Orserdu (Elacestrant)

• Elacestrant is a selective estrogen receptor degrader used in the management of hormone‑responsive breast cancer.
• Advanced ER+/HER2‑negative breast cancer: provides an oral SERD option after progression on prior endocrine therapy.
• Metastatic hormone‑receptor‑positive breast cancer: helps delay disease progression and may improve progression‑free survival.
• Post‑menopausal ER‑positive breast cancer: offers a non‑injectable treatment alternative.

• Elacestrant binds to the ligand‑binding domain of the estrogen receptor (ER) with high affinity, inducing a conformational change that targets the receptor for proteasomal degradation. By reducing cellular ER levels, the drug blocks estrogen‑driven transcriptional activity and downstream proliferative signaling pathways, thereby inhibiting growth of ER‑dependent tumor cells. The degradation process also diminishes cross‑talk with growth factor receptors, enhancing anti‑tumor efficacy and overcoming resistance to conventional aromatase inhibitors.

Elacestrant may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Fatigue: general tiredness or lack of energy.
• Hot flashes: transient sensation of warmth.
• Diarrhea: loose stools, usually self‑limiting.
• Headache: mild cranial discomfort.

Serious or Rare Side Effects

• Thromboembolic events: deep vein thrombosis or pulmonary embolism.
• Interstitial lung disease: cough, dyspnea, and radiographic infiltrates.
• Severe liver injury: elevated transaminases, jaundice.
• QT interval prolongation: risk of cardiac arrhythmia.

Before initiating elacestrant therapy, several safety considerations should be reviewed.

• Pregnancy: avoid use due to potential teratogenic effects.
• Breastfeeding: not recommended as drug may be excreted in milk.
• Liver impairment: assess function; dose adjustment may be required.
• Concomitant QT‑prolonging drugs: monitor ECG for arrhythmia risk.
• Drug interactions: evaluate CYP3A4 inhibitors or inducers.
• Store at below 25°C: keep in the original packaging, protect from moisture and light.

Elacestrant interacts with several medicines that affect its metabolism or cardiac safety.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may increase elacestrant exposure.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce efficacy.
• QT‑prolonging agents (e.g., amiodarone, sotalol): increase risk of cardiac arrhythmia.
• Other SERDs or selective estrogen modulators: may cause additive hormonal effects.
• Anticoagulants (e.g., warfarin): heightened risk of thrombotic events.

Moderate Interactions (Monitor Closely)

• Moderate CYP3A4 inhibitors (e.g., erythromycin, fluconazole): may modestly raise plasma levels.
• Hormonal therapies (e.g., aromatase inhibitors): monitor for overlapping toxicity.
• Statins metabolized by CYP3A4 (e.g., simvastatin): observe for increased concentrations.
• Antidepressants affecting QT (e.g., citalopram): watch ECG changes.
• Herbal supplements (e.g., St. John’s wort): possible induction of metabolism.