Oportuzumab (commonly studied as Oportuzumab monatox or Vicineum) is a humanized recombinant fusion protein specifically targeting the epithelial cell adhesion molecule (EpCAM/CD326). It consists of a single-chain variable fragment (scFv) directed against EpCAM covalently linked to a truncated, modified fragment of Pseudomonas exotoxin A (ETA). EpCAM is significantly overexpressed in epithelial-derived malignancies, particularly bladder cancer. Oportuzumab binds specifically to the EpCAM protein on the tumor cell surface and is internalized via endocytosis, after which the toxin payload is released into the cytoplasm. The toxin irreversibly inhibits eukaryotic elongation factor 2 (eEF-2), thereby blocking protein synthesis and ultimately inducing apoptosis in cancer cells.