a strong prognostic factor. Lenalidomide maintenance further improved MRD-negativity rate.

Final results of a phase 1b study of isatuximab short-duration fixed-volume infusion combination therapy for relapsed/refractory multiple myeloma

Part B of this phase 1b study (ClinicalTrials.gov number, NCT02283775) evaluated safety and efficacy of a fixed-volume infusion of isatuximab, an anti-CD38 monoclonal antibody, in combination with pomalidomide and dexamethasone (Pd) in relapsed/refractory multiple myeloma patients. Isatuximab (10 mg/kg weekly for 4 weeks, then every other week) was administered as a fixed-volume infusion of 250 mL (mL/h infusion rate) with standard doses of Pd on 28-day cycles. Patients (N = 47) had a median of three prior treatment lines (range, 1-8). Median duration of exposure was 36.9 weeks and median duration of first, second, and 3+ infusions were 3.7, 1.8, and 1.2 h, respectively. The most common non-hematologic treatment-emergent adverse events were fatigue (63.8%), infusion reactions (IRs), cough, and upper respiratory tract infection (40.4% each). IRs were all grade 2 and occurred only during the first infusion. The overall response rate was 53.2% in all patients (55.5% in response-evaluable population, 60.0% in daratumumab-naïve patients). Efficacy and safety findings were consistent with data from the isatuximab plus Pd infusion schedule in Part A of this study and also from the phase 3 ICARIA-MM study, and these new data confirm the safety, efficacy, and feasibility of fixed-volume infusion of isatuximab.

MRD Assessment in Multiple Myeloma: Progress and Challenges

PURPOSE OF REVIEW

Over the last decade, the development of effective treatment approaches for multiple myeloma (MM) has been associated with higher response rates and longer survival. In patients who achieve complete response, several high sensitivity techniques have been studied to assess minimal residual disease (MRD) and detect residual neoplastic cells within the bone marrow (by flow cytometry or molecular biology techniques) or outside the bone marrow (by imaging or circulating disease markers in the peripheral blood). This is of utmost importance, since residual disease can drive clinical relapse. This review focuses on the progress made in the assessment of MRD in MM.

RECENT FINDINGS

The achievement of MRD negativity after therapy is considered prognostically important for MM patients, and data from clinical trials and meta-analyses have confirmed that it is strongly associated with better survival. Along with well-known techniques, such as next-generation sequencing (NGS), next-generation flow (NGF), and positron emission tomography/computed tomography (PET/CT), other methods such as mass spectrometry (MS) and circulating tumor cells are under study. Intensive treatment regimens at diagnosis can lead up to 70% of MRD negativity in MM patients, although the current proportion of curable patients is still unknown. Today, clinicians who treat MM deal with MRD assessment in routine clinical practice. Its appropriate use in therapeutic decision making may be the most fascinating and challenging issue to be addressed over the next few years.

Current Methods of Post-Translational Modification Analysis and Their Applications in Blood Cancers

Post-translational modifications (PTMs) add a layer of complexity to the proteome through the addition of biochemical moieties to specific residues of proteins, altering their structure, function and/or localization. Mass spectrometry (MS)-based techniques are at the forefront of PTM analysis due to their ability to detect large numbers of modified proteins with a high level of sensitivity and specificity. The low stoichiometry of modified peptides means fractionation and enrichment techniques are often performed prior to MS to improve detection yields. Immuno-based techniques remain popular, with improvements in the quality of commercially available modification-specific antibodies facilitating the detection of modified proteins with high affinity. PTM-focused studies on blood cancers have provided information on altered cellular processes, including cell signaling, apoptosis and transcriptional regulation, that contribute to the malignant phenotype. Furthermore, the mechanism of action of many blood cancer therapies, such as kinase inhibitors, involves inhibiting or modulating protein modifications. Continued optimization of protocols and techniques for PTM analysis in blood cancer will undoubtedly lead to novel insights into mechanisms of malignant transformation, proliferation, and survival, in addition to the identification of novel biomarkers and therapeutic targets. This review discusses techniques used for PTM analysis and their applications in blood cancer research.

Belantamab mafodotin in combination with novel agents in relapsed/refractory multiple myeloma: DREAMM-5 study design

Belantamab mafodotin (belamaf) is a BCMA-targeted antibody-drug conjugate recently approved as monotherapy for adults with relapsed/refractory multiple myeloma who have received ≥4 prior therapies. Belamaf binds to BCMA and eliminates myeloma cells by multimodal mechanisms of action. The cytotoxic and potential immunomodulatory properties of belamaf have led to novel combination studies with other anticancer therapies. Here, we describe the rationale and design of DREAMM-5, an ongoing Phase I/II platform study evaluating the safety and efficacy of belamaf combined with novel agents, including GSK3174998 (OX40 agonist), feladilimab (an ICOS; GSK3359609), nirogacestat (a gamma-secretase inhibitor; PF-03084014) and dostarlimab (a PD-1 blocker) versus belamaf monotherapy for patients with relapsed/refractory multiple myeloma. Clinical trial registration: NCT04126200 (ClinicalTrials.gov).

