Dr Joanne Mortimer Discusses Novel Oral SERD ZN-c5 in ER-Positive Breast Cancer

City of Hope's Joanne Mortimer, MD, a medical oncologist and director of the Women's Cancer Program, discusses a poster presentation from the 2020 San Antonio Breast Cancer Symposium.

Joanne Mortimer, MD, director of the women's cancer program at City of Hope, discusses early findings of a study on the oral selective estrogen receptor downregulator (SERD) ZN-c5 being presented at the 2020 San Antonio Breast Cancer Symposium.


Your poster presentation is a dose escalation study of the novel oral SERD ZN-c5 in women with ER-positive, HER2-negative advanced/metastatic breast cancer. Can you discuss the key findings and the role of selective estrogen receptor degraders in breast cancer treatment?

Currently, we have 1 drug that is in the category of SERDs—selective estrogen receptor downregulators—and that's fulvestrant, or Faslodex is the trade name. And this is a shot that's 5 cc's in each buttock once a month, and you get an extra dose in the first month. And it's a very effective drug and it's effective in particular types of estrogen receptor-positive breast cancers over other oral agents that are available. So it's a very important drug in the management of women who have metastatic, hormone receptor-positive breast cancer.

The problem with the drug is that it requires that the patient come in and that they have a 5-cc injection each buttock, which is not pleasant. Otherwise, this drug is very well tolerated with very few side effects. The poster is about an oral agent in this category that hopefully will supplant or maybe add to our armamentarium of hormone therapies in metastatic breast cancer. This poster provides the results of 15 patients who have started this therapy, and they were heavily pretreated. The median number of previous hormone treatments was 3, all had received at least 1 dose of chemotherapy. Ultimately, 10 of the 15 women had at least stabilization of their disease. This is a very optimistic finding for a new drug that maybe will not require the patient to come in to get an intramuscular injection, and so there's reason for optimism with this agent.