Design, Synthesis, and Evaluation of the Antitubercular Activity of 5-Phenyl Substituted-5, 6-dihydropyrido[2, 3-d]pyrimidine-4, 7(3H, 8H)-dione Compounds

Tuberculosis (TB) remains a major public health challenge, with research on new anti-TB drugs crucial for global TB elimination efforts. Here, we report a novel class of anti-TB agents. Especially, compounds 5b and 5j exhibited the highest activity [minimum inhibitory concentration (MIC) H37Rv: 0.16 and 0.12 μg/mL]. Chiral resolution was performed on compounds 5b and 5j; the isomers were evaluated for their activity and safety, confirming that the R-isomer 5bb and 5jb displayed significant anti-TB activity (MIC H37Rv: 0.03–0.06 μg/mL; MDR-Mtb: 0.125–0.06 μg/mL) and low hERG toxicity. Further evaluations on 5bb and 5jb demonstrated good metabolic stability, favorable kinetic parameters and oral bioavailability (F: 56.7 and 63.8%, respectively). The results of in vivo activity assessment indicate that 5bb and 5jb exhibit protective and therapeutic effects on zebrafish larvae and adult zebrafish infected with Mycobacterium marinum. Based on these results, compounds 5bb and 5jb are considered promising candidates for further in-depth studies.