A scaffold repositioning approach: dihydroBenzoImidazoTriazineDione (BITD) derivatives as selective ALDH1A1 inhibitors

The overexpression of the Aldehyde Dehydrogenases 1A subfamily (ALDH1As) in various diseases, particularly in cancer, has made it an important target for therapeutic applications. Interestingly, the 1A1 isoenzyme plays a role in tumor initiation and progression, being identified as a biomarker for cancer stem cells. However, although promising, current ALDH1A1 inhibitors suffer from a lack of isoform selectivity and off-target toxicity. This study aims to address these limitations by developing a new class of ALDH1A1-selective inhibitors. By leveraging structural analogies with Isatin-based ALDH1A1 inhibitors, we designed compounds containing a dihydrobenzo[4,5]imidazo[2,1-c][1,2,4]triazine-3,4-dione (BITD) core, that emerged from a repositioning approach. Using a microwave-assisted protocol, a small library of derivatives was synthesized, and enzymatic assays highlighted a promising isoform specificity for ALDH1A1 among ALDH1As, with the best-in-class compound 5, showing an inhibition of the enzyme activity of 86% for ALDH1A1 and no inhibition for 1A2 and 1A3 isoenzymes. In silico studies further elucidated the binding mode of 5, providing a rational basis for the observed selectivity. These findings represent a promising strategy for the development of more selective ALDH1A1 inhibitors, laying the foundation for further optimization processes.