Chemically, oportuzumab is a single chain variable fragment of a monoclonal antibody which binds to epithelial cell adhesion molecule (EpCAM, the tumor-associated calcium signal transducer 1).

Oportuzumab is fused with Pseudomonas aeruginosa exotoxin A (which is reflected by the monatox in the medication's name).

The company was acquired by Cambridge(MA)-based Eleven Biotherapeutics in 2016, which then changed its name to Sesen Bio.

[2] In 2019 Sesen Bio reported updated, preliminary primary and secondary endpoint data from the company's Phase 3 VISTA trial further supporting the strong benefit-risk profile of Vicineum for the potential treatment of patients with high-risk, bacillus Calmette-Guérin(BCG) unresponsive, non-muscle invasive bladder cancer (NMIBC).

[3] The Company applied for approval of Vicineum by the United States Food and Drug Administration and the European Medicines Agency.