Pharmacokinetics and pharmacodynamics of two antithymocyte globulins in treatment of pediatric aplastic anemia.

Objective: To compare the pharmacokinetics and pharmacodynamics of antithymocyte globulins (ATGs) produced by two companies in the treatment of children with aplastic anemia (AA).

Methods: Six children with acquired AA were divided into two groups. The patients in each group were treated with either R-ATG or F-ATG for 5 consecutive days. Venous blood samples were collected at time points of 0 h, 4 h, 8 h after infusion of ATGs on day 1, at the end of the infusion on day 2-5, and on d7, d21, d35, d60, d90. The plasma concentrations of ATG were measured by ELISA. Pharmacokinetic parameters of ATG was calculated using pharmacokinetics calculation software 3P97. The kinetics of peripheral absolute lymphocyte count (ALC) was monitored. The long-term efficacy was evaluated according to international standards.

Results: The plasma concentration of both R-ATG and F-ATG peaked on day 3~4 after treatment with about 30~32 μg/ml, then fell gradually, reaching half of the peak level on day 21. The traces of ATG were still detectable on day 90. In addition, ALC in both groups declined significantly to a low level for a long time. No significant differences were observed between two groups in terms of the pharmacokinetic parameters and ALC. In an average follow-up period of 12 months, the total response rates (66.7%) in two groups were same. No treatment-related deaths or serious adverse reactions occurred during the treatment.

Conclusion: Both R-ATG and F-ATG have similar characteristics in pharmacokinetics and pharmcodynamics in the treatment of children with AA.