C5 and neoplasm: A previous study reported a GRP78‐targeting Nb with an affinity of only 2.1 × 10−7 M; however, it lacked binding identification for murine GRP78 and in vivo data.[37] In contrast, our identified Nb C5 demonstrated a higher affinity (9.2 × 10−8 M) and exhibited excellent tumor‐targeting efficacy in both cellular and animal models.