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, 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 theconference 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.