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

Remineralization Rate of Lytic Lesions of the Spine in Multiple Myeloma Patients Undergoing Radiation Therapy

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

In general, Multiple Myeloma (MM) patients are treated with systemic therapy including chemotherapy. Radiation therapy can have an important supportive role in the palliative management of MM-related osteolytic lesions. Our study aims to investigate the degree of radiation-induced remineralization in MM patients to gain a better understanding of its potential impact on bone mineral density and, consequently, fracture prevention. Our primary outcome measure was percent change in bone mineral density measured in Hounsfield Units (Δ% HU) between pre- and post-radiation measurements, compared to non-targeted vertebrae.

METHODS

We included 119 patients with MM who underwent radiotherapy of the spine between January 2010 and June 2021 and who had a CT scan of the spine at baseline and between 3-24 months after radiation. A linear mixed effect model tested any differences in remineralization rate per month (βdifference) between targeted and non-targeted vertebrae.

RESULTS

Analyses of CT scans yielded 565 unique vertebrae (366 targeted and 199 non-targeted vertebrae). In both targeted and non-targeted vertebrae, there was an increase in bone density per month (βoverall = .04; P = .002) with the largest effect being between 9-18 months post-radiation. Radiation did not cause a greater increase in bone density per month compared to non-targeted vertebrae (βdifference = .67; P = .118).

CONCLUSION

Our results demonstrate that following radiation, bone density increased over time for both targeted and non-targeted vertebrae. However, no conclusive evidence was found that targeted vertebrae have a higher remineralization rate than non-targeted vertebrae in patients with MM.

Expanding the horizon of transient CAR T therapeutics using virus-free technology

The extraordinary success that chimeric antigen receptor (CAR) T cell therapies have shown over the years on fighting hematological malignancies is evidenced by the six FDA-approved products present on the market. CAR T treatments have forever changed the way we understand cellular immunotherapies, as current research in the topic is expanding even outside the field of cancer with very promising results. Until now, virus-based strategies have been used for CAR T cell manufacturing. However, this methodology presents relevant limitations that need to be addressed prior to wide spreading this technology to other pathologies and in order to optimize current cancer treatments. Several approaches are being explored to overcome these challenges such as virus-free alternatives that additionally offer the possibility of developing transient CAR expression or in vivo T cell modification. In this review, we aim to spotlight a pivotal juncture in the history of medicine where a significant change in perspective is occurring. We review the current progress made on viral-based CAR T therapies as well as their limitations and we discuss the future outlook of virus-free CAR T strategies to overcome current challenges and achieve affordable immunotherapies for a wide variety of pathologies, including cancer.

Chimeric antigen receptor T-cell therapy in hematologic malignancies: Successes, challenges, and opportunities

The success of chimeric antigen receptor T-cell (CAR-T) therapy in hematologic malignancies has realized a longstanding effort toward harnessing the immune system to fight cancer in a truly personalized fashion. Second generation chimeric antigen receptors (CAR) incorporating co-stimulatory molecules like 4-1BB or CD28 were able to overcome some of the hindrances with initial CAR constructs resulting in efficacious products. Many second-generation CAR-T products have been approved in the treatment of relapsed/refractory hematologic malignancies including multiple myeloma (MM), non-Hodgkin lymphoma (NHL), and acute lymphoblastic leukemia. However, challenges remain in optimizing the manufacturing, timely access, limiting the toxicity from CAR-T infusions and improving sustainability of responses derived with CAR-T therapy. Here, we summarize the clinical trial data leading to approval CAR-T therapies in MM and NHL, discuss the limitations with current CAR-T therapy strategies and review emerging strategies for overcoming these limitations.

Targeted immunotherapy: harnessing the immune system to battle multiple myeloma

Multiple myeloma (MM) remains an incurable hematological malignancy disease characterized by the progressive dysfunction of the patient's immune system. In this context, immunotherapy for MM has emerged as a prominent area of research in recent years. Various targeted immunotherapy strategies, such as monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, chimeric antigen receptor T cells/natural killer (NK) cells, and checkpoint inhibitors have been developed for MM. This review aims to discuss promising experimental and clinical evidence as well as the mechanisms of action underlying these immunotherapies. Specifically, we will explore the design of exosome-based bispecific monoclonal antibodies that offer cell-free immunotherapy options. The treatment landscape for myeloma continues to evolve with the development of numerous emerging immunotherapies. Given their significant advantages in modulating the MM immune environment through immune-targeted therapy, these approaches provide novel perspectives in selecting cutting-edge treatments for MM.

CAR T-Cell Therapy for Multiple Myeloma: A Clinical Practice-Oriented Review

The emergence of chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of hematologic malignancies, including multiple myeloma (MM). Two BCMA-directed CAR T-cell products - idecabtagene vicleucel (ide-cel) and ciltacabtagene autoleucel (cilta-cel) - have received US Food and Drug Administration (FDA) approval for patients with relapsed/refractory MM who underwent four or more prior lines of therapy (including an immunomodulatory agent, a proteasome inhibitor, and an anti-CD38 monoclonal antibody). Despite producing unprecedented response rates in an otherwise difficult to treat patient population, CAR T-cell therapies are commonly associated with immune-related adverse events (e.g., cytokine release syndrome and neurotoxicity), cytopenias, and infections. Moreover, many patients continue to exhibit relapse post-treatment, with resistance mechanisms yet to be fully understood. Ongoing basic, translational, and clinical research efforts are poised to generate deeper insights into the optimal utilization of these therapies, improve their efficacy, minimize associated toxicity, and identify new target antigens in patients with MM.

Enhanced antitumor efficacy, proliferative capacity, and alleviation of T cell exhaustion by fifth-generation chimeric antigen receptor T cells targeting B cell maturation antigen in multiple myeloma

Chimeric antigen receptor (CAR) T cell therapy targeting B cell maturation antigen (BCMA) has been approved for treating multiple myeloma (MM). Some clinical studies reported suboptimal outcomes, including reduced cytotoxicity of CAR-T cells and tumor evasion through increased expression of programmed death-ligand 1 (PD-L1). To enhance CAR-T cell efficiency and overcome PD-L1-mediated T cell suppression, we developed anti-BCMA-CAR5-T cells equipped with three costimulatory domains and the ability to secrete anti-PD-L1 single-chain variable fragment (scFv) blockade molecules. Anti-BCMA-CAR4-T cells contained a fully human anti-BCMA scFv and three intracellular domains (CD28, 4-1BB, and CD27) joined with CD3ζ. Anti-BCMA-CAR5-T cells were generated by fusing anti-BCMA-CAR4 with anti-PD-L1 scFv. Both anti-BCMA-CAR4-T and anti-BCMA-CAR5-T cells demonstrated comparable antitumor activity against parental MM cells. However, at an effector-to-target ratio of 1:2, only anti-BCMA-CAR5-T cells maintained cytolytic activity against PD-L1 high MM cells, unlike anti-BCMA-CAR4 T cells. Anti-BCMA-CAR5-T cells were specifically activated by BCMA-expressing target cells, resulting in increased CAR-T cell proliferation, release of cytolytic mediators, and pro-inflammatory cytokines. Anti-BCMA-CAR5-T cells demonstrated specific cytotoxicity against BCMA-expressing target cells, leading to decreased target cell numbers, increased CAR-T cell numbers, and preserved CAR expression during antigenic re-stimulation. Interestingly, only anti-BCMA-CAR5-T cells showed reduced PD-1 receptor levels, which correlated with decreased PD-L1 expression on target cells. We successfully generated anti-BCMA-CAR5-T cells capable of secreting anti-PD-L1 scFv. These cells exhibited superior antitumor efficiency, proliferative capacity, and alleviated T-cell exhaustion against MM cells. Further investigation into the antitumor efficacy of anti-BCMA-CAR5-T cells is warranted in ex vivo and clinical research settings.

