Comparing Emerging Classes of Endocrine Therapies in Breast Cancer

EP: 1.The Present and Future of Endocrine Therapy in Breast Cancer

EP: 2.Emerging Endocrine Therapies in Breast Cancer Treatment

EP: 3.Upcoming Endocrine Therapy Developments Excite in Breast Cancer

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EP: 4.Comparing Emerging Classes of Endocrine Therapies in Breast Cancer

EP: 5.Navigating the Evolving Landscape of Endocrine Therapy in Breast Cancer

EP: 6.What’s Next in Breast Cancer Treatment After Endocrine Therapy Progression?

Erika Hamilton, MD, director of Breast Cancer Research at the Sarah Cannon Research Institute, discusses the different classes of endocrine therapies and how they compare to one another.

Endocrine therapies for breast cancer are rapidly evolving with agents like selective estrogen receptor degraders (SERDs) and proteolysis-targeting chimeras (PROTACs), complete estrogen receptor antagonists (CERANs), selective estrogen receptor modulators (SERMs), selective estrogen receptor covalent antagonists (SERCAs), and more.

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0:09 | So, currently we really have several. Tamoxifen [Soltamox] is our oldest endocrine agent, and that is a SERM, a selective estrogen receptor modulator. We also have aromatase inhibitors. This is our mainstay of endocrine therapy, I would say. Then there is fulvestrant, which is an intramuscular injection form of a selective estrogen receptor degrader [SERD]. We now have new SERDs coming, and they are different because they are oral, not intramuscular, and have better activity. One of them is approved, elacestrant, for patients with ESR1 mutations, and there are many more oral SERDs on the way.

0:56 | And then, certainly, we have PROTACs, which work by using an E3 ligase molecule to bind the target, in this case, the estrogen receptor. This leads to the ubiquitination of the estrogen receptor, marking it for degradation by the proteasome. I tell my patients it "chews up" the estrogen receptor and "spits it out.”

1:20 | We also have a novel SERM called lasofoxifene, which is a tamoxifen-like drug. It offers some advantages in terms of adverse effects because it does not act as a full anti-estrogen throughout the body—it acts as a pro-estrogen in some areas and an anti-estrogen in others. Finally, there are CRANs, circSERMs, and other new agents, all of which essentially work to block estrogen's interaction with cancer cells. They either lower estrogen levels so there’s nothing to bind, get rid of estrogen receptors on the cell surface, or block estrogen receptors so that estrogen cannot bind to them.