Definition

A bispecific T-cell engager (BiTE) antibody composed of two single-chain variable fragments (scFv), one directed against the B-cell-specific membrane protein CD19, and another that is directed against the CD3 antigen found on T lymphocytes, with potential immunostimulating and antineoplastic activities. Upon administration, anti-CD19/CD3 BiTE antibody AMG 562 binds to both the CD3 antigen on cytotoxic T lymphocytes (CTLs) and the CD19 antigen expressed on malignant B cells. This activates and redirects CTLs to CD19-expressing tumor cells, resulting in CTL-mediated killing of tumor cells. CD19 is a membrane antigen that is widely expressed during B-cell development, from pro-B-cell to early plasma cell stages.