High-Sensitivity Single Molecule Array Assays for Pathological Isoforms in Parkinson’s Disease

BACKGROUND: Clinical trials for neurodegenerative diseases are increasingly utilizing measurements of post-translational modifications (PTMs) and pathological isoforms as surrogate markers of target engagement and therapeutic efficacy. These isoforms, however, tend to exist at femtomolar concentrations, well below the detection limit of conventional immunoassays. Therefore, highly sensitive and well-validated assays for these isoforms are needed. METHODS: We developed a novel panel of single molecule array assays for pathological isoforms and PTMs implicated in the development and pathophysiology of Parkinson's disease. We validated this panel by measuring these analytes in the cerebrospinal fluid of a cross-sectional cohort of 100 patients with Parkinson's disease and 100 healthy controls. RESULTS: When comparing patients with Parkinson's disease to healthy controls, alpha synuclein, pSer129 alpha synuclein, DJ-1, and C-reactive protein were shown to be reduced in patients with Parkinson's disease while p396 tau and neurofilament light chain were shown to be increased. A random forest analysis produced an area under the curve of 0.70 for the panel. CONCLUSIONS: Measurement of post-translational modifications and pathological isoforms in patients with Parkinson's disease improved diagnostic accuracy above that of total protein measurements, demonstrating the potential utility of these assays for monitoring patients in clinical trials.