Biogen hammered after slashing guidance

Biogen Inc. (NASDAQ:BIIB) sank $85.02 (22%) to $300.03, losing $20 billion in market cap Friday after it lowered its 2015 guidance for EPS and sales growth, primarily because the company expects sales of multiple sclerosis drug Tecfidera dimethyl fumarate to be slower than expected.

The news dragged down biotech indices on Friday. The BioCentury 100 slipped 303.19 (4%) to 7,799.27, the NASDAQ Biotechnology Index was down 165.77 (4%) to 3,956.25, and the NYSE Arca Biotech Index lost 151.11 (3%) to 4,221.90. ...