Orserdu (Elacestrant) 86 mg
Oral selective estrogen receptor degrader (SERD) for ER-positive, HER2-negative, ESR1-mutated advanced breast cancer
Quick Facts About Orserdu
Key Takeaways About Orserdu
- Precision endocrine therapy: Orserdu is specifically designed for breast cancers with activating ESR1 mutations — a validated biomarker test is required before treatment
- Oral, once-daily: 345 mg (four 86 mg tablets) taken with food every day, offering a convenient alternative to intramuscular fulvestrant
- Dual mechanism: Blocks estrogen signaling and degrades the estrogen receptor, overcoming common resistance pathways after CDK4/6 inhibitors
- Generally well tolerated: Most side effects are gastrointestinal or musculoskeletal and manageable with supportive care, dose interruption or dose reduction
- Important interactions: Avoid strong or moderate CYP3A4 inducers and inhibitors, including grapefruit juice and St John's Wort; many common medicines need review
What Is Orserdu and What Is It Used For?
Orserdu (elacestrant) is an oral anti-cancer medicine belonging to a class called selective estrogen receptor degraders (SERDs). It is approved to treat postmenopausal women and adult men with estrogen receptor (ER)-positive, HER2-negative, locally advanced or metastatic breast cancer whose tumour carries an activating ESR1 mutation and has progressed after at least one prior line of endocrine therapy, including a CDK4/6 inhibitor.
Orserdu represents an important advance in the targeted treatment of hormone-sensitive breast cancer. In hormone receptor (HR)-positive breast cancer, the female sex hormone estrogen drives tumour growth by binding to the estrogen receptor (ER) inside cancer cells. Most patients initially respond well to endocrine therapies such as aromatase inhibitors (letrozole, anastrozole, exemestane), tamoxifen, or fulvestrant, frequently combined with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors. Over time, however, many tumours develop resistance — and a major mechanism of this resistance is the emergence of mutations in the ESR1 gene, which encodes the estrogen receptor itself.
ESR1 ligand-binding domain mutations lock the estrogen receptor in a constitutively active state, so that it can drive tumour growth even when estrogen levels are very low. These mutations are found in 30–40 % of patients whose hormone receptor-positive metastatic breast cancer progresses on an aromatase inhibitor. Historically this has been a difficult clinical scenario, because the mutated receptor is poorly inhibited by traditional endocrine therapies. Orserdu was specifically engineered to retain activity against these mutated receptors.
The active substance in Orserdu is elacestrant (as elacestrant dihydrochloride). Elacestrant binds tightly to the estrogen receptor, blocks its transcriptional activity, and promotes its degradation through the cellular proteasome system. By removing the receptor, elacestrant deprives hormone-sensitive cancer cells of the growth signals they depend on, even when an ESR1 mutation is present. Unlike fulvestrant, which must be given as a monthly intramuscular injection, elacestrant is an oral tablet that can be taken at home.
Approved Indication
The approved indication for Orserdu, according to the European Medicines Agency (EMA) and the U.S. Food and Drug Administration (FDA), is the treatment of postmenopausal women or adult men with:
- Estrogen receptor (ER)-positive breast cancer
- HER2-negative (human epidermal growth factor receptor 2-negative) disease
- Locally advanced or metastatic (stage IV) disease
- An activating ESR1 mutation, confirmed by a validated test
- Disease progression after at least one prior line of endocrine therapy that included a CDK4/6 inhibitor
Orserdu is intended as monotherapy (used on its own) in this setting. It is not approved for patients without an ESR1 mutation, nor for patients whose tumours are HER2-positive or hormone receptor-negative.
How Orserdu Works
At the molecular level, elacestrant functions both as a competitive antagonist of the estrogen receptor and as a degrader of the receptor protein. When elacestrant enters an ER-positive breast cancer cell, it binds to the ligand-binding pocket of the receptor with high affinity. This binding prevents estrogen from activating the receptor and blocks the transcription of genes that drive cell proliferation, including genes involved in DNA synthesis, mitosis and survival.
