An unusually detailed examination of an Alzheimer’s patient’s brain has revealed striking differences between regions where treatment successfully removed harmful amyloid plaques and areas where those plaques remained. The regions cleared of amyloid showed little or no buildup of tau tangles, another protein abnormality strongly associated with brain cell damage and declining memory. Nearby areas that still contained amyloid, however, showed much higher levels of tau and evidence of continued neurodegeneration.
The discovery offers rare evidence from a human brain that removing amyloid plaques may provide protection against other damaging processes involved in Alzheimer’s disease (AD). The results also suggest that clearing amyloid thoroughly, particularly early in the disease, could help limit tau accumulation and slow the progression of brain damage.
Researchers from the Perelman School of Medicine at the University of Pennsylvania presented the findings at the 2026 Alzheimer’s Association International Conference. The study was also published in JAMA.
“Seeing both disease patterns side-by-side in the same brain gave us a rare opportunity to understand how amyloid removal affects other proteins that contribute to Alzheimer’s disease,” said co-senior author David Wolk, MD, co-director of the Penn Memory Center and director of the Penn Alzheimer’s Disease Research Center. “The findings provide some of the clearest human evidence to date that anti-amyloid therapies may limit the accumulation of tau and slow the brain changes that lead to memory loss and cognitive decline.”
How Amyloid and Tau Contribute to Alzheimer’s Disease
Two proteins play major roles in the development of Alzheimer’s disease. Beta-amyloid collects outside nerve cells, forming sticky deposits known as plaques. Tau, meanwhile, accumulates inside neurons and forms abnormal tangles. Both are associated with the progressive damage to brain cells that contributes to memory problems, changes in personality, and difficulties with thinking.
Treatments designed to eliminate amyloid plaques have significantly changed how Alzheimer’s is managed in recent years. Aducanumab became the first drug of this type to receive accelerated approval from the FDA, although it is no longer sold. Since then, newer and more effective medications that target amyloid through a similar approach, donanemab (Kisunla) and lecanemab (Leqembi), have received full FDA approval.
Researchers have long believed that amyloid buildup helps create the conditions in which harmful tau tangles develop. What has been much harder to establish is whether eliminating amyloid can also limit tau accumulation in the human brain.
Direct evidence has been scarce because relatively few people who received amyloid-clearing drugs have undergone brain examinations after death.
A Rare Brain Examination Reveals a Striking Pattern
The researchers were able to investigate this question using brain tissue donated by a former Alzheimer’s clinical trial participant.
The man was in his fifties when he was diagnosed with mild cognitive impairment caused by Alzheimer’s disease. He subsequently joined a clinical trial testing aducanumab and received 30 doses of the medication over four and a half years.
He died approximately four years after his last dose, more than a decade after his first symptoms appeared. Before his death, he expressed a wish to donate his brain to scientific research. The tissue was provided to the Center for Neurodegenerative Disease Research in the Department of Pathology and Laboratory Medicine.
When specialists examined the donated brain, they discovered an unusual pattern in which neighboring regions showed dramatically different amounts of Alzheimer’s-related damage.
The raised ridges of the brain’s folded surface, known as gyri, had lost most of their amyloid plaques and contained very little accumulated tau. In contrast, the neighboring grooves between these ridges, called sulci, still contained considerable amyloid buildup. These regions also exhibited substantially more tau tangles, inflammation, and degeneration of brain tissue.
This patchwork distribution was consistent with scans taken while the patient was alive, which had already indicated that amyloid removal varied considerably across different parts of his brain.
“Many previous reports have shown either extensive amyloid clearance or limited clearance,” said co-senior author Edward B. Lee, MD, PhD, the John Q. Trojanowski, MD, PhD Professor for Neurodegenerative Disease Research in Pathology and Laboratory Medicine. “This case represented a unique ‘Goldilocks’ scenario in which some regions cleared amyloid and others did not. It allowed us to directly compare what happened next in neighboring brain regions and better understand the relationship between amyloid, tau, and neurodegeneration.”
Could Alzheimer’s Treatments Protect the Brain for Years?
The findings could have important implications for the latest generation of Alzheimer’s medications, which remove amyloid using mechanisms similar to the therapy received by this patient.
Although the investigation involved only one individual, the contrast between different brain regions suggests that substantial amyloid removal may influence other disease processes long after treatment has stopped.
The results also raise an important question about how the benefits of Alzheimer’s drugs are measured. Clinical trials commonly evaluate patients over approximately 18 months, but some protective effects might take considerably longer to become apparent.
However, the study cannot establish how much amyloid must be removed to achieve lasting protection or prove that plaque clearance was directly responsible for the differences in tau accumulation and brain damage.
Researchers now hope to understand why certain parts of the brain respond more effectively to amyloid-clearing treatments than others. Identifying and potentially strengthening the biological mechanisms responsible for plaque removal could lead to better therapies.
Another major question is whether beginning treatment before extensive tau tangles develop could substantially delay Alzheimer’s or even prevent the disease from emerging.
Why Earlier Alzheimer’s Treatment Could Matter
Because amyloid can accumulate silently in the brain for many years before memory problems begin, researchers are increasingly interested in treating people during the earliest stages of the disease, potentially before noticeable symptoms appear.
“Patients may accumulate amyloid for years before symptoms appear,” said first author Christopher A. Brown, MD, PhD, an assistant professor of Neurology. “This case suggests that removing amyloid early may help limit the changes that ultimately damage brain cells. Ongoing trials will help determine whether starting treatment before symptoms begin can provide even greater benefit.”
This research received support from the National Institutes of Health (P30-AG072979, RF1-AG069474, R01-AG056014, R01-AG055005, R01-AG072796, R01-AG065341, P01-AG084497).
Source: www.sciencedaily.com
