When it comes to treating cancer, early detection is critical to bolstering survival rates. However, not everyone is diagnosed in this crucial early stage, and some are not treated until the disease has become metastatic. The Federal Drug Administration (FDA) has just approved a new drug called Ibrance (palbociclib), which will treat a common form of advanced breast cancer in post-menopausal women. The drug was developed by Pfizer, and clinical trials were conducted at UCLA’s Jonsson Cancer Center’s Translational Oncology Research Laboratory. The drug was classified as a “breakthrough therapy” in 2013, allowing approval to be expedited.
"Palbociclib (IBRANCE) is the first drug in its class to be approved by the FDA," principal investigator Richard Finn said in a press release. "All of us at UCLA are very proud of the important role we played in bringing this new agent to patients.”
Development for the drug began in 2007. The drug targets cyclin-dependent kinases 4 and 6 (CDK4/6), which then inhibits cell division. No safety issues were discovered during Phase 1 testing, and so the drug moved forward.
Phase 2 testing began in 2010, and the study utilized 165 women whose cancer is estrogen receptor positive (ER+) and human epidermal growth factor receptor 2 (HER2-). The participants were divided into two groups: one group only used the post-surgical, estrogen-targeting treatment letrozole, while the other group used a combination of letrozole and IBRANCE. The results were fairly astounding. Those who took letrozole alone were progression-free for an average of 10.2 months. However, those that used a combination of the drugs were able to hold back the progression of the disease for an average of 20.2 months; an unprecedented length of time.
"What is really remarkable is that we doubled the median progression-free survival," Finn continued. "That type of result is not often seen in cancer medicine.”
Phase 3 trials used more than 660 women. Around 80% of the women who took IBRANCE in conjunction with letrozole did see some benefits. There were a few negative side effects, as the drug did result in lower white blood cell count, but this effect wasn’t as strong as is seen in usual chemotherapy treatments.
“With the FDA approval, this study represents a potential practice-changing result,” added Dennis Slamon, who serves as the director of the Revlon/UCLA Women’s Cancer Research Program. “I believe palbociclib will now become a standard treatment approach for postmenopausal women with ER+/HER2- metastatic breast cancer.”
Breast cancer affects roughly 1 in 8 women at some point during their lives, and roughly 60% of them will have the ER+/HER2-, which is part of what makes this approval and the successful results so phenomenal.
“[T]he magnitude of the observed benefit was very gratifying and reminiscent of results we saw when we conducted the initial studies on Herceptin in HER2+ breast cancers two decades ago,” Slamon concluded.
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