Pharmacokinetics and pharmacodynamics of rFIXFc in FIX-deficient dogs. Two dogs with hemophilia B were intravenously infused with rFIXFc at 140 IU/kg body weight. Blood samples were collected at 5, 15, and 30 minutes and at 1, 2, 4, 6, 8, 12, 24, 27, 30, 48, 51, 54, 72, 80, 96, 126, 144, and 168 hours. (A) FIX clotting activity was measured for all time points with respect to a standard curve generated with rFIXFc. (B) A sandwich ELISA that used a FIX capture antibody and Fc-HRP detection antibody was used to measure the concentration of intact rFIXFc in the plasma samples of the dog with hemophilia B. (C) Blood collected from animals was immediately analyzed for WBCT. Blood samples were incubated at 28°C and were visually inspected for the presence of a clot once per minute, and the time in which a clot formed was recorded.