CAR-T cells shape the immunological potential of the tumor microenvironment

CAR-T cells lose effectiveness over time and subsequent lines of immunotherapy become increasingly less potent. Investigating patients from two independent clinical trials at single cell resolution, we demonstrate that CAR-T cell treatment drives bystander CD8+ T lymphocytes along the differentiation path, which initially supports a clonal anti-tumor immune response, but ultimately results in terminal exhaustion, reduced potential for self-renewal and sustained depletion of the tumor-reactive T cell repertoire. The immune environment changes orchestrated by CAR-T cells result in reduced immune capacity, which could potentially diminish responses to other immunotherapies, such as response to checkpoint blockade. We describe the transcriptional modules that regulate plasticity of the T lymphocytic compartment and identify Tim3/Gal9 and CD27/CD70 as two crucial interactions of the cell-cell communication network that regulates immune capacity. The ability of the CAR-T cells to shape a regulatory immune microenvironment may explain why repeated immunotherapies become increasingly less successful, even when targeting distinct antigens. Our studies provide a framework for assessing and manipulating the ‘mileage’ of the immune system as a predictive marker and a therapeutic opportunity. Single cell expression profiles of 4 patients with relapsed/refractory multiple myeloma (RRMM) treated with BCMA-directed CAR-T cells profiled with 10X Genomics technology (5' expression profiling) and single cell expression profiles of T cells and CAR-T cells isolated from RRMM 24 patients treated with BCMA-directed CAR-T cells profiled with plate-based scRNA-Seq (Smartseq2). Submitter declares that the raw data is not provided due to patient privacy concerns.