At least 20 companies reported earnings last week. Questcor Pharmaceuticals Inc. (NASDAQ:QCOR) fell 21%, losing nearly $1 billion in market value, after posting 4Q13 revenues that missed the Street's estimate. In addition, Citron Research said the company's autoimmune drug H.P. Acthar Gel repository corticotropin injection faces "severe risk of being pulled off the market by FDA." Citron cites analysis by a contract laboratory that found the product contained little or none of the active pharmaceutical ingredient.

Medivation Inc. (NASDAQ: MDVN) fell 16%, losing $1 billion in market value, after providing 2014 U.S. net sales guidance for Xtandi enzalutamide of $500-$535M, below the analyst consensus estimate (see "Analyst Picks," A20). The cancer drug is partnered with Astellas Pharma Inc. (Tokyo:4503).