Orserdu (elacestrant): What to Expect, Side Effects, and More
Orserdu (chemical name: elacestrant) is a type of medicine called a selective estrogen receptor downregulator (SERD). It’s used to treat estrogen receptor-positive, HER2-negative breast cancer that has an ESR1 mutation and has spread to other areas of the body. The medicine is typically prescribed to men or women who’ve gone through menopause and is used if cancer did not respond to, or has started to grow after initally responding to, another hormonal medicine.
See Orserdu prescribing information.
How Orserdu works
The ESR1 gene makes estrogen receptors, which receive signals from estrogen that tell the cancer to grow. It’s estimated that up to 40% of advanced-stage or metastatic, estrogen receptor-positive, HER2-negative breast cancers have an ESR1 mutation.
Orserdu blocks the effects of estrogen on hormone receptor-positive breast cancer cells by sitting in the estrogen receptors on the cells. If Orserdu is in the receptor, estrogen can’t attach to the cancer cell and the cell doesn’t receive estrogen’s signals to grow and multiply.
Orserdu also changes the shape of the estrogen receptors so they don’t work as well.
What to expect during Orserdu treatment
Orserdu is a pill taken by mouth. The recommended dosage is one 345 mg tablet taken with food once daily.
Orserdu side effects
Like almost all breast cancer medicines, Orserdu can cause side effects, some of them serious.
The most common side effects of Orserdu are:
Orserdu also may cause serious side effects, including hypercholesterolemia and hypertriglyceridemia.
Hypercholesterolemia means your low-density lipoprotein (LDL), also called bad cholesterol, is too high. If this happens, fat can collect in your arteries, which increases your risk of heart attack and stroke.
Hypertriglyceridemia means you have too many triglycerides in your blood. Hypertriglyceridemia also increases your risk of heart attack and stroke.
Before you start taking Orserdu, your doctor should test the amount of cholesterol and triglycerides in your blood. These tests will be repeated as you continue to take the medicine.
Orserdu may cause harm to an unborn baby. You should not take Orserdu if you are pregnant, trying to get pregnant, or if there is any chance that you could be pregnant. Women should use an effective non-hormonal type of birth control while taking Orserdu. Ask your doctor which type of non-hormonal birth control would be best for you. Women should use birth control for at least one week after their last dose of Orserdu.
If you’re a man taking Orserdu and have a partner who can become pregnant, your partner should use birth control for at least one week after your last dose.
Real patient reviews
Members of our community discuss their experiences with Orserdu in the community forum. Here are some of their comments. Remember, it's very important to talk to your doctor about any side effects you're having and ask about ways to manage them.
“Into my second month with Orserdu with no side effects, which is fab.” —chico
“Now on Orserdu eight months. My tumor markers had gone down to the lowest they had been since 2016. I can still eat and have not lost weight, so to me, it’s working.” —kbl
Read more in our Orserdu discussion forum.
Orserdu drug interactions
There are certain medicines, supplements, and foods you should avoid if you’re taking Orserdu.
You should not take CYP3A4 inducers because they decrease the effects of Orserdu. This class of medicine includes Rifamate (chemical name: rifampin), an antibiotic used to treat tuberculosis, and Carbatrol (chemical name: carbamazepine), which is used to control certain types of seizures in people with epilepsy. St. John’s wort, an herbal supplement, is also considered a CYP3A4 inducer.
You should not take CYP3A4 inhibitors because they increase the effects of Orserdu. This class of medicine includes Nizoral (chemical name: ketoconazole) and Sporanox (chemical name: itraconazole), which are used to treat fungal infections; Reyataz (chemical name: atazanavir), used to treat HIV; and nefazodone, used to treat depression. Goldenseal, an herbal supplement, is also considered a CYP3A4 inhibitor.
You should not drink grapefruit juice or eat grapefruit because they can increase the effects of Orserdu.
It’s important to tell your doctor about all other medicines, vitamins, and supplements you take so they can determine whether Orserdu is right for you.
Paying for Orserdu
The cost of Orserdu may vary. The price you’ll pay depends on the drug manufacturer, your health insurance provider and plan, where you live, and the pharmacy you use.
Note: Your insurance company may require you to get prior authorization before covering Orserdu.
If your doctor prescribes Orserdu and you have problems paying for it or getting health insurance coverage, the Stemline Therapeutics ARC program may be able to help. For more information, call 1-833-478-3654.
Learn more about financial assistance and medicine cost-lowering tips.
— Last updated on June 17, 2025 at 7:54 PM