I'm summarizing the findings of a new study by Jeff Sevigny and colleagues, that found significant improvement in the brains of patients suffering from Alzheimer's disease after a trial of therapy with a monoclonal antibody, called aducanumab.

First let me explain a little about Alzheimer's disease, which is the commonest cause of senile and presenile dementia. The disease results in a progressive degeneration and atrophy of the brain, which is accompanied by a build-up of a cloggy material known as amyloid plaques. For many years doctors have suspected that the amyloid plaques play a key role in the pathogenesis of the disease, but this has never been clearly proven. In large part this has been difficult to prove because no therapy has ever managed to clear the plagues and so test this hypothesis.

This new study, which was published this week in Nature, involved a randomized controlled trial of 165 patients, about equal numbers of men and women, in which four different treatment groups took four different doses of the new treatments by monthly intravenous infusions. The trial also included a control (placebo) group randomized so that neither the doctors nor the patients know who was in the control group and who in the treatment group. They were all treated for a period of a year. 125 completed the course of treatment. 

Treatment with aducanumab was found to reduce the amyloid plaques in a dose dependent manner. The main purpose of the trial was to see if the drug reduced the plaques and also to check for safety and tolerability of the therapy. 

Clinical assessments were said to be "exploratory" in that this was not the main area of study, but assessments also did appear to show dose-dependent slowing of the anticipated progression of the disease over the test period.

While this study needs to be extended to much larger numbers, and the next stage of study will no doubt focus on clinical outcomes as well as confirming the removal of the plaques, this study does appear to imply two related breakthroughs.

It showed slowing of the disease progression through medical therapy for the first time. It also appears to confirm that the plaques are a key element of the pathogenesis of the disease, so that treatment aimed at their elimination should help to treat the condition.

Another very important implication is that, where up to now, widespread screening to diagnose the disease at an early stage seemed somewhat fruitless if there was no treatment forthcoming for those folks diagnosed early. Now that a treatment is possible - and it is highly likely other groups will now start testing other related therapies - screening for pre-clinical stages of the disease really might have a very important purpose.

What if the disease was caught very early? Would this kind of therapy not only stop the progression but, perhaps, even allow the body's own defenses to make good or even cure the condition?

Sevigny J, et al. The antibody aducanumab reduces Aβ plaques in Alzheimer’s disease. Nature 537; doi: 10.1038/nature19323.