Biallelic loss of BCMA as a resistance mechanism to CAR T cell therapy in a patient with multiple myeloma

Comprehensive Review of Bispecific Antibody Constructs In Multiple Myeloma: Affinities, Dosing Strategies and Future Perspectives

Despite significant advancements, multiple myeloma (MM) remains incurable, and there is still a pressing need for new therapeutic strategies with highly selective mechanisms of action and balanced off-target toxicity. In recent years, the development of "off-the-shelf" bispecific antibodies (bsAbs) has significantly enhanced our ability to treat relapsed or refractory MM. Teclistamab, elranatamab (both BCMA × CD3), and talquetamab (GPRC5D × CD3) are approved for treating MM patients who have received at least 3 prior lines of therapy, including a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 monoclonal antibody. Meanwhile, the range of available bsAbs is rapidly expanding, offering patients and healthcare providers a broad selection of options that vary in target antigens, binding domains, construct designs, dosing regimens, and side effects. As linvoseltamab, alnuctamab, and ABBV-383 (all BCMA × CD3), as well as forimtamig (GPRC5D × CD3) and cevostamab (FcRH5 × CD3) progress through late-stage clinical development, emerging trispecific antibodies are now available that target either 2 different MM-associated antigens or provide additional co-stimulatory signals to prevent T-cell exhaustion. Despite this plethora of therapeutic options, resistance to bsAbs is an inevitability, and the optimal positioning of these drugs within the current MM treatment landscape remains to be determined. In this review, we examine the available data on all clinically accessible bsAbs, evaluating their potential, current limitations, and implications for efficacy and safety, with the aim of achieving deeper responses and longer overall survival for MM patients.

Successful sequential application of CAR T-cell-therapies in relapsed refractory multiple myeloma

We here report on a patient with relapsed-refractory multiple myeloma (RRMM) who received chimeric antigen receptor (CAR) T-cells (Ciltacabtagene Autoleucel, cilta-cel, Carvykti®) after achieving a partial but not durable remission with Idecabtagene Vicleucel (ide-cel, Abecma®). Both CAR T-cells target the B-cell maturation antigen (BCMA) and their sequential use is as yet rare, thus data on safety and efficacy of their sequential employment are precious and relevant for the myeloma commmunity.

Perspectives on Talquetamab and its Utility in the Treatment of Multiple Myeloma: Safety, Efficacy and Place in Therapy

Despite recent advancements, most patients with multiple myeloma eventually develop resistance to available treatments, highlighting the need for new therapeutic strategies. G protein-coupled receptor class C group 5 member D (GPRC5D) has emerged as a viable novel therapeutic target on myeloma cells, leading to the clinical development of talquetamab, the first GPRC5D-directed bispecific T-cell engager (TCE). Talquetamab was granted accelerated approval in August 2023 by the Food and Drug Administration. Besides expected short-term toxicities including cytokine release syndrome, neurotoxicity and cytopenias, talquetamab commonly causes adverse events involving the oral cavity, nails, and skin, which can negatively impact quality of life and in some cases lead to treatment discontinuation. Despite these pitfalls, talquetamab yields responses in most treated patients, which in a subset are durable. There are now several clinical trials investigating talquetamab in different clinical contexts in multiple myeloma, as well as in combination with other anti-myeloma agents. Beyond results from these prospective trials, better biologic understanding of resistance mechanisms to talquetamab and improved strategies to mitigate common toxicities are key questions as talquetamab finds its place in the treatment of multiple myeloma.

CAR-mediated target recognition limits TCR-mediated target recognition of TCR- and CAR-dual-receptor-edited T cells

Antigen escape can compromise the efficacy of chimeric antigen receptor- (CAR-) or T cell receptor- (TCR-) engineered T cells. Targeting multiple antigens can effectively limit antigen escape, and combining CAR-with TCR-mediated targeting can significantly broaden the spectrum of targetable antigens. Here, we explored whether dual-antigen specificity can be installed on T cells using combined TCR and CAR engineering to prevent antigen escape of multiple myeloma (MM). We report the generation of CD8 T cells that were transduced to express a transgenic TCR, targeting a peptide derived from transcriptional coactivator BOB1 in the context of HLA-B∗07:02, alongside a BCMA-targeting CAR. Those T cells, called TRaCR T cells, efficiently recognized target cells that were resistant to either BOB1 TCR or BCMA CAR T cells, illustrating general dual specificity. In the presence of both antigens, however, target cell recognition was preferentially conferred via the CAR, compromising TCR-mediated target cell recognition. Importantly, this resulted in a survival advantage for tumor cells lacking expression of BCMA in an in vivo model of heterogeneous MM. In conclusion, we demonstrate general dual specificity of TRaCR T cells but advise caution when using TRaCR T cells as a strategy to target heterogeneous tumors.

Mechanisms of resistance to CAR-T cell therapy in multiple myeloma: latest updates from the 2024 ASH annual meeting

Chimeric Antigen Receptor T-Cell (CAR-T) therapy demonstrates significant potential in the treatment of multiple myeloma (MM). However, resistance to CAR-T therapy remains a critical challenge. Investigating the mechanisms underlying CAR-T resistance, including antigen escape, immunosuppression, and CAR-T cell exhaustion, is essential for enhancing the long-term efficacy of this therapeutic approach. This study provides an in-depth review of the latest findings presented at the 66th ASH Annual Meeting.

Progress of immune senescence in multiple myeloma treatment resistance

Multiple myeloma has become the second most common hematologic malignancy threatening human health with the increasing incidence in the population, and the emergence of drug resistance in its treatment has become a problem that needs to be solved urgently. Recent studies have shown that the immune system is closely related to the development of multiple myeloma, and immune senescence plays an extremely critical role in MM treatment resistance. In this paper, we review the connection between immune senescence and the development of MM and its possible role in the drug resistance of MM treatment, to provide new research ideas for the in-depth study of the mechanism of immune senescence and the search for new immunotherapeutic targets to overcome the phenomenon of drug resistance in the immunotherapy of MM patients.

Design of sensitive monospecific and bispecific synthetic chimeric T cell receptors for cancer therapy

The adoptive transfer of T cells expressing chimeric antigen receptors (CARs) is effective in B cell malignancies. However, the persistence of cancer cells with low levels or complete absence of the target antigen, thereby evading detection by CAR T cells, leads to relapse. These evasion mechanisms highlight the need for receptors with enhanced sensitivity and multispecificity. We introduce a synthetic chimeric T cell receptor (ChTCR) that confers superior antigen sensitivity compared with CARS and previous hybrid TCR designs and is readily adapted for bispecific targeting. ChTCRs replicate the structure of natural TCRs, form classical immune synapses and demonstrate TCR-like signaling. T cells expressing bispecific ChTCRs (Bi-ChTCRs) are more effective than bispecific CAR T cells in eradicating tumors with heterogeneous antigen expression in vivo in female mice. The Bi-ChTCR architecture is resilient and can be designed to target pairs of B cell and multiple myeloma antigens. These findings provide a widely applicable strategy to combat tumor heterogeneity and prevent relapse.

