Chimeric Antigen Receptor-Modified T Cell Therapy in Multiple Myeloma: Beyond B Cell Maturation Antigen

CAR T therapies in multiple myeloma: unleashing the future

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

Exploring the efficacy and safety of anti-BCMA chimeric antigen receptor T-cell therapy for multiple myeloma: Systematic review and meta-analysis

Objective

Multiple myeloma (MM) is a bone marrow cancer that profoundly affects plasma cells involved in the immune response. Myeloma cells alter the average production of cells in the bone marrow. Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapy allows genetic modifications of an individual's T-cells to increase the expression of CARs used to identify and attach BCMA proteins to the malignant cells. Our main objective is to perform a systematic review and meta-analysis to explore the efficacy and safety of anti-BCMA CAR T-cell therapy for MM.

Material and Methods

We searched five databases, PubMed, CNKI, EMBASE, Cochrane, Web of Science, and CNKI, for studies published on anti-BCMA,CAR-T-cell treatment for MM. Inclusion criteria involved prospective single-arm studies either single or multi-center, in various MM phases and studies that reported anti-BCMA,CAR-T-cell treatment for MM. We excluded non-English publications and conference papers. All statistical analyses were performed in R software and Review Manager 5.4.1.

Results

Thirteen articles were included in the analysis. We found that the overall response survival complete response increase was statistically significant. Similarly, the reduction in cytokine release syndrome grades 3 and 4 and neurotoxicity after follow-up was statistically significant. However, the reduction in minimal residual disease negativity (MRDN) was not statistically significant.

Conclusion

Using anti-BCMA CAR T-cell therapy in MM was highly efficacious and safe in lowering the adverse outcomes and improving the survival outcomes, complete response, and overall response.

Transient acute kidney injury after chimeric antigen receptor T-cell therapy in patients with hematological malignancies

Background

Acute kidney injury (AKI) occurs in 30% of patients infused with chimeric antigen receptor (CAR) T-cells. The purpose of this study was to identify risk factors and long-term outcomes after AKI in patients who received CAR T-cell therapy.

Methods

Medical records of 115 adult patients with R/R hematological malignancies treated with CD19-targeted CAR T-cells at Vall d'Hebron University Hospital between July 2018 and May 2021. Baseline demographic data including age, gender, ethnicity, body mass index (BMI), and co-morbidities, as well as the type of hematological neoplasia and prior lines of therapy were collected. Laboratory parameters including serum creatinine and whole blood hemoglobin were retrospectively reviewed and values were gathered for days +1, +7, +14, +21, and +28 post-infusion.

Results

A total of 24/115 (21%) patients developed AKI related to CAR T-cell therapy; 6/24 with AKI over chronic kidney disease (CKD). Two patients had AKI in the context of lymphodepleting (LD) chemotherapy and the other 22 after CAR T-cell infusion, starting at day+1 in 3 patients, day+7 in 13 patients, day +14 in 1 patient, day+21 in 2 patients, and day+28 in 3 patients. Renal function was recovered in 19/24 (79%) patients within the first month after infusion. Male gender, CKD, cytokine release syndrome (CRS), and immune effector cell-associated neurotoxicity syndrome (ICANS) were associated with AKI. Male gender, CKD, ICANS grade ≥3 and CRS grade ≥2 were identified as independent risk factors for AKI on multivariable analysis. In terms of the most frequent CAR T-cell related complications, CRS was observed in 95 (82%) patients and ICANS in 33 (29%) patients. Steroids were required in 34 (30%) patients and tocilizumab in 37 (32%) patients. Six (5%) patients were admitted to the intensive care unit (1 for septic shock, 4 for CRS grade ≥2 associated to ICANS grade ≥2, and 1 for CRS grade ≥3). A total of 5 (4.4%) patients died in the first 30 days after CAR T-cell infusion for reasons other than disease progression, including 4 cases of infectious complications and 1 of heart failure.

Conclusion

Our results suggest that AKI is a frequent but mild adverse event, with fast recovery in most patients.

Advancements in CRISPR screens for the development of cancer immunotherapy strategies

CRISPR screen technology enables systematic and scalable interrogation of gene function by using the CRISPR-Cas9 system to perturb gene expression. In the field of cancer immunotherapy, this technology has empowered the discovery of genes, biomarkers, and pathways that regulate tumor development and progression, immune reactivity, and the effectiveness of immunotherapeutic interventions. By conducting large-scale genetic screens, researchers have successfully identified novel targets to impede tumor growth, enhance anti-tumor immune responses, and surmount immunosuppression within the tumor microenvironment (TME). Here, we present an overview of CRISPR screens conducted in tumor cells for the purpose of identifying novel therapeutic targets. We also explore the application of CRISPR screens in immune cells to propel the advancement of cell-based therapies, encompassing T cells, natural killer cells, dendritic cells, and macrophages. Furthermore, we outline the crucial components necessary for the successful implementation of immune-specific CRISPR screens and explore potential directions for future research.

Mechanisms of resistance to chimeric antigen receptor-T cells in haematological malignancies

Chimeric antigen receptor (CAR)-T cells have recently emerged as a powerful therapeutic approach for the treatment of patients with chemotherapy-refractory or relapsed blood cancers, including acute lymphoblastic leukaemia, diffuse large B cell lymphoma, follicular lymphoma, mantle cell lymphoma and multiple myeloma. Nevertheless, resistance to CAR-T cell therapies occurs in most patients. In this Review, we summarize the resistance mechanisms to CAR-T cell immunotherapy by analysing CAR-T cell dysfunction, intrinsic tumour resistance and the immunosuppressive tumour microenvironment. We discuss current research strategies to overcome multiple resistance mechanisms, including optimization of the CAR design, improvement of in vivo T cell function and persistence, modulation of the immunosuppressive tumour microenvironment and synergistic combination strategies.

CAR-T-Cell Therapy in Multiple Myeloma: B-Cell Maturation Antigen (BCMA) and Beyond

Significant progress has been achieved in the realm of therapeutic interventions for multiple myeloma (MM), leading to transformative shifts in its clinical management. While conventional modalities such as surgery, radiotherapy, and chemotherapy have improved the clinical outcomes, the overarching challenge of effecting a comprehensive cure for patients afflicted with relapsed and refractory MM (RRMM) endures. Notably, adoptive cellular therapy, especially chimeric antigen receptor T-cell (CAR-T) therapy, has exhibited efficacy in patients with refractory or resistant B-cell malignancies and is now also being tested in patients with MM. Within this context, the B-cell maturation antigen (BCMA) has emerged as a promising candidate for CAR-T-cell antigen targeting in MM. Alternative targets include SLAMF7, CD38, CD19, the signaling lymphocyte activation molecule CS1, NKG2D, and CD138. Numerous clinical studies have demonstrated the clinical efficacy of these CAR-T-cell therapies, although longitudinal follow-up reveals some degree of antigenic escape. The widespread implementation of CAR-T-cell therapy is encumbered by several barriers, including antigenic evasion, uneven intratumoral infiltration in solid cancers, cytokine release syndrome, neurotoxicity, logistical implementation, and financial burden. This article provides an overview of CAR-T-cell therapy in MM and the utilization of BCMA as the target antigen, as well as an overview of other potential target moieties.

