The condition and the treatment(s)
Chronic lymphocytic leukaemia, which is also known as CLL, is a cancer of a type of white blood cell (called the B lymphocytes). The cancerous lymphocytes multiply in an uncontrolled way and stop other blood cells working properly.
Idelalisib blocks certain proteins inside cancer cells, helping to slow or stop the cancer growing for a time.
NHS Choices (www.nhs.uk) may be a good place to find out more.