Synthesis, stability and activity of the prodrugs of dihydroorotate dehydrogenase inhibitors

This study was conducted to improve structural instability of a highly active DHODH inhibitor A found in our group. Twelve prodrugs were synthesized by modifying the carboxyl group. The enzyme activity test of 12 prodrugs A1−A12 demonstrated that A1−A5 displayed weak inhibitory activity, and A6−A12 displayed no activity, which met the action mechanism of designed prodrug. The structural stability of A1−A12 in methanol and pH 2.0, 9.0 buffers were tested, and the results showed that A12 could avoid intramolecular ring-formation in CH₃OH, A1−A8 were easily hydrolyzed under acidic conditions, and A9−A12 were inclined to hydrolyze under alkaline conditions. The cell proliferation inhibitory activity of 12 prodrugs were evaluated, in which compound A12 displayed excellent activity (IC₅₀=0.63 μmol·L⁻¹) similar to brequinar. These results laid a good foundation for conducting further vivo studies.