For the people and families living with Lewy body dementia (LBD), the treatments available today share a common limit: they can ease symptoms, but none of them change the course of the underlying brain changes. Medications can help with memory, movement, sleep, or mood, yet the biological processes unfolding in the brain continue on their own timeline. A new clinical trial, now getting underway, sets out to test something the field has not yet been able to offer — a therapy aimed not at the symptoms of LBD, but at one of the underlying changes in the brain that may be driving it.
That change involves a protein called amyloid. Amyloid is best known for its role in Alzheimer’s disease, where it clumps together to form plaques between brain cells. But amyloid is far from exclusive to Alzheimer’s. It is also found in the brains of many people with LBD, alongside the protein most associated with the condition: alpha-synuclein, which gathers into the clusters known as Lewy bodies and is associated with the dysfunction and loss of brain cells.
When these two proteins appear together, the picture tends to be more difficult. Amyloid is present in an estimated 50 to 80 percent of people with dementia with Lewy bodies (DLB) and a smaller but still surprisingly high percent of people with Parkinson’s disease dementia (PDD). And when amyloid accompanies alpha-synuclein, research has linked the combination to an earlier onset of symptoms, a faster rate of decline, and a shorter lifespan than when either protein is present on its own. In other words, amyloid is not simply an incidental finding in LBD — for a large share of people living with the condition, it may be an active contributor to how the disease progresses. That makes it a logical thing to try to target.
The therapy being tested is donanemab, an antibody given as an intravenous infusion that attaches to amyloid and prompts the body to clear it away. Donanemab is not a newcomer: in 2024 it was approved by the U.S. Food and Drug Administration, under the name Kisunla, for the treatment of early Alzheimer’s disease, where it was shown to slow cognitive and functional decline. The question this new study asks is a different one — whether removing amyloid in people who have LBD, and who carry both amyloid and alpha-synuclein in their brains, might similarly slow the decline they experience.
The trial is called TRAILBLAZER-ALZ 7, and it is launching now. Sponsored by Eli Lilly, it is a Phase 2 study, meaning it is an early test designed to gauge whether the approach is safe and shows enough promise to justify larger trials down the road. About 350 participants between the ages of 55 and 85 will be enrolled and randomly assigned to receive either donanemab or a placebo, with neither the participants nor the study staff knowing who receives which. Each person takes part for about a year and a half.
Getting into the study involves careful confirmation that the right biology is present. Volunteers must have had gradual cognitive decline for at least six months and show at least one core clinical feature of dementia with Lewy bodies. Because the study aims to test the treatment near the beginning of cognitive decline, volunteers will need to meet certain minimum scores on cognitive testing to be accepted into the study. Beyond that, the trial uses biomarkers — biological signals that can be measured in blood or fluid — to confirm the underlying pathology. These include a blood test for a marker called P-tau217, along with tests of cerebrospinal fluid, the fluid that surrounds the brain and spinal cord, to confirm the presence of both amyloid and alpha-synuclein. The study’s main measure of progress is a standard rating scale called the Clinical Dementia Rating–Sum of Boxes, which tracks changes in memory, other cognitive domains, and the ability to manage daily life. The trial is opening at roughly 70 locations across the United States, Japan, South Korea, and Taiwan.
It is worth being clear about what a study like this can and cannot tell us yet. TRAILBLAZER-ALZ 7 is a beginning, not a conclusion. As a Phase 2 trial, it is built to answer whether the approach is safe and whether there is a signal worth pursuing — not to deliver a final verdict on whether donanemab helps people with LBD. Results are not expected until 2028. And because the trial enrolls only those with confirmed amyloid and alpha-synuclein together, its findings will speak to that specific group rather than to everyone living with LBD.
Still, for a community that has long waited for treatments aimed at the disease itself, a trial like this matters. For the people taking part and their care partners, the goal it reaches toward is concrete: more time with clearer thinking, steadier independence, and the daily routines that make up a life. Whether donanemab can help protect those things is exactly what the trial is designed to find out.
If you or someone you know is interested in learning more about research like this, the LBDA’s Lewy Trial Tracker can help. By signing up, you will be notified of research studies and clinical trials seeking participants from the LBD community.