Specific Targeting of Multiple Myeloma by Dual Split-signaling Chimeric Antigen Receptor T cells Directed against CD38 and CD138

PURPOSE

The success of B-cell maturation antigen (BCMA)-specific chimeric antigen receptor (CAR) T cells illustrates the potential of this novel therapy for multiple myeloma. Nonetheless, broadening CAR T-cell therapy beyond BCMA requires inventive strategies as there are only a few multiple myeloma- or plasma cell-specific target antigens. We investigated the feasibility of achieving multiple myeloma specificity by dual-split CD38/CD138 CAR targeting, whereby the stimulatory and costimulatory signals for T-cell activation are split into two separate stimulatory (sCAR) and costimulatory CARs (cCAR).

EXPERIMENTAL DESIGN

Using various combinations of CD38 and CD138 sCARs and cCARs with different affinities, we generated several dual-split CAR T cells and analyzed them for multiple myeloma-specific effector functions in vitro. The best-functioning CAR T cells were tested in vivo in a murine xenograft model.

RESULTS

We found optimal designs of both CD38sCAR/CD138cCAR and CD138sCAR/CD38cCAR combinations, that effectively lysed multiple myeloma cells but spared single CD38- or CD138-positive healthy hematopoietic cells. While the CD38sCAR/CD138cCAR T cells achieved multiple myeloma-specific activity solely due to the low affinity of the CD38sCARs, the multiple myeloma-specific cytotoxicity, cytokine release, and proliferation of CD138sCAR/CD38cCAR T cells were established through a true combinatorial stimulatory and costimulatory effect. The most optimal combination comprised a low-affinity CD138sCAR combined with a high-affinity CD38cCAR. These CD138sCAR/CD38cCAR T cells also showed dual-antigen specific anti-multiple myeloma effects in vivo. Importantly, they were also effective against multiple myeloma cells from daratumumab pretreated patients with decreased CD38 expression levels.

CONCLUSIONS

We demonstrate the possibility to specifically target multiple myeloma cells, even after CD38 targeted therapy, with carefully-designed dual-split CARs directed against CD38 and CD138.

Promising effects of exosomes from menstrual blood-derived mesenchymal stem cells on endometriosis

Endometriosis as a non-malignant gynecological disease leads to dysregulation of numerous cellular functions including apoptosis, angiogenesis, migration, proliferation, and inflammation. Accumulating evidence has shed light on the importance of endometrial stem cells within the menstrual blood which are involved in the establishment and progression of endometriotic lesions in a retrograde manner. According to the fact that the therapeutic benefits of mesenchymal stem cells are provided through paracrine functions, we used exosomes from menstrual blood-derived stem cells (MenSCs) for treating endometriotic stem cells to inhibit their lesion formation tendency. Menstrual blood samples from healthy and endometriosis women were collected. Isolated MenSCs by the density-gradient centrifugation method were characterized by flow cytometry. Secreted exosomes were isolated from healthy MenSCs (NE-MenSCs) and used to treat endometriotic cells (E-MenSCs). 72 h after treatment, different mechanisms and pathways including inflammation, proliferation, apoptosis, migration, and angiogenesis were analyzed using Real-Time PCR, ELISA, immunocytochemistry, annexin V/PI, and scratching assay. Exosome treatment significantly reduce the expression level of markers related to inflammation, proliferation, migration, and angiogenesis in E-MenSCs which are aberrantly expressed in endometriosis. Moreover, apoptosis was induced in E-MenSCs after treatment which was evaluated in both gene and protein levels. In this study, we give preliminary evidence for the potential of MenSCs-Exo in ameliorating endometriosis. Regarding our results, we suggest that after relevant clinical trial, MenSCs-derived exosomes can be considered as a better treatment option to improve endometriosis compared to common and conventional treatments and show their potential as a cell-free product in endometriosis repair.

Current progress in chimeric antigen receptor-modified T cells for the treatment of metastatic breast cancer

Breast cancer is the leading cancer in women. Around 20-30% breast cancer patients undergo invasion or metastasis after radical surgical resection and eventually die. Number of breast cancer patients show poor sensitivity toward treatments despite the advances in chemotherapy, endocrine therapy, and molecular targeted treatments. Therapeutic resistance and tumor recurrence or metastasis develop with the ongoing treatments. Conducive treatment strategies are thus required. Chimeric antigen receptor (CAR)-modified T-cell therapy has progressed as a part of tumor immunotherapy. However, CAR-T treatment has not been effective in solid tumors because of tumor microenvironment complexity, inhibitory effects of extracellular matrix, and lacking ideal tumor antigens. Herein, the prospects of CAR-T cell therapy for metastatic breast cancer are discussed, and the targets for CAR-T therapy in breast cancer (HER-2, C-MET, MSLN, CEA, MUC1, ROR1, EGFR) at clinical level are reviewed. Moreover, solutions are proposed for the challenges of breast cancer CAR-T therapy regarding off-target effects, heterogeneous antigen expression by tumor cells and immunosuppressive tumor microenvironment. Ideas for improving the therapeutics of CAR-T cell therapy in metastatic breast cancer are suggested.

Advancements and future trends of immunotherapy in light-chain amyloidosis

Light-chain (AL) amyloidosis is a type of plasma cell neoplasm with abnormal monoclonal immunoglobulin light-chain production and their subsequent deposition in tissues causing end-organ damage. In addition to existing treatments including autologous stem cell transplantation, there is a need for other approaches for eradicating abnormal plasma cells and amyloid tissue deposits. Treatment strategies of AL amyloidosis are mostly based on medications that are effective in multiple myeloma due to similar cell of origin. Daratumumab along with proteasome inhibitors and corticosteroids has become standard of care for AL amyloidosis. Another appealing approach is disassembling amyloid deposits with hope to potentially reverse the damage done by the disease. This was met with promising results for CAEL-101 and birtamimab. Although still in early stages, novel treatment options in pipeline, including antibody-drug conjugates, bispecific T-cell engagers, and chimeric antigen receptor T cell therapy may diversify the treatment armamentarium of AL amyloidosis in the future.

Pharmacy considerations: Use of anti-CD38 monoclonal antibodies in relapsed and/or refractory multiple myeloma

OBJECTIVE

This article reviews current evidence for the approved anti-CD38 monoclonal antibodies, isatuximab and daratumumab, for the treatment of patients with relapsed and/or refractory multiple myeloma (RRMM) and the implications for pharmacists.