Multi-Targeting CAR-T Cell Strategies to Overcome Immune Evasion in Lymphoid and Myeloid Malignancies

BACKGROUND

Chimeric antigen receptor (CAR)-T cell therapy has become a groundbreaking treatment for hematological malignancies, particularly lymphomas and multiple myeloma, with high remission rates in refractory and relapsed patients. However, most CAR-T therapies target a single antigen, such as CD19, which can result in immune evasion through antigen escape. This mechanism describes the downregulation or complete loss of the targeted antigen by the tumor cells, eventually leading to relapse. To address this issue, multi-targeting strategies like logic-gated CARs, adapter CARs, or combination therapies can increase the potency of CAR-T cells. These approaches aim to minimize immune evasion by targeting multiple antigens simultaneously, thereby increasing treatment durability. Additionally, advanced tools such as next-generation sequencing (NGS), direct stochastic optical reconstruction microscopy (dSTORM), or multiparametric flow cytometry are helping to identify novel tumor-specific targets and improve therapy designs.

SUMMARY

This review explores the current landscape of CAR-T cell therapies in lymphoid and myeloid malignancies, highlights ongoing clinical trials, and discusses the future of these innovative multi-targeting approaches to improve patient outcome.

KEY MESSAGES

Antigen escape limits CAR-T cell therapy success, but multi-targeting strategies like logic gates and adapter CARs offer solutions. Optimizing antigen selection and CAR design, along with larger clinical trials, is essential for improving patient outcomes. Personalization using advanced technologies like CRISPR screening and single-cell RNA sequencing can enhance durability and effectiveness of treatments for heavily pretreated patients.

Myeloma cell-intrinsic ANXA1 elevation and T cell dysfunction contribute to BCMA-negative relapse after CAR-T therapy

Multiple myeloma (MM) relapse still occurs after a durable response to anti-B cell maturation antigen (BCMA) chimeric antigen receptor-engineered T (CAR-T) cell therapy with less-defined factors. Herein, we investigated a CAR-T-exposed MM patient who relapsed after 12 months of remission by single-cell transcriptome sequencing. The bone marrow CAR-T population at relapse exhibited exhaustion and proliferation attenuation. The recurrent myeloma cells were deficient in or weakly expressed TNFRSF17 (BCMA) but possessed an identical immunoglobulin clonality to the baseline tumor. Interestingly, combined with the transcriptome profile of the myeloma strains, MM cells with BCMA negativity featured high ANXA1 expression that was identified as an inferior prognostic indicator for MM patients. At a single-cell resolution, BCMA-negative myeloma could be present in the MM patients without CAR-T cell exposure and displayed an increased level of intrinsic ANXA1 transcripts. In vitro assays unveiled that Annexin A1 (ANXA1) elevation conferred growth capacity to BCMA-negative myeloma cells via AMPKα signaling activation and disturbed CAR-T cell fitness. Blockade of Annexin A1 reduced BCMA-negative myeloma cell proliferation. Murine models further demonstrated that Annexin A1 inhibition could effectively diminish BCMA-negative myeloma that escaped from CAR-T's attack. Together, our data identified ANXA1 as a potential target for BCMA-negative myeloma clearance. The ANXA1-targeting strategy might be helpful for CAR-T treatment optimization.

Mechanisms for resistance to BCMA-targeted immunotherapies in multiple myeloma

Multiple myeloma (MM) remains incurable and patients eventually face the relapse/refractory dilemma. B cell maturation antigen (BCMA)-targeted immunotherapeutic approaches have shown great effectiveness in patients with relapsed/refractory MM, mainly including chimeric antigen receptor T cells (CAR-T), bispecific T cell engagers (TCEs), and antibody-drug conjugates (ADCs). However, their impact on long-term survival remains to be determined. Nonetheless, resistance to these novel therapies is still inevitable, raising a challenge that we have never met in both laboratory research and clinical practice. In this scenario, the investigation aiming to enhance and prolong the anti-MM activity of BCMA-targeted therapies has been expanding rapidly. Despite considerable uncertainty in our understanding of the mechanisms for their resistance, they have mainly been attributed to antigen-dependency, T cell-driven factors, and (immune) tumor microenvironment. In this review, we summarize the current understanding of the mechanisms for resistance to BCMA-targeted immunotherapies and discuss potential strategies for overcoming it.

Deciphering response dynamics and treatment resistance from circulating tumor DNA after CAR T-cells in multiple myeloma

Despite advances in treatments, multiple myeloma (MM) remains an incurable cancer where relapse is common. We developed a circulating tumor DNA (ctDNA) approach in order to characterize tumor genomics, monitor treatment response, and detect early relapse in MM. By sequencing 412 specimens from 64 patients with newly diagnosed or relapsed/refractory disease, we demonstrate the correlation between ctDNA and key clinical biomarkers, as well as patient outcomes. We further extend our approach to simultaneously track CAR-specific cell-free DNA (CAR-cfDNA) in patients undergoing anti-BCMA CAR T-cell (BCMA-CAR) therapy. We demonstrate that ctDNA levels following BCMA-CAR inversely correlate with relative time to progression (TTP), and that measurable residual disease (MRD) quantified by peripheral blood ctDNA (ctDNA-MRD) was concordant with clinical bone marrow MRD. Finally, we show that ctDNA-MRD can anticipate clinical relapse and identify the emergence of genomically-defined therapy-resistant clones. These findings suggest multiple clinical uses of ctDNA for MM in molecular characterization and disease surveillance.

Strategies to Overcome Antigen Heterogeneity in CAR-T Cell Therapy

Chimeric antigen receptor (CAR) gene-modified T-cell therapy has achieved significant success in the treatment of hematological malignancies. However, this therapy has not yet made breakthroughs in the treatment of solid tumors and still faces issues of resistance and relapse in hematological cancers. A major reason for these problems is the antigenic heterogeneity of tumor tissues. This review outlines the antigenic heterogeneity encountered in CAR-T cell therapy and the corresponding strategies to address it. These strategies include using combination therapy to increase the abundance of target antigens, optimizing the structure of CARs to enhance sensitivity to low-density antigens, developing multi-targeted CAR-T cells, and reprogramming the TME to activate endogenous immunity. These approaches offer new directions for overcoming tumor antigenic heterogeneity in CAR-T cell therapy.

Genetic disruption of Blimp-1 drastically augments the antitumor efficacy of BCMA-targeting CAR T cells

ABSTRACT

Chimeric antigen receptor (CAR) T cells directed against B-cell maturation antigen (BCMA) are an effective treatment for multiple myeloma (MM), but short persistence and frequent relapses are challenges for this immunotherapy. This lack of durability has been attributed to the premature terminal differentiation of CAR T cells, which prevents the formation of long-lived memory cells that maintain antitumor responses. To improve long-term efficacy, we used CRISPR/CRISPR-associated protein 9-mediated gene editing to ablate the expression of the transcription factor Blimp-1. Blimp-1 knockout (KO) CAR T cells displayed a memory-like phenotype compared with control (Mock) CAR T cells, but had reduced effector function, with a striking loss of granzyme B. However, in a murine model of advanced MM, Blimp-1 KO CAR T cells effectively slowed or even prevented disease progression, significantly outperforming Mock CAR T cells in improving survival (P = .006). To understand this enhanced in vivo effectiveness, Blimp-1 KO CAR T cells were characterized after being repeatedly challenged with tumor cells in vitro. In this setting, Blimp-1 KO CAR T cells maintained a highly active state with high expression of memory markers, but, crucially, demonstrated enhanced effector function and increased energetic capacity. RNA-sequencing analysis of tumor-exposed Blimp-1 KO CAR T cells confirmed the presence of a memory-like transcriptomic signature and, additionally, revealed enhanced ribosome biogenesis and repressed CAR T-cell dysfunction as mechanisms that could contribute to improved antitumor activity. Put together, our findings show that dampening Blimp-1 expression altered the phenotype and function of anti-BCMA CAR T cells, leading to augmented therapeutic efficacy in MM.