CAR-T Cell Therapy in the Treatment of Pediatric Non-Hodgkin Lymphoma

Non-Hodgkin lymphomas (NHL) are a group of cancers that originate in the lymphatic system, especially from progenitor or mature B-cells, T-cells, or natural killer (NK) cells. NHL is the most common hematological malignancy worldwide and also the fourth most frequent type of cancer among pediatric patients. This cancer can occur in children of any age, but it is quite rare under the age of 5 years. In recent decades, available medicines and therapies have significantly improved the prognosis of patients with this cancer. However, some cases of NHL are treatment resistant. For this reason, immunotherapy, as a more targeted and personalized treatment strategy, is becoming increasingly important in the treatment of NHL in pediatric patients. The objective of the following review is to gather the latest available research results, conducted among pediatric and/or adult patients with NHL, regarding one immunotherapy method, i.e., chimeric antigen receptor (CAR) T cell therapy. We focus on assessing the effectiveness of CAR-T cell therapy, which mainly targets B cell markers, CD19, CD20, and CD22, their connections with one another, sequential treatment, or connections with co-stimulatory molecules. In addition, we also evaluate the safety, aftermath (especially neurotoxicities) and limitations of CAR-T cell therapy.

Impacting T-cell fitness in multiple myeloma: potential roles for selinexor and XPO1 inhibitors

Competent T-cells with sufficient levels of fitness combat cancer formation and progression. In multiple myeloma (MM), T-cell exhaustion is caused by several factors including tumor burden, constant immune activation due to chronic disease, age, nutritional status, and certain MM treatments such as alkylating agents and proteasome inhibitors. Many currently used therapies, including bispecific T-cell engagers, anti-CD38 antibodies, proteasome inhibitors, and CART-cells, directly or indirectly depend on the anti-cancer activity of T-cells. Reduced T-cell fitness not only diminishes immune defenses, increasing patient susceptibility to opportunistic infections, but can impact effectiveness MM therapy effectiveness, bringing into focus sequencing strategies that could modulate T-cell fitness and potentially optimize overall benefit and clinical outcomes. Certain targeted agents used to treat MM, such as selective inhibitors of nuclear export (SINE) compounds, have the potential to mitigate T-cell exhaustion. Herein referred to as XPO1 inhibitors, SINE compounds inhibit the nuclear export protein exportin 1 (XPO1), which leads to nuclear retention and activation of tumor suppressor proteins and downregulation of oncoprotein expression. The XPO1 inhibitors selinexor and eltanexor reduced T-cell exhaustion in cell lines and animal models, suggesting their potential role in revitalizating these key effector cells. Additional clinical studies are needed to understand how T-cell fitness is impacted by diseases and therapeutic factors in MM, to potentially facilitate the optimal use of available treatments that depend on, and impact, T-cell function. This review summarizes the importance of T-cell fitness and the potential to optimize treatment using T-cell engaging therapies with a focus on XPO1 inhibitors.

Targeted single-cell proteomic analysis identifies new liquid biopsy biomarkers associated with multiple myeloma

Multiple myeloma (MM) is accompanied by alterations to the normal plasma cell (PC) proteome, leading to changes to the tumor microenvironment and disease progression. There is a great need for understanding the consequences that lead to MM progression and for the discovery of new biomarkers that can aid clinical diagnostics and serve as targets for therapeutics. This study demonstrates the applicability of utilizing the single-cell high-definition liquid biopsy assay (HDSCA) and imaging mass cytometry to characterize the proteomic profile of myeloma. In our study, we analyzed ~87,000 cells from seven patient samples (bone marrow and peripheral blood) across the myeloma disease spectrum and utilized our multiplexed panel to characterize the expression of clinical markers for PC classification, additional potential therapeutic targets, and the tumor microenvironment cells. Our analysis showed BCMA, ICAM3 (CD50), CD221, and CS1 (SLAMF7) as the most abundantly expressed markers on PCs across all myeloma stages, with BCMA, ICAM3, and CD221 having significantly higher expression levels on disease versus precursor PCs. Additionally, we identify significantly elevated levels of expression for CD74, MUM1, CD229, CD44, IGLL5, Cyclin D1, UBA52, and CD317 on PCs from overt disease conditions compared to those from precursor states.

SLAMF7 as a Promising Immunotherapeutic Target in Multiple Myeloma Treatments

Multiple myeloma (MM) is a common hematological malignancy that has fostered several new therapeutic approaches to combat newly diagnosed or relapsed MM. While the field has advanced over the past 2 decades, the majority of patients will develop resistance to these treatments, causing the need for new therapeutic targets. SLAMF7 is an attractive therapeutic target in multiple myeloma, and a monoclonal antibody that targets SLAMF7 has shown consistent beneficial outcomes in clinical trials to date. In this review, we will focus on the structure and regulation of SLAMF7 and its mechanism of action. The most recent clinical trials will be reviewed to further understand the clinical implications and improve the prognosis of MM. Furthermore, the efficacy of anti-SLAMF7 monoclonal antibodies combined with standard therapies and possible resistance mechanisms will be discussed. This review aimed to provide a detailed summary of the role of SLAMF7 in the pathogenesis of patients with MM and the rationale for further investigation into SLAMF7-mediated molecular pathways associated with MM development.

A phase I first-in-man study to investigate the pharmacokinetics and safety of liposomal dexamethasone in patients with progressive multiple myeloma

Despite the introduction of multiple new drugs and combination therapies, conventional dexamethasone remains a cornerstone in the treatment of multiple myeloma (MM). Its application is, however, limited by frequent adverse effects of which the increased infection rate may have the strongest clinical impact. The efficacy-safety ratio of dexamethasone in MM may be increased by encapsulation in long-circulating PEG-liposomes, thereby both enhancing drug delivery to MM lesions and reducing systemic corticosteroid exposure. We evaluated the preliminary safety and feasibility of a single intravenous (i.v.) infusion of pegylated liposomal dexamethasone phosphate (Dex-PL) in heavily pretreated relapsing or progressive symptomatic MM patients within a phase I open-label non-comparative interventional trial at two dose levels. In the 7 patients that were enrolled (prior to having to close the study prematurely due to slow recruitment), Dex-PL was found to be well tolerated and, as compared to conventional dexamethasone, no new or unexpected adverse events were detected. Pharmacokinetic analysis showed high and persisting concentrations of dexamethasone in the circulation for over a week after i.v. administration, likely caused by the long-circulation half-life of the liposomes that retain dexamethasone as the inactive phosphate prodrug form, something which could significantly limit systemic exposure to the active parent drug. Thus, despite the limitations of this small first-in-man trial, Dex-PL seems safe and well tolerated without severe side effects. Follow-up studies are needed to confirm this in a larger patient cohort and to evaluate if i.v. Dex-PL can provide a safer and more efficacious dexamethasone treatment option for MM.

Relapsed/Refractory Multiple Myeloma: A Review of Available Therapies and Clinical Scenarios Encountered in Myeloma Relapse

Multiple myeloma remains an incurable disease with the usual disease course requiring induction therapy, autologous stem cell transplantation for eligible patients, and long-term maintenance. Risk stratification tools and cytogenetic alterations help inform individualized therapeutic choices for patients in hopes of achieving long-term remissions with preserved quality of life. Unfortunately, relapses occur at different stages of the course of the disease owing to the biological heterogeneity of the disease. Addressing relapse can be complex and challenging as there are both therapy- and patient-related factors to consider. In this broad scoping review of available therapies in relapsed/refractory multiple myeloma (RRMM), we cover the pharmacologic mechanisms underlying active therapies such as immunomodulatory agents (IMiDs), proteasome inhibitors (PIs), monoclonal antibodies (mAbs), traditional chemotherapy, and Venetoclax. We then review the clinical data supporting the use of these therapies, organized based on drug resistance/refractoriness, and the role of autologous stem cell transplant (ASCT). Approaches to special situations during relapse such as renal impairment and extramedullary disease are also covered. Lastly, we look towards the future by briefly reviewing the clinical data supporting the use of chimeric antigen receptor (CAR-T) therapy, bispecific T cell engagers (BITE), and Cereblon E3 Ligase Modulators (CELMoDs).

