B cell maturation antigen-specific chimeric antigen receptor T cells for relapsed or refractory multiple myeloma: A meta-analysis

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.

Polymer Backpack-Loaded Tissue Infiltrating Monocytes for Treating Cancer

Adoptive cell therapies are dramatically altering the treatment landscape of cancer. However, treatment of solid tumors remains a major unmet need, in part due to limited adoptive cell infiltration into the tumor and in part due to the immunosuppressive tumor microenvironment. The heterogeneity of tumors and presence of nonresponders also call for development of antigen-independent therapeutic approaches. Myeloid cells offer such an opportunity, given their large presence in the immunosuppressive tumor microenvironment, such as in triple negative breast cancer. However, their therapeutic utility is hindered by their phenotypic plasticity. Here, the impressive trafficking ability of adoptively transferred monocytes is leveraged into the immunosuppressive 4T1 tumor to develop an antitumor therapy. To control monocyte differentiation in the tumor microenvironment, surface-adherent "backpacks" stably modified with interferon gamma (IFNγ) are developed to stimulate macrophage plasticity into a pro-inflammatory, antitumor phenotype, a strategy as referred to as Ornate Polymer backpacks on Tissue Infiltrating Monocytes (OPTIMs). Treatment with OPTIMs substantially reduces tumor burden in a mouse 4T1 model and significantly increases survival. Cytokine and immune cell profiling reveal that OPTIMs remodeled the tumor microenvironment into a pro-inflammatory state.

Enhanced cytotoxicity in multiple myeloma via T cells armed with bispecific T cell engager targeting B-cell maturation antigen on cancer cells and CD3 on T cells

Multiple myeloma (MM), a cancer of plasma cells, remains difficult to treat due to its incurability and high recurrence rates. Recent advancements in immunotherapies, such as CAR T cells, bispecific antibodies, and bispecific T cell engagers (BITEs) targeting B-cell maturation antigen (BCMA), have improved treatment options for relapsed and refractory MM (RRMM). However, these therapies face challenges, including complex manufacturing, high cost, and severe side effects. In this study, we developed a stable cell line that produces anti-BCMA × anti-CD3 BITEs and generated BITE-armed T cells (BATs) as a novel MM treatment approach. These αBCMA × αCD3 BATs specifically targeted BCMA-expressing cells, promoting T cell activation, proliferation, and cytotoxicity. BATs demonstrated superior cytotoxicity compared to unarmed T cells, likely due to enhanced antigen specificity and targeting efficiency, even at low effector-to-target ratios. The antitumor activity of BATs against BCMA-expressing cells was antigen-specific and dose-dependent. BATs also triggered T cell expansion and significant cytokine release (IL-2, TNF-α, IFN-γ) without increasing IL-6, suggesting a lower risk of cytokine release syndrome (CRS). Our findings indicate that BCMA-targeting BATs offer a promising and accessible therapeutic strategy for MM, with a simple, rapid, and cost-effective production process. These results support future development of BITE-armed T cells as a novel cancer treatment to enhance therapeutic outcomes for MM patients.

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.

BCMA CAR-T therapy combined with pomalidomide is a safe and effective treatment for relapsed/refractory multiple myeloma

BACKGROUND

B-cell maturation antigen (BCMA)-targeted chimeric antigen receptor T-cell (CAR T-cell) therapy has exhibited remarkable efficacy in refractory or relapsed multiple myeloma (R/R MM), but recurrence and rapid progression of disease are still observed within a short time after treatment. Long-term pomalidomide therapy, which potentiates T-cell functionality, might enhance the efficacy of BCMA CAR T-cell therapy.

METHODS

We performed a single-center retrospective clinical study. Patients with relapsed or refractory multiple myeloma who received BCMA CAR T-cell infusion were enrolled in our study, and were followed by long-term pomalidomide treatment (4 mg/day) or not one month after infusion. The response and adverse events were assessed after infusion. The effect of pomalidomide on BCMA CAR T-cells was assessed in vitro.

RESULTS

The objective response rate (ORR) of BCMA-CART was 100%. Three months following CAR T-cell infusion, of the 8 patients receiving pomalidomide, except for 2 patients who stopped maintenance therapy and were lost to follow-up, all patients (6/6) achieved VGPR (very good partial response) or CR (complete response), while only 5 patients (5/8) who did not receive pomalidomide treatment achieved VGPR or better. At a median follow-up of 27 months, for the 8 patients who did not receive pomalidomide administration, the median TTP (time to progression) was 5.85 (1-14) months, while the OS (overall survival) was 10.7 (1.2-16) months. Of the 8 patients who received pomalidomide therapy after CAR T-cell infusion, the median TTP was 13 (7-13) months, while the OS was not reached. Moreover, neither long-term hematological toxicity nor drug-induced liver damage was observed during the follow-up period. Mechanistically, pomalidomide promotes antimyeloma efficacy of BCMA CAR T-cells by inhibiting cell apoptosis and enhancing cytoxicity.

CONCLUSIONS

Our results confirmed that BCMA CAR T-cell therapy combined with long-term pomalidomide had a low recurrence rate and manageable therapy-related side effects, providing a promising option for treating R/R MM.

Successful Treatment of Refractory Orbital Plasmacytoma with Chimeric Antigen Receptor T Cell Therapy: A Case Report and Review of the Literature

Orbital plasmacytoma is a rare plasma cell tumor that may arise as an aggressive form of extramedullary multiple myeloma. Treatment modalities include surgical excision, radiation, and chemotherapy. Chimeric antigen receptor T cell therapy is currently reserved for refractory disease. The authors present a case of a 69-year-old woman with an extensive orbital plasmacytoma refractory to multimodal therapy who was treated with idecabtagene vicleucel chimeric antigen receptor T cell therapy. Four days after infusion, the patient exhibited grade 1 cytokine release syndrome, which resolved with tocilizumab. The orbital plasmacytoma significantly decreased in size 1 month after treatment and demonstrated complete serological response and sustained tumor burden reduction at 10-month follow-up. This case highlights the efficacy of chimeric antigen receptor T cell therapy for refractory orbital plasmacytoma and calls attention to potential inflammatory toxicities.

Impact of Treatment Modality and Route of Administration on Cytokine Release Syndrome in Relapsed or Refractory Multiple Myeloma: A Meta-Analysis

B-cell maturation antigen (BCMA)-targeting immunotherapies (e.g., chimeric antigen receptor T cells (CAR-T) and bispecific antibodies (BsAbs)) have achieved remarkable clinical responses in patients with relapsed and/or refractory multiple myeloma (RRMM). Their use is accompanied by exaggerated immune responses related to T-cell activation and cytokine elevations leading to cytokine release syndrome (CRS) in some patients, which can be potentially life-threatening. However, systematic evaluation of the risk of CRS with BCMA-targeting BsAb and CAR-T therapies, and comparisons across different routes of BsAb administration (intravenous (i.v.) vs. subcutaneous (s.c.)) have not previously been conducted. This study utilized a meta-analysis approach to compare the CRS profile in BCMA-targeting CAR-T vs. BsAb immunotherapies administered either i.v. or s.c. in patients with RRMM. A total of 36 studies including 1,560 patients with RRMM treated with BCMA-targeting CAR-T and BsAb therapies were included in the analysis. The current analysis suggests that compared with BsAbs, CAR-T therapies were associated with higher CRS incidences (88% vs. 59%), higher rates of grade ≥ 3 CRS (7% vs. 2%), longer CRS duration (5 vs. 2 days), and more prevalent tocilizumab use (44% vs. 25%). The proportion of CRS grade ≥ 3 may also be lower (0% vs. 4%) for BsAb therapies administered via the s.c. (3 studies, n = 311) vs. i.v. (5 studies, n = 338) route. This meta-analysis suggests that different types of BCMA-targeting immunotherapies and administration routes could result in a range of CRS incidence and severity that should be considered while evaluating the benefit-risk profiles of these therapies.