DATA SOURCES

We conducted a literature search on PubMed/Medline and other sources using the drug names and the terms CD38, multiple myeloma, and pharmacists.

DATA SUMMARY

Monoclonal antibodies targeting the CD38 transmembrane glycoprotein offer a promising treatment approach for patients with RRMM. Isatuximab and daratumumab bind to different epitopes on CD38. In this review, we describe the similarities and differences in their mechanism of action, regulatory labeling, and the current guidelines for isatuximab and daratumumab use in RRMM. We review the current evidence for the efficacy and safety of these agents in combination with pomalidomide or carfilzomib and dexamethasone from the landmark phase 3 clinical trials that led to their approval. We discuss key differences in the eligibility criteria between the clinical trials, and differences in dosing, administration, available formulations, and pre- and post-infusion medications for the two agents. We outline recent data from pharmacoeconomic analyses comparing the cost-effectiveness of isatuximab-based regimens with that of daratumumab-based regimens. A brief overview of other anti-CD38 agents in the pipeline for the treatment of patients with RRMM is presented.

CONCLUSIONS

Given that pharmacists play an integral role in driving cost-effective use of drugs without compromising efficacy and safety for the end user, educating pharmacists on the key differences between isatuximab and daratumumab can guide the selection of the appropriate anti-CD38 antibody.

Targeting TGF-β signaling in the multiple myeloma microenvironment: Steering CARs and T cells in the right direction

Multiple myeloma (MM) remains a lethal hematologic cancer characterized by the expansion of transformed plasma cells within the permissive bone marrow (BM) milieu. The emergence of relapsed and/or refractory MM (RRMM) is provoked through clonal evolution of malignant plasma cells that harbor genomic, metabolic and proteomic perturbations. For most patients, relapsed disease remains a major cause of overall mortality. Transforming growth factors (TGFs) have pleiotropic effects that regulate myelomagenesis as well as the emergence of drug resistance. Moreover, TGF-β modulates numerous cell types present with the tumor microenvironment, including many immune cell types. While numerous agents have been FDA-approved over the past 2 decades and significantly expanded the treatment options available for MM patients, the molecular mechanisms responsible for drug resistance remain elusive. Multiple myeloma is uniformly preceded by a premalignant state, monoclonal gammopathy of unknown significance, and both conditions are associated with progressive deregulation in host immunity characterized by reduced T cell, natural killer (NK) cell and antigen-presenting dendritic cell (DC) activity. TGF-β promotes myelomagenesis as well as intrinsic drug resistance by repressing anti-myeloma immunity to promote tolerance, drug resistance and disease progression. Hence, repression of TGF-β signaling is a prerequisite to enhance the efficacy of current and future immunotherapeutics. Novel strategies that incorporate T cells that have been modified to express chimeric antigen receptor (CARs), T cell receptors (TCRs) and bispecific T cell engagers (BiTEs) offer promise to block TGF-β signaling, overcome chemoresistance and enhance anti-myeloma immunity. Here, we describe the effects of TGF-β signaling on immune cell effectors in the bone marrow and emerging strategies to overcome TGF-β-mediated myeloma growth, drug resistance and survival.

Treating Multiple Myeloma in the Context of the Bone Marrow Microenvironment

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

Recent findings on chimeric antigen receptor (CAR)-engineered immune cell therapy in solid tumors and hematological malignancies

Advancements in adoptive cell therapy over the last four decades have revealed various new therapeutic strategies, such as chimeric antigen receptors (CARs), which are dedicated immune cells that are engineered and administered to eliminate cancer cells. In this context, CAR T-cells have shown significant promise in the treatment of hematological malignancies. However, many obstacles limit the efficacy of CAR T-cell therapy in both solid tumors and hematological malignancies. Consequently, CAR-NK and CAR-M cell therapies have recently emerged as novel therapeutic options for addressing the challenges associated with CAR T-cell therapies. Currently, many CAR immune cell trials are underway in various human malignancies around the world to improve antitumor activity and reduce the toxicity of CAR immune cell therapy. This review will describe the comprehensive literature of recent findings on CAR immune cell therapy in a wide range of human malignancies, as well as the challenges that have emerged in recent years.

Ciltacabtagene autoleucel: The second anti-BCMA CAR T-cell therapeutic armamentarium of relapsed or refractory multiple myeloma

Ciltacabtagene autoleucel (also known as cilta-cel) is a chimeric antigen receptor (CAR) T-cell therapy that targets B-cell maturation antigen (BCMA) on the surface of cancer cells in B cell malignancies, such as multiple myeloma (MM). It is a second-generation CAR that is outfitted with an ectodomain comprising two BCMA-binding single chain variable fragment (ScFv) domains, a transmembrane domain, and an endodomain possessing CD3ζ and 4-1BB. Cilta-cel is an autologous, gene-edited CAR T-cell that is prepared by collecting and modifying the recipient’s T-cells to create a patient personalized treatment in the laboratory to be infused back. This CAR T-cell product exceptionally entails CARs with two BCMA-targeting single-domain antibodies that detect two epitopes of BCMA expressed on the malignant cells of MM. Cilta-cel is the current addition to the treatment armamentarium of relapsed or refractory (r/r) MM after its approval by the FDA on February 28, 2022, based on the results of the Phase 1b/2 CARTITUDE-1 study. It was the second approved anti-BCMA CAR T-cell product after idecabtagene vicleucel (ide-cel) to treat myeloma patients. It induces early, deep, and long-lasting responses with a tolerable safety profile in r/r MM. Cilta-cel-treated myeloma patients may potentially experience adverse effects ranging from mild to life-threatening, but they are mostly manageable toxicities. Besides, it has a consistent safety profile upon a longer follow-up of patients. Cilta-cel generally outperforms ide cel in terms of efficacy in MM, but shows comparable adverse events. This review highlights the current updates on cilta-cel efficacy, adverse events, comparison with ide-cel, and its future direction in the treatment of MM.

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.

Immunotherapy in AL Amyloidosis

OPINION STATEMENT

Light-chain amyloidosis is a rare disorder where a small clone of plasma cells is producing excess toxic light chains that deposit in various organs and cause dysfunction. Cardiac involvement is a major determinant of survival and rapid reduction of light chain is critical for recovery of organ function and overall survival. Immunotherapy targeting the clonal plasma cells and amyloid fibrils has emerged as a promising candidate. Daratumumab, both alone and in combinations with other anti-myeloma agents, is able to achieve deep hematologic responses and has greatly improved outcomes. Isatuximab, elotuzumab, and CAEL101 have also shown promising results and further studies are ongoing in the frontline as well as the relapsed/refractory setting. The frailty of AL patients and the relapsing/remitting nature of the disease present unique challenges, and the low toxicity of monoclonal antibodies makes them well-suited for these patients. Other immunotherapy agents including chimeric antigen receptor T cells, bispecific antibodies, and antibody-drug conjugates have altered the landscape in treatment of multiple myeloma, and are in the early phase of evaluation in patients with AL amyloidosis with results eagerly awaited.

