Supplementary Material for: Cerebrospinal Fluid β-Amyloid Turnover in the Mouse, Dog, Monkey and Human Evaluated by Systematic Quantitative Analyses

<b><i>Background:</i></b> Reducing brain β-amyloid (Aβ) via inhibition of β-secretase, or inhibition/modulation of γ-secretase, has been widely pursued as a potential disease-modifying treatment for Alzheimer's disease. Compounds that act through these mechanisms have been screened and characterized with Aβ lowering in the brain and/or cerebrospinal fluid (CSF) as the primary pharmacological end point. Interpretation and translation of the pharmacokinetic (PK)/pharmacodynamic (PD) relationship for these compounds is complicated by the relatively slow Aβ turnover process in these compartments. <b><i>Objective:</i></b> To understand Aβ turnover kinetics in preclinical species and humans. <b><i>Methods:</i></b> We collected CSF Aβ dynamic data after β- or γ-secretase inhibitor treatment from in-house experiments and the public domain, and analyzed the data using PK/PD modeling to obtain CSF Aβ turnover rates (k_out) in the mouse, dog, monkey and human. <b><i>Results:</i></b> The k_out for CSF Aβ40 follows allometry (k_out = 0.395 × body weight^-0.351). The k_out for CSF Aβ40 is approximately 2-fold higher than the turnover of CSF in rodents, but in higher species, the two are comparable. <b><i>Conclusion:</i></b> The turnover of CSF Aβ40 was systematically examined, for the first time, in multiple species through quantitative modeling of multiple data sets. Our result suggests that the clearance mechanisms for CSF Aβ in rodents may be different from those in the higher species. The understanding of Aβ turnover has considerable implications for the discovery and development of Aβ-lowering therapeutics, as illustrated from the perspectives of preclinical PK/PD characterization and preclinical-to-clinical translation

Spirocyclic Sulfamides as β‑Secretase 1 (BACE-1) Inhibitors for the Treatment of Alzheimer’s Disease: Utilization of Structure Based Drug Design, WaterMap, and CNS Penetration Studies To Identify Centrally Efficacious Inhibitors

β-Secretase 1 (BACE-1) is an attractive therapeutic target for the treatment and prevention of Alzheimer’s disease (AD). Herein, we describe the discovery of a novel class of BACE-1 inhibitors represented by sulfamide <b>14g</b>, using a medicinal chemistry strategy to optimize central nervous system (CNS) penetration by minimizing hydrogen bond donors (HBDs) and reducing P-glycoprotein (P-gp) mediated efflux. We have also taken advantage of the combination of structure based drug design (SBDD) to guide the optimization of the sulfamide analogues and the in silico tool WaterMap to explain the observed SAR. Compound <b>14g</b> is a potent inhibitor of BACE-1 with excellent permeability and a moderate P-gp liability. Administration of <b>14g</b> to mice produced a significant, dose-dependent reduction in central Aβ_X‑40 levels at a free drug exposure equivalent to the whole cell IC₅₀ (100 nM). Furthermore, studies of the P-gp knockout mouse provided evidence that efflux transporters affected the amount of Aβ lowering versus that observed in wild-type (WT) mouse at an equivalent dose