Cheng et al. designed a therapeutic peptide-assembled nanoparticle that could accept dual stimuli sequentially and respond accordingly in the extracellular matrix of tumor cells, enabling the targeted delivery of DPPA-1 (a short-peptide inhibitor of PD-L1) and NLG919 (an IDO inhibitor) to the tumor site for enhanced immunotherapy [191]. Here, IDO1 is linked to neoplasm.