SRHdeHSRHHdeHSRHHdeHProvided herein are (8 9) 5 fluoro 8 (4 fluorophenyl) 9 (1 methyl lH 1 2 4 triazol 5 yl) 8 9 dihydro 2 pyrido[4 3 2 ]phthalazin 3(7) one tosylate salt forms including crystalline forms and methods of their preparation. Pharmaceutical compositions comprising a (8 9) 5 fiuoro 8 (4 fluorophenyl) 9 (1 methyl 1 1 2 4 triazol 5 yl) 8 9 dihydro 2 pyrido[4 3 2 ]phthalazin 3(7) one tosylate salt are also provided as are methods of using (8 9) 5 fluoro 8 (4 fluorophenyl) 9 (1 methyl 1 1 2 4 triazol 5 yl) 8 9 dihydro 2 pyrido[4 3 2 ]phthalazin 3(7) one tosylate salt to treat a disease or condition such as a cancer.