The U.S. Food and Drug Administration (FDA) today approved a new drug to treat patients with advanced breast cancer, signaling a new strategy for arresting tumor growth and extending the time before cancer worsens in women with metastatic disease. The drug, Ibrance (palbociclib), was studied in 165 post-menopausal women with advanced estrogen–receptor positive (ER+) and HER2–negative (HER2-) breast cancer who had received no prior systemic therapy for their metastatic disease. In 2013, after patients in a clinical study led by UCLA researchers showed a dramatic improvement, the FDA granted the drug “breakthrough therapy” status, allowing it to be fast-tracked for approval. ER+/HER2- is the most common type of breast cancer; it is traditionally treated with therapies like tamoxifen or letrozole that target the hormone receptor pathway. “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, Ibrance targets proteins in cancer cells — cyclin D kinase 4 (CDK 4) and cyclin D kinase 6 (CDK 6) — preventing the cells from dividing. A multiyear phase 2 study found a significantly higher progression-free survival rate for patients with advanced ER+/HER2- breast cancer who were given palbociclib in addition to letrozole, a standard anti-estrogen treatment, compared with women who received letrozole alone.
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