In a new study from AXON Neuroscience, researchers found an experimental Alzheimer’s vaccine appears to safely clear abnormal tau protein from the brain, but it’s not yet clear whether the shot will be able to save brain function.
In Phase 2 clinical trial, the vaccine produced high levels of antibodies to target and attack free-floating tau proteins before they can form “tau tangles” that clog neurons and damage brain function.
Tau tangles, along with plaques formed by the protein amyloid-beta, serve as one of the main hallmarks of Alzheimer’s.
While amyloid influences the speed of Alzheimer’s progression, there is strong evidence that tau pathology relates to the underlying cause of the disease.
The team found the vaccine also proved safe during the two-year trial, in which eleven doses were administered to randomly chosen patients with mild dementia.
People who received the vaccine, known as AADvac1, experienced about the same number of side effects and adverse events as those who were given a placebo.
However, the vaccine did not produce any significant benefits when it came to thinking, reasoning and memory tests performed across the entire patient group—possibly because there were too few people with clinically diagnosed Alzheimer’s participating in the trial.
During analysis of the clinical trial data, the researchers realized that about a third of the participants had low levels of abnormal tau protein.
This makes them not very suitable for evaluating the effects of a treatment halting the progression of tau pathology.
The team says that the research team did see some improvement in standard brain function tests given to a smaller group of trial participants who had actually been diagnosed with Alzheimer’s.
In that group, the vaccine slowed brain decline by around 30% in two different clinical and functional tests.
The results of the analysis perfectly align with the tau hypothesis—simply put, if the patient is tau biomarker positive, then tau pathology is responsible for his/her cognitive decline, and halting tau pathology should slow or halt progression.
If the patient is negative for markers of tau pathology, then this patient’s impairment is mainly due to other pathologies, and treating tau pathology in this patient won’t be meaningful.
The team says there’s still hope for this approach to treating Alzheimer’s disease despite the somewhat mixed results from this trial.
The phase 3 study will really focus on enrolling individuals that have the right biomarkers to be able to look at not only the safety and tolerability but also the efficacy on cognition and function.
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The study is published in Nature Aging. One author of the study is Dr. Petr Novak.
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