What is Elacestrant used for?

estrogen receptor positive, HER2 negative breast cancer with an ESR1 gene change that has grown after other hormone therapy, in women after menopause and in men.

What are the common side effects of Elacestrant?

Muscle or joint aches. Feeling sick to your stomach or throwing up. Higher cholesterol and blood fats. Feeling tired or weak. Not feeling hungry or losing weight. Constipation or diarrhea. Headache. Hot flashes.

When should I call my care team while taking Elacestrant?

Vomiting that will not stop; Feeling dizzy or faint, or not able to keep fluids down; Chest pain or pressure, or a racing or pounding heartbeat; Swelling, pain, or warmth in one leg, or sudden shortness of breath.

Elacestrant

Say it: el-a-SES-trant · Brand names: Orserdu

Elacestrant is a hormone blocking pill that attaches to and breaks down the estrogen receptor in breast cancer cells.

What it is

Many breast cancers use the hormone estrogen to grow. Elacestrant attaches to the estrogen receptor on cancer cells and helps the body break it down. It can work even when the receptor has a change called an ESR1 mutation.

Often used for

estrogen receptor positive, HER2 negative breast cancer with an ESR1 gene change that has grown after other hormone therapy, in women after menopause and in men

How you get it

Elacestrant is a pill you take by mouth at home, once a day with food. Your schedule may be different.

Common side effects and what helps

Muscle or joint aches. Gentle movement and stretching may help.
Feeling sick to your stomach or throwing up. Eat small meals and ask your team about anti-nausea medicine.
Higher cholesterol and blood fats. You will have blood tests to check.
Feeling tired or weak. Rest when you need to, and try short walks.
Not feeling hungry or losing weight. Try small, frequent meals and snacks.
Constipation or diarrhea. Drink fluids and tell your team if it does not get better.
Headache. Ask your team which pain medicines are safe.
Hot flashes. Dress in layers and keep cool.

Call your care team right away if you have

Vomiting that will not stop
Feeling dizzy or faint, or not able to keep fluids down
Chest pain or pressure, or a racing or pounding heartbeat
Swelling, pain, or warmth in one leg, or sudden shortness of breath

Before you start, tell your team

If you are pregnant, may become pregnant, or are breastfeeding
If you have high cholesterol
If you have liver problems
All the medicines, vitamins, and herbal products you take, since some can change how this medicine works

Good to know

You will have blood tests to check your cholesterol and blood fats before starting and during treatment.
This medicine can harm an unborn baby. Use birth control during treatment and for some time after. Ask your team how long.

At home

Take the tablet at about the same time each day with food.
Swallow the tablet whole.
If you miss a dose or throw up after taking it, ask your team what to do. Do not take extra pills to make up for it.
Store the pills at room temperature in the original bottle, away from children and pets.

Questions to ask

How long will I take this medicine?
Is it safe to take my other medicines, vitamins, or supplements with this one?
How will we know if this medicine is working?
Which side effects should I call about right away, and which can wait until my next visit?

Side effect guides

Sources

Quick answers

What is Elacestrant?: Elacestrant is a hormone blocking pill that attaches to and breaks down the estrogen receptor in breast cancer cells. Brand names: Orserdu.
What is Elacestrant used for?: estrogen receptor positive, HER2 negative breast cancer with an ESR1 gene change that has grown after other hormone therapy, in women after menopause and in men.
How is Elacestrant given?: Elacestrant is a pill you take by mouth at home, once a day with food. Your schedule may be different.
What are the common side effects of Elacestrant?: Muscle or joint aches. Feeling sick to your stomach or throwing up. Higher cholesterol and blood fats. Feeling tired or weak. Not feeling hungry or losing weight. Constipation or diarrhea. Headache. Hot flashes.
When should I call my care team while taking Elacestrant?: Vomiting that will not stop; Feeling dizzy or faint, or not able to keep fluids down; Chest pain or pressure, or a racing or pounding heartbeat; Swelling, pain, or warmth in one leg, or sudden shortness of breath.

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.