Bispecific BCMA-CD3 Antibodies Block Multiple Myeloma Tumor Growth

BCMA antigen is overexpressed in multiple myeloma cells and has been shown to be a promising target for novel cellular and antibody therapeutics. The humanized BCMA (clone 4C8A) antibody that effectively targeted multiple myeloma in a CAR (chimeric antigen receptor) format was used for designing several formats of bispecific BCMA-CD3 antibodies. Several different designs of univalent and bivalent humanized BCMA-CD3 CrossMAB and BCMA-FAB-CD3 ScFv-Fc antibodies were tested for binding with BCMA-positive cells and T cells and for killing by real time cytotoxic activity and IFN-gamma secretion with CHO-BCMA target cells and with multiple myeloma MM1S and H929 cell lines. All BCMA-CD3 antibodies demonstrated specific binding by FACS to CHO-BCMA, multiple myeloma cells, and to T cells with affinity Kd in the nM range. All antibodies with T cells specifically killed CHO-BCMA and multiple myeloma cells in a dose-dependent manner. The BCMA-CD3 antibodies with T cells secreted IFN-gamma with EC50 in the nM range. In addition, three BCMA bispecific antibodies had high in vivo efficacy using an MM1S xenograft NSG mouse model. The data demonstrate the high efficacy of novel hBCMA-CD3 antibodies with multiple myeloma cells and provide a basis for future pre-clinical and clinical development.

An Ex Vivo 3D Tumor Microenvironment-Mimicry Culture to Study TAM Modulation of Cancer Immunotherapy

Tumor-associated macrophages (TAMs) accumulate in the solid tumor microenvironment (TME) and have been shown to promote tumor growth and dampen antitumor immune responses. TAM-mediated suppression of T-cell antitumor reactivity is considered to be a major obstacle for many immunotherapies, including immune checkpoint blockade and adoptive T/CAR-T-cell therapies. An ex vivo culture system closely mimicking the TME can greatly facilitate the study of cancer immunotherapies. Here, we report the development of a 3D TME-mimicry culture that is comprised of the three major components of a human TME, including human tumor cells, TAMs, and tumor antigen-specific T cells. This TME-mimicry culture can readout the TAM-mediated suppression of T-cell antitumor reactivity, and therefore can be used to study TAM modulation of T-cell-based cancer immunotherapy. As a proof-of-principle, the studies of a PD-1/PD-L1 blockade therapy and a MAO-A blockade therapy were performed and validated.

Combinatorial antigen targeting strategies for acute leukemia: application in myeloid malignancy

BACKGROUND AIMS

Efforts to safely and effectively treat acute myeloid leukemia (AML) by targeting a single leukemia-associated antigen with chimeric antigen receptor (CAR) T cells have met with limited success, due in part to heterogeneous expression of myeloid antigens. The authors hypothesized that T cells expressing CARs directed toward two different AML-associated antigens would eradicate tumors and prevent relapse.

METHODS

For co-transduction with the authors' previously optimized CLL-1 CAR currently in clinical study (NCT04219163), the authors generated two CARs targeting either CD123 or CD33. The authors then tested the anti-tumor activity of T cells expressing each of the three CARs either alone or after co-transduction. The authors analyzed CAR T-cell phenotype, expansion and transduction efficacy and assessed function by in vitro and in vivo activity against AML cell lines expressing high (MOLM-13: CD123 high, CD33 high, CLL-1 intermediate), intermediate (HL-60: CD123 low, CD33 intermediate, CLL-1 intermediate/high) or low (KG-1a: CD123 low, CD33 low, CLL-1 low) levels of the target antigens.

RESULTS

The in vitro benefit of dual expression was most evident when the target cell line expressed low antigen levels (KG-1a). Mechanistically, dual expression was associated with higher pCD3z levels in T cells compared with single CAR T cells on exposure to KG-1a (P < 0.0001). In vivo, combinatorial targeting with CD123 or CD33 and CLL-1 CAR T cells improved tumor control and animal survival for all lines (KG-1a, MOLM-13 and HL-60); no antigen escape was detected in residual tumors.

CONCLUSIONS

Overall, these findings demonstrate that combinatorial targeting of CD33 or CD123 and CLL-1 with CAR T cells can control growth of heterogeneous AML tumors.

A combination of humanized anti-BCMA and murine anti-CD38 CAR-T cell therapy in patients with relapsed or refractory multiple myeloma

Chimeric antigen receptor T (CAR-T) cells are a promising approach in hematopoietic malignancies. We evaluated the safety and efficacy of a combination of humanized anti-BCMA and murine anti-CD38 CAR-T cell therapy in patients with relapsed or refractory multiple myeloma (R/RMM). Twenty-two R/RMM patients, with a median age of 56 years and a median number of previous therapies of 8, were included in the study. Both CAR-T cells infusion doses were 2.0 × 10⁶/kg. The overall response rate (ORR) was 90.9%, with 12 patients (54.5%) achieving a strict complete response/complete response (sCR/CR). The 24-month overall survival (OS) rate was 56.6%, and the progression-free survival (PFS) rate was 48.7%. Cytokine release syndrome (CRS) of grades 1-2 occurred in 16 patients (72.7%) and of grade ≥3 in six patients (27.3%). Immune effector cell-associated neurotoxic syndrome (ICANS) of grades 1-2 occurred in three patients (13.6%). The combination therapy is potential in R/RMM patients.Trial registration: The patients were enrolled in clinical trials registered as ChiCTR1800017051.

A BAFF ligand-based CAR-T cell targeting three receptors and multiple B cell cancers

B cell-activating factor (BAFF) binds the three receptors BAFF-R, BCMA, and TACI, predominantly expressed on mature B cells. Almost all B cell cancers are reported to express at least one of these receptors. Here we develop a BAFF ligand-based chimeric antigen receptor (CAR) and generate BAFF CAR-T cells using a non-viral gene delivery method. We show that BAFF CAR-T cells bind specifically to each of the three BAFF receptors and are effective at killing multiple B cell cancers, including mantle cell lymphoma (MCL), multiple myeloma (MM), and acute lymphoblastic leukemia (ALL), in vitro and in vivo using different xenograft models. Co-culture of BAFF CAR-T cells with these tumor cells results in induction of activation marker CD69, degranulation marker CD107a, and multiple proinflammatory cytokines. In summary, we report a ligand-based BAFF CAR-T capable of binding three different receptors, minimizing the potential for antigen escape in the treatment of B cell cancers.

