Quantitative Measurement of Changes in Amyloid-β(40) in the Rat Brain and Cerebrospinal Fluid following Treatment with the γ-Secretase Inhibitor LY-411575 [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]

Abstract

The efficacy of ␥-secretase inhibitors in vivo has, to date, been generally assessed in transgenic mouse models expressing increased levels of amyloid-␤ (A␤) peptide thereby allowing the detection of changes in A␤ production. However, it is not clear whether the in vivo potency of ␥-secretase inhibitors is independent of the level of amyloid precursor protein expression. In other words, does a ␥-secretase inhibitor have the same effect in nontransgenic physiological animals versus transgenic overexpressing animals? In the present study, an immunoassay has been developed which can detect A␤(40) in the rat brain, where concentrations are much lower than those seen in transgenic mice such as Tg2576 (c. 0.7 and 25 nM, respectively) and in cerebrospinal fluid (CSF, c. 0.3 nM). Using this immunoassay, the effects of thewere assessed and robust dose-dependent reductions in rat brain and CSF A␤(40) levels were observed with ID 50 values of 1.3 mg/kg for both brain and CSF. These values were comparable with those calculated for LY-411575 in transgenic mice.Time course experiments using LY-411575 demonstrated comparable temporal reductions in rat brain and CSF A␤(40), further suggesting these two pools of A␤ are related. Accordingly, when all the data for the dose-response curve and time course were correlated, a strong association was observed between the brain and CSF A␤ (40) levels. These data demonstrate the utility of the rat as a novel approach for assessing the effects of ␥-secretase inhibitors on central nervous system A␤(40) levels in vivo.Alzheimer's disease (AD) is one of the major neurological diseases of the elderly, characterized histopathologically by protein deposits in the brain parenchyma (plaques) or blood vessels and intracellular neurofibrillary tangles of abnormally phosphorylated protein. The plaques mainly consist of the A␤ peptides originating from cleavage of the amyloid precursor protein (APP), with the majority being the more hydrophobic A␤(42) which is particularly prone to aggregation (Selkoe 2001). Furthermore, the identification of APP gene mutations in familial Alzheimer's disease (FAD) cases gives evidence of the involvement of APP processing in AD (Goate et al., 1991;Hardy, 1997).The enzymes responsible for processing APP into A␤ are the aspartyl proteases, ␤-amyloid cleaving enzyme (BACE or 1 These authors contributed equally to this publication. Article, publication date, and citation information can be found at

Cerebrovascular Dysfunction in Amyloid Precursor Protein Transgenic Mice: Contribution of Soluble and Insoluble Amyloid-β Peptide, Partial Restoration via γ-Secretase Inhibition

“…We hypothesized that acute depletion of soluble Aβ via γ-secretase inhibition would improve vessel function. We assessed vessel reactivity in young Tg2576 mice in the presence and absence of significant extracellular brain and plasma human Aβ utilizing the blood-brain barrier permeable γ–secretase inhibitor, LY411575 (Cirrito et al, 2003; Best et al, 2005). Similar to previous results (Cirrito et al, 2005b), subcutaneous administration of LY411575 (3 mg/kg) in young Tg2576 mice resulted in almost complete depletion of soluble human Aβ 1-x pool in the interstitial fluid (ISF) up to 36 h after drug administration (Fig.…”

Inhibitors of signal peptide peptidase (SPP) affect HSV-1 infectivity in vitro and in vivo

“…The γ-secretase inhibitor LY-450139 is one of the most potent inhibitors and is currently in phase II clinical trials and it appears to be well tolerated in human Alzheimer’s patients (Siemers et al, 2006). While this inhibitor is the only one currently being tested in humans, other SPP inhibitors, such as LY-411,575 (Eli Lilly), BMS-299,897 (Bristol-Meyers Squibb) and DAPT (Eli Lilly) have been studied for their effect in vivo (Best et al, 2005; Dovey et al, 2001; Siemers et al, 2005; Siemers et al, 2006). In this study we have shown for the first time that SPP chemical inhibitors are able to block HSV-1 infectivity in vitro.…”

Inhibition and Modulation of γ-Secretase for Alzheimer's Disease

“…Benzodiazepine analogue LY-411575 and benzolactam LY-450139, developed at Eli Lilly, are highly potent γ-secretase inhibitors that have been tested extensively in vivo 56–58. LY- 411575 is one of the most potent γ-secretase inhibitors yet reported, with an IC 50 of 119 pM for inhibiting Aβ production in APP-overexpressing HEK293 cells.…”