Cited by 96Alzheimer's disease research and treatmentsDementia and Cognitive Impairment ResearchNeuroinflammation and Neurodegeneration Mechanisms

Current Status of Clinical Trials on Tau Immunotherapies

Open access
Ji, Changyi, Sigurdsson, Einar M.·2021·Drugs

Abstract

Tau immunotherapies have advanced from proof-of-concept studies to over a dozen clinical trials for Alzheimer's disease (AD) and other tauopathies. Mechanistic studies in animal and culture models have provided valuable insight into how these therapies may work but multiple pathways are likely involved. Different groups have emphasized the importance of intracellular vs extracellular antibody-mediated clearance of the tau protein and there is no consensus on which pool of tau should ideally be targeted. Likewise, various normal and disease-selective epitopes are being targeted, and the antibody isotypes either favor phagocytosis of the tau-antibody complex or are neutral in that aspect. Most of the clinical trials are in early stages, thus their efficacy is not yet known, but all have been without any major adverse effects and some have reported target engagement. A few have been discontinued. One in phase I, presumably because of a poor pharmacokinetic profile, and three in phase II for a lack of efficacy although this trial stage is not well powered for efficacy measures. In these phase II studies, trials with two antibodies in patients with progressive supranuclear palsy or other primary tauopathies were halted but are continuing in patients with AD, and one antibody trial was stopped in early-stage AD but is continuing in moderate AD. These three antibodies have been reported to only work extracellularly and tau is not increased in the cerebrospinal fluid of primary tauopathies, which may explain the failures of two of them. In the discontinued AD trial, there are some concerns about how much of extracellular tau contains the N-terminal epitope that is being targeted. In addition, extracellular tau is only a small part of total tau, compared to intracellular tau. Targeting only the former may not be sufficient for functional benefits. Given these outcomes, decision makers within the pharmaceutical companies who green light these trials should attempt to target tau not only extracellularly but also intracellularly to increase their chances of success. Hopefully, some of the ongoing trials will provide some functional benefits to the large number of patients with tauopathies.

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Research works printed but not linked: 13

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Authors
Ji, C., & Sigurdsson, E. M.
Affiliations
New York University (US)
Corresponding author
Sigurdsson, Einar M.
Venue
Drugs
Published
2021-06-08
Volume
81
Issue
10
Pages
1135-1152
ISSN
  • 0012-6667 (ISSN-L)
  • 1179-1950
OpenAlex
W3167046897
Cited by
96
References
137
Citations by year
2026: 6 · 2025: 19 · 2024: 31 · 2023: 25 · 2022: 10 · 2021: 5
FWCI
2.37
Type
journal article
Language
en
Open access
Locations
  • Drugs (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
Funders
National Institutes of Health (AG032611, NS077239, AG069475, NS120488)
Topics
  • Health Sciences › Medicine › Physiology › Alzheimer's disease research and treatments
  • Health Sciences › Medicine › Psychiatry and Mental health › Dementia and Cognitive Impairment Research
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
Keywords
tau immunotherapy, Alzheimer's disease, tauopathy, progressive supranuclear palsy, extracellular tau, tau antibodies, antibody epitopes, antibody isotypes, phagocytosis, target engagement, clinical trial discontinuation, cerebrospinal fluid tau, N-terminal epitope
MeSH terms
Alzheimer Disease, Animals, Clinical Trials as Topic, Humans, Immunotherapy, Vaccines, tau Proteins, Tauopathies

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