IDO1 and melanoma: The early clinical studies of pembrolizumab in combination with low-dose ipilimumab (1 mg/kg), talimogene laherparepvec (T-VEC), or epacadpstat, a selective oral inhibitor of indoleamine 2,3-dioxygenase 1(IDO1), showed acceptable safety profiles and promising efficacy in patients with advanced melanoma [27–29].