A targeted therapeutic agent comprising a compound of formula (I): B-L-D,wherein: B is a lowmolecular weight binding moiety for Carbonic Anhydrase IX (CAIX)； D is a drugmoiety； and Lis a linker group that undergoes cleavage in vivo for releasing said drugmoiety in an active form.The drug moiety is suitably a cytotoxic agent for targeted delivery to cancercells expressingCAIX. The binding moiety B suitably comprises a sulfonamidothiadiazole moiety.The bindingmoiety B may comprise one, two or more groups capable of binding to CAIX. Thelinker groupsuitably comprises a disulfide bond and/or a triazole group and/or a cleavablepeptide group.
