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An experimental Alzheimer’s drug called diranersen may slow early stages of the disease by targeting a different brain protein than current treatments, researchers announced Tuesday (July 14). Unlike existing drugs that focus on removing amyloid protein buildup, diranersen lowers levels of tau, a protein scientists believe plays a key role in Alzheimer’s symptoms.
According to new findings presented at the Alzheimer’s Association International Conference in London, diranersen reduced tau levels in the brain and showed signs of slowing memory and cognitive decline in people with mild cognitive impairment or mild Alzheimer’s. The research, involving about 400 participants, found that those who received the lowest dose of diranersen every six months experienced about a 26% reduction in cognitive decline compared to those who received a placebo. This improvement was similar to results seen with amyloid-targeting drugs like lecanemab and donanemab, which only modestly slow the progression of symptoms.
Diranersen works differently from amyloid drugs. It is an antisense oligonucleotide, a type of medicine that tells the body to make less tau protein, rather than clear it after it builds up. The drug is injected into the fluid around the spinal cord, which delivers it more directly to the brain, unlike current treatments given through the bloodstream.
The study did not meet its main goal of showing that higher doses produced greater benefits, but the lowest dose still led to meaningful results. Side effects included injection site pain and temporary confusion lasting about a week, but there were no reports of brain inflammation—a risk with some amyloid drugs.
Experts are hopeful but cautious. Dr. Cath Mummery, the study leader from University College London, explained, "If you lower tau production, you are lowering the amount of the abnormal tau that needs to be cleared by the microglia, by the clearance mechanism in the brain. And so you are enabling the normal clearance mechanism to have more capacity to clear the tau."
More research is planned. Biogen, the company behind diranersen, will conduct larger studies to confirm the benefits. Meanwhile, other approaches are also being explored, such as a possible tau vaccine and new ways to deliver drugs past the blood-brain barrier. The University of California, San Francisco, has launched a platform to test a range of anti-tau therapies.
Alzheimer's remains a challenging disease, affecting over seven million Americans. While current treatments can slow symptoms somewhat, researchers continue to search for new ways to treat and possibly prevent the disease.