Design and development of novel Mycobacterium tuberculosisl-alanine dehydrogenase inhibitors

• Structure based virtual screening, we identified lead for MTB-L-AlaDH.
• Two leads were modified synthetically to obtain thirty novel analogues.
• The compounds were screened for MTB-L-AlaDH and antitubercular activities.
• Compound 14 showed IC50 of 0.58 ± 0.02 μM against enzyme and MIC of 1.79 μM.
• Active against dormant TB at 10 μM.

In the present study, we used crystal structure of MTB L-AlaDH protein complex with N6-methyl adenosine for structure based virtual screening of in house database to identify new small molecule inhibitors for MTB-L-AlaDH. Two molecules identified as better leads and were modified synthetically to obtain thirty novel analogues belonging to 2-iminothiazolidine-4-ones and 4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxamides. Among the screened compounds four (4n, 4o, 12 and 14) emerged as potent inhibitors displaying IC50 values ranging from 0.58 ± 0.02 to 1.74 ± 0.03 μM against MTB-L-AlaDH and were non-cytotoxic at 50 μM. Some of these synthesized compounds also exhibited good activity against nutrient starved dormant MTB cells. The most potent inhibitors were found to stabilize the protein which was confirmed biophysically through differential scanning fluorimetry.

Compound tert-butyl 3-carbamoyl-2-(4-chlorobenzamido)-4,5-dihydrothieno[2,3-c]pyridine-6(7H)-carboxylate (14) was the most promising potent inhibitor with an IC50 of 0.58 ± 0.02 μM against Mycobacterium tuberculosis L-Aleph enzyme, with a good MTB MIC of 1.79 μM, and was not cytotoxic at 50 μM in eukaryotic cell lines.Figure optionsDownload as PowerPoint slide