CD19-Specific CAR-T Cell Treatment of 115 Children and Young Adults with Acute B Lymphoblastic Leukemia: Long-term Follow-up

Purpose Chemotherapy has been the primary treatment for patients with B-cell acute lymphoblastic leukemia (B-ALL). However, there are still patients who are not sensitive to chemotherapy, including those with refractory/relapse (R/R) disease and those experiencing minimal residual disease (MRD) re-emergence. Chimeric antigen receptor-T lymphocytes (CAR-T) therapy may provide a new treatment option for these patients. Materials and Methods Our institution conducted a single-arm prospective clinical trial (ChiCTR-OPN-17013507) using CAR-T-19 to treat R/R B-ALL and MRD re-emergent patients. One hundred and fifteen patients, aged 1-25 years (median age, 8 years), were enrolled, including 67 R/R and 48 MRD re-emergent CD19-positive B-ALL patients. Results All patients achieved morphologic complete remission (CR), and within 1 month after infusion, 111 out of 115 (96.5%) patients achieved MRD-negative CR. With a median follow-up time of 48.4 months, the estimated 4-year leukemia-free survival (LFS) rate and overall survival (OS) rate were 68.7%+/- 4.5% and 70.7%+/- 4.3%, respectively. There were no significant differences in longterm efficacy observed among patients with different disease statuses before infusion (4-year OS: MRD re-emergence vs. R/R B-ALL, 70.6%+/- 6.6% vs. 66.5%+/- 6.1%, p=0.755; 4-year LFS: MRD re-emergence vs. R/R B-ALL, 67.3%+/- 7.0% vs. 63.8%+/- 6.2%, p=0.704). R/R B-ALL patients bridging to transplantation after CAR-T treatment had a superior OS and LFS compared to those who did not. However, for MRD re-emergent patients, there was no significant difference in OS and LFS, regardless of whether they underwent hematopoietic stem cell transplantation or not. Conclusion CD19 CAR-T therapy effectively and safely cures both R/R B-ALL and MRD re-emergent patients.