BCMA/CD47-directed universal CAR-T cells exhibit excellent antitumor activity in multiple myeloma

BACKGROUND

BCMA-directed autologous chimeric antigen receptor T (CAR-T) cells have shown excellent clinical efficacy in relapsed or refractory multiple myeloma (RRMM), however, the current preparation process for autologous CAR-T cells is complicated and costly. Moreover, the upregulation of CD47 expression has been observed in multiple myeloma, and anti-CD47 antibodies have shown remarkable results in clinical trials. Therefore, we focus on the development of BCMA/CD47-directed universal CAR-T (UCAR-T) cells to improve these limitations.

METHODS

In this study, we employed phage display technology to screen nanobodies against BCMA and CD47 protein, and determined the characterization of nanobodies. Furthermore, we simultaneously disrupted the endogenous TRAC and B2M genes of T cells using CRISPR/Cas9 system to generate TCR and HLA double knock-out T cells, and developed BCMA/CD47-directed UCAR-T cells and detected the antitumor activity in vitro and in vivo.

RESULTS

We obtained fourteen and one specific nanobodies against BCMA and CD47 protein from the immunized VHH library, respectively. BCMA/CD47-directed UCAR-T cells exhibited superior CAR expression (89.13-98.03%), and effectively killing primary human MM cells and MM cell lines. BCMA/CD47-directed UCAR-T cells demonstrated excellent antitumor activity against MM and prolonged the survival of tumor-engrafted NCG mice in vivo.

CONCLUSIONS

This work demonstrated that BCMA/CD47-directed UCAR-T cells exhibited potent antitumor activity against MM in vitro and in vivo, which provides a potential strategy for the development of a novel "off-the-shelf" cellular immunotherapies for the treatment of multiple myeloma.

[Consensus for the diagnosis and management of extramedullary plasmacytoma in China(2024)]

Extramedullary plasmacytoma (EMP) is a special type of malignant plasmacytosis, which is complex and heterogeneous. Most EMP patients have poor prognosis and lack a stratified prognostic system or ideal treatment strategy supported by evidence-based medical evidence, which cannot meet clinical needs. In order to improve the understanding of this disease entity, Plasma Cell Disease Group, Chinese Society of Hematology, Chinese Medical Association and Chinese Myeloma Committee-Chinese Hematology Association developed the "Chinese Expert Consensus on the diagnosis and treatment of extramedullary plasmacytoma", which aims to standardize the clinical diagnosis and treatment of EMP and ultimately improve the overall survival of patients with plasmacytoma.

CAR-T Therapy in Relapsed Refractory Multiple Myeloma

Multiple myeloma is a plasma cell neoplasm. The emergence of proteasome inhibitors, immunomodulatory drugs, and anti-CD38 monoclonal antibodies has improved the prognosis of multiple myeloma patients. However, some patients are still insensitive to conventional therapy or frequently relapse after remission. Chemotherapy based on proteasome inhibitors or immunomodulatory drugs is ineffective in controlling the progression of relapsed refractory multiple myeloma. No consensus has been reached on treating relapsed refractory multiple myeloma to date. Recently chimeric antigen receptor T cells therapy has shown promising results that could achieve rapid remissions of patients and improve their prognoses. Additionally, most patients in chimeric antigen receptor T cell clinical trials were triple-refractory multiple myeloma patients, indicating that chimeric antigen receptor T cell immunotherapy could overcome drug resistance to new drugs. Since single immunotherapies are prone to acquired resistance, combination immunotherapies based on emerging immunotherapies may solve this issue. Achieving complete remission and minimal residual disease negative status as soon as possible is beneficial to patients. This paper reviewed the main chimeric antigen receptor T cell products in relapsed refractory multiple myeloma, and it explained the drug resistance mechanism and improvement methods of chimeric antigen receptor T cells therapy. This review summarized the best beneficiaries of chimeric antigen receptor T cell therapy and the salvage treatment of disease recurrence after chimeric antigen receptor T cell therapy, providing some ideas for the clinical application of chimeric antigen receptor T cells.

Immunotherapy of Multiple Myeloma: Current Status as Prologue to the Future

The landscape of therapeutic measures to treat multiple myeloma has undergone a seismic shift since the dawn of the current century. This has been driven largely by the introduction of new classes of small molecules, such as proteasome blockers (e.g., bortezomib) and immunomodulators (e.g., lenalidomide), as well as by immunotherapeutic agents starting with the anti-CD38 monoclonal antibody daratumumab in 2015. Recently, other immunotherapies have been added to the armamentarium of drugs available to fight this malignancy. These include the bispecifics teclistamab, talquetamab, and elranatamab, and the chimeric antigen receptor (CAR) T-cell products idecabtagene vicleucel (ide-cel) and ciltacabtagene autoleucel (cilta-cel). While the accumulated benefits of these newer agents have resulted in a more than doubling of the disease's five-year survival rate to nearly 60% and improved quality of life, the disease remains incurable, as patients become refractory to the drugs and experience relapse. This review covers the current scope of antimyeloma immunotherapeutic agents, both those in clinical use and in development. Included in the discussion are additional monoclonal antibodies (mAbs), antibody-drug conjugates (ADCs), bi- and multitargeted mAbs, and CAR T-cells and emerging natural killer (NK) cells, including products intended for "off-the-shelf" (allogeneic) applications. Emphasis is placed on the benefits of each along with the challenges that need to be surmounted if MM is to be cured.

Anti-myeloma efficacy of CAR-iNKT is enhanced with a long-acting IL-7, rhIL-7-hyFc

Multiple myeloma (MM), a malignancy of mature plasma cells, remains incurable. B-cell maturation antigen (BCMA) is the lead protein target for chimeric antigen receptor (CAR) therapy because of its high expression in most MM, with limited expression in other cell types, resulting in favorable on-target, off tumor toxicity. The response rate to autologous BCMA CAR-T therapy is high; however, it is not curative and is associated with risks of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome. Outcomes in patients treated with BCMA CAR-T cells (CAR-Ts) may improve with allogeneic CAR T-cell therapy, which offer higher cell fitness and reduced time to treatment. However, to prevent the risk of graft-versus-host disease (GVHD), allogenic BCMA CAR-Ts require genetic deletion of the T-cell receptor (TCR), which has potential for unexpected functional or phenotype changes. Invariant natural killer T cells (iNKTs) have an invariant TCR that does not cause GVHD and, as a result, can be used in an allogeneic setting without the need for TCR gene editing. We demonstrate significant anti-myeloma activity of BCMA CAR-iNKTs in a xenograft mouse model of myeloma. We found that a long-acting interleukin-7 (IL-7), rhIL-7-hyFc, significantly prolonged survival and reduced tumor burden in BCMA CAR-iNKT-treated mice in both primary and re-challenge settings. Furthermore, in CRS in vitro assays, CAR-iNKTs induced less IL-6 than CAR-Ts, suggesting a reduced likelihood of CAR-iNKT therapy to induce CRS in patients. These data suggest that BCMA CAR-iNKTs are potentially a safer, effective alternative to BCMA CAR-Ts and that BCMA CAR-iNKT efficacy is further potentiated with rhIL-7-hyFc.

