Discovery and Characterization of Diverse Non-nucleotide Inhibitors of DNPH1 Using an Integrated Hit Finding Strategy.

DNPH1 is a hydrolase enzyme that degrades the noncanonical nucleotide 5-hydroxymethyl-2'-deoxyuridine 5'-monophosphate (hmdUMP), thus acting as a nucleotide pool sanitizer by preventing its aberrant incorporation into DNA. Recent studies have shown that loss of DNPH1 enhances the sensitivity of homologous recombination repair-deficient cancer cells to PARP inhibitors, highlighting its potential as an attractive therapeutic target. Herein we report the design and prosecution of an integrated hit finding strategy combining high-throughput screening, DNA-encoded library screening, and fragment-based lead generation which enabled the discovery of the first non-nucleotide ligands for DNPH1. We compare four hit compounds which differ markedly in their chemical structures, physicochemical properties, and binding modes and summarize parallel hit-to-lead workup efforts. We also provide discussion of the merits of an integrated approach for hit discovery when applied to challenging novel targets such as DNPH1.