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# FDA Sends Sesen Bio a Complete Response Letter
- URL: https://www.fdaweb.com/fda-sends-sesen-bio-a-complete-response-letter/
- Published: 2021-08-13T12:00:00.000Z
- Updated: 2026-09-14T17:10:31.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5149935

**FDA has issued Sesen Bio** a complete response letter on its BLA for Vicineum (oportuzumab monatox-qqrs) for treating bacillus Calmette-Guérin-unresponsive non-muscle invasive bladder cancer. The agency’s letter requested additional clinical/statistical data and analyses, in addition to citing chemistry, manufacturing and controls issues related to a recent pre-approval inspection and product quality, the company says.  

Vicineum is described as a recombinant fusion protein that targets epithelial cell adhesion molecule (EpCAM) antigens on the surface of tumor cells to deliver a potent protein payload, *Pseudomonas Exotoxin A*.