CTSB and neoplasm: A cathepsin B‐responsive polymeric nanoparticle prodrug system is established for co‐delivery of paclitaxel (PTX) and capivasertib (CAP) to obtain BPGP@CAP, which selectively accumulates in the tumor tissue and releases PTX and CAP in response to overexpressed cathepsin B in lysosomes to exert a synergistic therapeutic effect to eradicate gastric cancer cells.