Tau is the major microtubule associated protein of a mature neuron. It is hyperphosphorylated in the brain of dementia and neurodegenerative disease patients, and multiple phosphorylation sites of Tau are therapeutic targets in active clinical trials. To support clinical development of a program targeting pS413 Tau, we developed an assay to measure free pS413 Tau in cerebrospinal fluid (CSF) as an assessment of central therapeutic target engagement. Prior to this work, there was no published method to detect pS413 Tau due to its ultra-low abundance in CSF. We will present the development, optimization, and validation of an ultra-sensitive assay detecting human pS413 Tau in CSF. This assay measures both full-length Tau and all C-terminal fragments of Tau on the Meso Scale Discovery (MSD) S-plex platform. The assay sensitivity was determined to be 4.1fM. Because drug concentration in blood is much higher than that in CSF, we also validated a hemoglobin assay in CSF to assess blood contamination during CSF collection, enabling the exclusion of samples with sufficient blood contamination to compromise the assessment of central therapeutic target engagement.
Learning Objectives:
Upon completion, participant will be able to describe critical aspects to build an ultra-sensitive clinical biomarker assay.
Upon completion, participant will be able to describe key elements to optimize a clinical biomarker assay to improve assay sensitivity in authentic sample matrix.
Upon completion, participant will be able to describe how to assess blood contamination in CSF clinical biomarker deployment.
