Early Results On Alzheimer's Vaccine Trial In People With Down Syndrome Promising, Researchers Say
People with Down syndrome actually make up the world's largest population of individuals predisposed to getting Alzheimer's disease. Researchers say they offer unique opportunities for clinicians exploring effective treatments for Alzheimer’s that could benefit both the Down syndrome and the general populations.
It was announced this month early clinical results of an ongoing study of an anti-beta-amyloid (Abeta) therapeutic vaccine in people with Down syndrome. The vaccine is being tested for safety, tolerability and its ability to provoke an immune response, or immunogenicity, in adults with Down syndrome. The vaccine is designed to stimulate a patient’s immune system to produce antibodies that specifically target Abeta proteins to prevent beta amyloid plaque accumulation and to boost plaque clearance.
“This is the first vaccine targeting Abeta that has been tested in the Down syndrome population,” she said, adding that she believes studying the Down syndrome population is critical for developing successful treatments for everyone with Alzheimer’s.
Because their bodies produce extra amyloid, most people with Down syndrome develop problems with thinking and memory early on. “The reason we are using Down syndrome individuals is that they have very defined genetics,” Pfeifer said. “Basically since birth they have beta-amyloid, which leads to plaques in Alzheimer’s disease. By the time they are 20, they develop Alzheimer’s like symptoms. By the time they are 40, they all have such symptoms. At the age of 60, the probability is almost 100% that they will have Alzheimer’s disease.” (Beta-amyloid is a sticky compound or microscopic brain protein fragment that accumulates in the brain, disrupting communication between brain cells and eventually killing them.)
One of the challenges in Alzheimer’s research, Pfeifer said, is that the disease is typically diagnosed once symptoms are already clinically present. “For Alzheimer’s disease in people with Down syndrome, the disease mechanism and approximate timing of onset are known; readily detectable pathological changes occur prior to Alzheimer-like symptoms, enabling treatment prior to disease onset,” Pfeifer continued. “That’s why the Down syndrome population is so important, because it can be an entry point which allows us to test treatments in a more homogenous, genetically defined situation to potentially help people with Down syndrome and a much wider Alzheimer’s population.”
Pfeifer said studying Alzheimer-like symptoms in people with Down syndrome addresses many of the key dilemmas that hinder the discovery of new treatments for everyone, including:
- Uncertain mechanisms and timing of disease-induced brain changes.
- Difficulty offering treatment before disease onset, genetic and age-related variability.
- The risk of including subjects with other forms of age-related dementia.
“The new attention given to people with Down syndrome now impacting society is new,” Pfeifer said. “Now, a lot of people with Down syndrome reach 60 years and older. They are independent and have relationships and are working. It has been completely overlooked. Their specialized genetics may give us hope to develop therapies for the wider population.”