Development and functional characterization of novel fully human anti-CD19 chimeric antigen receptors for T-cell therapy

Impressive outcomes have been achieved by chimeric antigen receptor (CAR)-T cell therapy using murine-derived single-chain variable fragment (scFv) FMC63 specific for CD19 in patients with B cell malignancies. However, evidence suggests that human anti-mouse immune responses might be responsible for poor persistence and dysfunction of CAR-T cells, leading to poor outcomes or early tumor recurrence. Substituting a fully human scFv for murine-derived scFv may address this clinically relevant concern. In this study, we discovered two human anti-CD19 scFv candidates through an optimized protein/cell alternative panning strategy and evaluated their function in CAR-T cells and CD19/CD3 bispecific antibody formats. The two clones exhibited excellent cytotoxicity in CAR-T cells and bispecific antibodies in vitro compared with the benchmarks FMC63 CAR-T cells and blinatumomab. Furthermore, Clone 78-BBz CAR-T cells exhibited similar in vivo antitumor activity to FMC63-BBz CAR-T cells. Our results indicate that Clone 78-BBz CAR has excellent efficacy and safety profile and is a good candidate for clinical development.