CD19 and acute lymphoblastic leukemia: However, no trends were found in other subgroups, including the proportion of patients with primary refractory B-ALL (<15% vs. ≥15%), the proportion of bridging allo-HSCT after CAR T-cell therapy (<20% vs. ≥20%), CD19 single-chain variable fragment clone (FMC63 vs. others), T-cell origin (autologous vs. allogeneic), and the sample size of trials (<20 vs. ≥20).