CARs and Drugs: Pharmacological Ways of Boosting CAR-T-Cell Therapy

The development of chimeric antigen receptor T cells (CAR-T cells) has marked a new era in cancer immunotherapy. Based on a multitude of durable complete remissions in patients with hematological malignancies, FDA and EMA approval was issued to several CAR products targeting lymphoid leukemias and lymphomas. Nevertheless, about 50% of patients treated with these approved CAR products experience relapse or refractory disease necessitating salvage strategies. Moreover, in the vast majority of patients suffering from solid tumors, CAR-T-cell infusions could not induce durable complete remissions so far. Crucial obstacles to CAR-T-cell therapy resulting in a priori CAR-T-cell refractory disease or relapse after initially successful CAR-T-cell therapy encompass antigen shutdown and CAR-T-cell dysfunctionality. Antigen shutdown predominately rationalizes disease relapse in hematological malignancies, and CAR-T-cell dysfunctionality is characterized by insufficient CAR-T-cell proliferation and cytotoxicity frequently observed in patients with solid tumors. Thus, strategies to surmount those obstacles are being developed with high urgency. In this review, we want to highlight different approaches to combine CAR-T cells with drugs, such as small molecules and antibodies, to pharmacologically boost CAR-T-cell therapy. In particular, we discuss how certain drugs may help to counteract antigen shutdown and CAR-T-cell dysfunctionality in both hematological malignancies and solid tumors.

NK cell therapy in relapsed refractory multiple myeloma

Recent advances in adoptive cell therapy have considerably changed the paradigm of cancer immunotherapy. Although current immunotherapies could cure many patients with multiple myeloma (MM), relapsed/refractory MM (RR/MM) is still challenging in some cases. Natural killer (NK) cells are innate immune cells that exert effective cytotoxic activity against malignant cells like myeloma cells. In addition to their antitumor properties, NK cells do not induce graft versus host disease following transplantation. Therefore, they provide a promising approach to treating RR/MM patients. Currently, attempts have been made to produce large-scale and good manufacturing practices (GMP) of NK cells. Ex vivo expanded/activated NK cells derived from the own patient or allogenic donors are potential options for NK cell therapy in MM. Besides, novel cell-based products such as NK cell lines and chimeric antigen receptor (CAR)-NK cells may provide an off-the-shelf source for NK cell therapy. Here, we summarized NK cell activity in the MM microenvironment and focused on different NK cell therapy methods for MM patients.

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.

Treating Multiple Myeloma in the Context of the Bone Marrow Microenvironment

The treatment landscape of multiple myeloma (MM) has evolved considerably with the FDA-approval of at least 15 drugs over the past two decades. Together with the use of autologous stem cell transplantation, these novel therapies have resulted in significant survival benefit for patients with MM. In particular, our improved understanding of the BM and immune microenvironment has led to the development of highly effective immunotherapies that have demonstrated unprecedented response rates even in the multiple refractory disease setting. However, MM remains challenging to treat especially in a high-risk setting. A key mediator of therapeutic resistance in MM is the bone marrow (BM) microenvironment; a deeper understanding is necessary to facilitate the development of therapies that target MM in the context of the BM milieu to elicit deeper and more durable responses with the ultimate goal of long-term control or a cure of MM. In this review, we discuss our current understanding of the role the BM microenvironment plays in MM pathogenesis, with a focus on its immunosuppressive nature. We also review FDA-approved immunotherapies currently in clinical use and highlight promising immunotherapeutic approaches on the horizon.

CAR T-cells for colorectal cancer immunotherapy: Ready to go?

Chimeric antigen receptor (CAR) T-cells represent a new genetically engineered cell-based immunotherapy tool against cancer. The use of CAR T-cells has revolutionized the therapeutic approach for hematological malignancies. Unfortunately, there is a long way to go before this treatment can be developed for solid tumors, including colorectal cancer. CAR T-cell therapy for colorectal cancer is still in its early stages, and clinical data are scarce. Major limitations of this therapy include high toxicity, relapses, and an impermeable tumor microenvironment for CAR T-cell therapy in colorectal cancer. In this review, we summarize current knowledge, highlight challenges, and discuss perspectives regarding CAR T-cell therapy in colorectal cancer.

Spatially resolved phosphoproteomics reveals fibroblast growth factor receptor recycling-driven regulation of autophagy and survival

Receptor Tyrosine Kinase (RTK) endocytosis-dependent signalling drives cell proliferation and motility during development and adult homeostasis, but is dysregulated in diseases, including cancer. The recruitment of RTK signalling partners during endocytosis, specifically during recycling to the plasma membrane, is still unknown. Focusing on Fibroblast Growth Factor Receptor 2b (FGFR2b) recycling, we reveal FGFR signalling partners proximal to recycling endosomes by developing a Spatially Resolved Phosphoproteomics (SRP) approach based on APEX2-driven biotinylation followed by phosphorylated peptides enrichment. Combining this with traditional phosphoproteomics, bioinformatics, and targeted assays, we uncover that FGFR2b stimulated by its recycling ligand FGF10 activates mTOR-dependent signalling and ULK1 at the recycling endosomes, leading to autophagy suppression and cell survival. This adds to the growing importance of RTK recycling in orchestrating cell fate and suggests a therapeutically targetable vulnerability in ligand-responsive cancer cells. Integrating SRP with other systems biology approaches provides a powerful tool to spatially resolve cellular signalling.

Immunotherapy for the treatment of multiple myeloma

Despite advances in treatment for multiple myeloma, the majority of patients ultimately develop relapsed disease marked by immune evasion and resistance to standard therapy. Immunotherapy has emerged as a powerful tool for tumor-directed cytotoxicity with the unique potential to induce immune memory to reduce the risk of relapse. Understanding the specific mechanisms of immune dysregulation and dysfunction in advanced myeloma is critical to the development of further therapies that produce a durable response. Adoptive cellular therapy, most strikingly CAR T cell therapy, has demonstrated dramatic responses in the setting of refractory disease. Understanding the factors that contribute to immune evasion and the mechanisms of response and resistance to therapy will be critical to developing the next generation of adoptive cellular therapies, informing novel combination therapy, and determining the optimal time to incorporate immune therapy in the treatment of myeloma.

Antifatigue effect of naringin on improving antioxidant capacity and mitochondrial function and preventing muscle damage

The aim of this study was to explore effects of naringin (Nar) on antifatigue ability; the weight-loaded and non-loading swimming tests were performed. Compared with the control group, dietary supplementation of Nar significantly prolonged the weight-loaded swimming time to exhaustion of mice (P < 0.01). Nar significantly reduced the serum lactic acid (LD) level (P < 0.05) and lactate dehydrogenase (LDH) activity (P < 0.001), while increased the serum non-esterified free fatty acids (NEFA) level (P < 0.001). In addition, Nar significantly increased the liver glycogen and muscle glycogen contents (P < 0.05) and the phosphoenolpyruvate carboxykinase (PEPCK) (P < 0.01) and glucokinase (GCK) mRNA levels (P < 0.001) in liver and gastrocnemius (GAS) muscle. Furthermore, Nar significantly improved the antioxidant capacity, mitochondrial function, and muscle mitochondrial fatty acid β-oxidation (P < 0.05), and decreased inflammation and muscle damage-related gene expression (P < 0.05). These findings suggested that Nar can improve antifatigue effect by enhancing antioxidant capacity and mitochondrial function and preventing muscle damage.

