Neurologic toxicities following adoptive immunotherapy with BCMA-directed CAR T cells

[Immunotherapy in multiple myeloma]

Patients with multiple myeloma who present with refractory disease or relapse after receiving the main classes of available drugs -immunomodulators, proteasome inhibitors and antibodies against CD38- do not have satisfactory therapeutic alternatives. New treatments based on the redirection of T lymphocytes to act directly against tumor cells, such as bispecific antibodies and T cells with chimeric antigen receptors, are changing this scenario. The published information confirms unprecedented antitumor activity of these agents in patients with refractory myeloma and they will certainly represent the backbone of the treatment of these patients in the immediate future. However, these therapies also present specific characteristics and medium or long-term toxicities that pose new healthcare challenges. In this review, we address the current results and future challenges of the administration of these treatments in patients with relapsed or refractory multiple myeloma.

Current progress of CAR-T-cell therapy for patients with multiple myeloma

Currently available chimeric antigen receptor (CAR)-engineered T-cell therapies targeting B-cell maturation antigen (BCMA), namely, idecabtagene vicleucel and ciltacabtagene autoleucel, have shown marked efficacy against relapsed and refractory multiple myeloma. However, further improvement in CAR-T-cell function is warranted as most patients treated with these products eventually relapse due to various mechanisms such as antigen loss and T-cell dysfunction or disappearance. Strategies for improving CAR-T-cell function include targeting of dual antigens, enhancing cell longevity through genetic modification, and eliminating the immunosuppressive tumor microenvironment. Serious side effects can also occur after CAR-T-cell infusions. Although understanding of the molecular pathogenesis of cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome is growing, the unique movement disorder caused by BCMA-targeted therapy is less understood, and its molecular mechanisms must be further elucidated to establish better management strategies. In this article, we will review the current status of BCMA-targeting CAR-T-cell therapy. We will also highlight progress in the development of CAR-T cells targeting other antigens, as well as universal allogeneic CAR-T cells and bispecific antibodies.

Current understanding and management of CAR T cell-associated toxicities

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of several haematological malignancies and is being investigated in patients with various solid tumours. Characteristic CAR T cell-associated toxicities such as cytokine-release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are now well-recognized, and improved supportive care and management with immunosuppressive agents has made CAR T cell therapy safer and more feasible than it was when the first regulatory approvals of such treatments were granted in 2017. The increasing clinical experience with these therapies has also improved recognition of previously less well-defined toxicities, including movement disorders, immune effector cell-associated haematotoxicity (ICAHT) and immune effector cell-associated haemophagocytic lymphohistiocytosis-like syndrome (IEC-HS), as well as the substantial risk of infection in patients with persistent CAR T cell-induced B cell aplasia and hypogammaglobulinaemia. A more diverse selection of immunosuppressive and supportive-care pharmacotherapies is now being utilized for toxicity management, yet no universal algorithm for their application exists. As CAR T cell products targeting new antigens are developed, additional toxicities involving damage to non-malignant tissues expressing the target antigen are a potential hurdle. Continued prospective evaluation of toxicity management strategies and the design of less-toxic CAR T cell products are both crucial for ongoing success in this field. In this Review, we discuss the evolving understanding and clinical management of CAR T cell-associated toxicities.

Beyond BCMA: the next wave of CAR T cell therapy in multiple myeloma

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

Optimizing the CAR T-Cell Therapy Experience in Multiple Myeloma: Clinical Pearls From an Expert Roundtable

Chimeric antigen receptor T-cell (CAR-T) therapies offer substantial advancement in the treatment of multiple myeloma (MM). However, the CAR-T therapy process involves complex decision-making that is informed by many variables. This review aims to provide an overview of the patient selection and administration process for CAR-T therapy for MM from the perspective of experienced healthcare providers (HCPs), including considerations for each step in the CAR-T therapy process. Referring HCPs should initiate conversations with HCPs at CAR-T capable centers earlier in the treatment journey, even before patients are eligible for CAR-T therapy, particularly for patients from underserved populations and patients with high-risk disease, to ensure adequate time for logistical planning and patient education. Patient selection for CAR-T therapy may be guided by factors such as performance status, rate of disease progression, and logistical considerations. Some anticancer therapies may affect T-cell fitness and therefore impact CAR-T manufacturing and patient outcomes; however, additional research is needed to confirm this in MM. Bridging therapies should be tailored to the needs of the patient and ideally halted 1 week or longer before CAR-T infusion, contingent upon the agent(s) used. Lymphodepletion regimens may need to be modified for patients with renal insufficiency. Collaboration with HCPs at both the treating and referring centers is important to optimize coordinated care of patients. Collaboration with and guidance from experienced HCPs throughout patient selection, referral, and CAR-T administration is instrumental in optimizing patient outcomes as access to CAR-T therapies expands.

