Accelerating drug discovery for Alzheimer's disease: best practices for preclinical animal studies

Animal models have contributed significantly to our understanding of the underlying biological mechanisms of Alzheimer's disease (AD). As a result, over 300 interventions have been investigated and reported to mitigate pathological phenotypes or improve behavior in AD animal models or both. To date, however, very few of these findings have resulted in target validation in humans or successful translation to disease-modifying therapies. Challenges in translating preclinical studies to clinical trials include the inability of animal models to recapitulate the human disease, variations in breeding and colony maintenance, lack of standards in design, conduct and analysis of animal trials, and publication bias due to under-reporting of negative results in the scientific literature. The quality of animal model research on novel therapeutics can be improved by bringing the rigor of human clinical trials to animal studies. Research communities in several disease areas have developed recommendations for the conduct and reporting of preclinical studies in order to increase their validity, reproducibility, and predictive value. To address these issues in the AD community, the Alzheimer's Drug Discovery Foundation partnered with Charles River Discovery Services (Morrisville, NC, USA) and Cerebricon Ltd. (Kuopio, Finland) to convene an expert advisory panel of academic, industry, and government scientists to make recommendations on best practices for animal studies testing investigational AD therapies. The panel produced recommendations regarding the measurement, analysis, and reporting of relevant AD targets, th choice of animal model, quality control measures for breeding and colony maintenance, and preclinical animal study design. Major considerations to incorporate into preclinical study design include a priori hypotheses, pharmacokinetics-pharmacodynamics studies prior to proof-of-concept testing, biomarker measurements, sample size determination, and power analysis. The panel also recommended distinguishing between pilot 'exploratory' animal studies and more extensive 'therapeutic' studies to guide interpretation. Finally, the panel proposed infrastructure and resource development, such as the establishment of a public data repository in which both positive animal studies and negative ones could be reported. By promoting best practices, these recommendations can improve the methodological quality and predictive value of AD animal studies and make the translation to human clinical trials more efficient and reliable

Restricted location of PSEN2/γ-secretase determines substrate specificity and generates an intracellular Aβ pool

gamma-Secretases are a family of intramembrane-cleaving proteases involved in various signaling pathways and diseases, including Alzheimer's disease (AD). Cells co-express differing gamma-secretase complexes, including two homologous presenilins (PSENs). We examined the significance of this heterogeneity and identified a unique motif in PSEN2 that directs this gamma-secretase to late endosomes/lysosomes via a phosphorylation-dependent interaction with the AP-1 adaptor complex. Accordingly, PSEN2 selectively cleaves late endosomal/lysosomal localized substrates and generates the prominent pool of intracellular A beta that contains longer A beta; familial AD (FAD)-associated mutations in PSEN2 increased the levels of longer A beta further. Moreover, a subset of FAD mutants in PSEN1, normally more broadly distributed in the cell, phenocopies PSEN2 and shifts its localization to late endosomes/lysosomes. Thus, localization of gamma-secretases determines substrate specificity, while FAD-causing mutations strongly enhance accumulation of aggregation-prone A beta 42 in intracellular acidic compartments. The findings reveal potentially important roles for specific intracellular, localized reactions contributing to AD pathogenesis

Discovery of (<i>R</i>)‑4-Cyclopropyl-7,8-difluoro-5-(4-(trifluoromethyl)phenylsulfonyl)-4,5-dihydro‑1<i>H</i>‑pyrazolo[4,3‑<i>c</i>]quinoline (ELND006) and (<i>R</i>)‑4-Cyclopropyl-8-fluoro-5-(6-(trifluoromethyl)pyridin-3-ylsulfonyl)-4,5-dihydro‑2<i>H</i>‑pyrazolo[4,3‑<i>c</i>]quinoline (ELND007): Metabolically Stable γ‑Secretase Inhibitors that Selectively Inhibit the Production of Amyloid‑β over Notch

Herein, we describe our strategy to design metabolically stable γ-secretase inhibitors which are selective for inhibition of Aβ generation over Notch. We highlight our synthetic strategy to incorporate diversity and chirality. Compounds <b>30</b> (ELND006) and <b>34</b> (ELND007) both entered human clinical trials. The in vitro and in vivo characteristics for these two compounds are described. A comparison of inhibition of Aβ generation in vivo between <b>30</b>, <b>34</b>, Semagacestat <b>41</b>, Begacestat <b>42</b>, and Avagacestat <b>43</b> in mice is made. <b>30</b> lowered Aβ in the CSF of healthy human volunteers