CAR‐HEMATOTOX: A DISCRIMINATIVE MODEL FOR CAR T‐CELL RELATED HEMATOTOXICITY IN RELAPSED/REFRACTORY LARGE B‐CELL LYMPHOMA

Mechanisms of Resistance and Treatment of Relapse after CAR T-cell Therapy for Large B-cell Lymphoma and Multiple Myeloma

Although chimeric antigen receptor (CAR) T cell therapy (CAR-T) has altered the treatment landscape for relapsed/refractory B cell malignancies and multiple myeloma, only a minority of patients attain long-term disease remission. The underlying reasons for CAR-T resistance are multifaceted and can be broadly divided into host-related, tumor-intrinsic, microenvironmental and macroenvironmental, and CAR-T-related factors. Emerging host-related determinants of response to CAR-T relate to gut microbiome composition, intact hematopoietic function, body composition, and physical reserve. Emerging tumor-intrinsic resistance mechanisms include complex genomic alterations and mutations to immunomodulatory genes. Furthermore, the extent of systemic inflammation prior to CAR-T is a potent biomarker of response and reflects a proinflammatory tumor micromilieu characterized by infiltration of myeloid-derived suppressor cells and regulatory T cell populations. The tumor and its surrounding micromilieu also can shape the response of the host to CAR-T infusion and the subsequent expansion and persistence of CAR T cells, a prerequisite for efficient eradication of tumor cells. Here, focusing on both large B cell lymphoma and multiple myeloma, we review resistance mechanisms, explore therapeutic avenues to overcome resistance to CAR-T, and discuss the management of patients who relapse after CAR-T.

Managing Hypogammaglobulinemia in Patients Treated with CAR-T-cell Therapy: Key Points for Clinicians

INTRODUCTION

The unprecedented success of chimeric antigen receptor (CAR)-T-cell therapy in the management of B-cell malignancies comes with a price of specific side effects. Healthy B-cell depletion is an anticipated 'on-target' 'off-tumor' side effect and can contribute to severe and prolonged hypogammaglobulinemia. Evidence-based guidelines for the use of immunoglobulin replacement therapy (IGRT) for infection prevention are lacking in this population.

AREAS COVERED

This article reviews the mechanisms and epidemiology of hypogammaglobulinemia and antibody deficiency, association with infections, and strategies to address these issues in CD19- and BCMA-CAR-T-cell recipients.

EXPERT OPINION

CD19 and BCMA CAR-T-cell therapy result in unique immune deficits due to depletion of specific B-lineage cells and may require different infection prevention strategies. Hypogammaglobulinemia before and after CAR-T-cell therapy is frequent, but data on the efficacy and cost-effectiveness of IGRT are lacking. Monthly IGRT should be prioritized for patients with severe or recurrent bacterial infections. IGRT may be more broadly necessary to prevent infections in BCMA-CAR-T-cell recipients and children with severe hypogammaglobulinemia irrespective of infection history. Vaccinations are indicated to augment humoral immunity and can be immunogenic despite cytopenias; re-vaccination(s) may be required. Controlled trials are needed to better understand the role of IGRT and vaccines in this population.