Adoptive T-cell Immunotherapy: Perfecting Self-Defenses

As an important part of the immune system, T lymphocytes exhibit undoubtedly an important role in targeting and eradicating cancer. However, despite these characteristics, their natural antitumor response may be insufficient. Numerous clinical trials in terminally ill cancer patients testing the design of novel and efficient immunotherapeutic approaches based on the adoptive transfer of autologous tumor-specific T lymphocytes have shown encouraging results. Moreover, this also led to the approval of engineered T-cell therapies in patients. Herein, we will expand on the development and the use of such strategies using tumor-infiltrating lymphocytes or genetically engineered T-cells. We will also comment on the requirements and potential hurdles encountered when elaborating and implementing such treatments as well as the exciting prospects for this kind of emerging personalized medicine therapy.

Early Dynamics and Depth of Response in Multiple Myeloma Patients Treated With BCMA CAR-T Cells

Chimeric antigen receptor T-cell (CAR-T) therapy targeted against B-cell maturation antigen (BCMA) in multiple myeloma (MM) has produced rapid responses but many eventually relapse. In light of this new treatment, novel predictors of progression-free survival (PFS) are needed. We performed a single institution analysis of 54 BCMA-CAR-T patients. We analyzed patient’s overall response rate (ORR) by the IMWG criteria, involved serum-free light chains (iFLC), and minimal residual disease testing by next-generation sequencing (MRD-NGS). Between patients who achieved a ≤SD and those who achieved a ≥PR, PFS differed significantly (p < 0.0001); though there was no difference between patients who achieved a ≥CR vs. VGPR/PR (p = 0.2). In contrast, patients who achieved a nonelevated iFLC at 15 days (p < 0.0001, HR = 6.8; 95% CI, 2.7–17.3) or 30 days (p < 0.001, HR = 16.7; 95% CI, 3.9–71.7) had a prolonged PFS compared with those with an elevated iFLC. Patients achieving MRD-NGS less than the detectable limit at a sensitivity of 10⁻⁶ had a better PFS than those with detectable disease at 1 month (p = 0.02) and 3 months (p = 0.02). In conclusion, achieving a nonelevated iFLC and an undetectable MRD-NGS quickly were factors that were strongly associated with improved PFS. Further studies are needed to confirm the role of these markers in MM patients receiving CAR-T therapies.

Development of allogeneic HSC-engineered iNKT cells for off-the-shelf cancer immunotherapy

Cell-based immunotherapy has become the new-generation cancer medicine, and "off-the-shelf" cell products that can be manufactured at large scale and distributed readily to treat patients are necessary. Invariant natural killer T (iNKT) cells are ideal cell carriers for developing allogeneic cell therapy because they are powerful immune cells targeting cancers without graft-versus-host disease (GvHD) risk. However, healthy donor blood contains extremely low numbers of endogenous iNKT cells. Here, by combining hematopoietic stem cell (HSC) gene engineering and in vitro differentiation, we generate human allogeneic HSC-engineered iNKT (AlloHSC-iNKT) cells at high yield and purity; these cells closely resemble endogenous iNKT cells, effectively target tumor cells using multiple mechanisms, and exhibit high safety and low immunogenicity. These cells can be further engineered with chimeric antigen receptor (CAR) to enhance tumor targeting or/and gene edited to ablate surface human leukocyte antigen (HLA) molecules and further reduce immunogenicity. Collectively, these preclinical studies demonstrate the feasibility and cancer therapy potential of AlloHSC-iNKT cell products and lay a foundation for their translational and clinical development.

Emerging Approaches for Solid Tumor Treatment Using CAR-T Cell Therapy

Cancer immunotherapy is becoming more important in the clinical setting, especially for cancers resistant to conventional chemotherapy, including targeted therapy. Chimeric antigen receptor (CAR)-T cell therapy, which uses patient’s autologous T cells, combined with engineered T cell receptors, has shown remarkable results, with five US Food and Drug Administration (FDA) approvals to date. CAR-T cells have been very effective in hematologic malignancies, such as diffuse large B cell lymphoma (DLBCL), B cell acute lymphoblastic leukemia (B-ALL), and multiple myeloma (MM); however, its effectiveness in treating solid tumors has not been evaluated clearly. Therefore, many studies and clinical investigations are emerging to improve the CAR-T cell efficacy in solid tumors. The novel therapeutic approaches include modifying CARs in multiple ways or developing a combination therapy with immune checkpoint inhibitors and chemotherapies. In this review, we focus on the challenges and recent advancements in CAR-T cell therapy for solid tumors.

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.

Treatment Strategy for Multiple Myeloma to Improve Immunological Environment and Maintain MRD Negativity

Improving the immunological environment and eradicating minimal residual disease (MRD) are the two main treatment goals for long-term survival in patients with multiple myeloma (MM). Immunomodulatory drugs (IMiDs), monoclonal antibody drugs (MoAbs), and autologous grafts for autologous stem cell transplantation (ASCT) can improve the immunological microenvironment. ASCT, MoAbs, and proteasome inhibitors (PIs) may be important for the achievement of MRD negativity. An improved immunological environment may be useful for maintaining MRD negativity, although the specific treatment for persistent MRD negativity is unknown. However, whether the ongoing treatment should be continued or changed if the MRD status remains positive is controversial. In this case, genetic, immunophenotypic, and clinical analysis of residual myeloma cells may be necessary to select the effective treatment for the residual myeloma cells. The purpose of this review is to discuss the MM treatment strategy to "cure MM" based on currently available therapies, including IMiDs, PIs, MoAbs, and ASCT, and expected immunotherapies, such as chimeric antigen receptor T cell (CAR-T) therapy, via improvement of the immunological environment and maintenance of MRD negativity.

Chimeric Antigen Receptor T-Cell Therapeutics for Multiple Myeloma: Moving Into the Spotlight

ABSTRACT

Chimeric antigen receptor (CAR) T-cell therapy has quickly emerged as a highly promising treatment for patients with relapsed and refractory multiple myeloma. There are numerous candidates under development, each with their unique characteristics and points of differentiation. The most recent US Food and Drug Administration approval of the first B-cell maturation antigen-targeted CAR-T cell therapy on March 26, 2021, has paved a path forward for the eventual evaluation of more of these investigational agents undergoing clinical trials. Herein, we highlight, from a clinical development perspective, the CAR-T cell therapies farthest along in development with updated data from the American Society of Hematology 2020 annual meeting. We also discuss potential paths of overcoming resistance to these therapies and the future direction for CAR-T cell therapeutics in multiple myeloma.

The Agony of Choice-Where to Place the Wave of BCMA-Targeted Therapies in the Multiple Myeloma Treatment Puzzle in 2022 and Beyond

Simple Summary

There is no doubt that immunotherapeutic approaches will change the current treatment landscape of multiple myeloma in the near future; in particular, a wave of BCMA-targeted therapies is currently entering clinical routine. Although the increasing availability of different therapeutic approaches is highly welcome, it also increases the daily challenges in clinical decision making if they all use the same target. Here, we provide a comprehensive summary of BCMA-targeted approaches in myeloma and aim to share some basic concepts in clinical decision making.

