The present disclosure relates to 3-(2,6-difluoro-3,5-dimethoxyphenyl)-1-ethyl-8-(morpholin-4-ylmethyl)-1,3,4,7-tetrahydro-2H-pyrrolo[3',2':5,6]pyrido[4,3-d]pyrimidin-2-one, solid forms and polymorphs thereof, methods of preparation thereof, and intermediates in the preparation thereof, which are useful in the treatment of the FGFR-associated or mediated diseases such as cancer.本發明係關於3-(2,6-二氟-3,5-二甲氧基苯基)-1-乙基-8-(嗎啉-4-基甲基)-1,3,4,7-四氫-2H-吡咯并[3',2':5,6]吡啶并[4,3-d]嘧啶-2-酮、其固體形式及多晶型物、其製備方法及其製備中之中間物,該等物質適用於治療FGFR相關或介導之疾病,諸如癌症。