Design and Optimization of Spiro-Isatin-Thiazolidinone Hybrids with Promising Anticancer Activity

Background: Cancer remains a leading cause of morbidity and mortality worldwide, and current therapies are limited by toxicity, cost, and resistance. Inhibition of the MDM2-p53 interaction is a promising anticancer strategy, as this pathway is frequently dysregulated across tumors. Spiro-isatin-thiazolidinone derivatives have shown diverse biological activities, including anticancer effects, but require optimization to improve potency and selectivity. The aims were to design, synthesize, and evaluate novel spiro-isatin-thiazolidinone hybrids with enhanced cytotoxicity against cancer cells and reduced toxicity toward normal cells. Methods: Derivatives were designed using molecular docking against MDM2, followed by structural optimization. Cytotoxic activity was evaluated in vitro by MTT assays on human and murine cancer cell lines and pseudo-normal cells. Docking and 100 ns molecular dynamics simulations assessed binding stability, while ADMET properties were predicted in silico. Results: Several derivatives exhibited micromolar cytotoxicity, with compound 18 emerging as the most potent and selective candidate (IC₅₀ 6.67-8.37 µM across most cancer lines; >100 µM in HaCaT). Docking showed a strong affinity for MDM2 (-10.16 kcal/mol), comparable to the reference ligand, and stable interactions in simulations. ADMET predictions confirmed good oral bioavailability and moderate acute toxicity, fully compliant with Lipinski's Rule of Five. Overall, the newly synthesized spiro-isatin-thiazolidinone hybrids, particularly compound 18, demonstrated potent and selective anticancer activity, favorable pharmacokinetic properties and a good toxicity profile.