Orserdu (elacestrant) is a prescription drug that’s used to treat breast cancer in certain situations. Orserdu comes as an oral tablet.

Orserdu is a type of hormone therapy. It’s used in certain adults to treat estrogen receptor-positive, HER2-negative breast cancer with a specific gene change.* The cancer must be advanced or metastatic.† Doctors prescribe Orserdu if the cancer has progressed (worsened) after treatment with another hormone therapy.

To learn more about Orserdu’s uses, see the “What is Orserdu taken for?” section below.

* Doctors call this gene change a mutation.
† Advanced means it has spread within the chest and/or other areas. Metastatic means it has spread to farther areas of the body.

Orserdu basics

Orserdu contains the active ingredient elacestrant. (An active ingredient is what makes a drug work.) It belongs to a group of drugs called hormone therapy.

Orserdu is a brand-name medication. A generic version of the drug isn’t available currently.

Like most drugs, Orserdu may cause mild to serious side effects. The lists below describe some of the more common side effects this drug may cause. These lists don’t include all possible side effects.

Keep in mind that side effects of a drug can depend on:

  • your age
  • other health conditions you have
  • other medications you take

Your doctor or pharmacist can tell you more about the potential side effects of Orserdu. They can also suggest ways to help reduce side effects.

Mild side effects

Here’s a list of some of the mild side effects that Orserdu can cause. To learn about other mild side effects, talk with your doctor or pharmacist or read Orserdu’s prescribing information.

Mild side effects of Orserdu that have been reported include:

  • muscle or body aches
  • nausea
  • fatigue (low energy)
  • vomiting
  • low appetite
  • diarrhea or constipation
  • headache
  • pain in the abdomen (belly)
  • hot flashes
  • indigestion
  • mild allergic reaction*

* To learn more about this side effect, see the “Allergic reaction” section below.

Mild side effects of many drugs may go away within a few days to a couple of weeks. But if they become bothersome, talk with your doctor or pharmacist.

Serious side effects

Serious side effects from Orserdu can occur, but they aren’t common. If you have serious side effects from Orserdu, call your doctor right away. But if you think you’re having a medical emergency, you should call 911 or your local emergency number.

Serious side effects of Orserdu that have been reported include:

* To learn more about this side effect, see the “Allergic reaction” section below.

Allergic reaction

An allergic reaction is possible with Orserdu use. But this side effect wasn’t reported in studies of the drug.

Symptoms of a mild allergic reaction can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include swelling under your skin, usually in your eyelids, lips, hands, or feet. They can also include swelling of your tongue, mouth, or throat, which can cause difficulty breathing.

Call your doctor right away if you have an allergic reaction to Orserdu. But if you think you’re having a medical emergency, call 911 or your local emergency number.

Whether you have health insurance or not, cost may be a factor when you’re considering Orserdu. What you’ll pay for Orserdu may depend on several things. These include your treatment plan and the pharmacy you use.

Here are a few things to consider regarding cost:

  • Cost information and savings coupons: You can visit Optum Perks to get price estimates of what you’d pay for Orserdu when using coupons from the site. (Note: Optum Perks coupons cannot be used with any insurance copays or benefits.)
  • Savings program: If you have questions about how to pay for your prescription, talk with your doctor or pharmacist. A program called Stemline ARC may also be available.

You can also check out this article to learn more about saving money on prescriptions.

Orserdu is a type of hormone therapy for breast cancer. Specifically, Orserdu is approved for use in females* who have gone through menopause and in adult males.* It’s used to treat breast cancer that’s all of the following:

  • estrogen receptor (ER)-positive
  • HER2-negative
  • ESR1-mutated, which means the cancer has a mutation (abnormal change) in ESR1 (a gene)
  • advanced (has spread within the chest and/or other areas) or metastatic (has spread to farther areas of the body)
  • has progressed (worsened) after treatment with at least one other hormone therapy, such as fulvestrant (Faslodex)

With ER-positive breast cancer, estrogen can help the cancer grow. Orserdu treats breast cancer by blocking a certain receptor (a type of protein) on cancer cells. This helps prevent estrogen from getting to the cancer. In turn, that can help slow or stop the cancer’s growth.

* In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Find answers to some commonly asked questions about Orserdu.

Is Orserdu considered a chemotherapy drug?

No, it’s not a chemotherapy drug. Orserdu is a type of hormone therapy.

Chemotherapy drugs work by destroying cancer cells. They also can destroy other cells that multiply quickly.

Hormone therapy doesn’t destroy cancer cells or other cells. Instead, it helps prevent hormones from affecting cancer cells. These drugs can slow or stop the cancer’s growth.

If you have questions about different breast cancer treatments, talk with your doctor or pharmacist.

Does Orserdu cause long-term side effects?

It’s unlikely. Long-term side effects weren’t reported in studies of Orserdu.

But the drugmaker warns that Orserdu may cause fertility problems in people who can conceive or reproduce. This warning is based on animal studies, so it isn’t known for certain how the drug affects fertility in people.

If you’re concerned about your ability to have children in the future, talk with your doctor before starting Orserdu. They can discuss family planning options with you.

How does Orserdu compare with Faslodex?

Both Orserdu and Faslodex (fulvestrant) are used to treat breast cancer in certain situations. Orserdu and Faslodex belong to the same group of drugs. Both are types of hormone therapy.

The key difference is that Orserdu may be effective for treating breast cancer that has become resistant to Faslodex. This means the cancer has stopped responding to Faslodex. Orserdu is approved in certain situations to treat breast cancer that’s progressed (worsened). It must have progressed after treatment with at least one other hormone therapy, such as Faslodex.

