Leading cancer journals publish OncoGenex's custirsen pre-clinical and Phase II study data

OncoGenex Pharmaceuticals, Inc. (NASDAQ: OGXI) announced today that data from two studies, a Phase II clinical study and a pre-clinical study, evaluating the investigational compound custirsen (OGX-011/TV-1011), were published in the September issues of the journals Clinical Cancer Research and Cancer Research.

Custirsen inhibits the production of clusterin, a protein commonly over-produced in cancer cells and a cause of treatment resistance. Two Phase III studies evaluating custirsen in men with castrate-resistant prostate cancer (CRPC) are ongoing: the SYNERGY clinical trial - designed to evaluate an overall survival benefit for custirsen in combination with first-line docetaxel treatment, and the Prostate Cancer SATURN Trial - which will evaluate a durable pain palliation benefit in patients receiving second-line chemotherapy. Both studies are currently enrolling CRPC patients.

Phase II Data Published in Clinical Cancer Research

Data from a Phase II clinical study of custirsen in combination with docetaxel retreatment or mitoxantrone as second-line chemotherapy in patients with metastatic castrate-resistant prostate cancer (mCRPC) was published in the September 1, 2011 issue of Clinical Cancer Research.

In the clinical study, custirsen combined with docetaxel retreatment resulted in overall survival of 15.8 months. When custirsen was combined with mitoxantrone, overall survival was 11.5 months. The Phase II study also evaluated pain responses in patients with mCRPC. Overall, the pain response was durable (greater than or equal to three months) in 88 percent of patients who had pain or were on opioids for pain at study entry.

"These are encouraging results because we observed durable pain responses in many patients who had disease progression while on or shortly after first-line docetaxel treatment," said Dr. Fred Saad, Professor of Surgery/Urology at the University of Montreal and lead investigator on the study. "These data suggest that custirsen may restore docetaxel sensitivity and potentially provide improvements in pain control for this difficult-to-treat patient population."

The authors concluded that the study's results, which demonstrated feasibility, safety and pain relief, as well as an association of low serum clusterin levels with longer survival, provides a consistent signal that warrants further testing of custirsen combined with second-line chemotherapy in mCRPC.

Pre-Clinical Data Published in Cancer Research

Pre-clinical data published in the September 1, 2011 issue of Cancer Research, demonstrated that clusterin inhibition using custirsen synergistically enhanced Heat-shock 90 (Hsp90) inhibitor activity by suppressing the heat shock response in CRPC.

Heat-shock 90 (Hsp 90) inhibitors trigger the elevation of compensatory survival mechanisms that result in the production of clusterin, leading to cancer cell survival and treatment resistance. Results of this study demonstrated that when custirsen was combined with the Hsp90 inhibitor PF-04929113 or 17-AAG, the compounds worked synergistically to inhibit CPRC tumor cell growth in mice.

"These data support the broad, potential applicability of custirsen in combination with various anti-cancer treatments," said Dr. Martin Gleave, Director of The Vancouver Prostate Centre at The University of British Columbia and researcher on the study. "This study is an example of how we continue to develop a greater understanding of cancer treatment resistance and identify opportunities to block these mechanisms in order to delay tumor progression."