The invention provides compounds, compositions and methods to treat certain inflammatory conditions and/or oncology by administering a compound that inhibits PI3K isoforms, particularly the delta isoform. It further provides specific stereoisomers of a compound useful for these methods. In particular, the compound is an optically active atropisomer of 2-((6-amino-9H-purin-9-yl)methyl)-5-methyl-3-o-tolylquinazolin-4(3H)-one.