Plasma and albumin-free recombinant factor VIII: Pharmacokinetics, efficacy and safety in previously treated pediatric patients

Background: The pharmacokinetics of factor VIII replacement therapy in preschool previously treated patients (PTPs) with hemophilia. A have not been well characterized. Objectives: To assess the pharmacokinetics, efficacy and safety of a plasma-free recombinant FVIII concentrate, ADVATE [Antihemophilic Factor (Recombinant), Plasma/Albumin-Free Method, rAHF-PFM], in children <6 years of age with severe hemophilia. Patients/methods: Fifty-two boys, one girl, mean (±SD) age 3.1 ± 1.5 years and ≥50 days of prior FVIII exposure, were enrolled in a prospective study of ADVATE rAHF-PFM at 23 centers. Results: The mean terminal phase half-life (t_1/2) was 9.88 ± 1.89h, and the mean adjusted in.vivo recovery (IVR) was 1.90 ± 0.43 IU dL^-1(IU kg^-1)^-1. Over the 1-6-year age range, t_1/2 of rAHF-PFM increased by 0.40 h year^-1. IVR increased by 0.095 IU dL^-1 (IU kg^-1)^-1 (kg m^-2)^-1 in relation to body mass index (BMI). Patients primarily received prophylaxis. Median (range) annual joint bleeds were 0.0 (0.0-5.8), 0.0 (0.0-6.1) and 14.2 (0.0-34.5) for standard prophylaxis, modified prophylaxis and on-demand treatment, respectively. Bleeds were managed in 90% (319/354) of episodes with one or two rAHF-PFM infusions; response was rated excellent/good in 93.8% of episodes. Over a median 156 exposure days, no FVIII inhibitors were detected and no related severe adverse events or unusual non-serious adverse events were seen. Conclusions: Children <6 years of age appear to have shorter FVIII t_1/2 and lower IVR values than older subjects. However, these parameters increased with age (t_1/2) and BMI (adjusted IVR), respectively. rAHF-PFM was clinically effective and well tolerated, with no signs of increased immunogenicity in previously treated young children with hemophilia A.