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Role of Donor-Derived CD19.CAR-T Cells in Treating Patients That Relapsed after Allogeneic Hematopoietic Stem Cell Transplantation

Background
 The Chimeric Antigen Receptor T (CAR-T) cells with strong anti-leukemia role can treat relapsed/refractory CD19-positive acute lymphoblastic leukemia (CD19+-ALL) with good outcome. The allogeneic CAR-T cells receives activation signals from both T cell receptor (TCR) and CAR, which may possess stronger activity in anti-leukemia cells. However, the infusion of allogeneic CAR-T cells may cause graft-versus-host disease, which could limit its application after allogeneic hematopoietic stem cell transplantation (allo-HSCT). It is still unclear that the role of the donor-derived CAR-T cells in treating relapsed patients after allo-HSCT. In this study, the prospective study was performed to investigate the role of donor-derived CAR-T cells on relapsed patients after allo-HSCT.
 Methods
 From April 2016 to March 2019, relapsed patients after allo-HSCT with CD19+-ALL and a Karnofsky score greater than or equal to 60 were enrolled in this study. The donor underwent apheresis for mononuclear cells to construct the CAR-T cells. The bone marrow aspiration every month after CART- cells infusion was carried out for the assessment of disease status by follow cytometry. The chimerism was detected every month after CAR-T cells treatment.
 Results
 Eighteen patients enrolled in this study. The median number of infused CAR-T cells was 1.825Í106/Kg. Thirteen patients (13/18=72.22%) reached complete remission (CR) after CAR-T cells treatment. Four patients (4/18=22.22%) had ineffectiveness. One patient died from b uncontrolled bleeding because of low platelet. The patients with blast cells <5% had higher CR. The full chimerism achieved after CART- cells treatment for all patients with the decrease of chimerism at the time of relapse. The median time of follow-up was seven months (ranged from three months to twenty-five months). Three patients with decreased CAR-T cells or chimerism was underwent allogeneic hematopoietic stem cell transplantation or relapsed within six months. The other eleven patients were complete remission with full chimerism or the continual proliferation of CAR-T cells without the second allo-HSCT during our follow-up period. Seventeen patients observed cytokine release syndrome in which six patients with degree III-IV. Two patients developed GVHD in skin and intestinal tract. All patients recovered after management. No other severe complications and death were observed.
 Conclusion
 Our results showed that the treatment by donor-derived CAR-T cells for relapsed patients after allo-HSCT is safe and effective. No second transplantation was needed for relapsed patients after allo-HSCT with the treatment of donor-derived CAR-T cells that with good chimerism and continual proliferation of CAR-T cells. However, further clinical trials should be performed to investigate this protocol with larger cases.
 
 
 No relevant conflicts of interest to declare.
