epacadostat + retifanlimab

**epacadostat + retifanlimab** is a combination investigational regimen consisting of epacadostat, a highly selective oral inhibitor of indoleamine 2,3-dioxygenase 1 (IDO1), and retifanlimab, a humanized monoclonal antibody against programmed cell death-1 (PD-1)[1][3]. Epacadostat inhibits the degradation of tryptophan into kynurenine by IDO1, thus reducing immunosuppression in the tumor microenvironment and potentially improving anti-tumor immune responses. Retifanlimab blocks the interaction of PD-1 with its ligands PD-L1 and PD-L2, thereby enhancing T-cell activity against cancer cells[2][4]. The combination is under investigation primarily in oncology (e.g., recurrent glioblastoma) to evaluate whether dual blockade of immunosuppressive pathways (IDO1 and PD-1) improves outcomes versus PD-1 inhibition alone[1][3].