Abstract
The presenilin containing γ-secretase complex is responsible for the regulated intramembraneous proteolysis of the amyloid precursor protein (APP), the Notch receptor, and a multitude of other substrates. γ-Secretase catalyzes the final step in the generation of Aβ40 and Aβ42 peptides from APP. Amyloid β-peptides (Aβ peptides) aggregate to form neurotoxic oligomers, senile plaques, and congophilic angiopathy, some of the cardinal pathologies associated with Alzheimer's disease. Although inhibition of this protease acting on APP may result in potentially therapeutic reductions of neurotoxic Aβ peptides, nonselective inhibition of the enzyme may cause severe adverse events as a result of impaired Notch receptor processing. Here, we report the preclinical pharmacological profile of GSI-953 (begacestat), a novel thiophene sulfonamide γ-secretase inhibitor (GSI) that selectively inhibits cleavage of APP over Notch. This GSI inhibits Aβ production with low nanomolar potency in cellular and cell-free assays of γ-secretase function, and displaces a tritiated analog of GSI-953 from enriched γ-secretase enzyme complexes with similar potency. Cellular assays of Notch cleavage reveal that this compound is approximately 16-fold selective for the inhibition of APP cleavage. In the human APP-overexpressing Tg2576 transgenic mouse, treatment with this orally active compound results in a robust reduction in brain, plasma, and cerebral spinal fluid Aβ levels, and a reversal of contextual fear-conditioning deficits that are correlated with Aβ load. In healthy human volunteers, oral administration of a single dose of GSI-953 produces dose-dependent changes in plasma Aβ levels, confirming pharmacodynamic activity of GSI-953 in humans.
- αAPPs, APP α-secretase-cleaved soluble fragment
- Aβ, β-amyloid peptide
- AD, Alzheimer's disease
- APP, amyloid precursor protein
- BBB, blood-brain barrier
- βCTF, APP β-secretase-cleaved carboxy-terminal fragment
- PS, presenilin
- GS, γ-secretase
- GSI, γ-secretase inhibitor
- Amgen GSI, 4-fluoro-N-[(1R,2R,4S)-1,3,3-trimethylbicyclo[2.2.1]hept-2-yl]benzenesulfonamide
- BMS GSI, (2R)-2-{[5-chloro-2-(hydroxymethyl)phenyl][(4-chlorophenyl)sulfonyl]amino}propylpropylcarbamate
- DAPT, tert-butyl (2S)-({N-[(3,5-difluorophenyl)acetyl]-l-alanyl}amino)(phenyl) ethanoate
- GSI-953, 5-chloro-N-[(1S)-3,3,3-trifluoro-1-(hydroxymethyl)-2-(trifluoromethyl)propyl]thiophene-2-sulfonamide
- GSI-953 analog, 5-chloro-N-[(1S,2R)-4,4,4-trifluoro-1-(hydroxymethyl)-2-methylbutyl]thiophene-2-sulfonamide
- LY411575, 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
- LY450139, (2S)-2-hydroxy-3-methyl-N-((1S)-1-methyl-2-{[(1S)-3-methyl-2-oxo-2,3,4,5-tetrahydro-1H-3-benzazepin-1-yl]amino}-2-oxoethyl)butanamide
- L685458, N-{(2R,4R,5S)-2-benzyl-5-[(tert-butoxycarbonyl)amino]-4-hydroxy-6-phenylhexanoyl}-l-leucyl-l-phenylalaninamide
- CFC, contextual fear conditioning
- CSF, cerebral spinal fluid
- NICD, Notch intracellular domain
- SEAP, secreted alkaline phosphatase
- ELISA, enzyme-linked immunosorbent assay
- CHAPSO, 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonic acid
- MED, minimal efficacious dose
- MES, 4-morpholineethanesulfonic acid (systematic)
- WT, wild type
- SP, single-positive
- DP, double-positive
- PK, pharmacokinetic
- GI, gastrointestinal.
Footnotes
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This research was supported by Wyeth Research.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.109.152975
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1 Subsequent to the submission of this manuscript, we synthesized and tested BMS-708163 in-house as a comparator to GSI-953. BMS-708163 displayed an EC50 of 4.5 nM in the cell-based assay, Notch selectivity of 26-fold, and reduced brain levels of Aβ40 and Aβ42 by 43 and 33%, respectively, in Tg2576 mice following a single oral administration (10 mg/kg) of compound.
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ABBREVIATIONS:
- Received March 6, 2009.
- Accepted August 10, 2009.
- © 2009 by The American Society for Pharmacology and Experimental Therapeutics
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