Oncothyreon Announces Initiation of Phase 1 Trial of ONT-380 in Combination with Trastuzumab in Patients with Brain Metastases from HER2+ Breast Cancer

SEATTLE, WA, Sept. 3, 2013 /PRNewswire/ - Oncothyreon Inc. (NASDAQ: ONTY) today announced the initiation of an investigator-sponsored trial of ONT-380 in combination with trastuzumab (Herceptin®) in patients with brain metastases from HER2+ breast cancer.  The trial is being conducted under the sponsorship of the Dana-Farber Cancer Institute, Boston, Massachusetts.  ONT-380 (also known as ARRY-380) is an orally active, reversible and selective small-molecule HER2 inhibitor being developed by Oncothyreon in collaboration with Array BioPharma Inc., Boulder, Colorado.

The Phase 1 trial is a dose-escalation trial in up to 50 patients.  The primary objectives are to determine the maximum-tolerated dose and recommended Phase 2 dose and schedule of ONT-380 in combination with trastuzumab in patients with HER2+ breast cancer and central nervous system (CNS) metastases.  Secondary objectives include CNS objective response rate by both RECIST and volumetric criteria, progression-free survival and overall survival.  The study will be conducted in two parallel arms with two dose regimens of ONT-380, either once-daily or twice-daily, in combination with standard dose trastuzumab.

"ONT-380 has demonstrated superior activity, based on overall survival, compared to Tykerb^® (lapatinib) and to the investigational drug, neratinib, in an intracranial HER2+ breast cancer xenograft model," said Robert L. Kirkman, M.D., President and CEO of Oncothyreon. "This provides a strong rationale to explore whether ONT-380 can provide benefit to patients with brain metastases, and we are pleased that the Dana Farber Cancer Institute is undertaking this trial."

"CNS metastases, which occur in one-third to one-half of women with metastatic HER2+ breast cancer, remain a significant clinical problem," said Nancy U. Lin, M.D., Principal Investigator of the Phase 1 trial and Clinical Director, Breast Oncology, Dana-Farber Cancer Institute.  "There is an urgent need for new therapies to treat patients with brain metastases from breast cancer, and we are excited to begin this study of ONT-380".

About ONT-380

ONT-380 is an orally active, reversible and selective HER2 inhibitor. In multiple preclinical tumor models, ONT-380 was well tolerated and demonstrated significant dose-related tumor growth inhibition that was superior to Herceptin and Tykerb. Additionally, in these models, ONT-380 demonstrated synergistic or additive tumor growth inhibition when dosed in combination with the standard-of-care therapeutics Herceptin or Taxotere® (docetaxel).

A Phase 1 trial of ONT-380, with both dose-escalation and expansion components, has been completed in 50 patients, 43 of whom had HER2+ metastatic breast cancer. All HER2+ breast cancer patients had progressed on a trastuzumab-containing regimen. In addition, over 80% had been treated with lapatinib, with many having progressed on therapy. In this study, ONT-380 demonstrated an acceptable safety profile; treatment-related adverse events were primarily Grade 1. Because ONT-380 is selective for HER2 and does not inhibit EGFR, there was a low incidence and severity of treatment-related diarrhea, rash and fatigue. Additionally, there were no treatment-related cardiac events or Grade 4 treatment-related adverse events reported. The maximum tolerated dose of ONT-380 established in this Phase 1 trial was 600 mg twice daily (BID). Twenty-two HER2+ breast cancer patients with measurable disease were treated with ONT-380 at doses greater than or equal to 600 mg BID. In this heavily pretreated patient population, there was a clinical benefit rate (partial response [n = 3] plus stable disease for at least 6 months [n = 3]) of 27%. Notably, two of the patients with partial responses during treatment with ONT-380 had confirmed progressions while on prior lapatinib- and trastuzumab-containing regimens.

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

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Forward-looking statements involve risks and uncertainties related to Oncothyreon's business and the general economic environment, many of which are beyond its control. These risks, uncertainties and other factors could cause Oncothyreon's actual results to differ materially from those projected in forward-looking statements, including 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. Although Oncothyreon believes that the 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 Oncothyreon's risks and uncertainties, you are encouraged to review the documents filed with the securities regulators in the United States on EDGAR and in Canada on SEDAR. Oncothyreon does not undertake any obligation to publicly update its forward-looking statements based on events or circumstances after the date hereof.

Additional Information

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SOURCE Oncothyreon Inc.