As the first approved PI3K inhibitor, idelalisib was approved by the FDA in 2014 for the treatment of recurrent CLL in combination with retuximab, or as a single drug to cure recurrent follicular B cell non-Hodgkin’s lymphoma (FL) and recurrent small lymphocytic lymphoma (SLL). This evidence concerns the gene PIK3CD and B-cell chronic lymphocytic leukemia.