IDO1 and cancer: There are some phase I/ II studies that enrolled patients with breast cancer in different stages of the disease, for treatments with indoximod, an IDO inhibitor (IDO is expressed by a number of tumor types and correlates with poor prognosis), an anti-OX40 antibody (OX40 is a costimulatory molecule expressed after T cell activation that enhances T cell survival and anti-cancer effector function) and an anti-PD-L1 checkpoint inhibitor.