Just as importantly, elacestrant changes the shape of the receptor in a way that targets it for degradation by the cell's proteasome machinery. Over time, total levels of estrogen receptor in the cancer cell fall substantially. Preclinical studies show that elacestrant continues to suppress estrogen receptor signaling even when the receptor carries common activating mutations such as Y537S, Y537N, Y537C and D538G. This distinguishes it from aromatase inhibitors, which work by lowering estrogen levels and have little effect once a constitutively active receptor is present.
Clinical Evidence: the EMERALD Trial
Regulatory approval of Orserdu was based primarily on the pivotal EMERALD trial (NCT03778931), a phase 3, open-label, randomised study that enrolled 478 postmenopausal women and men with ER+/HER2− advanced breast cancer who had received one or two prior lines of endocrine therapy — including a CDK4/6 inhibitor — and up to one prior line of chemotherapy. Participants were randomised to receive either elacestrant 345 mg once daily or the investigator's choice of standard-of-care endocrine monotherapy (fulvestrant, anastrozole, letrozole or exemestane).
In the prespecified subgroup of patients with ESR1-mutated tumours, elacestrant approximately doubled median progression-free survival (PFS) compared with standard endocrine therapy. In the overall population, elacestrant also significantly improved PFS. These results established elacestrant as the first oral SERD to demonstrate a PFS benefit over standard-of-care endocrine therapy in a phase 3 trial and supported a precision-medicine approach based on ESR1 mutation testing.
Orserdu is not a cure for metastatic breast cancer. Its aim is to delay disease progression, preserve quality of life and postpone the need for chemotherapy. Treatment continues for as long as it is controlling the cancer and is tolerated, and should always be overseen by an oncologist experienced in breast cancer care.
What Should You Know Before Taking Orserdu?
Before starting Orserdu, your oncologist will confirm that your tumour is ER-positive, HER2-negative and carries an activating ESR1 mutation. You must not take Orserdu if you are allergic to elacestrant, if you are pregnant or breastfeeding, or if you are taking a strong CYP3A4 inducer. Liver function, lipids and drug interactions are carefully reviewed before and during treatment.
Orserdu is a targeted anti-cancer medicine that requires careful patient selection, baseline testing and ongoing monitoring. Before prescribing, your healthcare team will review your medical history, current medications, organ function and cancer status in detail. Understanding the contraindications and precautions is essential for safe and effective use of this treatment.
Contraindications
You must not take Orserdu if:
- You are allergic (hypersensitive) to elacestrant or to any of the other ingredients of the tablets
- You are pregnant or believe you may be pregnant
- You are breastfeeding
- Your tumour does not carry an activating ESR1 mutation, or the mutation status has not been confirmed by a validated test
Tell your doctor about any serious allergic reaction to a medicine in the past, including swelling of the face or throat, difficulty breathing, or severe skin rashes, before starting Orserdu.
Warnings and Precautions
Talk to your doctor before taking Orserdu if any of the following apply to you:
- Liver disease: Elacestrant is mainly metabolised in the liver. Patients with moderate hepatic impairment require a lower daily dose and all patients have regular liver function tests during treatment
- Raised blood fats (lipids): Elacestrant can increase cholesterol and triglyceride levels. Baseline and periodic lipid profiles are recommended
- Pre-existing gastrointestinal problems: Nausea, vomiting, diarrhoea and dyspepsia are common — your doctor can prescribe supportive medicines
- Heart disease or QT-prolonging conditions: Clinically significant QT prolongation has not been observed, but caution is advised in patients with electrolyte abnormalities or on QT-prolonging drugs
- Bone health concerns: Like all endocrine therapies, long-term use can contribute to bone loss; your doctor may recommend DEXA scans and bone-strengthening measures
- Lactose intolerance: Orserdu tablets contain lactose monohydrate and should not be taken by patients with rare hereditary galactose intolerance, total lactase deficiency or glucose-galactose malabsorption
Based on its mechanism of action and animal data, Orserdu can cause fetal harm when administered to a pregnant person. Women of childbearing potential must have a negative pregnancy test before starting treatment and must use effective non-hormonal contraception during treatment and for at least one week after the last dose. Men with partners of childbearing potential should also use effective contraception during treatment and for at least one week after the last dose.
