Duvelisib is an FDA-approved PI3K γ/delta inhibitor for chronic lymphocytic leukemia (CLL) that has been shown to decrease MDSC induction of Arginase 1 (Arg1) and nitric oxide synthase 2 (NOS2) transcripts and enhance immunotherapy in preclinical models when given at low doses [71]. This evidence concerns the gene ARG1 and B-cell chronic lymphocytic leukemia.