Chronic diseases, particularly malignancies and immune-mediated inflammatory diseases (IMIDs), are a challenging frontier for clinical diagnosis and treatment, as well as for biomedical research. Current treatment regimens are frequently insufficient and thus new treatment strategies are needed. Novel therapies for disabling such diseases should provide improvements with respect to safety, efficacy and cost. To fulfill these three key criteria, recent research efforts have focused on the development of 'smart drugs'. This review highlights some examples of the rapidly expanding possibilities that current biotechnology has to offer in the development of novel therapeutic strategies for complex diseases such as IMIDs. Special attention is given to advances in, and limitations of, controlled and targeted gene product application in inflammatory diseases.