Glutathione-dependent degradation of SMARCA2/4 for targeted lung cancer therapy with improved selectivity

SMARCA2 and SMARCA4 are the mutually exclusive catalytic subunits of the mammalian Switch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex, and have recently been considered as attractive synthetic lethal targets for PROTAC-based cancer therapy. However, the potential off-tissue toxicity towards normal tissues remains a concern. Here, we optimize a GSH-inducible SMARCA2/4-based PROTAC precursor with selective antitumor activity towards lung cancer cells and negligible cytotoxicity towards normal cells in both in vitro and in vivo studies. The precursor is not bioactive or cytotoxic, but preferentially responds to endogenous GSH in GSH-rich lung cancer cells, releasing active PROTAC to degrade SMARCA2/4 via PROTAC-mediated proteasome pathway. Subsequent xenograft model study reveals that selective SMARCA2/4 degradation in lung tumors triggers DNA damage and apoptosis, which significantly inhibits lung cancer cell proliferation without obvious adverse events towards normal tissues. This study exemplifies the targeted degradation of SMARCA2/4 in lung cancer cells by the GSH-responsive PROTAC precursor, highlighting its potential as an encouraging cancer therapeutic strategy.