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

Arena Pharmaceuticals, Inc. (symbol: ARNA) was one of the worst losers of
the trading day today (2015-09-25), losing -13.51%. The number of shares
that changed hands was 3,283,028, or about 1 times the average daily volume
in the stock.
The closing price was $2.24, amounting to a market cap of $542,620,000,
about -64.33% off the highest price in the last 12 months. The stock has
been trading at a range between $2.18 and $6.28.
ARNA is in the Major Pharmaceuticals industry, part of the Health Care
sector. It first went public in 2000.