Blinatumomab Maintenance Therapy Following Bone Marrow Transplantation for Early Relapsed Pediatric B-cell Precursor Acute Lymphoblastic Leukemia and Analysis of Lymphocyte Subset Changes.

Blinatumomab, a CD19/CD3 bispecific T-cell engager, is recognized as an effective immunotherapy for relapsed B-cell precursor acute lymphoblastic leukemia (BCP-ALL). However, the efficacy and safety of blinatumomab in post-hematopoietic stem cell transplantation (HSCT) maintenance therapy has not been established. A 5-year-old male patient with BCP-ALL suffered a relapse in his bone marrow during maintenance therapy. After re-induction therapy with UK-R3 regimen, 2.3% of the blasts remained. Then the blinatumomab was administered, and he achieved minimal residual disease (MRD)-negative complete remission (CR). After two cycles of blinatumomab, he underwent allogeneic bone marrow transplantation (BMT) from his human leukocyte antigen (HLA)-matched sibling, following conditioning with total body irradiation, etoposide, and cyclophosphamide. Two cycles of blinatumomab maintenance therapy were initiated to prevent relapse. There was no exacerbation of graft-versus-host disease (GVHD) or other severe adverse events. CR was maintained for >22 months after BMT. A t-distributed symmetric neighbor embedding (tSNE) analysis revealed that blinatumomab altered the CD8+ population, as with pre-HSCT use, and markedly reduced the CD8+19dim+/CD8+CD19- ratio (i.e., naïve lymphocyte predominance). Blinatumomab maintenance therapy after HSCT may be considered a safe treatment.