Effectiveness and safety of anti-BCMA chimeric antigen receptor T-cell treatment in relapsed/refractory multiple myeloma: a comprehensive review and meta-analysis of prospective clinical trials

Background: Chimeric antigen receptor T cells treatment targeting B cell maturation antigen (BCMA) is an emerging treatment option for relapsed/refractory multiple myeloma (RRMM) and has demonstrated outstanding outcomes in clinical studies. Objective: The aim of this comprehensive review and meta-analysis was to summarize the effectiveness and safety of anti-BCMA CAR-T treatment for patients with relapsed/refractory multiple myeloma (RRMM). Our research identifies variables influencing outcome measures to provide additional evidence for CAR-T product updates, clinical trial design, and clinical treatment guidance. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standard was followed for conducting this comprehensive review and meta-analysis, which was submitted to PROSPERO (CRD42023390037). From the inception of the study until 10 September 2022, PubMed, Web of Science, EMBASE, the Cochrane Library, CNKI, and WanFang databases were searched for eligible studies. Stata software (version 16.0) was used to assess effectiveness and safety outcomes. Results: Out of 875 papers, we found 21 relevant trials with 761 patients diagnosed as RRMM and were given anti-BCMA CAR-T treatment. The overall response rate (ORR) for the entire sample was 87% (95% CI: 80-93%) complete response rate (CRR) was 44% (95% CI: 34-54%). The minimal residual disease (MRD) negativity rate within responders was 78% (95% CI: 65-89%). The combined incidence of cytokine release syndrome was 82% (95% CI: 72-91%) and neurotoxicity was 10% (95% CI: 5%-17%). The median progression-free survival (PFS) was 8.77 months (95% CI: 7.48-10.06), the median overall survival (OS) was 18.87 months (95% CI: 17.20-20.54) and the median duration of response (DOR) was 10.32 months (95% CI: 9.34-11.31). Conclusion: According to this meta-analysis, RRMM patients who received anti-BCMA CAR-T treatment have demonstrated both effectiveness and safety. Subgroup analysis confirmed the anticipated inter-study heterogeneity and pinpointed potential factors contributing to safety and efficacy, which may help with the development of CAR-T cell studies and lead to optimized BCMA CAR-T-cell products. Systematic Review Registration: Clinicaltrials.gov, PROSPERO, CRD42023390037.

Chimeric antigen receptor T cells targeting FcRH5 provide robust tumour-specific responses in murine xenograft models of multiple myeloma

BCMA-targeting chimeric antigen receptor (CAR) T cell therapy demonstrates impressive clinical response in multiple myeloma (MM). However, some patients with BCMA-deficient tumours cannot benefit from this therapy, and others can experience BCMA antigen loss leading to relapse, thus necessitating the identification of additional CAR-T targets. Here, we show that FcRH5 is expressed on multiple myeloma cells and can be targeted with CAR-T cells. FcRH5 CAR-T cells elicited antigen-specific activation, cytokine secretion and cytotoxicity against MM cells. Moreover, FcRH5 CAR-T cells exhibited robust tumoricidal efficacy in murine xenograft models, including one deficient in BCMA expression. We also show that different forms of soluble FcRH5 can interfere with the efficacy of FcRH5 CAR-T cells. Lastly, FcRH5/BCMA-bispecific CAR-T cells efficiently recognized MM cells expressing FcRH5 and/or BCMA and displayed improved efficacy, compared with mono-specific CAR-T cells in vivo. These findings suggest that targeting FcRH5 with CAR-T cells may represent a promising therapeutic avenue for MM.

Directed targeting of B-cell maturation antigen-specific CAR T cells by bioinformatic approaches: From in-silico to in-vitro

AIMS

Chimeric Antigen Receptor (CAR) T-cell is a breakthrough in cancer immunotherapy. The primary step of successful CAR T cell therapy is designing a specific single-chain fragment variable (scFv). This study aims to verify the designed anti-BCMA (B cell maturation antigen) CAR using bioinformatic techniques with the following experimental evaluations.

MAIN METHODS

Following the second generation of anti-BCMA CAR designing, the protein structure, function prediction, physicochemical complementarity at the ligand-receptor interface, and biding sites analysis of anti-BCMA CAR construct were confirmed using different modeling and docking server, including Expasy, I-TASSER, HDock, and PyMOL software. To generate CAR T-cells, isolated T cells were transduced. Then, anti-BCMA CAR mRNA and its surface expression were confirmed by real-time -PCR and flow cytometry methods, respectively. To evaluate the surface expression of anti-BCMA CAR, anti-(Fab')2 and anti-CD8 antibodies were employed. Finally, anti-BCMA CAR T cells were co-cultured with BCMA+/- cell lines to assess the expression of CD69 and CD107a as activation and cytotoxicity markers.

KEY FINDINGS

In-silico results approved the suitable protein folding, perfect orientation, and correct locating of functional domains at the receptor-ligand binding site. The in-vitro results confirmed high expression of scFv (89 ± 1.15% (and CD8α (54 ± 2.88%). The expression of CD69 (91.97 ± 1.7%) and CD107a (92.05 ± 1.29%) were significantly increased, indicating appropriate activation and cytotoxicity.

SIGNIFICANCE

In-silico studies before experimental assessments are crucial for state-of-art CAR designing. Highly activation and cytotoxicity of anti-BCMA CAR T-cell revealed that our CAR construct methodology would be applicable to define the road map of CAR T cell therapy.

Outcomes After Salvage Autologous Hematopoietic Cell Transplant for Patients With Relapsed/Refractory Multiple Myeloma: A Single-Institution Experience

BACKGROUND

The role of salvage autologous hematopoietic cell transplantation (sAHCT2) for patients with relapsed/refractory multiple myeloma (RRMM) in the era of modern therapeutics is unclear. As prospective data is limited, we conducted a retrospective analysis to determine the outcomes of sAHCT2.

PATIENTS AND METHODS

We conducted a single-institution, retrospective analysis of patients who received sAHCT2 at The Ohio State University from 2000 to 2018. Patients who received a second transplant as part of a planned tandem or autologous-allogeneic transplant were excluded.

RESULTS

Fifty-seven patients were treated with sAHCT2. Patients had a median of 2 lines of therapy after AHCT1 prior to their sAHCT2; 70% had prior immunomodulatory imide drugs, 82% had prior proteasome inhibitor, and 20% had prior anti-CD38 monoclonal antibodies as part of re-induction therapy. Forty-two percent of patients attained ≥VGPR prior to sAHCT2. Seventy-four were treated with melphalan 200 mg/m² as conditioning regimen before infusion of a median of 3.8 × 10⁶ CD34+ cells/kg. Fifty-eight percent patients had maintenance therapy and 81% patients attained CR/VGPR as the best response after sAHCT2. The median PFS and OS after sAHCT2 were 1.6 and 3.6 years, respectively. On multivariable analysis, high-risk cytogenetics, not having attained CR/VGPR, and having more than 2 lines of therapy post-AHCT1 were associated with inferior PFS. Melphalan 140 mg/m² compared to melphalan 200 mg/m² and no maintenance therapy compared to maintenance therapy were not associated with inferior PFS. There was no transplant-related mortality in this patient cohort.

