FDA Does Not Approve Vicinium for BCG-unresponsive NMIBC

The FDA has issued a complete response letter (CRL) to Sesen Bio, denying the approval of the Biologics License Application (BLA) for Vicinium (oportuzumab monatox-qqrs) for the treatment of BCG-unresponsive non-muscle invasive bladder cancer (NMIBC)¹, which the regulatory body had previously granted priority review², announced Sesen Bio, in a press release.¹

Additional clinical and statistical data and analyses are being requested by the FDA to potentially approve the agent for this indication in the future. In addition, the CRL noted Chemistry, Manufacturing and Controls issues that need to be addressed.

“We are deeply disappointed by this unexpected result, and it is an unfortunate day for patients suffering from BCG-unresponsive NMIBC,” said Thomas Cannell, president, and chief executive officer of Sesen Bio. “We remain dedicated to our mission to save and improve the lives of patients by bringing new treatment options to patients, and we intend to work closely with the FDA to understand next steps.”

Vicinium, a recombinant fusion protein, blocks protein synthesis in order to mediate tumor cell death. It is currently being investigated across several solid tumor types.

The approval was based on the results of a phase 3 study that has an estimated enrollment of 134 participants. The primary outcome of the study was complete response rate up to 24 months. Secondary outcome measures include recurrence rate, event-free survival, number of patients with adverse events as a measure of tolerability, changes in echocardiogram, changes in vital signs from baseline, changes in laboratory or physical examination, complete response rate, time to cystectomy, time to disease recurrence, time to progression, progression-free survival (PFS), and overall survival (OS).^1,3

During the single-arm study, patients received 30mg of Vicinium in 50ml of saline, twice weekly for 6 weeks followed by once weekly for 6 weeks. After the 12-week induction period, patients received maintenance Vicinium in 50 ml of saline administered once weekly every other week up to 104 weeks.³

In order to participate, patients must have histologically-confirmed non-muscle-invasive urothelial carcinoma of the bladder, have refractory disease after adequate BCG treatment, adequate organ function, and have received adequate BCG treatment. Patients who are breastfeeding or pregnant, have evidence of urethral or upper tract transitional cell carcinoma within 2 years, or any intravesicular or other chemotherapy treatment within 2 weeks or an investigation agent within 4 weeks prior to the initial dose of the study are not eligible to participate.

The 3-month complete response rate of 40%. The median DoR was 9.4 months (95% CI, 5.1 to not evaluable [NE]). Among patients who responded, 52% remained disease free for 12 months after treatment began. The 2-year overall survival rate was (96% 95% CI, 92%-100%).

The majority of adverse events (AEs) observed were grades 1 and 2. Severe AEs included grade 4 cholestatic hepatitis, grade 5 renal failure, grade 3 acute kidney injury, and grade 2 pyrexia. Of the patients, 3% discontinued treatment due to AEs.

A phase 3 follow-up trial, VISTA study (NCT02449239), of the trial is currently underway to further investigate the efficacy and safety of NCT02449239. A Type A meeting with the FDA will be requested by Sesen Bio as soon as to discuss the steps needed to get the Vicinium FDA approved for the treatment of BCG-unresponsive NMIBC.¹

 _References:

_{1. Sesen Bio receives complete response letter from fda for Vicineum™ (oportuzumab monatox-qqrs). News release. Sesen Bio. August 13. 2021. Accessed August 16, 2021. https://bit.ly/3xQdt1e}

_{2. Sesen Bio Announces FDA Acceptance and Priority Review of its Biologics License Application for Vicineum™. News release. Sesen Bio. February 16, 2021. Accessed February 17, 2021. https://bit.ly/37pBstN}

_{3. Shore N, O’Donnell M, Keane T, et al. PD03-02 Phase 3 results of Vicinium in bcg-unresponsive non-muscle invasive bladder cancer. J Urol. 2020; 203(suppl 4). doi: 10.1097/JU.0000000000000823.02}