Photocaged chloroquine derivatives for the light-dependent inhibition of autophagy in cancer stem cells

Chloroquine (CQ) and hydroxychloroquine (HCQ) inhibit autophagy and have shown promise as adjuvant anticancer agents, particularly for targeting therapy-resistant cancer stem cells (CSCs). However, their clinical utility is limited by systemic toxicity and poor tumour selectivity. Here we report the design, synthesis, and photochemical evaluation of [7-(diethylamino)coumarin-4-yl]methyl (DEACM)-caged CQ and HCQ derivatives as visible-light-activated autophagy inhibitors. Selective caging of the aliphatic amine fully suppressed biological activity in the dark and enabled rapid, efficient release of the parent drugs upon illumination. The lead compound 1C displayed robust light-dependent cytotoxicity across multiple cancer cell lines and, upon photoactivation, recapitulated CQ’s effects on LC3-II accumulation. In CSC-enriched tumourspheres, illumination of 1C completely abolished spheroid formation, demonstrating precise spatiotemporal control of stemness suppression. Importantly, ex vivo and in vivo studies confirmed that visible light penetrates tumour tissue sufficiently to activate 1C and release CQ within the tumour. These findings establish the first proof of concept for light-controlled autophagy inhibition and provide a blueprint for spatiotemporally confined anticancer therapies based on photopharmacological modulation of CSCs.