Antithymocyte globulin pharmacokinetics in pediatric patients after hematopoietic stem cell transplantation.

To analyze the dose effects of rabbit-derived antithymocyte globulin (ATG) in children after allogeneic hematopoietic stem cell transplantation (HSCT), ATG serum levels were monitored in 32 children and adolescents (median age 3.42 years, range 0.34-18.67 years) and the incidence of acute and chronic graft-versus-host disease, rejection, viral infections, EBV-lymphoproliferative disease, and survival was correlated with the ATG dose used. Cumulative doses from 7.5 to 20 mg/kg showed a constant half-life and linear correlation between dose and Cmax, whereas higher doses (30-40 mg/kg) accumulated in the body. High-dose ATG is of no benefit for preventing graft-versus-host disease but is associated with a significant increase in EBV-linked disease, and it appears to enhance the susceptibility to fatal viral infections and rejection. These data strongly support the use of a low-dose ATG regimen in pediatric HSCT.