A synthetic pentafluorophenylsulfonamide with potential antineoplastic activity. Batabulin sodium covalently binds to and selectively modifies the beta 1, beta 2, beta 3, and beta 4 isotypes of beta tubulin at a conserved cysteine residue, resulting in disruption of microtubule polymerization, collapse of the cytoskeleton, an increase in chromosomal ploidy, cell cycle arrest, and tumor cell apoptosis.