Biomarker Testing: ESR1 Mutation Status
A unique feature of Orserdu is that it is only prescribed after a molecular test has confirmed that the tumour carries an activating ESR1 mutation. Testing can be performed on:
- Circulating tumour DNA (ctDNA) from a blood sample — a minimally invasive "liquid biopsy"
- Formalin-fixed tumour tissue from a biopsy or surgical sample
Liquid biopsy is often preferred in the metastatic setting, because it samples DNA shed from all tumour sites simultaneously and can be repeated over time. Testing should be carried out in an accredited laboratory using a validated assay approved for ESR1 mutation detection. If no mutation is found, your oncologist will discuss alternative treatment options with you.
Baseline Tests and Monitoring
Before starting Orserdu, your team will typically perform:
- A full blood count and metabolic panel
- Liver function tests (ALT, AST, ALP, bilirubin)
- A fasting lipid profile (cholesterol, triglycerides)
- A pregnancy test in women of childbearing potential
- Assessment of your cancer status with imaging (CT, MRI or bone scan)
During treatment, these parameters are re-checked periodically — typically every 4 to 8 weeks initially, then every 3 months — so that side effects can be detected early and managed promptly. Your oncologist will also assess tumour response with regular imaging, usually every 8 to 12 weeks.
Pregnancy, Breastfeeding and Fertility
Orserdu is contraindicated during pregnancy because it can harm a developing fetus. If you become pregnant or suspect you are pregnant while taking Orserdu, stop the medicine and contact your oncologist immediately. Breastfeeding is also not recommended during treatment and for at least one week after the last dose, because it is not known whether elacestrant or its metabolites pass into human breast milk. Animal studies suggest possible effects on fertility; if future fertility is important to you, discuss fertility preservation options with your oncologist before starting treatment.
Driving and Operating Machinery
Orserdu has a minor influence on the ability to drive or operate machinery. However, some patients experience fatigue, dizziness or insomnia, which can impair concentration. If you feel unwell or tired after taking Orserdu, do not drive or use machines until you feel fully alert.
No dose adjustment is required based on age alone. However, older adults may be more likely to have kidney or liver impairment, take multiple medications, or have comorbid conditions, so treatment should be closely monitored.
Children and Adolescents
Orserdu has not been studied in children and adolescents under 18 years of age and is not indicated in this population. Breast cancer in premenopausal patients is managed with different strategies, which typically include ovarian suppression in combination with endocrine therapy.
How Does Orserdu Interact with Other Drugs?
Elacestrant is metabolised mainly by the CYP3A4 enzyme. Strong or moderate CYP3A4 inducers reduce its effectiveness and must be avoided, while strong or moderate CYP3A4 inhibitors increase side-effect risk. Orserdu can also raise blood levels of drugs transported by P-glycoprotein (P-gp) or BCRP. Always review all prescription medicines, over-the-counter products and herbal supplements with your oncologist or pharmacist.
Because elacestrant is primarily cleared by the cytochrome P450 enzyme CYP3A4 and is also a substrate for drug transporters such as P-glycoprotein (P-gp), many common medications can meaningfully change its exposure in the body. In some cases, co-administration can reduce the anti-cancer effect of Orserdu; in other cases, it can amplify side effects. A thorough medication review before starting treatment — and whenever a new medicine is added — is essential.
