Sorafenib and its tosylate salt: a multikinase inhibitor for treating cancer

Sorafenib, a drug that targets malignant cancer cells and cuts off the blood supply feeding the tumour, has been crystallized as the free base, 4-(4-{3-[4-chloro-3-(trifluoromethyl)phenyl]ureido}phenoxy)-N-methylpyridine-2-carboxamide, C21H16ClF3N4O3, (I), and as a tosylate salt, 4-(4-{3-[4-chloro-3-(trifluoromethyl)phenyl]ureido}phenoxy)-2-(N-methylcarbamoyl)pyridinium 4-methylbenzenesulfonate, C21H17ClF3N4O3 +center dot C7H7O3S-, (II). In both structures, the sorafenib molecule is in an extended conformation. The pyridine-2-carboxamide group exhibits a syn conformation of the N atoms in (I), whereas an almost anti orientation is present in (II). In both crystal structures, the two terminal groups, viz. pyridine-2-carboxamide and the trifluorophenyl ring, are oriented differently to the conformations found in enzyme-bound sorafenib. The sorafenib molecules in (I) are linked into zigzag chains by N-H...O hydrogen bonds, whereas in (II) the presence of the additional tosylate anion results in the formation of chains of fused hydrogen-bonded rings. This study reveals the variations in the solid-state conformation of the sorafenib molecule in different crystalline environments.