Atara Biotherapeutics has filed papers with the SEC to raise up to $50 million in an IPO. The company plans to list on the NASDAQ under the symbol ATRA. Kleiner Perkins Caufield & Byers (18.6% pre-IPO stake), Domain Associates (13.2%), DAG Ventures (13.2%) and Baupost Group (11.8%) are all current stockholders in the company, which develops molecularly targeted therapeutics with an initial focus on muscle-wasting conditions and oncology. Each of its three independent programs are novel compounds designed to address underlying mechanisms of disease and disease states with few therapeutic options. Including a $52 million round from earlier this year, the company has raised at least $72 million in financing prior to its IPO.