Oncothyreon and Array BioPharma Announce Initiation of Phase 1b Trial of ONT-380 in Combination with Capecitabine and/or Trastuzumab in Patients with Metastatic HER2+ Breast Cancer

February 3, 2014

SEATTLE AND BOULDER, CO, Feb. 3, 2014 /PRNewswire/ – Oncothyreon Inc. (NASDAQ:
ONTY) and Array BioPharma Inc. (NASDAQ: ARRY) today announced the
initiation of a Phase 1b trial of ONT-380 (ARRY-380) in combination
with Xeloda® (capecitabine) and/or Herceptin® (trastuzumab) in patients
with metastatic HER2+ breast cancer. ONT-380 is an orally active,
reversible and selective small-molecule HER2 inhibitor invented by
Array and being developed by Oncothyreon in collaboration with Array.

The trial (ClinicalTrials.gov Identifier NCT02025192) is a
dose-escalation study in patients who have been previously treated with
Herceptin® (trastuzumab) and Kadcyla® (ado-trastuzumab emtansine or
TDM-1) for metastatic breast cancer. The primary objective is to
determine the maximum-tolerated and/or recommended Phase 2 dose
(MTD/RP2D) of ONT-380 in combination with the approved dose of either
Xeloda or Herceptin or both. Secondary objectives include an
evaluation of the safety and preliminary anti-tumor activity of the
combinations. The study includes an expansion arm at the MTD/RP2D of
ONT-380 in combination with both Xeloda and Herceptin, with the option
to include expansion arms in combination with either agent alone.
Patients with treated stable central nervous system (CNS) metastases
are eligible for the dose escalation portions of the trial, while
patients with CNS metastases which are either asymptomatic and
untreated or progressive following local therapy may be included in the
expansion cohorts. The trial is expected to enroll approximately 50

“The treatment or prevention of CNS metastases is perhaps the greatest
unmet medical need for patients with HER2+ metastatic breast cancer,”
said Diana Hausman, M.D., Chief Medical Officer of Oncothyreon.
“ONT-380 has demonstrated preclinical activity in an animal model of
brain metastases from HER2+ breast cancer. This trial is intended to
identify clinically relevant combination therapy to advance the
evaluation of the activity of ONT-380 in patients with CNS metastases.”

“We are encouraged by the rapid progress the Oncothyreon team has made
since initiating our collaboration, now that important combination
studies are enrolling,” said Michael Needle, M.D., Chief Medical
Officer of Array. “We believe the unique pharmacologic properties of
ONT-380, as the only oral, selective HER2 inhibitor, position it
favorably as a potential new option for patients fighting breast

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® (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
Tykerb® and to the investigational drug, neratinib, in an intracranial
HER2+ breast cancer xenograft model.

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 Herceptin-containing regimen. In addition, over 80% had
been treated with Tykerb, 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 Tykerb – and Herceptin
-containing regimens.

In addition to the Phase 1b trial of ONT-380 in combination with Xeloda
and/or Herceptin described above, Oncothyreon expects to initiate a
Phase 1b trial of ONT-380 in combination with Kadcyla® (ado-trastuzumab
emtansine or TDM-1) in patients with metastatic HER2+ breast cancer.
The Dana-Farber Cancer Institute, Boston, Massachusetts, is also
currently conducting an investigator-sponsored trial of ONT-380 in
combination with Herceptin in patients with brain metastases from HER2+
breast cancer.

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.

About Array BioPharma

Array BioPharma Inc. is a biopharmaceutical company focused on the
discovery, development and commercialization of targeted small molecule
drugs to treat patients afflicted with cancer. Seven Phase 3 or
pivotal studies are already in progress, or are planned to begin,
within the next year. These programs include the wholly-owned
hematology drug, filanesib (ARRY-520), for multiple myeloma and two
partnered cancer drugs, selumetinib (AstraZeneca) and MEK162
(Novartis). For more information on Array, please go to www.arraybiopharma.com

Oncothyreon 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.

Array BioPharma Forward-Looking Statements

This press release contains forward-looking statements within the
meaning of the Private Securities Litigation Reform Act of 1995,
including statements about the potential for the results of ongoing
clinical trials to support further development, regulatory approval or
the marketing success of ONT-380 (ARRY-380), anticipated clinical and
other product development activities related to ONT-380 (ARRY-380) and
the costs and responsibilities of those activities, expected benefits
and market potential for ONT-380 (ARRY-380), and the success of
activities to obtain market approval and sales. These statements
involve significant risks and uncertainties, including those discussed
in the most recent annual report filed on Form 10-K, quarterly reports
filed on Form 10-Q, and other reports filed by Array with the
Securities and Exchange Commission. Because these statements reflect
current expectations concerning future events, actual results could
differ materially from those anticipated in these forward-looking
statements as a result of many factors. These factors include, but are
not limited to, the ability of Array and Oncothyreon to continue to
fund and successfully progress research and development efforts with
respect to ONT-380 (ARRY-380); risks associated with dependence on
collaborators for the clinical development and commercialization of
out-licensed drug candidates, including ONT-380 (ARRY-380); the ability
to effectively and timely conduct clinical trials in light of
increasing costs and difficulties in locating appropriate trial sites
and in enrolling patients who meet the criteria for certain clinical
trials; and risks associated with dependence on third-party service
providers to successfully conduct clinical trials within and outside
the United States. Array is providing this information as of February
3, 2014 and undertakes no duty to update any forward-looking statements
to reflect the occurrence of events or circumstances after the date of
such statements or of anticipated or unanticipated events that alter
any assumptions underlying such statements.

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.

Source: PR Newswire

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