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Pfizer Presents Phase 2 Data Showing Investigational Therapy PD-0332991 Plus Letrozole Significantly Improved Progression Free Survival Compared With Letrozole Alone In Patients With ER Positive, HER2 Negative Advanced Breast Cancer
NEW YORK --(Business Wire)--
Pfizer Inc. today announced randomized Phase 2 data that showed
PD-0332991 (PD-991) in combination with letrozole significantly extended
progression free survival (PFS) compared with letrozole alone in
post-menopausal patients with estrogen receptor positive (ER+), human
epidermal growth factor receptor 2 negative (HER2-) locally advanced or
metastatic breast cancer. For patients treated with the combination of
PD-991 plus letrozole, median PFS was 26.1 months, a statistically
significant improvement compared to the median PFS in women who received
letrozole alone, which was 7.5 months (HR=0.37 [95% CI: 0.21, 0.63]; P
<0.001). These data were presented today and featured in a press
conference at the 35th Annual San Antonio Breast Cancer
Symposium (Abstract #S1-6).
"These results are especially important because of the magnitude of
clinical effect observed and the fact that PD-991 represents a potential
first-in-class compound. Based on these positive Phase 2 data, Pfizer is
planning to open a randomized Phase 3 study of PD-991 in this patient
population in 2013," said Dr. Mace Rothenberg, senior vice president of
clinical development and medical affairs for Pfizer's Oncology Business
Unit. "We are working with regulatory authorities to advance the
development of this promising compound in the most expeditious and
responsible way."
Breast cancer is the most commonly diagnosed cancer1 and the
leading cause of cancer death among women worldwide.2
Estrogen receptor positive, HER2- breast cancer represents approximately
60 percent of all cases of breast cancer.3 Despite currently
available treatments, survival rates for advanced or metastatic breast
cancer remain low.4
About the Phase 2 Program
The focus of Phase 2 evaluation of PD-991 was to measure the clinical
activity of PD-991 in combination with letrozole versus letrozole alone
in post-menopausal women with ER+, HER2- locally advanced or metastatic
breast cancer. In Part 1, 66 patients were enrolled. Preliminary results
were presented in May 2012 at the IMPAKT Breast Cancer Conference in
Brussels, Belgium, and showed statistically significant improvement in
median PFS in the PD-991 plus letrozole arm versus the letrozole arm.
Part 2 enrolled 99 additional patients whose tumors were selected for
presence of biomarkers: cyclin D1 amplification and/or p16 loss. The
results presented here at SABCS reflect the combined interim data
analysis of parts 1 and 2 of the Phase 2 evaluation.
In patients with measurable disease, the objective response rate was 45
percent for those women who received PD-991 plus letrozole versus 31
percent for those who received letrozole alone. The clinical benefit
rate (defined as complete response plus partial response plus stable
disease for =24 weeks) was 70 percent versus 44 percent, respectively.
The differences observed in te objective response rate and clinical
benefit rate were statistically significant. The most frequently
reported treatment-related Grade 3/4 adverse events (AEs) in patients
who received the combination therapy were neutropenia, leucopenia,
anemia and fatigue.
Both Part 1 and Part 2 of this Phase 2 evaluation are ongoing but no
longer enrolling new patients. Final efficacy and safety data are
expected to be presented at a future medical congress.
"In demonstrating very strong efficacy and a manageable tolerability
profile, these new data represent a potential major advancement in
breast cancer clinical research and our continued efforts to identify
new medicines that target patients most likely to have an optimal
response," said Dr. Richard S. Finn, Associate Professor of Medicine,
Revlon/UCLA Women's Cancer Research Program at Jonsson Comprehensive
Cancer Center, UCLA, and lead investigator of the Phase 2 trial. "The
oncology community is looking forward to the further evaluation of
PD-991 in the planned Phase 3 trial and very interested in the potential
for this novel CDK 4 and 6 inhibitor to improve the treatment landscape
for patients with advanced breast cancer."
About PD-991
PD-991 is an investigational, oral and selective inhibitor of the CDK 4
and 6 kinases. CDK 4 and 6 are two closely related kinases that enable
tumor cell progression during phase G1 to phase S in the cell cycle.
This progression is necessary for DNA replication and cell division.
Inhibition of CDK 4 and 6 has been shown to prevent the deactivation of
retinoblastoma, a tumor suppressor protein, and interfere with tumor
cell progression. In pre-clinical studies, PD-991 was shown to be an
inhibitor of cell growth and a suppressor of DNA replication by
preventing cells from entering S phase.
In addition to breast cancer, PD-991 is currently being evaluated
through Pfizer-sponsored and investigator-initiated research in other
cancers, including liposarcoma, non-small cell lung cancer, liver
cancer, ovarian cancer, glioblastoma, refractory solid tumors, multiple
myeloma, and mantle cell lymphoma.
About Pfizer Oncology
Pfizer Oncology is committed to the discovery, investigation and
development of innovative treatment options to improve the outlook for
cancer patients worldwide. Our strong pipeline of biologics and small
molecules, one of the most robust in the industry, is studied with
precise focus on identifying and translating the best scientific
breakthroughs into clinical application for patients across a wide range
of cancers. By working collaboratively with academic institutions,
individual researchers, cooperative research groups, governments, and
licensing partners, Pfizer Oncology strives to cure or control cancer
with breakthrough medicines, to deliver the right drug for each patient
at the right time. For more information, please visit www.Pfizer.com.
DISCLOSURE NOTICE: The information contained in this release is as of
December 5, 2012. Pfizer assumes no obligation to update forward-looking
statements contained in this release as the result of new information or
future events or developments.
This release contains forward-looking information that involves
substantial risks and uncertainties about PD-991, an investigational
therapy, including a potential indication for advanced breast cancer and
various other potential indications and the anticipated commencement of
a Phase 3 study in advanced breast cancer in 2013. Such risks and
uncertainties include, among other things, the uncertainties inherent in
research and development, including the ability to meet anticipated
clinical trial commencement and completion dates, regulatory submission
and approval dates, and launch dates; decisions by regulatory
authorities regarding whether and when to approve any drug applications
that may be filed for any such potential indications as
well as their decisions regarding labeling and other
matters that could affect the availability or commercial
potential of such potential indications; and competitive developments.
A further description of risks and uncertainties can be found in
Pfizer's Annual Report on Form 10-K for the fiscal year ended December
31, 2011 and in its reports on Form 10-Q and Form 8-K.
1 World Health Organization. Breast Cancer Burden. Available
at: http://www.who.int/cancer/detection/breastcancer/en/index1.html.
Accessed November 15, 2012.
2 World Health Organization. Cancer. Available at: http://www.who.int/mediacentre/factsheets/fs297/en/.
Accessed November 15, 2012.
3 Decision Resources. Event Driven Pharmacor Report. 2012.
4 Miles, David. When HER2 is not the target: advances in the
treatment of HER2-negative metastatic breast cancer. Breast Cancer
Research 2009 August; 11(4).
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