The FDA has granted a Breakthrough Therapy designation for the investigational drug palbociclib (PD-0332991; Pfizer)—an oral, selective inhibitor of cyclin-dependent kinases (CDKs) 4 and 6—for the potential treatment of patients with breast cancer. CDKs 4 and 6 are related kinases that enable tumor-cell progression, which enhances cell division and DNA replication. Inhibition of CDKs 4 and 6 with palbociclib has been shown to inhibit tumor-cell growth and DNA replication.
The designation of a Breakthrough Therapy is intended to expedite the FDA review of new medications for life-threatening conditions when preliminary evidence suggests significant improvement with a specific medication compared with currently available therapies.
The Breakthrough Therapy designation was based on data from several phase 2 clinical trials of patients with breast cancer.
Interim results were presented at the 2012 San Antonio Breast Cancer Symposium, showing that women with breast cancer who received palbociclib plus letrozole demonstrated a significant improvement in progression-free survival compared with women who received letrozole alone—26.1 months versus 7.5 months, respectively. (April 10, 2013)
