A prospective, open, single-arm clinical trial of fludarabine- cyclophosphamide-porcine anti-lymphocyte globulin conditioning combined with matched sibling donor hematopoietic stem cell transplantation in the treatment of severe aplastic anemia

Hematopoietic stem cell transplantation (HSCT) remains an effective treatment for severe aplastic anemia (SAA), but the optimal conditioning regimen has yet to be established. This study aimed to evaluate the safety and efficacy of a conditioning regimen consisting of fludarabine (Flu), cyclophosphamide (Cy), and porcine anti-lymphocyte globulin (p-ATG). This prospective single-arm clinical trial enrolled 48 SAA patients who underwent HLA-matched sibling transplantation. The conditioning regimen consisted of p-ATG (120 mg/kg), Cy (120 mg/kg), and Flu (120 mg/m²). All patients achieved neutrophil engraftment (median time of 12 days), with 98% attaining platelet recovery (median time of 13 days). Complete donor chimerism was achieved in 95.8% of patients by day + 30. Cardiac toxicity was observed in three patients. No grade 4 regimen-related toxicity was observed. The cumulative incidences of grade acute GVHD and chronic GVHD were 21.0% (95% CI: 8.5% to 31.8%) and 15.8% (95% CI: 4.2% to 25.9%), respectively. The 1-year overall survival rate was 97.9% (95% CI: 94% to 100%). In this single-arm study, these results indicate that the conditioning regimen of p-ATG combined with Flu and Cy is associated with stable engraftment, an acceptable safety profile, and a manageable incidence of GVHD.