Oncothyreon Announces Presentation of Final Results from Phase 1 Trial of ONT-380

SEATTLE, WA, Oct. 7, 2013 /PRNewswire/ - Oncothyreon Inc. (NASDAQ: ONTY) today announced the presentation of final results from the first Phase 1 trial of ONT-380 at the American Association for Cancer Research Special Conference on Advances in Breast Cancer Research in San Diego.  The results were presented by Virginia F. Borges, M.D., Associate Professor in the Division of Medical Oncology, University of Colorado School of Medicine.  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. (Nasdaq:  ARRY), Boulder, Colorado.

The first-in-human Phase 1 trial, with both dose-escalation and expansion components, enrolled a total of 50 patients, 43 of whom had HER2+ metastatic breast cancer.  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, side effects which have been associated with EGFR inhibition.  A single patient experienced Grade 2 treatment-related diarrhea and no patient developed treatment-related Grade 3 diarrhea; one patient had a Grade 3 rash. 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.  The dose-limiting toxicity was reversible elevation in liver enzymes.

In this trial, 22 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.

"We believe that ONT-380's selectivity for HER2, without also targeting EGFR, positions ONT-380 as a potential best-in-class small molecule HER2 inhibitor," said Robert L. Kirkman, M.D., President and Chief Executive Officer of Oncothyreon.  "Results from this first-in-human trial provide preliminary evidence of activity against HER2+ breast cancer with a low incidence of EGFR-related side effects.  We are looking forward to the initiation of Oncothyreon's planned Phase 1b trials of ONT-380, which we currently expect to begin before year end."

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® (trastuzumab) and Tykerb® (lapatinib). 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). ONT-380 has also demonstrated superior activity, based on overall survival, compared to lapatinib and to the investigational drug, neratinib, in an intracranial HER2+ breast cancer xenograft model.

Under the collaboration agreement with Array, Oncothyreon will conduct the clinical development of ONT-380 through a defined set of combination proof-of-concept trials in patients with metastatic breast cancer, including patients with brain metastases.  Oncothyreon currently expects to initiate its clinical development of ONT-380 in the fourth quarter of 2013.  In addition, an investigator-sponsored trial of ONT-380 in combination with trastuzumab in patients with brain metastases from HER2+ breast cancer is underway.  The trial is being conducted under the sponsorship of the Dana-Farber Cancer Institute, Boston, Massachusetts. 

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 results and future prospects, this release contains statements that are forward-looking. Any statements contained in this press release that are not statements of historical fact may be deemed to be forward-looking statements. Words such as "believes," "anticipates," "plans," "expects," "will," "intends," "potential," "possible" and similar expressions are intended to identify forward-looking statements. These forward-looking statements include Oncothyreon's expectations regarding clinical development activities.

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

Additional information relating to Oncothyreon can be found on EDGAR at www.sec.gov and on SEDAR at www.sedar.com.

SOURCE Oncothyreon Inc.