hFIX levels in the systemic circulation of SCID mice after intramuscular implantation of myoblasts carrying pdLMe4βAhIXm1 or LIXSN. The background ELISA signals obtained from group 1 (control group) mice, which were injected with 2 × 10⁷ myoblasts transduced with BAG, were subtracted from the observed levels of other groups. Group 2 mice were injected with 2 × 10⁷ myoblasts transduced with LIXSN. On day 0, group 3, group 4, and group 5 animals were injected with 5, 10, and 20 × 10⁶ myoblasts stably transfected with pdLMe4βAhIXm1, respectively. Mice in group 4 were injected with additional cell doses (1, 1, and 2 × 10⁷ cells, respectively) on days 43, 52, and 59 as shown with arrows. Results from individual animals in each group were shown.