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The U.S. Food and Drug Administration has granted Breakthrough Therapy designation for PD 0332991, which now has the generic name palbociclib, for the treatment of patients with advanced breast cancer. Patients with advanced, estrogen-receptor positive, HER2-negative disease treated with letrozole (the standard anti-estrogen treatment) plus palbociclib had significant increases in progression-free survival compared with patients treated with letrozole alone.


"These results are as exciting as the initial results we saw for trastuzumab in HER2+ breast cancers, but represent a new approach for a different and larger subset of breast cancers-i.e., those who are ER positive," Dennis Slamon, MD, PhD, Director of the Revlon/UCLA Women's Cancer Research Program and Professor of Medicine, both at UCLA's Jonsson Comprehensive Cancer Center (who directed the drug's clinical trials there), said in a news release.


"We are working diligently to enroll the Phase III validation study as quickly and safely as possible."


The relatively new Breakthrough Therapy designation, enacted as part of the FDA's 2012 Safety and Innovation Act, was created to expedite the development and review time of a potential new drug for serious or life-threatening disease where early clinical evidence suggests the drug may demonstrate substantial improvement compared with existing therapies.

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The designation for palbociclib, made by Pfizer, Inc., was based on data from clinical and pre-clinical studies to determine the doses and initial safety results of the letrozole-palbociclib combo.


Phase II data reported at the CTRC-AACR San Antonio Breast Cancer Symposium (OT, 2/10/13issue) showed that in 165 breast cancer patients with ER+ disease, the median progression-free survival for those given the palbociclib-letrozole combination was 26.1 months compared with 7.5 months for those given letrozole alone.


A randomized, multicenter, double-blind Phase III study is now comparing the use of palbociclib combined with letrozole with letrozole alone as a first-line treatment for postmenopausal patients with ER+, HER2-, locally advanced, or metastatic breast cancer.