In what some experts
are hailing as a major breakthrough in the field of Alzheimer’s research, a new
investigation drug was found to reduce the disease’s hallmark plaques—
potentially slowing cognitive decline and preventing the disease.
Researchers
cautioned, however, that the study was an early test for safety, and the drug
needs to be tested further.
Alzheimer’s disease
is marked by amyloid plaques, which are believed to be the main culprit in the
most common form of dementia. Build-up of amyloid proteins leads to plaques,
which blocks cell-to-cell signaling. In the trial by Biogen, researchers tested
an antibody to see whether it can bind and break down amyloid protein, Time
reported.
“We are pretty
certain of the fact that the antibody reduces the amyloid plaques and in some
ways gets rid of the majority of it,” Alfred Sandrock, senior author of the paper
from Massachusetts-based Biogen, told Time.com. “That’s important because if we
really want to treat Alzheimer’s at even the very earliest stages, then we felt
it was important for our antibody to remove the plaque that’s already there.”
In the new yearlong
clinical trial, researchers gave 165 patients with mild to moderate Alzheimer’s
monthly infusions of either the antibody, aducanumab, or a placebo, and did a
series of brain scans. The people taking aducanumab showed a sharp decrease in
the amount of amyloid beta in their brains. The higher the dose of aducanumab
they received, the greater the amyloid clearance revealed in magnetic resonance
imaging (MRI) scans.
"After one
year, you can see no red on the image, meaning the amyloid has almost
completely disappeared," said Dr. Roger Nitsch, a co-author of the study
and the director of the Institute for Regenerative Medicine at the University
of Zurich. He is also a founder of the biopharmaceutical company Neuroimmune.
The findings, which
have been publicly presented before, are being published Wednesday for the
first time in a peer-reviewed journal, Nature.
“This is a
remarkable therapeutic achievement and a tremendous advance for the field,”
Robert Vassar, a neuroscientist at the Northwestern University Feinberg
School of Medicine in Chicago, Illinois, told Science.
Additionally,
participants who took the largest 10-mg dose showed less decline on one of two
memory tests, compared to those who had lower doses or the placebo, Science reported. Researchers are recruiting for
two separate 18-month-long phase III trials to see whether amyloid reduction
will result in improved brain function , Time reported. Many promising
Alzheimer’s drugs have failed in these larger groups, Science reported.
"We're
encouraged that, there appeared to be a slowing of cognitive decline at a
dose-dependent manner, and also a dose-dependent slowing in functional
decline," said study co-author Dr. Stephen Salloway, a neurologist at
Butler Hospital in Providence, Rhode Island.
However, 40 patients
dropped out of the trial, Science reported. Half did so because of adverse side
effects, such as small hemorrhages or brain swelling. Higher doses more
commonly led to the side effects. Individuals with a genetic predisposition to
developing Alzheimer’s were found to be at a higher risk for developing brain
swelling.
The larger question
is whether clearing amyloid beta will lead to dramatic improvements in
cognitive decline, Dr. Eric Reiman, a psychiatrist and researcher at Banner
Alzheimer's Institute, a research and patient care center in Phoenix, wrote in
an editorial accompanying the new study in the journal. Some researchers
believe beta amyloid is a byproduct of the destructive brain process, and not
the cause, noted Reiman, who was not involved in the new study.
There is no cure for
Alzheimer’s disease, which affects more than 5 million Americans, according to
the Alzheimer’s Association.
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