CD19 and acute lymphoblastic leukemia: ALL shows high cure rates in children, with a 5-year OS rate of over 90%, but the long-term survival rate in adults is only 35% to 45%, with most relapses due to chemotherapy resistance.34,35 The prognosis for R/R ALL subtypes is much worse than for primary ALL, with a long-term OS rate of 15% to 50%.36 In recent years, CAR-T-cell therapy has made good progress in the treatment of R/R ALL, with the most studied target being CD19.