Aducanumab immunotherapy robustly reduces Aβ burden and neuritic phospho-tau in postmortem Alzheimer's brains
Background
The accumulation of amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFTs), composed of hyperphosphorylated tau protein, are hallmark pathologies of Alzheimer's disease (AD). Current standard-of-care treatments primarily address symptoms, but recent anti-amyloid monoclonal antibodies aim to modify disease progression by clearing Aβ. However, the long-term neuropathological impact of these therapies on other AD phenotypes, particularly tau pathology and glial responses, remains a critical gap in understanding their full therapeutic potential and limitations.
Study Design
Researchers conducted a neuropathological study comparing postmortem brain tissue from six aducanumab clinical trial participants with nine untreated AD patients. The aducanumab-treated group had extensive drug exposure, with death occurring between 7 weeks and 5 years after their last infusion. Control patients were matched for age, APOE genotype, and Braak neurofibrillary tangle stage. The medial temporal lobe was analyzed to assess Aβ burden, neuritic phospho-tau, neurofibrillary tangles (using PHF-1+ and AT8+ antibodies), and microglial and astroglial reactivity.
Results
Patients treated with aducanumab exhibited a robust and significant reduction in Aβ burden compared to untreated controls. This reduction was consistent with previous biomarker data, confirming aducanumab's potent ability to target and remove brain Aβ. A notable observation was the association of Aβ with non-arterial microvessels in treated patients, suggesting a redistribution within the neuropil. In parallel with fewer Aβ plaques, neuritic phospho-tau also decreased. However, the density of PHF-1+ and AT8+ neurofibrillary tangles remained unchanged relative to the average untreated AD donor. Measures of microglial and astroglial reactivity were also comparable between treated and untreated groups. Importantly, Aβ plaques increased in proportion to the length of time after the last dose, consistent with gradual redeposition post-treatment.
Aducanumab treatment led to a robust reduction in Aβ burden and a parallel decrease in neuritic phospho-tau, but did not alter established neurofibrillary tangles or glial reactivity.
Key Findings
- Aducanumab treatment led to a robust reduction in
Aβ burdenin postmortem brain tissue. - Aβ was associated with non-arterial microvessels in treated patients, suggesting redistribution.
- Neuritic
phospho-taudecreased in parallel with fewer Aβ plaques. - Density of
PHF-1+andAT8+neurofibrillary tangles remained unchanged. - Microglial and astroglial reactivity were comparable to untreated controls.
Why It Matters
This study provides crucial postmortem evidence confirming the efficacy of aducanumab in reducing Aβ plaques and, importantly, demonstrates a selective reduction in neuritic phospho-tau. For clinicians and future drug development, this implies that while Aβ-targeted therapies can alleviate plaque-associated dystrophy, they may not effectively address established neurofibrillary tangles, highlighting the need for combination therapies or earlier intervention. The finding that plaques redeposit post-treatment underscores the importance of continuous or sustained dosing strategies for anti-amyloid antibodies to maintain therapeutic benefits. This deepens our understanding of the long-term neuropathological impact, informing future AD treatment protocols and drug design.
aducanumab
alzheimers-disease
amyloid-beta
tau-pathology
neurodegeneration
immunotherapy