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The Food and Drug Administration has granted accelerated approval to Ibrance (palbociclib) for the treatment of women with metastatic breast cancer. Ibrance, made by Pfizer, inhibits cyclin-dependent kinases (CKDs) 4 and 6, which are involved in promoting the growth of cancer cells.

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"The addition of palbociclib to letrozole provides a novel treatment option to women diagnosed with metastatic breast cancer," Richard Pazdur, MD, Director of the FDA's Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research, said in a news release.


Ibrance is the first drug in its class to be approved by the FDA, notes a new release from the University of California Los Angeles Jonsson Comprehensive Cancer Center, where the drug's clinical trial were led.


The drug is intended for postmenopausal women with estrogen receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer who have not yet received an endocrine-based therapy. It is intended for use in combination with letrozole.


Ibrance was approved under the FDA's accelerated approval program, which allows approval of a drug to treat a serious or life-threatening disease based on clinical data showing the drug has an effect on a surrogate endpoint reasonably likely to predict clinical benefit to patients. This program provides earlier patient access to promising new drugs while the company conducts confirmatory clinical trials.


The drug had also previously received Breakthrough Therapy designation (OT 5/10/13 issue); and was approved more than two months ahead of the prescription drug user fee goal date.


Ibrance was evaluated in a Phase II clinical trial of 165 postmenopausal women with ER-positive, HER2-negative metastatic breast cancer who had not received previous treatment for advanced disease. Patients received Ibrance in combination with letrozole or letrozole alone. Those receiving the Ibrance combination lived 20.2 months without disease progression, while patients receiving letrozole alone lived 10.2 months without disease progressing. Overall survival data from the trial is not yet available.


"What is really remarkable is that we doubled the median progression-free survival," the trial's principal investigator, Richard Finn, MD, Assistant Professor of Medicine at the Geffen School of Medicine at UCLA in the Department of Medicine, Division of Hematology/Oncology, said in a news release. "That type of result is not often seen in cancer medicine."


The most common side effects for Ibrance are neutropenia, leukopenia, anemia, upper respiratory infection, nausea, stomatitis, alopecia, diarrhea, thrombocytopenia, decreased appetite, vomiting, asthenia, peripheral neuropathy, and epistaxis.


It is recommended that treatment begin with a 125 milligram dose for 21 days, followed by seven days without treatment. Health care professionals are advised to monitor complete blood count prior to start of therapy and at the beginning of each cycle, as well as on Day 14 of the first two cycles, and as clinically indicated.


Additionally, a Phase III international clinical trial is being conducted and has completed enrollment.