Hide-and-seek molecular navigator targets tumor cell surface thiols by programmable disulfide exchange.

Metabolism dysregulation induces distinct thiol profiles between cancer and healthy cells, offering an attractive therapeutic target. However, systemically targeting cancer-specific thiols remains challenging due to the widespread presence of these groups in the physiological environment. Here, we design a molecular navigator (MONA) with spatiotemporally programmable thiol-reactivity to target the thiols on cancer cells upon intravenous injection. MONA operates through a bioresponsive "Hide-and-Seek" mechanism based on tunable disulfide exchange across biological compartments. In the "Hide" phase, MONA circulates stealthily through rapid conjugation with endogenous albumin via disulfide bonding. In the "Seek" phase, albumin facilitates MONA transcytosis into tumors, where elevated glutathione levels trigger disulfide exchange, releasing MONA to multivalently engage with thiols on cancer cells. When conjugated with a photosensitizer, MONA induces cancer cell membrane disruption upon light irradiation, enabling potent phototherapy. This approach leads to complete tumor regression and systemic abscopal effects in an immunosuppressive murine breast cancer model. These findings highlight MONA as a powerful strategy for precise thiol-targeted cancer therapy.