An inhibitor of IRE1α; inhibits ER stress induced XBP1 splicing and reduces expression of the XBP1 target genes SEC61A1, p58IPK, and ERdj4 in RPMI 8226 cells; cytotoxic to multiple myeloma cell lines but has no effect on normal mononuclear cells; reduces tumor growth and XBP1 splicing in an RPMI 8226 mouse xenograft model (100 mg/kg)