In what it is calling a strategic decision, Sesen Bio announced Monday that it has paused development activities of Vicineum, its lead asset, in the United States due to timeline and cost concerns.
Following a discussion with the U.S. Food and Drug Administration, Sesen said it will continue to evaluate other strategic alternatives that would maximize shareholder value. The company hopes halting research plans for Vicineum will allow it to conserve cash for operations and other initiatives, though it did not specify which. But Sesen is not totally pulling the plug on its lead drug. Instead, it is looking for a partner to push it forward.
"We continue to believe that Vicineum has benefits for patients and healthcare providers that can be maximized through a company with larger infrastructure, and as such, we intend to find a partner that can execute further development to realize the full potential of Vicineum,” Dr. Thomas Cannell, Sesen president and CEO, said in a statement.
Sesen has no outstanding debts and actually has $161.2 million in cash and cash equivalents as of June 30.
Vicineum is a locally administered fusion protein intended for the treatment of non-muscle invasive bladder cancer (NMIBC). The company has already completed the follow-up of its Phase III clinical trial in the U.S. for BCG-unresponsive NMIBC. The U.S. National Cancer Institute is also looking into combining the drug with AstraZeneca's durvalumab for the treatment of several cancers.
Sesen’s journey with Vicineum has not been without controversy. In August 2021, the company received a complete response letter from the FDA in which the regulator cited concerns associated with “drug substance and drug product manufacturing, cell bank, characterization, resin reuse, reference standards, methods, specifications, stability and microbiology." Sesen withdrew its marketing application authorization from the European Union shortly after.
On March 28, the company participated in a Type C meeting with the FDA, where the regulator agreed to most of the company’s proposed plan design elements and protocols for an additional Phase III trial to support a planned resubmission of a Biologics License Application in NMIBC. The two parties had agreed to meet again in mid-2022 to discuss the outstanding issues.
"We have had four 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 versus standard approval, single-arm versus randomized controlled trials, comparative versus non-comparative efficacy endpoints, and adequate versus less-than-adequate BCG patient populations," Cannell added.
All of the programs listed in Sesen’s pipeline involve Vicineum, including the aforementioned one in BCG-unresponsive high-risk NMIBC, and another for squamous cell carcinoma of the head and neck (SCCHN), in which the company has completed a Phase II trial.
However, Sesen does mention exploring the potential of a payload called deBouganin (VB6-845d), a plant toxin that is engineered to be de-immunized for systemic delivery in the treatment of multiple types of EpCAM-positive solid tumors. In January, Sesen received a milestone payment of $20 million in relation to its exclusive license agreement with Roche for a legacy interleukin-6 antagonist antibody technology that it owns.
