IDO1 and melanoma: developed PD‐1‐presenting nanovesicles derived from 293T cell membranes encapsulating small‐molecule IDO inhibitors called 1‐methyl‐tryptophan (1‐MT) (Figure 8A).[139] The cumulative effects of 1‐MT‐mediated IDO inhibition and PD‐1/PD‐L1 pathway blockage synergistically increased CD8+ T cell infiltration and a considerably improved T cell‐based immune response against melanoma.