$ATRA is one of biggest losers #stocks today. read more:

Atara Biotherapeutics, Inc. (symbol: ATRA) was one of the worst losers of
the trading day today (2016-01-04), losing -8.94%. The number of shares
that changed hands was 447,114, or about 1 times the average daily volume
in the stock.
The closing price was $24.05, amounting to a market cap of $688,580,000,
about -63.32% off the highest price in the last 12 months. The stock has
been trading at a range between $17.2 and $65.56.
ATRA is in the Biotechnology: Biological Products (No Diagnostic
Substances) industry, part of the Health Care sector. It first went public
in 2014.