Combining CRISPR/Cas9-mediated TRAC knockout with mRNA-based CAR expression enables flexible generation of allogeneic CAR T cells

BACKGROUND: Autologous chimeric antigen receptor (CAR) T-cell therapies have demonstrated remarkable efficacy in hematologic malignancies but remain limited by complex manufacturing processes. Allogeneic, off-the-shelf CAR T cells derived from healthy donors represent a promising alternative; however, safe implementation requires elimination of endogenous T-cell receptor (TCR) expression and flexible CAR expression strategies. OBJECTIVE: This study aimed to develop an optimized manufacturing workflow for allogeneic CAR T cells by combining CRISPR/Cas9-mediated TCR knockout with mRNA-based CAR expression, and to evaluate cryopreservation strategies enabling on-demand CAR T-cell generation. METHODS: Healthy donor T cells were edited at the TRAC locus using CRISPR/Cas9 to generate TCR-deficient T cells. These cells were cryopreserved and subsequently transfected with mRNA encoding CD117, BCMA, or CD19 CARs. CAR expression, cell viability, immunophenotype, cytokine secretion, and antigen-specific cytotoxicity were assessed under different cryopreservation-transfection conditions. RESULTS: TCR knockout T cells exhibited efficient TCR disruption with reduced alloreactive proliferation. CD117 mRNA CAR T cells derived from TCR-deficient T cells demonstrated CAR expression kinetics, immunophenotypic profiles, and antigen-specific cytotoxicity comparable to wild-type CAR T cells. Evaluation of two cryopreservation strategies revealed that cryopreservation prior to mRNA electroporation preserved cell viability, phenotype, and cytotoxic function, whereas cryopreservation after mRNA transfection was associated with reduced functional activity. The optimized protocol was successfully extended to CD19- and BCMA-targeting CAR mRNAs. CONCLUSION: Collectively, these findings establish a modular platform for producing allogeneic CAR T cells using mRNA technology, offering a practical approach for rapid, on-demand CAR T-cell therapy.