T cells isolated from G-CSF-treated multiple myeloma patients are suitable for the generation of BCMA-directed CAR-T cells

Autologous cell immunotherapy using B cell maturation antigen (BCMA)-targeted chimeric antigen receptor (CAR)-T cells is an effective novel treatment for multiple myeloma (MM). This therapy has only been used for relapsed and refractory patients, at which stage the endogenous T cells used to produce the CAR-T cells are affected by the immunosuppressive nature of advanced MM and/or side effects of previous therapies. An alternative pool of "fitter" T cells is found in leukocytoapheresis products that are routinely collected to obtain hematopoietic progenitor cells for autologous stem cell transplantation (ASCT) early in the treatment of MM. However, to mobilize the progenitor cells, patients are dosed with granulocyte colony-stimulating factor (G-CSF), which is reported to adversely affect T cell proliferation, function, and differentiation. Here, we aimed to first establish whether G-CSF treatment negatively influences T cell phenotype and to ascertain whether previous exposure of T cells to G-CSF is deleterious for anti-BCMA CAR-T cells. We observed that G-CSF had a minimal impact on T cell phenotype when added in vitro or administered to patients. Moreover, we found that CAR-T cell fitness and anti-tumor activity were unaffected when generated from G-CSF-exposed T cells. Overall, we showed that ASCT apheresis products are a suitable source of T cells for anti-BCMA CAR-T cell manufacture.

Phase 1 study of C-CAR088, a novel humanized anti-BCMA CAR T-cell therapy in relapsed/refractory multiple myeloma

Background

Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor T-cell (CAR T) therapy showed remarkable efficacy in patients with relapsed or refractory multiple myeloma (RRMM). This phase 1 dose-escalation and expansion study developed C-CAR088, a novel second-generation humanized anti-BCMA CAR T-cell therapy, and assessed the safety and efficacy of three dosages of C-CAR088 in patients with RRMM.

Methods

Patients received lymphodepletion with three doses of cyclophosphamide (300 mg/m²) and three doses of fludarabine (30 mg/m²) on days –5, –4, and –3, followed by an infusion of C-CAR088 on day 0. Doses of 1.0×10⁶, 3.0×10⁶, and 6.0×10⁶ CAR T cells/kg (±20%) were tested in the dose-escalation cohorts and expansion cohorts. The primary endpoint was treatment safety, including the rate of treatment-emergent adverse events after cell infusion. Secondary endpoints were the overall response rate and progression-free survival. The exploratory endpoints were the quantification of C-CAR088 CAR T cells, selection of cytokines and chemokines in blood, and measurement of tumor BCMA expression.

Results

As of July 2, 2021, 31 patients had been infused with C-CAR088. Any grade cytokine release syndrome (CRS) occurred in 29 patients (93.5%), and grade 3 CRS occurred in 3 patients (9.7%). One patient from the high-dose group (4.5–6.0×10⁶ CAR T cells/kg) developed grade 1 neurotoxicity. No dose-limiting toxicities were observed in any dose group, and all adverse events were reversible after proper management. The overall response, stringent complete response, complete response (CR), and very good partial response rates were 96.4%, 46.4%, 10.7%, and 32.1%, respectively. The CR rate in the medium-dose (3.0×10⁶ CAR T cells/kg) and high-dose (4.5–6.0×10⁶ CAR T cells/kg) groups was 54.5% and 71.4%, respectively. In the CR group, 15 (93.7%) patients achieved minimal residual disease (MRD) negativity (test sensitivity >1/10⁻⁵). All seven patients with double-hit or triple-hit multiple myeloma achieved MRD-negative CR.

Conclusions

The present study demonstrated that C-CAR088 had a good safety profile and high antitumor activity in patients with RRMM, constituting a promising treatment option for RRMM.

Trial registration number

NCT03815383, NCT03751293, NCT04295018, and NCT04322292.

T-Cell-Based Cellular Immunotherapy of Multiple Myeloma: Current Developments

Simple Summary

Over the past two decades, there has been significant progress in the treatment of multiple myeloma. Starting with the approval of bortezomib and lenalidomide, followed by newer agents in the same classes, monoclonal antibodies, and most recently idecabtagene vicleucel and ciltacabtagene autoleucel, which are genetically engineered autologous T-cell-based therapies, our view of this disease has changed from incurable to controllable and potentially curable. In addition to multiple myeloma and B-cell lymphomas, T-cell-based therapies are also actively investigated in various types of hematological and non-hematological malignancies and are considered one of the most impactful evolutions in cancer therapeutics. This review aims to summarize existing data regarding the efficacy, toxicity, and management of unique adverse events in T-cell-based therapies that are both clinically available and under investigation. We will also address undergoing efforts to improve the survival outcomes of multiple myeloma patients through this treatment modality.

Abstract

T-cell-based cellular therapy was first approved in lymphoid malignancies (B-cell acute lymphoblastic leukemia and large B-cell lymphoma) and expanding its investigation and application both in hematological and non-hematological malignancies. Two anti-BCMA (B cell maturation antigen) CAR (Chimeric Antigen Receptor) T-cell therapies have been recently approved for relapsed and refractory multiple myeloma with excellent efficacy even in the heavily pre-treated patient population. This new therapeutic approach significantly changes our practice; however, there is still room for further investigation to optimize antigen receptor engineering, cell harvest/selection, treatment sequence, etc. They are also associated with unique adverse events, especially CRS (cytokine release syndrome) and ICANS (immune effector cell-associated neurotoxicity syndrome), which are not seen with other anti-myeloma therapies and require expertise for management and prevention. Other T-cell based therapies such as TCR (T Cell Receptor) engineered T-cells and non-genetically engineered adoptive T-cell transfers (Vγ9 Vδ2 T-cells and Marrow infiltrating lymphocytes) are also actively studied and worth attention. They can potentially overcome therapeutic challenges after the failure of CAR T-cell therapy through different mechanisms of action. This review aims to provide readers clinical data of T-cell-based therapies for multiple myeloma, management of unique toxicities and ongoing investigation in both clinical and pre-clinical settings.

The surfaceome of multiple myeloma cells suggests potential immunotherapeutic strategies and protein markers of drug resistance

The myeloma surface proteome (surfaceome) determines tumor interaction with the microenvironment and serves as an emerging arena for therapeutic development. Here, we use glycoprotein capture proteomics to define the myeloma surfaceome at baseline, in drug resistance, and in response to acute drug treatment. We provide a scoring system for surface antigens and identify CCR10 as a promising target in this disease expressed widely on malignant plasma cells. We engineer proof-of-principle chimeric antigen receptor (CAR) T-cells targeting CCR10 using its natural ligand CCL27. In myeloma models we identify proteins that could serve as markers of resistance to bortezomib and lenalidomide, including CD53, CD10, EVI2B, and CD33. We find that acute lenalidomide treatment increases activity of MUC1-targeting CAR-T cells through antigen upregulation. Finally, we develop a miniaturized surface proteomic protocol for profiling primary plasma cell samples with low inputs. These approaches and datasets may contribute to the biological, therapeutic, and diagnostic understanding of myeloma.

Harnessing the T Cell to Treat Multiple Myeloma: Dawn of a New Therapeutic Paradigm

Multiple myeloma is an incurable hematologic malignancy. The typical disease course for myeloma patients is characterized by initial response to treatment followed by eventual development of resistance. Subsequent cycles of remission and relapse proceed as long as patients have new lines of therapy available to them. This reality has prompted development of many novel immunotherapeutics. Many of these drugs exploit the cytotoxic capabilities of the patients' own T cells, effectively redirecting them to myeloma cells that are otherwise evading immune attack. Approaches including CAR T cell therapy and bispecific antibodies have displayed impressive efficacy in clinical trials for myeloma patients. This review examines the different approaches that utilize T cells in multiple myeloma therapy and investigates the benefits and risks of these exciting new strategies.

CAR-T cells for cancer immunotherapy-the barriers ahead and the paths through

This review discusses the major concerns and changes emerged during the rapidly extended clinical application of chimeric antigen receptor (CAR) T therapy based on our experience and understanding. In the past decades, the CAR-T cells have been questioned, sequentially, about their capability of inducing initial remission, their safety profile, their ability to sustain long-term persistence and response, and their potential to be industrialized. Significant advances, novel targeting strategies, innovative molecular structure, fine tuning of both CAR-T and host immune system, combination with other therapies, streamlined manufacturing, and etc., have been made to overcome these challenges. Although not perfectly resolved, rational pathways have been proposed to pass through the barriers. Here, we present the recent achievements on these pathways, and look into the possible future directions.

