Puma Biotechnology Announces European Medicines Agency Validation of Marketing Authorization Application for PB272 (Neratinib) as Extended Adjuvant Treatment of HER2-Positive Early Stage Breast Cancer in Europe

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LOS ANGELES–(BUSINESS WIRE)–Puma Biotechnology, Inc. (NYSE: PBYI), a biopharmaceutical company,
announced that the Marketing Authorization Application (MAA) for
neratinib has been validated by the European Medicines Agency (EMA).
Validation of the MAA confirms that the submission is complete and
starts the EMA’s formal review process. The potential indication for
neratinib is for the extended adjuvant treatment of HER2-positive early
stage breast cancer that has previously been treated with trastuzumab
(Herceptin®)-based adjuvant therapy. The MAA submission is based upon
the ExteNET Phase III study, which reached its primary endpoint whereby
neratinib demonstrated a statistically significant reduction of risk of
invasive disease recurrence or death versus placebo.

“Although the use of trastuzumab in the adjuvant setting has led to a
reduction in disease recurrence in patients with early stage
HER2-positive breast cancer, there remains an unmet clinical need for
further improvement in outcome in order to attempt to further reduce
this risk of recurrence following trastuzumab therapy,” said Alan H.
Auerbach, Chief Executive Officer and President of Puma. “Neratinib may
be able to provide this type of improvement to further help the patients
with this disease. We look forward to working with the CHMP/EMA during
their review of this submission.”

In the ExteNET study, treatment with neratinib resulted in a 33%
reduction of risk of invasive disease recurrence or death versus placebo
(hazard ratio = 0.67, p = 0.009). The 2-year invasive disease free
survival (DFS) rate for the neratinib arm was 93.9% and the 2-year DFS
rate for the placebo arm was 91.6%. For the pre-defined subgroup of
patients with hormone receptor positive disease, the results of the
trial demonstrated that treatment with neratinib resulted in a 49%
reduction of risk of invasive disease recurrence or death versus placebo
(hazard ratio = 0.51, p = 0.001). For the patients with hormone receptor
positive disease, the 2-year DFS rate for the neratinib arm was 95.4%
and the 2-year DFS rate for the placebo arm was 91.2%. Results of the
study were published online in The Lancet Oncology on February
10, 2016.

The most frequently observed adverse event for the neratinib-treated
patients was diarrhea, with approximately 39.9% of the neratinib-treated
patients experiencing grade 3 or higher diarrhea (1 patient (0.1%) had
grade 4 diarrhea). Patients who received neratinib in the ExteNET trial
did not receive any prophylaxis with antidiarrheal agents to prevent the
neratinib-related diarrhea. Interim results of a Phase II study of
neratinib monotherapy in patients with HER2-positive early stage breast
cancer who have previously been treated with adjuvant trastuzumab, where
patients received anti-diarrheal prophylaxis with loperamide,
demonstrated that treatment with prophylactic loperamide reduced the
rate of grade 3 or higher diarrhea to between 13.0% and 18.5%.

About ExteNET

The ExteNET trial is a double-blind, placebo-controlled, Phase III trial
of neratinib versus placebo after adjuvant treatment with trastuzumab
(Herceptin) in women with early stage HER2-positive breast cancer. The
trial randomized 2,840 patients in 41 countries with early stage
HER2-positive breast cancer who had undergone surgery and adjuvant
treatment with trastuzumab. After completion of adjuvant treatment with
trastuzumab, patients were randomized to receive extended adjuvant
treatment with either neratinib or placebo for a period of one year.
Patients were then followed for recurrent disease, ductal carcinoma in
situ (DCIS), or death for a period of two years after randomization in
the trial. The primary endpoint of the trial was DFS.

About Puma Biotechnology

Puma Biotechnology, Inc. is a biopharmaceutical company with a focus on
the development and commercialization of innovative products to enhance
cancer care. The Company in-licenses the global development and
commercialization rights to three drug candidates—PB272 (neratinib
(oral)), PB272 (neratinib (intravenous)) and PB357. Neratinib is a
potent irreversible tyrosine kinase inhibitor that blocks signal
transduction through the epidermal growth factor receptors, HER1, HER2
and HER4. Currently, the Company is primarily focused on the development
of the oral version of neratinib, and its most advanced drug candidates
are directed at the treatment of HER2-positive breast cancer. The
Company believes that neratinib has clinical application in the
treatment of several other cancers as well, including non-small cell
lung cancer and other tumor types that over-express or have a mutation
in HER2.

Further information about Puma Biotechnology can be found at www.pumabiotechnology.com.

Forward-Looking Statements:

This press release contains forward-looking statements, including
statements regarding the potential benefits of neratinib and the MAA for
neratinib in Europe for the potential indication for the extended
adjuvant treatment of HER2-positive early stage breast cancer that has
previously been treated with trastuzumab (Herceptin®)-based adjuvant
therapy. All forward-looking statements included in this press release
involve risks and uncertainties that could cause the Company’s actual
results to differ materially from the anticipated results and
expectations expressed in these forward-looking statements. These
statements are based on current expectations, forecasts and assumptions,
and actual outcomes and results could differ materially from these
statements due to a number of factors, which include, but are not
limited to, the fact that the Company has no product revenue and no
products approved for marketing, the Company’s dependence on PB272,
which is still under development and may never receive regulatory
approval, the challenges associated with conducting and enrolling
clinical trials, the risk that the results of clinical trials may not
support the Company’s drug candidate claims, even if approved, the risk
that physicians and patients may not accept or use the Company’s
products, the Company’s reliance on third parties to conduct its
clinical trials and to formulate and manufacture its drug candidates,
the Company’s dependence on licensed intellectual property, and the
other risk factors disclosed in the periodic and current reports filed
by the Company with the Securities and Exchange Commission from time to
time, including the Company’s Annual Report on Form 10-K for the year
ended December 31, 2015. Readers are cautioned not to place undue
reliance on these forward-looking statements, which speak only as of the
date hereof. The Company assumes no obligation to update these
forward-looking statements, except as required by law.

Contacts

Puma Biotechnology, Inc.
Alan H. Auerbach or Mariann Ohanesian,
+1-424-248-6500
info@pumabiotechnology.com
ir@pumabiotechnology.com
or
Russo
Partners
David Schull, +1-212-845-4271
david.schull@russopartnersllc.com