anti-BCMA Chimeric Antigen Receptor Research Articles

Efficacy and Safety of BCMA-CAR-T Cell Therapy in Relapsed/Refractory Extramedullary Plasmacytoma: Exploring the Role of Consolidation Therapy

Alloimmune Defense Receptor Combined with Genetic Ablation of Adhesion Ligand CD58 Is a Comprehensive Approach to Promote Functional Persistence of Allogeneic Cell Therapies without Conditioning Chemotherapy

Efficacy and Safety of Anti-BCMA Chimeric Antigen Receptor T-Cell (CART) for the Treatment of Relapsed and Refractory AL Amyloidosis

Genomic Determinants of Resistance to Anti-BCMA Chimeric Antigen Receptor T-Cell (CART) Therapies in Patients with Relapsed/Refractory Multiple Myeloma

Chimeric antigen receptor (CAR) T cell therapy has become an important treatment for hematological cancers, and its success has spurred research into CAR T cell therapies for other diseases, including solid tumor cancers and autoimmune diseases. Notably, the development of CAR-based treatments for autoimmune diseases has shown great progress recently. Clinical trials for anti-CD19 and anti-BCMA CAR T cells in treating severe B cell-mediated autoimmune diseases, like systemic lupus erythematosus (SLE), have shown lasting remission thus far. CAR T cells targeting autoreactive T cells are beginning clinical trials for treating T cell mediated autoimmune diseases. Chimeric autoantigen receptor (CAAR) T cells specifically target and eliminate only autoreactive B cells, and they have shown promise in treating mucosal pemphigus vulgaris and MuSK myasthenia gravis. Regulatory CAR T cells have also been developed, which show potential in altering autoimmune affected areas by creating a protective barrier as well as helping decrease inflammation. These new treatments are only the beginning of potential CAR T cell applications in treating autoimmune disease. Novel CAR technologies have been developed that increase the safety, potency, specificity, and efficacy of CAR T cell therapy. Applying these novel modifications to autoimmune CARs has the potential to enhance the efficacy and applicability of CAR therapies to autoimmune disease. This review will detail several recently developed CAR technologies and discuss how their application to autoimmune disease will improve this emerging field. These include logic-gated CARs, soluble protein-secreting CARs, and modular CARs that enable CAR T cell therapies to be more specific, reach a wider span of target cells, be safer for patients, and give a more potent cytotoxic response. Applying these novel CAR technologies to the treatment of autoimmune diseases has the potential to revolutionize this growing application of CAR T cell therapies.

Chimeric antigen receptor (CAR) T-cell therapies have revolutionised the field of haematological malignancies by achieving impressive remission rates in patients with highly refractory haematological malignancies, improving overall survival. To date, six commercial anti-CD19 and anti-BCMA CAR T-cell products have been approved by the Food and Drug Administration (FDA) for the treatment of relapsed/refractory B-cell haematological malignancies and multiple myeloma. The indications for CAR T-cell therapies are gradually expanding, with these therapies being investigated in a variety of diseases, including non-malignant ones. Despite the great success, there are several challenges surrounding CAR T-cell therapies, such as non-durable responses and high-grade toxicities. In addition, a new safety concern was added by the FDA on 28 November 2023 following reports of T-cell malignancies in patients previously treated with either anti-CD19 or anti-BCMA autologous CAR T-cell therapies both in clinical trials and in the real-world setting. Since then, several reports have been published presenting the incidence and analysing the risks of other secondary malignancies after CAR T-cell therapies. In this opinion article, the current landscape of secondary malignancies after CAR T-cell therapies is presented, along with a proposed strategy for future research aiming at potentially diminishing or abrogating the risk of developing secondary malignancies after CAR T-cell therapies.

We attempt to analyze bone marrow findings and correlation with cytopenia(s) after anti-B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell infusion in this study. Relevant clinicopathologic data, including complete blood counts, neutrophil counts, relevant therapy history, and pre- and posttherapy bone marrow evaluations, were studied in 12 patients who received anti-BCMA CAR T-cell therapy. Bone marrow findings after CAR T-cell therapy were available in 6 of 12 cases, 3 of which showed markedly hypocellular marrow with either markedly reduced or essentially absent hematopoiesis. One case showed a hypocellular marrow with trilineage hematopoiesis, while the remaining 2 cases showed persistent involvement by plasma cell myeloma. Reticulin stains did not reveal significant fibrosis. Ten patients had anemia, and 8 patients had leukopenia and thrombocytopenia at day 90 posttherapy. Long-term follow-up showed persistent disease in 10 of 12 cases. Prolonged cytopenias occur in most patients after BCMA CAR T-cell therapy with bone marrow evaluations demonstrating associated marked hypocellularity with minimal or no hematopoiesis without an increase in fibrosis.