These drugs also come in different forms and have different dosages. Orserdu comes as an oral tablet. You usually take it once daily. In contrast, a healthcare professional gives you injections of Faslodex. You usually receive one or more injections per month.

If you have other questions about how Orserdu and Faslodex compare, talk with your doctor. They can recommend suitable treatments for you.

Your doctor will recommend the dosage of Orserdu that’s right for you. Below are commonly used dosages, but always take the dosage your doctor prescribes.

Form and strengths

Orserdu is available as an oral tablet in two strengths: 86 milligrams (mg) and 345 mg.

Recommended dosage

The usual recommended dosage of Orserdu is 345 mg once daily.

If you develop certain side effects while taking Orserdu, your doctor may pause or stop your treatment. If they restart your treatment, they may then prescribe a lower dosage of Orserdu. This may help prevent the side effects from coming back or make them less bothersome.

Your doctor may prescribe a lower dosage of Orserdu if you have liver problems.

Questions about taking Orserdu

Below are some common questions about taking Orserdu.

  • Can Orserdu be chewed, crushed, or split? No, you should not chew, crush, or split Orserdu tablets. You should swallow them whole. If you have difficulty swallowing pills, check out this article or ask your doctor or pharmacist for advice.
  • Should I take Orserdu with food? Yes, you should take it with food. Taking Orserdu with food helps lower your chance of getting nausea and vomiting side effects.
  • Is there a best time of day to take Orserdu? You can take Orserdu at any time of day. But it’s best to take it at the same time each day. This ensures a more consistent level of the drug in your body, which helps Orserdu work effectively.
  • What if I miss a dose of Orserdu? If you miss a dose of Orserdu by more than 6 hours, skip the missed dose. Then take your next dose at the usual time the following day.
  • What if I vomit after taking Orserdu? If you vomit at any time after taking a dose of Orserdu, you do not need to repeat the dose. Instead, take your regular dose at the usual time the next day.
  • Will I need to take Orserdu long term? Orserdu is typically taken as a long-term treatment. You and your doctor can discuss whether it’s safe and effective for your condition. If you agree that it is, you’ll likely take it long term.

Overdose

Do not take more Orserdu than your doctor prescribes, as this can lead to harmful effects.

What to do in case you take too much Orserdu

Call your doctor if you think you’ve taken too much Orserdu. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. But if you have severe symptoms, immediately call 911 or your local emergency number. Or go to the nearest emergency room.

Below is important information you should consider before taking Orserdu.

Interactions

Taking a drug with certain medications, vaccines, foods, and other things can affect how the drug works. These effects are called interactions.

Orserdu can interact with several other medications. It can also interact with certain supplements as well as certain foods.

Before starting Orserdu treatment, talk with your doctor and pharmacist. Tell them about all prescription, over-the-counter, and other drugs you take. Also, tell them about any herbs or vitamins and supplements you take. Sharing this information can help you avoid potential interactions.

If you have questions about drug interactions that may affect you, talk with your doctor or pharmacist.

Drug interactions

Below are examples of medications that can interact with Orserdu. This list does not contain all drugs that may interact with Orserdu. If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Drug group or drug nameDrug example
medications that can block or slow the activity of a certain liver enzyme itraconazole (Sporanox)
medications that can increase the activity of a certain liver enzymerifampin (Rifadin)

Orserdu and alcohol

Alcohol is not known to interact with Orserdu.

Talk with your doctor to determine whether it’s safe for you to consume alcohol during Orserdu treatment.

Other interactions

Orserdu may interact with other substances such as:

  • Vitamins, herbs, or supplements: Orserdu may interact with St. John’s wort. Your doctor likely will recommend that you avoid taking this supplement during your Orserdu treatment. Interactions with other supplements are possible. So check with your doctor or pharmacist before taking any of these products with Orserdu.
  • Foods: Orserdu may interact with grapefruit and grapefruit juice. Your doctor likely will recommend that you avoid consuming grapefruit products during Orserdu treatment.

Pregnancy and breastfeeding

Orserdu is not safe to take during pregnancy or while breastfeeding.

Note that this medication is approved to treat breast cancer only in females* who have gone through menopause and in adult males.* As such, Orserdu is meant to be taken only by people who cannot become pregnant or breastfeed.

* In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Birth control

Orserdu is not safe to take during pregnancy.

Males* with partners who can become pregnant should use birth control (such as condoms). They should use it during treatment and for at least 1 week after the last dose.

Females* who can become pregnant should use birth control during treatment and for at least 1 week after their last dose. But this medication is approved to treat breast cancer only in females who have gone through menopause and adult males. As such, Orserdu is not approved for use in females who can become pregnant.

* In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Warnings

Orserdu can sometimes cause harmful effects in people who have certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Orserdu is a good treatment option for you.

Talk with your doctor about your health history before you take Orserdu. Be sure to tell them if any of the following factors apply to you:

Other drugs are available that can treat your condition. If you’d like to explore an alternative to Orserdu, talk with your doctor. They can tell you about other medications that might work well for you.

The following drugs are similar to Orserdu:

If you have questions about taking Orserdu, talk with your doctor or pharmacist. Questions you may want to ask include:

  • How often will I need to have blood tests to monitor for side effects of Orserdu?
  • Do any of my current medications or supplements interact with Orserdu?
  • What lifestyle changes can you recommend to help prevent high cholesterol and high triglycerides with Orserdu?

To get information on different conditions and tips for improving your health, subscribe to any of Healthline’s newsletters. You may also want to check out the online communities at Bezzy. It’s a place where people with certain conditions can find support and connect with others.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.