Its not a great drug. The trial results were iffy at best. The problem is that there's nothing out there to treat it. There's a class of drugs called acetylcholinesterase inhibitors (Aricept patch), and a class called NMDA receptor antagonists (Namenda). Both of these are short term fixes that don't get to the root of the plaque problem. In the end its a way to stave off the inevitable. The problem is that the biology of Alzheimer’s is poorly understood. In order to find a good treatment, the biology needs to be worked out better.
I don't blame Biogen per se. They're a good well run company. People are desperate for a treatment. The FDA will watch it pretty close. If it's shown there's not a benefit, they will pull it down the road. They haven't done that very often but I think there's a shift in the thinking. If they approve a drug that could be beneficial for these "unmet needs" but based on sketchy data, the path going forward will be to pull it if there's no benefit after its been on the market..
Pricings a tough one. A lot goes into it. One of the reasons drugs cost a lot in the US is because they are mandated to be cheap in other countries. There needs to be more balance. And as I've said before, what institutions charge pharma companies to run clinical trials is criminal. Patent law needs to change to. Starting a patent run time when the structure is published is wrong. The patent duration needs to run longer once its on the market. There wouldn't be the need to recoup investment in such a short timespan. There's no easy answer.