Crystalline forms ofN-(2-(2-(dimethylamino)ethoxy)-4-methoxy-5-((4-(1-methyl-1H-indol-3-yl)pyrimidin-2-yl)amino)phenyl)acrylamide (1) and its pharmaceutically acceptable salts and compositions thereof useful for the treatment or prevention of diseases or medical conditions mediated through mutated forms of epidermal growth factor receptor (EGFR), such as various cancers, are disclosed.本發明揭示N-(2-(2-(二甲基胺基)乙氧基)-4-甲氧基-5-((4-(1-甲基-1H-吲哚-3-基)嘧啶-2-基)胺基)苯基)丙烯醯胺(1)之結晶型式及其醫藥學上可接受之鹽及其組合物,該等結晶型式及其醫藥學上可接受之鹽及其組合物適用於治療或預防經表皮生長因子受體(EGFR)之突變型式介導之疾病或醫學病況,諸如各種癌症。