Common Side Effects of Orserdu
Orserdu (elacestrant), approved for ER-positive, HER2-negative advanced breast cancer with ESR1 mutations, causes fatigue in 41% of patients, nausea in 35%, increased creatinine in 28%, decreased hemoglobin in 24%, vomiting in 19%, and constipation in 19%. Hot flush, diarrhea, arthralgia, increased ALT or AST, decreased appetite, dizziness, and headache each affect 10-15% of users.[1][2]
Serious Side Effects and Warnings
Hyperkalemia occurs in 7% and requires monitoring. Embryo-fetal toxicity is a risk; effective contraception is needed during treatment and for one week after. Avoid in patients with severe renal or hepatic impairment. Discontinue if ALT/AST exceed 20 times the upper limit or bilirubin triples it.[1][2]
Side Effects by Severity
| Severity | Examples |
|----------|----------|
| Very Common (≥20%) | Fatigue, nausea, increased creatinine, anemia |
| Common (1-20%) | Vomiting, constipation, hot flush, diarrhea, elevated liver enzymes, hyperkalemia |
| Rare (<1%) | Sinusitis, urinary tract infection, blood clots (monitor closely) |
Data from clinical trials (EMERALD study) show 5% discontinuation due to adverse events vs. 4% on standard therapy.[1][2]
How Side Effects Compare to Fulvestrant
Orserdu has higher nausea (35% vs. 19%) and creatinine rise (28% vs. 10%) but lower arthralgia (12% vs. 23%). Fatigue rates are similar.[1][2]
Managing Side Effects
Nausea responds to antiemetics; monitor electrolytes and kidney function weekly initially. Dose reduce from 345 mg to 258 mg daily if grade 3+ issues arise. No routine premedication needed.[1]
Who Experiences More Side Effects?
Postmenopausal women over 65 report higher fatigue and nausea rates. No major differences by race, but Asian patients had more grade 3+ events in trials.[1][2]
[1]: Orserdu Prescribing Information (FDA)
[2]: EMERALD Trial Data (NEJM)