Design, synthesis, and bioevaluation of pyrazole-containing tubulin polymerisation inhibitors based on conformational...

Based on conformational preference of SMART analogues and conformational constraint strategy, two series of new tubulin polymerisation inhibitors (4a - 4k and 5a - 5h/6a - 6h) were designed via hydrogen bonding, steric effect (for 4a - 4k) and ring-closing approach by fused five- and seven-membered ring (for 5a - 5h/6a - 6h) which was first adopted in the design of new SMART analogues. Among these compounds, 4k and 5a showed potent activities with IC₅₀ values of 15 nM and 6 nM against PC-3 cell line. Mechanism studies indicated that 4k and 5a could inhibit tubulin polymerisation, arrest cell cycle at G₂/M phase, induce cell apoptosis, and inhibit cell migration and colony formation. Molecular docking suggested that compounds 4k and 5a could bind into the colchicine binding site at the pose similar to DAMA-colchicine. Western blot assays revealed that 4k and 5a regulated the expression of cell cycle and apoptosis-related proteins. Prediction of physicochemical properties indicated good drug-likeness of 4k and 5a.