Alzheimer’s disease gradually affects memory and thinking, creating a need for treatments that can slow its progression and tools that reveal whether those treatments are working.

Although newer medications target abnormal protein buildup in the brain, monitoring individual responses remains challenging.

A study published in The Lancet Neurology in 2026 offers a potential way forward. Researchers at Washington University School of Medicine in St. Louis found that multiple proteins in the blood changed during treatment with lecanemab, an anti-amyloid medication. These changes could eventually help clinicians assess treatment responses and better understand how the disease progresses.

What Researchers Discovered

The study followed 197 patients with early Alzheimer’s symptoms and confirmed amyloid buildup who received lecanemab infusions every two weeks for up to two years. Researchers measured 130 proteins in plasma, the liquid component of blood, and examined how their levels changed during treatment.

The team identified significant changes in 34 proteins. Some changes were associated with Alzheimer’s-related processes, while others reflected immune activity. Researchers also compared the results with information from people without cognitive impairment or amyloid buildup and from individuals experiencing cognitive difficulties who were not receiving anti-amyloid treatment.

The findings are important because clinicians currently rely heavily on specialized brain imaging to assess amyloid buildup and its removal. Such scans can be expensive and difficult to access. Blood-based measurements could eventually provide a more convenient way to monitor certain biological responses, although additional validation is necessary.

How Blood Proteins Reflect Treatment Responses

Lecanemab works by targeting amyloid-beta, a protein that can accumulate into plaques in the brain. These deposits are a defining feature of Alzheimer’s disease and are associated with changes that contribute to cognitive decline. Among the proteins that changed during treatment was phosphorylated tau, commonly known as p-tau.

Abnormal tau accumulation is another important feature of Alzheimer’s disease. Researchers observed that several markers of Alzheimer’s-related pathology shifted toward levels found in cognitively healthy individuals, suggesting that treatment was influencing disease-associated biological processes.

However, changes in blood measurements do not automatically demonstrate improvements in memory or everyday functioning. Biomarkers provide information about biological activity, while cognitive assessments measure changes in thinking and memory. Both types of evidence are important when evaluating treatment effectiveness.

The researchers also detected increases in several proteins associated with inflammation and microglial activity. Microglia are immune cells that help maintain the brain and respond to harmful substances, including amyloid deposits.

Expert Insight

Suzanne Schindler, M.D., Ph.D., a professor of neurology at Washington University School of Medicine and a co-senior author of the research, highlighted the difficulty of assessing individual treatment responses. She stated: “When patients want to know how the anti-amyloid treatments are working, it's difficult to provide a clear answer.”

Potential Benefits and Research Limitations

The researchers identified two promising applications for blood-based biomarkers. One group of proteins changed alongside amyloid clearance, potentially helping clinicians assess how long treatment may be necessary. Another group was associated with changes in memory and thinking, suggesting possible value for estimating future cognitive outcomes.

These applications remain investigational. The study was conducted at a single clinic, meaning the findings must be replicated in other medical settings and patient populations before reliable clinical tests can be developed. Blood tests would also need to be evaluated for accuracy, consistency, and their ability to improve medical decisions. They are not yet a replacement for established assessments or a guarantee that a particular medication is working.

Although these findings do not yet establish a ready-to-use test, further validation could eventually help clinicians assess treatment responses and understand individual disease trajectories more effectively. The research represents a promising step toward more personalized Alzheimer’s care, while emphasizing the importance of rigorous testing before these biomarkers enter routine clinical practice.