Quinazolinones as Bioisosteres of Naphthoquinones: A Path to Potent HsDHODH Inhibitors with Optimized Properties.

Human dihydroorotate dehydrogenase (HsDHODH) is a key enzyme in pyrimidine biosynthesis and a target for antiviral therapies against RNA viruses like SARS-CoV-2. Building on prior quinone-based inhibitors, we explored quinazol-inones as bioisosteric replacements to reduce cytotoxicity and off-target effects. Through structure-based design, we synthesized quinazol-inone derivatives aimed at maintaining critical binding interactions. First-generation compounds showed moderate HsDHODH inhibition (up to 60% at 250 μM), with compound 10c having an IC50 of 25 μM. Using computational modeling, we optimized second-generation derivatives, with 10e showing the highest potency (IC50 = 0.59 ± 0.03 μM) and significant antiviral activity against SARS-CoV-2 (EC50 = 0.15 ± 0.03 μM). These compounds demonstrated improved selectivity compared to naphtho-quinone analogs, though challenges with aqueous solubility remain. These results highlight quinazol-inones as promising scaffolds for further development of anti-SARS-CoV-2 therapies targeting HsDHODH.