Rapid Evolution of a Fragment-like Molecule to Pan-Metallo-Beta-Lactamase Inhibitors: Initial Leads toward Clinical Candidates.

With the emergence and rapid spreading of NDM-1 and existence of clinically relevant VIM-1 and IMP-1, discovery of pan inhibitors targeting metallo-beta-lactamases (MBLs) became critical in our battle against bacterial infection. Concurrent with our fragment and high-throughput screenings, we performed a knowledge-based search of known metallo-beta-lactamase inhibitors (MBLIs) to identify starting points for early engagement of medicinal chemistry. A class of compounds exemplified by , discovered earlier as metallo-beta-lactamase inhibitors, was selected for virtual screening.

The discovery of fused oxadiazepines as gamma secretase modulators for treatment of Alzheimer's disease.

In an attempt to further improve overall profiles of the oxadiazine series of GSMs, in particular the hERG activity, conformational modifications of the core structure resulted in the identification of fused oxadiazepines such as 7i which had an improved hERG inhibition profile and was a highly efficacious GSM in vitro and in vivo in rats. These SAR explorations offer opportunities to identify potential drugs to treat Alzheimer's disease.

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.

Cyclic hydroxyamidines as amide isosteres: discovery of oxadiazolines and oxadiazines as potent and highly efficacious γ-secretase modulators in vivo.

Cyclic hydroxyamidines were designed and validated as isosteric replacements of the amide functionality. Compounds with these structural motifs were found to be metabolically stable and to possess highly desirable pharmacokinetic profiles. These designs were applied in the identification of γ-secretase modulators leading to highly efficacious agents for reduction of central nervous system Aβ(42) in various animal models.

Iminoheterocycles as gamma-secretase modulators.

The synthesis of a novel series of iminoheterocycles and their structure-activity relationship (SAR) as modulators of gamma-secretase activity will be detailed. Encouraging SAR generated from a monocyclic core led to a structurally unique bicyclic core. Selected compounds exhibit good potency as gamma-secretase modulators, excellent rat pharmacokinetics, and lowering of Abeta42 levels in various in vivo models.

The Discovery of Pyridone and Pyridazone Heterocycles as γ-Secretase Modulators.

A series of novel pyridazone and pyridone compounds as γ-secretase modulators were discovered. Starting from the initial lead, structure-activity relationship studies were carried out in which an internal hydrogen bond was introduced to conformationally fix the side chain, and compounds with improved in vitro Aβ42 inhibition activity and good Aβtotal/Aβ42 selectivity were quickly discovered. Compound 35 displayed very good in vitro activity and excellent selectivity with good in vivo efficacy in both CRND8 mouse and nontransgenic rat models.

Protein binding-dependent decreases in hERG channel blocker potency assessed by whole-cell voltage clamp in serum.

In vitro hERG blocking potency is measured in drug discovery as part of an integrated cardiovascular risk assessment. Typically, the concentrations producing 50% inhibition are measured in protein-free saline solutions and compared with calculated free therapeutic in vivo Cmax values to estimate a hERG safety multiple. The free/unbound fraction is believed responsible for activity.

The impact of protein on Caco-2 permeability of low mass balance compounds for absorption projection and efflux substrate identification.

This study was to evaluate the mechanistic effect of protein to help better interpret the permeability results for compounds with low mass balance in Caco-2 permeability assay. The absorptive or bi-directional permeability of lipophilic compounds with mass balance were measured across Caco-2 cell monolayers as well as the empty transport devices with or without protein (4% bovine serum albumin, BSA) added to the receiver side. The results from empty transport device study indicated that the filter membrane is a permeability barrier for the low mass balance compounds and protein increases permeability by improving the compound diffusivity through the filter membrane.

Temporal evaluation of CYP mRNA in mice administered with prototypical P450 inducers: comparison with conventional protein/enzyme methods.

Assessment of cytochrome P450 (CYP) induction at the mRNA level in preclinical rodent studies has gained interest in recent years, but there are still concerns regarding correlations between the mRNA and the enzyme activity levels, especially in mice. The purpose of the present study was to systematically evaluate patterns of temporal changes of CYPs 1a1, 1a2, 2b10, 3a11, and 4a10 at mRNA, protein, and activity levels in order to determine to what extent mRNA levels could be used either qualitatively or quantitatively for the assessment of CYP enzyme induction. In this study, livers from male CD-1 mice treated daily with beta-naphthoflavone, phenobarbital, dexamethasone, clofibrate, and control vehicles were collected for RNA and microsomal analysis after 0.

Discovery of amide and heteroaryl isosteres as carbamate replacements in a series of orally active gamma-secretase inhibitors.

The design of amide and heteroaryl amide isosteres as replacements for the carbamate substructure in previously disclosed 2,6-disubstituted piperidine N-arylsulfonamides is described. In several cases, amides lessened CYP liabilities in this class of gamma-secretase inhibitors. Selected compounds showed significant reduction of Abeta levels upon oral dosing in a transgenic murine model of Alzheimer's disease.

