Are you ready for retirement? Take this quiz to test your smarts and help secure your financial future.

Content starts here

This Brain Protein May Be Key to Treating Alzheimer’s

It's called tau and may be more closely tied to cognitive decline than amyloid

Marlene Cimons

Reviewed by

Orly Avitzur, M.D.

En español

Published July 28, 2026

An illustration of a woman grabbing hold of a tau tangle inside of a brain cell

Naomi Elliott

Key takeaways

The tau protein may drive symptoms more than amyloid, which can build up without causing noticeable decline.
Researchers are shifting focus to tau as a key treatment target after limited success with amyloid drugs.
New studies aim to prevent tau from forming tangles, ideally before symptoms begin.

Whenever Alzheimer’s is discussed, two problem proteins often come up in the conversation: amyloid and tau, the “hallmarks” of the disease.

Amyloid plaques usually get more attention than tau tangles. This may be due, in part, to two medications the Food and Drug Administration approved in recent years that target and remove amyloid plaques, those clumps that build up in the memory and higher thinking areas of the brain in people with Alzheimer’s. Development of effective drugs to remove tau tangles thus far has proved elusive, although scientists increasingly believe tau may be more important in the onset of Alzheimer’s symptoms.

More Ways to Benefit

View All

Related Benefit 1
Related Benefit 2
Related Benefit 3
Related Benefit 4
Related Benefit 5

“Researchers are highly focused on tau as the causative agent of [Alzheimer’s] disease,” says Roy Robert Parker, distinguished professor of biochemistry at the University of Colorado, Boulder.

Individuals can have a whole lot of amyloid build up over years but experience only mild Alzheimer’s symptoms — or none at all. Tau tangles, on the other hand, are believed to be largely responsible for the progressive memory loss and cognitive decline that occur in people with Alzheimer’s, according Dr. David Wolk, professor of neurology at the University of Pennsylvania Perelman School of Medicine and director of its Penn Alzheimer’s Disease Research Center, and other Alzheimer’s researchers.

There is an ongoing debate among Alzheimer’s disease specialists over which of the two abnormal proteins is more important in influencing Alzheimer’s, says Laura Nisenbaum, interim chief science officer at the Alzheimer’s Disease Drug Discovery Foundation.

Scientists believe that combination therapy — drugs that work on both tau and amyloid, as well as on other Alzheimer’s instigators, such as inflammation — ultimately will provide the most benefit for people with Alzheimer’s.

“The field has focused on amyloid therapy, with modest success, but tau is just as important,” she says. “The clumps of abnormal tau correlate more closely with cognitive decline. Amyloid sets the disease in motion, but tau is the engine that drives much of the damage.”

Tau tangles are related to neuron injury and dysfunction, Wolk says. Neurons, or nerve cells, transmit and receive information across the brain. “The amount of aberrant tau is closely linked to symptoms,” Wolk says. Researchers think finding drugs that can curb its misfolding and its spread “would likely slow or prevent development of brain injury and symptoms,” he adds.

What turns a good protein bad?

Tau is an important protein found naturally in the brain. It is key to keeping the internal structure of neurons stable, like the scaffolding that holds a building together.

Most Popular

But in Alzheimer’s, tau becomes chemically altered and begins to clump together, forming twisted tangles inside brain cells, disrupting the normal functioning of neurons.

“Tau essentially goes from being part of the solution to becoming part of the problem,” says Jeffrey Dage, senior research professor of neurology at Indiana University. “It abandons its day job and starts clogging up the machinery of the cell. Healthy tau is like oil in an engine. Diseased tau is more like sludge.”

In short, “every healthy brain contains tau,” Dage adds. “Alzheimer’s doesn’t create tau; it changes tau from a helpful protein into a harmful one.”

Scientists aren’t sure how amyloid behaves in a healthy brain before it begins forming clumps. “The normal function of [amyloid] is still not entirely clear,” Wolk says. “It seems to be involved in helping the integrity of synapses — which are how neurons communicate with each other — response to injury, and possibly immune function.”

Unlike tau, which clumps inside brain cells, amyloid plaques build up between them, which makes amyloid an easier drug target. Tau exists inside the neuron, making it harder for drugs to reach it. Tau is found in other cells but predominantly exists in the brain’s nerve cells.

AARP Brain Health Resource Center

Find explainers on dementia, stroke, Parkinson’s disease, head injuries and mental-health topics. Learn about healthy habits that support memory and mental skills.

Learn, take action, build healthy habits

Targeting tau

One promising new tau-targeted drug, BIIB08, or diranersen, still in clinical testing, works differently from past experimental tau-related therapies by trying to prevent tau tangles from forming by slowing tau production, rather than removing them after they develop.

In an 18-month clinical trial called Celia, the drug reduced tau levels in the brains and cerebrospinal fluid of people with early Alzheimer’s and slowed some cognitive decline. It did not, however, show a consistent relationship between doses and clinical benefit. The lowest dose had the biggest positive impact on symptoms. In fact, the findings raise important questions about the optimal dose of the drug and how future clinical trials should be designed, Nisenbaum says.

Biogen, is developing diranersen. The company presented its data in July at the Alzheimer’s Association International Conference in London and plans to continue clinical testing.

Scientists’ past attempts at tau-targeted therapy were unsuccessful. The initial experimental tau drugs were antibodies, proteins designed to latch onto tau and clear it from the brain. Several were tested in clinical trials, but all were discontinued after they failed to produce noticeable benefits for patients.

“Probably one of the reasons previous drugs failed was because they weren’t able to attack the right tau target,” Nisenbaum says. “They were focused on the tail of the protein.” More recent therapies target the core, or middle, of the protein, which they now know is responsible for the clumping.

The aim is not to get rid of tau entirely, since the brain still needs some normal tau, but to reach some sort of balance in how the drug acts. “The dose of these drugs is important,” Dage says. “We want to slow down new tau production enough to reduce tau tangles without reducing new tau so much that the neurons suffer any negative consequences.”

With that in mind, scientists will be working to develop tau-related drugs that can stop enough tau before the tangling — and symptoms — begin.

“Rather than cleaning up tau after the damage starts,” new treatments being studied “aim to turn down the production of new tau,” Dage says. “Instead of cleaning up the mess, these therapies try to reduce the amount of new tau entering the system in the first place.”

The key takeaways were created with the assistance of generative AI. An AARP editor reviewed and refined the content for accuracy and clarity.

Marlene Cimons is a Maryland-based writer who specializes in health, science and the environment.

Orly Avitzur, M.D., a former president of the American Academy of Neurology, is a practicing neurologist in Tarrytown, New York, and is working on a medical memoir, A Very Good Brain. She is a former medical director at Consumer Reports and a past editor in chief of Brain & Life magazine.

AARP Membership

Join AARP for only $15 per year with automatic renewal. Get instant access to members-only products and hundreds of benefits, a free second membership, and a subscription to AARP The Magazine.

Join