Elacestrant

What it is and how it works

Mechanism of Action Elacestrant is an estrogen receptor antagonist that binds to estrogen receptor-alpha (ERα). In ER-positive (ER+) HER2-negative (HER2-) breast cancer cells, elacestrant inhibited 17β-estradiol mediated cell proliferation at concentrations inducing degradation of ERα protein mediated through proteasomal pathway. Elacestrant demonstrated in vitro and in vivo antitumor activity including in ER+ HER2- breast cancer models resistant to fulvestrant and cyclin-dependent kinase 4/6 inhibitors and those harboring estrogen receptor 1 gene ( ESR1 ) mutations.

Mechanism class: Estrogen Receptor Antagonists · P-Glycoprotein Inhibitors · Breast Cancer Resistance Protein Inhibitors

Indications

is indicated for the treatment of postmenopausal women or adult men with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)‑negative, ESR1 -mutated advanced or metastatic breast cancer, as detected by an FDA-authorized test , with disease progression following at least one line of endocrine therapy. ORSERDU is an estrogen receptor antagonist indicated for: treatment of postmenopausal women or adult men, with ER-positive, HER2-negative, ESR1 -mutated advanced or metastatic breast cancer, as detected by an FDA-authorized test, with disease progression following at least one line of endocrine therapy

Dosage and administration (summary)

Select patients for treatment with ORSERDU based on the presence of ESR1 mutations. The recommended dosage of ORSERDU is one 345 mg tablet taken orally, once daily, with food Dose interruption, reduction, or permanent discontinuation may be required due to adverse reactions. Patient Selection Select patients for treatment of ER-positive, HER2-negative advanced or metastatic breast cancer with ORSERDU based on the presence of ESR1 mutation(s) in plasma specimen using an FDA-authorized test . Information on FDA-authorized tests for detection of ESR1 mutations in breast cancer is available at: http://www.fda.gov/CompanionDiagnostics.

Contraindications

None. None

Warnings and precautions

Dyslipidemia : ORSERDU may cause hypercholesterolemia and hypertriglyceridemia. Monitor lipid profile prior to starting treatment and periodically thereafter. Embryo-Fetal Toxicity : ORSERDU can cause fetal harm. Advise of the potential risk to a fetus and to use effective contraception. ( 5.2 , 8.1 , 8.3 ) Dyslipidemia Hypercholesterolemia and hypertriglyceridemia occurred in patients taking ORSERDU at an incidence of 30% and 27%, respectively. The incidence of Grade 3 and 4 hypercholesterolemia and hypertriglyceridemia were 0.9% and 2.2%, respectively .

Pregnancy

Pregnancy Risk Summary Based on findings in animals and its mechanism of action, ORSERDU can cause fetal harm when administered to a pregnant woman . There are no available human data on ORSERDU use in pregnant women to inform the drug-associated risk.

Storage and supply

Storage and Handling Store at 20°C to 25°C (68°F to 77°F). Excursions permitted from 15°C to 30°C (59°F to 86°F). .

Source: Elacestrant (Orserdu) — US FDA prescribing information, 2026-06-24, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.