Phase I Trial of MCARH109, a G Protein-Coupled Receptor Class C Group 5 Member D (GPRC5D)-Targeted Chimeric Antigen Receptor T-Cell Therapy for Multiple Myeloma: An Updated Analysis

MCARH109 is a first-in-class G protein-coupled receptor, class C, group 5, member D (GPRC5D)-targeted chimeric antigen receptor (CAR) T-cell therapy for patients with relapsed/refractory multiple myeloma. This phase I clinical trial included 17 patients and determined that MCARH109 is safe at a maximum tolerated dose of 150 × 106 CAR T cells. In this updated analysis, no new serious adverse events were reported at a median follow-up of 37 months. Overall, 12 (71%) of 17 patients responded, including seven (70%) of 10 patients previously treated with B-cell maturation antigen-targeted therapy. The median duration of response was 8.6 months (95% CI, 5.7 to not reached [NR]) with two patients sustaining a stringent complete response at the time of last follow-up, 32 months and 41 months, respectively. The median overall survival (OS) was NR and the 3-year OS estimate was 59% (95% CI, 40 to 88). Possible GPRC5D loss via immunohistochemistry was observed in 6 (60%) of 10 patients at relapse. High-dimensional spectral cytometry-based immune profiling associated an activated T-cell phenotype at apheresis with a response to MCARH109.

CAR-T cell therapy in the treatment of relapsed or refractory primary central nervous system lymphoma: recent advances and challenges

Primary central nervous system lymphoma (PCNSL) is a rare and aggressive lymphoma that is isolated in the central nervous system (CNS) or vitreoretinal space. High-dose methotrexate (HD-MTX)-based immunochemotherapy is the frontline for its treatment, with a high early response rate. However, relapsed or refractory (R/R) patients present numerous difficulties and challenges in clinical treatment. Chimeric antigen receptor (CAR)-T cells offer a promising option for the treatment of hematologic malignancies, especially in the R/R B-cell lymphoma and multiple myeloma. Despite the exclusion of most PCNSL cases from pivotal CAR-T cell trials due to their specific tumor microenvironment (TME), available preclinical and clinical studies with small cohorts suggest an overall acceptable safety profile and remarkable anti-tumor effects. In this review, we will provide the development process of CAR-T cells and summarize the research progress, limitations, and future perspectives of CAR-T cell therapy in patients with R/R PCNSL.

Targeting BCMA in multiple myeloma: designs, challenges, and future directions

Chimeric antigen receptor (CAR) T cell therapy has emerged as a groundbreaking immunotherapy, demonstrating significant efficacy in treating B cell malignancies. In the context of multiple myeloma (MM), B cell maturation antigen (BCMA) has been identified as a critical target, driving the development of CAR T cell therapies designed to address this plasma cell cancer. Various CAR designs, utilizing different BCMA recognition domains, have yielded promising clinical results, leading to the approval of two BCMA-targeting CAR T cell therapies by the US Food and Drug Administration (FDA) for the treatment of MM. This review uniquely examines the BCMA CAR T cell landscape, emphasizing the design of recognition domains, clinical efficacy, and patient outcomes. It critically addresses emerging challenges such as antigen escape and toxicity profiles, which have surfaced alongside therapeutic advances. Moreover, the review spotlights cutting-edge developments, including dual-targeting CAR T strategies, advancements in CAR T cell manufacturing, and innovative allogeneic CAR T approaches utilizing healthy donor cells. By detailing both the breakthroughs and ongoing challenges in BCMA CAR T cell therapy, this review offers a comprehensive perspective on the current state and future possibilities of CAR T cell therapy for MM and its expanding role in treating hematologic malignancies and beyond.

Targets Selection for Precision Therapy of Relapsed/Refractory Multiple Myeloma: the Latest Advancements

OPINION STATEMENT

According to the guidelines, the primary treatment for multiple myeloma is still based on drugs such as carfilzomib, lenalidomide, or daratumumab. However, patients with relapsed/refractory multiple myeloma (RRMM) may be insensitive or develop resistance to the above therapeutic medications. Thus, formulating standardized and rational treatment regimens for such patients remains an area for consideration. Multidrug combinations are available for the therapy of patients with relapsed/refractory multiple myeloma to improve their clinical outcome and prevent the occurrence of multidrug resistance. For instance, combination therapy with immunomodulators, proteasome inhibitors, and CD38 monoclonal antibodies. With the development of genomics and molecular diagnostic technologies, RRMM has entered the era of precision therapy. Targeted immunotherapeutic drugs such as monoclonal antibodies, bispecific antibodies, antibody-drug conjugates (ADCs), and chimeric antigen receptor-T (CAR-T) cells have shown promising clinical response rates and favorable safety profiles in several clinical and experimental studies. These cutting-edge medicinal treatments may provide new hope for a cure for RRMM. However, the choice of treatment regimen still needs to adhere to the principle of individualization. Generally, we recommend treatment with drugs of a new generation or novel mechanism of action for patients with RRMM who are first relapsed, such as next-generation proteasome inhibitors, next-generation immunomodulators, and CD38-based monoclonal antibody regimens. For multiple relapsed RRMM, we recommend choosing a combination regimen or participating in relevant clinical trials. Additionally, monoclonal antibodies have become the standard of care for patients with RRMM. With the introduction of CAR-T therapy, ADCs, and bispecific antibodies, RRMM patients are expected to achieve deep remissions and long-term survival again.

Exploring CAR-PBMCs: A Novel Strategy Against EGFR-Positive Tumor Cells

Background: Chimeric antigen receptor (CAR) T cell therapy has shown significant promise in treating hematological malignancies, yet its application in solid tumors, particularly those expressing the epidermal growth factor receptor (EGFR), remains limited. This study investigates the potential of CAR-engineered peripheral blood mononuclear cells (PBMCs) as a novel adoptive cell therapy against EGFR-positive cancers. Methods: Lentiviral transduction at an MOI of 50 was performed to generate specific anti-EGFR second generation CAR-effector cells. The transduced PBMCs were stimulated with cytokines and CD3/CD28 beads to enhance their proliferation and activation. Flow cytometric and real-time cell analysis were performed at various effector-to-target ratios to explore the cytotoxic potential of CAR-PBMCs. Results: CAR-PBMCs exhibited improved targeting and cytotoxicity against EGFR-positive cancer cell lines MDA-MB-468 and SK-BR-3, compared to untransduced controls, with unsignificant effects on allogeneic PBMCs. Conclusion: CAR-PBMCs hold considerable potential as a therapeutic strategy for EGFR-positive solid tumors, warranting further clinical investigation.

Engineered T cells secreting αB7-H3-αCD3 bispecific engagers for enhanced anti-tumor activity against B7-H3 positive multiple myeloma: a novel therapeutic approach

BACKGROUND

Multiple myeloma (MM) is an incurable plasma cell malignancy with increasing global incidence. Chimeric antigen receptor (CAR) T-cell therapy targeting BCMA has shown efficacy in relapsed or refractory MM, but it faces resistance due to antigen loss and the tumor microenvironment. Bispecific T-cell engaging (BITE) antibodies also encounter clinical challenges, including short half-lives requiring continuous infusion and potential toxicities.

