High-specificity CRISPR-mediated genome engineering in anti-BCMA allogeneic CAR T cells suppresses allograft rejection in preclinical models

Abstract

Allogeneic chimeric antigen receptor (CAR) T-cell therapies hold the potential to overcome many of the challenges associated with patient-derived (autologous) CAR T cells. Key considerations in the development of allogeneic CAR T-cell therapies include prevention of GvHD and suppression of allograft rejection. Here we describe preclinical data supporting the ongoing first-in-human clinical study, the CaMMouflage trial (NCT05722418), evaluating CB-011 in patients with relapsed/refractory multiple myeloma. CB-011 is a hypoimmunogenic, allogeneic anti-B cell maturation antigen (BCMA) CAR T-cell therapy candidate. CB-011 cells feature 4 genomic alterations and were engineered from healthy donor-derived T cells using a Cas12a CRISPR hybrid RNA-DNA (chRDNA) genome-editing technology platform. To address allograft rejection, CAR T cells were engineered to prevent endogenous human leukocyte antigen (HLA) class I complex expression and overexpress a single-chain polyprotein complex composed of beta-2 microglobulin (B2M) tethered to HLA-E. Additionally, T-cell receptor (TCR) expression was disrupted at the TCR alpha constant locus in combination with the site-specific insertion of a humanized BCMA-specific CAR. CB-011 cells exhibited robust plasmablast cytotoxicity in vitro in a mixed lymphocyte reaction in cell co-cultures derived from patients with multiple myeloma. Additionally, CB-011 cells demonstrated suppressed recognition by and cytotoxicity from HLA-mismatched T cells. CB-011 cells were protected from natural killer (NK) cell-mediated cytotoxicity in vitro and in vivo due to endogenous promoter-driven expression of B2M-HLA-E. Potent antitumor efficacy, when combined with an immune-cloaking armoring strategy to dampen allograft rejection, offers optimized therapeutic potential in multiple myeloma.