- A new blood-based test reflected Alzheimer's tau tangle pathology.
- The assay measured a new plasma tau species known as endogenously cleaved MTBR-tau243.
- The test distinguished various stages of Alzheimer's and separated it from non-Alzheimer's tauopathies.
A novel plasma-based assay was more strongly associated with
tau tangle pathology in Alzheimer's disease than other established blood
biomarkers, researchers said.
The assay measured a new plasma tau species known as endogenously
cleaved, microtubule-binding region containing residue 243
(MTBR-tau243), which specifically reflected tau tangle pathology,
reported Randall Bateman, MD, of Washington University School of
Medicine in St. Louis, and co-authors.
Plasma MTBR-tau243 was associated with tau PET binding (β=0.72, R2=0.56) and cognitive performance (β=0.60, R2=0.40), outperforming other markers like phosphorylated tau 217 (p-tau217) and p-tau205, Bateman and colleagues said in Nature Medicine.
The
assay was tested in three cohorts. It distinguished between early-
versus later-stage Alzheimer's disease and separated Alzheimer's disease
from non-Alzheimer's tauopathies.
The results suggested that plasma MTBR-tau243 could help estimate the
tauopathy load in Alzheimer's disease, improving diagnostic evaluations
of Alzheimer's in clinical practice and monitoring the efficacy of
tau-targeted therapies in clinical trials, the researchers noted.
"This blood test clearly identifies Alzheimer's tau tangles, which is
our best biomarker measure of Alzheimer's symptoms and dementia,"
Bateman said in a statement. The test also provides a good indication
about whether a patient's symptoms are due to Alzheimer's or another
disorder, he noted.
Insoluble tau aggregates within neurofibrillary tangles are a
defining feature of Alzheimer's disease and closely correlate with
clinical symptoms. In earlier research, Bateman and colleagues showed
that the MTBR-tau243 in cerebrospinal fluid (CSF) was a specific biomarker of tau aggregate pathology. The current study extended this analysis to plasma.
The researchers tested the assay in two pilot cohorts: a sample of 55 people in the Knight Alzheimer Disease Research Center(ADRC) at Washington University, and a group of 108 people from the Swedish BioFINDER-2 cohort. They validated the assay in a larger cohort of 739 people from the Swedish BioFINDER-2 study.
In both pilot cohorts, plasma MTBR-tau243 levels were significantly
increased in Alzheimer's disease dementia compared with mild cognitive
impairment or very mild Alzheimer's dementia. Plasma MTBR-tau243 levels
also were strongly correlated with CSF levels in the BioFINDER-2
(Spearman's ρ=0.92, P<0.001) and the Knight ADRC (Spearman's ρ=0.79, P<0.001) groups.
The validation cohort included people with Alzheimer's disease,
Parkinson's disease, Lewy body dementia, progressive supranuclear palsy
(PSP) or corticobasal syndrome (CBS), vascular dementia, frontotemporal
dementia (FTD), and others. Plasma MTBR-tau243 levels were not elevated
in non-Alzheimer's tauopathies; levels in people with PSP or CBS and FTD
were similar to those in controls.
Among
amyloid-positive participants, plasma MTBR-tau243 consistently
demonstrated a significantly higher area under the curve (AUC) compared
with p-tau217 and p-tau205 across nearly all tau PET regions. Plasma
p-tau217, however, outperformed MTBR-tau243 (AUC 0.97 vs 0.80) in predicting amyloid positivity across all participants.
"I believe we will use blood-based p-tau217 to determine whether an
individual has Alzheimer's disease, but MTBR-tau243 will be a highly
valuable complement in both clinical settings and research trials,"
noted co-author Oskar Hansson, MD, PhD, of Lund University in Sweden.
"When both of these biomarkers are positive, the likelihood that
Alzheimer's is the underlying cause of a person's cognitive symptoms
increases significantly, compared to when only p-tau217 is abnormal," he
said. "This distinction is crucial for selecting the most appropriate
treatment for each patient."
Study limitations include the relatively large volume of plasma (1.5
ml) needed for this first version of the MTBR-tau243 assay, Bateman and
co-authors said. Plasma MTBR-tau243 should be further validated in
larger populations, including people with higher frequencies of other
neurodegenerative or psychiatric diseases, medical comorbidities, and
those with a wider range of race and ethnicity.
-
Judy George
covers neurology and neuroscience news for MedPage Today, writing about
brain aging, Alzheimer’s, dementia, MS, rare diseases, epilepsy,
autism, headache, stroke, Parkinson’s, ALS, concussion, CTE, sleep,
pain, and more. Follow
Disclosures
This work was
supported by the Charles F. and Joanne Knight Alzheimer Disease Research
Center, the Tracy Family SILQ Center, the National Institutes of
Health, the Hope Center for Neurological Disorders, the Department of
Neurology at the Washington University School of Medicine, and a Zenith
award.
Bateman reported being an unpaid scientific advisory board
member of Roche and Biogen, and received research funding from Avid
Radiopharmaceuticals, Janssen, Roche or Genentech, Eli Lilly, Eisai,
Biogen, AbbVie, Bristol Myers Squibb, and Novartis.
Co-authors
reported relationships with nonprofit groups, pharmaceutical companies,
and other entities. Hansson also is a part-time remote employee of Eli
Lilly.
Primary Source
Nature Medicine
Source Reference: Horie
K, et al "Plasma MTBR-tau243 biomarker identifies tau tangle pathology
in Alzheimer's disease" Nat Med 2025; DOI: 10.1038/s41591-025-03617-7.