CD229 (Ly9) a Novel Biomarker for B-Cell Malignancies and Multiple Myeloma

CD229 (Ly9) homophilic receptor, which belongs to the SLAM family of cell-surface molecules, is predominantly expressed on B and T cells. It acts as a signaling molecule, regulating lymphocyte homoeostasis and activation. Studies of CD229 function indicate that this receptor functions as a regulator of the development of marginal-zone B cells and other innate-like T and B lymphocytes. The expression on leukemias and lymphomas remains poorly understood due to the lack of CD229 monoclonal antibodies (mAb) for immunohistochemistry application (IHC). In this study, we used a new mAb against the cytoplasmic region of CD229 to study the expression of CD229 on normal tissues and B-cell malignancies, including multiple myeloma (MM), using tissue microarrays. We showed CD229 to be restricted to hematopoietic cells. It was strongly expressed in all cases of MM and in most marginal-zone lymphomas (MZL). Moderate CD229 expression was also found in chronic lymphocyte leukemia (CLL), follicular (FL), classic mantle-cell (MCL) and diffuse large B-cell lymphoma. Given the high expression on myeloma cells, we also analyzed for the presence of soluble CD229 in the sera of these patients. Serum levels of soluble CD229 (sCD229) at the time of diagnosis in MM patients could be useful as a prognostic biomarker. In conclusion, our results indicate that CD229 represents not only a useful biomarker but also an attractive therapeutic target.

Targeting BCMA to Treat Multiple Myeloma: Updates From the 2021 ASH Annual Meeting

With the gradual improvement of treatment regimens, the survival time of multiple myeloma (MM) patients has been significantly prolonged. Even so, MM is still a nightmare with an inferior prognosis. B-cell maturation antigen (BCMA) is highly expressed on the surface of malignant myeloma cells. For the past few years, significant progress has been made in various BCMA-targeted immunotherapies for treating patients with RRMM, including anti-BCMA mAbs, antibody-drug conjugates, bispecific T-cell engagers, and BCMA-targeted adoptive cell therapy like chimeric antigen receptor (CAR)-T cell. The 63rd annual meeting of the American Society of Hematology updated some information about the application of BCMA in MM. This review summarizes part of the related points presented at this conference.

Allogeneic Anti-BCMA CAR T Cells Are Superior to Multiple Myeloma-derived CAR T Cells in Preclinical Studies and May Be Combined with Gamma Secretase Inhibitors

Multiple myeloma remains an incurable plasma cell malignancy despite the rapidly evolving treatment landscape. Chimeric antigen receptor T cells targeted against BCMA have recently shown great promise in relapsed refractory multiple myeloma; however, all patients ultimately still progress from their disease. Lack of CAR T-cell persistence, impaired T-cell fitness in autologous CAR T-cell products and the presence of an immunosuppressive bone marrow (BM) microenvironment are contributory factors to treatment failure. We generated anti-BCMA CAR T cells from healthy donors (HD) and patients with multiple myeloma at different stages of disease to compare their T-cell profile, fitness, and cytotoxic activity in preclinical studies. We also used an ex vivo assay with multiple myeloma BM biopsies from distinct genomic subgroups to test the efficacy of HD-derived CAR T cells in a clinically relevant model. HD volunteers showed increased T-cell counts, higher CD4/CD8 ratio, and expanded naïve T-cell population compared with patients with multiple myeloma. After anti-BCMA CAR T-cell production, patients with relapsed multiple myeloma had lower frequencies of CAR⁺ T cells, decreased central memory phenotype, and increased checkpoint inhibitory markers compared with HD-derived products, which compromised their expansion and cytotoxicity against multiple myeloma cells in vitro. Importantly, HD-derived CAR T cells efficiently killed primary multiple myeloma cells within the BM microenvironment of different multiple myeloma genomic subgroups and their cytotoxic activity could be boosted with gamma secretase inhibitors. In conclusion, allogeneic anti-BCMA CAR T cells are a potential therapeutic strategy for patients with relapsed multiple myeloma and should be further developed in the clinic.

Significance

Multiple myeloma is an incurable cancer of the plasma cells. A new therapy with anti-BCMA CAR T cells - the patient's own T cells genetically engineered to find and kill myeloma cancer cells - has shown encouraging results. Unfortunately, patients still relapse. In this study, we propose to use T cells from HD volunteers, which have a stronger T-cell fitness, higher cancer killing capacity, and are ready to be administered when needed.

Chimeric antigen receptor T-cells, bispecific antibodies, and antibody-drug conjugates for multiple myeloma: An update

Patients with multiple myeloma who are refractory to currently available effective therapies have short expected survival. Modalities harvesting the knowledge of the immune characteristics and microenvironment of myeloma such as chimeric antigen receptor (CAR) T-lymphocytes, bispecific antibodies (bsAbs), and antibody-drug conjugates (ADCs) have shown potential in early phase trials. Based on data from phase 2 studies, idecabtagene vicleucel (ide cel), an anti-B-cell maturation antigen CAR T-product and belantamab mafodotin (belamaf), an ADC are currently approved in the relapsed/refractory setting. bsAbs have shown promise with quick and deep responses. In this review, we summarize the available evidence on these treatments from clinical trials.

Chimeric Antigen Receptor T-Cell Therapy in Lung Cancer: Potential and Challenges

Chimeric antigen receptor T (CAR-T) cell therapy has exhibited a substantial clinical response in hematological malignancies, including B-cell leukemia, lymphoma, and multiple myeloma. Therefore, the feasibility of using CAR-T cells to treat solid tumors is actively evaluated. Currently, multiple basic research projects and clinical trials are being conducted to treat lung cancer with CAR-T cell therapy. Although numerous advances in CAR-T cell therapy have been made in hematological tumors, the technology still entails considerable challenges in treating lung cancer, such as on−target, of−tumor toxicity, paucity of tumor-specific antigen targets, T cell exhaustion in the tumor microenvironment, and low infiltration level of immune cells into solid tumor niches, which are even more complicated than their application in hematological tumors. Thus, progress in the scientific understanding of tumor immunology and improvements in the manufacture of cell products are advancing the clinical translation of these important cellular immunotherapies. This review focused on the latest research progress of CAR-T cell therapy in lung cancer treatment and for the first time, demonstrated the underlying challenges and future engineering strategies for the clinical application of CAR-T cell therapy against lung cancer.

Trial watch: intratumoral immunotherapy

While chemotherapy and radiotherapy remain the first-line approaches for the management of most unresectable tumors, immunotherapy has emerged in the past two decades as a game-changing treatment, notably with the clinical success of immune checkpoint inhibitors. Immunotherapies aim at (re)activating anticancer immune responses which occur in two main steps: (1) the activation and expansion of tumor-specific T cells following cross-presentation of tumor antigens by specialized myeloid cells (priming phase); and (2) the immunological clearance of malignant cells by these antitumor T lymphocytes (effector phase). Therapeutic vaccines, adjuvants, monoclonal antibodies, cytokines, immunogenic cell death-inducing agents including oncolytic viruses, anthracycline-based chemotherapy and radiotherapy, as well as adoptive cell transfer, all act at different levels of this cascade to (re)instate cancer immunosurveillance. Intratumoral delivery of these immunotherapeutics is being tested in clinical trials to promote superior antitumor immune activity in the context of limited systemic toxicity.

Relapsed/Refractory Multiple Myeloma in 2020/2021 and Beyond

Despite the challenges imposed by the COVID-19 pandemic, exciting therapeutic progress continues to be made in MM. New drug approvals for relapsed/refractory (RR)MM in 2020/2021 include the second CD38 monoclonal antibody, isatuximab, the first BCMA-targeting therapy and first-in-class antibody-drug conjugate (ADC) belantamab mafodotin, the first BCMA-targeting CAR T cell product Idecabtagen-Vicleucel (bb2121, Ide-Cel), the first in-class XPO-1 inhibitor selinexor, as well as the first-in-class anti-tumor peptide-drug conjugate, melflufen. The present introductory article of the Special Issue on "Advances in the Treatment of Relapsed and Refractory Multiple Myeloma: Novel Agents, Immunotherapies and Beyond" summarizes the most recent registration trials and emerging immunotherapies in RRMM, gives an overview on latest insights on MM genomics and on tumor-induced changes within the MM microenvironment, and presents some of the most promising rationally derived future therapeutic strategies.

