Biogen's (BIIB 0.49%) Alzheimer's disease drug Aduhelm has been embroiled in controversy for a while. Now, there are reports that the drug could have some potentially serious safety issues. In this Motley Fool Live video recorded on Sept. 29, 2021, Motley Fool contributors Keith Speights and Brian Orelli discuss whether or not Biogen's blockbuster hopes for Aduhelm could be doomed.

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Keith Speights: Biogen has encountered plenty of issues so far with the launch of its Alzheimer's disease drug, Aduhelm. Now, though, there are reports of some potentially serious safety issues with this drug.

What are the concerns here? Do you think that maybe Biogen's blockbuster hopes for Aduhelm could be in jeopardy?

Brian Orelli: Yeah. The reports were of ARIA, our A-R-I-A that's emulated related imaging abnormalities in the FDA's adverse event reporting system. This is a known issue with the drug on the side in the clinical trials. It's really a problem for any emulated targeting drug on basically you're breaking up the amyloid and then that causes brain issues that can result in nausea and tremor issues, and issues with the walking. It's definitely not a side effect that you want, and it's definitely a problem for patients.

But there's a couple of problems with the reporting system. You don't know if the drug is the actual cause of the side effect. Although in this case, you can image data and you know the patients have Alzheimer's disease then it's probably likely that that's the cause.

But you also don't know the denominator. You know how many reports or are in the FDA system, but you don't know how many total patients that's out of. That makes it difficult to know the likelihood that how frequent ARIA actually is in patients that are taking the drug.

Then reports can actually come from the clinical trial. Some of these reports are maybe like duplicative ones that we already knew about in the clinical trial. That makes things difficult.

I don't think this is really that important for the success of Aduhelm. I think that probably getting cumulative doctors that the drug works, it's probably more important than allaying their fears of potentially getting ARIA. It definitely adds to the downside of the benefit-risk profile.