METHODS

To address these issues, we developed a lentiviral system to engineer T cells that secrete αB7-H3-αCD3 bispecific engager molecules (αB7-H3-αCD3 ENG-T cells). We evaluated their effectiveness against MM cells with varying B7-H3 expression levels, from B7-H3neg to B7-H3high.

RESULTS

The αB7-H3-αCD3 ENG-T cells demonstrated significant anti-tumor activity against MM cell lines expressing B7-H3. SupT-1 cells (B7-H3neg) served as controls and exhibited minimal cytotoxicity from αB7-H3-αCD3 ENG T cells. In contrast, these engineered T cells showed dose-dependent killing of B7-H3-expressing MM cells: NCI-H929 (B7-H3low), L-363 (B7-H3medium), and KMS-12-PE (B7-H3high). For NCI-H929 cells, cytotoxicity reached 38.5 ± 7.4% (p = 0.0212) and 54.0 ± 9.2% (p = 0.0317) at effector-to-target (E:T) ratios of 5:1 and 10:1, respectively. Against L-363 cells, cytotoxicity was 56.6 ± 3.2% (p < 0.0001) and 71.4 ± 5.2% (p = 0.0002) at E:T ratios of 5:1 and 10:1, respectively. For KMS-12-PE cells, significant cytotoxic effects were observed even at an E:T ratio of 1:1, with 27.2 ± 3.7% (p = 0.0004), 44.4 ± 3.7% (p < 0.0001), and 68.6 ± 9.2% (p = 0.0004) cytotoxicity at E:T ratios of 1:1, 5:1, and 10:1, respectively.

CONCLUSIONS

These results indicate that αB7-H3-αCD3 ENG T cells could be a promising therapy for B7-H3-positive MM. They may enhance current MM treatments and improve overall outcomes. Additional preclinical and clinical research is required to fully assess their therapeutic potential.

Single-cell analysis of the multiple myeloma microenvironment after γ-secretase inhibition and CAR T-cell therapy

ABSTRACT

Chimeric antigen receptor (CAR) T cells and bispecific antibodies targeting B-cell maturation antigen (BCMA) have significantly advanced the treatment of relapsed and refractory multiple myeloma. Resistance to BCMA-targeting therapies, nonetheless, remains a significant challenge. BCMA shedding by γ-secretase is a known resistance mechanism, and preclinical studies suggest that inhibition may improve anti-BCMA therapy. Leveraging a phase 1 clinical trial of the γ-secretase inhibitor (GSI), crenigacestat, with anti-BCMA CAR T cells (FCARH143), we used single-nuclei RNA sequencing and assay for transposase-accessible chromatin sequencing to characterize the effects of GSI on the tumor microenvironment. The most significant impacts of GSI involved effects on monocytes, which are known to promote tumor growth. In addition to observing a reduction in the frequency of nonclassical monocytes, we also detected significant changes in gene expression, chromatin accessibility, and inferred cell-cell interactions after exposure to GSI. Although many genes with altered expression are associated with γ-secretase-dependent signaling, such as Notch, other pathways were affected, indicating GSI has far-reaching effects. Finally, we detected monoallelic deletion of the BCMA locus in some patients with prior exposure to anti-BCMA therapy, which significantly correlated with reduced progression-free survival (PFS; median PFS, 57 vs 861 days). GSIs are being explored in combination with the full spectrum of BCMA-targeting agents, and our results reveal widespread effects of GSI on both tumor and immune cell populations, providing insight into mechanisms for enhancing BCMA-directed therapies.

Forimtamig, a novel GPRC5D-targeting T-cell bispecific antibody with a 2+1 format, for the treatment of multiple myeloma

ABSTRACT

Despite several approved therapies, multiple myeloma (MM) remains an incurable disease with high unmet medical need. "Off-the-shelf" T-cell bispecific antibodies (TCBs) targeting B-cell maturation antigen (BCMA) and G protein-coupled receptor class C group 5 member D (GPRC5D) have demonstrated high objective response rates in heavily pretreated patients with MM; however, primary resistance, short duration of response, and relapse driven by antigen shift frequently occur. Although GPRC5D represents the most selective target in MM, recent findings indicate antigen loss occurs more frequently than with BCMA. Thus, anti-GPRC5D immunotherapies must hit hard during a short period of time. Here, we characterize forimtamig, a novel GPRC5D-targeting TCB with 2+1 format. Bivalent binding of forimtamig to GPRC5D confers higher affinity than classical 1+1 TCB formats correlating with formation of more stable immunological synapses and higher potency in tumor cell killing and T-cell activation. Using an orthotopic mouse model of MM, forimtamig recruited T effector cells to the bone marrow and induced rapid tumor killing even after the introduction of step-up dosing to mitigate cytokine release. Combination of forimtamig with standard-of-care agents including anti-CD38 antibodies, immunomodulatory drugs, and proteasome inhibitors improved depth and duration of response. The combination of forimtamig with novel therapeutic agents including BCMA TCB and cereblon E3 ligase modulatory drugs was potent and prevented occurrence of GPRC5D -negative tumor relapse. Forimtamig is currently being evaluated in phase 1 clinical trials in patients with relapsed and refractory MM for monotherapy and in combination treatments. This trial was registered at www.ClinicalTrials.gov as #NCT04557150.

A systematic literature review on clonal evolution events preceding relapse in multiple myeloma

Despite considerable treatment advances, multiple myeloma (MM) remains an incurable hematological cancer due to treatment resistance. A systematic literature search was conducted to identify determinants for clonal evolution driving relapse and drug resistance in MM. A total of 631 non-duplicate publications were screened of which 28 articles were included for data extraction. Genetic alterations, mutational signatures, evolutionary trajectories, and non-genetic determinants were identified as key topics to characterize clonal evolution in relapsed MM. A variety of factors led to clonal diversification and increased tumor mutation burden, such as MAPK-Ras mutations and incremental changes related to chromosomal bands 1 and 17, while mutational signature analyses revealed that APOBEC activity and melphalan treatment leave a distinct impact on the clonal composition in MM genomes. To capture and dissect tumor heterogeneity, our review suggests combining methods or using technical approaches with high resolution to assess the impact of clonal evolution.

Idecabtagene vicleucel (ide-cel) for the treatment of triple-class exposed relapsed and refractory multiple myeloma

INTRODUCTION

Modern anti-myeloma therapies have broken new ground in the treatment of the disease, and the incorporation of ide-cel in the treatment landscape represents one of the major scientific and clinical advances.

AREAS COVERED

Ide-cel was the first cell-based gene therapy approved for the treatment of triple-class exposed relapsed/refractory myeloma patients, showing impressive results, and demonstrating superiority over standard regimens in terms of efficacy, potential treatment-free intervals, and improved quality of life in heavily pretreated patients and in high-risk disease. This review summarizes the state-of-the-art of the most recent updates deriving from the use of ide-cel within ongoing, or upcoming, clinical trials, and from real-life experiences.

EXPERT OPINION

As the use of chimeric antigen receptor (CAR)-T therapy is likely to progressively increase over time and current indications expand to earlier treatment lines, efforts should be directed toward ameliorating overall management to facilitate proactive planning for treatment sequencing and provide adequate time for logistical planning. Importantly, the potential limited availability of CAR-T therapy highlights the importance of careful patient selection and coordination among centers. Meanwhile, attempts are underway to improve tolerance and reduce toxicity while enhancing anti-myeloma activity.

