Discovery of Imidazo[1,2-a]pyridine Ethers and Squaramides as Selective and Potent Inhibitors of Mycobacterial Adenosine Triphosphate (ATP) Synthesis.

The approval of bedaquiline to treat tuberculosis has validated adenosine triphosphate (ATP) synthase as an attractive target to kill Mycobacterium tuberculosis (Mtb). Herein, we report the discovery of two diverse lead series imidazo[1,2-a]pyridine ethers (IPE) and squaramides (SQA) as inhibitors of mycobacterial ATP synthesis. Through medicinal chemistry exploration, we established a robust structure-activity relationship of these two scaffolds, resulting in nanomolar potencies in an ATP synthesis inhibition assay.

Evaluation of the metabolism, bioactivation and pharmacokinetics of triaminopyrimidine analogs toward selection of a potential candidate for antimalarial therapy.

1. During the course of metabolic profiling of lead Compound 1, glutathione (GSH) conjugates were detected in rat bile, suggesting the formation of reactive intermediate precursor(s). This was confirmed by the identification of GSH and N-acetylcysteine (NAC) conjugates in microsomal incubations.

In silico-based high-throughput screen for discovery of novel combinations for tuberculosis treatment.

There are currently 18 drug classes for the treatment of tuberculosis, including those in the development pipeline. An in silico simulation enabled combing the innumerably large search space to derive multidrug combinations. Through the use of ordinary differential equations (ODE), we constructed an in silico kinetic platform in which the major metabolic pathways in Mycobacterium tuberculosis and the mechanisms of the antituberculosis drugs were integrated into a virtual proteome.

Triaminopyrimidine is a fast-killing and long-acting antimalarial clinical candidate.

The widespread emergence of Plasmodium falciparum (Pf) strains resistant to frontline agents has fuelled the search for fast-acting agents with novel mechanism of action. Here, we report the discovery and optimization of novel antimalarial compounds, the triaminopyrimidines (TAPs), which emerged from a phenotypic screen against the blood stages of Pf. The clinical candidate (compound 12) is efficacious in a mouse model of Pf malaria with an ED99 <30 mg kg(-1) and displays good in vivo safety margins in guinea pigs and rats.

N-aryl-2-aminobenzimidazoles: novel, efficacious, antimalarial lead compounds.

From the phenotypic screening of the AstraZeneca corporate compound collection, N-aryl-2-aminobenzimidazoles have emerged as novel hits against the asexual blood stage of Plasmodium falciparum (Pf). Medicinal chemistry optimization of the potency against Pf and ADME properties resulted in the identification of 12 as a lead molecule. Compound 12 was efficacious in the P.

1,4-azaindole, a potential drug candidate for treatment of tuberculosis.

New therapeutic strategies against multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis are urgently required to combat the global tuberculosis (TB) threat. Toward this end, we previously reported the identification of 1,4-azaindoles, a promising class of compounds with potent antitubercular activity through noncovalent inhibition of decaprenylphosphoryl-β-D-ribose 2'-epimerase (DprE1). Further, this series was optimized to improve its physicochemical properties and pharmacokinetics in mice.

Aminoazabenzimidazoles, a novel class of orally active antimalarial agents.

Whole-cell high-throughput screening of the AstraZeneca compound library against the asexual blood stage of Plasmodium falciparum (Pf) led to the identification of amino imidazoles, a robust starting point for initiating a hit-to-lead medicinal chemistry effort. Structure-activity relationship studies followed by pharmacokinetics optimization resulted in the identification of 23 as an attractive lead with good oral bioavailability. Compound 23 was found to be efficacious (ED90 of 28.

Lead optimization of 1,4-azaindoles as antimycobacterial agents.

In a previous report, we described the discovery of 1,4-azaindoles, a chemical series with excellent in vitro and in vivo antimycobacterial potency through noncovalent inhibition of decaprenylphosphoryl-β-d-ribose-2'-epimerase (DprE1). Nevertheless, high mouse metabolic turnover and phosphodiesterase 6 (PDE6) off-target activity limited its advancement. Herein, we report lead optimization of this series, culminating in potent, metabolically stable compounds that have a robust pharmacokinetic profile without any PDE6 liability.

4-aminoquinolone piperidine amides: noncovalent inhibitors of DprE1 with long residence time and potent antimycobacterial activity.

4-Aminoquinolone piperidine amides (AQs) were identified as a novel scaffold starting from a whole cell screen, with potent cidality on Mycobacterium tuberculosis (Mtb). Evaluation of the minimum inhibitory concentrations, followed by whole genome sequencing of mutants raised against AQs, identified decaprenylphosphoryl-β-d-ribose 2'-epimerase (DprE1) as the primary target responsible for the antitubercular activity. Mass spectrometry and enzyme kinetic studies indicated that AQs are noncovalent, reversible inhibitors of DprE1 with slow on rates and long residence times of ∼100 min on the enzyme.