Management of patients with multiple myeloma beyond the clinical-trial setting: understanding the balance between efficacy, safety and tolerability, and quality of life

Treatment options in multiple myeloma (MM) are increasing with the introduction of complex multi-novel-agent-based regimens investigated in randomized clinical trials. However, application in the real-world setting, including feasibility of and adherence to these regimens, may be limited due to varying patient-, treatment-, and disease-related factors. Furthermore, approximately 40% of real-world MM patients do not meet the criteria for phase 3 studies on which approvals are based, resulting in a lack of representative phase 3 data for these patients. Therefore, treatment decisions must be tailored based on additional considerations beyond clinical trial efficacy and safety, such as treatment feasibility (including frequency of clinic/hospital attendance), tolerability, effects on quality of life (QoL), and impact of comorbidities. There are multiple factors of importance to real-world MM patients, including disease symptoms, treatment burden and toxicities, ability to participate in daily activities, financial burden, access to treatment and treatment centers, and convenience of treatment. All of these factors are drivers of QoL and treatment satisfaction/compliance. Importantly, given the heterogeneity of MM, individual patients may have different perspectives regarding the most relevant considerations and goals of their treatment. Patient perspectives/goals may also change as they move through their treatment course. Thus, the 'efficacy' of treatment means different things to different patients, and treatment decision-making in the context of personalized medicine must be guided by an individual's composite definition of what constitutes the best treatment choice. This review summarizes the various factors of importance and practical issues that must be considered when determining real-world treatment choices. It assesses the current instruments, methodologies, and recent initiatives for analyzing the MM patient experience. Finally, it suggests options for enhancing data collection on patients and treatments to provide a more holistic definition of the effectiveness of a regimen in the real-world setting.

Metabolic Reprogramming Induces Immune Cell Dysfunction in the Tumor Microenvironment of Multiple Myeloma

Tumor cells rewire metabolism to meet their increased nutritional demands, allowing the maintenance of tumor survival, proliferation, and expansion. Enhancement of glycolysis and glutaminolysis is identified in most, if not all cancers, including multiple myeloma (MM), which interacts with a hypoxic, acidic, and nutritionally deficient tumor microenvironment (TME). In this review, we discuss the metabolic changes including generation, depletion or accumulation of metabolites and signaling pathways, as well as their relationship with the TME in MM cells. Moreover, we describe the crosstalk among metabolism, TME, and changing function of immune cells during cancer progression. The overlapping metabolic phenotype between MM and immune cells is discussed. In this sense, targeting metabolism of MM cells is a promising therapeutic approach. We propose that it is important to define the metabolic signatures that may regulate the function of immune cells in TME in order to improve the response to immunotherapy.

Recent Advances in the Treatment of Patients with Multiple Myeloma

In the past 20 years, few diseases have seen as great progress in their treatment as multiple myeloma. With the approval of many new drugs and the limited availability of clinical trials comparing head-to-head the different possible combinations, the choice of the best treatments at each stage of the disease becomes complex as well as crucial since multiple myeloma remains incurable. This article presents a general description of the novelties of the whole treatment of multiple myeloma, from induction in the newly diagnosed patient through the role of hematopoietic stem cell transplantation and maintenance treatment until early and late relapses, including a section on recently approved drugs as well as novel drugs and immunotherapy in advanced stages of research, and that will surely play a relevant role in the treatment of this devastating disease in the coming years.

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.

Multiple myeloma: the (r)evolution of current therapy and a glance into future

Over the past 20 years, the regulatory approval of several novel agents to treat multiple myeloma (MM) has prolonged median patient survival from 3 to 8-10 years. Increased understanding of MM biology has translated to advances in diagnosis, prognosis, and response assessment, as well as informed the development of targeted and immune agents. Here we provide an overview of the recent progress in MM, and highlight research areas of greatest promise to further improve patient outcome in the future.

New drugs in early development for treating multiple myeloma: all that glitters is not gold

INTRODUCTION

The last twenty years have introduced new therapeutic agents for multiple myeloma (MM); these include proteasome inhibitors (PIs), immunomodulatory drugs (IMDs) and monoclonal antibodies (mAbs). However, MM remains incurable, hence there is an unmet need for new agents for the treatment of advanced refractory disease. New agents could also be used in early lines to achieve improved, more sustained remission.

