Biogen stock plunged 30% after unfavorable FDA decision

Biogen (BIIB.US) shares fell 30% during today 'session after U.S. Food and Drug Administration advisory panel voted against approving company's experimental Alzheimer’s disease drug aducanumab last Friday. The FDA’s Peripheral and Central Nervous System Drugs Advisory Committee voted 8-1 against recommending approval of Biogen’s aducanumab. Two other members of the panel voted "undecided." On November 4th aducanumab received overall favorable initial review from the FDA which sparked a historic rally during which company's shares rose 44% to $355.63. However, on Friday the outside panel of experts questioned the drug's effectiveness, dimming prospects it will be approved by the agency. It turned out that the drug didn't perform particularly well in its late-stage clinical program. The advisory committee said the single successful test, along with an earlier-stage study, aren't sufficient to prove aducanumab's effectiveness. Biogen stock was halted on Friday during the meeting.