Imlunestrant: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
Imlunestrant: clinical details
Prescribing considerations
- Initiation and supervision should be by a clinician experienced in anticancer treatment.
- Confirm an activating ESR1 mutation in tumour or plasma using a CE-marked test for the intended purpose, or an alternative validated test when unavailable.
- Review CYP3A inhibitors and inducers and sensitive CYP2D6, P-glycoprotein and BCRP substrates.
- Exposure may increase with moderate or severe hepatic impairment and possibly severe renal impairment; data in dialysis and patients aged 75 years or older are limited.
- Verify pregnancy status where relevant and discuss fertility preservation when appropriate.
Contraindications and cautions
- Breastfeeding.
- Hypersensitivity to imlunestrant or any excipient.
Monitoring
- ALT and AST during treatment and when clinically indicated.
- Clinical toxicity, particularly gastrointestinal effects, fatigue, musculoskeletal symptoms and venous thromboembolism.
- Pregnancy status before treatment in patients who could become pregnant.
- Closer toxicity surveillance in severe renal impairment.
- Consider triglyceride measurements according to clinical context because increases are very common.
Clinical pharmacology
Imlunestrant is an oral antagonist and degrader of wild-type and mutant ER-alpha. It inhibits ER-dependent transcription and proliferation and is metabolised through sulfation, CYP3A4 oxidation and glucuronidation.
Formulation and product differences
- The selected product is a white, capsule-shaped film-coated oral tablet.
- Tablets must be swallowed whole; splitting, crushing and chewing have not been studied and may affect safety, efficacy or stability.
- The formulation is essentially sodium-free.
- No alternative selected UK formulation is represented.
Imlunestrant preparations and strengths
Tablet
Route: Oral
Strengths: 200 mg
Imlunestrant interactions
The oncology team should review prescription, non-prescription and herbal products before treatment. Important examples include:
Strong CYP3A inhibitors, including itraconazole
They can substantially increase imlunestrant exposure; concomitant use should generally be avoided or specialist-managed.
Strong CYP3A inducers, including carbamazepine, phenytoin, rifampicin and St John’s wort
They can reduce imlunestrant exposure and potentially reduce effectiveness; concomitant use should generally be avoided.
Digoxin and other sensitive P-glycoprotein substrates
Imlunestrant can increase their exposure, potentially increasing adverse effects.
Sources
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Record learning (opens in a new tab)Prepared and reviewed by the iatroX editorial team.