A Feasibility and Safety Study of Concomitant Therapy With Allo-CAR-T Cells and Allo-HSCT in Patients With Relapse or Refractory Leukemia

Allogenic hematopoietic stem cell transplant (Allo-HSCT) is routinely used for treatment of aggressive hematological malignancies. The biological foundation of allo-HSCT is the graft-versus-leukemia (GVL) effect, which is primarily mediated by donor T cells present in the graft and is able to eradicate malignant B cells either CD19+ or CD19-. Relapse following an allo-HSCT remains a major challenge in the treatment of B-ALL. CD19-directed CAR-T cell therapy has shown promising results for the treatment of relapsed or refractory B-cell malignancies; however, a subset of patients relapse due to the loss of CD19 in tumor cells. Co-infusion of donor-derived CD19/22 bispecific CAR-T cells or CD19-directed CAR-T cells and donor-derived-HSCT has the potential to combine the CAR-T cell mediated targeted elimination of CD19 expressing B cells with GVL effect, which could have clear advantages in reducing the risk of relapse and the evolution of CD19- escape variants or clonally related malignancies in other lineages. Therefore, a complete and durable tumor responses induced by this immunotherapy could be expected.