Studies of Aβ Pharmacodynamics in the Brain, Cerebrospinal Fluid, and Plasma in Young (Plaque-Free) Tg2576 Mice Using the γ-Secretase Inhibitor N2-[(2S)-2-(3,5-Difluorophenyl)-2-hydroxyethanoyl]-N1-[(7S)-5-methyl-6-oxo-6,7-dihydro-5H-dibenzo[b,d]azepin-7-yl]-L-alaninamide (LY-411575)

Substituted thiazolamide coupled to a redox delivery system: a new γ-secretase inhibitor with enhanced pharmacokinetic profile

Inhibition of gamma-secretase, one of the enzymes responsible for the cleavage of the amyloid precursor protein (APP) to produce pathogenic A beta peptides, is an attractive approach for the treatment of Alzheimer's disease. We have designed a new gamma-secretase thiazolamide inhibitor bearing a dihydronicotinoyl moiety as Redox Delivery System which allows specific delivery of the drug to the brain. Through, on the one hand, A beta peptide production measurements by specific in vitro assays (gamma-secretase Cell Free assay and Cell Based assay on HEK 293 APP transfected cells) and, on the other hand, pharmacokinetic studies on animal models, the new inhibitor shows a good pharmacokinetic profile as well as a potent gamma-secretase inhibitory activity in vitro. From the obtained results, it is expected that drug will be mainly delivered to the CNS with low diffusion in the peripheral tissues. Consequently the side effects of this gamma-secretase inhibitor on the immune cells could be reduced.

Dynamics of {beta}-amyloid reductions in brain, cerebrospinal fluid, and plasma of {beta}-amyloid precursor protein transgenic mice treated with a {gamma}-secretase inhibitor

gamma-Secretase inhibitors are one promising approach to the development of a therapeutic for Alzheimer's disease (AD). gamma-Secretase inhibitors reduce brain beta-amyloid peptide (Abeta), which is believed to be a major contributor in the etiology of AD. Transgenic mice overexpressing the human beta-amyloid precursor protein (APP) are valuable models to examine the dynamics of Abeta changes with gamma-secretase inhibitors in plaque-free and plaque-bearing animals. BMS-299897 2-[(1R)-1-[[(4-chlorophenyl)sulfony](2,5-difluorophenyl)amino]ethyl]-5-fluorobenzenepropanoic acid, a gamma-secretase inhibitor, showed dose- and time dependent reductions of Abeta in brain, cerebrospinal fluid (CSF), and plasma in young transgenic mice, with a significant correlation between brain and CSF Abeta levels. Because CSF and brain interstitial fluid are distinct compartments in composition and location, this correlation could not be assumed. In contrast, aged transgenic mice with large accumulations of Abeta in plaques showed reductions in CSF Abeta in the absence of measurable changes in plaque Abeta in the brain after up to 2 weeks of treatment. Hence, CSF Abeta levels were a valuable measure of gamma-secretase activity in the central nervous system in either the presence or absence of plaques. Transgenic mice were also used to examine potential side effects due to Notch inhibition. BMS-299897 was 15-fold more effective at preventing the cleavage of APP than of Notch in vitro. No changes in the maturation of CD8(+) thymocytes or of intestinal goblet cells were observed in mice treated with BMS-299897, showing that it is possible for gamma-secretase inhibitors to reduce brain Abeta without causing Notch-mediated toxicity.

Lack of specific amyloid-beta(1-42) suppression by nonsteroidal anti-inflammatory drugs in young, plaque-free Tg2576 mice and in guinea pig neuronal cultures

Recent studies indicating that some nonsteroidal anti-inflammatory drugs (NSAIDs) selectively modulate gamma-secretase cleavage of amyloid precursor protein (APP) while sparing Notch processing have generated interest in discovery of novel gamma-secretase modulators with the "NSAID-like" efficacy profile. The objective of the present studies was to compare the efficacy of a subset of NSAIDs with previously reported classical gamma-secretase inhibitors LY-411575 [N(2)-[(2S)-2-(3,5-difluorophenyl)-2-hydroxyethanoyl]-N(1)-[(7S)-5-methyl-6-oxo-6,7-dihydro-5H-dibenzo[b,d]azepin-7-yl]-L-alaninamide]and DAPT [N-[N- (3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester] in Tg2576 mice. Flurbiprofen (10 and 25 mg/kg/day) was overtly toxic and elicited significant (but nonselective) reductions in both Abeta(1-40) and Abeta(1-42) in the plasma in one of two studies. Flurbiprofen also produced a small reduction in Abeta(1-40) in the cortex at 25 mg/kg/day but did not affect Abeta levels in hippocampus or cerebrospinal fluid. Ibuprofen and sulindac sulfide were neither overtly toxic nor efficacious at doses up to 50 mg/kg/day. The effects of NSAIDs LY-411575 and DAPT were tested in guinea pig embryonic neuronal cultures to determine whether the selective reductions in Abeta(1-42) observed in cell lines overexpressing human mutant APP can be reproduced in a neuronal model of physiological Abeta production and secretion. Flurbiprofen and sulindac nonselectively reduced Abeta(1-40) and Abeta(1-42) at concentrations > or =125 microM, although cytotoxicity was noted at > or =250 microM sulindac. Ibuprofen had no effect at concentrations up to 500 microM. In contrast, DAPT and LY-411575 potently and completely inhibited Abeta(1-40), Abeta(1-42), and Abeta(1-38) in the absence of cytotoxicity. The divergence of the present data from published reports raises the need to examine the conditions necessary to perceive selective Abeta(1-42) reduction by NSAIDs in neuronal tissue.

A signal peptide peptidase (SPP) reporter activity assay based on the cleavage of type II membrane protein substrates provides further evidence for an inverted orientation of the SPP active site relative to presenilin

Signal peptide peptidase (SPP) is an intramembrane-cleaving protease identified by its cleavage of several type II membrane signal peptides after signal peptidase cleavage. Here we describe a novel, quantitative, cell-based SPP reporter assay. This assay utilizes a substrate consisting of the NH2 terminus of the ATF6 transcription factor fused to a transmembrane domain susceptible to SPP cleavage in vitro. In cells, cleavage of the substrate releases ATF6 from the membrane. This cleavage can be monitored by detection of an epitope that is unmasked in the cleaved substrate or by luciferase activity induced by the cleaved ATF6 substrate binding to and activating an ATF6 luciferase reporter construct. Using this assay we show that (i) SPP is the first aspartyl intramembrane-cleaving protease whose activity increases proportionally to its overexpression and (ii) selectivity of various SPP and gamma-secretase inhibitors can be rapidly evaluated. Because this assay was designed based on data suggesting that SPP has an orientation distinct from presenilin and cleaves type II membrane proteins, we determined whether the segment of SPP located between the two presumptive catalytic aspartates was in the lumen or cytoplasm. Using site-directed mutagenesis to insert an N-linked glycosylation site we show that a portion of this region is present in the lumen. These data provide strong evidence that although the SPP and presenilin active sites have some similarities, their presumptive catalytic domains are inverted. This assay should prove useful for additional functional studies of SPP as well as evaluation of SPP and gamma-secretase inhibitors.