Safety, pharmacokinetics and efficacy of a subcutaneous recombinant FVIII (OCTA101) in adult patients with severe haemophilia A

Abstract Introduction Regular, prophylactic intravenous (i.v.) FVIII can be challenging for some patients with haemophilia A. Subcutaneous (s.c.) FVIII administration could provide an alternative treatment option with greater convenience and without the complications associated with venous access. Aim To assess the safety, pharmacokinetics (PK), bioavailability and efficacy of s.c. OCTA101, a recombinant FVIII with a recombinant von Willebrand factor fragment dimer. Methods This was a single‐centre, prospective, open‐label, phase I/II study (NCT04046848). Previously treated male patients (≥18 years) with severe haemophilia A were eligible for the study. The primary objective of the study was to assess the safety (including immunogenicity) of OCTA101. Secondary objectives included assessments of PK, bioavailability, and the efficacy of prophylaxis. Results Thirty patients were treated with OCTA101. FVIII inhibitors developed in five (16.7%) patients during daily prophylaxis with 40–60 IU/kg (three cases) and 12.5 IU/kg (two cases) OCTA101. The trial was therefore terminated. OCTA101 had a 2.5‐fold longer terminal half‐life compared with i.v. rFVIII, and bioavailability was 16.6%. Efficacy data at study termination indicated that daily prophylaxis with 40–60 IU/kg OCTA101 was efficacious in the absence of FVIII inhibitors. Conclusions Despite promising PK and efficacy results, the trial was terminated due to the incidence of FVIII inhibitors. The occurrence of inhibitors at two dose levels suggests that their development may be related to the subcutaneous route of administration.