Tcrαβ-Depleted Haploidentical Hematopoietic Cell Transplantation for Pediatric Patients with Severe Aplastic Anemia

Purpose We evaluated the outcome of haploidentical hematopoietic cell transplantation (haplo-HCT) using an ex vivo TCRαβ-depleted graft in pediatric patients with acquired severe aplastic anemia (SAA). Patients and methods Between May 2013 and July 2023, 46 pediatric patients with acquired SAA received haplo-HCT using ex vivo TCRαβ-depleted graft at our center. Of 46 patients, 24 were male and the median age at transplant was 11.6 years (range, 1.4 ̶ 22.6). Donors were father in 16, mother in 16 and sibling in 14. Of the 46 patients, 38 received upfront haplo-HSCT for treatment-naïve SAA and 8 received salvage haplo-HCT for refractory/relapsed SAA. Conditioning regimen consisted of Total body irradiation (TBI 400 or 600 cGy), fludarabine 180 mg/m2, cyclophosphamide 100 mg/kg and r-ATG 3-7.5 mg/kg. Results Forty-five (98%) of 46 patients achieved neutrophil engraftment at a median of +10 days (range, 9-12 days). One patient experienced primary graft failure (GF) and the other one patient developed late GF at +125 days. All the 2 patients received rescue transplantations and achieved neutrophil engraftment. The CI of acute GVHD ≥ grade 2 and ≥ grade 3 were 40% and 20%, respectively. No patient developed grade 4 or moderate/severe chronic GVHD. Four patients died at a median of 205 days after receiving haplo-HSCT (CMV disease in 2, and TMA in 1 and MOF in 1). At a median follow-up of 71 months (range, 3-127), failure-free survival and overall survival (OS) were 89% ± 4.8% and 91% ± 4.4%, respectively. OS was comparable between upfront and salvage haplo-HCT (naïve 92% vs salvage 88%, P>.05). Higher TBI dose seemed to have a better OS (95% for 600 cGy vs 86% for 400 cGy, P>.05) Conclusions This study demonstrated that our current haplo-HSCT using ex vivo TCRαβ-depleted graft is a viable treatment option for pediatric patients with acquired SAA who lack a suitable related or unrelated donor.