$BIIB Barron's “The FDA’s decision will be sure to spark a big move in Biogen shares. Jefferies analyst Michael Yee wrote on May 12 that the stock could climb as much as 70% if the drug gets approved—and fall as much as 40% if it is rejected. And there will be ripple effects. Biogen shares make up 3.6% of the iShares Nasdaq Biotechnology exchange-traded fund (IBB).”