Pfizer's Palbociclib (PD-0332991) Earns FDA Breakthrough Therapy Designation for Potential Treatment of Patients With Breast Cancer
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Pfizer Inc. announced its investigational compound palbociclib (PD-0332991), an oral and selective inhibitor of cyclin dependent kinases (CDK) 4 and 6, has received Breakthrough Therapy designation by the United States Food and Drug Administration (FDA) for the potential treatment of patients with breast cancer.
In a release, the Company noted:
Enacted as part of the 2012 FDA Safety and Innovation Act (FDASIA), Breakthrough Therapy designation is intended to expedite the development and review of a potential new medicine if it is "intended, alone or in combination with one or more other drugs, to treat a serious or life-threatening disease or condition and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints." The Breakthrough Therapy designation is distinct from the FDA's other mechanisms to expedite drug development and review.
"We appreciate the opportunity that Breakthrough Therapy designation provides to work closely with the FDA on the development of palbociclib," said Dr. Mace Rothenberg, senior vice president of clinical development and medical affairs for Pfizer's Oncology business unit. "Palbociclib is one example of Pfizer's commitment to identifying and translating innovative science into meaningful new treatment options for cancer patients."
Pfizer will continue to work with the FDA to better understand the implications of Breakthrough Therapy designation on the palbociclib development program and to generate evidence needed to support a potential regulatory submission. The FDA's requirements for a potential submission have not yet been defined.
Pfizer has initiated a randomized, multi-center, double-blind Phase 3 study (known as Study 1008) evaluating palbociclib in combination with letrozole versus letrozole alone as a first-line treatment for post-menopausal patients with ER+, HER2- locally advanced or metastatic breast cancer. Study 1008 is currently open and enrolling.
The Breakthrough Therapy designation was based on preliminary Phase 2 data in this patient population. Interim data presented at the 2012 CTRC-AACR San Antonio Breast Cancer Symposium showed that women treated with the combination of palbociclib plus letrozole achieved a statistically significant improvement in median progression free survival (PFS) compared to women who received letrozole alone (26.1 months and 7.5 months, respectively).
Breast cancer is the most commonly diagnosed cancer in women and the leading cause of cancer death among women worldwide. Among post- menopausal patients with advanced or metastatic breast cancer, ER+, HER2- is the largest molecular subgroup, representing approximately 60 percent of cases. Despite currently available treatments, survival rates for advanced or metastatic breast cancer remain low.
Palbociclib is an investigational, oral and selective inhibitor of cyclin dependent kinases (CDK) 4 and 6. 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 susceptibility gene protein, a tumor suppressor protein, and interfere with tumor cell progression. In pre-clinical studies, palbociclib 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, palbociclib is currently being evaluated through Pfizer-sponsored and investigator-initiated research in other cancers. More Information on Palbociclib: www.clinicaltrials.gov.