Definition

A bispecific antibody directed against the tumor-associated antigen (TAA) Claudin18.2 (CLDN18.2; A2 isoform of claudin-18) and the human T-cell surface antigen CD3, with potential immunostimulatory and antineoplastic activities. Upon administration, anti-CD3/anti-CLDN18.2 bispecific antibody IBI389 simultaneously binds to both CD3-expressing T cells and CLDN18.2-expressing cancer cells, thereby crosslinking CLDN18.2-expressing tumor cells and cytotoxic T lymphocytes (CTLs). This results in the activation and proliferation of T cells and causes CTL-mediated cell lysis of CLDN18.2-expressing tumor cells. CLDN18.2, a tight junction protein and stomach-specific isoform of claudin-18, is expressed on a variety of tumor cells. Its expression in healthy tissues is strictly confined to short-lived differentiated epithelial cells of the gastric mucosa.