Successful Engraftment Following Blinatumomab and Donor-Derived Buffy Coat Infusion in a Patient With Relapsed B-cell Acute Lymphoblastic Leukemia and High-Level Donor-Specific Anti-HLA Antibodies: A Case Report.

A 40-year-old Japanese woman with Philadelphia chromosome-negative B-cell acute lymphoblastic leukemia (B-ALL) underwent human leukocyte antigen (HLA)-matched related peripheral blood stem cell transplantation approximately 22 months before the current transplantation because measurable residual disease persisted after induction therapy. She experienced hematologic relapse approximately six months before the current transplantation and achieved complete remission after two cycles of inotuzumab ozogamicin. A second transplantation using her HLA-haploidentical son as the donor was planned; however, pretransplant testing detected donor-specific anti-HLA antibodies (DSA) against HLA-A31 and HLA-B51, with mean fluorescence intensity (MFI) values of 10,582 and 19,288, respectively. Five doses of rituximab reduced the MFI values for HLA-A31 and HLA-B51 to 2,341 and 9,789, respectively. Two cycles of blinatumomab produced a further reduction, although the HLA-B51 MFI remained above 3,000. An irradiated donor-derived buffy coat prepared from 400 mL of whole blood was therefore infused one day before stem cell infusion, followed by haploidentical hematopoietic stem cell transplantation. Neutrophil engraftment was achieved on day 9, complete donor chimerism was confirmed on day 28, and DSA became undetectable on day 33. No secondary graft failure or severe acute graft-versus-host disease occurred. This case suggests that blinatumomab followed by donor buffy coat infusion may be considered as part of a multimodal desensitization strategy in selected patients with B-ALL and persistent clinically significant DSA. However, the efficacy and safety of this approach cannot be established from a single case.