Abstract

Since the introduction of first-generation proteasome inhibitors and immunomodulatory agents, the multiple myeloma (MM) treatment landscape has undergone a remarkable development. Most recently, immunotherapeutic strategies targeting the B cell maturation antigen (BCMA) entered the clinical stage providing access to highly anticipated novel treatment strategies. At present, numerous different approaches investigate BCMA as an effective multi-modal target. Currently, BCMA-directed antibody–drug conjugates, bispecific and trispecific antibodies, autologous and allogeneic CAR-T cell as well as CAR-NK cell constructs are either approved or in different stages of clinical and preclinical development for the treatment of MM. This armamentarium of treatment choices raises several challenges for clinical decision making, particularly in the absence of head-to-head comparisons. In this review, we provide a comprehensive overview of BCMA-targeting therapeutics, deliver latest updates on clinical trial data, and focus on potential patient selection criteria for different BCMA-targeting immunotherapeutic strategies.

Immunotherapy of Multiple Myeloma: Promise and Challenges

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

Trial Watch: Adoptive TCR-Engineered T-Cell Immunotherapy for Acute Myeloid Leukemia

Simple Summary

Acute myeloid leukemia (AML) is a type of blood cancer with an extremely grim prognosis. This is due to the fact that the majority of patients will relapse after frontline treatment. Overall survival of relapsed AML is very low, and treatment options are few. T lymphocytes harnessed with antitumor T-cell receptors (TCRs) can produce objective clinical responses in certain cancers, such as melanoma, but have not entered the main road for AML. In this review, we describe the current status of the field of TCR-T-cell therapies for AML.

Abstract

Despite the advent of novel therapies, acute myeloid leukemia (AML) remains associated with a grim prognosis. This is exemplified by 5-year overall survival rates not exceeding 30%. Even with frontline high-intensity chemotherapy regimens and allogeneic hematopoietic stem cell transplantation, the majority of patients with AML will relapse. For these patients, treatment options are few, and novel therapies are urgently needed. Adoptive T-cell therapies represent an attractive therapeutic avenue due to the intrinsic ability of T lymphocytes to recognize tumor cells with high specificity and efficiency. In particular, T-cell therapies focused on introducing T-cell receptors (TCRs) against tumor antigens have achieved objective clinical responses in solid tumors such as synovial sarcoma and melanoma. However, contrary to chimeric antigen receptor (CAR)-T cells with groundbreaking results in B-cell malignancies, the use of TCR-T cells for hematological malignancies is still in its infancy. In this review, we provide an overview of the status and clinical advances in adoptive TCR-T-cell therapy for the treatment of AML.

Bone Marrow Microenvironment Interplay and Current Clinical Practice in Multiple Myeloma: A Review of the Balkan Myeloma Study Group

The course of multiple myeloma (MM) is influenced by a variety of factors, including the specificity of the tumour microenvironment (TME). The aim of this review is to provide insight into the interplay of treatment modalities used in the current clinical practice and TME. Bortezomib-based triplets are the standard for MM first-line treatment. Bortezomib is a proteasome inhibitor (PI) which inhibits the nuclear factor kappa B (NF-κB) pathway. However, bortezomib is decreasing the expression of chemokine receptor CXCR4 as well, possibly leading to the escape of extramedullary disease. Immunomodulatory drugs (IMiDs), lenalidomide, and pomalidomide downregulate regulatory T cells (Tregs). Daratumumab, anti-cluster of differentiation 38 (anti-CD38) monoclonal antibody (MoAb), downregulates Tregs CD38+. Bisphosphonates inhibit osteoclasts and angiogenesis. Sustained suppression of bone resorption characterises the activity of MoAb denosumab. The plerixafor, used in the process of stem cell mobilisation and harvesting, block the interaction of chemokine receptors CXCR4-CXCL12, leading to disruption of MM cells’ interaction with the TME, and mobilisation into the circulation. The introduction of several T-cell-based immunotherapeutic modalities, such as chimeric-antigen-receptor-transduced T cells (CAR T cells) and bispecific antibodies, represents a new perspective in MM treatment affecting TME immune evasion. The optimal treatment approach to MM patients should be adjusted to all aspects of the individual profile including the TME niche.

Emerging therapies for relapsed/refractory multiple myeloma: CAR-T and beyond

The pace of innovation of multiple myeloma therapy in recent years is remarkable with the advent of monoclonal antibodies and the approval of novel agents with new mechanisms of action. Emerging therapies are on the horizon for clinical approval with significant implications in extending patient survival and advancing closer to the goal of a cure, especially in areas of immunotherapy such as chimeric antigen receptor T cells, bispecific T cell engager antibodies, antibody drug conjugates, newer generations of monoclonal antibodies, and small molecule inhibitor and modulators. This review provides an update of current myeloma therapeutics in active preclinical and early clinical development and discusses the mechanism of action of several classes of novel therapeutics.

Chimeric Antigen Receptor T Cell Therapy and Its Significance in Multiple Myeloma

Multiple myeloma (MM) has a five-year prevalence worldwide of 230,000 people and is known as the second most common hematological malignancy within the United States. Extensive research has been conducted to gain a wide range of treatment strategies, providing hope to these patients. Combination therapy using chemotherapy, monoclonal antibodies, and immunomodulatory drugs are the current management of choice. After the introduction of chimeric antigen receptor (CAR) T cell therapy, promising results have been evidenced. In this therapy, T cells are derived from the patient and modified in-vitro to induce receptors that later target specific antigens when they are injected into patients. CAR T cells use three mechanisms to kill tumor cells: cytolytic pathways, cytokine release, and Fas/FasL axis. In this review, we highlight the different tumor markers targeted for therapy against multiple myeloma (MM). Target antigens for CAR T cell therapy include B-cell maturation antigen (BCMA), signaling lymphocyte activation molecule F7 (SLAMF7), CD38, CD138, CD19, immunoglobulin kappa light chain, orphan G protein-coupled receptor class C group 5 member D (GPRC5D). With the benefit of improving survival and prognosis, this therapy does carry a risk of some adverse events such as cytokine release syndrome, encephalopathy, infections, hypogammaglobulinemia, and tumor lysis syndrome.