Utility of mass spectrometry for in-vitro ADME assays.

A balance between pharmacological activity, safety and drug metabolism and pharmacokinetics (DMPK) attributes determines the fate of a new chemical entity (NCE) in drug discovery. Because of the increased number of NCEs requiring DMPK evaluation, several in vitro higher-throughput screens and counter screens designed to evaluate DMPK attributes have been introduced in drug discovery. The DMPK screens evaluate NCEs for potential absorption, metabolism, drug-drug interactions, brain penetration, protein binding and pharmacokinetics.

Blocking ion channel KCNN4 alleviates the symptoms of experimental autoimmune encephalomyelitis in mice.

The KCNN4 potassium-ion channel has been reported to play an important role in regulating antigen-induced T cell effector functions in vitro. This study presents the first evidence that a selective KCNN4 blocker, TRAM-34, confers protection against experimental autoimmune encephalomyelitis (EAE) in the mouse model. Treatment with the KCNN4 blocker did not prevent infiltration of T cells in the spinal cord, but resulted in the reduction of both the protein and the message levels of TNF-alpha and IFN-gamma as well as the message levels of several other pro-inflammatory molecules in the spinal cord.

A computer program for automated data evaluation to support in vitro higher-throughput screening for drug metabolism and pharmacokinetics attributes.

With the advances in analytical techniques, higher-throughput screening for drug metabolism and pharmacokinetics (DMPK) attributes has become an integral part of drug discovery. However, as the number of compounds increases, the volume of data that needs to be processed and evaluated increases exponentially. As a result, a major challenge for the analytical chemist is how to quickly process the vast amount of data so as to keep up with the throughput of the screening assay.

Assessment of temporal biochemical and gene transcription changes in rat liver cytochrome P450: utility of real-time quantitative RT-PCR.

Purpose: A conventional approach to assess cytochrome P450 (CYP) induction in preclinical animal models involves daily dosing for a least a week followed by Western blot and/or enzyme activity analysis. To evaluate the potential benefit of a third more specific and sensitive assay, real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), with the objective of reducing the duration of the conventional 1-week study, we simultaneously assessed gene expression by qRT-PCR along with Western blots and enzyme activity assays as a time course in an in vivo model.

Methods: Rats were dosed daily for 8 days with model inducers of CYP1A, CYP2B, CYP3A, or CYP4A.

Higher-throughput screening for Caco-2 permeability utilizing a multiple sprayer liquid chromatography/tandem mass spectrometry system.

In the current drug discovery environment, higher-throughput analytical assays have become essential to keep pace with the screening demands for drug metabolism and pharmacokinetics (DMPK) attributes. This has been dictated by advances primarily in chemical procedures, notably combinatorial and parallel syntheses, which has resulted in many-fold increases in the number of compounds requiring DMPK evaluation. Because of its speed and specificity, liquid chromatography/tandem mass spectrometry (LC/MS/MS) has become the dominant technology for sample analysis in the DMPK screening assays.

A fully automated nanoelectrospray tandem mass spectrometric method for analysis of Caco-2 samples.

Caco-2 cells offer a means to rapidly screen permeability of drug candidates, allowing pharmaceutical companies to eliminate candidates unable to cross the intestinal barrier early in the discovery process. This screening process is typically performed by conventional liquid chromatography/tandem mass spectrometry (LC/MS/MS), which can require time-consuming method development. An alternative to LC/MS/MS, automated nanoelectrospray tandem mass spectrometry (nanoESI-MS/MS), is introduced.

The use of in vitro metabolic stability for rapid selection of compounds in early discovery based on their expected hepatic extraction ratios.

Purpose: The in vivo hepatic extraction ratio of cynomolgus monkeys was correlated with the corresponding in vitro extraction ratios that were determined in monkey microsomal incubations.

Method: For compounds that are eliminated mainly through liver phase I metabolism, the extraction ratio calculated from liver microsomal stability studies should correlate with their in vivo hepatic extraction ratios and also with their oral bioavailability in monkey. We used both well-stirred and parallel tube models of intrinsic clearance for the correlation.

Generic fast gradient liquid chromatography/tandem mass spectrometry techniques for the assessment of the in vitro permeability across the blood-brain barrier in drug discovery.

Rapid, generic gradient liquid chromatography/tandem mass spectrometry (LC/MS/MS) assays, designed to accelerate sample analyses, have been developed to keep pace with the productivity of advanced synthetic procedures. In this study, LC/MS/MS was combined with an in vitro, cell-based, blood-brain barrier (BBB) model to evaluate the potential of new chemical entities (NCEs) to cross the BBB. This in vitro assay provides the permeability of discovery compounds across a monolayer of a primary culture of bovine brain microvessel endothelial cells in a fraction of the time that is required for in vivo studies (brain/plasma concentrations), using only 2 mg of the compound.