Recombinant Anti-Ad fiber knob x Anti-CEA Bispecific Antibody (scIgG) is intended to be expressed as two chains, each of which contains the identical immunoglobulin units as the anti-Ad fiber knob and anti-CEA IgGs from the parent antibodies. Using Fc KIH, the two chains combine to form a heterodimer. Adenoviral vectors can be retargeted by this BsAb to tumor cells. It can be applied in cancer gene therapy to deliver a therapeutic gene to tumor cells with the goal of efficient and targeted cell death.