Major Interactions
| Interacting Drug / Class | Effect on Orserdu | Recommendation |
|---|---|---|
| Strong CYP3A4 inducers (rifampicin, rifabutin, carbamazepine, phenytoin, phenobarbital, St John's Wort, enzalutamide) |
Markedly decrease elacestrant blood levels and may reduce efficacy | Avoid concomitant use. If unavoidable, no Orserdu dose adjustment compensates adequately — consult your oncologist |
| Moderate CYP3A4 inducers (efavirenz, etravirine, modafinil, bosentan) |
Decrease elacestrant exposure | Avoid if possible; if required, monitor clinical response closely |
| Strong CYP3A4 inhibitors (ketoconazole, itraconazole, clarithromycin, ritonavir, cobicistat) |
Substantially increase elacestrant exposure, raising toxicity risk | Avoid. If essential, reduce Orserdu to a lower dose as advised by your oncologist and monitor carefully |
| Moderate CYP3A4 inhibitors (fluconazole, erythromycin, verapamil, diltiazem, grapefruit juice) |
Increase elacestrant exposure | Avoid if possible; monitor for increased side effects. Avoid grapefruit, grapefruit juice and Seville oranges during treatment |
| P-gp substrates with narrow therapeutic index (digoxin, dabigatran) |
Elacestrant can increase plasma levels of these drugs | Monitor digoxin levels and bleeding risk with dabigatran; dose adjustment may be needed |
| BCRP substrates (rosuvastatin, methotrexate, topotecan) |
Elacestrant can raise plasma levels of BCRP substrates | Monitor for toxicity of the BCRP substrate; consider dose adjustment |
| Acid-reducing drugs (proton pump inhibitors, H2 antagonists, antacids) |
Minimal clinically significant impact on elacestrant exposure | Can generally be continued; take Orserdu with food as recommended |
Minor Interactions and Practical Advice
Elacestrant is not a strong inhibitor or inducer of most other cytochrome P450 enzymes at therapeutic doses, so interactions with CYP2C9, CYP2C19 or CYP2D6 substrates are usually clinically manageable. However, the overall drug-interaction profile is complex, and any new medicine — including seemingly simple over-the-counter products — should be reviewed by your oncologist or pharmacist. Examples of minor but relevant considerations include:
- Non-steroidal anti-inflammatory drugs (NSAIDs): Can be used for pain relief but may irritate the stomach; paracetamol is often preferred
- Vitamin and mineral supplements: Generally safe, but avoid mega-dose regimens without medical advice
- Bisphosphonates or denosumab: Commonly co-prescribed for bone health; no pharmacokinetic interaction with elacestrant
- CDK4/6 inhibitors: Orserdu is currently approved as monotherapy; combination with CDK4/6 inhibitors is being studied but is not yet an approved regimen outside clinical trials
Foods, Drinks and Herbal Products
Certain foods and herbal products can significantly alter elacestrant metabolism:
- Grapefruit, grapefruit juice and Seville (bitter) oranges: Inhibit CYP3A4 and can increase elacestrant blood levels — avoid throughout treatment
- St John's Wort (Hypericum perforatum): A strong CYP3A4 inducer that can lower elacestrant blood levels — do not use
- Alcohol: No direct pharmacokinetic interaction, but alcohol can worsen nausea, fatigue and liver stress — moderate intake is advised
- Grapefruit supplements and extracts: Must also be avoided, as they carry the same enzyme-inhibiting compounds
Keep an up-to-date list of every medicine and supplement you take — including prescription drugs, over-the-counter products, vitamins, herbal remedies and recreational substances — and bring it to every oncology appointment. Ask your pharmacist before starting any new product while on Orserdu.
What Is the Correct Dosage of Orserdu?
The recommended dose of Orserdu is 345 mg (four 86 mg film-coated tablets) taken orally once daily with food, at about the same time each day. Treatment continues until disease progression or unacceptable toxicity. Dose reductions to 258 mg (three tablets) or 172 mg (two tablets) once daily are used to manage side effects or hepatic impairment.
Orserdu should only be prescribed and supervised by a physician experienced in the use of anti-cancer agents for breast cancer. Dosing is tailored to the individual patient based on tolerance, liver function and concomitant medications. Adherence to the prescribed schedule is important for maintaining effective drug levels.
Adults: Standard Dose
Recommended Dose: 345 mg once daily
Take four 86 mg film-coated tablets orally once daily with food, at approximately the same time each day. Swallow the tablets whole with a glass of water. Do not crush, chew, split or dissolve the tablets, and do not take any tablet that is broken, cracked or otherwise damaged. Food modestly increases absorption and may improve tolerance, so taking Orserdu with a meal is recommended.
Missed Dose
If you miss a dose of Orserdu
If you miss a dose by less than 6 hours, take it as soon as you remember. If more than 6 hours have passed, skip the missed dose and take the next dose at the regular scheduled time the following day. Do not take a double dose to make up for a missed tablet. If you vomit after taking Orserdu, do not take another dose on the same day — simply continue with the next scheduled dose.
