In the absence of a submission from the holder of the marketing authorisation, idelalisib (Zydelig®) cannot be endorsed for use within NHS Wales in combination with an anti-CD20 monoclonal antibody (ofatumumab) for the treatment of adult patients with chronic lymphocytic leukaemia; who have received at least one prior therapy, or as a first-line treatment in the presence of 17p deletion or TP53 mutation in patients unsuitable for chemo-immunotherapy.