Class: Selective Estrogen Receptor Degrader (SERD)

Therapeutic Indications

• Treatment of postmenopausal women with hormone receptor-positive, advanced or metastatic breast cancer, especially after progression on prior endocrine therapy (e.g., aromatase inhibitors).
• Used as monotherapy or in combination with targeted agents (e.g., CDK4/6 inhibitors).

Mechanism of Action

• Binds to estrogen receptors (ER) with high affinity, causing receptor downregulation and degradation.
• Completely blocks estrogen signaling, leading to inhibition of hormone-driven tumor growth in ER-positive breast cancer.

Dosing

• Administered as intramuscular injection, typically 500 mg on days 0, 14, 28, then monthly thereafter.

Common Adverse Effects

• Injection site reactions
• Hot flashes
• Fatigue
• Nausea
• Back pain

Pharmacist Considerations

• Counsel patients about the intramuscular injection schedule and possible injection site discomfort.
• Monitor for menopausal symptoms and manage accordingly.
• Be aware of drug interactions when combined with targeted therapies.
• Support adherence to scheduled dosing to maintain efficacy.