Abatacept in combination with ATLG reduces acute GvHD incidence and improves outcomes of children transplanted from mismatched unrelated donors: a real-world, multicenter, retrospective study.
Abstract
Background
The use of HLA-mismatched donors has been associated with increased risk of both acute and chronic Graft versus Host Disease (GvHD). The use of abatacept (ABA) reduces the risk of acute GvHD. ABA data in pediatric patients and in combination with serotherapy are limited.
Objective
We hypothesized that adding ABA to the standard European GvHD prophylaxis with calcineurin inhibitor (CNI), short-course methotrexate (MTX) and anti-T-lymphocyte globulins (ATLG) would result in a lower incidence of acute GvHD and improve survival outcomes. STUDY
Design
We retrospectively analyzed data from 8 pediatric centers on consecutive patients transplanted from an HLA-mismatched unrelated donor who received ABA. The drug was added to standard GvHD pharmacological prophylaxis, including CNI, MTX and ATLG. Besides the classical 4-dose schedule, extended administration was performed (6 total doses).
Results
Between February/2021 and July/2025, 91 pediatric/young adult patients with malignant or non-malignant diseases received ABA. The cumulative incidence (CI) of grade II-IV and grade III-IV acute GvHD were 24.4% and 6.9%, respectively. CI of grade II-IV acute GvHD was higher, but not statistically significant, in patients who received four doses of ABA as compared to those treated with six doses (38.1% vs 19.9%, p=0.08). CI of chronic GvHD was 29.6%, with no difference according to ABA schedule. In children with malignant diseases, relapse incidence was lower in patients receiving extended-course ABA compared to those who received 4 doses (6.9% vs 39.7%, p=0.008), resulting in improved 3-year event-free survival (88.2% vs 44.9%, p=0.001) and overall survival (OS, 91% vs 72.8 p=0.008). Among the 35 patients with non-malignant diseases, OS was 95.7%. No increased incidence of infections was observed, with the exception of EBV reactivation. Finally, we compared the outcomes of the malignant group with those of a comparable cohort from AIEOP-HSCT network, transplanted with the same approach (with the exception of ABA). Three-year GVHD/Relapse-Free Survival was 59.3% for the present cohort and 35.8% for the historical one (p=0.006).
Conclusions
Our data indicate that in patients undergoing mismatched HSCT, ABA, added to a standard GvHD prophylaxis, is a suitable option for preventing GvHD, without impairing the graft-versus-leukemia effect.