What Happened in the Stock Market Today

Fitbit shares spiked 7% following a rare piece of encouraging news about the fitness device maker’s holiday sales trends. Its activity tracking software was the second most-popular download among free apps on Apple ‘s iTunes this past week, beating such heavyweights as Snapchat, YouTube, and Instagram.

Seattle Genetics Plunges After Drug Studies Halted on Deaths

Seattle Genetics Inc. plunged the most in five years after U.S. regulators halted several early-stage blood cancer studies following the deaths of four patients who suffered from liver damage. The Food and Drug Administration halted the trials testing Seattle Genetics’s acute myeloid leukemia, or AML, therapy, called SGN-CD33A.

J&J’s Decision to Walk Away Set Stage for Renewed Actelion Talks

Johnson & Johnson’s willingness to walk away from talks to acquire Swiss biotechnology company Actelion Ltd. for about $28 billion is the very thing that got the two sides back to the negotiating table. This week, amid rising pressure from shareholders, Actelion surprised investors and re-entered negotiations with J&J, which signaled a willingness to raise its offer if granted exclusivity, said people familiar with the matter.