In this study, we evaluated in vivo effects of the novel FAF1 inhibitor, KM-819, in a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD using [18F]FE-PE2I positron emission tomography (PET). The gene discussed is FAF1; the disease is Parkinson disease.