The clearest picture of Biogen's Alzheimer's drug is still fuzzy

Fresh data didn't do much to clear up questions around the most closely watched drug in all of biotech, an experimental treatment for what many consider the underlying cause of Alzheimer's disease.

Well before Thursday's presentation, there was skepticism. Two late-stage studies meant to show aducanumab can slow cognitive decline were halted prematurely because an interim peek at the data found chances for success slim.