L-685,458 is a selective and Potent inhibitor of γ-secretase with IC50 value of 17 nM[1]. γ-Secretase is one of intramenbrane-cleaving aspartyl protease which cleaves many type-I membrane proteins and many of them have important biological functions. γ-Secretase is a multi-subunit protease and it contains presenilin, nicastrin, APH-1(Anterior Pharynx- defective 1) and PEN-2. Presenilin contains Asp258 and Asp385 embedded in the sixth and seventh transmembrane domain and forms the active site. The feature of being a membrane integrated protease complex makes it difficult to be purified as well as studying its mechanism. γ-secretase is responsible for the generation Aβfrom the amyloid precusor protein. γ-Secretase has been considered as an important drug target for Alzheimer"s disease. γ-Secertase also is responsible for Notch processing which is related to cancer such as leukemia.L-685,458 is a transition state analogue inhibitor.It is a pan-inhibitor of γ-secretase which decrease the products of Aβ(42) and Aβ(40) peptides. It displays a selectivity of 50-fold or greater inhibition than a range of aspartyl, serine, and cysteine protease in vitro membrane assay. L-685,458 reduced the product both total Aβand Aβ42 in human primary neuronal cells with IC50 value of 115 nM for Aβand Aβ42 for 200 nM[2]. L-685,458 also inhibitedγ-secretase activity by characterizing the production of total secreted Aβby ELISA with IC50 value of about 5 nM in HEK 293 cells overexpressing human APP751.L-685,458 reduced the cortical total Aβwith a 50% reduction occurring at 100 mg/kg in a dose-dependent manner in PDAPP, and similar reductions in cortical Aβ42 were observed. L-685,458 decreased brain levels of Aβwhen given orally to Tg2576 mice that are transgenic for human APPV717F mutation. [3] L-685,458 also inhibit the Notch signaling, then affects embryonic development in zebrafish embryos[4].References: 1.Shearman MS, Beher D, Clarke EE, Lewis HD, Harrison T, Hunt P, Nadin A, Smith AL, Stevenson G, Castro JL: L-685,458, an aspartyl protease transition state mimic, is a potent inhibitor of amyloid beta-protein precursor gamma-secretase activity. Biochemistry 2000, 39(30):8698-8704.2.Dovey HF, John V, Anderson JP, Chen LZ, de Saint Andrieu P, Fang LY, Freedman SB, Folmer B, Goldbach E, Holsztynska EJ et al: Functional gamma-secretase inhibitors reduce beta-amyloid peptide levels in brain. J Neurochem 2001, 76(1):173-181.3.Lanz TA, Himes CS, Pallante G, Adams L, Yamazaki S, Amore B, Merchant KM: The gamma-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester reduces A beta levels in vivo in plasma and cerebrospinal fluid in young (plaque-free) and aged (plaque-bearing) Tg2576 mice. J Pharmacol Exp Ther 2003, 305(3):864-871.4.Geling A, Steiner H, Willem M, Bally-Cuif L, Haass C: A gamma-secretase inhibitor blocks Notch signaling in vivo and causes a severe neurogenic phenotype in zebrafish. EMBO Rep 2002, 3(7):688-694.