NRP1 and neoplasm: While inhibitors to confirm NRP-1 dependency were not used in the current study, the NRP-1-mediated tissue-penetrating pathway was clearly activated by iRGD-MMAF because it extensively spread in the extravascular tumor tissue and doubled the amount of co-injected dye entry into tumors, effects that are not achieved by traditional RGD peptides that lack an NRP-1-binding motif [9].