CONCLUSIONS

For MM patients deriving durable remission after their AHCT1, sAHCT2 was safe and resulted in deep and durable remissions.

Negative E-cadherin expression on bone marrow myeloma cell membranes is associated with extramedullary disease

Background: The loss of E-cadherin expression and the induction of N-cadherin are known as hallmarks of the epithelial-to-mesenchymal transition, an essential initial step in the process of metastasis in solid tumors. Although several studies have reported expressions of these cadherins in patients with multiple myeloma (MM), their clinical significance is unknown as MM cells are non-epithelial. Methods: In this study, we examined the expression of E- and N-cadherins by immunohistochemistry using bone marrow (BM) biopsy specimens from 31 newly diagnosed MM patients and in subsequent biopsy specimens from six of these. Results: Negative E-cadherin expression on BM myeloma cell membranes was significantly associated with the presence of soft-tissue masses arising from bone lesions and breaking through the cortical bone, referred to as extramedullary disease (EMD). Conclusions: Given the aggressive nature of EMD, our study suggests that screening for E-cadherin using BM immunohistochemistry is one measure that could predict the development of EMD in patients with MM.

Access to and affordability of CAR T-cell therapy in multiple myeloma: an EBMT position paper

Chimeric antigen receptor (CAR) T-cell therapy is a promising immunotherapeutic approach in the treatment of multiple myeloma, and the recent approval of the first two CAR T-cell products could result in improved outcomes. However, it remains a complex and expensive technology, which poses challenges to health-care systems and society in general, especially in times of crises. This potentially accelerates pre-existing inequalities as access to CAR T-cell therapy varies, both between countries, depending on the level of economic development, and within countries, due to structural disparities in access to quality health care-a parameter strongly correlated with socioeconomic status, ethnicity, and lifestyle. Here, we identify two important issues: affordability and access to CAR T-cell treatment. This consensus statement from clinical investigators, clinicians, nurses, and patients from the European Society for Blood and Marrow Transplantation (EBMT) proposes solutions as part of an innovative collaborative strategy to make CAR T-cell therapy accessible to all patients with multiple myeloma.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

TRIAL REGISTRATION NUMBER

NCT03815383, NCT03751293, NCT04295018, and NCT04322292.

Road testing new CAR design strategies in multiple myeloma

A deeper understanding of basic immunology principles and advances in bioengineering have accelerated the mass production of genetically-reprogrammed T-cells as living drugs to treat human diseases. Autologous and allogeneic cytotoxic T-cells have been weaponized to brandish MHC-independent chimeric antigen receptors (CAR) that specifically engage antigenic regions on tumor cells. Two distinct CAR-based therapeutics designed to target BCMA are now FDA-approved based upon robust, sustained responses in heavily-pretreated multiple myeloma (MM) patients enrolled on the KarMMa and CARTITUDE-1 studies. While promising, CAR T-cells present unique challenges such as antigen escape and T-cell exhaustion. Here, we review novel strategies to design CARs that overcome current limitations. Co-stimulatory signaling regions were added to second-generation CARs to promote IL-2 synthesis, activate T-cells and preclude apoptosis. Third-generation CARs are composed of multiple co-stimulatory signaling units, e.g., CD28, OX40, 4-1BB, to reduce exhaustion. Typically, CAR T-cells incorporate a potent constitutive promoter that maximizes long-term CAR expression but extended CAR activation may also promote T-cell exhaustion. Hypoxia-inducible elements can be incorporated to conditionally drive CAR expression and selectively target MM cells within bone marrow. CAR T-cell survival and activity is further realized by blocking intrinsic regulators of T-cell inactivation. T-Cells Redirected for Universal Cytokine Killing (TRUCKs) bind a specific tumor antigen and produce cytokines to recruit endogenous immune cells. Suicide genes have been engineered into CAR T-cells given the potential for long-term on-target, off-tumor effects. Universal allo-CAR T-cells represent an off-the-shelf source, while logic-gated CAR T-cells are designed to recognize tumor-specific features coupled with Boolean-generated binary gates that then dictate cell-fate decisions. Future generations of CARs should further revitalize immune responses, enhance tumor specificity and reimagine strategies to treat myeloma and other cancers.

Central Nervous System Myeloma and Unusual Extramedullary Localizations: Real Life Practical Guidance

Central nervous system localization of multiple myeloma (CNS-MM) accounts for about 1% of all MM during disease course or even rarer at diagnosis. A difference in the origin, i.e., osteodural or primary dural vs leptomeningeal/intraparenchymal, seems to define two distinct types of intracranial myeloma, with different clinical behavior. CNS-MM may occur also as a presentation of MM. Treatment is still unsatisfactory and many treatments have been reported: chemotherapy, intrathecal therapy, and radiotherapy, with dismal prognosis. Other sites of myeloma localization could be also of interest and deserve description. Because of the rarity and aggressiveness of the disease clinicians are often doubtful on how to treat it since there is no general agreement. Moreover, recent drugs such as the anti CD38 monoclonal antibody, immunomodulatory drugs, and proteasome inhibitors have changed the treatment of patients with MM with a significant improvement in overall response and survival. The role of novel agents in CNS MM management and unusual presentations will be discussed as well as the potential role of other new immunomodulatory drugs and proteasome inhibitors that seem to cross the blood-brain barrier. The purpose of this review is to increase awareness of the clinical unusual presentation and neuroradiological findings, give practical diagnostic advice and treatment options algorithm.

Novel immunotherapies in multiple myeloma

For a substantial period, options for the treatment of multiple myeloma (MM) were limited; however, the advent of novel therapies into clinical practice in the 1990s resulted in dramatic changes in the prognosis of the disease. Subsequently, new proteasome inhibitors and immunomodulators with innovations in efficacy and toxicity were introduced; yet there remains a spectrum of patients with poor outcomes with current treatment strategies. One of the causes of disease progression in MM is the loss of the ability of the dysfunctional immune environment to control virulent cell clones. In recent years, therapies to overcome the immunosuppressive tumor microenvironment and activate the host immune system have shown promise in MM, especially in relapsed and refractory disease. Clinical use of this approach has been approved for several immunotherapies, and a number of studies are currently underway in clinical trials. This review outlines three of the newest and most promising approaches being investigated to enhance the immune system against MM: (1) overcoming immunosuppression with checkpoint inhibitors, (2) boosting immunity against tumors with vaccines, and (3) enhancing immune effectors with adoptive cell therapy. Information on the latest clinical trials in each class will be provided, and further developments will be discussed.

