Sesen Bio has decided to pause clinical development of Vicineum™ (oportuzumab monatox-qqrs) for the treatment of bacillus Calmette-Guérin (BCG)-unresponsive non-muscle invasive bladder cancer (NMIBC).

Vicineum is an investigational locally administered recombinant fusion protein that targets epithelial cell adhesion molecule antigens on the surface of tumor cells to deliver Pseudomonas Exotoxin A. The fusion protein design is expected to reduce the risk of toxicity to healthy tissue, thereby improving safety. 

The Biologics License Application (BLA) for Vicineum included preliminary findings from the phase 3 VISTA trial ( Identifier: NCT02449239), which demonstrated a strong benefit-risk profile for Vicineum in 133 adults with high-risk, BCG-unresponsive NMIBC. 

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In August 2021, the Food and Drug Administration (FDA) issued a Complete Response Letter (CRL) to Sesen Bio requesting additional clinical and statistical data and analyses for Vicineum prior to another review. The Agency also noted CMC (Chemistry, Manufacturing and Controls) issues pertaining to a recent pre-approval inspection. 

The decision to pause further development in the United States was made after a reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional phase 3 clinical trial.

“We have had 4 productive meetings with the FDA since August 2021 and we believe we have a full understanding of the FDA’s evolving position and guidance on the following variables: accelerated vs standard approval, single-arm vs randomized controlled trials, comparative vs noncomparative efficacy endpoints, and adequate vs less-than-adequate BCG patient populations,” said Dr Thomas Cannell, president and chief executive officer of Sesen Bio. “We have also recently observed an evolution of the current treatment paradigm in NMIBC, with substantial uptake of intravesical chemotherapy (monotherapy and combination therapy) during the ongoing BCG shortage. In assessing the impact of the regulatory and commercial landscape, we have made the decision to pause the clinical development of Vicineum.”

Sesen Bio intends to seek a partner for further development of Vicineum.


Sesen Bio announces strategic decision to pause clinical development of Vicineum™ in the US. News release. Sesen Bio. Accessed July 18, 2022.

This article originally appeared on MPR