Epacodostat, a hydroxyamidine analogue developed by Incyte Inc [26], was the first IDO1-selective inhibitor to complete Phase III evaluation in combination with Pembrolizumab, an anti-PD1 immune checkpoint blocker from Merck for the treatment of advanced malignant melanoma (ECHO-301/KEYNOTE-252). The gene discussed is IDO1; the disease is melanoma.