begacestat and Alzheimer-Disease

The γ-secretase is a large transmembrane protein complex composed of four distinct units. It has aroused numerous attention over the past two decades as its intriguing role in mediating intramembrane proteolysis. γ-Secretase controls the cleavage of a broad ranged substrates, part of which have implicated in the pathogenesis of Alzheimer's disease, inflammation, and tumorigenesis. The disclosure of the atomic structure of the γ-secretase complex through cryo-EM in recent years has facilitated the understanding of its physiological roles, as well as enabled rational design of novel γ-secretase targeting molecules. This review highlights the recent progress of γ-secretase inhibitors and modulators under either clinical or preclinical stages, as well as their potential uses against various biological indications.

Topics: Alzheimer Disease; Amyloid Precursor Protein Secretases; Cell Membrane; Humans

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid Precursor Protein Secretases; Animals; Drug Discovery; Humans; Models, Biological; Protease Inhibitors

Several lines of evidence indicate that the production and deposition of amyloid-beta peptides (Abeta) contribute to the etiology of Alzheimer's disease. Inhibition or modulation of gamma-secretase, that is a responsible enzyme for the Abeta production, is one of the plausible therapeutics for Alzheimer's disease. However, the gamma-secretase is an unusual aspartic protease that cleaves the scissile bond within the transmembrane domain of several membrane protein including APP and Notch receptor. Thus, development of drugs that regulate the production of Abeta without affecting the Notch signaling is now demanding. Extensive drug screening and development allow that some secretase inhibitors and modulators have advanced into late-phase clinical trials, whereas the molecular mechanisms of Notch-sparing effect by these compounds effect still remain unknown. Identification of the molecular targets and mechanisms of these compounds using chemical biological approaches is currently underway. This review focuses on the recent development of inhibitors/modulators and provides a direction for the effective treatment of AD through inhibition/modulation of the gamma-secretase activity.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Clinical Trials as Topic; Drug Design; Enzyme Inhibitors; Humans; Sulfonamides; Tetrahydronaphthalenes; Thiophenes; Valine

γ-Secretase modulators (GSM), which reduce amyloidogenic Aβ(42) production while maintaining total Aβ levels, and Notch-sparing γ-secretase inhibitors (GSIs) are promising therapies for the treatment of Alzheimer's Disease (AD). To have a safety margin for therapeutic use, GSMs and GSIs need to allow Notch intracellular domain (NICD) production, while preventing neurotoxic Aβ peptide production. Typically, GSI and GSM effects on these substrates are determined using two different cell lines, one for the measurement of enzyme activity against each substrate. However, predicting selectivity for different substrates across cell systems may reduce the reliability of such ratios such that the in vitro data are not useful for predicting in vivo safety margins. This is especially concerning since the IC(50)'s of some GSIs vary depending upon the level of APP expression in a cell line. To circumvent this problem, we utilized the SUP-T1 cell line which expresses a truncated Notch receptor fragment that does not need sheddase cleavage to be a γ-secretase substrate. When combined with a sensitive method of measuring Aβ production, this assay system allows both substrates to be measured simultaneously, reducing the potential to calculate imprecise selectivity margins. To demonstrate the value of this system, known GSIs and GSMs were examined in the SUP-T1 dual substrate assay. IC(50)'s were determined for both substrates and the in vitro selectivity margin was calculated. These data suggest using a single cell line is a more accurate prediction of the fold difference between NICD inhibition and Aβ(42) lowering for therapeutically promising GSIs and GSMs.

Topics: Alanine; Alzheimer Disease; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Azepines; Cell Line; Enzyme Inhibitors; Humans; Oxadiazoles; Receptors, Notch; Solid Phase Extraction; Substrate Specificity; Sulfonamides; Thiophenes

A "second generation" γ-secretase, Begacestat (GSI-953), which is more selective against Notch-signaling, has shown promise in recent Phase I clinical trials. Begacestat, a novel, 2,5-disubsitituted thiophene sulfonamide from Wyeth (now Pfizer) is under evaluation for the treatment of Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid Precursor Protein Secretases; Animals; Clinical Trials as Topic; Enzyme Inhibitors; Humans; Sulfonamides; Thiophenes

The presenilin containing gamma-secretase complex is responsible for the regulated intramembraneous proteolysis of the amyloid precursor protein (APP), the Notch receptor, and a multitude of other substrates. gamma-Secretase catalyzes the final step in the generation of Abeta(40) and Abeta(42) peptides from APP. Amyloid beta-peptides (Abeta 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 Abeta 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 gamma-secretase inhibitor (GSI) that selectively inhibits cleavage of APP over Notch. This GSI inhibits Abeta production with low nanomolar potency in cellular and cell-free assays of gamma-secretase function, and displaces a tritiated analog of GSI-953 from enriched gamma-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 Abeta levels, and a reversal of contextual fear-conditioning deficits that are correlated with Abeta load. In healthy human volunteers, oral administration of a single dose of GSI-953 produces dose-dependent changes in plasma Abeta levels, confirming pharmacodynamic activity of GSI-953 in humans.

Topics: Adolescent; Adult; Alzheimer Disease; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Binding, Competitive; Cell Line; CHO Cells; Cricetinae; Cricetulus; Dogs; Enzyme Inhibitors; Fear; Female; Humans; Male; Mice; Mice, Transgenic; Middle Aged; Rats; Rats, Sprague-Dawley; Receptors, Notch; Signal Transduction; Sulfonamides; Thiophenes; Young Adult

SAR on HTS hits 1 and 2 led to the potent, Notch-1-sparing GSI 9, which lowered brain Abeta in Tg2576 mice at 100 mg/kg po. Converting the metabolically labile methyl groups in 9 to trifluoromethyl groups afforded the more stable analogue 10, which had improved in vivo potency. Further side chain modification afforded the potent Notch-1-sparing GSI begacestat (5), which was selected for development for the treatment of Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid Precursor Protein Secretases; Animals; Crystallography, X-Ray; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Discovery; Enzyme Inhibitors; Mice; Mice, Transgenic; Models, Molecular; Molecular Conformation; Receptor, Notch1; Stereoisomerism; Structure-Activity Relationship; Sulfonamides; Thiophenes