Imlunestrant

Imlunestrant is a prescription medication indicated for the treatment of adults with estrogen receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-), estrogen receptor-1 (ESR1)-mutated advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy.

• Imlunestrant is available under the following different brand names: Inluriyo

Common side effects of Imlunestrant include:

• nausea
• fatigue
• musculoskeletal pain
• constipation
• diarrhea
• abdominal pain 
• decreased calcium levels
• neutropenia
• anemia
• thrombocytopenia
• increased alanine transaminase (ALT) and aspartate transaminase (AST)
• increased triglyceride levels
• increased cholesterol levels

Serious side effects of Imlunestrant include:

• pleural effusion 
• fatal adverse reactions including cardiac arrest, acute myocardial infarction, right ventricular failure, hypovolemic shock, and upper gastrointestinal hemorrhage
• hepatotoxicity
• fractured sacrum
• peripheral neuropathy
• interstitial lung disease

Rare side effects of Imlunestrant include:

• none 

Seek medical care or call 911 at once if you have the following serious side effects:

• Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, coordination loss, unsteady, very stiff muscles, high fever, profuse sweating, or tremors.
• Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.
• Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

Adult dosage

Tablet

• 200 mg

Breast Cancer

Adult dosage

• 400 mg orally daily on an empty stomach
• Continue until disease progression or unacceptable toxicity
• Pre/perimenopausal women and men: Take with gonadotropin-releasing hormone agonist (GnRH) according to current clinical practice standards

Dosage Considerations – Should be Given as Follows: 

• See “Dosages”

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

Drug interaction overview

• Substrate of CYP3A
• Inhibitor of P-gp and BCRP
• Strong CYP3A inhibitors
  • Avoid coadministration or modify dose
  • Avoid concomitant use with strong CYP3A inhibitors; if unavoidable, decrease Imlunestrant dose
• Strong CYP3A inducers
  • Avoid coadministration or modify dose
  • Avoid concomitant use with strong CYP3A inducers; if unavoidable, increase Imlunestrant dose
• Sensitive P-gp or BCRP substrates
  • Avoid concomitant use unless otherwise recommended in the Prescribing Information for P-gp or BCRP substrates, where minimal concentration changes may lead to serious adverse reactions
  • Imlunestrant inhibits both P-gp and BCRP, resulting in increased systemic exposure of P-gp and BCRP substrates, which may increase the risk of adverse reactions related to these substrates

Contraindications

• None

Effects of drug abuse

• None

Short-Term Effects

• See “What Are Side Effects Associated with Using Imlunestrant?”

Long-Term Effects

• See “What Are Side Effects Associated with Using Imlunestrant?”

Cautions

• Embryofetal toxicity
  • It can cause fetal harm when administered during pregnancy, based on findings in animals and their mechanism of action
  • Advise pregnant women and females of reproductive potential of potential fetal risk
  • Advise females of reproductive potential and male patients with female partners of reproductive potential to use effective contraception during treatment and for 1 week after the last dose

Pregnancy and Lactation

Based on findings in animals and their mechanism of action, Imlunestrant can cause fetal harm when administered during pregnancy

There are no available human data regarding use during pregnancy to inform of drug-associated risk

Verify pregnancy status in females of reproductive potential before starting treatment

Advise pregnant women and females of reproductive potential of potential fetal risk

Contraception

• Females
  • Advise females of reproductive potential to use effective contraception during treatment and for 1 week after the last dose
• Males
  • Advise male patients with female partners of reproductive potential to use effective contraception during treatment and for 1 week after the last dose

Infertility

Based on findings in animals, it may impair fertility in females and males of reproductive potential

Findings in animals were reversible

Lactation

• There are no data on the presence of imlunestrant or its metabolites in human milk, its effects on breastfed children, or on milk production
• Because of the potential for serious adverse reactions in breastfed children, advise breastfeeding women not to breastfeed during treatment and for 1 week after the last dose