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

Prothena Corporation plc (symbol: PRTA) was one of the worst losers of the
trading day today (2015-10-05), losing -5.13%. The number of shares that
changed hands was 395,403, or about 1 times the average daily volume in the
stock.
The closing price was $47.0, amounting to a market cap of $1,470,000,000,
about -33.35% off the highest price in the last 12 months. The stock has
been trading at a range between $17.0 and $70.52.
PRTA is in the Major Pharmaceuticals industry, part of the Health Care
sector.