Oncothyreon Inc.,a biotechnology company specializing in the development of innovative therapeutic products for the treatment of cancer, is planning to expand the ongoing phase 2 trial of PX-866 in patients with recurrent or metastatic castration-resistant prostate cancer to include an additional group of up to 25 patients whose disease has begun to progress while receiving abiraterone (Zytiga) and prednisone. PX-866 is Oncothyreon's small molecule compound designed to inhibit the activity of phosphatidylinositol-3-kinase (PI-3K), a component of an important cell survival signaling pathway.

The open label phase II trial is being conducted by the NCIC Clinical Trials Group (NCIC CTG), Queen's University in Kingston, Canada. The initial part of this trial (Part A) has enrolled approximately 36 of a planned 40 patients with progressive castration-resistant prostate cancer who have received no prior chemotherapy. Part A included an interim efficacy analysis after enrollment of the first 23 patients, which was met. Enrollment of Part B of the trial will commence following full enrollment in Part A. Part B will enroll patients who demonstrate disease progression while receiving abiraterone as evidenced by a rising prostate specific antigen (PSA). PX-866 will be administered in addition to continuing treatment with abiraterone and prednisone. The primary endpoint of each part of this single-arm screening trial is the proportion of patients with lack of disease progression at 12 weeks from the initiation of therapy with PX-866.

"We appreciate the support and interest of the NCIC CTG in PX-866, our novel, irreversible PI-3K inhibitor, as demonstrated by the expansion of this phase II trial in prostate cancer," said Robert L Kirkman, MD, president and CEO of Oncothyreon. "This trial is an important component of our broad phase II programme for PX-866, intended to provide significant information to guide later stage development of this product candidate."

PX-866 is an irreversible pan inhibitor of the PI-3K/PTEN/AKT pathway, a critical cell signaling pathway that is activated in many types of human cancer. Aberrant activation and regulation of PI-3K is implicated in a large proportion of human cancers, where it leads to increased proliferation and inhibition of apoptosis (programmed cell death).

Oncothyreon is conducting a broad development program of PX-866 as a single agent and in combination with other agents in multiple cancer types. Current trials include a phase I/II trial of PX-866 in combination with cetuximab (Erbitux) in patients with metastatic colorectal carcinoma or progressive, recurrent or metastatic squamous cell carcinoma of the head and neck (SCCHN), a phase I/II trial of PX-866 in combination with the chemotherapeutic agent docetaxel in patients with locally advanced, recurrent or metastatic non-small cell lung cancer or SCCHN, and a phase I/II trial of PX-866 in combination with vemurafenib in patients with BRAF mutant cancer. In addition, the NCIC Clinical Trials Group is conducting two phase II trials, the trial in patients with recurrent or metastatic castration- resistant prostate cancer described above and a trial in patients with glioblastoma multiforme that has recurred during or following primary therapy.

The NCIC Clinical Trials Group (NCIC CTG) is a cancer clinical trials cooperative group that conducts phase I-III trials testing anti-cancer and supportive therapies across Canada and internationally. It is one of the national programmes and networks of the Canadian Cancer Society Research Institute (CCSRI), and is supported by the CCSRI with funds raised by the Canadian Cancer Society (CCS). The NCIC CTG's Central Office is located at Queen's University in Kingston, Ontario, Canada.