Optimized BCMA/CS1 bispecific TRuC-T cells secreting IL-7 and CCL21 robustly control multiple myeloma

Introduction

Challenges remain in reducing antigen escape and tumor recurrence while CAR-T cell therapy has substantially improved outcomes in the treatment of multiple myeloma. T cell receptor fusion construct (TRuC)-T cells, which utilize intact T cell receptor (TCR)-CD3 complex to eliminate tumor cells in a non-major histocompatibility complex (MHC)-restricted manner, represent a promising strategy. Moreover, interleukin-7 (IL-7) is known to enhance the proliferation and survival of T cells. C-C motif chemokine ligand 21 (CCL21) is a ligand for chemokine C-C motif receptor 7 (CCR7) and exhibits strong chemotaxis against naïve T cells and antigen-presenting cells such as dendritic cells.

Methods

The bispecific TRuC-T cells simultaneously targeting B cell maturation antigen (BCMA) and CD2 subset 1 (CS1) were constructed by pairing two of five subunits (i.e., TCRαC, TCRβC, CD3γ, CD3δ, and CD3ϵ) in the TCR/CD3 complex and were named C-AC-B-3E, C-BC-B-3E, C-3G-B-3E, C-3D-B-3E, C-3E-B-3E, B-3E-C-3E, B-3G-C-3E, and B-3D-C-3E. Additionally, the BCMA/CS1 bispecific TRuC-T cells secreting IL-7 and CCL21, named BC-7×21 TRuC-T cells, were generated. All of the bispecific TRuC-T cells were characterized and tested in vitro and in vivo.

Results

Following the optimization of various pairs of two subunits of TCR/CD3 complex, B-3G-C-3E TRuC-T cells, characterized by incorporating CD3γ and CD3ε, exhibited the strongest myeloma-specific cytotoxicity. Furthermore, the bispecific BC-7×21 TRuC-T cells had stronger proliferation, chemotaxis, and cytotoxicity in vitro. Accordingly, the bispecific BC-7×21 TRuC-T cells showed better persistence in vivo so as to effectively suppress tumor growth in the NCG mouse xenograft model of MM.1S multiple myeloma.

Discussion

This study demonstrated that BC-7×21 TRuC-T cells, engineered through the optimization of the two subunits of TCR/CD3 complex and a co-expression cytokine strategy, may offer a novel and effective therapy for relapsed/refractory multiple myeloma.

Impact of soluble BCMA and non-T-cell factors on refractoriness to BCMA-targeting T-cell engagers in multiple myeloma

ABSTRACT

Adoptive T-cell therapy is a promising therapy for multiple myeloma (MM), but its efficacy hinges on understanding the relevant biologic and predictive markers of response. B-cell maturation antigen (BCMA) is a key target antigen in MM with active development of multiple anti-BCMA T-cell engagers (TCEs) and chimeric antigen receptor T-cell therapies. The regulation of surface BCMA expression by MM cells, which leads to shedding of soluble BCMA (sBCMA), has triggered debate about the significance of sBCMA as a predictive marker and its potential impact on treatment outcomes. To address this, we leveraged whole-genome sequencing and in vitro assays to demonstrate that sBCMA may independently predict primary refractoriness to anti-BCMA therapies. In addition to sBCMA, tumor burden and surface BCMA antigen density collectively influenced the anti-BCMA TCE cytotoxic efficacy. Correlative analyses of 163 patients treated with the anti-BCMA TCE teclistamab validated and further underscored the association between elevated baseline sBCMA (>400 ng/mL) and refractoriness. Importantly, increasing the TCE dose, using TCE against alternative targets (eg, GPRC5D), and gamma secretase inhibitors were able to overcome the high sBCMA levels. These findings highlight the importance of taking into account the baseline sBCMA levels, disease burden, and TCE dose intensity when administering anti-BCMA TCEs, thereby offering critical insights for optimizing therapeutic strategies to overcome specific high-risk features and primary anti-BCMA TCE refractoriness.

Bispecific antibody and chimeric antigen receptor (CAR) modified T-cell in the treatment of multiple myeloma: Where do we stand today?

Although the prognosis of patients with multiple myeloma (MM) has been significantly improved by the introduction of proteasome inhibitors, immunomodulatory drugs and monoclonal antibodies, MM is still considered an incurable disease in the vast majority of the patients. In recent years, T-cell based immunotherapy represents a novel treatment strategy for relapsed/refractory (RR) MM. So far, chimeric antigen receptor (CAR) modified T-cells and bispecific T-cell engaging antibodies (bsAb) have shown promising anti-MM efficacy and manageable safety profile within clinical trials, and B-cell maturation antigen (BCMA) is the most commonly used immune target for T-cell based immunotherapies in MM. To date, several CAR T-cell and bsAb products have already been approved for the treatment of RRMM, leading to a paradigm shift in the MM therapy and providing a potential curative option. In this review, we provide a summary of mechanisms of action, immune targets, selected clinical data, resistance mechanisms and therapy sequencing of CAR T-cell and bsAb in MM.

Bispecific antibodies targeting BCMA or GPRC5D are highly effective in relapsed myeloma after CAR T-cell therapy

Despite the astonishing outcomes after chimeric antigen receptor (CAR) T-cell therapy for relapsed refractory multiple myeloma (RRMM), most patients eventually relapse. There are only limited data available on salvage therapies following relapse after BCMA-directed CAR T-cell therapy. Here, we analyzed outcomes of post-CAR T-cell therapy relapse and impact of different salvage strategies in an international cohort of 139 patients (n = 130 ide-cel, n = 9 cilta-cel), receiving talquetamab (n = 28), teclistamab (n = 37), combinations of immunomodulating drugs (IMiDs), proteasome inhibitors (PIs) or CD38 monoclonal antibodies (n = 43), and others (n = 31). The median time to relapse after CAR T-cell therapy was 5 months, 53% had the extramedullary disease (EMD) at relapse, associated with dismal post-relapse outcome (P = 0.005). Overall response and complete response upon salvage therapies were 79% and 39% for talquetamab, 64% and 32% for teclistamab, 30% and 0% for IMiDs/PIs/CD38, and 26% and 3% for others (P < 0.001). Duration of response, as well as median survival, was significantly improved with bispecific antibodies (P < 0.001, respectively). Bispecific antibodies seemed to overcome the poor prognosis associated with early relapse and EMD, and were independent predictors for improved survival in multivariable analysis. In summary, these results suggest bispecific antibodies as the standard of care for relapse after CAR T-cell therapy for RRMM.

Kinetics of Nirogacestat-Mediated Increases in B-cell Maturation Antigen on Plasma Cells Inform Therapeutic Combinations in Multiple Myeloma

SIGNIFICANCE

GSIs can enhance multiple myeloma therapies targeting BCMA by increasing mbBCMA on plasma cells. In response to the GSI nirogacestat, mbBCMA rapidly and robustly increased in vitro and in vivo. Elucidating nirogacestat's effects on BCMA kinetics will guide potential multiple myeloma dosing strategies.

