Cambridge-based pharmaceutical company Biogen is moving ahead with a potentially groundbreaking new drug to treat Alzheimer’s disease. The drug, called aducanumab, had been scrapped earlier this year, but the company now says that a new analysis has given it the confidence to ask the FDA for approval.

Dr. Dennis Selkoe is the co-director for the Center for Neurologic Diseases at Brigham and Women’s Hospital and is a professor of neurological diseases at Harvard Medical School. He spoke with WGBH Radio’s Arun Rath about the drug. This transcript has been edited for clarity.

Arun Rath: So to set up our understanding of this, to simplify things, Alzheimer's is associated with a certain kind of protein that accumulates in the brain. And this drug, aducanumab, is intended to prevent the buildup of that protein?

Dennis Selkoe: Yes, it is actually intended to remove the protein once it's happened, but it could potentially prevent it if you started the drug early enough. But today's discussion is about a trial in people who already have the buildup and have clinical Alzheimer's disease. And so you're talking about removing the protein.

Rath: Is the promise of that to not only stop the progression of the disease, but maybe even step towards a cure?

Selkoe: In my opinion, neurologically speaking, scientifically speaking, it looks like it could be prevented if we start early enough. We don't have that evidence yet, although we have it in animal models.

Rath: Can you explain what happened with that trial? Because the last that we heard, it was going so badly that Biogen decided to abandon it.

Selkoe: So the explanation that Biogen has provided is that the reason things reversed themselves is because they have twice as many patients they've studied, and more of those additional patients happen to be at the highest dose that Biogen offered of the drug. And also, there was a greater representation of folks who had taken the drug for a longer period of time.

This is a very strange happenstance that I think has hardly ever happened before in pharmaceutical development. I think there's one other example where an analysis was done that suggested the drug was not working and one should stop the trial and then, some months later, it turned out there was evidence the drug worked. So this is a very rare situation in drug development, to my knowledge. But nonetheless, it's very good news, potentially, for our patients.

Rath: Picking up on that study that did show, based on the new information that we've heard, some positive results — how much promise does that show?

Selkoe: Right. So as someone who has been studying this disease for a long time now, more than three and a half decades, these are the most striking and compelling data that we have yet seen in terms of a disease-modifying treatment. There is no treatment that I can offer my patients that will slow down the cognitive decline and the symptoms of the disease.

And here, in one of the two studies, the analysis of the full data set so far shows that they had a lessening of decline in memory and cognitive functions, as well as a lessening of decline in activities in everyday living. And that latter point is very important for all of us — for the patients, for their families, and for the FDA, that has to ultimately decide if they're going to approve these results, because that's what really counts. Can patients do things better? And Biogen gave examples that patients could do, you know, fairly minor financial tasks better if they were on aducanumab than if they were on a placebo, particularly if they got the high dose. They needed to have the higher of the two doses that were offered.

They also could do things like perhaps a little work in the kitchen, or making a cup of coffee, or cleaning up the house a bit. So those common activities that we all engage in were more readily done by patients who were on the high dose of aducanumab than those who were on placebo in this double-blind controlled study.

Rath: Well, it sounds like there's the possibility of a drug that finally might attack the roots of this illness. That sounds just incredibly exciting.

Selkoe: It is really very exciting.