An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Alzheimer’s disease is the most prevalent cause of dementia and is associated with accumulation of amyloid- β peptide (A β ), particularly the 42-amino acid A β 1-42, in the brain. A β 1-42 levels can be decreased by γ -secretase modulators (GSM), which are small molecules that modulate γ -secretase, an enzyme essential for A β production. BMS-869780 is a potent GSM that decreased A β 1-42 and A β 1-40 and increased A β 1-37 and A β 1-38, without inhibiting overall levels of A β peptides or other APP processing intermediates. BMS-869780 also did not inhibit Notch processing by γ -secretase and lowered brain A β 1-42 without evidence of Notch-related side effects in rats. Human pharmacokinetic (PK) parameters were predicted through allometric scaling of PK in rat, dog, and monkey and were combined with the rat pharmacodynamic (PD) parameters to predict the relationship between BMS-869780 dose, exposure and A β 1-42 levels in human. Off-target and safety margins were then based on comparisons to the predicted exposure required for robust A β 1-42 lowering. Because of insufficient safety predictions and the relatively high predicted human daily dose of 700 mg, further evaluation of BMS-869780 as a potential clinical candidate was discontinued. Nevertheless, BMS-869780 demonstrates the potential of the GSM approach for robust lowering of brain A β 1-42 without Notch-related side effects.
CSF Aβ42, Tau and p181Tau are widely accepted diagnostic biomarkers of Alzheimer's disease (AD). Results from numerous studies demonstrate that CSF Tau levels are ∼2X higher in mild-to-moderate AD compared to age-matched controls. In addition, this increase in CSF Tau is detected prior to the onset of clinical symptoms, and thus is predictive of the conversion from predementia (MCI) to clinical disease. Despite the importance as a diagnostic biomarker, the molecular nature of Tau present in CSF is not known. We have employed CSF denaturation coupled with reverse-phase HPLC in order to enrich and concentrate Tau and to further characterize the CSF Tau profile. Individual fractions from pooled AD and control CSF samples were analyzed by SDS-PAGE/Western blot (WB) using various anti-Tau antibodies or by using in-house, research-grade Tau ELISAs. Multiple fragments of Tau, with apparent MW sizes ranging from ∼15 kD to 40 kD, were identified by WB using an antibody that recognizes the mid-domain of Tau, but not an isotype control IgG. A subset of these bands was recognized using an antibody specific for the N-terminal of Tau. In contrast, relatively low levels of C-terminal-containing fragments were detected as demonstrated using a C-terminal specific antibody. Tau ELISA results confirmed the WB data and demonstrated that differences in Tau levels between AD and control CSF are more prominent in specific fractions, corresponding to certain apparent molecular weight Tau fragments. Our results demonstrate the existence of multiple Tau fragments in CSF and suggest that a subset of these fragments are increased in AD CSF. These particular Tau fragments may have utility as disease and/or pharmacodynamic biomarkers.
Accumulation of amyloid-β (Aβ) peptide in the brain is thought to play a key pathological role in Alzheimer's disease. Many pharmacological targets have therefore been proposed based upon the biochemistry of Aβ, but not all are equally tractable for drug discovery.To search for novel targets that affect brain Aβ without causing toxicity, we screened mouse brain samples from 1930 novel gene knock-out (KO) strains, representing 1926 genes, using Aβ ELISA assays. Although robust Aβ lowering was readily apparent in brains from a BACE1 KO strain, none of the novel strains exhibited robust decreases in brain Aβ, including a GPR3 KO strain, which had previously been proposed as an Aβ target. However, significantly increased Aβ was observed in brain samples from two KO strains, corresponding to genes encoding the glycosylphosphatidylinositol mannosyl transferase PIGZ and quinolinate phosphoribosyltransferase (QPRT).Thus, gene ablations that are permissive for mouse survival and that also have a robust effect on Aβ levels in the brain are rare.
Levels of tau in cerebrospinal fluid (CSF) are elevated in Alzheimer's disease (AD) patients. It is believed this elevation is related to the tau pathology and neurodegeneration observed in AD, but not all tauopathies have increased CSF tau. There has been little pre-clinical work to investigate me chanisms of increased CSF tau due to the difficulty in collecting CSF samples from mice, the most commonly used pre-clinical models. We developed methods to collect CSF from mice without contamination from tau in brain tissue, which is approximately 50,000 fold more abundant in brain than CSF. Using these methods, we measured CSF tau from 3xTg, Tg4510, and Tau Alone transgenic mice. All three lines of mice showed age-dependent increases in CSF tau. They varied in phenotype from undetectable to severe tau pathology and neurodegeneration, suggesting that degenerating neurons are unlikely to be the only source of pathologic CSF tau. Overall, CSF tau levels mirrored expression levels and changes of tau in the brain, but they did not always correlate exactly. CSF tau was often more sensitive to changes in brain transgene expression and pathology. In addition, we also developed ELISA assays specific to different regions of the tau protein. We used these assays to provide evidence that CSF tau exists as fragments, with little intact C-terminus and partial loss of the N-terminus. Taken together, these assays and mouse models may be used to facilitate a deeper understanding of CSF tau in neurodegenerative disease.
A hallmark of Alzheimer's disease (AD) pathology is the accumulation of brain amyloid β-peptide (Aβ), generated by γ-secretase-mediated cleavage of the amyloid precursor protein (APP). Therefore, γ-secretase inhibitors (GSIs) may lower brain Aβ and offer a potential new approach to treat AD. As γ-secretase also cleaves Notch proteins, GSIs can have undesirable effects due to interference with Notch signaling. Avagacestat (BMS-708163) is a GSI developed for selective inhibition of APP over Notch cleavage. Avagacestat inhibition of APP and Notch cleavage was evaluated in cell culture by measuring levels of Aβ and human Notch proteins. In rats, dogs, and humans, selectivity was evaluated by measuring plasma blood concentrations in relation to effects on cerebrospinal fluid (CSF) Aβ levels and Notch-related toxicities. Measurements of Notch-related toxicity included goblet cell metaplasia in the gut, marginal-zone depletion in the spleen, reductions in B cells, and changes in expression of the Notch-regulated hairy and enhancer of split homolog-1 from blood cells. In rats and dogs, acute administration of avagacestat robustly reduced CSF Aβ40 and Aβ42 levels similarly. Chronic administration in rats and dogs, and 28-day, single- and multiple-ascending–dose administration in healthy human subjects caused similar exposure-dependent reductions in CSF Aβ40. Consistent with the 137-fold selectivity measured in cell culture, we identified doses of avagacestat that reduce CSF Aβ levels without causing Notch-related toxicities. Our results demonstrate the selectivity of avagacestat for APP over Notch cleavage, supporting further evaluation of avagacestat for AD therapy.