Armored BCMA CAR T Cells Eliminate Multiple Myeloma and Are Resistant to the Suppressive Effects of TGF-β

CAR T-cell therapies targeting the B-cell maturation antigen eliminate tumors in relapsed/refractory multiple myeloma patients, however durable remissions remain difficult to attain. Transforming growth factor beta (TGF-β) is a multifunctional cytokine abundantly expressed in the multiple myeloma bone marrow niche, where it promotes an immunosuppressive tumor microenvironment. We hypothesized that BCMA CAR T-cells armored to resist the suppressive effects of TGF-β will provide an advantage in treating multiple myeloma. The armored B2ARM CAR T cells, co-expressing BCMA targeting CAR with TGF-β dominant-negative receptor II, were generated by lentiviral transduction of primary human CD4+ and CD8+ T cells. The B2ARM CAR T cells eliminated MM.1S multiple myeloma targets in long-term cytotoxicity assays, even under TGF-β-high conditions, whereas cytotoxic function of the non-armored B2 CAR -T cells was inhibited by TGF-β. Concordantly, after long-term exposure to targets in the presence of TGF-β, the B2ARM CAR T cells were enriched for Granzyme B, CD107a, Ki67 and polyfunctional cells T-cells (double or triple-positive for IFN-γ, IL-2 and/or TNF-α), as determined by flow cytometry. In addition, the B2ARM CAR T-cells, but not the conventional B2 CAR T-cells, resisted the TGF-β-mediated suppression of activation (CD25), exhaustion (PD-1, LAG3), and differentiation to T effectors (CD45RA+ CD45RO-CD62L-). In NSG mice bearing RPMI-8226 tumors overexpressing TGF-β, the B2ARM CAR mediated 100% tumor rejection and survival, superior infiltration of tumors on day 7 post CAR T treatment (%CD3+CAR+), and greater expression of IFN-γ, TNF-α, Ki67, Granzyme B, and PD-1, as compared to tumor-infiltrating non-armored B2 CAR T-cells. In NSG RPMI-8226 xenograft model in which tumors were additionally supplemented with TGF-β injections on days -1 through 11 of CAR T treatment, the B2ARM CAR T cells rejected tumors faster than the non-armored B2 CARs, and showed greater numbers of CD3+ and CD3+CAR+, central memory (CD45RO+CD62L+) and effector memory (CD45RO+CD62L-) T cells in the peripheral blood 18 days after treatment. In summary, the armored B2ARM CAR T cells mediate superior persistence, proliferation, multi-functionality, effector differentiation and anti-tumor function in pre-clinical models of multiple myeloma, while abrogating TGF-β-mediated suppression.

Negative E-cadherin expression on bone marrow myeloma cell membranes is associated with extramedullary disease

Background: The loss of E-cadherin expression and the induction of N-cadherin are known as hallmarks of the epithelial-to-mesenchymal transition, an essential initial step in the process of metastasis in solid tumors. Although several studies have reported expressions of these cadherins in patients with multiple myeloma (MM), their clinical significance is unknown as MM cells are non-epithelial. Methods: In this study, we examined the expression of E- and N-cadherins by immunohistochemistry using bone marrow (BM) biopsy specimens from 31 newly diagnosed MM patients and in subsequent biopsy specimens from six of these. Results: Negative E-cadherin expression on BM myeloma cell membranes was significantly associated with the presence of soft-tissue masses arising from bone lesions and breaking through the cortical bone, referred to as extramedullary disease (EMD). Conclusions: Given the aggressive nature of EMD, our study suggests that screening for E-cadherin using BM immunohistochemistry is one measure that could predict the development of EMD in patients with MM.

Neurocognitive and hypokinetic movement disorder with features of parkinsonism after BCMA-targeting CAR-T cell therapy

B-cell maturation antigen (BCMA) is a prominent tumor-associated target for chimeric antigen receptor (CAR)-T cell therapy in multiple myeloma (MM). Here, we describe the case of a patient with MM who was enrolled in the CARTITUDE-1 trial ( NCT03548207 ) and who developed a progressive movement disorder with features of parkinsonism approximately 3 months after ciltacabtagene autoleucel BCMA-targeted CAR-T cell infusion, associated with CAR-T cell persistence in the blood and cerebrospinal fluid, and basal ganglia lymphocytic infiltration. We show BCMA expression on neurons and astrocytes in the patient's basal ganglia. Public transcriptomic datasets further confirm BCMA RNA expression in the caudate of normal human brains, suggesting that this might be an on-target effect of anti-BCMA therapy. Given reports of three patients with grade 3 or higher parkinsonism on the phase 2 ciltacabtagene autoleucel trial and of grade 3 parkinsonism in the idecabtagene vicleucel package insert, our findings support close neurological monitoring of patients on BCMA-targeted T cell therapies.

Comprehensive meta-analysis of anti-BCMA chimeric antigen receptor T-cell therapy in relapsed or refractory multiple myeloma

BACKGROUND

Chimeric antigen receptor (CAR) T-cell therapy shows impressive results in clinical trials. We conducted a meta-analysis based on the most recent data to systematically describe the efficacy and safety of anti-BCMA CAR T therapy for patients with relapsed or refractory multiple myeloma (R/R MM).

METHODS

PubMed, Embase, Web of Science, Cochrane library, ClinicalTrials.gov, China Biology Medicine disc (CBM disc) and Wanfang Data were searched on 8 November 2020. Registration number of PROSPERO was CRD42020219127.

RESULTS

From 763 articles, we identified 22 appropriate studies with 681 patients. The pooled overall response rate (ORR) was 85.2% (95%CI 0.797-0.910), complete response rate (CRR) was 47.0% (95%CI 0.378-0.583), and minimal residual disease (MRD) negativity rate was 97.8% (95%CI 0.935-1.022). The pooled incidence of grade 3-4 cytokine release syndrome was 6.6% (95%CI 0.036-0.096) and neurotoxicity was 2.2% (95%CI 0.006-0.038). The median progression-free survival (PFS) was 14.0 months and median overall survival (OS) was 24.0 months. Subgroup analysis showed dual epitope-binding CAR T cells achieved the best therapy outcomes and humanized CAR T cells had the best safety profile. Patients who were older, heavily pre-treated or received lower dose of CAR T cells had worse ORR. There was no significant difference in ORR, CRR and PFS between patients with and without high-risk cytogenetic features. The PFS and CRR of non-extramedullary disease (EMD) group was superior to those of EMD group.

CONCLUSION

Anti-BCMA CAR T therapy is effective and safe for patients with R/R MM. It can improve the prognosis of patients with high-risk cytogenetic features while the prognosis of patients with EMD remains poor. Moreover, patients are likely to benefit from an earlier use of CAR T therapy and human-derived CAR T cells have obvious advantages based on the existing data.

Stratification for RRMM and Risk-Adapted Therapy: Sequencing of Therapies in RRMM

The treatment landscape for relapsed multiple myeloma (RRMM) has experienced an unprecedented wave of innovation. Implementation of numerous new substances and drug classes with different modes of action is made possible in routine clinical practice. Next generation proteasome inhibitors, monoclonal antibodies, as well as first in class agents such as selinexor and venetoclax have widened the therapeutic spectrum. This has led to an increase in progression-free and overall survival. Consequently, new challenges for treating physicians in choosing the right treatment at the right stage of the disease have been generated. Several trials support the use of novel agents in the frontline treatment of newly diagnosed multiple myeloma. The use of lenalidomide or bortezomib as a backbone in the first-line setting, requires strategies for treatment once these patients relapse and are refractory to these drugs. Despite the variety of options, selecting the optimal treatment strategy is difficult, since multiple factors have to be considered: patient-specific factors such as age and co-morbidities, as well as myeloma/tumor specific factors such as cytogenetics and relapse kinetics. This review intends to summarize the existing data and guidelines regarding the optimal sequencing of treatments of RRMM using already approved agents as well as agents under investigation.

