Initiation of Pediatric Clinical Trials for Coagulation Factors: Application of Pharmacokinetics and Allometry to First-in-Pediatric Dose Selection.

Allometric scaling is a method that can be used for the extrapolation of pharmacokinetic parameters from adults to children. Subsequently, these allometrically predicted PK parameters can be used to project a suitable dose to initiate a pediatric clinical trial. The objective of this study was to predict clearance and in vivo recovery of coagulation factors VIII and IX allometrically in children from 1 year of age to adolescents and then project the first-in-children dose. The values for observed clearance, in vivo recovery, and dose for pediatric as well as adult subjects for 7 factor VIII and 3 factor IX products were obtained from the US Food and Drug Administration package insert and the allometrically predicted clearance, in vivo recovery, and dose were compared with the observed values. The clearance of factors VIII and IX were predicted with reasonable accuracy. Of 27 predicted clearance values, all 27 (100%) were predicted with ≤30% prediction error (range, 5%-28%). Of 27 predicted in vivo recovery values, 26 (96%) were predicted with ≤30% prediction error (range, 0%-45%). The projected doses of factor VIII or IX, either by clearance or in vivo recovery, were generally within the recommended dose range indicating an accurate prediction of pediatric dose for both factors. The proposed allometric methods can be used to select first-in-children dose in pediatric clinical trials.