YUM70 (YUM-70) is a novel and potent GRP78 (glucose-regulated protein 78) inhibitor (IC50=1.5 μM) with anticancer activity. It induces endoplasmic reticulum (ER) stress-mediated apoptosis in pancreatic cancer. YUM70 inhibits pancreatic cancer cell growth in vitro and showed in vivo efficacy in a pancreatic cancer xenograft model with no toxicity to normal tissues. Importantly, YUM70 directly binds GRP78 and inactivates its function. Moreover, YUM70-PROTAC forces the degradation of GRP78 in pancreatic cancer cells. YUM70 is an ER stress inducer and kills cells by activating the apoptosis pathway. Especially, YUM70 treatment induces ER stress and triggers UPR by inhibiting GRP78.