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Experimental Alzheimer’s drug shows promise by targeting tau protein
The Alzheimer’s Association says the results provide hope but aren’t definitive
Updated:
key insights:
- Experimental drug diranersen is the first tau-targeting Alzheimer’s therapy to show Phase 2 evidence of reducing toxic tau tangles in the brain while slowing cognitive decline.
- Researchers say the findings could open a new front in Alzheimer’s treatment beyond today’s amyloid-targeting drugs, though larger studies are still needed.
- Biogen plans to advance the therapy into a Phase 3 trial after presenting the results at the Alzheimer’s Association International Conference in London.
An experimental Alzheimer’s drug that attacks one of the disease’s key proteins has shown encouraging results in a mid-stage clinical trial, raising hopes that a new treatment strategy could complement the amyloid-targeting drugs currently on the market.
The drug, diranersen (BIIB080), developed by Biogen, significantly reduced levels of the tau protein in the brains of people with early Alzheimer’s disease while also slowing cognitive decline, according to Phase 2 trial results presented this week at the Alzheimer’s Association International Conference (AAIC) in London.
The findings are significant because tau has long been viewed as a major driver of Alzheimer’s disease, but previous attempts to develop drugs targeting the protein have largely failed.
Unlike approved Alzheimer’s therapies such as Leqembi (lecanemab) and Kisunla (donanemab), which remove amyloid plaques from the brain, diranersen works by reducing production of the tau protein before it forms the tangles associated with the death of brain cells.
“This is the first Phase 2 clinical trial evidence that a drug treatment can remove toxic tau tangles from the brain in people living with early Alzheimer’s disease,” the Alzheimer’s Association said in a statement announcing the results.
Encouraging, but not definitive
The global CELIA study enrolled 416 people with early Alzheimer’s disease. Participants received one of several doses of diranersen or a placebo over 18 months.
Researchers reported that the drug reduced cerebrospinal fluid total tau by roughly 50% to 65% and also lowered tau deposits visible on PET brain scans. Patients receiving the therapy also experienced slower cognitive decline across several commonly used measures of memory and thinking ability.
One dose slowed decline on the Clinical Dementia Rating-Sum of Boxes scale by about 26% compared with placebo, while showing even larger improvements on some cognitive tests.
However, the results were not entirely straightforward. Higher doses did not consistently produce greater clinical benefits, and the study did not meet its primary endpoint, leaving questions about the optimal dosing strategy.
A different approach to Alzheimer’s
Researchers have increasingly concluded that Alzheimer’s is driven by multiple biological processes. Amyloid plaques tend to accumulate early in the disease, while tau tangles are believed to correlate more closely with memory loss and cognitive decline.
That has led scientists to pursue treatments aimed at both proteins, either separately or eventually in combination.
“People living with Alzheimer’s and their families deserve more treatment options, and the pace of progress is accelerating,” said Joanne Pike, DrPH, Alzheimer’s Association president and CEO.
“We look forward to seeing additional data and results when they are presented at the Alzheimer’s Association International Conference. Alzheimer’s is a complex disease, and people living with it deserve a research effort that pursues every promising lead.”
Experts cautioned that the new findings should be viewed as preliminary until confirmed in a larger Phase 3 study.
Biogen said it plans to begin that confirmatory trial after discussions with regulators. If successful, diranersen could become the first approved Alzheimer’s therapy to directly target tau, potentially expanding treatment options for the nearly 7 million Americans living with the disease.