Dose Reductions for Side Effects
If you experience significant side effects, your oncologist may temporarily interrupt Orserdu or reduce the dose step-wise:
- First dose reduction: 258 mg once daily (three 86 mg tablets)
- Second dose reduction: 172 mg once daily (two 86 mg tablets)
- Discontinuation: If the 172 mg daily dose cannot be tolerated, Orserdu is permanently discontinued
Dose modification guidance is provided in the EMA Summary of Product Characteristics and FDA Prescribing Information for specific situations such as nausea, vomiting, diarrhoea, fatigue, musculoskeletal pain or elevated liver enzymes.
Patients with Liver Problems
Hepatic impairment
In patients with mild hepatic impairment (Child-Pugh A), no dose adjustment is required. In patients with moderate hepatic impairment (Child-Pugh B), the recommended dose is 258 mg once daily (three 86 mg tablets). Orserdu has not been studied in patients with severe hepatic impairment (Child-Pugh C) and is not recommended in this population.
Patients with Kidney Problems
Renal impairment
No dose adjustment is needed in patients with mild or moderate renal impairment. Orserdu has not been specifically studied in patients with severe renal impairment or those on dialysis, so treatment decisions in this group should be individualised and discussed with the oncology team.
Elderly Patients
No specific dose adjustment is required based on age alone. Clinical trials of elacestrant included patients aged 65 and older, with no clinically meaningful differences in efficacy compared with younger patients. However, older patients may experience more gastrointestinal and musculoskeletal side effects and may benefit from closer monitoring and proactive supportive care.
Children
Orserdu is not recommended for use in children and adolescents under 18 years of age, because its safety and effectiveness have not been established in this age group and it is not indicated for any paediatric breast cancer setting.
Overdose
There is limited experience with elacestrant overdose. In clinical pharmacology studies, doses up to 1,000 mg per day were investigated; the most common findings were nausea, vomiting, abdominal discomfort and elevated liver enzymes. If you suspect an overdose, contact a poison control centre or go to the nearest emergency department immediately. There is no specific antidote. Management consists of stopping Orserdu and providing symptomatic and supportive care, including hydration, anti-emetics and monitoring of liver function.
Duration of Treatment
Treatment with Orserdu continues for as long as the cancer is controlled and side effects are manageable. Do not stop taking Orserdu without speaking to your oncologist, even if you feel well, because stopping prematurely can allow the cancer to progress. If you experience troublesome symptoms, contact your oncology team — in most cases, side effects can be managed with supportive medicines or a temporary dose reduction rather than stopping treatment altogether.
What Are the Side Effects of Orserdu?
The most common side effects of Orserdu are gastrointestinal (nausea, vomiting, diarrhoea, decreased appetite), musculoskeletal pain, fatigue and hot flushes. Laboratory abnormalities include increased cholesterol, triglycerides, creatinine and liver enzymes. Most side effects are mild to moderate, appear in the first weeks of treatment and improve with time or supportive care. Seek urgent medical advice for severe symptoms or signs of serious liver problems.
Like all medicines, Orserdu can cause side effects, although not everyone experiences them. Understanding what to expect and knowing when to seek medical help is an important part of staying safe and staying on treatment. Side-effect frequencies below are based on the EMERALD phase 3 trial and post-marketing surveillance reported in the EMA Summary of Product Characteristics and FDA Prescribing Information.
Contact your oncology team urgently or go to the nearest emergency department if you develop: yellowing of the skin or eyes (jaundice), dark urine, severe upper abdominal pain, persistent vomiting, very severe diarrhoea with dehydration, chest pain, shortness of breath, a sudden severe allergic reaction (swelling of the face or throat, difficulty breathing, widespread rash), or any symptom that feels life-threatening.
