Oncothyreon Announces Presentation of ONT-10 Data at ASCO Annual Meeting

June 2, 2014

SEATTLE, June 2, 2014 /PRNewswire/ – Oncothyreon Inc. (NASDAQ: ONTY) today
announced the presentation of data from a Phase 1 trial of ONT-10, an
antigen-specific immunotherapy targeting MUC1, at the American
Association of Clinical Oncology (ASCO) 2014 Annual Meeting in
Chicago. The data demonstrated that ONT-10 was well tolerated in this
trial, resulted in a humoral immune response in the majority of
patients and led to encouraging disease control in advanced stage
patients with a variety of cancer types.

The Phase 1 trial was a first-in-man dose escalation trial which
enrolled 49 patients with malignancies of types associated with the
expression of the tumor-associated antigen MUC1, including ovarian
cancer (14), breast cancer (10), colorectal cancer (7), pancreatic
cancer (5), endometrial cancer (4), and lung cancer (4). The patients
were extensively pretreated, having received multiple lines of prior
therapy (median 3, range 1-11). ONT-10 was administered at doses from
250 µg up to 2000 µg weekly, and from 250 µg up to 2000 µg every other

ONT-10 was well-tolerated in this trial, with no treatment-related
serious adverse events identified. The most common treatment-related
adverse events have been fatigue and injection site reactions, all of
which have been mild to moderate in severity. A dose-limiting toxicity
was not identified, and 2000 µg weekly has been selected as the dose
for future studies.

Patients without disease progression by Immune-Related Response Criteria
(irRC) for at least twelve weeks after starting treatment with ONT-10
were eligible for a separate maintenance protocol in which the same
dose of the immunotherapy was administered every six weeks until tumor
progression. To date, 31 of 43 patients (72%) currently evaluable for
response have entered the maintenance protocol. Eleven patients were
without disease progression for at least 6 months (range, 6.4-26
months), of which six remain on study. A decrease in the size of nodal
disease was seen in two patients with ovarian cancer.

A significant endpoint of the trial was to determine if ONT-10
stimulates the production of MUC1-specific antibodies as seen in
preclinical animal models. IgM and IgG anti-MUC1 antibodies were
observed in the majority of patients with many titers exceeding
1:50,000. The data support a dose and schedule response, with the
greatest IgG response occurring at 1000-2000 µg weekly.

“We are encouraged by the high percentage of patients who were able to
enter the maintenance protocol and the lack of disease progression for
at least 6 months seen in advanced stage patients,” said Diana Hausman,
M.D., Chief Medical Officer at Oncothyreon. “We believe these results
support further development of ONT-10, and we are currently enrolling
patients with advanced breast and ovarian cancer in two
disease-specific expansion cohorts of this trial. We expect these
patients to provide comparative data for the recently announced planned
combination trial of ONT-10 with varlilumab, the fully human monoclonal
antibody targeting CD27 from Celldex Therapeutics, Inc.”

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 glycosylated antigen designed to mimic the hypoglycosylated state of
tumor-associated MUC1 and intended to stimulate both the humoral and
cellular arms of the immune response. Additionally, ONT-10 contains the
adjuvant PET-Lipid A, a fully synthetic toll like receptor 4 (TLR4)
agonist proprietary to Oncothyreon.

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.

Source: PR Newswire

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