Abstract Objective: To evaluate the clinical efficacy of single unrelated cord blood transplantation (UCBT) with anti-thymocyte globulin (ATG)-containing conditioning regimen for the treatment of mucopolysaccharidosis (MPS).

Methods: A retrospective study was conducted to analyze the data of 41 children with MPS who underwent single UCBT ATG-containing conditioning regimen in the Children's Hospital of Capital Institute of Pediatrics from June 2020 to June 2024. Children were divided into low-dose ATG group (ATG dosage <3 mg/kg) and high-dose ATG group (ATG dosage ≥3 mg/kg). Graft-versus-host disease (GVHD) prevention involved using cyclosporine A (CsA) or tacrolimus (FK506) combined with mycophenolate mofetil (MMF).

Results: 95.12% of the children (39/41) who underwent UCBT were successful. The median time for neutrophil and platelet recovery was 18 and 26 days, respectively, with the cumulative engraftment rates of 97.6% and 95.2% on 42 days. The univariate regression analysis showed that the number of prefrozen CD34⁺ cells had a significant effect on the time for neutrophils recovery (β = 0.35, P = 0.012, R² = 0.18), colony forming units (CFUs) had a significant effect on the transfusion requirements of red blood cells and platelets (β = 0.22, P = 0.045, R² = 0.15). There were no significant differences in engraftment rate, incidence of acute GVHD (aGVHD), or chronic GVHD (cGVHD) between the two groups (P>0.05), but the reactivation rate of cytomegalovirus (CMV) was significantly higher in the high-dose ATG group compared with the low-dose group (P<0.05). T test showed that the levels of regulatory T (Treg) cells in low-dose ATG group was significantly higher than that in high-dose ATG group at 2 and 3 months after transplantation (P=0.045, 0.027), while there was no significant difference in the levels of CD4+, CD8+, natural killer (NK) and B cells between the two groups. The overall survival of all patients with MPS was 97.6% at 1 year after transplantation. The enzyme activity of patients with successful transplantation returned to normal, urinary mucopolysaccharides (GAGs) turned negative within 3-6 months, and clinical symptoms was improved after single UCBT.

Conclusion: The engraftment rate and survival rate of patients with MPS who underwent single UCBT with ATG-containing conditioning regimen were high. The levels of Treg cells of low-dose ATG group were increased in the early stage after transplantation, which not only did not increase the graft failure risk and GVHD incidence, but also reduced the rate of CMV reactivation. Therefore, it is recommended to consider low-dose ATG in UCBT conditioning regimen to achieve a high engraftment rate and low risk of infection.

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2025
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