A structure- and property-based drug design approach was employed to identify aminooxazoline xanthenes as potent and selective human β-secretase inhibitors. These compounds exhibited good isolated enzyme, cell potency, and selectivity against the structurally related aspartyl protease cathepsin D. Our efforts resulted in the identification of a potent, orally bioavailable CNS penetrant compound that exhibited in vivo efficacy. A single oral dose of compound 11a resulted in a significant reduction of CNS Aβ40 in naive rats.

The optimization of a series of aminooxazoline xanthene inhibitors of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is described. An early lead compound showed robust Aβ lowering activity in a rat pharmacodynamic model, but advancement was precluded by a low therapeutic window to QTc prolongation in cardiovascular models consistent with in vitro activity on the hERG ion channel. While the introduction of polar groups was effective in reducing hERG binding affinity, this came at the expense of higher than desired Pgp-mediated efflux. A balance of low Pgp efflux and hERG activity was achieved by lowering the polar surface area of the P3 substituent while retaining polarity in the P2' side chain. The introduction of a fluorine in position 4 of the xanthene ring improved BACE1 potency (5-10-fold). The combination of these optimized fragments resulted in identification of compound 40, which showed robust Aβ reduction in a rat pharmacodynamic model (78% Aβ reduction in CSF at 10 mg/kg po) and also showed acceptable cardiovascular safety in vivo.

The therapeutic use of Abs in cancer, autoimmunity, transplantation, and other fields is among the major biopharmaceutical advances of the 20th century. Broader use of Ab-based drugs is constrained because of their high production costs and frequent side effects. One promising approach to overcome these limitations is the use of highly diluted Abs, which are produced by gradual reduction of an Ab concentration to an extremely low level. This technology was used to create a group of drugs for the treatment of various diseases, depending on the specificity of the used Abs. Highly diluted Abs to IFN-g (hd-anti-IFN-g) have been demonstrated to be efficacious against influenza and other respiratory infections in a variety of preclinical and clinical studies. In the current study, we provide evidence for a possible mechanism of action of hd-anti-IFN-g. Using high-resolution solution nuclear magnetic resonance spectroscopy, we show that the drug induced conformational changes in the IFN-g molecule. Chemical shift changes occurred in the amino acids located primarily at the dimer interface and at the C-terminal region of IFN-g. These molecular changes could be crucial for the function of the protein, as evidenced by an observed hd-anti-IFN-g-induced increase in the specific binding of IFN-g to its receptor in U937 cells, enhanced induced production of IFN-g in human PBMC culture, and increased survival of influenza A-infected mice.

We have previously shown that the aminooxazoline xanthene scaffold can generate potent and orally efficacious BACE1 inhibitors although certain of these compounds exhibited potential hERG liabilities. In this article, we describe 4-aza substitution on the xanthene core as a means to increase BACE1 potency while reducing hERG binding affinity. Further optimization of the P3 and P2' side chains resulted in the identification of 42 (AMG-8718), a compound with a balanced profile of BACE1 potency, hERG binding affinity, and Pgp recognition. This compound produced robust and sustained reductions of CSF and brain Aβ levels in a rat pharmacodynamic model and exhibited significantly reduced potential for QTc elongation in a cardiovascular safety model.

BACE1 inhibition to prevent Aβ peptide formation is considered to be a potential route to a diseasemodifying treatment for Alzheimer's disease. Previous efforts in our laboratory using a combined structure-and propertybased approach have resulted in the identification of aminooxazoline xanthenes as potent BACE1 inhibitors. Herein, we report further optimization leading to the discovery of inhibitor 15 as an orally available and highly efficacious BACE1 inhibitor that robustly reduces CSF and brain Aβ levels in both rats and nonhuman primates. In addition, compound 15 exhibited low activity on the hERG ion channel and was well tolerated in an integrated cardiovascular safety model. KEYWORDS: β-site amyloid precursor protein cleaving enzyme 1 (BACE1), Alzheimer's disease (AD), Aβ, aminooxazoline, xanthene A lzheimer's disease (AD) is the most common neurodegenerative disorder and accounts for 50−80% of dementia cases identified each year. Current therapeutics for AD only provide temporary symptomatic relief and do not address the underlying neuropathology. A therapeutic treatment that directly modifies the progression of the disease remains one of the largest unmet medical needs in neurobiology.The most widely held hypothesis for the underlying pathogenesis of AD posits that aggregation of β-amyloid peptides (Aβ) and deposition into amyloid plaques in the neural parenchyma play an essential role. Aβ is produced by sequential endoproteolytic cleavage of amyloid precursor protein (APP) by the aspartyl protease β-site APP cleaving enzyme-1 (BACE1) and γ-secretase.