Balancing potency and basicity by incorporating fluoropyridine moieties: Discovery of a 1-amino-3,4-dihydro-2,6-naphthyridine BACE1 inhibitor that affords robust and sustained central Aβ reduction

beta-Site amyloid precursor protein cleaving enzyme 1 (BACE1) has been pursued as a prime target for the treatment of Alzheimer's disease (AD). In this report, we describe the discovery of BACE1 inhibitors with a 1-amino-3,4-dihydro-2,6-naphthyridine scaffold. Leveraging known inhibitors 2a and 2b, we designed the naphthyridine-based compounds by removing a structurally labile moiety and incorporating pyridine rings, which showed increased biochemical and cellular potency, along with reduced basicity on the amidine moiety. Introduction of a fluorine atom on the pyridine culminated in compound 11 which had improved cellular activity as well as further reduced basicity and demonstrated a robust and sustained cerebrospinal fluid (CSF) A beta reduction in dog. The crystal structure of compound 11 bound to BACE1 confirmed van der Waals interactions between the fluorine on the pyridine and Tyr71 in the flap. (C) 2021 Elsevier Masson SAS. All rights reserved.

Automated summary

This report details the discovery of BACE1 inhibitors with a 1-amino-3,4-dihydro-2,6-naphthyridine scaffold, which showed improved biochemical and cellular potency with reduced basicity. A compound with a fluorine atom on the pyridine ring demonstrated enhanced cellular activity and sustained cerebrospinal fluid A beta reduction in dog models, confirmed by crystal structure analysis.