Discovery of fused 5,6-bicyclic heterocycles as γ-secretase modulators

Characterizing the Chemical Space of γ-Secretase Inhibitors and Modulators

γ-Secretase (GS) is one of the most attractive molecular targets for the treatment of Alzheimer's disease (AD). Its key role in the final step of amyloid-β peptides generation and its relationship in the cascade of events for disease development have caught the attention of many pharmaceutical groups. Over the past years, different inhibitors and modulators have been evaluated as promising therapeutics against AD. However, despite the great chemical diversity of the reported compounds, a global classification and visual representation of the chemical space for GS inhibitors and modulators remain unavailable. In the present work, we carried out a two-dimensional (2D) chemical space analysis from different classes and subclasses of GS inhibitors and modulators based on their structural similarity. Along with the novel structural information available for GS complexes, our analysis opens the possibility to identify compounds with high molecular similarity, critical to finding new chemical structures through the optimization of existing compounds and relating them with a potential binding site.

Copper-Catalyzed Asymmetric Arylation of N-Heteroaryl Aldimines: Elementary Step of a 1,4-Insertion

Copper complexes of monodentate phosphoramidites efficiently promote asymmetric arylation of N-azaaryl aldimines with arylboroxines. DFT calculations and experiments support an elementary step of 1,4-insertion in the reaction pathway, a step in which an aryl-copper species adds directly across four atoms of C=N-C=N in the N-azaaryl aldimines.

Discovery of a Tetrahydrobenzisoxazole Series of γ-Secretase Modulators

The design and synthesis of a new series of tetrahydrobenzisoxazoles as modulators of γ-secretase activity and their structure-activity relationship (SAR) will be detailed. Several compounds are active γ-secretase modulators (GSMs) with good to excellent selectivity for the reduction of Aβ₄₂ in the cellular assay. Compound 14a was tested in vivo in a nontransgenic rat model and was found to significantly reduce Aβ₄₂ in the CNS compartment compared to vehicle-treated animals (up to 58% reduction of cerebrospinal fluid Aβ₄₂ as measured 3 h after an acute oral dosing at 30 mg/kg).

Electronically modified amine substituted alkynols for regio-selective synthesis of dihydrofuran derivatives

An efficient approach has been developed for the regio-selective synthesis of iodo-dihydrofurans from amino alkynols. These dihydrofurans have been further diversified by C–C, C–N coupling reactions.

Cinnamamide Derivatives for Central and Peripheral Nervous System Disorders--A Review of Structure-Activity Relationships

The cinnamamide scaffold has been incorporated in to the structure of numerous organic compounds with therapeutic potential. The scaffold enables multiple interactions, such as hydrophobic, dipolar, and hydrogen bonding, with important molecular targets. Additionally, the scaffold has multiple substitution options providing the opportunity to optimize and modify the pharmacological activity of the derivatives. In particular, cinnamamide derivatives have exhibited therapeutic potential in animal models of both central and peripheral nervous system disorders. Some have undergone clinical trials and were introduced on to the pharmaceutical market. The diverse activities observed in the nervous system included anticonvulsant, antidepressant, neuroprotective, analgesic, anti-inflammatory, muscle relaxant, and sedative properties. Over the last decade, research has focused on the molecular mechanisms of action of these derivatives, and the data reported in the literature include targeting the γ-aminobutyric acid type A (GABAA ) receptors, N-methyl-D-aspartate (NMDA) receptors, transient receptor potential (TRP) cation channels, voltage-gated potassium channels, histone deacetylases (HDACs), prostanoid receptors, opioid receptors, and histamine H3 receptors. Here, the literature data from reports evaluating cinnamic acid amide derivatives for activity in target-based or phenotypic assays, both in vivo and in vitro, relevant to disorders of the central and peripheral nervous systems are analyzed and structure-activity relationships discussed.

γ-Secretase modulators: current status and future directions

This chapter reviews the current status of γ-secretase modulators, highlighting key compounds by each company involved in the area. The review focuses on the three main chemotypes: acids, imidazoles and related derivatives and natural products. A section on chemical biology and ligand-binding site elucidation studies is also included. The primary source of information is drawn from peer reviewed literature as this permits analysis of PK-PD relationships and subsequent comment. Discussion of the patent literature is included for completeness. From this analysis, the key issues and challenges in the area are highlighted. The review concludes with a summary of the clinical development status and comment on future prospects of the field.

γ-Secretase inhibitors and modulators

γ-Secretase is a fascinating, multi-subunit, intramembrane cleaving protease that is now being considered as a therapeutic target for a number of diseases. Potent, orally bioavailable γ-secretase inhibitors (GSIs) have been developed and tested in humans with Alzheimer's disease (AD) and cancer. Preclinical studies also suggest the therapeutic potential for GSIs in other disease conditions. However, due to inherent mechanism based-toxicity of non-selective inhibition of γ-secretase, clinical development of GSIs will require empirical testing with careful evaluation of benefit versus risk. In addition to GSIs, compounds referred to as γ-secretase modulators (GSMs) remain in development as AD therapeutics. GSMs do not inhibit γ-secretase, but modulate γ-secretase processivity and thereby shift the profile of the secreted amyloid β peptides (Aβ) peptides produced. Although GSMs are thought to have an inherently safe mechanism of action, their effects on substrates other than the amyloid β protein precursor (APP) have not been extensively investigated. Herein, we will review the current state of development of GSIs and GSMs and explore pertinent biological and pharmacological questions pertaining to the use of these agents for select indications. This article is part of a Special Issue entitled: Intramembrane Proteases.

Synthesis and SAR Studies of Fused Oxadiazines as γ-Secretase Modulators for Treatment of Alzheimer's Disease

Fused oxadiazines (3) were discovered as selective and orally bioavailable γ-secretase modulators (GSMs) based on the structural framework of oxadiazoline GSMs. Although structurally related, initial modifications showed that structure-activity relationships (SARs) did not translate from the oxadiazoline to the oxadiazine series. Subsequent SAR studies on modifications at the C3 and C4 positions of the fused oxadiazine core helped to identify GSMs such as compounds 8r and 8s that were highly efficacious in vitro and in vivo in a number of animal models with highly desirable physical and pharmacological properties. Further improvements of in vitro activity and selectivity were achieved by the preparation of fused morpholine oxadiazines. The shift in specificity of APP cleavage rather than a reduction in overall γ-secretase activity and the lack of changes in substrate accumulation and Notch processing as observed in the animal studies of compound 8s confirm that the oxadiazine series of compounds are potent GSMs.

Design and synthesis of dihydrobenzofuran amides as orally bioavailable, centrally active γ-secretase modulators

We report the discovery and optimization of a novel series of dihydrobenzofuran amides as γ-secretase modulators (GSMs). Strategies for aligning in vitro potency with drug-like physicochemical properties and good microsomal stability while avoiding P-gp mediated efflux are discussed. Lead compounds such as 35 and 43 have moderate to good in vitro potency and excellent selectivity against Notch. Good oral bioavailability was achieved as well as robust brain Aβ42 lowering activity at 100 mg/kg po dose.

Discovery of a Potent Pyrazolopyridine Series of γ-Secretase Modulators

The synthesis and structure-activity relationship of a novel series of pyrazolopyridines are reported. These compounds represent a new class of γ-secretase modulators that demonstrate good in vitro potency in inhibiting Aβ42 production. Examples with statistically significant in vivo efficacy in reducing the production of rat cerebrospinal fluid Aβ42 were also identified.