Atara Biotherapeutics, Inc. is a clinical-stage biopharmaceutical company. The Company is focused on developing therapies for patients with severe and life-threatening diseases. The Company operates through the business of developing and commercializing therapeutics segment. The Company is focused on developing allogeneic or third-party derived antigen-specific T-cells. T-cells are a type of white blood cell. The Company's product candidate, ATA129, is a third-party derived Epstein-Barr virus CTL for the treatment of Epstein-Barr virus (EBV). ATA188 is in development for the treatment of multiple sclerosis. ATA520, which is a third-party donor derived WT1-CTL, targets cancers expressing the antigen Wilms Tumor 1 (WT1). ATA520 is in Phase I clinical trials. The Company's T-cell product candidate, ATA230, which is a third-party derived cytomegalovirus-CTL (CMV-CTL), is in Phase II clinical trials for refractory CMV.