Multiplex Genome Editing of Human T Cells with Innovative Transformer Base Editor (tBE) for Construction of Next Generation CAR-T Therapies

Autologous chimeric antigen receptor T (CAR-T) cell therapy has achieved great success for antitumor treatments especially against hematological malignancies, and several autologous CAR-T therapies have been approved around the world. However, high manufacturing cost and long manufacturing process hinder the broader application of autologous CAR-T cell therapy. As a result, off-the-shelf universal CAR-T cell therapy with donor derived healthy T cells is of great interest and under development by many companies globally. Gene editing technologies including TALENs, CRISPR/Cas nucleases and base editors are of great potential in T cell engineering for allogeneic T cell therapy. The innovative transformer base editor (tBE) is a base editing system that avoids to cause DNA double strand breaks (DSBs) and exhibits higher editing efficiency, no detected off-target mutations and lower cytotoxicity. Due to its capability to avoid off-target mutations and DSB-caused chromosomal translocations, tBE is potentially one of the best gene editing tools to induce multiplex editing in cells. Here we show that the tBE was used to induce highly efficient single or multiplex gene editing in primary human T cells. With optimized electroporation conditions for tBE, TRAC, CD52 and PDCD1 could be knocked out simultaneously with editing efficiency up to ~90% for each target gene. tBE triggered no detected off-target mutation or chromosomal abnormalities, which were reported in the cases of CRISPR/Cas- or TALEN-mediated multiplex editing. CD19-targeted CAR-T cells with triplex base editing exhibits enhanced antitumor efficacy in vitro and in mouse models compared with unedited CAR-T cells. Our results demonstrated the application of tBE for construction of next generation universal or enhanced CAR-T therapies.