Provided herein is a genetically-modified micro-organ that provides a sustained delivery of a therapeutic peptide. The genetically-modified micro-organ may comprise a viral vector or expression cassette comprising at least two nucleic acid sequences encoding the therapeutic peptide separated by a cleavable linker. Further provided herein is a method of treating or preventing a disease or disorder in a human subject that can be treated or prevented by administration of a therapeutic peptide over a sustained time period using the genetically-modified micro-organ described herein.