For over a century, doctors and scientists have accepted one unchanging truth: Alzheimer’s disease cannot be reversed. Once the brain deteriorates into dementia, there’s no coming back. That assumption just collapsed.
Researchers at Case Western Reserve University have done what generations of scientists thought impossible. They reversed advanced Alzheimer’s disease in mice. Not slowed it. Not stabilized it. Reversed it. Older mice with memory problems, in two different Alzheimer’s-like mouse models (one focused on amyloid plaques, one on tau tangles), regained normal performance on memory tests after treatment with an experimental compound called P7C3-A20.
The mice were elderly animals with clear brain pathology and memory loss. In one model, amyloid plaques were prominent. In the other, tau-related disease features dominated. Their brains healed anyway.
Treatments have focused on slowing decline or managing symptoms, never on turning back the clock. This new work, published in Cell Reports Medicine, upends that approach.
How Did Scientists Reverse Alzheimer’s Disease in Mice?
Researchers used two different mouse models that mimic human Alzheimer’s disease. The first, called 5xFAD mice, develops amyloid plaques similar to those in human patients. The second, PS19 mice, develops tau tangles, another hallmark of the disease. Both types develop memory problems and brain damage that look a lot like human Alzheimer’s.
Scientists divided mice into groups starting at either 2 months old (mid-stage disease) or 6 months old (advanced disease). The mid-stage group received daily injections of either P7C3-A20 or a placebo until 6 months old. The advanced-disease group received treatment until 12 months old. In a separate tau tangle model, 11-month-old mice received treatment for one month. Each treatment group included both male and female mice.
Mice with advanced Alzheimer’s that received P7C3-A20 performed as well on memory tests as healthy mice. In the Morris water maze, a standard test where mice must remember the location of a hidden platform, treated Alzheimer’s mice found the platform as quickly as normal mice. Untreated Alzheimer’s mice struggled. Similar improvements showed up in object recognition tests and other measures of thinking ability.
But the changes went far beyond behavior. Brain tissue analysis showed broad improvements across many Alzheimer’s-linked measures, including reduced plaque accumulation, tau-related changes, blood-brain barrier damage, and inflammation. Most remarkably, the brains began generating new neurons again, a process that normally shuts down in Alzheimer’s.
What Causes Alzheimer’s Disease? The NAD+ Connection
The key to this reversal lies in NAD+, a molecule that works as universal energy currency in cells. Every cell needs NAD+ to power repair processes, fight oxidative stress, and keep DNA intact. When NAD+ levels fall, cells can’t keep up with constant maintenance needs.
The research team discovered that Alzheimer’s severity tracks with disrupted NAD+ homeostasis in both mice and humans. When they examined human brain tissue, people who had died with Alzheimer’s showed disturbed NAD+ metabolism.
But some elderly people had Alzheimer’s-like changes in the brain at autopsy yet had never developed dementia while alive. In this study’s analysis, these individuals showed gene expression patterns suggesting preserved NAD+ homeostasis despite their brain pathology.
P7C3-A20 doesn’t deliver NAD+ directly. Instead, it helps cells restore NAD+ balance when they are under stress (similar to fixing a leaky bucket rather than just pouring more water in).
The treatment also normalized a blood marker tied to Alzheimer’s in the mice. This marker, p-tau217, is used in humans to help diagnose the disease.
Can Alzheimer’s Disease Be Reversed in Humans?
To identify which aspects of the mouse findings might translate to human patients, researchers compared protein changes in the treated mice with databases of human Alzheimer’s brain tissue. They found 46 proteins that changed the same way in both human and mouse Alzheimer’s brains. All 46 returned to normal with P7C3-A20 treatment.
These proteins affect how cells handle stress, produce energy, and manage inflammation. The finding suggests potential drug targets for treating human Alzheimer’s.
