Promising response rates in NSCLC and melanoma with pembrolizumab plus the IDO inhibitor epacadostat were recently reported, leading to exploration of this combination in a phase III trial in melanoma (NCT02752074) and a recently announced expansion of this phase III program into NSCLC, renal, bladder, and head and neck cancers [45]. The gene discussed is IDO1; the disease is non-small cell lung carcinoma.