Osimertinib (Specialist drug)

How it works

It irreversibly and selectively inhibits sensitising EGFR mutations and the T790M resistance mutation while largely sparing wild-type EGFR, blocking downstream proliferative and survival signalling in tumour cells.

Prescribing in practice

• It can cause QT prolongation and, less commonly, cardiomyopathy with reduced left ventricular ejection fraction, so check ECG and electrolytes and assess cardiac function as advised, and stop for serious arrhythmia or heart failure.
• Interstitial lung disease/pneumonitis is a recognised and potentially fatal effect, so withhold and investigate any new or worsening respiratory symptoms.
• Rare but serious skin reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis have been reported.

Monitoring

Monitor ECG and electrolytes, periodically assess left ventricular function, and watch closely for respiratory symptoms and severe skin reactions throughout treatment.

Counselling the patient

• Report new breathlessness, cough or fever promptly.
• Tell us about palpitations, fainting or marked swelling.
• Seek advice urgently for any severe or blistering skin rash.

Evidence & guidelines

Efficacy is established by randomised trials showing superior progression-free and overall survival versus earlier EGFR inhibitors in EGFR-mutant lung cancer.