Abstract
The current selection of ligands for both proteins of interest (POI) and E3 ubiquitin ligase significantly restricts the scope of targeted protein degradation (TPD) technologies. This study introduces cell-penetrating peptide-induced chimera conjugates (cp-PCCs) targeting the DHHC3 enzyme involved in PD-L1 palmitoylation. This approach disrupts PD-L1's immunosuppressive function, enhancing anti-tumor immunity. We developed cp-PCCs to degrade DHHC3, directly linking DHHC3-mediated PD-L1 palmitoylation to PD-L1 stability on tumor cells. Our research utilized both in vitro assays and in vivo experiments in immune checkpoint blockade-resistant mouse models. We focused on a CRBN-based cp-PCC named PCC16, which demonstrated a DC50 of 102 nmol for DHHC3 degradation and significantly reduced PD-L1 levels. In resistant models, PCC16 not only robustly downregulated PD-L1 but also exhibited substantial anti-tumor activity in vivo without significant toxicity. This outperformed traditional inhibitors, showcasing the potential of cp-PCC technology to bypass current PROTAC limitations. Our findings suggest that cp-PCCs offer a promising method for targeting PD-L1 through DHHC3 inhibition and support their continued exploration as a versatile tool in cancer immunotherapy, especially for tumors resistant to standard treatments.