Side Effects by Frequency
Very Common (affects more than 1 in 10 patients)
- Musculoskeletal pain: back pain, bone pain, pain in arms or legs
- Nausea and vomiting
- Fatigue and generalised weakness (asthenia)
- Decreased appetite
- Joint pain (arthralgia)
- Diarrhoea
- Headache
- Hot flushes
- Constipation
- Abdominal pain and dyspepsia (indigestion)
- Increased cholesterol and triglycerides (dyslipidemia)
- Increased serum creatinine (usually without clinically significant kidney impairment)
- Elevated liver enzymes (ALT, AST)
- Decreased haemoglobin (anaemia)
- Hyponatraemia (low sodium) and hypocalcaemia (low calcium)
Common (affects up to 1 in 10 patients)
- Insomnia or disturbed sleep
- Dizziness
- Cough
- Shortness of breath (dyspnoea) during exertion
- Stomatitis (mouth inflammation) and mouth ulcers
- Taste disturbance (dysgeusia)
- Rash or dry skin
- Weight loss
- Urinary tract infection
- Peripheral oedema (swelling of ankles and feet)
Uncommon (affects up to 1 in 100 patients)
- Clinically significant hepatotoxicity with marked elevation of transaminases or bilirubin
- Pancreatitis
- Severe hypersensitivity reactions, including significant rash or angioedema
- QT interval prolongation on electrocardiogram
Rare (affects up to 1 in 1,000 patients)
- Severe drug-induced liver injury requiring hospitalisation
- Stevens-Johnson-like severe skin reactions (theoretical class risk; not yet definitively linked to elacestrant in published data)
Managing Common Side Effects
Most side effects of Orserdu can be effectively managed without stopping treatment. A few practical strategies are outlined below:
- Nausea and vomiting: Take Orserdu with food; eat small frequent meals; avoid fatty, spicy or strongly-smelling foods; use anti-emetic medicines such as ondansetron or metoclopramide as prescribed
- Diarrhoea: Drink plenty of clear fluids to prevent dehydration; eat a bland diet; use loperamide as directed; report severe or persistent diarrhoea promptly
- Fatigue: Prioritise rest and gentle exercise; maintain a regular sleep schedule; review other medicines that may contribute; consider referral to a cancer rehabilitation or exercise programme
- Musculoskeletal and joint pain: Paracetamol is often effective; hot packs, gentle stretching and physiotherapy can help; NSAIDs may be used with caution under medical supervision
- Hot flushes: Wear layered, breathable clothing; reduce triggers such as spicy food, alcohol and caffeine; discuss non-hormonal options (e.g. certain antidepressants or gabapentin) with your doctor
- Elevated lipids: Adopt a Mediterranean-style diet, increase physical activity and discuss statin therapy if needed
Monitoring for Liver Problems
Because elacestrant is cleared by the liver, liver function tests (ALT, AST, ALP and bilirubin) are checked before starting treatment, every 2 to 4 weeks for the first few months, and then periodically thereafter. Mild elevations are common and usually do not require changes to therapy. Significant increases may prompt dose reduction or a temporary pause. Tell your oncologist promptly if you notice yellowing of the eyes or skin, unusual fatigue, unexplained bruising, pain in the upper right abdomen or very dark urine.
Reporting Side Effects
It is important to report any suspected side effect — even if it seems minor — to your healthcare team. Early reporting helps identify problems quickly, adjust treatment if needed and contribute to the ongoing safety monitoring of Orserdu. You can also report suspected adverse reactions directly to your national pharmacovigilance authority (such as the EMA, FDA MedWatch, MHRA Yellow Card scheme or your local equivalent).
How Should You Store Orserdu?
Store Orserdu tablets in the original blister pack at room temperature below 30 degrees Celsius, away from moisture and out of the reach of children. Do not use Orserdu after the expiry date printed on the carton and blister. Return any unused or expired medicine to your pharmacy for safe disposal.
Correct storage of Orserdu helps ensure that the tablets remain stable and effective throughout your course of treatment. Because elacestrant is a cytotoxic anti-cancer medicine, safe storage and disposal also help protect other members of your household from accidental exposure.
