FDA Approves Palbociclib for Postmenopausal Women With Advanced Breast Cancer

Accelerated approval granted

On 3 February 2015, the US Food and Drug Administration (FDA) granted accelerated approval to palbociclib (Ibrance) to treat advanced (metastatic) breast cancer. Palbociclib works by inhibiting cyclin-dependent kinases (CDKs) 4 and 6, involved in promoting the growth of cancer cells. Palbociclib is intended for postmenopausal women with oestrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer who have not yet received an endocrine-based therapy. It is to be used in combination with letrozole, another FDA-approved product used to treat certain kinds of breast cancer in postmenopausal women.
The FDA granted palbociclib breakthrough therapy designation because the sponsor demonstrated through preliminary clinical evidence that the drug may offer a substantial improvement over available therapies. It also received a priority review, which provides for an expedited review of drugs intended to provide a significant improvement in safety or effectiveness in the treatment of a serious condition or meet an unmet medical need.
Palbociclib is being approved more than two months ahead of the prescription drug user fee goal date of 13 April, 2015, the date when the agency was scheduled to complete its review of the application.

Palbociclib is being approved under the FDA’s accelerated approval programme, 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 programme provides earlier patient access to promising new drugs while the company conducts confirmatory clinical trials.

The drug’s efficacy was demonstrated in 165 postmenopausal women with ER-positive, HER2-negative advanced breast cancer who had not received previous treatment for advanced disease. Clinical study participants were randomly assigned to receive palbociclib in combination with letrozole or letrozole alone. Participants treated with palbociclib plus letrozole achieved progression-free survival of 20.2 months, compared to about 10.2 months seen in participants receiving only letrozole. Information on overall survival is not available at this time.

The most common side effects of the drug were neutropaenia, leukopaenia, fatigue, anaemia, upper respiratory infection, nausea, stomatitis, alopecia, diarrhoea, thrombocytopaenia, decreased appetite, vomiting, asthenia, peripheral neuropathy and epistaxis. Healthcare professionals should inform patients of these risks.

It is recommended that treatment begin with a 125 milligram dose for 21 days, followed by seven days without treatment.

Healthcare 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.

Ibrance is marketed by New York City-based Pfizer, Inc.