Are we there yet? CAR-T therapy in multiple myeloma

The last few years have seen a revolution in cellular immunotherapies for multiple myeloma (MM) with novel antigen targets. The principle new target is B-cell maturation antigen (BCMA). Autologous chimeric antigen receptor T-cell (CAR-T) therapy directed against BCMA was first approved by the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) in 2021, although approval by the National Institute for Health and Care Excellent (NICE) is awaited. Initial response rates in patients with heavily pretreated MM have been impressive, but patients are still relapsing. Furthermore, CAR-T manufacturing is expensive and time-consuming, and T-cell fitness is impaired by prior MM treatment. Numerous strategies to improve outcomes and delivery of cellular immunotherapy are under investigation, including next-generation CARs, allogeneic 'off-the-shelf' CARs and targeting of other MM antigens including G protein-coupled receptor, class C, group 5, member D (GPRC5D), Fc receptor homologue 5 (FcRH5), cluster of differentiation (CD)19, signalling lymphocyte activation molecule family member 7 (SLAMF7) and several others. In this exciting and rapidly evolving treatment landscape, this review evaluates the most recent clinical and preclinical data pertaining to these new cellular immunotherapies and explores strategies to overcome resistance pathways. On the protracted journey to a long-term cure, we outline the challenges that lie ahead and ask, 'Are we there yet?'

Complete loss of lineage defining antigens in two cases of B-cell malignancies following CAR-T therapy

Targeted immunotherapy is a promising approach in treating high-risk and refractory/relapsed lymphoid malignancies. Although this strategy has shown a significant success in treating non-Hodgkin B-cell lymphomas and plasma cell myeloma, relapse with loss of targeted antigen can occur. Rarely, complete loss of multiple lineage specific markers can happen. We are describing 2 cases of B-cell neoplasms along with contributing immunohistochemistry, cytogenetic, and molecular results. Post-targeted CAR-T therapy, both cases, one aggressive B-cell lymphoma and the other plasma cell myeloma, lost B-cell, and plasma cell antigens, respectively. Complete loss of lineage specific markers post-targeted therapy is a rare event that makes the diagnosis of the relapsed neoplasm challenging. In this article, we also reviewed the literature and highlighted possible mechanisms of antigen loss following targeted therapy.

Efficacy and safety of teclistamab in relapsed or refractory multiple myeloma: a systematic review and meta-analysis

To synthesize the evidence on the efficacy and safety of teclistamab in treating relapsed/refractory multiple myeloma (RRMM). A systematic search for records published from inception until June 2024 was conducted on PubMed, Web of Science, EMBASE, and Google Scholar databases. Five studies with 661 RRMM patients were included in the analysis. The pooled results showed that teclistamab led to an overall response rate (ORR) of 62.8% (95% Confidence Interval (CI): 58.6-66.8), a ≥ very good partial response or better (VGPR) of 52.1% (95% CI: 46.8-57.3), and a ≥ complete response or better (CR) of 29.5% (95% CI: 21.9-38.4). When the ORR was assessed in different subgroups, we found that patients with extramedullary disease (EMD) had considerably lower ORR than those without EMD (45% vs. 71%, p < 0.0001). The ORR was significantly lower in patients with prior (B-cell maturation antigen) BCMA-directed therapy (OR: 2.24, p = 0.002) and those with stage III disease (OR: 3.69, p = 0.0001). However, the subgroup analyses showed no considerable difference in the ORR between patients with high or standard-risk cytogenetics (OR: 1.05 p = 0.82) and those with penta-drug or triple-class-refractory disease (OR: 0.97 p = 0.89). Regarding the safety of teclistamab, the pooled results showed that the incidence of grade ≥ 3 adverse events was high (90.7%). However, grade ≥ 3 cytokine release syndrome (CRS) and neurotoxic events were low (1.5% and 2.2%, respectively). RRMM patients treated with teclistamab display good response rates.

CAR-T cell therapy in Multiple Myeloma: current status and future challenges

The treatment of multiple myeloma has changed dramatically in recent years, with huge strides forward made in the field. Chimeric antigen receptor T-cell therapy targeting the B cell maturation antigen (BCMA) is now widely approved in relapsed refractory patients and is moving into earlier treatment lines. In this review, we discuss the evidence underpinning current regulatory approvals and consider mechanisms through which CAR-T cell efficacy could be improved. These include tackling BCMA-loss, harnessing the immunosuppressive tumour microenvironment, manufacturing concerns including the potential role of other cellular sources, safety issues such as cytokine release syndrome and neurotoxicity, and optimal patient selection.

Logic-gated and contextual control of immunotherapy for solid tumors: contrasting multi-specific T cell engagers and CAR-T cell therapies

CAR-T cell and T cell engager therapies have demonstrated transformational efficacy against hematological malignancies, but achieving efficacy in solid tumors has been more challenging, in large part because of on-target/off-tumor toxicities and sub-optimal T cell anti-tumor cytotoxic functions. Here, we discuss engineering solutions that exploit biological properties of solid tumors to overcome these challenges. Using logic gates as a framework, we categorize the numerous approaches that leverage two inputs instead of one to achieve better cancer selectivity or efficacy in solid tumors with dual-input CAR-Ts or multi-specific TCEs. In addition to the "OR gate" and "AND gate" approaches that leverage dual tumor antigen targeting, we also review "contextual AND gate" technologies whereby continuous cancer-selective inputs such a pH, hypoxia, target density, tumor proteases, and immune-suppressive cytokine gradients can be creatively incorporated in therapy designs. We also introduce the notion of "output directionality" to distinguish dual-input strategies that mechanistically impact cancer cell killing or T cell fitness. Finally, we contrast the feasibility and potential benefits of the various approaches using CAR-T and TCE therapeutics and discuss why the promising "IF/THEN" and "NOT" gate types pertain more specifically to CAR-T therapies, but can also succeed by integrating both technologies.

T Cell-Redirecting Bispecific Antibodies in Multiple Myeloma: Optimal Dosing Schedule and Duration of Treatment

T cell-redirecting bispecific antibodies (BsAb) induce significant responses in heavily pretreated multiple myeloma. BsAbs are currently administered in a dose-dense manner until disease progression. However, continuous therapy is associated with safety concerns, including a high risk of infections and high costs. In addition, chronic exposure to BsAbs, and thus long-term T-cell stimulation, induces T-cell exhaustion, which may contribute to relapse. There is increasing evidence that the strategy of induction treatment followed by maintenance with longer intervals between BsAb doses, or limited treatment duration with cessation of therapy in patients who achieve deep remission, improves the balance between toxicity and efficacy. Significance: There is increasing evidence that after initial debulking, less-frequent BsAb administration mitigates T-cell exhaustion and minimizes the potential for chronic or cumulative toxicity while maintaining durable clinical responses. In addition, specific patient subsets may experience an extended treatment-free period following fixed-duration treatment. Fixed-duration treatment may, therefore, decrease cumulative toxicities and the burden on patients and healthcare systems.

Chimeric Antigen Receptor T Cells for the Treatment of Multiple Myeloma

Multiple myeloma (MM), characterized by abnormal proliferation of clonal plasma cells, is an incurable hematological malignancy. Various immunotherapy strategies have emerged as an efficacious approach for the treatment of MM, including monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, and chimeric antigen receptor T (CAR-T) cells. Anti-B-cell maturation antigen (BCMA) CAR-T cells have revolutionized the treatment of MM patients with relapsed/refractory disease and their clinical use was approved for the treatment of these patients. Despite this progress, the efficacy of CAR-T cells in MM is limited by the responsiveness of only a part of the treated patients, the relapse of other patients, the cost of the treatment and the diminished response in patients with prior exposure to anti-BCMA targeting agents. Ongoing clinical trials are evaluating the use of CAR-T cells at an earlier stage of MM disease and the use of CAR-T cells targeting other membrane antigens expressed on malignant plasma cells.

