Tethered Aryl Groups Increase the Activity of Anti-Proliferative Thieno[2,3-b]Pyridines by Targeting a Lipophilic Region in the Active Site of PI-PLC

Abstract

The compounds 2-amino-3-carboxamido-thieno[2,3-b]pyridines have demonstrated excellent anti-proliferative activity against human cancer cell lines, including the triple-negative breast cancer cell line MDA-MB-231. In this study, 81 novel thieno[2,3-b]pyridines were synthesised in four series to further improve their anti-proliferative activity, in particular by targeting an adjacent lipophilic pocket in the putative target enzyme phosphoinositide phospholipase C (PI-PLC). Overall, it was found that appending a propyl-aryl group at C-5 on 2-amino-3-carboxamido-thieno[2,3-b]pyridine resulted in compounds with potent biological activity, exhibiting IC50 values in the nanomolar range. The propyl linker could be an α,β-unsaturated ketone or a saturated propyl ketone, but the highest activity was obtained when allylic alcohols were the tether between thieno[2,3-b]pyridine and the appended aryl group, with compound 21r having IC50 values lower than 50 nM. Compounds with one extra carbon in the tether (i.e., a four-atom chain) were found to be considerably less active. Molecular modelling revealed this propyl tether places the newly introduced aryl ring in an untargeted lipophilic pocket within the active site of the phosphoinositide phospholipase C (PI-PLC) enzyme.

Disruption of Crystal Packing in Thieno[2,3-b]pyridines Improves Anti-Proliferative Activity

“…For the remaining analogues, the decreased melting point was indicative of decreased crystal packing, and consequently, improved solubility. NMR experiments were performed with samples dissolved in DMSO-d6 so as to be consistent with previously obtained spectra for the thieno[2,3- b ]pyridines [ 1 , 20 ].…”

Synthesis and Anti-Proliferative Evaluation of Arctigenin Analogues with C-9′ Derivatisation

“…The anti-proliferative assays were conducted according to our previously reported methods. [ 36 , 37 , 38 ]. In short, cells were seeded in 96 well plates with 3000 cells per well and incubated with 10 µM of arctigenin-derived compounds for three days.…”

Novel Thieno [2,3-b]pyridine Anticancer Compound Lowers Cancer Stem Cell Fraction Inducing Shift of Lipid to Glucose Metabolism

“…( E )-3-Amino-5-(3-(3-bromophenyl)acryloyl- N -(3-chloro-2-methylphenyl)-6-methylthieno [2,3- b ]pyridine-2-carboxamide (compound 1 ) ( Figure 11 ) was prepared as reported [ 19 ] and dissolved in a minimum amount of dimethyl sulfoxide (DMSO) prior to dilution in buffer. Cancer cell lines MDA-MB-231 and MCF-7 were grown in a humidified incubator at 37 °C and 5% CO 2 in Dulbecco’s Modified Eagle Medium (DMEM, Sigma-Aldrich, Steinheim, Germany), enriched with 10% fetal bovine serum and 1% antibiotics.…”

“…The newly synthesized ( E )-3-amino-5-(3-(3-bromophenyl)acryloyl)- N -(3-chloro-2-methylphenyl)-6-methylthieno [2,3- b ]pyridine-2-carboxamide (Compound) [ 19 ] belongs to the group of thieno [2,3-b]pyridine, a family of compounds that were discovered by virtual screening [ 20 ], targeting phosphoinositide specific phospholipase C (pi-PLC) and which have been found to have antitumor activity on numerous tumor cell lines [ 21 ]. Whilst pi-PLC is a known target, other cellular targets are believed to be involved [ 22 ].…”

“…This increase in activity is proposed to be the result of increased overall lipophilicity and improved interactions of the compounds in a lipophilic pocket of the pi-PLC enzyme. Compound 1 utilized an alternative approach using a tethered propyl-aryl group, which has greater rotation freedom than the cycloalkyl derivatives, to interact with the lipophilic pocket, and resulted in improved antiproliferative activity [ 19 ]. Importantly, this class of compound has specifically been shown to inhibit of the growth of triple-negative breast cancer cell lines in nanomolar concentrations [ 19 , 26 ].…”