Mouse-tested Alzheimer's peptide also circulates in human blood

In a paper published in PNAS Nexus on 20 October 2026, Sergey A. Kozin and colleagues describe a discovery that began as a drug project. Their team had designed a short peptide, a chain of four amino acids called HAEE, to stop amyloid-beta plaques from forming in the brain. In mice, the results were promising. Then, while testing the molecule, the researchers found that an identical one was already circulating in human blood.

Amyloid-beta is a protein that clumps into plaques, and preventing those plaques has been proposed as a way to prevent Alzheimer's disease or to treat it in its early stages. The plaques are believed to precede the spread of tau, a second protein that becomes toxic in the brain. The team targeted a specific weak point: zinc ions, which are thought to be key to plaque formation. HAEE blocks the main zinc-binding site on single amyloid-beta molecules. The authors had, in effect, reverse-engineered a molecule that the body had already produced on its own.

The blood measurements are the part that changes the picture. HAEE levels track disease status, lower in people with cognitive impairment, while amyloid-beta levels are the same in people with Alzheimer's and in healthy people. This is why the authors describe HAEE as a possible biomarker, a measurable sign in the blood that could help diagnose the disease. They also suggest that a deficiency of HAEE may be a cause of Alzheimer's. That is their interpretation, and the study does not establish it on its own.

For patients and clinicians, the most immediate prospect is diagnostic. A blood marker would be measured from a sample rather than inferred from later symptoms, and the authors are exploring HAEE in that role as well as a possible treatment. Yet the study reports results in mice and blood levels across groups of people. It describes no treatment trial in patients and gives no date for any clinical use, so the path from this finding to a test in a clinic remains open.