Spirocyclic β-Site Amyloid Precursor Protein Cleaving Enzyme 1 (BACE1) Inhibitors: From Hit to Lowering of Cerebrospinal Fluid (CSF) Amyloid β in a Higher Species
作者:Kevin W. Hunt、Adam W. Cook、Ryan J. Watts、Christopher T. Clark、Guy Vigers、Darin Smith、Andrew T. Metcalf、Indrani W. Gunawardana、Michael Burkard、April A. Cox、Mary K. Geck Do、Darrin Dutcher、Allen A. Thomas、Sumeet Rana、Nicholas C. Kallan、Robert K. DeLisle、James P. Rizzi、Kelly Regal、Douglas Sammond、Robert Groneberg、Michael Siu、Hans Purkey、Joseph P. Lyssikatos、Allison Marlow、Xingrong Liu、Tony P. Tang
DOI:10.1021/jm4002154
日期:2013.4.25
A hallmark of Alzheimer's disease is the brain deposition of amyloid beta (A beta), a peptide of 36-43 amino acids that is likely a primary driver of neurodegeneration. A beta is produced by the sequential cleavage of APP by BACE1 and gamma-secretase; therefore, inhibition of BACE1 represents an attractive therapeutic target to slow or prevent Alzheimer's disease. Herein we describe BACE1 inhibitors with limited molecular flexibility and molecular weight that decrease CSF A beta in vivo, despite efflux. Starting with spirocycle la, we explore structure activity relationships of core changes, P3 moieties, and Asp binding functional groups in order to optimize BACE1 affinity, cathepsin D selectivity, and blood brain barrier (BBB) penetration. Using wild type guinea pig and rat, we demonstrate a PK/PD relationship between free drug concentrations in the brain and CSF A beta lowering. Optimization of brain exposure led to the discovery of (R)-50 which reduced CSF A beta in rodents and in monkey.