Provided herein is a modular polycistronic vector system, such as for the genetic reprogramming of cells to express one or more antigen receptors. The modular characteristic of the system allows for exchange of one or more cistrons in addition to one or more components within particular cistrons. In specific embodiments, the modularity of the system allows exchange of components of a chimeric antigen receptor, such as exchange of costimulatory domains, scFvs, hinges, signaling domains, and so forth.

Described herein are cell compositions comprising an active cell (e.g., an engineered active cell, e.g., an engineered RPE cell) or derivatives thereof, as well as compositions, pharmaceutical products, and implantable elements comprising an active cell, and methods of making and using the same. The cells and compositions may express a therapeutic agent useful for the treatment of a disease, disorder, or condition described herein.