Translesion synthesis (TLS) has emerged as a mechanism through which several forms of cancer develop acquired resistance to first‐line genotoxic chemotherapies by allowing replication to continue in the presence of damaged DNA. Small molecules that inhibit TLS hold promise as a novel class of anticancer agents that can serve to enhance the efficacy of these front‐line therapies. We previously used a structure‐based rational design approach to identify the phenazopyridine scaffold as an inhibitor of TLS that functions by disrupting the protein–protein interaction (PPI) between the C‐terminal domain of the TLS DNA polymerase Rev1 (Rev1‐CT) and the Rev1 interacting regions (RIR) of other TLS DNA polymerases. To continue the identification of small molecules that disrupt the Rev1‐CT/RIR PPI, we generated a pharmacophore model based on the phenazopyridine scaffold and used it in a structure‐based virtual screen. In vitro analysis of promising hits identified several new chemotypes with the ability to disrupt this key TLS PPI. In addition, several of these compounds were found to enhance the efficacy of cisplatin in cultured cells, highlighting their anti‐TLS potential.

Translesion synthesis (TLS) is a DNA damage tolerance mechanism that allows replicative bypass of DNA lesions, including DNA adducts formed by cancer chemotherapeutics. Previous studies demonstrated that suppression of TLS can increase sensitivity of cancer cells to first-line chemotherapeutics and decrease mutagenesis linked to the onset of chemoresistance, marking the TLS pathway as an emerging therapeutic target. TLS is mediated by a heteroprotein complex consisting of specialized DNA polymerases, including the Y-family DNA polymerase Rev1. Previously, we developed a screening assay to identify the first small molecules that disrupt the protein-protein interaction between the C-terminal domain of Rev1 (Rev1-CT) and the Rev1-interacting region (RIR) present in multiple DNA polymerases involved in TLS. Herein we report additional hit scaffolds that inhibit this key TLS PPI. In addition, through a series of biochemical, computational, and cellular studies we have identified preliminary structure-activity relationships and determined initial pharmacokinetic parameters for our original hits.

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