Discovery of new chemical entities as potential leads against Mycobacterium tuberculosis

A series of biheterocyclic (1H-indole, benzofuran, pyrazolo[1,5-a]pyrimidine, pyrazolo[1,5-a]pyrimidin-5(4H)-one, imidazo[2,1-b]thiazole and pyrazolo[5,1-b]thiazole) derivatives were synthesized and evaluated for their anti-tubercular activities. The imidazo[2,1-b]thiazoles 9a–c and pyrazolo[5,1-b]thiazoles 10a–c exhibited promising anti-tubercular activity in varying degrees. Especially, the 2,6-dimethylpyrazolo[5,1-b]thiazole 10a exhibited strong suppressing function against H37Ra strain with MIC value of 0.03 μg/mL. Compound 10a also displayed good pharmacokinetic profiles with oral bioavailability (F) of 41.7% and a half-life of 13.4 h. Furthermore, 10a significantly reduced the bacterial burden in an autoluminescent H37Ra infected mouse model, suggesting its promising potential for development of anti-tubercular drugs.