An orally bioavailable, highly selective and potent small molecule inhibitor of the delta and gamma isoforms of phosphoinositide-3 kinase (PI3K) with potential immunomodulating and antineoplastic activities. Upon administration, duvelisib prevents the activation of the PI3K delta/gamma-mediated signaling pathways which may lead to a reduction in cellular proliferation in PI3K delta/gamma-expressing tumor cells. Unlike other isoforms of PI3K, the delta and gamma isoforms are overexpressed primarily in hematologic malignancies and inflammatory and autoimmune diseases. By selectively targeting these PI3K isoforms, PI3K signaling in normal, non-neoplastic cells is minimally or not affected which would result in a more favorable side effect profile.