Prothena Corporation plc (NASDAQ:PRTA - Get Free Report) major shareholder William Scully bought 103,500 shares of the stock in a transaction dated Monday, September 28th. The shares were acquired at an average price of $8.60 per share, with a total value of $890,100.00. Following the completion of the acquisition, the insider directly owned 187,000 shares of the company's stock, valued at approximately $1,608,200. The trade was a 123.95% increa…