• 3/29/2005
  • Toronto, Ontario, Canada
  • PRNewswire (www.prnewswire.com)

Viventia Biotech Inctoday reported preliminary results from an exploratory Phase I efficacy trial using direct intratumoral injection of Proxinium(TM) as a monotherapy for the treatment of patients with refractory head & neck cancer.

A total of 20 patients were enrolled in the study, of which 18 were considered evaluable at the end of the trial. Preliminary efficacy analysis showed that 25% of the 16 evaluable patients who expressed the therapeutic target for Proxinium(TM) had a complete response to therapy (complete disappearance of treated tumor); 63% had an objective response (significant or partial shrinkage of treated tumor); and 88% had tumor growth control (objective response or stabilization of disease). The drug was reported to have a good safety profile and was well tolerated, consistent with previous results.

“Current treatments for refractory head and neck cancer have shown limited efficacy. To have achieved such a high number of complete responses in patients that have, in essence, failed all other available therapies is very encouraging,” said Dr. Nick Glover, President and CEO of Viventia. “These results, and the promising survival data that emerged from our previous Phase I trial, show the tremendous potential for Proxinium(TM) for the treatment of refractory head and neck cancer. With the recent granting of Orphan Drug designation by the FDA, we are on track to initiate advanced clinical trials for Proxinium(TM) in 2005.”

Dr. Barry Wenig, Professor of Otolaryngology and Head and Neck Surgery, Northwestern University Medical School, and Director of the Division of Head and Neck Surgery, Evanston Northwestern Hospital, Chicago, a clinical adviser to the Company, independently evaluated the treatment sites employed in the study and, in an investigators’ meeting, participated in a review of each patient treated. Dr. Wenig commented “It appears that safety and efficacy issues were extremely well managed in the study. The results generated from a safety perspective are extremely encouraging with the safety profile being known. The results that were generated from an efficacy perspective appear to be significant and real. There was clearly a response of each tumor to injection of the drug, with some responses being dramatic.”

This exploratory efficacy Phase I trial tested Proxinium(TM) therapy using a more intensive dosing schedule than that employed in Viventia’s previously reported Phase I safety and tolerability clinical trial. The study, which was conducted in Brazil, enrolled 20 patients who had advanced head and neck cancer and continuing disease progression, with all patients having failed previous courses of surgery, chemotherapy and/or radiotherapy. The patients received a Proxinium(TM) injection directly into a target tumor on a weekly basis for four weeks. The trial was initiated in June 2004 and completed enrolment in January 2005. Complete results from this trial, including updated survival data, will be disclosed at the American Society of Clinical Oncology (ASCO) Annual Meeting in May 2005.

About Proxinium(TM)

Proxinium(TM) combines a powerful cytotoxic protein payload with the highly precise tumour-targeting characteristics of a monoclonal antibody. A single molecule of the cytotoxic protein payload, Pseudomonas exotoxin, is capable of killing a cancer cell. The antibody fragment of Proxinium(TM) targets EpCAM — a target that is highly expressed on many solid tumours including head & neck cancer, ensuring that the payload is delivered directly to the tumour.

Viventia completed a 24 patient Phase I safety and tolerability trial with a similar cohort of head and neck cancer patients in 2004. In this study, which was completed in Russia, Proxinium(TM) therapy yielded an objective response rate of 43% and a tumor growth control rate of 71% from those patients that expressed the EpCAM antigen. A recently completed analysis has determined that the median survival rate for EpCAM positive patients who showed a response to Proxinium(TM) in this study was 301 days, compared to a median survival of 125 days for those patients that were EpCAM negative (the expected median survival is approximately 120-150 days). Commenting on these data, Dr. Glover stated, “Existing therapeutic options are essentially palliative in this patient population, with no approved agent having demonstrated an ability to confer a survival benefit. These median survival data, while preliminary, suggest that Proxinium(TM) therapy may be associated with an improvement in survival for the treatment of refractory head and neck cancer patients, which is a very promising and exciting development.”

Proxinium(TM) received U.S. Orphan Drug designation from the FDA for the treatment of head and neck cancer in March 2005. Head and neck cancer is the 9th most common cancer in North America, with approximately 50,000 new cases diagnosed annually in the U.S. alone, leading to 14,000 deaths annually. Head and neck cancer recurs in 60 – 70% of patients. The historical median survival time for patients with advanced, refractory head & neck cancer is less than six months.