Osimertinib
Kinase inhibitors (targeted oncology)
Kinase inhibitors (targeted oncology)High alert
An error with this medicine can cause serious harm: double checks and protocols are used.
A third-generation, irreversible EGFR inhibitor active against the T790M resistance mutation; now a standard first-line drug for EGFR-mutant lung cancer.
Also called: AZD9291
Quick facts
- Group
- Kinase inhibitors (targeted oncology)
- Target
- EGFR tyrosine kinase domain
- Used for
- Non-small cell lung cancer
- Key effects
- Diarrhoea · Rash · Nail changes
- Monitor
- EGFR mutation testing · ECG and electrolytes
- ATC
- L01EB04
No doses: the clinician sets them by the current guideline.
Mechanism of action
The crystal shows osimertinib bound to the kinase domain of normal (wild-type) human EGFR; in patients its main targets are the mutant forms, including T790M.
Osimertinib binds irreversibly to the EGFR kinase. It potently inhibits the common activating mutations (exon 19 deletion, L858R) and also the T790M gatekeeper mutation that causes resistance to first- and second-generation inhibitors, while sparing normal EGFR more. That selectivity explains why rash and diarrhoea are milder than with the older drugs.
- Binds irreversibly to the EGFR kinase
- Blocks exon 19 deletion, L858R and T790M mutants
- Spares normal EGFR more than older drugs
- Milder rash and diarrhoea
Indications
- Non-small cell lung cancer with EGFR exon 19 deletion or L858R: first-line for metastatic disease, after surgery, after chemoradiation, and for T790M-positive disease after another EGFR inhibitor. Lung cancer →
Adverse effects
Common
- Diarrhoea
- Rash, dry skin, itching
- Nail changes
- Mouth sores
- Low blood counts
Contraindications
- No absolute contraindications; caution with long QT syndrome, heart failure and electrolyte disturbances
Key interactions
- Strong CYP3A4 inducers (rifampicin, St John's wort)
- Lower osimertinib levels; avoided.
- Other QT-prolonging drugs
- Add to QT prolongation.
What is monitored
- EGFR mutation testing (tissue or blood) before starting
- ECG and electrolytes in people at QT risk
- Ejection fraction in people with cardiac risk
- New cough or breathlessness
- Eye symptoms and blood counts
Administration and safety
- Oral; swallowed whole at about the same time each day.
- Check the name carefully: kinase inhibitors with similar «-tinib» names are not interchangeable.
- If the tablet cannot be swallowed, the patient information describes dispersing it in water and drinking it at once.
Pregnancy and breastfeeding
May harm the fetus; women and men with female partners use effective contraception during and after treatment; breastfeeding is avoided.
Nursing care
- Ask about palpitations, fainting, ankle swelling and breathlessness.
- Ask about eye pain, redness or light sensitivity.
- Teaching: report new cough or breathlessness at once; use contraception during treatment and for weeks to months after.
Pharmacokinetics
- Absorption
- Oral, with or without food.
- Metabolism
- Liver, mainly CYP3A.
- Elimination
- Mainly in the faeces, less in the urine.
- Half-life
- About two days.
Test yourself
Think of the answer, then tap the question to see it.
Which EGFR resistance mutation is covered by osimertinib but not by erlotinib?
T790M.
Why are rash and diarrhoea milder with osimertinib?
It inhibits normal (wild-type) EGFR less than older EGFR inhibitors.
Which two cardiac effects are monitored on osimertinib?
QTc prolongation and reduced left ventricular function.
Connections
← Back to the class: Kinase inhibitors (targeted oncology)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Osimertinib: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.