MKC8866, a salicylaldehyde analog, is a potent, selective IRE1 RNase inhibitor with an IC50 of 0.29 μM in human vitro. MKC8866 strongly inhibits Dithiothreitol-induced X-box-binding protein 1-spliced (XBP1s) expression with an EC50 of 0.52 μM and unstresses RPMI 8226 cells with an IC50 of 0.14 μM. MKC8866 inhibits IRE1 RNase in breast cancer cells leading to the decreased production of pro-tumorigenic factors and it can inhibits prostate cancer (PCa) tumor growth.
