Umbralisib (TGR-1202) is an orally available PI3K delta inhibitor, targeting the delta isoform with nanomolar potency and several fold selectivity over the alpha, beta, and gamma isoforms of PI3K. The delta isoform of PI3K is strongly expressed in cells of hematopoietic origin and is believed to be important in the proliferation and survival of B-cell lymphocytes. Inhibition of PI3K delta signaling with umbralisib has demonstrated robust activity in numerous pre-clinical models and primary cells from patients with hematologic malignancies. Umbralisib is currently in Phase 3 clinical development in combination with Ublituximab for patients with hematologic malignancies.