Mechanisms and salvage treatments in patients with multiple myeloma relapsed post-BCMA CAR-T cell therapy

Chimeric antigen receptor T-cell (CAR-T) therapy has ushered in a new era for the treatment of multiple myeloma (MM). Numerous clinical studies, especially those involving B-cell maturation antigen (BCMA)-directed CAR-T, have shown remarkable efficacy in patients with relapsed or refractory multiple myeloma (R/R MM). However, a considerable number of patients still experience disease recurrence or progression after BCMA CAR-T treatment, which is attributed to various factors, including antigen escape, CAR-T manufacturing factors, T cell exhaustion, inhibitory effects of tumor microenvironment and impact of prior treatments. The scarcity of effective treatment options following post-CAR-T disease recurrence, coupled with the lack of well-established salvage regimens, leaves patients who do relapse facing a bleak prognosis. In recent years, some academic institutions have achieved certain results in salvage treatments of patients with relapse after BCMA CAR-T treatment through secondary infusion of BCMA CAR-T, changing to non-BCMA-directed CAR-T, double-target CAR-T, bispecific antibodies or other novel therapies. This review summarizes the mechanisms of resistance or relapse after BCMA CAR-T administration and the available data on current salvage treatments, hoping to provide ideas for optimizing clinical salvage therapies.

[BCMA chimeric antigen receptor T cells therapy re-treatment of a patient with recurrent/refractory IgD multiple myeloma: A case report and literature review]

Multiple myeloma (MM) is a malignant plasma cell disease that currently cannot be cured. Several new drugs have continuously been introduced in the recent years. New drugs targeting B-cell maturation antigen (BCMA) have greatly improved the efficacy and prognosis of MM compared with traditional treatments. This article reports the case of an IgD type relapsed and refractory MM patient with poor efficacy of BCMA×CD3 bispecific antibody. The patient achieved deep remission after receiving BCMA-targeted CAR-T cell therapy after initial seven lines of treatment. Literature review was also conducted to improve the clinical physicians' understanding of BCMA target therapy for relapsed and refractory MM patients.

DrugFormer: Graph-Enhanced Language Model to Predict Drug Sensitivity

Drug resistance poses a crucial challenge in healthcare, with response rates to chemotherapy and targeted therapy remaining low. Individual patient's resistance is exacerbated by the intricate heterogeneity of tumor cells, presenting significant obstacles to effective treatment. To address this challenge, DrugFormer, a novel graph-augmented large language model designed to predict drug resistance at single-cell level is proposed. DrugFormer integrates both serialized gene tokens and gene-based knowledge graphs for the accurate predictions of drug response. After training on comprehensive single-cell data with drug response information, DrugFormer model presents outperformance, with higher F1, precision, and recall in predicting drug response. Based on the scRNA-seq data from refractory multiple myeloma (MM) and acute myeloid leukemia (AML) patients, DrugFormer demonstrates high efficacy in identifying resistant cells and uncovering underlying molecular mechanisms. Through pseudotime trajectory analysisunique drug-resistant cellular states associated with poor patient outcomes are revealed. Furthermore, DrugFormer identifies potential therapeutic targets, such as COX8A, for overcoming drug resistance across different cancer types. In conclusion, DrugFormer represents a significant advancement in the field of drug resistance prediction, offering a powerful tool for unraveling the heterogeneity of cellular response to drugs and guiding personalized treatment strategies.

Bispecific antibodies: advancing precision oncology

Bispecific antibodies (bsAbs) are engineered molecules designed to target two different epitopes or antigens. The mechanism of action is determined by the bsAb molecular targets and structure (or format), which can be manipulated to create variable and novel functionalities, including linking immune cells with tumor cells, or dual signaling pathway blockade. Several bsAbs have already changed the treatment landscape of hematological malignancies and select solid cancers. However, the mechanisms of resistance to these agents are understudied and the management of toxicities remains challenging. Herein, we review the principles in bsAb engineering, current understanding of mechanisms of action and resistance, data for clinical application, and provide a perspective on ongoing challenges and future developments in this field.

Measurable Residual Disease Testing in Multiple Myeloma Following T-Cell Redirecting Therapies

Several novel T-cell-based therapies have recently become available for multiple myeloma (MM). These T-cell redirecting therapies (TRTs) include chimeric antigen receptor T-cells (CAR-T) and bispecific antibodies (BiAbs). In both clinical trial and real-world data, these therapies have demonstrated high rates of deep clinical response, and some are now approved for second-line treatment for relapsed MM. The deep and sustained clinical responses these therapies are capable of inducing will require sophisticated response monitoring to provide meaningful information for patient care. Obtaining measurable residual disease (MRD) negativity has been validated as an independent positive prognostic marker for progression-free survival (PFS) and overall survival (OS) in both newly diagnosed and relapsed refractory patients with multiple myeloma. Assessment for MRD negativity was performed in all of the trials for FDA-approved TRT. Here, we summarize pertinent data for MRD assessment following TRT in MM and provide a rationale and structured framework for conducting MRD testing post TRT.

Revolutionizing Cancer Treatment: Recent Advances in Immunotherapy

Cancer immunotherapy has emerged as a transformative approach in oncology, utilizing the body's immune system to specifically target and destroy malignant cells. This review explores the scope and impact of various immunotherapeutic strategies, including monoclonal antibodies, chimeric antigen receptor (CAR)-T cell therapy, checkpoint inhibitors, cytokine therapy, and therapeutic vaccines. Monoclonal antibodies, such as Rituximab and Trastuzumab, have revolutionized treatment paradigms for lymphoma and breast cancer by offering targeted interventions that reduce off-target effects. CAR-T cell therapy presents a potentially curative option for refractory hematologic malignancies, although challenges remain in effectively treating solid tumors. Checkpoint inhibitors have redefined the management of cancers like melanoma and lung cancer; however, managing immune-related adverse events and ensuring durable responses are critical areas of focus. Cytokine therapy continues to play a vital role in modulating the immune response, with advancements in cytokine engineering improving specificity and reducing systemic toxicity. Therapeutic vaccines, particularly mRNA-based vaccines, represent a frontier in personalized cancer treatment, aiming to generate robust, long-lasting immune responses against tumor-specific antigens. Despite these advancements, the field faces significant challenges, including immune resistance, tumor heterogeneity, and the immunosuppressive tumor microenvironment. Future research should address these obstacles through emerging technologies, such as next-generation antibodies, Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)-based gene editing, and AI-driven drug discovery. By integrating these novel approaches, cancer immunotherapy holds the promise of offering more durable, less toxic, and highly personalized treatment options, ultimately improving patient outcomes and survival rates.

Targeting B-cell maturation antigen for treatment and monitoring of relapsed/refractory multiple myeloma patients: a comprehensive review

Despite major therapeutic advancements in recent years, multiple myeloma (MM) remains an incurable disease with nearly all patients experiencing relapsed and refractory disease over the course of treatment. Extending the duration and durability of clinical responses will necessitate the development of therapeutics with novel targets that are capable of robustly and specifically eliminating myeloma cells. B-cell maturation antigen (BCMA) is a membrane-bound protein expressed predominantly on malignant plasma cells and has recently been the target of several novel therapeutics to treat MM patients. This review will focus on recently approved and currently in development agents that target this protein, including bispecific antibodies, antibody-drug conjugates, and chimeric antigen receptor T-cell therapies. In addition, this protein also serves as a novel serum biomarker to predict outcomes and monitor disease status for MM patients; the studies demonstrating this use of BCMA will be discussed in detail.