Clinical experience of CAR T cells for multiple myeloma

Important advances in the treatment landscape of multiple myeloma (MM) had been seen over the past two decades leading to improved overall survival but despite the progress multiple myeloma is still considered incurable and the prognosis of the pentarefractory patients have been poor. The development of immunotherapy and in particular adoptive cell therapy with chimeric antigen receptor (CAR) T cells have dramatically improved the outcomes of heavily pretreated relapsed/refractory MM patients. The bulk of CAR T-cell constructs currently in clinical development target the B-cell maturation antigen (BCMA) and to date only idecabtagene vicleucel (ide-cel) is approved by the Food and Drug Administration (FDA) for commercial use in adult patients with relapsed or refractory MM based on the promising clinical responses and positive safety record shown in the pivotal KarMMa study. This review focus on the development of CAR T-cell therapy for multiple myeloma as well as a brief review of the mechanisms of resistance, toxicity and new approaches under development.

Real-world data on survival improvement in patients with multiple myeloma treated at a single institution over a 45-year period

The prognostic landscape of multiple myeloma (MM) has evolved significantly over the last few decades. There are, however, few data measuring such improvement in real-world patients. This study aimed to investigate trends in survival improvement over 45 years, and the associated clinical factors, in an unselected population of patients with MM. Between 1970 and 2015, 1 161 MM patients were included. Patients were classified into three calendar periods (1970-1984, 1985-1999, and 2000-2015), according to the treatment received; polychemotherapy, autologous stem cell transplantation, and novel drugs respectively. We analysed relative survival (RS) to accurately evaluate MM-related death rates after excluding the mortality expected in the general population. RS at five years increased from 27% in 1970-1984 to 38% and 56% in the next two calendar periods respectively. The improvement to survival was greater in the younger population, but it was also observed in elderly patients and those with poor performance status and more advanced disease. Although myeloma is still a non-curable disease, encouraging results have been observed in the last decades. Progress is expected to continue with the use of new generations of anti-myeloma drugs, and will, hopefully, be documented in real-world patients by the appropriate population-based studies.

Effect of Lactobacillus fermentum HFY03 on the Antifatigue and Antioxidation Ability of Running Exhausted Mice

Yak yogurt is mainly produced in Qinghai-Tibet Plateau. It is a kind of naturally fermented dairy product. It contains abundant microorganisms. Lactobacillus fermentum (LF) HFY03 is a lactic acid bacteria derived from it. Our main research content is to study the influence of LF-HFY03 on the antifatigue and antioxidation ability of running exhausted mice. We gave different doses of LF-HFY03 to mice by gavage for 4 weeks. We selected vitamin C as the positive control group, mainly to study the relationship between antioxidant capacity and fatigue resistance and LF-HFY03 in mice with running exhaustion. The results showed that LF-HFY03 and vitamin C could significantly improve the running time of mice. And with the increase in LF-HFY03 concentration, the exhaustion time of mice was also extended. LF-HFY03 can reduce the content of urea nitrogen and lactic acid and also can increase the content of free fatty acids and liver glycogen. The levels of alanine aminotransferase, serum creatine kinase, and aspartate aminotransferase in mice decreased gradually as the antioxidant peptide level of walnut albumin increased. LF-HFY03 can reduce malondialdehyde (MDA) levels in a quantification-dependent manner and can also increase catalase (CAT) and superoxide dismutase (SOD) levels. LF-HFY03 can also increase the expressions of CAT mRNA, Cu/Zn-SOD, and Mn-SOD in the liver of mice. At the same time, LF-HFY03 can also increase the expression of protein of threonine transporter 1 (AST1)/alanine/cysteine/serine, mRNA, nNOS, and eNOS. At the same time, the solution could reduce the expression of TNF-α, syncytin-1, and inducible nitric oxide synthase (iNOS). The results showed that LF-HFY03 has a high development and application prospect as an antifatigue probiotic nutritional supplement.

An Overview of Organoid and 3-Dimensional Models in Multiple Myeloma

ABSTRACT

Multiple myeloma is a hematological malignancy of differentiated B cells that resides primarily in bone marrow niches. Its interaction with the microenvironment is known to provide a survival advantage and plays an important role in drug resistance. Despite the increased efficacy of new treatment drugs, clinical results oftentimes fall short of in vitro observations, and this disease remains incurable. Conventional 2-dimensional cultures used to perform chemosensitivity assays and the established multiple myeloma cells lines commonly used do not replicate the conditions seen in vivo. This review presents various 3-dimensional culture platforms for myeloma that attempt to overcome this obstacle by incorporating aspects of the tumor microenvironment. The unique features of each model and contributions they have provided in personalized medicine, tumor physiology, and chemosensitivity assays will be summarized.

CAR-T after Stem Cell Transplantation in B-Cell Lymphoproliferative Disorders: Are They Really Autologous or Allogenic Cell Therapies?

Allogenic hematopoietic stem cell transplantation (allo-HSCT) is one of the standard treatments for B-cell lymphoproliferative disorders; however, deep relapses are common after an allo-HSCT, and it is associated with poor prognosis. A successful approach to overcome these relapses is to exploit the body's own immune system with chimeric antigen receptor (CAR) T-cells. These two approaches are potentially combinatorial for treating R/R B-cell lymphoproliferative disorders. Several clinical trials have described different scenarios in which allo-HSCT and CAR-T are successively combined. Further, for all transplanted patients, assessment of chimerism is important to evaluate the engraftment success. Nonetheless, for those patients who previously received an allo-HSCT there is no monitorization of chimerism before manufacturing CAR T-cells. In this review, we focus on allo-HSCT and CAR-T treatments and the different sources of T-cells for manufacturing CAR T-cells.

Characterization of the Therapeutic Effects of Novel Chimeric Antigen Receptor T Cells Targeting CD38 on Multiple Myeloma

Multiple myeloma (MM) is a tumor type characterized by the unregulated proliferation of clonal plasma cells in the bone marrow. Immunotherapy based on chimeric antigen receptor T cell (CAR-T) therapy has achieved exciting success in the treatment of hematological malignant tumors. CD38 is highly and evenly expressed in MM and is an attractive target for MM treatment. Here, we successfully constructed two novel second-generation CAR-T cells targeting CD38 by retroviral vector transduction. CD38 CAR-T cells could be activated effectively after stimulation with CD38-positive tumor cells and secrete cytokines such as IFN-γ and TNF-α to promote tumor cell apoptosis in in vitro experiments. Real-time fluorescence monitoring experiments, luciferase detection experiments and flow cytometry experiments revealed the efficient and specific killing abilities of CD38 CAR-T cells against CD38-positive tumor cells. The proliferation ability of CD38 CAR-T cells in vitro was higher than that of untransduced T cells. Further antitumor experiments in vivo showed that CD38 CAR-T cells could be quickly activated to secrete IFN-γ and eliminate tumors. Thus, novel CD38-targeted second-generation CAR-T cells have efficient and specific antitumor activity and may become a novel therapy for the clinical treatment of MM.

