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The discovery of chiral amino alcohols derived from our previously disclosed clinical LTA4H inhibitor LYS006 is described. In a biochemical assay, their optical antipodes showed similar potencies, which could be rationalized by the cocrystal structures of these compounds bound to LTA4H. Despite comparable stabilities in liver microsomes, they showed distinct in vivo PK properties. Selective O -phosphorylation of the ( R )-enantiomers in blood led to clearance values above the hepatic blood flow, whereas the ( S )-enantiomers were unaffected and exhibited satisfactory metabolic stabilities in vivo. Introduction of two pyrazole rings led to compound ( S )- 2 with a more balanced distribution of polarity across the molecule, exhibiting high selectivity and excellent potency in vitro and in vivo. Furthermore, compound ( S )- 2 showed favorable profiles in 16-week IND-enabling toxicology studies in dogs and rats. Based on allometric scaling and potency in whole blood, compound ( S )- 2 has the potential for a low oral efficacious dose administered once daily.

After identification of lead compound 6 , 5-amino-1,4-oxazine BACE1 inhibitors were optimized in order to improve potency, brain penetration, and metabolic stability. Insertion of a methyl and a trifluoromethyl group at the 6-position of the 5-amino-1,4-oxazine led to 8 ( NB-360 ), an inhibitor with a p K a of 7.1, a very low P-glycoprotein efflux ratio, and excellent pharmacological profile, enabling high central nervous system penetration and exposure. Fur color changes observed with NB-360 in efficacy studies in preclinical animal models triggered further optimization of the series. Herein, we describe the steps leading to the discovery of 3-chloro-5-trifluoromethyl-pyridine-2-carboxylic acid [6-((3 R ,6 R )-5-amino-3,6-dimethyl-6-trifluoromethyl-3,6-dihydro-2 H -[1,4]oxazin-3-yl)-5-fluoro-pyridin-2-yl]amide 15 ( CNP520 , umibecestat ), an inhibitor with superior BACE1/BACE2 selectivity and pharmacokinetics. CNP520 reduced significantly Aβ levels in mice and rats in acute and chronic treatment regimens without any side effects and thus qualified for Alzheimer's disease prevention studies in the clinic.

Starting from lead compound 4 , the 1,4-oxazine headgroup was optimized to improve potency and brain penetration. Focusing at the 6-position of the 5-amino-1,4-oxazine, the insertion of a Me and a CF 3 group delivered an excellent pharmacological profile with a p K a of 7.1 and a very low P-gp efflux ratio enabling high central nervous system (CNS) penetration and exposure. Various synthetic routes to access BACE1 inhibitors bearing a 5-amino-6-methyl-6-(trifluoromethyl)-1,4-oxazine headgroup were investigated. Subsequent optimization of the P3 fragment provided the highly potent N -(3-((3 R ,6 R )-5-amino-3,6-dimethyl-6-(trifluoromethyl)-3,6-dihydro-2 H -1,4-oxazin-3-yl)-4-fluorophenyl)-5-cyano-3-methylpicolinamide 54 ( NB-360 ), able to reduce significantly A β levels in mice, rats, and dogs in acute and chronic treatment regimens.

New amino-1,4-oxazine derived BACE-1 inhibitors were explored and various synthetic routes developed. The binding mode of the inhibitors was elucidated by co-crystallization of 4 with BACE-1 and X-ray analysis. Subsequent optimization led to inhibitors with low double digit nanomolar activity in a biochemical and single digit nanomolar potency in a cellular assays. To assess the inhibitors for their permeation properties and potential to cross the blood-brain-barrier a MDR1-MDCK cell model was successfully applied. Compound 8a confirmed the in vitro results by dose-dependently reducing Aβ levels in mice in an acute treatment regimen., (Copyright © 2018. Published by Elsevier Ltd.)

Previous structure based optimization in our laboratories led to the identification of a novel, high-affinity cyclic sulfone hydroxyethylamine-derived inhibitor such as 1 that lowers CNS-derived Aβ following oral administration to transgenic APP51/16 mice. Herein we report SAR development in the S3 and S2' subsites of BACE1 for cyclic sulfoxide hydroxyethyl amine inhibitors, the synthetic approaches employed in this effort, and in vivo data for optimized compound such as 11d., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Structure-based design of a series of cyclic hydroxyethylamine BACE1 inhibitors allowed the rational incorporation of prime- and nonprime-side fragments to a central core template without any amide functionality. The core scaffold selection and the structure-activity relationship development were supported by molecular modeling studies and by X-ray analysis of BACE1 complexes with various ligands to expedite the optimization of the series. The direct extension from P1-aryl- and heteroaryl moieties into the S3 binding pocket allowed the enhancement of potency and selectivity over cathepsin D. Restraining the design and synthesis of compounds to a physicochemical property space consistent with central nervous system drugs led to inhibitors with improved blood-brain barrier permeability. Guided by structure-based optimization, we were able to obtain highly potent compounds such as 60p with enzymatic and cellular IC(50) values of 2 and 50 nM, respectively, and with >200-fold selectivity over cathepsin D. Pharmacodynamic studies in APP51/16 transgenic mice at oral doses of 180 μmol/kg demonstrated significant reduction of brain Aβ levels., (© 2012 American Chemical Society)