Paul Scherrer Institute Mar 19 2026 Rendering a drug effective or ineffective in a flash at the appropriate location – this is the focus of research in photopharmacology. The goal is to develop drugs that can be switched on and off with light of a specific wavelength. Orally administered medications could then be selectively activated by irradiating only a specific part of the body with light; the medication would remain ineffective in the rest of the body – thus reducing side-effects. For