For decades, Alzheimer’s disease has been one of the hardest brain disorders to treat, largely because it is usually diagnosed only after memory loss and confusion disrupt everyday life. By then, extensive damage has already occurred in the brain, leaving current treatments with limited impact.
New research from Northwestern University, however, suggests that an experimental drug may be able to slow or even stop Alzheimer’s much earlier—before symptoms appear.
Scientists say Alzheimer’s does not begin with forgetfulness. Instead, the disease starts quietly, sometimes decades in advance, with subtle but harmful changes inside brain cells. One of the earliest changes involves amyloid beta, a protein that can form toxic clusters.
While large amyloid plaques have long been associated with Alzheimer’s, researchers now believe smaller clusters, known as oligomers, are far more damaging. Until now, it was unclear which forms of these oligomers were the most dangerous.
In the new study, researchers identified a previously unknown and highly toxic subtype of amyloid beta oligomer that appears very early in the disease process. This form seems to trigger a chain reaction in the brain, leading to nerve cell dysfunction, chronic inflammation, and activation of immune cells that gradually damage brain tissue.
The team tested an experimental oral drug called NU-9 in mice genetically designed to develop Alzheimer’s disease. When given before any memory problems appeared, the drug significantly reduced levels of the newly identified toxic amyloid beta subtype and sharply limited the brain damage that usually follows.
NU-9 was originally developed years ago to target harmful protein buildup in neurological diseases. Earlier studies showed it was effective in animal models of ALS, helping clear toxic proteins and restore nerve cell health. Based on those results, the drug has already been approved to begin human trials for ALS.
More recent laboratory studies suggested NU-9 could also benefit Alzheimer’s disease by clearing toxic amyloid beta clusters from brain cells involved in learning and memory. The latest research expanded on this work by testing whether the drug could intervene at the earliest stage of the disease.
Mice were treated daily with NU-9 for two months before symptoms developed. Researchers observed a major reduction in brain inflammation, particularly involving astrocytes—support cells that normally protect neurons but can become harmful when overactivated.
The study found that NU-9 prevented astrocytes from entering this destructive state. It also reduced abnormal forms of another protein, TDP-43, which is commonly linked to brain cell damage and cognitive decline. These protective effects were seen across several brain regions.
During the research, scientists also discovered that the toxic amyloid beta subtype first appears inside stressed nerve cells and then spreads to nearby astrocytes. Once attached, it may spark widespread inflammation long before memory loss begins, effectively setting Alzheimer’s disease in motion.
NU-9 was especially effective at lowering this toxic protein, potentially stopping astrocytes from becoming harmful and slowing the cascade of brain degeneration.
Researchers compared the approach to treating high cholesterol to prevent heart disease—addressing a silent problem early to avoid severe outcomes later. They suggest that, in the future, NU-9 could be used in people identified as high-risk through blood tests or other early markers of Alzheimer’s.
Several such blood tests are currently under development. If successful, they could allow preventive treatments to begin years before symptoms arise.
The research team is now testing NU-9 in additional Alzheimer’s models that more closely resemble normal human aging. Longer-term studies are also planned to determine whether treated animals retain memory and brain health over time.
While the findings are based on animal studies and human trials are still needed, researchers say the work is significant because it targets Alzheimer’s at its earliest stage. Many previous clinical trials failed because treatment began after irreversible damage had already occurred.
By identifying a specific toxic protein and showing it can be reduced before symptoms emerge, the study offers a promising new direction for Alzheimer’s research and treatment.