Priming Cells with Modulators of Cellular Signaling Ensures Enhanced Selectivity of HSPG-Specific Protein-Drug Conjugate Delivery.

Protein-drug conjugates (PDCs) constitute a rapidly growing group of precise anticancer agents. Receptor-mediated endocytosis is a critical step in PDC action, which ensures the delivery of PDCs into the interior of cancer cells. Here, we report TriFHS-MMAE, the first multivalent PDC specifically targeting heparan sulfate proteoglycans (HSPGs) overexpressed by pancreatic cancer cells, which induces ultrafast and highly efficient aggregation-dependent endocytosis (ADE) of HSPGs. Using high-content screening with a near-kinome-wide library of inhibitors, we identified signaling pathways that govern ADE of HSPGs and discovered cascades that selectively operate in pancreatic cancer cells versus healthy cells. We show that priming cells with identified endocytic chemical modulators improves the targeting of the TriFHS-MMAE conjugate in vitro and in vivo. Overall, these findings provide insights into the interplay among signaling, endocytosis, and PDCs and support the development of specific therapies for pancreatic cancer.