Safety and pharmacokinetics of subcutaneously administered recombinant activated factor VII (rFVIIa)

Recombinant activated factor VIIa (rFVIIa) is used to treat bleeds in hemophilia patients with inhibitors. A subcutaneous formulation could potentially improve its half-life and make it suitable for prophylactic treatment.

A study was conducted to determine the safety of subcutaneously administered rFVIIa in patients with hemophilia and the pharmacokinetic profile (including bioavailability).

This was a multicenter, open-label, cross-over comparison of single doses of intravenous rFVIIa 90μgkg(-1) and a new formulation of rFVIIa for subcutaneous injection at dose levels of 45, 90, 180, 270 and 360μgkg(-1) . Sixty subjects (12 per dose cohort) with hemophilia A or B were enrolled.

Subcutaneously administered rFVIIa showed lower mean peak plasma concentrations and prolonged FVII activity (C(max) , 0.44-5.16IU mL(-1) [across doses]; t(1/2) , 12.4h; t(max) , 5.6h) compared with intravenously administered rFVIIa (C(max) , 51.7IUmL(-1) ; t(1/2) , 2.7h; t(max) , <10min). The absolute bioavailability of subcutaneous rFVIIa ranged from 21.1 to 30.1% across dose levels. Dose proportionality was observed within a 2-fold dose increase but not across the full dose range. No thromboembolic events, drug-related serious adverse events, severe injection-site reactions or neutralizing antibodies were reported (primary endpoint). Mild and moderate injection-site reactions were more frequent with subcutaneous than with intravenous injections.

This phase I clinical trial did not identify safety concerns of prolonged exposure to rFVIIa administered subcutaneously in single doses to hemophilia patients.