AREAS COVERED

We review the most promising agents investigated in early-phase trials for the treatment of MM and provide an emphasis on new agents directed against well-known targets (new PIs, IMDs and anti-CD38 mAbs). Drugs that work through distinct and numerous mechanisms of action (e.g. pro-apoptotic agents and tyrosine kinase inhibitors) and innovative immunotherapeutic approaches are also described. The paper culminates with our perspective on therapeutic approaches on the horizon for this disease.

EXPERT OPINION

IMD iberdomide and the export protein inhibitor selinexor demonstrated efficacy in heavily pretreated patients who had no other therapeutic options. We expect that immunotherapy with anti-BCMA BTEs and ADCs will revolutionize the approach to treating the early stages of the disease. Data on venetoclax in t(11;14)-positive patients may pave the way for personalized therapy. Not all new agents under early clinical evaluation will be investigated in regulatory phase III trials; one of the most important challenges is to identify those that could make a difference.

Autologous Transplantation Using Donor Leukocytes Loaded Ex Vivo with Oncolytic Myxoma Virus Can Eliminate Residual Multiple Myeloma

Multiple myeloma (MM) is a hematological malignancy of monoclonal plasma cells that remains incurable. Standard treatments for MM include myeloablative regimens and autologous cell transplantation for eligible patients. A major challenge of these treatments is the relapse of the disease due to residual MM in niches that become refractory to treatments. Therefore, novel therapies are needed in order to eliminate minimal residual disease (MRD). Recently, our laboratory reported that virotherapy with oncolytic myxoma virus (MYXV) improved MM-free survival in an allogeneic transplant mouse model. In this study, we demonstrate the capacity of donor autologous murine leukocytes, pre-armed with MYXV, to eliminate MRD in a BALB/c MM model. We report that MYXV-armed bone marrow (BM) carrier leukocytes are therapeutically superior to MYXV-armed peripheral blood mononuclear cells (PBMCs) or free virus. Importantly, when cured survivor mice were re-challenged with fresh myeloma cells, they developed immunity to the same MM that had comprised MRD. In vivo imaging demonstrated that autologous carrier cells armed with MYXV were very efficient at delivery of MYXV into the recipient tumor microenvironment. Finally, we demonstrate that treatment with MYXV activates the secretion of pro-immune molecules from the tumor bed. These results highlight the utility of exploiting autologous leukocytes to enhance tumor delivery of MYXV to treat MRD in vivo.

Dual Targeting to Overcome Current Challenges in Multiple Myeloma CAR T-Cell Treatment

In the era of highly promising novel targeted-immunotherapy strategies for multiple myeloma (MM), the first series of clinical trials with CAR T-cells targeting the plasma cell-specific B-cell maturation antigen (BCMA) have shown excellent response rates. In the long-term, however, MM appears to escape the therapy likely due to initial low and heterogeneous expression or downregulation of BCMA expression. Several other molecules targeted by CAR T-cells in MM are expressed at high levels on MM cells, but many of these attractive targets are also expressed on various, sometimes vital non-malignant cells, posing major risks for on-target, off-tumor side effects. CAR T-cell therapy for MM therefore faces two urgent challenges: (i) improving the efficacy of BCMA CAR T-cells and (ii) establishing a MM-selectivity even when CAR T-cells are directed against not entirely MM-specific target antigens. In this review, we will outline the current attempts to tackle these challenges, with a specific focus on how dual CAR targeting might be applied to tackle both issues.

Minimal Residual Disease in Multiple Myeloma: Current Landscape and Future Applications With Immunotherapeutic Approaches

The basic principle that deeper therapeutic responses lead to better clinical outcomes in cancer has emerged technologies capable of detecting rare residual tumor cells. The need for ultra-sensitive approaches for minimal residual disease (MRD) detection is particularly evident in Multiple Myeloma (MM), where patients will ultimately relapse despite the achievement of complete remission, which is commonplace due to remarkable therapeutic advances. Consequently, current response criteria on MM have been amended based on MRD status and MRD negativity is now considered the most dominant prognostic factor and the most valuable indicator for a subsequent relapse. However, there are particular limitations and several aspects for MRD assessment that remain open. This review summarizes current data on MRD in the clinical management of MM, highlights open issues and discusses the challenges and the endless opportunities arising for both patients and clinicians. Furthermore, it focuses on the current status of MRD in clinical trials, its dynamics in addressing debatable aspects in the clinical handling and its potential role as the prevailing factor for future MRD-driven tailored therapies.