Sulfonamide derivatives

The present invention relates to a compound of the following Formula (1) or the pharmaceutically acceptable salts thereof, having low toxicity and a potent effect of inhibiting tubulin polymerization, and the use thereof as a pharmaceutical composition:(wherein R1 and R2 may be the same or different and each independently represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, a nitro group, a hydroxy group; each R3, R4, R5 and R6 represents a hydrogen atom; A represents any group of (1) 5-membered heterocyclic group (except triazoyl group) optionally substituted by a lower alkyl group or phenyl group whose ring members include at least 1 nitrogen atom and may include any atom(s) selected from the group consisting of nitrogen atom, oxygen atom, and sulfur atom, and (2) a 3 to 10-membered alicyclic group whose ring members include at least 1 nitrogen atom and may include any atom(s) selected from the group consisting of nitrogen atom, oxygen atom, and sulfur atom).