Preventive infusion of donor-derived CAR-T cells after haploidentical transplantation: Two cases report

RATIONALE: Relapse is the main cause of death after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Unfortunately, there are no efficient methods to prevent relapse after allo-HSCT. Chimeric antigen receptor T (CAR-T) cells have achieved favorable outcomes in the treatment of refractory/relapsed acute lymphoblastic leukemia (ALL) because of their strong anti-leukemia activity. However, it is unclear whether the CAR-T cells constructed using viral systems can be used as preventive infusions to prevent relapse after haploidentical HSCT. PATIENT CONCERNS: Two patients with ALL with high risk received haploidentical HSCT. DIAGNOSES: Two patients were diagnosed with ALL with high risk. INTERVENTIONS: Patients received preventive infusion of donor-derived CAR-T cells constructed using viral systems on day 60 after haploidentical HSCT. OUTCOMES: The CAR-T cells were continually detected, and no graft versus host disease developed. The two patients survived with disease-free for 1 year and 6 months, respectively. LESSONS: Preventive infusion of donor-derived CAR-T cells after haploidentical HSCT may be safe and that immunosuppressors may not affect the proliferation of CAR-T cells.