Puma Biotechnology Announces Interim 5-Year Disease Free Survival Data from Phase III Trial of PB272 (Neratinib) in Extended Adjuvant HER2-Positive Early Stage Breast Cancer (ExteNET Trial)

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LOS ANGELES–(BUSINESS WIRE)–Puma Biotechnology, Inc. (NYSE: PBYI), a biopharmaceutical company,
announced updated results from the Phase III clinical trial of Puma’s
investigational drug PB272 (neratinib) for the extended adjuvant
treatment of HER2-positive early stage breast cancer (ExteNET trial).
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 ExteNET 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, or death for a period of two years after
randomization in the trial. The primary endpoint of the trial was
invasive disease free survival (DFS). The results of the trial
demonstrated that 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 DFS rate for the neratinib
arm was 93.9% and the 2-year invasive DFS rate for the placebo arm was
91.6%. These results were previously reported at the 2015 American
Society of Clinical Oncology meeting and updated results, including
interim 3-year invasive DFS data, were presented at the 2015 CTRC-AACR
San Antonio Breast Cancer Symposium (SABCS).

As part of the data analysis for the New Drug Application (NDA) filing
in the United States and the Marketing Authorisation Application (MAA)
submission in Europe, an updated analysis that included an interim
5-year invasive DFS analysis was performed. This data analysis was
performed in order to examine the durability of treatment effect beyond
the 2-year data included in the primary analysis. This interim analysis
was not a pre-planned analysis in the statistical analysis plan for the
trial. For the primary endpoint of the trial, invasive DFS, the 5-year
interim results of the trial demonstrated that treatment with neratinib
resulted in a 26% reduction of risk of invasive disease recurrence or
death versus placebo (hazard ratio = 0.74, p = 0.017). The 5-year
interim invasive DFS rate for the neratinib arm was 90.4% and the 5-year
interim invasive DFS rate for the placebo arm was 87.9%. Additional
updated results for the 3-year invasive DFS rate and 4-year invasive DFS
rate are shown in the table below:

 
DFS for Intent to Treat (ITT) Population
        3-Year DFS       4-Year DFS       5-Year Interim DFS
Neratinib       92.5%       91.4%       90.4%
Placebo       90.3%       89.2%       87.9%
Absolute invasive DFS                  
Difference       2.2%       2.2%       2.5%
 

As an inclusion criteria for the ExteNET trial, patients needed to have
tumors that were HER2 positive using local assessment. In addition, as a
pre-defined subgroup in the trial, patients had centralized HER2 testing
performed on their tumor as well. To date, centralized HER2 testing has
been performed on 2,140 (75%) of the patients in the ExteNET trial, and
further central testing on available samples is currently ongoing. For
the 1,777 patients whose tumors were HER2 positive by central
confirmation, the interim results of the trial demonstrated that
treatment with neratinib resulted in a 30% reduction of risk of invasive
disease recurrence or death versus placebo (hazard ratio = 0.70, p =
0.026). The 5-year interim invasive DFS rate for the centrally confirmed
patients in the neratinib arm was 90.8% and the 5-year interim invasive
DFS rate for the centrally confirmed patients in the placebo arm was
88.1%.

For the pre-defined subgroup of 1,631 patients with hormone receptor
positive disease, the interim results of the trial demonstrated that
treatment with neratinib resulted in a 41% reduction of risk of invasive
disease recurrence or death versus placebo (hazard ratio = 0.59, p =
0.002). The 5-year interim invasive DFS rate for the neratinib arm was
91.7% and the 5-year interim invasive DFS rate for the placebo arm was
86.9%. Additional updated results for the 3-year invasive DFS rate and
4-year invasive DFS rate are shown in the table below:

 
DFS for Hormone Receptor Positive (HR-positive) Population
        3-Year DFS       4-Year DFS       5-Year Interim DFS
Neratinib       93.8%       92.9%       91.7%
Placebo       89.9%       88.6%       86.9%
Absolute invasive DFS                  
Difference       3.9%       4.3%       4.8%
 

“We are very pleased with the interim 5-year invasive DFS results from
the ExteNET trial with neratinib,” said Alan H. Auerbach, Chief
Executive Officer and President of Puma. “We believe these results
support the long term clinical benefit of neratinib in the extended
adjuvant treatment of patients with early stage HER2-positive breast
cancer who have completed prior trastuzumab-based adjuvant therapy. We
look forward to obtaining the full 5-year DFS data, which we anticipate
will be available in 2017.”

Conference Call and Webcast

The Company will host a conference call to discuss the updated ExteNET
trial data at 2:00 p.m. PDT (5:00 p.m. EDT) on July 21. The conference
call may be accessed by dialing 1-877-709-8150 for domestic callers and
1-201-689-8354 for international callers. Please specify to the operator
that you would like to join the “Puma Biotechnology Update Call.” The
conference call and presentation slides will be webcast live and
accessible through the Investor Relations section of Puma’s website at http://www.pumabiotechnology.com/ir_events.html
and will be archived there for 30 days following the call. Please visit
Puma’s website several minutes prior to the start of the broadcast to
ensure adequate time for any software download that may be necessary.

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 development of the Company’s drug candidates
and the announcement of data relative to the Company’s clinical trials.
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