In this regard, early to moderate PD likely may represent the stages of disease most expected to respond to a gliptin, in the light of the demonstrated efficacy of the single GLP-1R incretin mimetics exenatide [29, 31, 32] and lixisenatide [79] in recent human clinical trials, and of exenatide in early-stage disease in a progressive PD preclinical model [80, 81]. The gene discussed is GLP1R; the disease is Parkinson disease.