Despite being the mainstay of management for cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS), there is limited data regarding the impact of tocilizumab (TCZ) and corticosteroids (CCS) on chimeric antigen receptor (CAR) T-cell efficacy in multiple myeloma (MM). The present study aims to evaluate the prognostic impact of these immunosuppressants in recipients of BCMA- or GPRC5D-directed CAR T cells for relapsed/refractory MM. Our retrospective cohort involved patients treated with commercial or investigational autologous CAR T-cell products at a single institution from March 2017–March 2023. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall response rate (ORR), complete response rate (CRR), and overall survival (OS). In total, 101 patients (91% treated with anti-BCMA CAR T cells and 9% treated with anti-GPRC5D CAR T cells) were analyzed. Within 30 days post-infusion, 34% received CCS and 49% received TCZ for CRS/ICANS management. At a median follow-up of 27.4 months, no significant difference in PFS was observed between CCS and non-CCS groups (log-rank p = 0.35) or between TCZ and non-TCZ groups (log-rank p = 0.69). ORR, CRR, and OS were also comparable between evaluated groups. In our multivariable model, administering CCS with/without TCZ for CRS/ICANS management did not independently influence PFS (HR, 0.74; 95% CI, 0.36–1.51). These findings suggest that, among patients with relapsed/refractory MM, the timely and appropriate use of CCS or TCZ for mitigating immune-mediated toxicities does not appear to impact the antitumor activity and long-term outcomes of CAR T-cell therapy.

Chimeric antigen receptor (CAR) T cell immunotherapy for the treatment of neurological autoimmune diseases is promising, but CAR T cell kinetics and immune alterations after treatment are poorly understood. Here, we performed single-cell multi-omics sequencing of paired cerebrospinal fluid (CSF) and blood samples from patients with neuromyelitis optica spectrum disorder (NMOSD) treated with anti-B cell maturation antigen (BCMA) CAR T cells. Proliferating cytotoxic-like CD8+ CAR T cell clones were identified as the main effectors in autoimmunity. Anti-BCMA CAR T cells with enhanced features of chemotaxis efficiently crossed the blood-CSF barrier, eliminated plasmablasts and plasma cells in the CSF, and suppressed neuroinflammation. The CD44-expressing early memory phenotype in infusion products was potentially associated with CAR T cell persistence in autoimmunity. Moreover, CAR T cells from patients with NMOSD displayed distinctive features of suppressed cytotoxicity compared with those from hematological malignancies. Thus, we provide mechanistic insights into CAR T cell function in patients with neurological autoimmune disease.

Chimeric antigen receptor (CAR) T cell therapy has transformed the treatment landscape of relapsed/refractory multiple myeloma. The current Food and Drug Administration approved CAR T cell therapies idecabtagene vicleucel and ciltacabtagene autoleucel both target B cell maturation antigen (BCMA), which is expressed on the surface of malignant plasma cells. Despite deep initial responses in most patients, relapse after anti-BCMA CAR T cell therapy is common. Investigations of acquired resistance to anti-BCMA CAR T cell therapy are underway. Meanwhile, other viable antigenic targets are being pursued, including G protein-coupled receptor class C group 5 member D (GPRC5D), signaling lymphocytic activation molecule family member 7 (SLAMF7), and CD38, among others. CAR T cells targeting these antigens, alone or in combination with anti-BCMA approaches, appear to be highly promising as they move from preclinical studies to early phase clinical trials. This review summarizes the current data with novel CAR T cell targets beyond BCMA that have the potential to enter the treatment landscape in the near future.