Immunotherapy of Multiple Myeloma: Promise and Challenges

Whereas the treatment of MM was dependent solely on alkylating agents and corticosteroids during the prior three decades, the landscape of therapeutic measures to treat the disease began to expand enormously early in the current century. The introduction of new classes of small-molecule drugs, such as proteasome blockers (bortezomib and carfilzomib), immunomodulators (lenalidomide and pomalidomide), nuclear export inhibitors (selinexor), and histone deacetylase blockers (panobinostat), as well as the application of autologous stem cell transplantation (ASCT), resulted in a seismic shift in how the disease is treated. The picture changed dramatically once again starting with the 2015 FDA approval of two monoclonal antibodies (mAbs) - the anti-CD38 daratumumab and the anti-SLAMF7 elotuzumab. Daratumumab, in particular, has had a great impact on MM therapy and today is often included in various regimens to treat the disease, both in newly diagnosed cases and in the relapse/refractory setting. Recently, other immunotherapies have been added to the arsenal of drugs available to fight this malignancy. These include isatuximab (also anti-CD38) and, in the past year, the antibody-drug conjugate (ADC) belantamab mafodotin and the chimeric antigen receptor (CAR) T-cell product idecabtagene vicleucel (ide-cel). While the accumulated benefits of these newer agents have resulted in a doubling of the disease's five-year survival rate to more than 5 years and improved quality of life, the disease remains incurable. Almost without exception patients experience relapse and/or become refractory to the drugs used, making the search for innovative therapies all the more essential. This review covers the current scope of anti-myeloma immunotherapeutic agents, both those in clinical use and on the horizon, including naked mAbs, ADCs, bi- and multi-targeted mAbs, and CAR T-cells. Emphasis is placed on the benefits of each along with the challenges that need to be overcome if MM is to be considered curable in the future.

Flow cytometric myeloma measurable residual disease testing in the era of targeted therapies

Therapies in myeloma are rapidly advancing with a host of new targeted therapies coming to market. While these drugs offer significant survival benefits and better side-effect profiles compared with conventional chemotherapeutics, they raise significant difficulties in monitoring post-therapy disease status by flow cytometry due to assay interference and/or selection of phenotypically different sub-clones. The principal culprit, anti-CD38 monoclonal antibodies, limits the ability to detect plasma cells based on classical CD38/CD45 gating. Other markers, such as CD138, are known to be suboptimal by flow cytometry. Various techniques have been proposed to overcome this problem. The most promising of these techniques has been the marker VS38c, a monoclonal antibody targeting an endoplasmic reticulum protein which has shown high sensitivity for plasma cells. Alternative techniques for gating plasma cells, while variably effective in the near term are already the subject of several targeted therapies rendering their usefulness limited in the longer term. Likewise, future targets of these therapies may render present aberrancy markers ineffective in MRD testing. These therapies pose challenges that must be overcome with new markers and novel panels in order for flow cytometric MRD testing to remain relevant.

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.

Cellular immunotherapy for hematological malignancy: recent progress and future perspectives

Advancements in the field of cellular immunotherapy have accelerated in recent years and have changed the treatment landscape for a variety of hematologic malignancies. Cellular immunotherapy strategies exploit the patient's immune system to kill cancer cells. The successful use of CD19 chimeric antigen receptor (CAR) T-cells in treating B-cell malignancies is the paradigm of this revolution, and numerous ongoing studies are investigating and extending this approach to other malignancies. However, resistance to CAR-T-cell therapy and non-durable efficacy have prevented CAR-T-cells from becoming the ultimate therapy. Because natural killer (NK) cells play an essential role in antitumor immunity, adoptively transferred allogeneic NK and CAR-modified NK cell therapy has been attempted in certain disease subgroups. Allogenic hematopoietic stem cell transplantation (allo-HSCT) is the oldest form of cellular immunotherapy and the only curative option for hematologic malignancies. Historically, the breadth of application of allo-HSCT has been limited by a lack of identical sibling donors (ISDs). However, great strides have recently been made in the success of haploidentical allografts worldwide, which enable everyone to have a donor. Haploidentical donors can achieve comparable outcomes to those of ISDs and even better outcomes in certain circumstances because of a stronger graft vs. tumor effect. Currently, novel strategies such as CAR-T or NK-based immunotherapy can be applied as a complement to allo-HSCT for curative effects, particularly in refractory cases. Here, we introduce the developments in cellular immunotherapy in hematology.

IL-15 Enhances the Persistence and Function of BCMA-Targeting CAR-T Cells Compared to IL-2 or IL-15/IL-7 by Limiting CAR-T Cell Dysfunction and Differentiation

Simple Summary

T cells modified with a chimeric antigen receptor (CAR) that targets BCMA, a protein expressed on malignant plasma cells, represent a novel treatment option for multiple myeloma. Despite initially eliminating the disease, the function of BCMA-directed CAR-T cells diminishes within a year of administration, leading to disease relapse. The aim of this research was to alter the cytokines used in the ex vivo expansion of anti-BCMA CAR-T cells, to avoid the development of an unfavorable phenotype that would impair in vivo function. We discovered that CAR-T cells expanded with IL-15 had reduced dysfunction and enhanced persistence compared to those grown with IL-2 or a combination of IL-15 and IL-7, which resulted in longer and improved anti-tumor responses in a mouse model. Therefore, the use of IL-15 alone in place of IL-2 or IL-15/IL-7 should be considered when designing CAR-T cell production protocols, to improve the duration of patient responses.

Abstract

Chimeric antigen receptor (CAR)-T cell immunotherapy has revolutionized the treatment of B-lymphoid malignancies. For multiple myeloma (MM), B-cell maturation antigen (BCMA)-targeted CAR-T cells have achieved outstanding complete response rates, but unfortunately, patients often relapse within a year of receiving the therapy. Increased persistence and reduced dysfunction are crucial features that enhance the durability of CAR-T cell responses. One of the factors that influence CAR-T cell in vivo longevity and loss of function, but which has not yet been extensively studied for BCMA-directed CAR-T cells, are the cytokines used during their production. We here compared the impact of IL-2, IL-15 and a combination of IL-15/IL-7 on the phenotype and function of ARI2h, an academic BCMA-directed CAR-T cell that is currently being administered to MM patients. For this study, flow cytometry, in vitro cytotoxicity assays and analysis of cytokine release were performed. In addition, ARI2h cells expanded with IL-2, IL-15, or IL-15/IL-7 were injected into MM tumor-bearing mice to assess their in vivo efficacy. We demonstrated that each of the cytokine conditions was suitable for the expansion of ARI2h cells, with clear in vitro activity. Strikingly, however, IL-15-produced ARI2h cells had improved in vivo efficacy and persistence. When explored further, it was found that IL-15 drove a less-differentiated ARI2h phenotype, ameliorated parameters related to CAR-T cell dysfunction, and lowered the release of cytokines potentially involved in cytokine release syndrome and MM progression. Moreover, we observed that IL-15 was less potent in inducing T cell senescence and DNA damage accumulation, both of which may contribute to an unfavorable CAR-T cell phenotype. These findings show the superiority of IL-15 to IL-2 and IL-15/IL-7 in the quality of anti-BCMA CAR-T cells, particularly their efficacy and persistence, and as such, could improve the duration of responses if applied to the clinical production of CAR-T cells for patients.

The Effect of Lactobacillus plantarum CQPC02 on Fatigue and Biochemical Oxidation Levels in a Mouse Model of Physical Exhaustion

Chinese Sichuan pickle is a fermented food rich in microorganisms. Microorganisms have the potential to become an important new form of potent future therapeutic capable of treating human disease. Selecting vitamin C as a positive control, a lactic acid bacteria (Lactobacillus plantarum CQPC02, LP-CQPC02) isolated from Sichuan pickle was given to mice over 4 weeks to investigate the effect of CQPC02 on fatigue levels and biochemical oxidation phenomena in exercise-exhausted Institute of Cancer Research (ICR) mice. The fatigue model was established by forced swimming of mice, the levels of hepatic glycogen, skeletal muscle glycogen, lactic acid, blood urea nitrogen and free fatty acid were measured by physicochemical methods, serum serum creatine kinase (CK), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) levels were measured by kits, the histopathological changes in the livers of mice were observed by H&E slicing, and the mRNA changes in the livers and skeletal muscles were observed by quantitative polymerase chain reaction (qPCR). Both vitamin C and LP-CQPC02 increased swimming exhaustion time. The concentration of LP-CQPC02 and exhaustion time were positively correlated. LP-CQPC02 also increased liver glycogen, skeletal muscle glycogen and free fatty acid content in mice and reduced lactic acid and blood urea nitrogen content in a dose-dependent manner. As walnut albumin antioxidant peptide concentration increased, levels of mouse CK, AST, and AST gradually decreased. LP-CQPC02 increased SOD and CAT levels and decreased MDA levels in a dose-dependent fashion. LP-CQPC02 up-regulated expression of mRNA encoding copper/zinc-superoxide dismutase (Cu/Zn-SOD), manganese-superoxide dismutase (Mn-SOD), and CAT in swimming exhaustion mouse liver tissue. LP-CQPC02 also up-regulated alanine/serine/cysteine/threonine transporter 1 (ASCT1) expression while down-regulating syncytin-1, inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-α) expression in swimming exhaustion mouse skeletal muscle. Overall, LP-CQPC02 had a clear anti-fatigue and anti-oxidation effect. This suggests that LP-CQPC02 can be developed as a microbiological therapeutic agent.