A bispecific CAR-T cell therapy targeting BCMA and CD38 in relapsed or refractory multiple myeloma

Background

BCMA-specific chimeric antigen receptor-T cells (CAR-Ts) have exhibited remarkable efficacy in refractory or relapsed multiple myeloma (RRMM); however, primary resistance and relapse exist with single-target immunotherapy. Bispecific CARs are proposed to mitigate these limitations.

Methods

We constructed a humanized bispecific BM38 CAR targeting BCMA and CD38 and tested the antimyeloma activity of BM38 CAR-Ts in vitro and in vivo. Twenty-three patients with RRMM received infusions of BM38 CAR-Ts in a phase I trial.

Results

BM38 CAR-Ts showed stronger in vitro cytotoxicity to heterogeneous MM cells than did T cells expressing an individual BCMA or CD38 CAR. BM38 CAR-Ts also exhibited potent antimyeloma activity in xenograft mouse models. In the phase I trial, cytokine release syndrome occurred in 20 patients (87%) and was mostly grade 1–2 (65%). Neurotoxicity was not observed. Hematologic toxicities were common, including neutropenia in 96% of the patients, leukopenia in 87%, anemia in 43% and thrombocytopenia in 61%. At a median follow-up of 9.0 months (range 0.5 to 18.5), 20 patients (87%) attained a clinical response and minimal residual disease-negativity (≤ 10^–4 nucleated cells), with 12 (52%) achieving a stringent complete response. Extramedullary plasmacytoma was eliminated completely in 56% and partially in 33% and of 9 patients. The median progression-free survival was 17.2 months. Two relapsed patients maintained BCMA and CD38 expression on MM cells. Notably, BM38 CAR-Ts cells were detectable in 77.8% of evaluable patients at 9 months and 62.2% at 12 months.

Conclusion

Bispecific BM38 CAR-Ts were feasible, safe and significantly effective in patient with RRMM.

Trial registration: Chictr.org.cn ChiCTR1800018143.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-021-01170-7.

Anti-CD19 CAR T Cells That Secrete a Biparatopic Anti-CLEC12A Bridging Protein Have Potent Activity Against Highly Aggressive Acute Myeloid Leukemia In Vitro and In Vivo

Refractory acute myeloid leukemia (AML) remains an incurable malignancy despite the clinical use of novel targeted therapies, new antibody-based therapies, and cellular therapeutics. Here, we describe the preclinical development of a novel cell therapy that targets the antigen CLEC12A with a biparatopic bridging protein. Bridging proteins are designed as "CAR-T cell engagers," with a CAR-targeted protein fused to antigen binding domains derived from antibodies. Here, we created a CD19-anti-CLEC12A bridging protein that binds to CAR19 T cells and to the antigen CLEC12A. Biparatopic targeting increases the potency of bridging protein-mediated cytotoxicity by CAR19 T cells. Using CAR19 T cells that secrete the bridging protein we demonstrate potent activity against aggressive leukemic cell lines in vivo This CAR-engager platform is facile and modular, as illustrated by activity of a dual-antigen bridging protein targeting CLEC12A and CD33, designed to counter tumor heterogeneity and antigen escape, and created without the need for extensive CAR T-cell genetic engineering. CAR19 T cells provide an optimal cell therapy platform with well-understood inherent persistence and fitness characteristics.

Extramedullary disease in multiple myeloma

When clonal plasma cells grow at anatomic sites distant from the bone marrow or grows contiguous from osseous lesions that break through the cortical bone, it is referred to as extramedullary multiple myeloma (EMD). EMD remains challenging from a therapeutic and biological perspective. The pathogenetic mechanisms are not completely understood and it is generally associated with high-risk cytogenetics which portends poor outcomes. There is a rising incidence of EMD in the era of novel agents, likely a reflection of longer OS, with no standard treatment approach. Patients benefit from aggressive chemotherapy-based approaches, but the OS and prognosis remains poor. RT has been used for palliative care. There is a need for large prospective trials for development of treatment approaches for treatment of EMD.

The evolving status of immunotherapies in multiple myeloma: the future role of bispecific antibodies

Treatment outcomes in multiple myeloma (MM) have improved dramatically over the past 10 years. However, patients with high-risk disease such as those with Stage III disease by the Revised International Staging System, the presence of adverse cytogenetics, or who are refractory to proteosome inhibitors, immunomodulatory drugs and monoclonal antibodies may have dismal outcomes. These patients represent an urgent ongoing need in MM. One of the hallmarks of MM is immune dysfunction and a tumour-permissive immune microenvironment. Ameliorating the immune-paresis could lead to improved outcomes. The role of immunotherapies has been growing at an exponential pace with numerous agents under development in clinical trials. In the present review, we provide an overview of immunotherapies in MM, focussing on bispecific antibodies (BsAbs). We review efficacy outcomes from the published clinical trials and consider the important safety aspects of these therapies, in particular the risk of cytokine-release syndrome and immune effector cell-associated neurotoxicity syndrome, and how these compare with patients receiving chimeric antigen receptor T cells. We discuss the MM epitopes being targeted by BsAbs, either in clinical or preclinical stages, and we consider where these therapies might best fit within the future ever-changing paradigm of MM treatment.

Novel BCMA-OR-CD38 tandem-dual chimeric antigen receptor T cells robustly control multiple myeloma

BCMA-targeting chimeric antigen receptor (CAR)-T cell therapy has shown remarkable clinical efficacy against multiple myeloma, yet antigen escape and tumor relapse still occur after the use of these therapies. Designing CAR-T therapies that targets multiple antigens simultaneously seems a feasible way to avoid antigen escape, and it has been extensively studied elsewhere. Here, we report novel BCMA-OR-CD38 Tan CAR T cells that can trigger robust cytotoxicity against target cells expressing either BCMA or CD38. We demonstrate that, in in vitro studies, these BCMA-OR-CD38 Tan CAR T cells exhibit similar CAR expression, superior cytotoxicity and antigen-stimulated T cell proliferation as compared to single-targeted CAR T cells or CD38-OR-BCMA Tan CAR T cells. Importantly, these BCMA-OR-CD38 Tan CAR-T cells can achieve complete tumor clearance in myeloma-bearing mice with no relapse observed through the course of these experiments. Finally, this BCMA-OR-CD38 Tan CAR was fully compatible with existing clinical grade T cell manufacturing procedures and can be implemented using current clinical protocols. Taken together, our results present an effective solution to the challenge of antigen escape in BCMA CAR T-cell therapies.

Efficacy and Safety of CAR-T Cell Products Axicabtagene Ciloleucel, Tisagenlecleucel, and Lisocabtagene Maraleucel for the Treatment of Hematologic Malignancies: A Systematic Review and Meta-Analysis

Background

Currently, three chimeric antigen receptor (CAR)-T cell products axicabtagene ciloleucel, tisagenlecleucel, and lisocabtagene maraleucel have been approved by the U.S. Food and Drug Administration for the treatment of large B cell lymphoma, which provide a novel and promising choice for patients with relapsed or refractory to traditional anti-tumor treatments. Thus, it is pertinent to describe the efficacy and safety profile of the three products available by summarizing the current evidence.

