Design, synthesis, and mechanistic evaluation of novel pyrazole/thiazole chalcone hybrids as dual tubulin polymerization and COX-2 inhibitors with potent antiproliferative activity

A novel series of pyrazole/thiazole chalcone hybrids (9a–o) was designed, synthesized, and evaluated as dual tubulin/COX-2 inhibitors with anticancer activity. The synthesized compounds were screened for antiproliferative activity against MDA-MB-231, HCA-7, and A549 cancer cell lines. Several derivatives exhibited promising activity, with 9m being the most potent against MDA-MB-231 cells (IC50 = 1.96 ± 0.10 µM), while 9l emerged as the most balanced lead compound, showing strong antiproliferative activity against HCA-7, MDA-MB-231, and A549 cells with IC₅₀ values of 2.18 ± 0.11, 2.92 ± 0.15, and 4.86 ± 0.25 µM, respectively. Mechanistic studies revealed that the anticancer activity of this series is mediated through a dual mechanism involving tubulin polymerization inhibition and selective COX-2 inhibition. In particular, compound 9l inhibited tubulin polymerization with an IC₅₀ of 4.21 ± 0.25 µM and showed potent COX-2 inhibition (IC₅₀ = 0.10 ± 0.01 µM) with high selectivity over COX-1 (IC₅₀ = 10.92 ± 0.78 µM; selectivity index = 109.20). Further investigation in HCA-7 cells demonstrated that 9l significantly increased Bax level to 438.64 ± 15.72 pg mL⁻¹ and reduced Bcl-2 to 6.74 ± 0.19 pg mL⁻¹, while markedly elevating caspase-3 and caspase-9 levels to 496.80 ± 14.90 pg mL⁻¹ and 47.86 ± 1.18 ng mL⁻¹, respectively. Moreover, 9l strongly suppressed PGE-2 production to 0.56 ± 0.04 ng mL⁻¹, corresponding to 89.2% inhibition, and induced G2/M cell-cycle arrest. It also showed promising anti-migratory activity in the wound-healing assay, favorable microsomal stability, and acceptable in silico ADMET properties. Molecular docking further supported its favorable binding within the active sites of both tubulin and COX-2. Collectively, these findings identify 9l as a promising dual tubulin/COX-2-targeting anticancer candidate.