Sesen Bio Inc. (NASDAQ: SESN) shares took a beating on Thursday despite posting positive data for its late-stage trial for patients with high-grade non-muscle invasive bladder cancer who have been previously treated with bacillus Calmette-Guérin (BCG) and deemed BCG-unresponsive.

Overall, the data reported show clinically meaningful complete response rates in evaluable Carcinoma in situ patients at three, six, nine and 12 months of follow-up in the trial consistent with the data in the completed Phase 1 and Phase 2 clinical trials. Importantly, Vicinium continues to be generally well-tolerated in treated patients.

Sesen also reported an update on the durability of responses in the Vista trial. While the median has not yet been reached, the preliminary data show that Vicinium treatment resulted in a prolonged duration of response in many patients. This is particularly notable given that, in order for patients to remain on study, they have to have achieved a complete response at each assessment time period. These findings suggest that Vicinium has the potential to benefit patients by delaying the time to a radical cystectomy, a secondary endpoint that will be measured and reported in mid-2019.

The Vista Trial completed enrollment in the second quarter of 2018, and complete 12-month efficacy data from all patients in the clinical trial are expected to be reported at a medical meeting in mid-2019.

Michael A.S. Jewett, M.D., Professor of Surgery, Division of Urology, University of Toronto, commented:

Non-muscle invasive bladder cancer is a very prevalent cancer that can progress to become incurable. The usual treatment for patients who relapse or become refractory to BCG, today’s standard-of-care, is complete bladder removal or radical cystectomy. Removing the bladder is a potentially morbid and complex surgery with potential for side effects that can drastically reduce a patient’s quality of life. In fact, many patients choose not to undergo bladder removal. I am very encouraged by the data generated to-date with intravesical Vicinium as an alternative after BCG failure. Based on the strength of the clinical activity observed, and the consistently favorable safety and tolerability, I believe that Vicinium has the potential to change the treatment outcome for patients.

Shares of Sesen were last seen down 33% at $0.98, in a 52-week range of $0.76 to $3.50. The consensus analyst price target is $5.00.

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