Atara Biotherapeutics, Inc. is a clinical-stage biopharmaceutical company. The Company is focused on developing therapeutics for serious unmet medical needs, with an initial focus on muscle wasting conditions and oncology. The Company’s research is based on the ability of activin, myostatin and other growth factors to change the course of disease progression. Atara Biotherapeutics’ is developing several independent programs: PINTA 745, STM 434 and ATA 842. The Company operates and manages its business as a reporting and operating segment, which is the business of developing and commercializing therapeutics. PINTA 745 is a peptibody, a protein construct made of a synthetic peptide that is fused to an antibody that binds to and blocks growth factors in the transforming growth factor beta pathway. Peptibodies are an established class of biologic therapies. STM 434 is a soluble receptor fused to part of an antibody that blocks the growth factor activin-A.