In the title compound, C20H19N3O4S, a novel tubulin ligand active against human cancer, the dihedral angle between the pyridine ring and the carbazole ring system is 42.87 (10)°. In the crystal, the mol-ecules are held together by N-H⋯O and C-H⋯O hydrogen bonds into layers, which are assembled into a three-dimensional network via π-π stacking inter-actions between inversion-related pyridine rings, with centroid-centroid distances of 3.5101 (12) Å.