The present invention relates to crystalline polymorph forms of (S)-2-((2-((S)-4-(difluoromethyl)-2-oxooxazolidin-3-yl)-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepin-9-yl)amino)propanamide (GDC-0077), having the structure, Formula I:I (GDC-0077) or stereoisomers, geometric isomers, tautomers, and pharmaceutically acceptable salts thereof, and processes of preparing the polymorph forms.本發明係關於(S)-2-((2-((S)-4-(二氟甲基)-2-氧代㗁唑烷-3-基)-5,6-二氫苯并[f]咪唑并[1,2-d][1,4]氧氮呯-9-基)胺基)丙醯胺(GDC-0077)之結晶多晶型形式,GDC-0077具有式I之結構:I (GDC-0077) 或其立體異構體、幾何異構體、互變異構體及醫藥學上可接受之鹽及製備該等多晶型形式之方法。