3048 Background: Autologous chimeric antigen receptor (CAR) T therapies are highly efficient at targeting hematological malignancies, but the clinical applications have been limited by individualized manufacturing. Furthermore, there has been little success in treating solid tumors due to immunosuppressive microenvironments. Currently, genome editing technologies are being used to address both issues. However, the CRISPR/Cas9 system has significant safety concerns due to high incidence of off-target mutations and TALEN only works sufficiently in activated cells. A hybrid gene editing system, NextGEN (NG) Clo51-dCas9, can be targeted using gRNA, like CRISPR/Cas9, but exhibits little-to-no off-target cutting like TALEN, thereby overcoming limitations in the genome editing of resting T cells. Methods: We successfully developed a platform for production of allogeneic CAR-T cells with reduced receptivity to inhibitory signaling. Here, T cells were modified by piggyBac-mediated BCMA CAR gene delivery, along with NG reagents to knock out critical genes mediating rejection responses. Gene edited CAR-T cells were assessed by mixed lymphocyte reaction (MLR) and tumor killing. In addition, NG was used to knockout multiple checkpoint inhibitory receptors known to mediate key suppressive signals in T cells. Results: NG demonstrated high gene disruption efficiencies for all targets (84% for TCRα, 91% for TCRβ, 64% for β-2 microglobulin, and 40-60% for the surface inhibitory receptors PD-1, CTLA-4, Tim3, Lag-3, and TGFBRII). In contrast to CRISPR/Cas9, no off-target mutations were detected for multiple targets by deep-sequencing. In MLRs, disruption of TCR eliminated the GvHD response, while disruption of MHCI completely abrogated graft-rejection. Lastly, TCR/MHCI double knockout did not affect the ability to kill BCMA+ multiple myeloma cells in vitro. Conclusions: NG overcomes significant limitations of the CRISPR/Cas9 and TALEN systems with highly efficient genome editing in resting T cells. NG has great potential and flexibility for the manufacture of allogeneic CAR-T cells and for enhancing efficacy against solid tumors.
Highly efficient homology-driven genome editing in human T cells by combining zinc-finger nuclease mRNA and AAV6 donor delivery