Optimization of a flow cytometry test for routine monitoring of B cell maturation antigen targeted CAR in peripheral blood

Chimeric antigen receptor (CAR) modified T cell therapies targeting BCMA have displayed impressive activity in the treatment of multiple myeloma. There are currently two FDA licensed products, ciltacabtagene autoleucel and idecabtagene vicleucel, for treating relapsed and refractory disease. Although correlative analyses performed by product manufacturers have been reported in clinical trials, there are limited options for reliable BCMA CAR T detection assays for physicians and researchers looking to explore it as a biomarker for clinical outcome. Given the known association of CAR T cell expansion kinetics with toxicity and response, being able to quantify BCMA CAR T cells routinely and accurately in the blood of patients can serve as a valuable asset. Here, we optimized an accurate and sensitive flow cytometry test using a PE-conjugated soluble BCMA protein, with a lower limit of quantitation of 0.19% of CD3+ T cells, suitable for use as a routine assay for monitoring the frequency of BCMA CAR T cells in the blood of patients receiving either ciltacabtagene autoleucel or idecabtagene vicleucel.

The preclinical discovery and clinical development of ciltacabtagene autoleucel (Cilta-cel) for the treatment of multiple myeloma

INTRODUCTION

Despite remarkable therapeutic advances over the last two decades, which have resulted in dramatic improvements in patient survival, multiple myeloma (MM) is still considered an incurable disease. Therefore, there is a high need for new treatment strategies. Genetically engineered/redirected chimeric antigen receptor (CAR) T cells may represent the most compelling modality of immunotherapy for cancer treatment in general, and MM in particular. Indeed, unprecedented response rates have led to the recent approvals of the first two BCMA-targeted CAR T cell products idecabtagene-vicleucel ('Ide-cel') and ciltacabtagene-autoleucel ('Cilta-Cel') for the treatment of heavily pretreated MM patients. In addition, both are emerging as a new standard-of-care also in earlier lines of therapy.

AREAS COVERED

This article briefly reviews the history of the preclinical development of CAR T cells, with a particular focus on Cilta-cel. Moreover, it summarizes the newest clinical data on Cilta-cel and discusses strategies to further improve its activity and reduce its toxicity.

EXPERT OPINION

Modern next-generation immunotherapy is continuously transforming the MM treatment landscape. Despite several caveats of CAR T cell therapy, including its toxicity, costs, and limited access, prolonged disease-free survival and potential cure of MM are finally within reach.

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

Multiple myeloma (MM) is a rarely curable malignancy of plasma cells. MM expresses B cell maturation antigen (BCMA). We developed a fully human anti-BCMA chimeric antigen receptor (CAR) with a heavy-chain-only antigen-recognition domain, a 4-1BB domain, and a CD3ζ domain. The CAR was designated FHVH33-CD8BBZ. We conducted the first-in-humans clinical trial of T cells expressing FHVH33-CD8BBZ (FHVH-T). Twenty-five patients with relapsed MM were treated. The stringent complete response rate (sCR) was 52%. Median progression-free survival (PFS) was 78 weeks. Of 24 evaluable patients, 6 (25%) had a maximum cytokine-release syndrome (CRS) grade of 3; no patients had CRS of greater than grade 3. Most anti-MM activity occurred within 2-4 weeks of FHVH-T infusion as shown by decreases in the rapidly changing MM markers serum free light chains, urine light chains, and bone marrow plasma cells. Blood CAR+ cell levels peaked during the time that MM elimination was occurring, between 7 and 15 days after FHVH-T infusion. C-C chemokine receptor type 7 (CCR7) expression on infusion CD4+ FHVH-T correlated with peak blood FHVH-T levels. Single-cell RNA sequencing revealed a shift toward more differentiated FHVH-T after infusion. Anti-CAR antibody responses were detected in 4 of 12 patients assessed. FHVH-T has powerful, rapid, and durable anti-MM activity.