In-vivo rat striatal 5-HT4 receptor occupancy using non-radiolabelled SB207145.

Objectives: The objective of the current investigation was to develop a simple, rapid method for determining in-vivo 5-hydroxytryptamine type 4 receptor (5-HT4 R) occupancy in rat brain using non-radiolabelled SB207145 as a tracer for accelerating the drug discovery process.

Methods: In-vivo tracer optimization studies for tracer dose, survival intervals and brain distribution profile were carried out in rats. The tracer was pharmacologically validated using potent well-characterized 5-HT4 R ligands.

Aripiprazole in an animal model of chronic alcohol consumption and dopamine D₂ receptor occupancy in rats.

Background: Epidemiologic studies and clinical assessment of schizophrenic population have revealed a high incidence of overlap between schizophrenia and addictive disorders.

Objective: The aim of the present investigation was to study the effect of aripiprazole in a preclinical animal model of chronic alcohol self-administration (CASA) and also to evaluate the influence of CASA on plasma pharmacokinetics and dopamine D₂ receptor (D₂R) occupancy in rats.

Methods: The effect of oral administration of aripiprazole (1, 3, and 10 mg/kg) on 4% alcohol intake in CASA was studied for a period of 45 min after a post-dosing interval of 60 min.

Approach to reduce the non-specific binding in microdialysis.

Measurement of unbound test compound concentrations at the biophase is routinely carried out in the drug discovery. Microdialysis is an established sampling technique for in vivo measurement of endogenous and exogenous compounds and it is commonly used for monitoring true concentrations. Endogenous compounds like neurotransmitters and neuropeptides in the brain are routinely evaluated as a proof of pharmacological activity of test compounds.

Pharmacokinetic profiling of efavirenz-emtricitabine-tenofovir fixed dose combination in pregnant and non-pregnant rats.

During pregnancy, the disposition of various drugs is altered due to changes in physiological condition, maternal gastrointestinal absorption, gastric secretion and motility. A fixed dose combination of antiretrovirals is commonly prescribed for the treatment of HIV infection. There is a need to understand the pharmacokinetics and placental transfer of efavirenz-emtricitabine-tenofovir in fixed dose combination during pregnancy.

Methyllycaconitine: a non-radiolabeled ligand for mapping α7 neuronal nicotinic acetylcholine receptors - in vivo target localization and biodistribution in rat brain.

Introduction: Reduction of cerebral cortical and hippocampal α7 neuronal nicotinic acetylcholine receptor (nAChR) density was observed in the Alzheimer's disease (AD) and other neurodegenerative diseases. Mapping the subtypes of nAChRs with selective ligand by viable, quick and consistent method in preclinical drug discovery may lead to rapid development of more effective therapeutic agents. The objective of this study was to evaluate the use of methyllycaconitine (MLA) in non-radiolabeled form for mapping α7 nAChRs in rat brain.

Rat thalamic α₄β₂ neuronal nicotinic acetylcholine receptor occupancy assay using LC-MS/MS.

Introduction: In vivo brain receptor occupancy has been the key assay in driving preclinical drug discovery program and there is a need to hasten this screening step. Radiolabeled methods, which are time consuming and expensive, are most widely employed to measure receptor occupancy. Thus we sought to develop and validate an alternative novel approach for measuring rat brain α₄β₂ neuronal nicotinic acetylcholine receptor occupancy using high performance liquid chromatography combined with tandem mass spectrometric detector (LC-MS/MS).

In vivo receptor occupancy assay of histamine H₃ receptor antagonist in rats using non-radiolabeled tracer.

Introduction: Rapid and reliable preclinical receptor occupancy measurement at the target organ in relevant species is critical in accelerating the drug hunting process. The aim of this study was to develop in vivo receptor occupancy assay for histamine H₃ receptors (H₃R) using the non-radiolabeled GSK189254 as a tracer and to correlate the occupancy-exposure relationship for H₃R antagonists in the rats.

Methods: In vivo tracer characterization studies like brain regional distribution, dose and time dependent uptake were carried out for GSK189254 in the male Wistar rats after intravenous administration.

Concurrent administration of atypical antipsychotics and donepezil: drug interaction study in rats.

Psychotic and behavioral symptoms are common in patients with dementia. Thus, it is rational to assume that patients with dementia would gain benefit from combination therapy of an antipsychotic agent and a cognitive enhancer. Antipsychotics are not approved by the US FDA in elderly patients with dementia but their use is still prevalent in other population.

A simple and rapid method to collect the cerebrospinal fluid of rats and its application for the assessment of drug penetration into the central nervous system.

Many central nervous system (CNS) drug discovery programs require the successful collection of cerebrospinal fluid (CSF) for assessing CNS penetration and distribution of new chemical entities. The objective of the present investigation was to simplify the technique for collecting maximum CSF from cisterna magna of the rats. Rat was anesthetized with 5% halothane and positioned in a stereotaxic frame.