Development of a novel ß-secretase binding assay using the AlphaScreen platform.

Alzheimer's disease (AD) is a devastating neurodegenerative disease affecting millions of people. ß-secretase-1 (BACE1), an enzyme involved in the processing of the amyloid precursor protein (APP) to form Aß is a validated target for AD. Herein, the authors develop and validate a novel binding assay for BACE1 using the AlphaScreen platform that is amenable for high-throughput screening (HTS). Small-molecule BACE1 inhibitors of the hydroxyethylamine, hydantoin, and sulfamide classes were functionalized by biotin PEG linkers of varying lengths forming probes that were bound to streptavidin donor beads. BACE1 was coupled to nickel-chelate acceptor beads. Upon mixing, probes designed from all three classes registered high signal-to-background values in the AlphaScreen binding assay, where the interaction between probe and BACE1 was completely blocked by free parent compound. A probe from the hydantoin class was chosen for further optimization, where the final assay conditions of 50 nM BACE and 250 nM probe were used and Z(') values >0.75 were commonly observed. IC50 values determined by the AlphaScreen assay format exhibited ~10-fold greater sensitivity when compared with a fluorescence polarization-based activity assay. The assay was miniaturized to a 1536-well format for HTS, in which 525 000 compounds were screened.

Discovery of a novel [3.2.1] benzo fused bicyclic sulfonamide-pyrazoles as potent, selective and efficacious γ-secretase inhibitors.

Structure-activity relationship (SAR) of a novel, potent and metabolically stable series of benzo [3.2.1] bicyclic sulfonamide-pyrazoles as γ-secretase inhibitors are described. Compounds that are efficacious in reducing the cortical Aßx-40 levels in FVB mice via oral dose, as well as those with high selectivity over Notch, are highlighted.

Design of an orally efficacious hydroxyethylamine (HEA) BACE-1 inhibitor in a preclinical animal model.

In this Letter, we describe our efforts to design HEA BACE-1 inhibitors that are highly permeable coupled with negligible levels of permeability-glycoprotein activity. These efforts culminate in producing 16 which lowers Αß by 28% and 32% in the cortex and CSF, respectively, in the preclinical wild type Hartley guinea pig animal model when dosed orally at 30mpk BID for 2.5days.

Design and synthesis of cell potent BACE-1 inhibitors: structure-activity relationship of P1' substituents.

Using structure-guided design, hydroxyethylamine BACE-1 inhibitors were optimized to nanomolar Abeta cellular inhibition with selectivity against cathepsin-D. X-ray crystallography illuminated the S1' residues critical to this effort, which culminated in compounds 56 and 57 that exhibited potency and selectivity but poor permeability and high P-gp efflux.

Preparation and optimization of a series of 3-carboxamido-5-phenacylaminopyrazole bradykinin B1 receptor antagonists.

The B1 receptor is an attractive target for the treatment of pain and inflammation. A series of 3-carboxamido-5-phenacylamino pyrazole B1 receptor antagonists are described that exhibit good potency against B1 and high selectivity over B2. Initially, N-unsubstituted pyrazoles were studied, but these compounds suffered from extensive glucuronidation in primates. This difficulty could be surmounted by the use of N-substituted pyrazoles. Optimization efforts culminated in compound 41, which has high receptor potency and metabolic stability.

Optimizing phenylethylphosphonamidates for the inhibition of prostate-specific membrane antigen.

A series of eight N-2-phenylethylphosphonyl derivatives of glutamic acid was prepared to determine if the inhibitory potency of a phenylethylphosphonyl derivative of glutamic acid against prostate-specific membrane antigen (PSMA) could be improved through rational substitutions on the phenyl ring. The design of these eight analogs was based upon the Topliss batchwise approach. Of the inhibitors from the first generation, the 3,4-dichlorophenyl analog exhibited the greatest improvement over the lead compound which was an unsubstituted phenyl derivative, while the 4-methoxyphenyl analog was essentially void of inhibitory potency against PSMA in single-dose studies. From the potency ranking order of the first generation, the parameter most important to the pharmacophore was determined to be pi + sigma. Attempts to optimize further the potency of inhibitors by preparing a second generation of compounds did not result in structures with greater potency than that of the 3,4-dichlorophenyl analog from the first generation. Based upon K(i) values, the 3,4-dichlorophenyl analog represented a potency improvement of nearly one order of magnitude. These results confirm further the usefulness of the Topliss approach to analog development when large library synthesis cannot be achieved readily.

A series of C-terminal amino alcohol dipeptide A beta inhibitors.

Potent, small molecule A beta inhibitors have been prepared that incorporate an alanine core bracketed by an N-terminal arylacetyl group and various C-terminal amino alcohols. The compounds exhibit stereospecific inhibition as demonstrated in an in vitro assay.