A composition comprising: a stably integrating delivery vector; a modified mammalian thymidylate kinase (tmpk) activator polynucleotide wherein the modified mammalian tmpk polynucleotide encodes a modified mammalian tmpk polypeptide that increases phosphorylation of a prodrug relative to phosphorylation of the prodrug by wild-type mammalian tmpk polypeptide to a drug; and/or a targeting polynucleotide encoding a cell surface polypeptide that selectively binds a toxic binding agent. The disclosure also relates to use of these compositions in methods of treatment of diseases such as Fabry disease.