The DPP-4 resistant long-acting GLP-1 mimetic Exendin-4, approved for the treatment of T2DM, is hence being clinically assessed in neurological disorders [20–25] and has demonstrated promising efficacy in clinical studies when administered to PD patients by twice daily [26, 27] or once weekly injection [28–30]. The gene discussed is DPP4; the disease is Parkinson disease.