FDA CRL for Sesen Bio’s Bladder Cancer Drug

 

Shares of Sesen Bio have plunged nearly 70% since Friday after the company announced the U.S. Food and Drug Administration rejected its lead candidate, Viceneum (oportuzumab monatox-qqrs) as a treatment for BCG-unresponsive non-muscle invasive bladder cancer (NMIBC).

In its Complete Response Letter, the FDA said it is unable to approve the company’s Biologics License Application for Vicineum in its present form. The regulatory agency recommended additional clinical and statistical data analyses, as well as issues related to the company’s Chemistry, Manufacturing and Controls (CMC). 

The FDA also expressed concern about drug substance and drug product manufacturing, cell bank, characterization, resin reuse, reference standards, methods, specifications, stability, and microbiology, the company said in a conference call on Monday.

In that call, Sesen chief executive officer Tomas Cannell expressed his disappointment in the FDA’s decision adding that the company will seek a Type A meeting with the regulatory agency to discuss the next steps regarding potential approval. Cannell said they anticipate the meeting will take place during the fourth quarter of this year. 

The CEO also discussed that the Type A meeting would be twofold. In addition to addressing the CMC concerns, Sesen will need to confirm the primary endpoints of clinical data. He said the endpoints should be Complete Response and Duration of Response. 

Additionally, they will need to confirm the trial size and how long the study will need to be. Cannell said the company will need a clear understanding of the FDA’s guidance expectations for the study. 

“I will add that we will need to better understand the Agency’s concerns in the context that if we do another clinical trial, we will be able to use drug substance and drug product from full-scale GMP commercial runs, and that should obviate the need to demonstrate analytical comparability, which was a large part of this submission,” Cannell said, according to a transcript of the call. Once we get this feedback from the FDA, we will provide you with guidance on this topic as quickly and transparently as possible.”

As of June 30, Sesen had $151.1 million in cash, cash equivalents and restricted cash. Cannell believes they have the available resources to conduct whatever study the FDA needs in order to gain regulatory approval for Vicenium.

In February, the FDA accepted the BLA for Vicenium under Priority Review. Vicenium is a recombinant fusion protein that targets epithelial cell adhesion molecule (EpCAM) antigens on the surface of tumor cells. It aims to deliver a potent protein payload of Pseudomonas Exotoxin A to the tumor.