The U.S. Food and Drug Administration today approved a potentially groundbreaking new drug to treat women with advanced breast cancer, signalling a new treatment strategy to arrest tumour growth and extend the time before the cancer worsens. The drug, IBRANCE (palbociclib) was studied in 165 post-menopausal breast cancer patients with advanced ER+, HER2- disease who had received no prior systemic therapy for their metastatic disease.

Early results from a clinical study led by UCLA researchers showed a dramatic improvement and the FDA granted the drug “breakthrough therapy” status in April 2013, allowing it to be fast-tracked to early approval.

The ER+/HER2- subgroup represents the largest proportion of breast cancer cases and is traditionally treated with therapies, like tamoxifen or letrozole, that target the hormone receptor pathway. “Palbociclib (IBRANCE) is the first drug in its class to be approved by the FDA,” said Dr. Richard Finn, the study’s principal investigator and a researcher at UCLA’s Jonsson Comprehensive Cancer Center. “All of us at UCLA are very proud of the important role we played in bringing this new agent to patients.”

Developed by Pfizer Inc., IBRANCE (palbociclib) targets a key family of proteins (CDK4/6) responsible for cell growth by preventing cells from dividing. Results of the multi-year phase 2 study showed a significant increase in progression-free survival (PFS) for patients with advanced breast cancer that was estrogen receptor positive (ER+), HER2-negative (HER2-), who were given a combination of a standard anti-estrogen treatment, letrozole, and palbociclib compared to letrozole alone.

“With the FDA approval, this study represents a potential practice-changing result,” said Dr. Dennis Slamon, director of the Revlon/UCLA Women’s Cancer Research Program and Clinical/Translational Research at the Jonsson Cancer Center. “I believe palbociclib will now become a standard treatment approach for postmenopausal women with ER+/HER2- metastatic breast cancer.”

The origin of the research began in 2007, when Finn and Slamon held a pivotal meeting with Pfizer to discuss palbociclib and other experimental drugs in its pipeline.

Preclinical work testing the drug in a panel of human breast cancer cells growing in culture dishes showed very encouraging activity, specifically against estrogen-receptor-positive (ER+) cancer cells. This led to a clinical study collaboration with Pfizer led by Finn and Slamon built on laboratory work directed at the Jonsson Cancer Center’s Translational Oncology Research Laboratory at UCLA.

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