Discovery and Optimization of a Non-Nucleoside-Based Series of Inhibitors of 2'-Deoxynucleoside 5'-Monophosphate Glycosidase (DNPH1)

DNPH1 is a nucleotide pool sanitizer that cleaves 5-hydroxymethyl-2-deoxyuridine-5-monophosphate (hmdUMP), preventing incorporation of the correspondent non-natural nucleotide into DNA. Recent findings have demonstrated that loss of DNPH1 could potentiate the sensitivity of PARP inhibitors in homologous recombination repair (HRR)-deficient cancers. We report the optimization of a non-nucleoside-based series of DNPH1 inhibitors. Starting from a weak compound 1 (binding affinity pIC₅₀ 4.7), we identified compound 38 as a very potent inhibitor of DNPH1 (pIC₅₀ 9.3) using DNPH1 X-ray structure-guided drug design. Compound 38 demonstrated target engagement of DNPH1 in the SUM149PT cell line (pIC₅₀ 7.2). Using this tool compound, we then report the in vitro pharmacology of a DNPH1 inhibitor in the BRCA1 mutant SUM149PT cell line.