Methods

Two reviewers independently searched the Embase, PubMed, Web of Science, and Cochrane Library, to identify studies related to the use of the three CAR-T cell products for treating hematologic malignancies published up to October 5, 2020. We pooled the overall response rate, complete response rate, cytokine release syndrome, and immune effector cell-associated neurotoxicity syndrome of three products, and then performed subgroup analysis based on the type of product and type of tumor.

Results

Thirty-three studies involving 2,172 patients were included in the analysis. All three products showed promising results in patients with different pathological subtypes and clinical characteristics that included those who did not meet the eligibility criteria of licensing trials, with overall response rates of nearly 70% or above and complete response rates of more than 50%. However, high rates of severe immune effector cell-associated neurotoxicity syndrome in patients undergoing axicabtagene ciloleucel treatment and life-threatening cytokine release syndrome in patients with leukemia undergoing tisagenlecleucel treatment required special attention in practice (31%; 95% CI: 0.27–0.35 and 55%; 95% CI: 0.45–0.64, respectively). Moreover, lisocabtagene maraleucel that showed a favorable efficacy and safety in the licensing trial lacked corresponding real-world data.

Conclusion

Both axicabtagene ciloleucel and tisagenlecleucel showed considerable efficacy in practice, but need special attention with respect to life-threatening toxicity that can occur in certain situations. Lisocabtagene maraleucel demonstrated excellent efficacy and safety profiles in the licensing trial, but lacked corresponding real-world data. Additional data on the three products are needed in rare histological subtypes to benefit a broader patient population.

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

Simple Summary

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

Abstract

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

[CAR T-cell therapy for multiple myeloma]

Die Behandlung mit CAR-T-Zellen (CAR chimärer Antigenrezeptor) ist eine neuartige Strategie der zellulären Immuntherapie, die das patienteneigene Immunsystem als „Waffe gegen Tumorzellen“ benutzt. Bei Patienten mit multiplem Myelom werden CAR-T-Zell-Therapien im Rahmen klinischer Studien getestet. Die aktuellen Studiendaten der gegen das „B-cell maturation antigen“ (BCMA) gerichteten CAR-T-Zell-Therapien zeigen eine beachtliche Wirksamkeit, die eine baldige Zulassung erwarten lässt. Allerdings erleiden weiterhin die meisten Patienten nach einer Behandlung mit CAR-T-Zellen ein Rezidiv. Hinzu kommt, dass CAR-T-Zell-Therapien zu schwerwiegenden Nebenwirkungen wie Zytokinfreisetzungssyndrom und Neurotoxizität mit teilweise auch letalem Ausgang führen können. Ein angemessenes Kosten-Nutzen-Verhältnis der CAR-T-Zell-Therapie stellt eine weitere Herausforderung dar. Trotz dieser Limitationen erscheint die CAR-T-Zell-Therapie eine attraktive Option für Patienten mit Myelom, sodass diese Therapie das Potenzial hat, in die Standardbehandlung integriert zu werden.

Therapeutic outcome of early-phase clinical trials in multiple myeloma: a meta-analysis

Great progress in the treatment of patients with multiple myeloma (MM) has been made due to the development of novel drugs. Patients with relapsed/refractory MM (RRMM) can be enrolled in early-phase clinical trials, but their performance across the last decade is unknown. We conducted a meta-analysis on the overall response rate (ORR) and toxicity. PubMed, Embase, and Cochrane Library were systematically searched for phase I and phase II trials investigating an experimental compound as a single agent or in combination with dexamethasone, published from January 1, 2010 to July 1, 2020. Eighty-eight articles were included, describing 61 phase I trials involving 1835 patients and 37 phase II trials involving 2644 patients. There was a high degree of heterogeneity. Using a random-effects model, the 95% CIs of the estimated ORR were 8-17% for phase I trials and 18-28% for phase II trials. There were significant subgroup differences in ORR between the years of publication in phase I trials and between drug classes in both phase I and phase II trials. The ORR in early-phase clinical trials in RRMM is substantial, especially in phase II trials, but due to high heterogeneity a general assessment of clinical benefit before participation is difficult to offer to patients.

Why Immunotherapy Fails in Multiple Myeloma

Multiple myeloma remains an incurable disease despite great advances in its therapeutic landscape. Increasing evidence supports the belief that immune dysfunction plays an important role in the disease pathogenesis, progression, and drug resistance. Recent efforts have focused on harnessing the immune system to exert anti-myeloma effects with encouraging outcomes. First-in-class anti-CD38 monoclonal antibody, daratumumab, now forms part of standard treatment regimens in relapsed and refractory settings and is shifting to front-line treatments. However, a non-negligible number of patients will progress and be triple refractory from the first line of treatment. Antibody-drug conjugates, bispecific antibodies, and chimeric antigen receptors (CAR) are being developed in a heavily pretreated setting with outstanding results. Belantamab mafodotin-blmf has already received approval and other anti-B-cell maturation antigen (BCMA) therapies (CARs and bispecific antibodies are expected to be integrated in therapeutic options against myeloma soon. Nonetheless, immunotherapy faces different challenges in terms of efficacy and safety, and manufacturing and economic drawbacks associated with such a line of therapy pose additional obstacles to broadening its use. In this review, we described the most important clinical data on immunotherapeutic agents, delineated the limitations that lie in immunotherapy, and provided potential insights to overcome such issues.

Safety and clinical efficacy of BCMA CAR-T-cell therapy in multiple myeloma

Background

B-cell maturation antigen (BCMA)-targeted chimeric antigen receptor (CAR)-T-cell therapy is an emerging treatment option for multiple myeloma. The aim of this systematic review and meta-analysis was to determine its safety and clinical activity and to identify factors influencing these outcomes.

Methods

We performed a database search using the terms “BCMA,” “CAR,” and “multiple myeloma” for clinical studies published between 01/01/2015 and 01/01/2020. The methodology is further detailed in PROSPERO (CRD42020125332).

Results

Twenty-three different CAR-T-cell products have been used so far in 640 patients. Cytokine release syndrome was observed in 80.3% (69.0–88.2); 10.5% (6.8–16.0) had neurotoxicity. A higher neurotoxicity rate was reported in studies that included more heavily pretreated patients: 19.1% (13.3–26.7; I² = 45%) versus 2.8% (1.3–6.1; I² = 0%) (p < 0.0001). The pooled overall response rate was 80.5% (73.5–85.9); complete responses (CR) were observed in 44.8% (35.3–54.6). A pooled CR rate of 71.9% (62.8–79.6; I² = 0%) was noted in studies using alpaca/llama-based constructs, whereas it was only 18.0% (6.5–41.1; I² = 67%) in studies that used retroviral vectors for CAR transduction. Median progression-free survival (PFS) was 12.2 (11.4–17.4) months, which compared favorably to the expected PFS of 1.9 (1.5–3.7) months (HR 0.14; p < 0.0001).

