Phosphorylation product of inositol 1,4,5-trisphosphate (Ins (1,4,5)P3). Potent inhibitor of Ins (1,4,5)P3 5-phosphatase (IC50 ~150 nM); facilitates Ca2+ influx by sensitizing Ins (1,4,5)P3-mediated activation of ICRAC. At higher concentrations, acts as an inhibitor of Ins (1,4,5)P3 receptors.