CART-Cell Therapy: Recent Advances and New Evidence in Multiple Myeloma

Despite the improvement in survival outcomes, multiple myeloma (MM) remains an incurable disease. Chimeric antigen receptor (CAR) T-cell therapy targeting B-cell maturation antigen (BCMA) represents a new strategy for the treatment of relapsed/refractory MM (R/R). In this paper, we describe several recent advances in the field of anti-BCMA CAR T-cell therapy and MM. Currently, available data on anti-BCMA CART-cell therapy has demonstrated efficacy and manageable toxicity in heavily pretreated R/R MM patients. Despite this, the main issues remain to be addressed. First of all, a significant proportion of patients eventually relapse. The potential strategy to prevent relapse includes sequential or combined infusion with CAR T-cells against targets other than BCMA, CAR T-cells with novel dual-targeting vector design, and BCMA expression upregulation. Another dark side of CART therapy is safety. Cytokine release syndrome (CRS) andneurologic toxicity are well-described adverse effects. In the MM trials, most CRS events tended to be grade 1 or 2, with fewer patients experiencing grade 3 or higher. Another critical point is the extended timeline of the manufacturing process. Allo-CARs offers the potential for scalable manufacturing for on-demand treatment with shorter waiting days. Another issue is undoubtedly going to be access to this therapy. Currently, only a few academic centers can perform these procedures. Recognizing these issues, the excellent response with BCMA-targeted CAR T-cell therapy makes it a treatment strategy of great promise.

How metabolism bridles cytotoxic CD8+ T cells through epigenetic modifications

In the direct competition for metabolic resources between cancer cells and tumor-infiltrating CD8+ T cells, the latter are bound to lose out. These effector lymphocytes are therefore rendered exhausted or dysfunctional. Emerging insights into the mechanisms of T cell unresponsiveness in the tumor microenvironment (TME) point towards epigenetic mechanisms as crucial regulatory factors. In this review, we discuss the effects of characteristic components of the TME, i.e. glucose/amino acid dearth with elevated levels of reactive oxygen species (ROS), on DNA methylation and histone modifications in CD8+ T cells. We then take a closer look at the translational potential of epigenetic interventions that aim to improve current immunotherapeutic strategies, including the adoptive transfer of T cell receptor (TCR) or chimeric antigen receptor (CAR) engineered T cells.

CAR T-cell therapy in multiple myeloma: more room for improvement

The emergence of various novel therapies over the last decade has changed the therapeutic landscape for multiple myeloma. While the clinical outcomes have improved significantly, the disease remains incurable, typically in patients with relapsed and refractory disease. Chimeric antigen receptor (CAR) T-cell therapies have achieved remarkable clinical success in B-cell malignancies. This scope of research has more recently been extended to the field of myeloma. While B-cell maturation antigen (BCMA) is currently the most well-studied CAR T antigen target in this disease, many other antigens are also undergoing intensive investigations. Some studies have shown encouraging results, whereas some others have demonstrated unfavorable results due to reasons such as toxicity and lack of clinical efficacy. Herein, we provide an overview of CAR T-cell therapies in myeloma, highlighted what has been achieved over the past decade, including the latest updates from ASH 2020 and discussed some of the challenges faced. Considering the current hits and misses of CAR T therapies, we provide a comprehensive analysis on the current manufacturing technologies, and deliberate on the future of CAR T-cell domain in MM.

Tumor Microenvironment Proteomics: Lessons From Multiple Myeloma

Although the "seed and soil" hypothesis was proposed by Stephen Paget at the end of the 19th century, where he postulated that tumor cells (seeds) need a propitious medium (soil) to be able to establish metastases, only recently the tumor microenvironment started to be more studied in the field of Oncology. Multiple myeloma (MM), a malignancy of plasma cells, can be considered one of the types of cancers where there is more evidence in the literature of the central role that the bone marrow (BM) microenvironment plays, contributing to proliferation, survival, migration, and drug resistance of tumor cells. Despite all advances in the therapeutic arsenal for MM treatment in the last years, the disease remains incurable. Thus, studies aiming a better understanding of the pathophysiology of the disease, as well as searching for new therapeutic targets are necessary and welcome. Therefore, the present study aimed to evaluate the protein expression profiling of mononuclear cells derived from BM of MM patients in comparison with these same cell types derived from healthy individuals, in order to fill this gap in MM treatment. Proteomic analysis was performed using the mass spectrometry technique and further analyses were done using bioinformatics tools, to identify dysregulated biological pathways and/or processes in the BM microenvironment of patients with MM as a result of the disease. Among the pathways identified in this study, we can highlight an upregulation of proteins related to protein biosynthesis, especially chaperone proteins, in patients with MM. Additionally, we also found an upregulation of several proteins involved in energy metabolism, which is one of the cancer hallmarks. Finally, with regard to the downregulated proteins, we can highlight mainly those involved in different pathways of the immune response, corroborating the data that has demonstrated that the immune system of MM is impaired and, therefore, the immunotherapies that have been studied recently for the treatment of the disease are extremely necessary in the search for a control and a cure for these patients who live with the disease.

Anti-CD19 CAR T cells potently redirected to kill solid tumor cells

Successful CAR T cell therapy for the treatment of solid tumors requires exemplary CAR T cell expansion, persistence and fitness, and the ability to target tumor antigens safely. Here we address this constellation of critical attributes for successful cellular therapy by using integrated technologies that simplify development and derisk clinical translation. We have developed a CAR-CD19 T cell that secretes a CD19-anti-Her2 bridging protein. This cell therapy strategy exploits the ability of CD19-targeting CAR T cells to interact with CD19 on normal B cells to drive expansion, persistence and fitness. The secreted bridging protein potently binds to Her2-positive tumor cells, mediating CAR-CD19 T cell cytotoxicity in vitro and in vivo. Because of its short half-life, the secreted bridging protein will selectively accumulate at the site of highest antigen expression, ie. at the tumor. Bridging proteins that bind to multiple different tumor antigens have been created. Therefore, antigen-bridging CAR-CD19 T cells incorporate critical attributes for successful solid tumor cell therapy. This platform can be exploited to attack tumor antigens on any cancer.

Perspectives for the Use of CAR-T Cells for the Treatment of Multiple Myeloma

During recent years considerable progress has been made in the treatment of multiple myeloma. However, despite the current improvements in the prognosis of this malignancy, it always ends with relapse, and therefore new therapy approaches for destroying resistant cancer cells are needed. Presently, there is great hope being placed in the use of immunotherapy against refractory/relapsed multiple myeloma which is unresponsive to any other currently known drugs. The most promising one is CAR-T cell therapy which has already shown tremendous success in treating other malignancies such as acute lymphoblastic leukaemia (ALL) and could potentially be administered to multiple myeloma patients. CAR-T cells equipped with receptors against BCMA (B-cell maturation antigen), which is a surface antigen that is highly expressed on malignant cells, are now of great interest in this field with significant results in clinical trials. Furthermore, CAR-T cells with other receptors and combinations of different strategies are being intensively studied. However, even with CAR-T cell therapy, the majority of patients eventually relapse, which is the greatest limitation of this therapy. Serious adverse events such as cytokine release syndrome or neurotoxicity should also be considered as possible side effects of CAR-T cell therapy. Here, we discuss the results of CAR-T cell therapy in the treatment of multiple myeloma, where we describe its main advantages and disadvantages. Additionally, we also describe the current results that have been obtained on using combinations of CAR-T cell therapies with other drugs for the treatment of multiple myeloma.

