Design, Synthesis, and Cellular Efficacy of Inositol-Requiring Enzyme Type 1 (IRE1α) Inhibitors

A library of 66 small molecules targeting IRE1α were designed using a molecular docking approach and prepared by a two-step reaction sequence using diverse substrates. All compounds utilized a 1-amino-4-bromonaphthalene core that was modified via Suzuki coupling with boronic acids to form intermediates that were carbamoylated to form urea-linked inhibitor candidates. We developed a 3³ DoE approach for the Suzuki coupling reaction that was optimized with 216 reactions via HTE. By screening the purified compounds in a tunicamycin-induced ER stress assay with ARPE-19 cells and quantifying their kinase inhibition activity by RT-qPCR, we identified 14 derivatives with the potential for IRE1α inhibition. IC₅₀ assays showed that six of the compounds displayed IRE1α inhibition alike KIRA6, a standard in IRE1α inhibition, with three of the leads possessing improved IC₅₀. Viability screens indicated that the best IRE1α inhibitors were not cytotoxic in the working concentrations and displayed improved protection from apoptosis compared to KIRA6.