Abstract Background: Chimeric antigen receptor (CAR) T cells targeting B-cell maturation antigen (BCMA) can induce >70% response rates in patients with relapsed/refractory multiple myeloma (RRMM). However, most patients ultimately relapse. There are two FDA-approved CAR T products: ciltacabtagene autoleucel (cilta-cel) and idecabtagene vicleucel (ide-cel), the former having much more durable responses. The mechanisms that mediate more durable responses with these CAR T cells is unknown. Previous studies have shown that specific cell states in the apheresis and infusion products are associated with long-term efficacy of anti-BCMA CAR therapy in MM and the relationship between durability of response and CAR T cell persistence remains unclear. Methods: We analyzed serial bone marrow and PBMC samples from 20 MM patients who received BCMA CAR T therapy, including cilta-cel, ide-cel, and JCARH125. Flow cytometry and single-cell RNAseq were used to evaluate the features of CAR T cells that are associated with durable clinical responses. Results: While CAR T cells were detectable but variable among patients at 1-month post infusion, the frequency of CAR T cells in bone marrow at 1-month post-infusion is positively correlated with progression free survival (PFS) in all MM patients (p=0.009). This association was also evident in patients just treated with cilta-cel (p= 0.008). By 6 months, CAR T cells could still be detected by high-throughput flowcytometry in the cilta-cel-treated patients, but CAR T cells were not detectable in most of the patients receiving the other 2 products. Cilta-cel CAR T cells predominantly possessed an effector-like surface phenotype at 1-moth post infusion in both CD8+ and CD4+ compartments in bone marrow. These CAR T cells shifted to effector memory and central memory T cell states by 6 months, respectively. For ide-cel and JCARH125, patients with more durable responses (>6mos) there was a significantly higher proportion of CAR T cells with CD8+ effector memory-like state at 1-month post infusion. Conclusions: Our data demonstrate that distinct anti-BCMA CAR T cell treatments lead to very different cellular outcomes: Cilta-cel CAR T cell treatment leads to greater expansion and persistence compared to other anti-BCMA CAR T cells. Cilta-cel CAR T cells also shift from the initial effector state to a memory phenotype. These results provide insights into features of more efficacious anti-BCMA CAR T cells that can help guide the future development of more durable treatments for MM. Citation Format: Kai Wu, Karen Law, Guy Ledergor, Chang Liu, Zenghua Fan, Vibha Gurunathan, Averey Lea, Matthew Clark, Serena Kwek, Alexander Cheung, Jeffrey Wolf, Ajai Chari, Anupuma Kumar, Justin Eyquem, Thomas Martin, Lawrence Fong. Expansion and persistence of anti-BCMA CAR T cells correlates with durability of responses in multiple myeloma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3617.

Abstract Introduction Multiple myeloma (MM) is the second most prevalent hematopoietic malignancy with an overall 5-year survival rate of 58%. B cell maturation antigen (BCMA) is selectively expressed on normal and malignant plasma cells, making it an attractive MM target. Anti-BCMA chimeric antigen receptor (CAR) T cell therapy and T cell engagers have shown promise as treatment options for certain MM patients; however, potential toxicities associated with these anti-BCMA therapies, such as cytokine release syndrome (CRS), have limited broader utilization. Much like T cells, natural killer (NK) cells are cytolytic and have demonstrated an innate capacity to reduce tumor burden while exhibiting a more favorable safety profile in clinical testing. To that end, we developed a cryopreserved allogeneic cell therapy comprised of genetically modified human umbilical cord blood-derived (CB) NK cells transduced with a gammaretroviral vector, which incorporates genes for an anti-BCMA CAR and soluble human interleukin-15 (sIL-15). Referred to hereafter as anti-BCMA CAR-NK, it exhibits both innate NK- and CAR-mediated killing in vitro and robust in vivo activity against established MM tumors. Methods CBNK cells were isolated from donor cord blood units, propagated using feeder cells, transduced with a gammaretroviral vector to express an anti-BCMA CAR and soluble human IL-15, and propagated further before harvest and cryopreservation. Donor-equivalent untransduced (UTD) NK cells were generated via the same process but without the transduction step. Cryopreserved anti-BCMA CAR-NK and UTD NK cells were used for in vitro studies, including short-term killing, as well as for evaluation of activity against established MM tumors in vivo using the MM.1S-Luc4 model. Results The anti-BCMA CAR was successfully expressed across all batches of anti-BCMA CAR-NK generated. Results from an in vitro cytotoxicity assay indicated that anti-BCMA CAR-NK kills BCMA expressing MM.1S-Luc4 tumor cells and secretes IFNγ, TNFα, and granzyme B at greater amounts compared to donor-equivalent UTD NK. Anti-BCMA CAR-NK and UTD NK cells also demonstrated equivalent cytotoxicity towards BCMA non-expressing cell lines, JJN3-Luc BCMA KO and NCI-H520, in an effector:target cancer cell dependent manner, highlighting the potential for treatment with anti-BCMA CAR-NK post-prior BCMA therapy. In in vivo studies, anti-BCMA CAR-NK exhibited robust anti-tumor activity in an MM.1S-Luc4 NSG mouse xenograft model, with no signs of anti-BCMA CAR-NK related body weight loss. Conclusion A cryopreserved allogeneic anti-BCMA CAR-NK cellular therapy exhibits both innate and CAR-mediated killing in vitro and robust in vivo activity in MM tumor models. Preclinical data supports future clinical evaluation in relapsed/refractory MM patients who have received prior BCMA therapy and IND enabling studies are ongoing. Citation Format: LeeAnn Talarico, Christina Wong, Chunyan Pang, Taylor Hickman, Chenqi Hu, Amy Shaw, Emily Wisniewski, Shao-Chiang (Michael) Lai, Pranjal Sharma, Shaun Moore, Luan Nguyen, Kayla Rhuda, Saurin Patel, Paul Lin, Rafet Basar, Shawn Cogan, Kat Sofjan, Arun Ramamurthy, Aaron Handler, Kathryn Fraser, Yana Wang, Katayoun Rezvani, Michael D. Curley. A cryopreserved allogeneic anti-BCMA CAR-NK cellular therapy exhibits both innate and CAR-mediated MM cell killing in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1322.

