Project Summary The common approaches in cancer treatment involve drugs that act on DNA or proteins involved in cell proliferation. Regrettably, such drugs are (a) not selective to tumor cells causing damage in normal cells, and (b) ineffective in killing nondividing tumor cells, which can cause tumor relapse after the initial remission, leading to therapy failure. In our search for a protein that can kill tumor cells regardless of theirs proliferating status, we noted that the Protein Complex of Secretory Vesicle I (COPI) is involved in retrograde transport of proteins in the ER-Golgi secretory pathway, endosome maturation, and autophagy homeostasis. Its depletion leads to abortive autophagy, ER stress, unfolded protein response (UPR), and apoptosis. Almost all of the COPI components are expressed at the same levels in both normal and tumor cells. However, the coatomer protein complex I subunit 2 (COPZ2) is drastically downregulated in the tumor cells. Interestingly, in normal cells, the inhibition of the coatomer protein complex subunit 1 (COPZ1, an isoform of COPZ2) does not affect COPI function. However, the silencing of COPZ1 and COPZ2 simultaneously led to the loss of COPI function and, consequently, cell death. Then, COPZ2 deficiency indicates tumor cells' dependency on COPZ1. Therefore, selective COPZ1 inhibition in COPZ2-deficient tumor cells can potentially overcome the therapy failure problem. We will design a promising lead compound to inhibit COPZ1 in COPZ2-deficient tumor cells, selectively killing tumor cells over healthy cells. Our first-generation synthesized COPZ1 inhibitors (based on virtual screening) showed good selectivity against PDAC. Our central objective is to develop the second-generation small- molecule-based COPZ1 inhibitors that can kill PDAC cells selectively over normal cells by merging molecular modeling, chemical Synthesis, cellular mechanistic studies, and animal experiments. Specifically, we will improve COPZ1 selectivity by conjugating small organic molecules to interact with a secondary binding site. We hypothesize that the tumor cell death induced by selective inhibition of COPZ1 could lead the proliferating and nondividing tumor cells to apoptosis but not normal cells.