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.

Grant Number: 1R43AG094422-01
NIH Institute/Center: NIH
Principal Investigator: Vladislav Bergo