The present invention relates to salt forms of the Fibroblast Growth Factor Receptors (FGFR) inhibitor 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, including methods of preparation thereof, where the compound is useful in the treatment of FGFR mediated diseases such as cancer.本發明係關於纖維母細胞生長因子受體(FGFR)抑制劑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-酮之鹽形式,包括其製備方法,其中該化合物適用於治療FGFR介導之疾病,諸如癌症。