CD19 and acute lymphoblastic leukemia: Regarding the binding affinity of CARs consisting of scFv, it has been reported that a low-affinity CAR (KD: 1.4 × 10−8 M), which exhibits more than 40-fold lower affinity for CD19 compared to existing scFvs derived from FMC63, enhances CAR-T cell expansion and prolongs persistence in pediatric patients with ALL [38].