Abstract: Disclosed is a bispecific antibody that specifically binds to surface antigens CD3 of immune cells and CD20 antigens on the surfaces of tumor cells, and that can bind to human CD3 with high affinity, inducing T cell proliferation, and mediating tumor cell killing. The bispecific antibody in an in vitro test was able to mediate the specific killing of target cells by T cells. The construction method thereof is simple, avoiding the possibility of mismatch between two sets of light chains and heavy chains of heterobispecific antibodies, thereby reducing the difficulty of antibody purification. The affinity of the obtained antibody is high, the side effects caused by cytokines are small, and safety is high.

Abstract: Provided is a tetravalent, homodimer-type bispecific antibody molecule that targets both immune effector cell antigen CD3 and tumor-related antigen CD19. The bispecific antibody molecule comprises first and second single-chain Fv and Fc fragments in sequence from the N-terminus to the C-terminus, wherein the first single-chain Fv can specifically bind to CD19, the second single-chain Fv can specifically bind to CD3, the first and second single-chains Fv are connected by means of a linker peptide, the second single-chain Fv and Fc fragments are directly connected to each other or connected by means of a linker peptide; and the Fc fragment does not have effector functions such as CDC, ADCC, and ADCP.

Abstract: Provided is a tetravalent homodimeric bispecific antibody molecule simultaneously targeting an immune effector cell antigen CD3 and a tumor-associated antigen, wherein the bispecific antibody molecule contains, in order from N-terminus to C-terminus, a first single chain Fv, a second single chain Fv and a Fc fragment; wherein the first single chain Fv can specifically bind to the tumor-associated antigen, the second single chain Fv can specifically bind to CD3, and the first and the second single chain Fvs are connected by a linker peptide, while the second single chain Fv and the Fc fragment are directly connected or connected by a linker peptide; and the Fc fragment does not have effector functions such as CDC, ADCC and ADCP.