Sesen Bio, after years on the edge of irrelevancy, scores speedy review for long gestating bladder cancer program
After years spent in the penny stock range, Sesen Bio has nabbed a long-awaited FDA review for its antibody-drug conjugate bladder cancer program.
The FDA will give an accelerated audit to Sesen and its bladder cancer candidate Vicineum, an antibody-drug conjugate acquired in the company’s buyout of Toronto-based Viventia back in 2016. Sesen is penciled in for an Aug 18 PDUFA, and there is no adcomm on the docket right now, the company said.
“We have been meeting with the FDA regularly for the past two years on the application for Vicineum,” CEO Thomas Cannell said in a statement. “We understand the FDA’s position and guidance very clearly and have found the review process to be collaborative and engaging.”
News of the priority review ostensibly pleased investors, sending Sesen $SESN shares up more than 10% in early Tuesday trading.
The idea behind the experimental drug is to use a recombinant fusion protein, attached to a genetically engineered peptide, to target specific antigens on the surface of tumor cells. It seeks out what are called epithelial cell adhesion molecule antigens, or EpCAM, that are overexpressed in NMIBC and uses the peptide tether to allow for minimal spillover toxicity.
Sesen applied for Vicineum to treat high-risk, BCG-unresponsive non-muscle invasive bladder cancer and submitted data from a 133-patient Phase III trial, which is still conducting the follow-up stage. Patients in the single-arm Phase III trial had previously been on BCG immunotherapy, a standard treatment that doesn’t always work.
The most recent batch of efficacy data, which came from 93 patients with cancer that had not spread from the bladder into muscle or other tissue, showed the program had a complete response rate of 39% after three months. Later data also showed complete responses at the 6-, 9- and 12- month periods. Respectively, those time frames resulted in rates of 28%, 21% and 15%.
The program’s safety data, which appeared to spook investors three years ago when top-line results were first released, showed that 78% of side effects were designated as Grade 1 or Grade 2. But there were four treatment-related side effects noted at the time, including acute kidney injury, renal failure and cholestatic hepatitis.
Those events, which sent the company’s stock down about 23% after the initial announcement, don’t seem to have regulators worried, however.
With Tuesday’s news, Sesen is preparing to submit data to European regulators in the next one to two months. The company is also waiting to hear back from Chinese health authorities over a possible approval of their IND application.
Bladder cancer isn’t the only area Sesen is seeking to treat with Vicineum. The company is also looking at squamous cell carcinoma of the head and neck, having completed a Phase II trial in the US. Sesen is also looking at Vicineum combination partners, studying the program with AstraZeneca’s Imfinzi in the same indication as the NMIBC monotherapy.
The candidate has given Sesen new life after its former lead program failed twice and it completed a deal to license out its remaining program to Roche.