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Alzheimer's Vaccine Looks Promising

Kate Traynor

A vaccine that destroys amyloid plaques similar to those seen in the brains of patients with Alzheimer's disease seems to be safe and effective in mice. Preliminary clinical trials show that the vaccine is also safe for humans, but its effectiveness is not yet known.

The vaccine studies were pioneered by Dublin, Ireland-based Elan Pharmaceuticals. According to Elan's Dale Schenk in a July 11 Webcast from World Alzheimer Conference 2000, in Washington, D.C., the vaccine protects mice and causes no known ill effects. Company-conducted safety studies using primates and other animals indicate also revealed no ill effects from the vaccine. 

04 March 2002 — Update

Elan Pharmaceuticals announced last week that the company has halted a clinical trial of its experimental Alzheimer’s vaccine, AN-1792. According to Elan, the decision was made because 15 study participants showed signs of central-nervous-system inflammation after receiving the treatment.

The study had involved patients with mild to moderate Alzheimer’s disease. Elan said in the announcement that the company will no longer pursue studies of AN-1792 in humans.

Five days after Schenk's presentation, President Clinton announced that the government's National Institute on Aging will allocate $50 million for new research focused primarily on developing a vaccine against Alzheimer's disease. 

In March, the United Kingdom's Medicines Control Agency approved Elan's plan to test the safety of the multidose vaccine on patients with mild to moderate Alzheimer's disease. Schenk also stated that Phase I trials of a single-dose regimen are underway in the United States. 

Although the company did not present its preliminary clinical findings at the conference, Schenk said there is "no question that the vaccine is well tolerated." 

Elan's initial study, reported in a 1999 issue of Nature, tested the vaccine in mice that had been transformed genetically to express large amounts of amyloid precursor protein and develop symptoms of Alzheimer's disease. After a year, the brains of mice immunized at six weeks of age had hardly any of the amyloid plaques seen in the mice that did not receive the vaccine. Vaccinating mice when 11 months old also reduced the formation of plaques and other neurological abnormalities. 

According to Schenk, the vaccine seems to cause the production of antibodies that recruit phagocytes to the site of plaque formation. The phagocytes engulf the amyloid plaques, which then disappear from the brain. Although the plaques may not actually cause Alzheimer's disease, researchers hope that destruction of the plaques can prevent Alzheimer's symptoms from developing. 

In April, Elan formed an alliance with American Home Products Corp., based in Madison, N.J., to develop and promote the Alzheimer's vaccine and other products.