Storage Conditions
- Store below 30°C (86°F) — typical room temperature in most homes
- Keep tablets in the original blister pack until you are ready to take them, to protect against moisture and light
- Store the blister pack in its outer carton for additional protection
- Avoid storing the medicine in humid places, such as the bathroom or kitchen near the sink
- Do not freeze Orserdu
Keep Out of Reach of Children
Store Orserdu in a secure location out of sight and out of reach of children and pets. Accidental ingestion of a cancer medicine can cause serious harm. If a child accidentally takes Orserdu, contact a poison control centre or emergency services immediately, taking the carton with you to show the medical team.
Expiry Date
Do not use Orserdu after the expiry date (EXP) printed on the outer carton and the blister. The expiry date refers to the last day of the month shown. Expired tablets may be less effective and should not be taken.
Safe Disposal
Unused, expired or damaged Orserdu tablets should be returned to your pharmacist for safe disposal. Do not dispose of medicines down the toilet, sink or in household rubbish, as they may pose risks to other people or the environment. Follow your country's specific take-back or disposal guidance for cytotoxic medicines.
Orserdu tablets are film-coated and should not be broken or crushed. If a tablet is accidentally damaged, avoid direct skin contact with the contents; clean the surface with detergent and water, and wash hands thoroughly. Caregivers who assist with administration may wish to wear gloves when handling broken tablets.
What Does Orserdu Contain?
Each Orserdu tablet contains 86 mg of elacestrant (as elacestrant dihydrochloride) as the active ingredient, together with inactive ingredients including microcrystalline cellulose, mannitol, lactose monohydrate, sodium starch glycolate and magnesium stearate. The film coating contains pigments such as iron oxides and titanium dioxide.
Knowing what is in your medicine can help you identify any ingredients you might be allergic to or need to avoid for dietary, religious or health reasons. The exact list of excipients may vary slightly between regions, so always refer to the patient information leaflet that comes with your specific pack.
Active Ingredient
The active substance in Orserdu is elacestrant, present as elacestrant dihydrochloride. Each film-coated tablet contains 86 mg of elacestrant (equivalent to approximately 100 mg of the dihydrochloride salt). The standard daily dose of 345 mg is provided by four tablets.
Excipients (Inactive Ingredients)
The tablet core contains:
- Microcrystalline cellulose (tablet structure)
- Mannitol (filler)
- Lactose monohydrate (filler)
- Sodium starch glycolate (disintegrant)
- Colloidal anhydrous silica (flow aid)
- Magnesium stearate (lubricant)
The film coating contains:
- Polyvinyl alcohol
- Titanium dioxide (E171)
- Macrogol (polyethylene glycol)
- Talc
- Iron oxide red (E172) and/or iron oxide yellow (E172) — for colour
Important Composition Notes
- Lactose: Orserdu contains lactose monohydrate. Patients with rare hereditary galactose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take Orserdu
- Sodium: Each tablet contains less than 1 mmol (23 mg) of sodium — essentially "sodium-free"
- Gluten: Orserdu tablets do not contain gluten
- Animal products: Orserdu tablets do not contain ingredients of animal origin
Appearance and Packaging
Orserdu 86 mg tablets are oval, film-coated tablets debossed with identifying marks from the manufacturer. They are supplied in blister packs, typically containing 28 or 30 tablets per carton (a monthly supply) depending on the country. Each carton includes a patient information leaflet with country-specific prescribing information.
Frequently Asked Questions About Orserdu
Orserdu (elacestrant) is an oral anti-cancer medicine used to treat postmenopausal women and adult men with estrogen receptor (ER)-positive, HER2-negative, locally advanced or metastatic breast cancer whose tumour carries an activating ESR1 mutation and has progressed after at least one line of endocrine therapy that included a CDK4/6 inhibitor. Orserdu works by binding to and degrading the estrogen receptor, blocking the hormonal signals that drive tumour growth.
The recommended dose is 345 mg once daily, given as four 86 mg film-coated tablets taken together with food at approximately the same time each day. Tablets should be swallowed whole with a glass of water and should not be crushed, split or chewed. Treatment continues for as long as it controls the cancer and is tolerated. Your oncologist may adjust the dose to 258 mg or 172 mg daily if you have liver problems or significant side effects.
