ISR activator 2 is a selective ISR activator that targets the integrated stress response. It preferentially activates the ISR by binding to the cytosolic pattern recognition receptor RIG-I, which subsequently activates the heme-regulated inhibitor (HRI) ISR kinase, independent of the interferon response. ISR activator 2 is utilized in pancreatic cancer research.

ISR activator 2, also known as Compound A8, at a concentration of 10 μM for 8 hours, induces the enrichment of UPR (unfolded protein response) and mTORC1 signaling pathway gene sets in HEK293T cells. This enrichment is due to increased expression of ISR target genes such as ASNS, DDIT4, CHAC1, and CHOP. In a concentration-dependent manner, ISR activator 2 (16 hours) activates the ATF4-FLuc reporter gene in HEK293T cells stably expressing ATF4-FLuc (EC50 = 10.53 μM), and this activation is inhibited by the ISR inhibitor ISRIB (200 nM). At 10 μM for 16 hours, ISR activator 2 activates the ATF4-mAPPLE reporter gene in HEK293T cells stably expressing it, though HRI knockdown completely blocks this activation, whereas knockdown of PERK, GCN2, or PKR does not affect it. ISR activator 2 inhibits the binding of RIG-I to a dsRNA probe in a concentration-dependent manner (K D = 0.764 μM) at concentrations ranging from 0.625-5 μM. RIG-I knockdown blocks the ISR activator 2 (10 μM, 4 hours) induced increase in expression of CHAC1 and CHOP. ISR activator 2 also promotes lipid droplet clearance in a concentration-dependent manner in MEFWT cells and remains effective in ISR-deficient cells (MEFA/A) over 20 hours. At 10 μM for 4 hours, the compound demonstrates distinct ISR activation and lipid droplet clearance activities via its metabolite CC81 in HEK293T and SW1990 cells.