As that last-linked blog post makes clear, I don’t find that evidence compelling, and most certainly not compelling enough to approve the drug as it stands. But with the way the FDA is behaving these days, God only knows what’s going to happen. People are investing on just that basis, although rarely stated in quite those words. But if you can look at the ruins of all the attempts to show efficacy with anti-amyloid antibody therapies and decide that the Biogen/Eisai data represent a real ray of hope, you have a sunnier disposition than I do.
I share the cynicism! Early drugs targeted amyloid plaques because it seemed like a good idea. But after so many failures, I can't think of any reason so much time and money is spent on a failed hypothesis other than hoping for a false positive. Because a false positive, even with very modest results, would result in a ridiculously profitable drug given the complete lack of Alzheimer's treatments we currently have.