Purity ~98% (HPLC). Cell-permeable. A potent and selective γ-secretase inhibitor (IC50 = 17 nM). Displays > 50-fold selectivity over a range of aspartyl, serine and cysteine proteases. Exhibits equal potency for inhibition of Aβ40 and Aβ42 peptides (IC50 values are 48 and 67nM respectively in human neuroblastoma cells).