Learn About the Latest Therapeutic Advance for Breast Cancer

Trial data first presented at the AACR Annual Meeting 2014, showed new drug doubled progression-free survival for a certain type of metastatic breast cancer.

Richard S. Finn, MD, Unversity of California, Los Angeles
Richard S. Finn, MD, Unversity of California, Los Angeles

On Feb. 3, 2015, the U.S. Food and Drug Administration (FDA) approved palbociclib (Ibrance) for use in combination with the antihormone therapeutic letrozole for treating postmenopausal women with estrogen receptor-positive, HER2-negative, metastatic breast cancer.

Palbociclib was the sixth of eight anti-cancer treatments to receive an FDA approval in a three month period starting Dec. 1, 2014. With each approval covering a distinct type of cancer, it is clear that researchers are building broadly from our knowledge of the biology of cancer to identify and develop unique ways to target a range of cancers.

The FDA approval of palbociclib was based on the final analysis of progression-free survival of the randomized, phase II PALOMA-1 clinical trial. These data were first presented in the opening plenary session of the AACR Annual Meeting 2014, by Richard S. Finn, MD, an associate professor of medicine at the University of California, Los Angeles.

The data analysis showed that adding palbociclib to letrozole almost doubled the median time to disease progression. Progression-free survival for those patients who received the combination was 20.2 months compared with 10.2 months for those who received letrozole alone.

At the time the results were announced at the AACR Annual Meeting 2014, Finn explained:

The palbociclib and letrozole combination demonstrated a significantly improved clinical outcome for patients who had hormone receptor-positive, metastatic breast cancer in this phase II trial. Two prominent reasons for this success are: we identified a subpopulation of breast cancer patients-hormone receptor-positive, HER2-negative breast cancer patients, who are most likely to benefit, and we have a significantly improved second-generation CDK-4/6 inhibitor, which is very specific and efficient in its ability to block CDK-4/6, leading to less toxicity.

Cancer arises when the orderly processes that control the multiplication and life span of normal cells go awry. Palbociclib is a molecularly targeted therapeutic that blocks the function of two specific proteins that play a role in driving cell multiplication – cyclin-dependent kinase 4 (CDK4) and CDK6. It is the first CDK4/6 inhibitor to be approved by the FDA.

Importantly, because the FDA approval is based on progression-free survival data from a phase II study, palbociclib’s manufacturer, Pfizer, is required to conduct clinical trials to verify the clinical benefit of the therapeutic. A phase III clinical trial to do just that – PALOMA-2 – is already fully enrolled, with initial data expected before the end of the year.

Palbociclib is also being tested in a number of other breast cancer clinical trials and in clinical trials evaluating whether it might be an effective treatment for other types of cancer, including lung cancer, multiple myeloma, and gastrointestinal stromal tumors.