STF-083010 is an inhibitor of the IRE1/XBP1 pathway, blocking IRE1 endonuclease activity without affecting its kinase activity after endoplasmic reticulum (ER) stress both in vitro and in vivo. STF-083010 (60 µM) reduces the splicing of XBP1 by IRE1 in the presence of thapsigargin (Item No. 10522), an ER stress inducer. This has cytotoxic effects against multiple myeloma cells and drives apoptosis in pancreatic cancer cells.