21 July 2021 - - The first patient has been enrolled in China in the clinical trial to assess the efficacy and safety of Vicineum in patients with BCG-unresponsive non-muscle invasive bladder cancer (NMIBC), US-based fusion protein therapeutics developer Sesen Bio (NASDAQ: SESN) and its partner in Greater China, Qilu Pharmaceutical said.

The milestone comes only four months after the Investigational New Drug application for Vicineum was approved by the Center for Drug Evaluation of the China National Medical Products Administration, which triggered a USD 3m milestone payment from Qilu Pharmaceutical, the first of USD 23m in potential milestone payments to Sesen Bio.

The open-label, single-arm, multi-center bridging trial will evaluate the efficacy and safety of Vicineum in approximately 53 patients with carcinoma in situ with or without papillary disease, high-grade Ta papillary disease or T1 papillary disease of any grade.

Patients will be required to have failed previous treatment with BCG for inclusion in the trial.

The primary endpoints are the complete response rate (for CIS patients) and the recurrence-free rate (for papillary patients) at six months, with the complete response rate and the recurrence-free rate at three months, safety and tolerability as the secondary endpoints.

Based on the partnership agreement between Sesen Bio and Qilu Pharmaceutical, the trial is being run at the sole cost of Qilu Pharmaceutical.

Assuming a successful trial, Qilu Pharmaceutical anticipates submission of the product market application for Vicineum in China in 2022, with potential approval expected in 2023.

Sesen Bio believes China represents a large potential market for Vicineum, with unadjusted peak year sales estimated at USD 155m-USD 418m.

In the US, the company believes it remains on track for an FDA decision on its Biologics License Application for Vicineum by the target PDUFA date of August 18, 2021.

Vicineum, a locally administered fusion protein, is Sesen Bio's lead product candidate being developed for the treatment of BCG-unresponsive non-muscle invasive bladder cancer (NMIBC).

Vicineum is comprised of a recombinant fusion protein that targets epithelial cell adhesion molecule (EpCAM) antigens on the surface of tumor cells to deliver a potent protein payload, Pseudomonas Exotoxin A.

Vicineum is constructed with a stable, genetically engineered peptide tether to ensure the payload remains attached until it is internalized by the cancer cell, which is believed to decrease the risk of toxicity to healthy tissues, thereby improving its safety.

In prior clinical trials conducted by Sesen Bio, EpCAM has been shown to be overexpressed in NMIBC cells with minimal to no EpCAM expression observed on normal bladder cells.

Sesen Bio is currently in the follow-up stage of a Phase 3 registration trial in the US for the treatment of BCG-unresponsive NMIBC.

In February 2021, the FDA accepted for filing the company's BLA for Vicineum for the treatment of BCG-unresponsive NMIBC and granted the application Priority Review with a target PDUFA date of August 18, 2021.

Additionally, Sesen Bio believes that cancer cell-killing properties of Vicineum promote an anti-tumor immune response that may potentially combine well with immuno-oncology drugs, such as checkpoint inhibitors.

For this reason, the activity of Vicineum in BCG-unresponsive NMIBC is also being explored at the US National Cancer Institute in combination with AstraZeneca's immune checkpoint inhibitor durvalumab.

Sesen Bio, Inc. is a late-stage clinical company advancing targeted fusion protein therapeutics for the treatment of patients with cancer.

The company's lead program, Vicineum, also known as oportuzumab monatox, is currently in the follow-up stage of a Phase 3 registration trial for the treatment of BCG-unresponsive non-muscle invasive bladder cancer (NMIBC).

In February 2021, the FDA accepted for filing the company's BLA for Vicineum for the treatment of BCG-unresponsive NMIBC and granted the application Priority Review with a target PDUFA date of August 18, 2021.

Sesen Bio retains worldwide rights to Vicineum with the exception of Greater China and the Middle East and North Africa, for which the company has partnered with Qilu Pharmaceutical and Hikma Pharmaceuticals, respectively, for commercialization.

Vicineum is a locally administered targeted fusion protein composed of an anti-EpCAM antibody fragment tethered to a truncated form of Pseudomonas Exotoxin A, which is being developed for the treatment of BCG-unresponsive NMIBC.

Qilu Pharmaceutical is a vertically integrated pharmaceutical company focused on discovering, developing, manufacturing and commercializing innovative medicines.

To date, Qilu Pharmaceutical has launched 200+ products with 30+ products "First to launch" in China and 3 products "D181 launch" in US.