Oncothyreon Presents Preclinical Data for ONT-10 and PX-866 at American Association for Cancer Research

SEATTLE, WA, April 4 /PRNewswire-FirstCall/ - Oncothyreon Inc. (Nasdaq: ONTY) today announced the presentation of preclinical data for ONT-10, a therapeutic vaccine directed at cancers expressing MUC1, and PX-866, its irreversible inhibitor of phosphatidylinositol 3-kinase (PI3K), at the American Association of Cancer Research meeting in Orlando, Florida.

ONT-10

ONT-10 is a therapeutic vaccine targeting MUC1 which has been designed to stimulate both the humoral and cellular arms of the immune response.  Results presented at the meeting demonstrated that administration of ONT-10 produced a robust antibody response in mice that was specific for human tumor MUC1.  A strong cellular immune response directed to the target was also shown.  ONT-10 blocked the growth of two different tumors expressing human MUC1 in murine models, with a high proportion of animals tumor free at the conclusion of the experiment.  Additionally, the adjuvant component of ONT-10, PET-Lipid A, a fully synthetic toll like receptor 4 (TLR4) agonist discovered by Oncothyreon, was shown to have enhanced potency compared to the adjuvant monophosphoryl lipid A (MPL).

"These preclinical data validate our hypothesis that the antigen present in ONT-10 stimulates both effector arms of the immune response," said Scott Peterson, Ph.D., Vice President of Research and Development at Oncothyreon.  "We are looking forward to beginning our first clinical trial with ONT-10 late this year with a goal of replicating these data in man."

PX-866

PX-866 is an oral, small molecule compound designed to inhibit the activity of PI3K, a component of an important cell survival signaling pathway. Data presented at the meeting concerned the efficacy of PX-866 alone or in combination with either docetaxel or cetuximab in direct patient human tumor xenograft models (DPTM) of squamous cell carcinoma of the head and neck (SCCHN) developed by Dr. Antonio Jimeno's laboratory at University of Colorado School of Medicine.  These models maintain the histology of the tumor and are particularly suited to preclinical evaluation of novel cancer therapeutics.  PX-866 was equal or superior to docetaxel in slowing tumor growth in two of four DPTM and equal or superior to cetuximab in each of four DPTM. The combination of PX-866 plus docetaxel was superior to single agent therapy in three of four DPTM, while the combination with cetuximab was superior to single agent therapy in two of four DPTM.  The data were presented by Daniel W. Bowles, M.D., University of Colorado School of Medicine, Aurora, Colorado.

"These data are strongly supportive of our ongoing Phase 1/2 trials of PX-866 in combination with either docetaxel or cetuximab," said Diana Hausman, M.D., Vice President of Clinical Development at Oncothyreon. "The Phase 2 portion of each of these trials includes an arm enrolling patients with SCCHN."

About ONT-10

ONT-10 is a therapeutic vaccine targeting MUC1, a tumor-associated antigen present on many types of human malignant tumors, including lung, breast, colorectal, prostate and ovarian cancer.  ONT-10 contains a forty three amino acid antigen which is glycosylated; the attached sugars are expected to contribute to the stimulation of an immune response to the vaccine.  The adjuvant in ONT-10 is PET Lipid A, a fully synthetic TLR4 agonist developed at Oncothyreon.  Oncothyreon currently expects to file an Investigational New Drug application for ONT-10 in the third quarter of 2011 and to begin a Phase 1 clinical trial by late 2011.  ONT-10 and PET Lipid A are fully owned by Oncothyreon.

About PX-866

PX-866 is a 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). Results from a single-agent Phase 1 open-label, dose escalation study of PX-866 in patients with advanced metastatic cancer demonstrated that PX-866 was well tolerated using both an intermittent and continuous (daily) dosing schedule.   Additional data from the Phase 1 trial presented at the EORTC/NCI/AACR meeting in Berlin on November 18, 2010 demonstrated that 8 of 19 evaluable patients treated with continuous dosing achieved stable disease as their best response.

Oncothyreon is conducting a broad development program of PX-866 including clinical trials evaluating the compound as a single agent and in combination with other agents in multiple cancer types. Current trials include a Phase 1/2 trial of PX-866 in combination with cetuximab (Erbitux®) in patients with progressive metastatic colorectal carcinoma (CRC) or progressive, recurrent or metastatic SCCHN and a Phase 1/2 trial of PX-866 in combination with the chemotherapeutic agent docetaxel in patients with advanced cancers for which docetaxel is considered standard of care.  In addition, the National Institute of Canada Clinical Trials Group is expected to initiate two Phase 2 trials of PX-866, one in patients with castration-resistant prostate cancer and the second in patients with relapsed glioblastoma.

About Oncothyreon

Oncothyreon is a biotechnology company specializing in the development of innovative therapeutic products for the treatment of cancer. Oncothyreon's goal is to develop and commercialize novel synthetic vaccines and targeted small molecules that have the potential to improve the lives and outcomes of cancer patients. For more information, visit www.oncothyreon.com.

Forward Looking Statements

In order to provide Oncothyreon's investors with an understanding of its current intentions and future prospects, this release contains statements that are forward looking, including statements related to future preclinical and clinical development plans for our product candidates. These forward-looking statements represent Oncothyreon's intentions, plans, expectations and beliefs and are based on its management's experience and assessment of historical and future trends and the application of key assumptions relating to future events and circumstances.

Forward-looking statements involve risks and uncertainties, including risks and uncertainties related to Oncothyreon's business and the general economic environment. Many of these risks and uncertainties are beyond Oncothyreon's control. These risks, uncertainties and other factors could cause our actual results to differ materially from those projected in forward-looking statements. Risks, uncertainties, and assumptions include those predicting the timing, duration and results of clinical trials, the timing and results of regulatory reviews, the safety and efficacy of our product candidates, and the indications for which our product candidates might be developed. There can be no guarantee that the results of preclinical studies or clinical trials will be predictive of either safety or efficacy in future clinical trials. These and other risks and uncertainties are described in the reports and other documents filed by Oncothyreon Inc. with the SEC and/or Canadian regulatory authorities.

Although Oncothyreon believes that any forward-looking statements contained herein are reasonable, it can give no assurance that its expectations are correct. All forward-looking statements are expressly qualified in their entirety by this cautionary statement. For a detailed description of the risks and uncertainties associated with Oncothyreon, you are encouraged to review the official corporate documents filed with the securities regulators in the United States on U.S. EDGAR and in Canada on SEDAR. Oncothyreon is under no obligation to (and expressly disclaims any such obligation to) update or alter its forward-looking statements whether as a result of new information, future events, or otherwise.

SOURCE Oncothyreon Inc.

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