A synthesis, in silico, in vitro and in vivo study of thieno[2,3-b]pyridine anticancer analogues

The anticancer activity of the thieno[2,3-b]pyridines was explored by altering the ring size of the cyclo-aliphatic moiety. Five-, six-, seven- and eight-membered derivatives were tested against the NCI60 tumour cell panel. According to this assay the most active derivative 9a has a cyclooctane moiety, which suggests that larger aliphatic ring systems are favourable. For the most sensitive tumour cell line MB-MDA-435, derivative 9a has a GI₅₀ = 70 nM and a LC₅₀ = 925 nM. To explore the biological mechanism of the thieno[2,3-b]pyridines five derivatives were tested against tyrosyl-DNA phosphodiesterase I (TDP1), a phospholipase D enzyme, using a biochemical assay. The most potent derivative for TDP1 was 9d, giving an excellent IC₅₀ at 0.5 ± 0.1 μM. Also, derivative 12 was tested against 97 kinases and no or very limited activity was found, excluding this class of biomolecular targets. Finally, a mouse xenograft study using derivative 12 was encouraging but the tumour size/mass reduction was not quite statistically significant.