Write up in Bloomberg for those of us who are as clued in to Alzheimer's. Professor Cummings is also quoted in this article as "I am really at 50-50" as to whether FDA approves. But Cummings also says that the FDA is under "a lot of public pressure" to approve the drug.
https://www.bloomberg.com/news/articles/2019-12-04/it-s-make-or-break-for-alzheimer-s-drug-in-biogen-data-reveal?srnd=premium