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
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.