May 22, 2003
A vaccine has shown some promising results in slowing the progression of Alzheimer's disease, results of a small, preliminary follow-up study suggest. Although the findings are encouraging, doctors are still likely years away from having an effective vaccine against the disease. The findings should prompt continued research into the development of safe and effective immune-based therapies.
Medical researchers have long been interested in developing a vaccine to prevent or stop the progression of Alzheimer's disease. Vaccines currently being tested consist of tiny protein fragments that are designed to prime the immune system to attack beta amyloid, a toxic substance that is believed to build up in the brains of those with Alzheimer's disease. Beta amyloid is thought to form sticky patches of amyloid plaque that strangle and kill off brain cells, leading to the inexorable mental and cognitive decline of Alzheimer's.
Earlier Vaccine Trial Halted
Vaccine tests have been promising in animals, but the first trial of a vaccine in humans was halted last year when several participants developed life-threatening inflammation of the brain and spinal cord. Because of these serious side effects, administration of the vaccine, developed by the Elan Corporation and called AN-1792, was halted at the 28 medical centers where it was being tested. Doctors, however, continued to monitor the more than 300 men and women with mild to moderate Alzheimer's who were enrolled in the study.
This study looked at 28 study volunteers who were being treated by doctors at only one of those medical centers, the University of Zurich. Of these patients, 19 appeared to have responded to the vaccine--that is, their immune systems developed antibodies that were directed to attack the amyloid deposits. The remaining 9 patients did not have any antibodies against amyloid in their bloodstreams.
Doctors performed mental tests at the start of the study, and then again after eight months and one year. Those vaccine responders who had developed antibodies to amyloid showed a decline, on average, of only 1.4 points on the Mini-Mental State Exam (MMSE), a test doctors use to assess memory and thinking, compared to a decline of 6.3 points in those who did not develop an immune response. Most people with mild to moderate Alzheimer's would be expected to decline, on average, 3 or 4 points within a year.
In addition, vaccine responders also got a higher score when caregivers were asked to rate patient progress.
Although these initial results are encouraging, indicating that a vaccine approach may be helpful in the battle against Alzheimer's for at least some people, they were conducted among only a small group of patients. Overall outcomes may be very different when all 300 plus patients are evaluated.
In addition, it is important to remember that the vaccine being tested had life-threatening side effects in some people. Additional research is needed to find a safe and effective vaccine that may slow, or even halt, the progression of Alzheimer's disease.
The study appeared in the May 22, 2003 issue of the scientific journal Neuron.
By Toby Bilanow, Medical Writer for www.ALZinfo.org. The Alzheimer’s Information Site. Reviewed by Samuel E. Gandy, M.D., Ph.D., Chairman of the Scientific Advisory Board, Fisher Center for Alzheimer's Research Foundation.