Updated project metadata. Inositol Requiring Enzyme 1 (IRE1) is a bifunctional serine/threonine kinase and endoribonuclease that is a major mediator of the Unfolded Protein Response (UPR) during endoplasmic reticulum (ER) stress. Tumor cells experience ER stress due to adverse environmental cues such as hypoxia or nutrient shortage and high metabolic/protein folding demand. To cope with those stresses, cancer cells utilize IRE1 signaling as an adaptive mechanism. Here we report the discovery of novel family of compounds as IRE1 inhibitors identified through a structural exploration of the IRE1 kinase domain. All the inhibitors were tested for their ability to sensitize glioblastoma (GBM) cells to chemotherapy. We show that all molecules identified inhibit IRE1 signaling and sensitize glioblastoma cells to the standard of care chemotherapy temozolomide (TMZ). From these inhibitors we selected one that was able to cross the Brain Blood Barrier (BBB) and evaluated its capacity to inhibit tumor growth and avoid relapse in vivo. These results support the attractiveness of IRE1 as an adjuvant therapeutic target in GBM; a common and wholly fatal diagnosis. In addition, they provide scope for quickly testing IRE1 inhibitor suitability in GBM as adjuvant therapy due to their current status for clinical use.