Abstract Introduction: Chimeric antigen receptor (CAR) T cell (CAR-T) treatments have revolutionized the treatment of multiple myeloma (MM). Two CAR-T cell products targeting B cell maturation antigen (BCMA) have received approval for the treatment of MM: idecabtagene vicleucel (idecel) and ciltacabtagene autoleucel (ciltacel). A comparative analysis of in vivo CAR-T responses in patients receiving these novel cellular therapies has not been performed, especially not in the real-world setting. Methods: We prospectively enrolled 23 MM patients treated with idecel or ciltacel in our study GCCC2043. Blood samples were obtained at apheresis, pre-lymphodepleting (LD) chemotherapy, on days 0, +7, +14, +21, +28 and at +3 months post CAR-T. Samples were stained using BCMA or control CAR detection reagents, monoclonal antibodies against T cell surface antigens, and analyzed using flow cytometry. Results: Baseline clinical characteristics, pre-apheresis and pre-LD absolute lymphocyte counts were comparable between groups. There were no G3 cytokine release syndrome (CRS) events whereas G1/2 CRS and all-grade Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS) events were not significantly different between cohorts. The global overall response rate (ORR) was 78.3% (n=18) and 60.9% (n=14) at days 30 and 90, respectively. At +1 month, 72.7% (8/11) of idecel and 83.3% (10/12) of ciltacel cohort had an objective response (p=0.625). There was no statistical ORR difference between idecel and ciltacel cohorts at 3, 6, and 9 months. Two-way ANOVA of CAR-T expansion studies revealed a trend towards an effect of treatment type (p=0.0595). Time to peak CAR-T numbers was significantly shorter for idecel (p=0.0127), however, ciltacel showed a significantly more pronounced CAR-T expansion (p=0.043) and longer persistence. Peak CAR-T expansion was associated with clinical responses across cohorts at +1 (p=0.034) and +3 months (p=0.050). Day +30 responses were indicative of Day +90 and Day +180 responses (p<0.001, p=0.011). There was no difference in CD8+ CAR T cell peak levels, however, CD4+ CAR T cell peak levels were much higher (p=0.019) for ciltacel vs. idecel. Similarly, there were significantly higher (p=0.002) CD4+/CD8+ double-positive CAR-T peak levels in ciltacel vs. idecel patients. There was no significant difference in the distribution of T cell memory subtypes at peak level. Conclusions: We demonstrate here for the first time significant differences in CAR T cell expansion and persistence patterns following infusion of either idacel or ciltacel. Studies are underway at our institution investigating anti-BCMA CAR T cell responses in more detail and larger numbers of patients. Such studies have the potential to identify predictive/prognostic biomarkers and/or lead to further optimization of myeloma-targeting CAR-T. Citation Format: Mehmet Kocoglu, Aaron P. Rapoport, Etse Gebru, Destiny Omili, Daniel Yamoah, Rediet Mulatu, Jean Yared, Nancy M. Hardy, Michael Kallen, Ashraf Z. Badros, Djordje Atanackovic. In vivo expansion patterns of anti-BCMA CAR T-cell in relapsed/refractory multiple myeloma: Comparative immunomonitoring of idecabtagene vicleucel and ciltacabtagene autoleucel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3616.

