This past week, the United States Food and Drug Administration (FDA) announced that it would expand the indication of Ibrance (palbociclib) to include men with specific types of advanced or metastatic breast cancer. More specifically, Ibrance will now be indicated for use by men with hormone receptor-positive (HR-positive), human epidermal growth factor receptor 2-negative (HER2-negative) advanced breast cancer. Ibrance will also be used in addition to other, specific hormone therapies for these types of cancer as well. Ibrance is a kinase inhibitor, that blocks CDKs 4 and 6 (cyclin-dependent kinases). These kinases are responsible for cellular growth and development, and when blocked, may stop cancer cells from continuing to replicate.
The request to expand the use of Ibrance was filed as a supplemental New Drug Application (sNDA) after the manufacturer of the medication, Pfizer, provided data from electronic health records that demonstrated the safety of Ibrance in males with ABC who were already taking the medication in the real world. When a medication is prescribed to a population that it wasn’t originally tested on or approved for, like males with ABC in this case, it is often referred to as off-label prescribing. However, the records provided by Pfizer indicated that males with HR-positive, HER2-negative ABC taking Ibrance, in addition to an aromatase inhibitor or fulvestrant, experienced a similar safety profile to women in the same situation. Aromatase inhibitors and fulvestrant both disrupt the synthesis of estrogen. In hormone-sensitive cancers, like HR-positive breast cancer, estrogen may help fuel cancer cells to grow, so blocking its formation may help slow down cancer growth.
Breast cancer in men
Breast cancer in males may make up less than 1% of all breast cancer cases, and most of these cases involve cancer that expresses hormone receptors. Since breast cancer in males is so rare, there are few clinical trials that exist that involve men, and therefore, there are fewer treatment options for this population. Using current, real-world data to show the safety and efficacy of medication is something that is allowed by a law passed in 2016 called the 21st Century Cures Act, which helps make promising treatment options available quicker to individuals who need them.
Ibrance’s indication has now been expanded for use by post-menopausal women or men with HR-positive, HER2-negative advanced or metastatic breast cancer. It is to be used in combination with an aromatase inhibitor if the individual taking the medication has had no previous exposure to hormone therapy. However, if the individual taking Ibrance has had prior exposure to hormone therapy and their cancer still progressed, the medication should be taken in combination with fulvestrant instead.
The most common adverse effects experienced by individuals taking Ibrance include, but are not limited to, fatigue, nausea, low white blood cell counts (leukopenia), low red blood cell counts (anemia), low platelet counts (thrombocytopenia), inflammation of the mouth and lips, diarrhea, hair loss, decreased appetite, fever, and rash. Individuals taking Ibrance should have their blood cell counts monitored regularly. Ibrance can cause harm to a developing fetus, and therefore, men taking Ibrance who have female partners with reproductive potential should use birth control methods during and for three months after taking Ibrance.
The results from the real-world data analysis of the electronic health records that Pfizer completed for the expanded indication will be presented at an upcoming medical meeting.1,2
FDA Expands Approved Use of Metastatic Breast Cancer Treatment to Include Male Patients. United States Food and Drug Administration. https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm635276.htm?utm_campaign=040419_PR_FDA%20expands%20use%20of%20breast%20cancer%20treatment%20to%20include%20male%20patients&utm_medium=email&utm_source=Eloqua. Published April 4, 2019. Accessed April 5, 2019.
U.S. FDA Approves Ibrance (Palbociclib) for the Treatment of Men with HR+, HER2- Metastatic Breast Cancer. Pfizer, Inc. https://www.pfizer.com/news/press-release/press-release-detail/u_s_fda_approves_ibrance_palbociclib_for_the_treatment_of_men_with_hr_her2_metastatic_breast_cancer. Published April 4, 2019. Accessed April 5, 2019.