Selective Estrogen Receptor Degrader (SERD)

Definition:

• SERDs are a class of endocrine therapy agents that bind to estrogen receptors (ER) and induce their conformational change, leading to receptor degradation and downregulation.

Mechanism of Action:

• Unlike selective estrogen receptor modulators (SERMs) that block or activate ER depending on tissue, SERDs irreversibly reduce ER protein levels, effectively eliminating estrogen signaling in ER-positive breast cancer cells.

Clinical Use:

• Used primarily in postmenopausal women with hormone receptor-positive metastatic or advanced breast cancer, especially after resistance to other endocrine therapies.
• Fulvestrant is the prototypical and only currently widely used SERD.

Pharmacist Considerations:

• SERDs are typically administered via intramuscular injection (e.g., fulvestrant).
• Monitor for menopausal symptoms and injection site reactions.
• Counsel on adherence to injection schedule for optimal receptor suppression.
• Be aware of potential drug interactions, especially when combined with targeted therapies.