Conclusions

Although considerable toxicity was observed, BCMA-targeted CAR-T-cell therapy is highly efficacious even in advanced multiple myeloma. Subgroup analysis confirmed the anticipated inter-study heterogeneity and identified potential factors contributing to safety and efficacy. The results of this meta-analysis may assist the future design of CAR-T-cell studies and lead to optimized BCMA CAR-T-cell products.

[Quality assessment of CAR T-cell activity: Recommendations of the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

CAR T-cells are anti-cancer immunocellular therapy drugs that involve reprogramming the patient's T-cells using a transgene encoding a chimeric antigen receptor (CAR). Although CAR T-cells are cellular therapies, the organization for manufacturing and delivering these medicinal products is in many ways different from the one for hematopoietic cell grafts or donor lymphocyte infusions. The implementation of this innovative therapy is recent and requires close coordination between clinical teams, the therapeutic apheresis unit, the cell therapy unit, the pharmaceutical laboratory, and pharmacy. Apart from the regulatory texts, which are regularly modified, and the specific requirements of each pharmaceutical laboratory, there is currently no guide to help the centers initiating their activity and there is no specific indicator to assess the quality of the CAR T-cell activity in each center. The purpose of the current harmonization workshop is to clarify the regulatory prerequisites warranted for a center to have a CAR T-cell activity and to propose recommendations for implementing quality tools, in particular indicators, and allowing their sharing.

Rewriting History: Epigenetic Reprogramming of CD8+ T Cell Differentiation to Enhance Immunotherapy

The full potential of T cell-based immunotherapies remains limited by a variety of T cell extrinsic and intrinsic immunosuppressive mechanisms that can become imprinted to stably reduce the antitumor ability of T cells. Here, we discuss recent insights into memory CD8+ T cell differentiation and exhaustion and the association of these differentiation states with clinical outcomes during immune checkpoint blockade and chimeric antigen receptor (CAR) T cell therapeutic modalities. We consider the barriers limiting immunotherapy with a focus on epigenetic regulation impeding efficacy of adoptively transferred T cells and other approaches that augment T cell responses such as immune checkpoint blockade. Furthermore, we outline conceptual and technical breakthroughs that can be applied to existing therapeutic approaches and to the development of novel cutting-edge strategies.

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

Despite recent therapeutic advances, the prognosis of multiple myeloma (MM) patients remains poor. Thus, new strategies to improve outcomes are imperative. Chimeric antigen receptor (CAR) T-cell therapy has changed the treatment landscape of B-cell malignancies, providing a potentially curative option for patients who are refractory to standard treatment. Long-term remissions achieved in patients with acute lymphoblastic leukemia and Non-Hodgkin Lymphoma encouraged its further development in MM. B-cell maturation antigen (BCMA)-targeted CAR T-cells have established outstanding results in heavily pre-treated patients. However, several other antigens such as SLAMF7 and CD44v6 are currently under investigation with promising results. Idecabtagene vicleucel is expected to be approved soon for clinical use. Unfortunately, relapses after CAR T-cell infusion have been reported. Hence, understanding the underlying mechanisms of resistance is essential to promote prevention strategies and to enhance CAR T-cell efficacy. In this review we provide an update of the most recent clinical and pre-clinical data and we elucidate both, the potential and the challenges of CAR T-cell therapy in the future.

Development of CAR-T cell therapies for multiple myeloma

Currently available data on chimeric antigen receptor (CAR)-T cell therapy has demonstrated efficacy and manageable toxicity in heavily pretreated multiple myeloma (MM) patients. The CAR-T field in MM is rapidly evolving with >50 currently ongoing clinical trials across all phases, different CAR-T design, or targets. Most of the CAR-T trials are performed in China and the United States, while European centers organize or participate in only a small fraction of current clinical investigations. Autologous CAR-T cell therapy against B cell maturation antigen shows the best evidence of efficacy so far but main issues remain to be addressed: duration of response, longer follow-up, prolonged cytopenia, patients who may benefit the most such as those with extramedullary disease, outcome prediction, and the integration of CAR-T cell therapy within the MM treatment paradigm. Other promising targets are, i.a.,: CD38, SLAMF7/CS1, or GPRC5D. Although no product has been approved to date, cost and production time for autologous products are expected to be the main obstacles for broad use, for which reason allogeneic CAR-T cells are currently explored. However, the inherent risk of graft-versus-host disease requires additional modification which still need to be validated. This review aims to present the current status of CAR-T cell therapy in MM with an overview on current targets, designs, and stages of CAR-T cell development. Main challenges to CAR-T cell therapy will be highlighted as well as strategies to structurally improve the CAR-T cell product, and thereby its efficacy and safety. The need for comparability of the most promising therapies will be emphasized to balance risks and benefits in an evidence-based but personalized approach to further improve outcome of patients with MM.

BCMA-Targeting Therapy: Driving a New Era of Immunotherapy in Multiple Myeloma

The treatment of multiple myeloma (MM) has entered into a new era of immunotherapy. Novel immunotherapies will significantly improve patient outcome via simultaneously targeting malignant plasma cell (PC) and reversing immunocompromised bone marrow (BM) microenvironment. B-cell maturation antigen (BCMA), selectively expressed in PCs and a key receptor for A proliferation-inducing ligand (APRIL), is highly expressed in MM cells from patients at all stages. The APRIL/BCMA signal cascades promote the survival and drug resistance of MM cells and further modulate immunosuppressive BM milieu. Impressively, anti-BCMA immunotherapeutic reagents, including chimeric antigen receptor (CAR), antibody-drug conjugate (ADC) and bispecific T cell engager (BiTE) have all shown high response rates in their first clinical trials in relapse and refractory patients with very limited treatment options. These results rapidly inspired numerous development of next-generation anti-BCMA biotherapeutics, i.e., bispecific molecule, bispecific or trispecific antibodies, a novel form of CAR T/NK cells and T Cell Antigen Coupler (TAC) receptors, antibody-coupled T cell receptor (ACTR) as well as a cancer vaccine. We here highlight seminal preclinical and clinical studies on novel BCMA-based immunotherapies as effective monotherapy and discuss their potential in combination with current anti-MM and novel checkpoint drugs in earlier disease stages to further achieve durable responses in patients.

Paving the Way toward Successful Multiple Myeloma Treatment: Chimeric Antigen Receptor T-Cell Therapy

Despite the significant progress of modern anticancer therapies, multiple myeloma (MM) is still incurable for the majority of patients. Following almost three decades of development, chimeric antigen receptor (CAR) T-cell therapy now has the opportunity to revolutionize the treatment landscape and meet the unmet clinical need. However, there are still several major hurdles to overcome. Here we discuss the recent advances of CAR T-cell therapy for MM with an emphasis on future directions and possible risks. Currently, CAR T-cell therapy for MM is at the first stage of clinical studies, and most studies have focused on CAR T cells targeting B cell maturation antigen (BCMA), but other antigens such as cluster of differentiation 138 (CD138, syndecan-1) are also being evaluated. Although this therapy is associated with side effects, such as cytokine release syndrome and neurotoxicity, and relapses have been observed, the benefit–risk balance and huge potential drive the ongoing clinical progress. To fulfill the promise of recent clinical trial success and maximize the potential of CAR T, future efforts should focus on the reduction of side effects, novel targeted antigens, combinatorial uses of different types of CAR T, and development of CAR T cells targeting more than one antigen.