PSMA-Targeting Chimeras for Cell-Type-Specific Degradation of Surface Immune Checkpoint Protein PD-L1.

Lysosome-targeting chimera technology has been utilized to degrade proteins of interest via the endosome-lysosome pathway mediated by endogenous ligands that engage cell-surface transmembrane proteins. Despite their promising potential, current approaches remain limited by the tissue-specific expression of surface receptors required for endocytosis. Prostate-specific membrane antigen (PSMA) is highly and specifically expressed in prostate cancer, driving significant progress in PSMA-targeted therapies, particularly radioligand therapy and antibody-drug conjugates, through PSMA-mediated internalization. Leveraging this phenomenon, we developed PSMA-targeting chimeras (PATACs), a novel and readily accessible class of heterobispecific small molecules designed for membrane protein degradation. PATACs facilitate the cointernalization of a target protein of interest, directing it into the lysosomal degradation pathway. As a proof of concept, A4, a representative PATAC, induced rapid and dose-dependent degradation of programmed cell death ligand 1 (PD-L1), with significant reduction observed within 4 h at concentrations up to 100 nM. Consequently, this degradation potently enhanced T-cell-mediated killing of LNCaP cells in a coculture system. Molecular dynamics simulations revealed that PATAC A4, featuring a short and rigid linker, exhibits enhanced conformational stability within the PSMA-A4-PD-L1 ternary complexes. These findings reveal PATACs as a promising new class of bifunctional small-molecule modalities for the precise manipulation of membrane proteins and targeted therapy in prostate cancer.