IDO1 and cancer: Based on our previous data describing the effect of epacadostat (hereafter EPA) in promoting the non-enzymatic function of IDO1 in both murine plasmacytoid DCs and in the SKOV-3 cell line (20, 23), we extended our screening to two further catalytic inhibitors of IDO1, namely, navoximod and linrodostat (hereafter NAV and LIN, respectively), in various human cancer cell lines endogenously expressing IDO1 protein.