Overcoming the Immunosuppressive Tumor Microenvironment in Multiple Myeloma

Simple Summary

This article provides a comprehensive review of new and emerging treatment strategies against multiple myeloma that employ precision medicines and/or drugs capable of improving the ability of the immune system to prevent or slow down the progression of multiple myeloma. These rationally designed new treatment methods have the potential to change the therapeutic landscape in multiple myeloma and improve the long-term survival outcome.

Abstract

SeverFigurel cellular elements of the bone marrow (BM) microenvironment in multiple myeloma (MM) patients contribute to the immune evasion, proliferation, and drug resistance of MM cells, including myeloid-derived suppressor cells (MDSCs), tumor-associated M2-like, “alternatively activated” macrophages, CD38+ regulatory B-cells (Bregs), and regulatory T-cells (Tregs). These immunosuppressive elements in bidirectional and multi-directional crosstalk with each other inhibit both memory and cytotoxic effector T-cell populations as well as natural killer (NK) cells. Immunomodulatory imide drugs (IMiDs), protease inhibitors (PI), monoclonal antibodies (MoAb), adoptive T-cell/NK cell therapy, and inhibitors of anti-apoptotic signaling pathways have emerged as promising therapeutic platforms that can be employed in various combinations as part of a rationally designed immunomodulatory strategy against an immunosuppressive tumor microenvironment (TME) in MM. These platforms provide the foundation for a new therapeutic paradigm for achieving improved survival of high-risk newly diagnosed as well as relapsed/refractory MM patients. Here we review the scientific rationale and clinical proof of concept for each of these platforms.

A new decade: novel immunotherapies on the horizon for relapsed/refractory multiple myeloma

INTRODUCTION

Survival in multiple myeloma (MM) has improved due to the ongoing revolution of therapeutic approaches. Nevertheless, many patients relapse, and additional novel approaches are required to prolong remissions and prevent disease progression.

AREAS COVERED

Considering the success of monoclonal antibodies (mAbs) against CD38 and SLAMF7 in relapsed/refractory MM (R/R MM), additional antigens expressed on malignant plasma cells are being investigated as treatment targets. Among these, many trials are focusing on B cell maturation antigen (BCMA), using either antibody-drug conjugates (ADCs), bispecific T cell engagers (TCE), or chimeric antigen receptor T cells (CAR-T). Other potential targets include the myeloma markers CD138, GPRC5D, FcRH5, the plasma cell differentiating factors APRIL, TACI and BAFF, and the immune checkpoint proteins CD47 and TIGIT. Additionally, novel immunomodulatory Cereblon E3 Ligase Modulators (CELMoDs) offer the potential to overcome resistance to conventional immunomodulatory agents. Based upon PubMed and abstract searches primarily from the past 4 years, here we review the data supporting novel immunotherapies for R/R MM.

EXPERT OPINION

Overcoming disease resistance remains a challenge in R/R MM. Novel therapeutic approaches targeting MM antigens and/or enhancing immune cell function offer the potential to prolong survival and are actively being investigated in clinical trials.

Expert review on soft-tissue plasmacytomas in multiple myeloma: definition, disease assessment and treatment considerations

In this review, two types of soft-tissue involvement in multiple myeloma are defined: (i) extramedullary (EMD) with haematogenous spread involving only soft tissues and (ii) paraskeletal (PS) with tumour masses arising from skeletal lesions. The incidence of EMD and PS plasmacytomas at diagnosis ranges from 1·7% to 4·5% and 7% to 34·4% respectively. EMD disease is often associated with high-risk cytogenetics, resistance to therapy and worse prognosis than in PS involvement. In patients with PS involvement a proteasome inhibitor-based regimen may be the best option followed by autologous stem cell transplantation (ASCT) in transplant eligible patients. In patients with EMD disease who are not eligible for ASCT, a proteasome inhibitor-based regimen such as lenalidomide-bortezomib-dexamethasone (RVD) may be the best option, while for those eligible for high-dose therapy a myeloma/lymphoma-like regimen such as bortezomib, thalidomide and dexamethasone (VTD)-RVD/cisplatin, doxorubicin, cyclophosphamide and etoposide (PACE) followed by SCT should be considered. In both EMD and PS disease at relapse many strategies have been tried, but this remains a high-unmet need population.

Early Time-to-Tocilizumab after B Cell Maturation Antigen-Directed Chimeric Antigen Receptor T Cell Therapy in Myeloma

Preemptive administration of tocilizumab (toci) to manage cytokine release syndrome (CRS) after chimeric antigen receptor T cell (CAR-T) therapy may reduce rates of serious CRS but conversely may worsen neurotoxicity or risk of infections. Optimal toci administration strategies for patients with relapsed/refractory multiple myeloma (RRMM) receiving B cell maturation antigen (BCMA)-directed CAR-T therapies have not been evaluated. The objective of this study was to identify whether shorter time-to-toci intervals (hours between first fever attributed to CRS and first dose of toci) have any impact on therapy-related toxicities or clinical outcomes among patients with RRMM receiving BCMA-directed CAR-T therapies. We retrospectively analyzed our institution's experience with 4 BCMA-directed CAR-T therapies (idecabtagene vicleucel, bb21217, ciltacabtagene autoleucel, and orvacabtagene autoceucel) for RRMM over a 3-year period ending in June 2020. We divided patients based on the administration of toci and median time-to-toci interval into early-toci (time-to-toci ≤50th percentile), late-toci (time-to-toci >50th percentile), and no-toci (no toci received) groups. We compared the early-toci and late-toci groups with regard to patient characteristics, weight-based CAR-T toxicities, selected toxicities (CRS, neurotoxicity, macrophage activation syndrome, or infections), and clinical outcomes. Of 50 analyzed patients with a median follow-up of 15.3 months, 76% (n = 38) received ≥1 dose of toci (range, 1 to 3) and were classified into early-toci (time-to-toci ≤12 hours) or late-toci (time-to-toci >12 hours) groups. The 2 groups (n = 19 each) had similar CRS grade distributions, hours to CRS onset, CRS-related biomarkers, and incidences of neurotoxicity or severe infections; however, weight-adjusted CAR-T cell doses were higher in the early-toci group (median 5.99 versus 3.80 × 10⁶ cells/kg, P < 0.01). Peak CRS grades (range, 0 to 2) using American Society for Transplantation and Cellular Therapy consensus criteria, neurotoxicity rates, and rates of severe infections were similar between groups; however, the median CRS duration was 18.6 hours for the early-toci group versus 84.7 hours for the late-toci group. The median progression-free survival was 35.7 months in the early-toci group and 13.2 months in the late-toci group. While limited by small sample size and known confounders such as CAR-T cell dose, our analysis suggests that preemptive toci strategies for CRS management with BCMA-directed CAR-T therapy-specifically, toci administration within 12 hours of the first fever attributed to CRS-do not appear to increase rates of therapy-related toxicities or compromise efficacy. However, total CRS duration may be shorter with early-toci workflows. Prospective validation of our findings may lead to improved safety and cost-effectiveness profiles for CAR-T therapy in RRMM.