Yang et al. generated DOX prodrug nanoparticles (CAP-NPs) via conjugation of the cathepsin B-cleavable peptide with DOX that allowed the release of the DOX only in cancer cells over-expressing cathepsin B. Moreover, when compared with the treatment of conventional free DOX with anti-PD-L1 antibodies, the combinatorial therapy of CAP-NPs with the same immune-checkpoint inhibitor demonstrated a significantly higher rate of complete tumor regression (50%) than the latter. The gene discussed is CTSB; the disease is cancer.