Disclosed are salts of 3-{ [((2E)-2-{ 1-[5-(4-t-butylphenyl)-4-hydroxy-3-thienyl]ethylidene} hydrazino)carbonothioyl]amino} benzoic acid, wherein said salt is an organic amine salt or a salt with quaternary ammonium cation. Salts of particular importance include salts where the organic amine or quaternary ammonium salt is an organic amine or quaternary ammonium salt having a hydroxy group such as ethanolamine, tromethamine or choline. Further disclosed is a crystalline tromethamine salt of 3-{ [((2E)-2-{ 1-[5-(4-t-butylphenyl)-4-hydroxy-3-thienyl]ethylidene} hydrazino)carbonothioyl]amino} benzoic acid for use in medicine as a thrombopoietin receptor activator or a platelet increasing agent.
