Drug Combo for Breast Cancer Close to Getting Worldwide Approval

Building on earlier clinical trials, researchers at the University of Californina, Los Angeles have confirmed that the “breakthrough” drug palbociclib when used in combination with the traditional hormonal therapy letrozole delays progression of advanced breast cancer significantly and without the harsh side effects seen in some women prescribed letrozole alone.

A release from the university notes that the study, published in November 2016 in the New England Journal of Medicine, is the phase 3 study following phase 1 and phase 2 clinical trials that led to U.S. Food and Drug Administration approval of palbociclib in early 2015. Palbociclib was also approved in Europe for the first time earlier in November based on these results. In 2013, after women in a clinical study led by UCLA researchers showed a dramatic improvement, the FDA granted palbociclib “breakthrough therapy” status, allowing it to be fast-tracked for approval.

The drug combination is the first and only treatment for women with estrogen-receptor–positive breast cancer to show such significant results in a randomized phase 3 trial. Dr. Richard Finn and Dr. Dennis Slamon of the UCLA Jonsson Comprehensive Cancer Center led the laboratory studies and previous trials and are co-authors of the study.

The release quotes Finn, who is also an associate professor of medicine in the David Geffen School of Medicine at UCLA, as saying, “These results are a truly meaningful advancement for women in this patient population. The results of the phase 3 study will support the full approval of palbociclib in the United States and around the world.”

Palbociclib (marketed as Ibrance by Pfizer) is known as the first new drug that in combination with hormonal therapy has proven to be very effective in post-menopausal women with estrogen receptor-positive breast cancer. Estrogen-receptor–positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) breast cancer 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, which was developed by Pfizer, prevents cells from dividing by targeting a key family of proteins (CDK4/6) responsible for cell growth.

Led by Finn and Slamon, an international team of investigators from 17 countries analyzed 666 women with advanced ER+/HER2- breast cancer. The people were treated with a combination of palbociclib and letrozole, and had not received prior systemic therapy for their cancer. The results of the new study confirmed the previous findings of the multi-year phase 1 and phase 2 trials, which showed a significant increase in progression-free survival, meaning without the cancer worsening, compared to letrozole alone.