Early steps toward an Alzheimer’s vaccine

Some encouraging Alzheimer’s news from Sweden: a vaccine called CAD106 appears to be safe and ramps up the body’s immune system against a protein likely involved in Alzheimer’s. The hope is that this vaccine will slow the progression of Alzheimer’s disease, and possibly even stop it.

The vaccine is designed to activate the body’s immune system against beta amyloid, a protein fragment that forms deposits called amyloid plaques between nerve cells in the brain. While it’s unclear if beta amyloid plaques cause Alzheimer’s or are a result of it, scientists do know that the plaques are an important biomarker of the disease. Some researchers believe that beta amyloid plaques interfere with communication between nerve cells or somehow inhibit processes needed to keep brain cells alive.

“Twenty-five years ago,” says Dr. Anthony L. Komaroff, professor of medicine at Harvard Medical School, “we knew very little about what caused Alzheimer’s disease and therefore how it might be prevented and treated. A lot of people were hopeless. We knew that we could see certain microscopic abnormalities in the brains of people with Alzheimer’s disease, called plaques and tangles. And we knew some of the chemicals inside the plaques and tangles. But we didn’t know if they caused the disease, and whether targeting them would help people with the disease.”

This vaccine work may help answer those questions.

Safety first

In the vaccine study, published online in Lancet Neurology, researchers from the Karolinska Institute gave 58 men and women with mild-to-moderate Alzheimer’s disease injections of CAD106 or a placebo and followed them for three years. Three-quarters of those who received CAD106 developed antibodies against beta amyloid protein. Virtually all of them—including those getting the placebo—reported one or more side effects, ranging from inflammation of the nose and throat to headache, muscle pain, and fatigue.

None, though, developed meningoencephalitis, an inflammation of brain tissue. That’s important because a trial of an earlier vaccine called AN1792 was abruptly stopped when 6% of those getting the vaccine developed meningoencephalitis. That vaccine apparently triggered a response among certain white blood cells that wound up attacking healthy brain tissue. CAD106, in comparison, targets only the beta amyloid proteins.

The next step in the development of CAD106 is a larger clinical trial to confirm the vaccine’s safety and to see if it is effective at slowing the relentless progression of Alzheimer’s disease.

“It’s much too early to say whether this particular vaccine will prove to be a valuable treatment in Alzheimer’s disease,” Dr. Komaroff says. “Nevertheless, in contrast to 25 years ago, today there is a lot of evidence that beta amyloid is one important cause of Alzheimer’s disease, and that targeting beta amyloid with drugs and vaccines may bring benefits. Because of biomedical research, today we have real reason for hope.”

Several other Alzheimer’s vaccines that target the beta amyloid protein are also being tested in clinical trials. Another effort moving forward includes an insulin-based nasal spray, which has shown promise in repairing damaged brain tissue involved in memory and cognition. The Obama administration’s National Alzheimer’s Plan, which was released last month, calls for $7.9 million in funding for this spray.