Immunotherapy for Alzheimer’s Disease- The Alzheimer’s Disease Vaccine
Immunotherapy for Alzheimer's disease, commonly known as "the Alzheimer's Vaccine" has generated considerable excitement in both the Alzheimer's disease research community and among patients and caregivers. The basic logic of the approach is that it is possible to use the body's own immune system to fight off invading organisms and in doing so to treat disease.
Our immune systems are designed to fight off invading organisms such as bacteria and viruses. This is the primary way we cure illnesses ranging from the common cold to the flu. When the immune system detects a foreign substance, it mounts a defensive response that includes the production of antibodies that attack and eliminate the invader.
When scientists determined that a single molecule called beta-amyloid was responsible for the plaques and corresponding brain damage that is present in Alzheimer's disease, Elan pharmaceuticals set out on a research program to develop a vaccine that would attack and clear the beta amyloid from the brain. The rationale was that if the beta amyloid could be cleared, the progression of Alzheimer's disease could be slowed and perhaps ultimately stopped. Because this approach worked remarkably well in animal models, Elan began clinical trials in humans.
Unfortunately, this first trial was stopped because a small percentage (about 6%) of vaccinated individuals developed brain inflammation. Although the trial was stopped early, there was evidence that the vaccine was beneficial in many study participants. Some participants who later died of other causes were generous enough to donate their brain to research.
Alzheimer's disease patients who received the vaccine had significantly fewer beta amyloid plaques in their brains then patients who were not vaccinated. Additionally, a recent study has found that more than 4 years after their last vaccination, vaccinated patients were doing better in terms of their day-to-day activities than similar patients who did not receive the vaccine.
Because of these encouraging studies, there has been considerable effort in developing a safer version of the vaccine. These versions of the vaccine take a very different approach and in doing so may provide benefits without the inflammation seen in the initial studies.
The newer version of the vaccine is known as bapinuezumab. Bapinuezumab is a monoclonal antibody that is produced in the laboratory. Bapinuezumab binds to and clears beta amyloid peptide in the brain and in doing so hopefully facilitates memory and other cognitive processes.
A phase II clinical trial is currently being conducted at 20 sites across the United States. In this double blind trial patients have received either bapinuezumab or a placebo. Although the results of this trial will not be available until July, a small group of scientists from Elan and Wyeth have examined some of the results.
Based upon their evaluation, Elan and Wyeth have recently begun a large-scale phase III clinical trial in the US that will enroll approximately 2,000 patients. There are currently 70 sites across the country that are recruiting patients for this study. In general, patients should be between 50 and 88 years old, be in the mild to early moderate stage of the disease, have a caregiver who can attend clinic visits, and be able to tolerate magnetic resonance imaging (MRI) scans. Patients who participate in this study may remain on their Alzheimer's disease medications (Aricept, Exelon, Razadyne and/or Namenda). For more information regarding this study and for a list of sites currently recruiting patients, please visit ClinicalTrials.gov and search for "Bapineuzumab."