Idelalisib (Specialist drug)

How it works

It selectively inhibits the delta isoform of phosphoinositide 3-kinase (PI3Kδ), a signalling enzyme critical to malignant B-cell activation and survival.

Prescribing in practice

• Serious and potentially fatal hepatotoxicity, colitis, pneumonitis and infection (including opportunistic infection) are class warnings demanding close specialist supervision.
• Pneumocystis pneumonia prophylaxis and CMV surveillance are generally mandated throughout treatment and for a period afterwards.
• It is a CYP3A4 substrate and inhibitor, so interacting drugs must be reviewed against current prescribing references before co-prescription.

Monitoring

Monitor liver transaminases regularly, alongside full blood count and vigilance for diarrhoea, respiratory symptoms and infection, per the SPC.

Counselling the patient

• Report severe or persistent diarrhoea, breathlessness, fever or yellowing of the skin immediately.
• Do not stop or start other medicines without checking for interactions.
• Attend all scheduled blood tests.

Evidence & guidelines

Approval rests on randomised controlled trials in relapsed chronic lymphocytic leukaemia and indolent lymphoma showing improved response and progression-free survival.