Objective:Multiple myeloma (MM) is a bone marrow cancer that profoundly affects plasma cells involved in the immune response. Myeloma cells alter the average production of cells in the bone marrow. Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapy allows genetic modifications of an individual’s T-cells to increase the expression of CARs used to identify and attach BCMA proteins to the malignant cells. Our main objective is to perform a systematic review and meta-analysis to explore the efficacy and safety of anti-BCMA CAR T-cell therapy for MM.Material and Methods:We searched five databases, PubMed, CNKI, EMBASE, Cochrane, Web of Science, and CNKI, for studies published on anti-BCMA,CAR-T-cell treatment for MM. Inclusion criteria involved prospective single-arm studies either single or multi-center, in various MM phases and studies that reported anti-BCMA,CAR-T-cell treatment for MM. We excluded non-English publications and conference papers. All statistical analyses were performed in R software and Review Manager 5.4.1.Results:Thirteen articles were included in the analysis. We found that the overall response survival complete response increase was statistically significant. Similarly, the reduction in cytokine release syndrome grades 3 and 4 and neurotoxicity after follow-up was statistically significant. However, the reduction in minimal residual disease negativity (MRDN) was not statistically significant.Conclusion:Using anti-BCMA CAR T-cell therapy in MM was highly efficacious and safe in lowering the adverse outcomes and improving the survival outcomes, complete response, and overall response.

Allogeneic chimeric antigen receptor (CAR) T cell therapies hold the potential to overcome many of the challenges associated with patient-derived (autologous) CAR T cells. Key considerations in the development of allogeneic CAR T cell therapies include prevention of graft-vs-host disease (GvHD) and suppression of allograft rejection. Here, we describe preclinical data supporting the ongoing first-in-human clinical study, the CaMMouflage trial (NCT05722418), evaluating CB-011 in patients with relapsed/refractory multiple myeloma. CB-011 is a hypoimmunogenic, allogeneic anti-B-cell maturation antigen (BCMA) CAR T cell therapy candidate. CB-011 cells feature 4 genomic alterations and were engineered from healthy donor-derived T cells using a Cas12a CRISPR hybrid RNA-DNA (chRDNA) genome-editing technology platform. To address allograft rejection, CAR T cells were engineered to prevent endogenous HLA class I complex expression and overexpress a single-chain polyprotein complex composed of beta-2 microglobulin (B2M) tethered to HLA-E. In addition, T-cell receptor (TCR) expression was disrupted at the TCR alpha constant locus in combination with the site-specific insertion of a humanized BCMA-specific CAR. CB-011 cells exhibited robust plasmablast cytotoxicity in vitro in a mixed lymphocyte reaction in cell cocultures derived from patients with multiple myeloma. In addition, CB-011 cells demonstrated suppressed recognition by and cytotoxicity from HLA-mismatched T cells. CB-011 cells were protected from natural killer cell-mediated cytotoxicity in vitro and in vivo due to endogenous promoter-driven expression of B2M-HLA-E. Potent antitumor efficacy, when combined with an immune-cloaking armoring strategy to dampen allograft rejection, offers optimized therapeutic potential in multiple myeloma. See related Spotlight by Caimi and Melenhorst, p. 385.

