Atara Biotherapeutics, Inc. (NASDAQ:ATRA – Get Rating) was the recipient of a significant decrease in short interest in May. As of May 15th, there was short interest totalling 14,180,000 shares, a decrease of 20.3% from the April 30th total of 17,790,000 shares. Based on an average daily trading volume, of 1,420,000 shares, the short-interest ratio […]