IDO1 and breast neoplasm: To determine whether the combination of PLG‐CA4 and PI3Kγ inhibitor interacts with other immune therapies, we used the checkpoint inhibitor of IDO (NLG919) in 4T1 breast tumor models (Figure6a).24 IDO is a crucial negative feedback protein in generating immunosuppressive molecules that inhibit the effector T cells and improve the regulatory T cells.[qv: 24c,25] Single agent of IDO inhibitor seemed to be an ineffective therapy for controlling the tumor progression with a decrease in the tumor burden to a lesser extent (Figure 6b).