Chimeric antigen receptor (CAR) T-cell therapy for multiple myeloma targeting B-cell maturation antigen (BCMA) induces high overall response rates. However, relapse still occurs and novel strategies for targeting multiple myeloma cells using CAR T-cell therapy are needed. SLAMF7 (also known as CS1) and CD38 on tumor plasma cells represent potential alternative targets for CAR T-cell therapy in multiple myeloma, but their expression on activated T cells and other hematopoietic cells raises concerns about the efficacy and safety of such treatments. Here, we used CRISPR/Cas9 deletion of the CD38 gene in T cells and developed DCAR, a double CAR system targeting CD38 and CS1 through activation and costimulation receptors, respectively. Inactivation of CD38 enhanced the anti-multiple myeloma activity of DCAR T in vitro. Edited DCAR T cells showed strong in vitro and in vivo responses specifically against target cells expressing both CD38 and CS1. Furthermore, we provide evidence that, unlike anti-CD38 CAR T-cell therapy, which elicited a rapid immune reaction against hematopoietic cells in a humanized mouse model, DCAR T cells showed no signs of toxicity. Thus, DCAR T cells could provide a safe and efficient alternative to anti-BCMA CAR T-cell therapy to treat patients with multiple myeloma.

Multiple myeloma (MM) is an incurable hematologic malignancy characterized by the rapid proliferation of malignant plasma cells within the bone marrow. Standard therapies often fail due to patient resistance. The US FDA has approved second-generation chimeric antigen receptor (CAR) T cells targeting B-cell maturation antigen (anti-BCMA-CAR2 T cells) for MM treatment. However, achieving enduring clinical responses remains a challenge in CAR T cell therapy. This study developed third-generation T cells with an anti-BCMA CAR (anti-BCMA-CAR3). The CAR incorporated a fully human scFv specific to BCMA, linked to the CD8 hinge region. The design included the CD28 transmembrane domain, two co-stimulatory domains (CD28 and 4-1BB), and the CD3ζ signaling domain (28BBζ). Lentiviral technology generated these modified T cells, which were compared against anti-BCMA-CAR2 T cells for efficacy against cancer. Anti-BCMA-CAR3 T cells exhibited significantly higher cytotoxic activity against BCMA-expressing cells (KMS-12-PE and NCI-H929) compared to anti-BCMA-CAR2 T cells. At an effector-to-target ratio of 10:1, anti-BCMA-CAR3 T cells induced lysis in 75.5 ± 3.8% of NCI-H929 cells, whereas anti-BCMA-CAR2 T cells achieved 56.7 ± 3.4% (p = 0.0023). Notably, after twelve days of cultivation, anti-BCMA-CAR3 T cells nearly eradicated BCMA-positive cells (4.1 ± 2.1%), while anti-BCMA-CAR2 T cells allowed 36.8 ± 20.1% to survive. This study highlights the superior efficacy of anti-BCMA-CAR3 T cells against both low and high BCMA-expressing MM cells, surpassing anti-BCMA-CAR2 T cells. These findings suggest potential for advancing anti-BCMA-CAR3 T cells in chimeric antigen receptor T (CAR-T) therapy for relapsed/refractory MM.

Rapid anti-myeloma activity by T cells expressing an anti-BCMA CAR with a human heavy-chain-only antigen-binding domain

Multiple myeloma (MM) has witnessed improved patient outcomes through advancements in therapeutic approaches. Notably, allogeneic stem cell transplantation, proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies have contributed to enhanced quality of life. Recently, a promising avenue has emerged with chimeric antigen receptor (CAR) T cells targeting B-cell maturation antigen (BCMA), expressed widely on MM cells. To mitigate risks associated with allogenic T cells, we investigated the potential of BCMA CAR expression in natural killer cells (NKs), known for potent cytotoxicity and minimal side effects. Using the NK-92 cell line, we co-expressed BCMA CAR and soluble tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL) employing the piggyBac transposon system. Engineered NK cells (CAR-NK-92-TRAIL) demonstrated robust cytotoxicity against a panel of MM cell lines and primary patient samples, outperforming unmodified NK-92 cells with a mean difference in viability of 45.1% (±26.1%, depending on the target cell line). Combination therapy was explored with the proteasome inhibitor bortezomib (BZ) and γ-secretase inhibitors (GSIs), leading to a significant synergistic effect in combination with CAR-NK-92-TRAIL cells. This synergy was evident in cytotoxicity assays where a notable decrease in MM cell viability was observed in combinatorial therapy compared to single treatment. In summary, our study demonstrates the therapeutic potential of the CAR-NK-92-TRAIL cells for the treatment of MM. The synergistic impact of combining these engineered NK cells with BZ and GSI supports further development of allogeneic CAR-based products for effective MM therapy.

Increased Bone Turnover and Decreased BCMA Levels in Patients with Response to Anti-BCMA CAR T Cell Therapy in Relapsed/Refractory Multiple Myeloma