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Dr. Paul Aisen Q&A: Aducanumab for Alzheimer's.

In the wake of Biogen and Eisai's Oct. 22 announcement about plans to apply to the Food and Drug Administration next year for the regulatory approval of the investigational monoclonal antibody aducanumab as a treatment for Alzheimer's disease, we spoke with Paul Aisen, MD, the founding director of the Alzheimer's Therapy Research Institute at the University of Southern California, Los Angeles, for his views on the news. He has been a consultant for Biogen and is a member of the aducanumab steering committee.

Q: What was your first reaction when you heard about the plan to submit an application for aducanumab to the FDA?

A: My initial reaction is that this provides terrific support for the amyloid hypothesis, and is consistent with the early aducanumab studies showing significant reductions in brain amyloid with resulting clinical improvement.

My next thought was that these data are going to be very, very challenging to analyze because both of these trials were stopped early, and one was clearly negative. We really need to scrutinize the data, but even at this point I would say this strongly supports targeting amyloid. The scrutiny will begin in detail at the Clinical Trials in Alzheimer's Disease conference in December, when Biogen will likely release detailed data. A lot of people will analyze it, and I think that's great. It's beneficial to bring different perspectives.

We have had a terribly frustrating series of disappointments in the field. After the futility analysis of aducanumab and the multiple failures of BACE [beta-secretase] inhibitors, many were convinced we were barking up the wrong tree. I think these results, although complicated, should resurrect the enthusiasm for targeting amyloid.

Q: What is different about aducanumab from other antibodies tested--and rejected--in Alzheimer's drug development?

A: There are lots of antibodies that have been tested in clinical trials. They all differ in terms of their affinity for amyloid beta. Some target monomers of the protein. Some target dimers. Some target fibrils. Some tie up amyloid and some reduce it. Aducanumab directly attacks brain plaques, reducing the plaque load in the brain. It carries a liability of amyloid-related imaging abnormalities [ARIA], but it also allows us to assess the impact that removing plaques might have on downstream events, including biomarkers. Overall, these data show that aducanumab did remove brain plaques and that removing them had a beneficial effect on cognition and function, and also a favorable effect on downstream biomarkers.

But again, we must be cautious because this is a complex data set taken from a post hoc analysis of two different terminated trials.

Q: We see some statistically significant differences in cognitive and functional outcomes. What would that mean for patients on an everyday basis?

A: Well, everyone is different, so that's hard to say. A 25% slowing of functional decline on the Clinical Dementia Rating Scale sum of boxes (CDR-SB) might mean that, at the end of a year, there's not a significant change in memory, or that there's better social function. If both trials had been completed and if people had 18 months of high-dose aducanumab, the slowing of functional decline on the CDR-SB might in fact be greater than reported. Again, we're having to draw conclusions from interrupted trials.

Q: This suggestion you make of a potentially continuous slowing of decline--are you suggesting that aducanumab might slow decline to the point of stopping it altogether? If an elderly patient has little or no progression until death would that, in effect, be considered a "cure?"

A: I don't think it is possible to cure AD once the disease is clinically evident. These are studies of people with early AD, late mild cognitive impairment, and mild dementia. At that stage, there's already a loss of synapses that won't come back, and these studies don't suggest that aducanumab can cure that. But what if people took it earlier, when the brain is still functioning normally? Some of us have argued for many years that earlier intervention is the way to go. And since we can now identify people [with brain plaques] before they become symptomatic, there is the possibility that if we removed them, we could stop progression.

Q: Are there any plans to study aducanumab as a preventive agent?

A: A grant has been awarded for this, but it was put on hold after the futility analysis. I don't know when or if that will go forward.

(Editor's note: The National Institutes of Health previously awarded Banner Health a $32 million, 5-year grant to examine this. The 2-year prevention study of aducanumab is aimed at cognitively unimpaired 65to 80-year-old patients with PET-confirmed amyloid brain plaques. It was to be a multicenter, double-blind, placebo-controlled trial using Alzheimer's biomarker endpoints as primary outcomes, along with cognitive and clinical changes, safety, and tolerability. The study was put on hold after Biogen discontinued the aducanumab development program in March. Investigators are considering whether to resurrect plans considering the new data. The study is intended to be a public-private partnership, with additional unspecified funding from Biogen plus $10 million from philanthropic sources. It has three intended goals: to find an approved prevention therapy as early as 2023, ahead of the National Plan to Address Alzheimer's Disease's goal of an effective prevention strategy by 2025; to advance the use of surrogate biomarkers to rapidly test and support accelerated approval of prevention therapies in almost everyone at biomarker or genetic risk, even in earlier preclinical Alzheimer's stages when some treatments may have their greatest benefit; and to help make it possible to conduct prevention trials in at-risk persons even before they have extensive amyloid plaques, when some treatments may have their greatest benefit.)

Q: It seems like rolling this out to an enormous population of patients is going to be difficult, if not impossible. Are people really going to be able to commit to what could be a lifetime of monthly intravenous infusions of a medicine that could be expensive, as therapeutic antibodies generally are?

A: I would say, nothing about this disease is easy. It's devastating and horrible. And if someone is diagnosed at this stage, I would think that individual would embrace any opportunity to treat it. My hope is that we will be able to prescreen people with an effective blood test for amyloid that would be part of a regular testing protocol once they reach a certain age. Those with positive results would be referred for more testing, including amyloid brain imaging.

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Title Annotation:NEUROLOGY
Author:Sullivan, Michele G.
Publication:Clinical Psychiatry News
Article Type:Interview
Date:Dec 1, 2019
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