Claudin-18(CLDN18) is a protein that in humans is encoded by the CLDN18 gene. It belongs to the group of claudins. CLDN18 belongs to the large claudin family of proteins, which form tight junction strands in epithelial cells. CLDN18 plays a major role in tight junction-specific obliteration of the intercellular space, through calcium-independent cell-adhesion activity. CLDN18 has two isoform A1 and isoform A2. IMAB362 (Claudiximab) is a monoclonal antibody against isoform 2 of Claudin-18. It is under investigation for the treatment of gastrointestinal adenocarcinomas and pancreatic tumors. IMAB362 was developed by Ganymed Pharmaceuticals AG.