Recombinant Anti-CA72-4 x Anti-CD3 Bispecific Antibody (Single-chain Diabody) is designed to be expressed as three chains derived from the variable domains of anti-CA72-4 and anti-CD3 parental antibodies. The middle linker is long enough to form scFv dimers between the two diabody chains. And the two Fd regions are connected by a flexible linker. This BsAb can retarget T cells to tumor cells. It is designed for the research of Gastrointestinal cancer; Ovarian cancer; Colon cancer; Gastric cancer; Breast cancer; Adenocarcinomas therapy.