HLA‐haploidentical stem cell transplantation in children with inherited bone marrow failure syndromes: A retrospective analysis on behalf of EBMT severe aplastic Anemia and pediatric diseases working parties

Abstract

AbstractHaploidentical stem cell transplantation (haplo‐SCT) represents the main alternative for children with inherited bone marrow failure syndrome (I‐BMF) lacking a matched donor. This retrospective study, conducted on behalf of the EBMT SAAWP and PDWP, aims to report the current outcomes of haplo‐SCT in I‐BMFs, comparing the different in vivo and ex vivo T‐cell depletion approaches. One hundred and sixty‐two I‐BMF patients who underwent haplo‐SCT (median age 7.4 years) have been registered. Fanconi Anemia was the most represented diagnosis (70.1%). Based on different T‐cell depletion (TCD) approaches, four categories were identified: (1) TCRαβ+/CD19+‐depletion (43.8%); (2) T‐repleted with post‐transplant Cyclophosphamide (PTCy, 34.0%); (3) In‐vivo T‐depletion with ATG/alemtuzumab (14.8%); (4) CD34+ positive selection (7.4%). The cumulative incidences (CI) of neutrophil and platelet engraftment were 84% and 76% respectively, while that of primary and secondary graft failure was 10% and 8% respectively. The 100‐day CI of acute GvHD grade III‐IV(95% CI) was 13%, while the 24‐month CI of extensive chronic GvHD was 4%. After a median follow‐up of 43.4 months, the 2‐year overall survival(OS) and GvHD/Rejection‐free Survival (GRFS) probabilities are 67% and 53%, respectively. The TCR CD3+αβ+/CD19+ depletion group showed a significantly lower incidence of both acute and chronic GvHD and higher OS (79%; p0.013) and GRFS (71%; p < .001), while no significant differences in outcomes have been observed by different diagnosis and conditioning regimens. This large retrospective study supports the safety and feasibility of haplo‐SCT in I‐BMF patients. TCRαβ+/CD19+ depletion offers higher chances of patients' survival, with a significantly lower risk of severe a‐ and c‐GvHD in I‐BMFs compared to other platforms.