IRE1 RNase inhibitors (including B-I09, STF083010, MKC3946, and MKC8866) have shown good therapeutic performance in multiple myeloma (MM), breast cancer, prostate cancer, melanoma, lymphoma, and chronic lymphocytic leukemia (Tang et al., 2014; Logue et al., 2018; Xie et al., 2018; Zhao et al., 2018; Sheng et al., 2019; Jin and Saatcioglu, 2020). The gene discussed is ERN1; the disease is breast cancer.