Viventia Bio Inc., a late clinical-stage company advancing a broad pipeline of novel anti-cancer agents, announced that it has begun approving clinical trial centres for participation in its pivotal phase 3 human clinical trial for Vicinium (VB4-845), a recombinant fusion protein which is being developed for treatment of high grade non-muscle invasive bladder cancer (NMIBC).

Based on discussions with the US Food and Drug Administration, Viventia has finalised its clinical protocol and plans to start enrolling patients next month at multiple sites in the US and Canada. Preliminary efficacy data from the trial are expected in the third quarter of 2016.

"We are excited to launch patient enrollment imminently for Vicinium, a highly differentiated, wholly biologic targeted protein therapeutic designed to overcome the challenges and deficiencies of earlier-generation antibody drug conjugates," said Stephen Hurly, Viventia's chief executive officer.

"Vicinium has been administered to more than 100 patients in phase 1 and 2 clinical trials. Clinical results to date have demonstrated complete response rates of greater than 40 per cent at 3 months with no drug-related serious adverse events." The findings were published in the Journal of Urology

Glen MacDonald, Viventia's chief science officer added "No effective new drugs for high grade NMIBC have been approved in the past 25 years, and failure rates are high for current treatment of these patients. We are encouraged that our clinical trial data for Vicinium holds great promise for patients who have failed the standard treatment, BCG. As a targeted therapy, Vicinium is able to target the cancer cells directly and has to date avoided systemic toxicity. With a strong combination of efficacy and safety we look forward to driving the product development forward."

Viventia's open-label, multi-centre phase 3 clinical trial will assess efficacy and tolerability of intravesical administration of Vicinium in patients with high grade NMIBC (carcinoma in situ and/or papillary disease) refractory to treatment with Bacillus Calmette–Guérin (BCG). The trial will be conducted at approximately 55 leading medical centres in the United States and Canada.

NMIBC is the second most common malignancy of the genitourinary system in the US, accounting for 70-80 per cent of all bladder cancers, and the sixth most common cancer diagnosed. It is estimated that there will be 74,000 new cases of bladder cancer in the US and 16,000 deaths in the US in 2015, according to the Surveillance, Epidemiology and End Results Programme (SEER) of the National Cancer Institute. BCG was approved to treat NMIBC carcinoma in situ in 1990. As a front-line therapy, BCG, with or without transurethral resection of the bladder tumour (TURBT), is associated with high failure rates: 50 per cent within one year and 90 per cent within five years.

A recombinant fusion protein, Vicinium consists of a single chain EpCAM-targeting antibody fragment genetically fused to truncated Pseudomonas exotoxin, or exotoxin A (ETA). Vicinium targets and binds to cancer cells expressing EpCAM, a protein exclusively associated with epithelium and overexpressed on many epithelial cancers. Once bound, Vicinium is internalised and migrates within the cancer cell, where its toxin payload dissociates from the single chain antibody fragment and is then able to exert its cancer cell-killing activity. Vicinium is administered by direct instillation into the urinary bladder (intravesical delivery), consistent with current treatment paradigm for BCG. In addition, Vicinium's mechanism of action is complementary to use with chemotherapeutics or immune modulators.