F9 and hemophilia B: Although the cFIX levels (300–800 ng/ml) in the medium dose group were lower than the normal range of the physiological canine coagulation factor IX level (3000–8000 ng/ml), they remained above the therapeutic level for treatment of hemophilia B (Fig. 2c). However, for mice of the group which received the lowest vector dose (8×109 TU/kg), low serum cFIX levels (∼100 ng/ml) were observed within the first few weeks dropping to undetectable levels at later time points after CCl4 administration (data not shown).