Objective:
To assess the pharmacokinetics (PK) and efficacy of prophylactic treatment with BAX 855 - a novel polyethylene glycol (peg)ylated full-length recombinant factor VIII, built on the rAHF-PFM (ADVATE) protein - by age group in previously-treated male patients with severe hemophilia A.
Methods:
Adolescent (12 to <18 years) and adult (18 to 65 years) subjects received 45 ± 5 IU/kg BAX 855 twice weekly as prophylaxis for approximately 6 months. PK was assessed in a subgroup (n=25 planned, including ≥6 adolescents) for one ADVATE infusion, then for BAX 855 at the initial infusion and after ≥50 exposure days (EDs). Efficacy was assessed in all subjects.
Summary:
Twenty-six subjects (8 adolescents, 18 adults) were included in the PK evaluation, and 121 (23 adolescents, 98 adults) were included in the efficacy analysis (all subjects assigned to treatment, i.e. full analysis set). The extended half-life (T1/2) and mean residence time (MRT) of BAX 855 (initial dose) compared to ADVATE were demonstrated by fold increases in the means of 1.4 and 1.5, respectively in both adolescents and in adults, using the one-stage clotting assay. The initial and repeat PK assessments of BAX 855 showed similar results. Consistent trends were observed when PK was determined using the chromogenic assay. The arithmetic mean (SD) annualized bleeding rate (ABR) during prophylaxis with BAX 855 was higher in adolescents than in adults (6.2 [6.1] versus 3.2 [4.2]). ABRs for injury-related bleeding episodes (BEs) were higher in adolescents (arithmetic mean [SD]:2.3 [3.2] versus 1.7 [3.1] in adults), thus contributing to the overall higher ABR in this group. Joint ABRs were lower in adolescents (arithmetic mean [SD]: 1.8 [2.5] versus 3.2 [8.8] in adults) with an inverse relationship for non-joint ABRs. Six adolescents (26.1%) and 39 adults (40.2%) had zero BEs. A total of 48 BEs occurred in adolescents (20 minor; 26 moderate; 2 severe); 182 occurred in adults (69 minor; 103 moderate; 10 severe). The hemostatic efficacy of BAX 855 was rated excellent or good at resolution for the majority of BEs in both age groups (93.8% in adolescents; 92.9% in adults).
Conclusions:
Although fewer adolescents than adults were included in the study, the data suggest that BAX 855 is efficacious in both age groups for twice-weekly prophylaxis and control of BEs. As expected, joint ABR was higher in the adult group.