Pharmaceutical compositions of (E)-2,4,6-trimethoxystyryl-3-[(carboxymethyl)amino]-4- methoxybenzylsulphone and pharmaceutically acceptable salts thereof are described as well as methods of their use, and a dose regimen of (E)-2,4,6-trimethoxystyryl-3- [(carboxymethyl)amino]-4-methoxybenzylsulphone, sodium salt to reduce the incidence of urothelial toxicity.