Using a cytotoxicity-based phenotypic
screen of a highly diverse
library of 20,000 small-molecule compounds, we identified a quinolin-8-yl-nicotinamide,
QN519, as a promising lead. QN519 represents a novel scaffold with
drug-like properties, showing potent in vitro cytotoxicity
in a panel of 12 cancer cell lines. Subsequently, lead optimization
campaign generated compounds with IC50 values < 1 μM.
An optimized compound, QN523, shows significant in vivo efficacy in a pancreatic cancer xenograft model. QN523 treatment
significantly increased the expression of HSPA5, DDIT3, TRIB3, and
ATF3 genes, suggesting activation of the stress response pathway.
We also observed a significant increase in the expression of WIPI1,
HERPUD1, GABARAPL1, and MAP1LC3B, implicating autophagy as a major
mechanism of action. Due to the lack of effective treatments for pancreatic
cancer, discovery of novel agents such as the QN series of compounds
with unique mechanism of action has the potential to fulfill a clear
unmet medical need.