Game of Bones: How Myeloma Manipulates Its Microenvironment

Multiple myeloma is a clonal disease of long-lived plasma cells and is the second most common hematological cancer behind Non-Hodgkin’s Lymphoma. Malignant transformation of plasma cells imparts the ability to proliferate, causing harmful lesions in patients. In advanced stages myeloma cells become independent of their bone marrow microenvironment and form extramedullary disease. Plasma cells depend on a rich array of signals from neighboring cells within the bone marrow for survival which myeloma cells exploit for growth and proliferation. Recent evidence suggests, however, that both the myeloma cells and the microenvironment have undergone alterations as early as during precursor stages of the disease. There are no current therapies routinely used for treating myeloma in early stages, and while recent therapeutic efforts have improved patients’ median survival, most will eventually relapse. This is due to mutations in myeloma cells that not only allow them to utilize its bone marrow niche but also facilitate autocrine pro-survival signaling loops for further progression. This review will discuss the stages of myeloma cell progression and how myeloma cells progress within and outside of the bone marrow microenvironment.

Toxicities of Chimeric Antigen Receptor T Cell Therapy in Multiple Myeloma: An Overview of Experience From Clinical Trials, Pathophysiology, and Management Strategies

In the last few years, monoclonal antibodies (mAbs) such as elotuzumab and daratutumab have brought the treatment of multiple myeloma (MM) into the new era of immunotherapy. More recently, chimeric antigen receptor (CAR) modified T cell, a novel cellular immunotherapy, has been developed for treatment of relapsed/refractory (RR) MM, and early phase clinical trials have shown promising efficacy of CAR T cell therapy. Many patients with end stage RRMM regard CAR T cell therapy as their “last chance” and a “hope of cure”. However, severe adverse events (AEs) and even toxic death related to CAR T cell therapy have been observed. The management of AEs related to CAR T cell therapy represents a new challenge, as the pathophysiology is not fully understood and there is still no well-established standard of management. With regard to CAR T cell associated toxicities in MM, in this review, we will provide an overview of experience from clinical trials, pathophysiology, and management strategies.

Future of CAR T cells in multiple myeloma

Despite the significant improvement in survival outcomes of multiple myeloma (MM) over the past decade, it remains an incurable disease. Patients with triple-class refractory MM have limited treatment options and a dismal prognosis. Chimeric antigen receptor (CAR) T-cell therapy targeting B-cell maturation antigen has transformed the treatment armamentarium of relapsed/refractory MM (RRMM), with unprecedented overall response rates in this difficult-to-treat patient population. However, a significant proportion of patients ultimately relapse despite achieving deep remission. Several innovative approaches, including alternative/dual-antigen-specific CAR T-cell constructs, genetically engineered "off-the-shelf" CAR T cells, and strategies to counteract an immunosuppressive microenvironment, may dramatically reshape the field of CAR T-cell therapy in the future. These strategies are being actively investigated in preclinical and early clinical trial settings with the hopes of enhancing the durability of responses and, thereby, improving the overall survival of RRMM patients after CAR T-cell therapy.

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.

Treatment of Multiple Myeloma Using Chimeric Antigen Receptor T Cells with Dual Specificity

Chimeric antigen receptor (CAR) T-cell therapy has shown remarkable successes in fighting B-cell leukemias/lymphomas. Promising response rates are reported in patients treated with B-cell maturation antigen (BCMA) CAR T cells for multiple myeloma. However, responses appear to be nondurable, highlighting the need to expand the repertoire of multiple myeloma-specific targets for immunotherapy and to generate new CAR T cells. Here, we developed a "dual-CAR" targeting two multiple myeloma-associated antigens and explored its safety and efficacy. To reduce the "off-target" toxicity, we used the recognition of paired antigens that were coexpressed by the tumor to induce efficient CAR T-cell activation. The dual-CAR construct presented here was carefully designed to target the multiple myeloma-associated antigens, taking into consideration the distribution of both antigens on normal human tissues. Our results showed that the CD138/CD38-targeted dual CAR (dCAR138-38) elicited a potent anti-multiple myeloma response both in vitro and in vivo NSG mice transplanted with a multiple myeloma cell line and treated with dCAR138-38 showed median survival of 97 days compared with 31 days in the control group treated with mock-lymphocytes. The dCAR138-38 showed increased specificity toward cells expressing both targeted antigens compared with single-antigen-expressing cells and low activity toward primary cells from healthy tissues. Our findings indicated that the dCAR138-38 may provide a potent and safe alternative therapy for patients with multiple myeloma.

BCMA-targeted immunotherapy for multiple myeloma

B cell maturation antigen (BCMA) is a novel treatment target for multiple myeloma (MM) due to its highly selective expression in malignant plasma cells (PCs). Multiple BCMA-targeted therapeutics, including antibody-drug conjugates (ADC), chimeric antigen receptor (CAR)-T cells, and bispecific T cell engagers (BiTE), have achieved remarkable clinical response in patients with relapsed and refractory MM. Belantamab mafodotin-blmf (GSK2857916), a BCMA-targeted ADC, has just been approved for highly refractory MM. In this article, we summarized the molecular and physiological properties of BCMA as well as BCMA-targeted immunotherapeutic agents in different stages of clinical development.

The Role of Immunological Synapse in Predicting the Efficacy of Chimeric Antigen Receptor (CAR) Immunotherapy

Abstract

Chimeric Antigen Receptor (CAR) immunotherapy utilizes genetically-engineered immune cells that express a unique cell surface receptor that combines tumor antigen specificity with immune cell activation. In recent clinical trials, the adoptive transfer of CAR-modified immune cells (including CAR-T and CAR-NK cells) into patients has been remarkably successful in treating multiple refractory blood cancers. To improve safety and efficacy, and expand potential applicability to other cancer types, CARs with different target specificities and sequence modifications are being developed and tested by many laboratories. Despite the overall progress in CAR immunotherapy, conventional tools to design and evaluate the efficacy and safety of CAR immunotherapies can be inaccurate, time-consuming, costly, and labor-intensive. Furthermore, existing tools cannot always determine how responsive individual patients will be to a particular CAR immunotherapy. Recent work in our laboratory suggests that the quality of the immunological synapse (IS) can accurately predict CAR-modified cell efficacy (and toxicity) that can correlate with clinical outcomes. Here we review current efforts to develop a Synapse Predicts Efficacy (SPE) system for easy, rapid and cost-effective evaluation of CAR-modified immune cell immunotherapy. Ultimately, we hypothesize the conceptual basis and clinical application of SPE will serve as an important parameter in evaluating CAR immunotherapy and significantly advance precision cancer immunotherapy.

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

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