Umbralisib R-enantiomer (TGR-1202 R-enantiomer) is a PI3Kδ inhibitor, which is the less active enantiomer of TGR-1202.In Vitro: Umbralisib R-enantiomer (TGR-1202 R-enantiomer) (Formula A) exhibits a 50% inhibitory concentration (IC50) with respect to the δ type PI3-kinase that is at least 20-fold lower than the inhibitor’s IC50 with respect to the rest of the other PI3K isoforms (i.e., a, β, and γ).