Pharmacokinetics and tissue distribution of B-domain deleted recombinant human factor VIII (GC-γ AHF) in rats

Recombinant human factor VIII is a glycoprotein that is used for the treatment of hemophilia A. The B-domain deleted recombinant factor VIII, GC-γ AHF, was newly developed by the Korea Green Cross Pharmaceutical Company. To investigate its pharmacokinetics and tissue distribution, GC-γ AHF was labelled with ¹²⁵I. Following a single intravenous administration of [¹²⁵I]GC-γ AHF to rats, plasma concentrations of [¹²⁵I]GC-γ AHF versus time curves were analyzed and the pharmacokinetic parameters were estimated. The data obtained from plasma as fitted with a two compartment open model and mean residence time (MRT) was 123.83 min. The half life of radioactivity associated with [¹²⁵I]GC-γ AHF in plasma was 13.25 min and other pharmacokinetic parameters of GC-γ AHF were as follows: Clearance, 23 ml/min/kg; steady-state volume of distribution, 2.84 l/kg. A larger proportion of the administered radioactivity was excreted via urine than via faeces and the total administered dose recovered in excreta was 88.2%. The total levels of radioactivity were higher in liver, stomach and small intestine than in other tissues. These studies suggest that the pharmacokinetic data of GC-γ AHF obtained from rats in the present study would be useful for preclinical evaluation of the newly developed genetically engineered human protein.