Design, Synthesis, Molecular Modeling and Biological Evaluation of Novel Benzothiazole-Based 1,3,4-Thiadiazole Derivatives as Potential Anticancer Agents.

Objective: The present study aimed to design and synthesize a new series of benzothiazole analogues containing 1,3,4-thiadiazole, and assess their biological activities as potential anticancer agents.

Methods: N-(5,6-dimethylbenzo[d]thiazol-2-yl)-2-((5-(substituted amino)-1,3,4-thiadiazol-2-yl)thio)acetamide derivatives (4a-4h) were synthesized via the reaction of thiadiazole derivatives (3a-3h) with 2-chloro-N-(5,6- dimethylbenzo[d]thiazol-2-yl)acetamide (1) in the presence of potassium carbonate. All the target compounds have been characterized by spectral analysis. The anticancer activities of compounds 4a-4h were tested against two human HT-1376 bladder and HT-29 colorectal carcinoma cells using the WST-1 assay. Flow cytometry was used for the determination of apoptosis, cell cycle, and caspase 3/7 activity. Moreover, wound-healing assay was utilized to evaluate cell migration. In silico physicochemical, pharmacokinetics, and toxicological properties of compound 4g were determined by pkCSM, SwissADME, and SwissTargetPrediction online web tools.

Results: Among all synthesized derivatives, compound 4g (N-(5,6-dimethylbenzo[d]thiazol-2-yl)-2-((5-((3- methoxyphenyl)amino)-1,3,4-thiadiazol-2-yl)thio)acetamide) recorded the highest antiproliferative activity against HT-1376 cells with an IC50 as 26.51 μM at 24 h, which was less cytotoxic than cisplatin (IC50=14.85 μM). The combined treatment with compound 4g and cisplatin increased the cellular apoptosis with a higher impact compared with the cisplatin group. The higher accumulation of cells in the G2 phase, a significant increase of caspase 3/7 activity, and the inhibition of migration rate were also observed in HT-1376 following a combination of compound 4g and cisplatin treatment versus cisplatin alone, which might be involved in the apoptotic effects of compound 4g.

Conclusion: The in vitro anticancer potential of compound 4g lays the foundation for future research to focus on its value as a novel and advanced cancer therapy.