CTSB and neoplasm: The cathepsin B-overexpressed tumor cell activatable albumin-binding doxorubicin prodrug, Al-ProD, which consists of albumin-binding maleimide group, cathepsin B-cleavable peptide (NH2-FRRG-COOH; NH2-Phe-Arg-Arg-Gly-COOH), and doxorubicin (DOX), was designed for cancer-targeted therapy with minimal side effects.