Crystalline (8

1. A crystalline form of (8S,9R)-5-fluoro-8-(4-fluorophenyl)-9-(1-methyl-1H-1,2,4-triazol-5-yl)-8,9-dihydro-2H-pyrido[4,3,2-de]phthalazin-3(7H)-one tosylate salt, where the crystalline form exhibits at least one of:

a solid state 13 C NMR spectrum with peaks at 143.2, 136.0, 131.8, 123.9, 112.2, 105.2, and 100.3 ppm±0.2 ppm;

a differential scanning calorimetry thermogram having an endotherm with a maximum at between about 320° C. and about 335° C.;

a thermogravimetric analysis thermogram indicative of an unsolvated material;

a dynamic vapor sorption isotherm plot which does not exhibit a significant weight change from 0 to 95% relative humidity;

an X-ray powder diffraction pattern comprising characteristic peaks expressed in d-values (Å) of about 11.9, 5.9, 4.9, 4.4, 4.3, 3.9, and 3.7; and

an X-ray powder diffraction pattern comprising peaks at 2θ angle degrees±0.2 2θ angle degrees of 7.4, 15.1, 18.1, 20.1, 20.4, 22.6, and 24.0.

2. The crystalline form of the (8S,9R)-5-fluoro-8-(4-fluorophenyl)-9-(1-methyl-1H-1,2,4-triazol-5-yl)-8,9-dihydro-2H-pyrido[4,3,2-de]phthalazin-3(7H)-one tosylate salt of claim 1 , where the crystalline form has a purity of at least about 99.5%.

3. The crystalline form of the tosylate salt of claim 1 , where the crystalline form is substantially free of an amorphous form of (8S,9R)-5-fluoro-8-(4-fluorophenyl)-9-(1-methyl-1H-1,2,4-triazol-5-yl)-8,9-dihydro-2H-pyrido[4,3,2-de]phthalazin-3(7H)-one or a salt or solvate thereof.

4. A pharmaceutical composition comprising the crystalline form of the tosylate salt according to claim 1 and a pharmaceutically acceptable excipient.

5. The pharmaceutical composition according to claim 4 , where the composition is formulated for oral administration to a subject.