The most common side effects in clinical trials were musculoskeletal pain, nausea, fatigue, vomiting, decreased appetite, joint pain, diarrhoea, headache, constipation and hot flushes. Laboratory changes often include increases in cholesterol, triglycerides, creatinine and liver enzymes. Most of these side effects are mild to moderate, appear in the first few weeks of treatment and improve with time or with supportive measures such as anti-nausea medicines, adequate hydration and dietary changes.
Yes. Orserdu is only approved for patients whose tumour has an activating ESR1 mutation, confirmed using a validated test — most often on a blood sample (liquid biopsy) measuring circulating tumour DNA, or on tumour tissue from a biopsy. Without confirmation of an ESR1 mutation, Orserdu is not expected to provide additional benefit over standard endocrine therapies such as fulvestrant or aromatase inhibitors.
No. Orserdu is contraindicated during pregnancy and breastfeeding because it can cause serious harm to the unborn or breastfeeding child. A pregnancy test should be performed before starting treatment in women of childbearing potential, who must use effective non-hormonal contraception during treatment and for at least one week after the last dose. Men with partners of childbearing potential should also use effective contraception during treatment and for at least one week after the last dose.
You should avoid strong and moderate CYP3A4 inducers such as rifampicin, carbamazepine, phenytoin and St John's Wort, which reduce elacestrant's effectiveness. You should also avoid strong and moderate CYP3A4 inhibitors such as ketoconazole, itraconazole, clarithromycin and grapefruit juice, which increase side-effect risk. Orserdu can also raise levels of drugs such as digoxin, dabigatran and rosuvastatin, so close monitoring is needed. Always review every prescription, over-the-counter medicine, vitamin and herbal product with your oncologist or pharmacist.
Orserdu tablets should be stored at room temperature below 30°C in the original blister pack and outer carton, away from moisture and direct sunlight. Keep the medicine out of the sight and reach of children. Do not use Orserdu after the expiry date printed on the carton and blister. Unused or expired tablets should be returned to the pharmacy for safe disposal and must not be thrown in household waste or flushed down the toilet.
References
- European Medicines Agency (EMA). Orserdu (elacestrant) — Summary of Product Characteristics. Available at: ema.europa.eu/en/medicines/human/EPAR/orserdu. Accessed January 2026.
- U.S. Food and Drug Administration (FDA). ORSERDU (elacestrant) — Prescribing Information. Approved January 27, 2023; updated 2025.
- Bidard FC, Kaklamani VG, Neven P, et al. Elacestrant (oral selective estrogen receptor degrader) versus standard endocrine therapy for estrogen receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer: results from the randomized phase III EMERALD trial. J Clin Oncol. 2022;40(28):3246-3256. doi:10.1200/JCO.22.00338
- Bardia A, Bidard FC, Neven P, et al. EMERALD phase 3 trial of elacestrant versus standard of care endocrine therapy in patients with ER+/HER2− advanced breast cancer: updated results by duration of prior CDK4/6 inhibitor in metastatic setting. Cancer Res. 2023;83(5 Suppl):GS3-01.
- Turner NC, Swift C, Kilburn L, et al. ESR1 mutations and overall survival on fulvestrant versus exemestane in advanced hormone receptor-positive breast cancer: a combined analysis of the phase III SoFEA and EFECT trials. Clin Cancer Res. 2020;26(19):5172-5177.
- Gennari A, André F, Barrios CH, et al. ESMO Clinical Practice Guideline for the diagnosis, staging and treatment of patients with metastatic breast cancer. Ann Oncol. 2021;32(12):1475-1495.
- National Comprehensive Cancer Network (NCCN). Clinical Practice Guidelines in Oncology: Breast Cancer. Version 2.2025.
- Brett JO, Spring LM, Bardia A, Wander SA. ESR1 mutation as an emerging clinical biomarker in metastatic hormone receptor-positive breast cancer. Breast Cancer Res. 2021;23(1):85.
- World Health Organization (WHO) Collaborating Centre for Drug Statistics Methodology. ATC/DDD Index 2025: Elacestrant, ATC code L02BA04.
- British National Formulary (BNF). Elacestrant monograph. Royal Pharmaceutical Society, London, 2025.
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