Design, synthesis and in vitro anti-proliferative evaluation of new pyridine-2,3-dihydrothiazole/thiazolidin-4-one hybrids as dual CDK2/GSK3β kinase inhibitors

Abstract

Herein, the molecular hybridization drug discovery approach was used in the design and synthesis of twelve novel pyridine-2,3-dihydrothiazole hybrids (2a,b–5a,b and 13a,b–14a,b) and fourteen pyridine-thiazolidin-4-one hybrids (6a,b–12a,b) as anti-proliferative analogues targeting CDK2 and GSK3β kinase inhibition. Almost all of the newly synthesized hybrids, including their precursors (1a,b), were evaluated for their anti-proliferative activity against three human cancer cell lines—MCF-7, HepG2 and HEp-2—as well as normal Vero cell lines. Both compounds 1a (pyridine-thiourea precursor) and 8a (pyridine-5-acetyl-thiazolidin-4-one hybrid) exhibited excellent anti-proliferative activity against HEp-2 (IC₅₀ = 7.5 μg mL⁻¹, 5.9 μg mL⁻¹, respectively). Additionally, 13a (pyridine-5-(p-tolyldiazenyl-2,3-dihydrothiazole)) hybrid demonstrated excellent anti-proliferative activity against HepG2 (IC₅₀ = 9.5 μg mL⁻¹), with an acceptable safety profile against Vero (<45% inhibition at 100 μg mL⁻¹) in the cases of 8a and 13a alone. The three promising anti-proliferative hybrids (1a, 8a, 13a) were selected for the assessment of their in vitro inhibitory kinase activity against CDK2/GSK3β using roscovitine (IC₅₀ = 0.88 μg mL⁻¹) and CHIR-99021 (IC₅₀ = 0.07 μg mL⁻¹) as references, respectively. Compound 13a was the most potent dual CDK2/GSK3β inhibitor (IC₅₀ = 0.396 μg mL⁻¹, 0.118 μg mL⁻¹, respectively) followed by 8a (IC₅₀ = 0.675 μg mL⁻¹, 0.134 μg mL⁻¹, respectively), and the weakest was 1a. To elucidate the mechanism of the most potent anti-proliferative 13a hybrid, further cell cycle analysis was performed revealing that it caused G1 cell cycle arrest and induced apoptosis. Moreover, it resulted in an increase in Bax and caspase-3 with a decrease in Bcl-2 levels in HepG2 cells compared with untreated cells. Finally, in silico drug likeness/ADME prediction for the three potent compounds as well as a molecular docking simulation study were conducted in order to explore the binding affinity and interactions in the binding site of each enzyme, which inspired their usage as anti-proliferative leads for further modification.