Elacestrant

Mechanism of action

◎Oestrogen receptor alpha (ERα), ligand-binding domainElacestrant

ⓘ The crystal shows elacestrant (code name RAD1901) in the ligand-binding pocket of human ERα.

Elacestrant binds the oestrogen receptor and stops oestrogen from binding, so oestrogen-dependent breast cancer cells stop growing. It is grouped with fulvestrant as a selective oestrogen receptor degrader, but unlike fulvestrant it is a non-steroidal tablet. Its benefit is clearest in tumours with ESR1 mutations, a common way that breast cancers escape aromatase inhibitors by keeping the receptor active with little oestrogen.

1. Elacestrant occupies the oestrogen receptor's ligand pocket
2. Oestrogen can no longer bind and switch genes on
3. Oestrogen-driven tumour growth stops, even with ESR1 mutations

Indications

• ER-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer in postmenopausal women or adult men, after at least one line of endocrine therapy. Breast cancer →

Adverse effects

Common

• Muscle and joint pain
• Nausea, vomiting, diarrhoea, constipation, indigestion
• Tiredness, decreased appetite, headache
• Hot flushes
• Raised cholesterol, triglycerides, liver enzymes and creatinine; low sodium

Contraindications

• No absolute contraindications in the label apart from hypersensitivity; see the warnings

Key interactions

St John's wort and other enzyme inducers

Lower elacestrant levels and may make it less effective.

Some other prescription medicines

Must not be combined or need dose changes, so the full medicine list is reviewed before starting.

What is monitored

• ESR1 mutation test before starting (tumour or blood test)
• Cholesterol and triglycerides
• Liver tests
• Pregnancy test before starting in women who could be pregnant

Administration and safety

• Oral tablet taken with food at about the same time each day.
• Swallowed whole: not split, chewed or crushed.
• A missed or vomited dose is not doubled; the next dose is taken at the usual time.

Pregnancy and breastfeeding

Avoid in pregnancy: effective contraception is used by women and by men with partners who could become pregnant, during treatment and for a short time after; breastfeeding is stopped.

Nursing care

• Check that an ESR1 mutation was confirmed before the first dose.
• Ask about St John's wort and review all medicines and supplements.
• Ask about liver disease or high cholesterol before starting, and follow the lipid and liver results.
• Teach to report yellow skin or eyes, dark urine or abdominal pain.

Pharmacokinetics

Absorption

Oral tablet, taken with food once a day.

Metabolism

Its levels are lowered by inducers such as St John's wort, and some medicines should not be combined with it.

Test yourself

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Connections

← Back to the class: Selective oestrogen receptor degraders (SERDs)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Elacestrant: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2023); FDA approves elacestrant for ER-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer (U.S. Food and Drug Administration, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Estrogen Receptor Alpha Ligand Binding Domain in Complex with RAD1901 (RCSB Protein Data Bank, 2022).

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Representative model, for educational purposes only.