TauTrace™: An ultrasensitive immunoassay for neurodegenerative protein biomarkers

ABSTRACT Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by the formation of neurofibrillary tangles composed of hyperphosphorylated tau protein. Cerebrospinal fluid (CSF) and plasma levels of phosphorylated tau (pTau), are critical biomarkers used in molecular tests for diagnosing Alzheimer's Disease (AD), with Tau phosphorylated at the Thr217 site (pTau217) showing a strong correlation with the formation of AD-specific Tau tangles in the brain. However, current analytical methods lack the sensitivity required to detect and quantify the extremely low abundant disease-specific tau proteoforms present in biofluids at femtogram/milliliter (fg/ml) concentrations. This major unmet need hinders the development of personalized AD diagnostics and companion diagnostics for evaluating therapeutic response. To address this need, Adeptrix proposes to develop TauTrace™, a novel ultrasensitive immunoassay platform capable of quantifying distinct molecular forms of tau in CSF and plasma down to fg/ml levels. TauTrace™ is based on a sandwich immunoassay format using lanthanide-labeled antibodies and Secondary Ion Mass Spectrometry (SIMS) detection. This technology enables the detection of single ions, allowing for the quantification of distinct molecular forms of Tau in minimally invasive blood samples. A key innovation of TauTrace™ is its ability to independently probe multiple sites within a protein target by simultaneously applying several detection antibodies that recognize non-overlapping epitopes. This unique feature distinguishes it from other high sensitivity immunoassays and allows for the generation of relative abundance profiles of multiple Tau proteoforms, such as differentiating between full-length Tau and proteolytically cleaved forms. The liquid biopsy platform offers a simple, robust, and affordable solution for customers to perform in-house discovery and validation of low-abundance biomarkers, reducing reliance on specialized service providers. In this Phase I study, we will establish feasibility by developing lanthanide-tagged antibody probes against total tau (tTau) and pTau217, and validating their performance in quantifying these analytes in human CSF and plasma samples. Milestones for this project include achieving minimum signal-to-noise ratios for detecting tTau and pTau217 in CSF and plasma, as well as measuring the tTau/pTau217 ratio with a coefficient of variation of less than 15% in replicate assays. Successful completion will enable further development of TauTrace™ in a Phase II proposal into a comprehensive, affordable liquid biopsy platform for multiplexed quantification of low abundance tau proteoforms and other neurodegenerative biomarkers to support early AD diagnosis, disease monitoring, and therapeutic development.