IRE1α kinase-IN-1 is a highly selective IRE1α (ERN1) inhibitor, with an IC50 of 77 nM, displaying 100-fold selectivity over the IRE1β isoform. It inhibits ER stress-induced IRE1α oligomerization and autophosphorylation, as well as IRE1α RNase activity (IC50=80 nM).

IRE1α kinase-IN-1 (compound 31) effectively mitigates endoplasmic reticulum stress by hindering IRE1α oligomerization and phosphorylation, while also suppressing its endoribonuclease activity within human cells[1]. This compound demonstrates high specificity, showing greater than 70% inhibition for only 4 out of 455 kinases tested, indicating its select focus on IRE1α. It attenuates recombinant G547 IRE1α KEN domain pS274 autophosphorylation with an IC50 of 160 nM and disrupts ATP-site LanthaScreen tracer binding to the recombinant dephosphorylated G547 IRE1α KEN with an IC50 of 0.27 μM[1]. Additionally, it prevents tunicamycin-induced GFP-IRE1α foci formation in HEK293 cells with an IC50 of 0.74 μM and obstructs both tunicamycin- and thapsigargin-induced IRE1α-dependent XBP1 mRNA splicing, with IC50 values ranging from 0.68 to 1.63 μM in the same cell line[1]. In H929 and NCI-H929 cells, IRE1α kinase-IN-1 dose-dependently suppresses IRE1α-dependent XBP1s mRNA expression when applied at concentrations between 0 to 20 μM, demonstrating its potent inhibitory activity on tunicamycin-induced XBP1s expression[1].