Bispecific antibodies in the treatment of multiple myeloma

The treatment paradigm in myeloma is constantly changing. Upfront use of monoclonal antibodies like daratumumab along with proteasome inhibitors (PI)s, and immune modulators (IMiD)s have significantly improved survival and outcomes, but also cause unique challenges at the time of relapse. Engaging immune T cells for tumour cell kill with chimeric antigenic T-cell (CAR T-cell) therapy and bispecific antibodies have become important therapeutic options in relapsed multiple myeloma. Bispecific antibodies are dual antigen targeting constructs that engage the T cells to plasma cells through various target antigens like B-cell membrane antigen (BCMA), G-protein-coupled receptor family C group 5 member D (GPRC5D), and Fc receptor-homolog 5 (FcRH5). These agents have proven to induce deep and durable responses in heavily pre-treated myeloma patients with a predictable safety profile and the ease of off-the-shelf availability. Significant research is ongoing to overcome resistance mechanisms like T cell exhaustion, target antigen mutation or loss and high disease burden. Various trials are also studying these agents as first line options in the newly diagnosed setting. These agents play an important role in the relapsed setting, and efforts are underway to optimize their sequencing in the myeloma treatment algorithm.

Updates on CAR T cell therapy in multiple myeloma

Multiple myeloma (MM) is a hematological cancer characterized by the abnormal proliferation of plasma cells. Initial treatments often include immunomodulatory drugs (IMiDs), proteasome inhibitors (PIs), and monoclonal antibodies (mAbs). Despite salient progress in diagnosis and treatment, most MM patients typically have a median life expectancy of only four to five years after starting treatment. In recent developments, the success of chimeric antigen receptor (CAR) T-cells in treating B-cell malignancies exemplifies a new paradigm shift in advanced immunotherapy techniques with promising therapeutic outcomes. Ide-cel and cilta-cel stand as the only two FDA-approved BCMA-targeted CAR T-cells for MM patients, a recognition achieved despite extensive preclinical and clinical research efforts in this domain. Challenges remain regarding certain aspects of CAR T-cell manufacturing and administration processes, including the lack of accessibility and durability due to T-cell characteristics, along with expensive and time-consuming processes limiting health plan coverage. Moreover, MM features, such as tumor antigen heterogeneity, antigen presentation alterations, complex tumor microenvironments, and challenges in CAR-T trafficking, contribute to CAR T-cell exhaustion and subsequent therapy relapse or refractory status. Additionally, the occurrence of adverse events such as cytokine release syndrome, neurotoxicity, and on-target, off-tumor toxicities present obstacles to CAR T-cell therapies. Consequently, ongoing CAR T-cell trials are diligently addressing these challenges and barriers. In this review, we provide an overview of the effectiveness of currently available CAR T-cell treatments for MM, explore the primary resistance mechanisms to these treatments, suggest strategies for improving long-lasting remissions, and investigate the potential for combination therapies involving CAR T-cells.

Mapping the cancer surface proteome in search of target antigens for immunotherapy

Immune-based therapeutic interventions recognizing proteins localized on the cell surface of cancer cells are emerging as a promising cancer treatment. Antibody-based therapies and engineered T cells are now approved by the Food and Drug Administration to treat some malignancies. These therapies utilize a few cell surface proteins highly expressed on cancer cells to release the negative regulation of immune activation that limits antitumor responses (e.g., PD-1, PD-L1, CTLA4) or to redirect the T cell specificity toward blood cancer cells (e.g., CD19 and B cell maturation antigen). One limitation preventing broader application of these novel therapeutic strategies to all cancer types is the lack of suitable target antigens for all indications owing in part to the challenges in identifying such targets. Ideal target antigens are cell surface proteins highly expressed on malignant cells and absent in healthy tissues. Technological advances in mass spectrometry, enrichment protocols, and computational tools for cell surface protein isolation and annotation have recently enabled comprehensive analyses of the cancer cell surface proteome, from which novel immunotherapeutic target antigens may emerge. Here, we review the most recent progress in this field.

T cell-redirecting therapies in hematological malignancies: Current developments and novel strategies for improved targeting

T cell-redirecting therapies (TCRTs), such as chimeric antigen receptor (CAR) or T cell receptor (TCR) T cells and T cell engagers, have emerged as a highly effective treatment modality, particularly in the B and plasma cell-malignancy setting. However, many patients fail to achieve deep and durable responses; while the lack of truly unique tumor antigens, and concurrent on-target/off-tumor toxicities, have hindered the development of TCRTs for many other cancers. In this review, we discuss the recent developments in TCRT targets for hematological malignancies, as well as novel targeting strategies that aim to address these, and other, challenges.

Identification of Therapy-Induced Clonal Evolution and Resistance Pathways in Minimal Residual Clones in Multiple Myeloma through Single-Cell Sequencing

PURPOSE

In multiple myeloma (MM), therapy-induced clonal evolution is associated with treatment resistance and is one of the most important hindrances toward a cure for MM. To further understand the molecular mechanisms controlling the clonal evolution of MM, we applied single-cell RNA sequencing (scRNA-seq) to paired diagnostic and posttreatment bone marrow (BM) samples.

EXPERIMENTAL DESIGN

scRNA-seq was performed on 38 BM samples from patients with monoclonal gammopathy of undetermined significance (n = 1), MM patients at diagnosis (n = 19), MM posttreatment (n = 17), and one healthy donor (HD). The single-cell transcriptome data of malignant plasma cells (PC) and the surrounding immune microenvironment were analyzed.

RESULTS

Profiling by scRNA-seq data revealed three primary trajectories of transcriptional evolution after treatment: clonal elimination in patients with undetectable minimal residual disease (MRD-) and clonal stabilization and clonal selection in detectable MRD (MRD+) patients. We noted a metabolic shift toward fatty acid oxidation in cycling-resistant PCs, whereas selective PCs favored the NF-κB pathway. Intriguingly, when comparing the genetic and transcriptional dynamics, we found a significant correlation between genetic and nongenetic factors in driving the clonal evolution. Furthermore, we identified variations in cellular interactions between malignant PCs and the tumor microenvironment. Selective PCs showed the most robust cellular interactions with the tumor microenvironment.

CONCLUSIONS

These data suggest that MM cells could rapidly adapt to induction treatment through transcriptional adaptation, metabolic adaptation, and specialized immune evasion. Targeting therapy-induced resistance mechanisms may help to avert refractory disease in MM.

Single-cell multiomic dissection of response and resistance to chimeric antigen receptor T cells against BCMA in relapsed multiple myeloma

Markers that predict response and resistance to chimeric antigen receptor (CAR) T cells in relapsed/refractory multiple myeloma are currently missing. We subjected mononuclear cells isolated from peripheral blood and bone marrow before and after the application of approved B cell maturation antigen-directed CAR T cells to single-cell multiomic analyses to identify markers associated with resistance and early relapse. Differences between responders and nonresponders were identified at the time of leukapheresis. Nonresponders showed an immunosuppressive microenvironment characterized by increased numbers of monocytes expressing the immune checkpoint molecule CD39 and suppressed CD8+ T cell and natural killer cell function. Analysis of CAR T cells showed cytotoxic and exhausted phenotypes in hyperexpanded clones compared to low/intermediate expanded clones. We identified potential immunotherapy targets on CAR T cells, like PD1, to improve their functionality and durability. Our work provides evidence that an immunosuppressive microenvironment causes resistance to CAR T cell therapies in multiple myeloma.