Pyr6 is a selective inhibitor of calcium release from the endoplasmic reticulum via STIM1/Orai1 mediated, store operated calcium entry (SOCE). Pyr6 blocks SOCE in thapsigargin treated, calcium depleted BRL-2H3 cells (IC50 = 0.49 μM), but has poor activity against carbachol-induced, TRPC3-mediated calcium entry in TRPC3-transfected HEK293 cells (IC50 = 18.46 μM).