Idelalisib

How it works

It selectively inhibits the delta isoform of PI3K, interrupting B-cell receptor signalling pathways that drive malignant B-cell survival and proliferation.

Prescribing in practice

• Serious and sometimes fatal hepatotoxicity, colitis with diarrhoea, pneumonitis and infections can occur, requiring close monitoring and prompt treatment interruption.
• Pneumocystis jirovecii pneumonia prophylaxis and monitoring for cytomegalovirus reactivation are recommended during therapy.
• It is a CYP3A substrate and inhibitor, so review interacting medicines carefully before and during treatment.

Monitoring

Monitor liver function tests frequently, particularly early in treatment, alongside full blood count and surveillance for diarrhoea, respiratory symptoms and infection.

Counselling the patient

• Report diarrhoea, abdominal pain, breathlessness, cough, fever or yellowing of the skin without delay.
• Do not stop or alter the dose yourself; interruption is sometimes needed for safety.
• Keep taking any prescribed anti-infective prophylaxis.

Evidence & guidelines

Idelalisib is recommended by NICE within its licensed indications, supported by randomised controlled trials in chronic lymphocytic leukaemia and follicular lymphoma.