Abstract

ReFacto AF (Albumin-Free Cell Culture Process) is a BDDrFVIII manufactured using an albumin-free cell culture process and purified using a chemically synthesized peptide affinity ligand instead of a murine monoclonal antibody. A virus-retaining filtration step has been included as an additional safety precaution during manufacture. The potency assignment of ReFacto AF has been aligned to the one-stage clotting assay, to permit routine clinical monitoring, as for other rFVIII products, without specialized standards. The pharmacokinetic (PK) profile of ReFacto AF vs. Advate was assessed in a randomized double blind crossover fashion, in 30 previously treated patients (PTPs) (≥ 12 years; FVIII:C ≤1%) using the standard bioequivalence approach based upon the one-stage clotting assay. Safety and efficacy of ReFacto AF was also assessed in a total of 94 PTPs (FVIII ≤2%), which included the PK subjects, during 6 months of open label routine prophylaxis supplemented with on-demand treatment as necessary. A follow-up PK assessment with ReFacto AF was performed in the PK subjects after 6 months. Pharmacokinetic equivalence of ReFacto AF and Advate was demonstrated (n = 30 subjects). The ratios of geometric least-square means for K-value, AUCt, AUC were 100%, 89.8%, and 88.0%, respectively, and associated 90% confidence intervals were within the bioequivalence window of 80%–125%. Twenty five (25) subjects had a baseline and 6 month follow-up PK assessment with ReFacto AF. Mean K-value and t1/2 for ReFacto AF were 2.23 (± 0.39) IU/dL per IU/kg and 11.8 (± 5.1) hours, respectively at baseline and the 6 month follow-up PK profile was unchanged. Of the 94 patients, 89 accrued at least 50 ReFacto AF exposure days. Median routine prophylaxis dose was 30.2 IU/kg. During routine prophylaxis, the median annualized bleed rate was 1.9 (mean 3.9, range 0 to 42.1), and 43 of 94 (45.7%) patients experienced no bleeding episodes. A total of 187 bleeding episodes were treated on-demand with a median dose of 30.6 IU/kg, and 92.5% resolved with 1 or 2 infusions. The overall adverse event (AE) profile was consistent with the AE profile of ReFacto and other rFVIII products. Two of the 94 patients had transient, low-titer, clinically silent inhibitors (0.98 BU/mL and 1.21 BU/mL), each detected by routine surveillance on a single occasion and each was negative on follow-up testing. The corresponding ELISAs for FVIII antibodies were negative for both patients. No patient in the study had a positive ELISA immune response to CHO cell protein or to the peptide affinity ligand used for ReFacto AF purification. ReFacto AF is pharmacokinetically equivalent to Advate based on one-stage FVIII activity assessments, and ReFacto AF PK is stable over 6 months of use. The product is effective in the prevention and treatment of bleeding episodes. Inhibitor safety results show no evidence of neoantigenicity and the AE profile demonstrates safety in PTPs with hemophilia A.

Author notes

Disclosure:Employment: Steven Arkin, Amanda O’Brien and David Roth are employees of Wyeth. Consultancy: Lazlo Nemes: Consultant: Wyeth. Research Funding: Michael Recht: Clinical trial support: Wyeth; Lazlo Nemes: Clinical trial support: Wyeth. Membership Information: Lazlo Nemes: Advisory Board: Wyeth.