PDCD1 and metastatic melanoma: The fact that DTIC/Epacasome-2 markedly outperformed the co-administration of DTIC/Lipo-SM/Chol and Epacasome-2 on delaying tumour growth, preventing metastasis, and enhancing PD-1 blockade in late-stage metastatic melanoma corroborates the significance of the temporospatial controlled co-delivery approach (Figs. 5 and 6).