Disclosed are salts and crystalline forms of N-(4-(2-amino-3-chloropyridin-4- yloxy)-3 -fluorophenyl)-4-ethoxy- 1 -(4-fluorophenyl)-2-oxo- 1,2-dihydropyridine-3- carboxamide and salts thereof. Also disclosed are at least one pharmaceutical composition comprising at least one crystalline form of N-(4-(2-amino-3-chloropyridin-4- yloxy)-3 -fluorophenyl)-4-ethoxy- 1 -(4-fluorophenyl)-2-oxo- 1,2-dihydropyridine-3- carboxamide, at least one method of using at least one crystalline form of N-(4-(2-amino- 3 -chloropyridin-4-yloxy)-3 -fluorophenyl)-4-ethoxy- 1 -(4-fluorophenyl)-2-oxo- 1,2- dihydropyridine-3 -carboxamide to treat cancer and/or other proliferative diseases, and processes to prepare crystalline forms of N-(4-(2-amino-3-chloropyridin-4-yloxy)-3- fluorophenyl)-4-ethoxy-1-(4-fluorophenyl)-2-oxo-1,2-dihydropyridine-3-carboxamide and salts thereof.