Background Major ABO-group incompatibility increases the risk of delayed erythroid engraftment, and other immunological complications post allogeneic hematopoietic stem cell transplantation (allo-HSCT). Blinatumomab, a CD19/CD3 bispecific T-cell engager antibody, has demonstrated efficacy in eradicating CD19 positive B lymphocytes. However, its role in optimizing immune complications after an ABO incompatible transplant remains unreported.

Methods We performed a single-center retrospective analysis on 42 consecutive B-ALL patients who received major or bidirectional ABO-incompatible allogeneic HSCT between June 2021 to June 2025. Patients were divided into three groups: group A (incompatible major ABO-group with blinatumomab treatment, n=13), group B (incompatible ABO-group without blinatumomab treatment, n=10), and group C (compatible ABO-group with blinatumomab treatment, n=19). The primary endpoint was the time to transfusion independence (defined as the first day without red blood cell transfusion for 3 consecutive months). The secondary endpoints included total red blood cell transfusion volume, time to blood type conversion, immune reconstitution indicators, and other survival outcomes. Multi-group comparisons were performed using the Kruskal-Wallis test, and survival analysis was evaluated using the Kaplan-Meier method.

Results The median times to transfusion independence in group A , group B, and group C were 1 (range, 1-13), 54 (1-119), and 1 (1-67) days, respectively. Compared to group B, blinatumomab shortened the time to transfusion independence in group A (P=0.011), reduced the red blood cell transfusion volume (group A vs group B: 0 (0-5.50) vs 8.5 (0-16) U; P=0.031) and relapse rate (2-year relapse rate: 12.50% vs 40.00%; P=0.041), and improved overall survival (2-year survival rate: 87.50% vs 60.00%, P=0.046). No statistical differences were observed between group A and group C (P>0.05). However, no statistical differences existed among the three groups in neutrophil engraftment time (group A vs group B vs group C: 12 (9,14) vs 13 (12,18) vs 13 (10,17) days), platelet engraftment time (13 (9,22) vs 15 (12,22) vs 14 (10,27) days), time to blood type conversion (group A vs group B: 106 (54,175) vs 111 (101,293) days), post-transplant B lymphocyte count (3 (0,73) vs 10.5 (0,355) vs 2 (0,522) cells/μL), CD4+ cell count (70 (1,146) vs 45 (1,419) vs 81 (2,486) cells/μL), incidence of grade II-IV acute graft-versus-host disease (aGVHD) (100-day grade II-IV aGVHD rate: 15.40% vs 31.60% vs 20.00%), and incidence of chronic graft-versus-host disease (cGVHD) (3-year cGVHD rate: 23.10% vs 20% vs 27%) (P>0.05). In the assessment of immune function, post-transplant globulin levels (25.20 (17.50,31.40) vs 17.10 (14,25.40) g/L, P=0.036) and IgG levels (9.30 (5.62,13.60) vs 5.73 (2.58,11) g/L, P=0.041) in group B were higher than those in group C, but the levels in group A (globulin: 18.80 (14.70,24.80) g/L; IgG: 6.19 (4.01,10.80) g/L) fell in between the two groups with no statistical significance (P>0.05).

ConclusionsBlinatumomab improves time to erythroid engraftment after a major ABO-incompatible transplant.

Disclosures No relevant conflicts of interest to declare.

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2025
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