This invention relates to the field of therapeutics. Most specifically, the invention provides methods of generating conditionally expressing one or more proteins under the control of a gene expression modulation system in the presence of activating ligand and uses for therapeutic purposes in animals. The vector may be provided to treat or prevent disease.本發明關於治療劑之領域。最特別地,本發明提供條件性表現產製一或多種蛋白質之方法及在動物體內供治療目的之用途,該一或多種蛋白質之條件性表現係在活化配體存在下受基因表現調節系統之控制。該載體可被提供以治療或預防疾病。