Bedaquiline has potential for targeting tuberculosis reservoirs in the central nervous system

Predictions of Bedaquiline Central Nervous System Exposure in Patients with Tuberculosis Meningitis Using Physiologically based Pharmacokinetic Modeling

BACKGROUND AND OBJECTIVE

The use of bedaquiline as a treatment option for drug-resistant tuberculosis meningitis (TBM) is of interest to address the increased prevalence of resistance to first-line antibiotics. To this end, we describe a whole-body physiologically based pharmacokinetic (PBPK) model for bedaquiline to predict central nervous system (CNS) exposure.

METHODS

A whole-body PBPK model was developed for bedaquiline and its metabolite, M2. The model included compartments for brain and cerebrospinal fluid (CSF). Model predictions were evaluated by comparison to plasma PK time profiles following different dosing regimens and sparse CSF concentrations data from patients. Simulations were then conducted to compare CNS and lung exposures to plasma exposure at clinically relevant dosing schedules.

RESULTS

The model appropriately described the observed plasma and CSF bedaquiline and M2 concentrations from patients with pulmonary tuberculosis (TB). The model predicted a high impact of tissue binding on target site drug concentrations in CNS. Predicted unbound exposures within brain interstitial exposures were comparable with unbound vascular plasma and unbound lung exposures. However, unbound brain intracellular exposures were predicted to be 7% of unbound vascular plasma and unbound lung intracellular exposures.

CONCLUSIONS

The whole-body PBPK model for bedaquiline and M2 predicted unbound concentrations in brain to be significantly lower than the unbound concentrations in the lung at clinically relevant doses. Our findings suggest that bedaquiline may result in relatively inferior efficacy against drug-resistant TBM when compared with efficacy against drug-resistant pulmonary TB.

Bioanalysis of bedaquiline in human plasma by liquid chromatography-tandem mass spectrometry: Application to pharmacokinetic study

Introduction

A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for estimation of bedaquiline (BDQ) in human plasma using the deuterated analogue of the analyte, bedaquiline-d6 (BDQ-d6) as the internal standard.

Methods

The plasma sample of 50 µL was extracted by liquid-liquid extraction using methyl tertiary butyl ether (MTBE). The separation was achieved on Zodiac C18 (50 x 4.6 mm, 5 µm) column with a mobile phase consisting of methanol and 5 mM ammonium formate in 0.1 % formic acid (w/v) (90:10, v/v) at a flow rate of 1.0 mL/min. Protonated analyte and internal standard were detected on a triple quadrupole mass spectrometer using multiple reaction monitoring (MRM) mode.

Results

The linearity of the method was established in the concentration range of 5---1800 ng/mL with correlation coefficient, r2 ≥ 0.99. All the validated parameters were found well within the limits.

Discussion

The method was applied for the first time to evaluate the pharmacokinetic parameters after single oral dose of BDQ 100 mg under fed conditions in healthy human volunteers, and the results were further authenticated by incurred sample reanalysis.

Pharmacokinetics of bedaquiline in cerebrospinal fluid (CSF) in patients with pulmonary tuberculosis (TB)

BACKGROUND

With current treatment options most patients with CNS TB develop severe disability or die. Drug-resistant tuberculous meningitis is nearly uniformly fatal. Novel treatment strategies are needed. Bedaquiline, a potent anti-TB drug, has been reported to be absent from CSF in a single report.

OBJECTIVES

To explore the pharmacokinetics of bedaquiline and its M2 metabolite in the CSF of patients with pulmonary TB.

PATIENTS AND METHODS

Individuals with rifampicin-resistant pulmonary TB established on a 24 week course of treatment with bedaquiline underwent a lumbar puncture along with multiple blood sample collections over 24 h for CSF and plasma pharmacokinetic assessment, respectively. To capture the expected low bedaquiline and M2 concentrations (due to high protein binding in plasma) we optimized CSF collection and storage methods in vitro before concentrations were quantified via liquid chromatography with tandem MS.

RESULTS

Seven male participants were enrolled, two with HIV coinfection. Using LoBind® tubes lined with a 5% BSA solution, bedaquiline and M2 could be accurately measured in CSF. Bedaquiline and M2 were present in all patients at all timepoints at concentrations similar to the estimated unbound fractions in plasma.

CONCLUSIONS

Bedaquiline and M2 penetrate freely into the CSF of pulmonary TB patients with a presumably intact blood-brain barrier. Clinical studies are urgently needed to determine whether bedaquiline can contribute meaningfully to the treatment of CNS TB.

Sterile tuberculous granuloma in a patient with XDR-TB treated with bedaquiline, pretomanid and linezolid

Drug-resistant tuberculosis (DR-TB) continues to pose a threat to the global eradication of TB. Regimens for extensively drug-resistant (XDR) TB are lengthy and poorly tolerated, often with unsuccessful outcomes. The TB Alliance Nix-TB trial investigated the safety and efficacy of a 26-week regimen of bedaquiline, pretomanid and linezolid (BPaL) in participants with XDR-TB, multidrug-resistant (MDR) TB treatment failure or intolerance. In this trial 9 out of 10 participants were cured. We describe a trial participant with XDR-TB who presented with new-onset seizures soon after BPaL treatment completion. Imaging showed a right temporal ring-enhancing lesion, and a sterile tuberculous granuloma was confirmed after a diagnostic, excisional biopsy. Learning points include management of a participant with a tuberculoma after BPaL completion, efficacy of new medications for central nervous system (CNS) TB and a review of their CNS penetration. This is the first case of pretomanid use in CNS TB.

Neuroprotective Effect of a Novel ATP-Synthase Inhibitor Bedaquiline in Cerebral Ischemia-Reperfusion Injury

Mitochondrial dysfunction during ischemic stroke ultimately manifests as ATP depletion. Mitochondrial ATP synthase upon loss of mitochondrial membrane potential during ischemia rapidly hydrolyses ATP and thus contributes to ATP depletion. Increasing evidence suggests that inhibition of ATP synthase limits ATP depletion and is protective against ischemic tissue damage. Bedaquiline (BDQ) is an anti-microbial agent, approved for clinical use, that inhibits ATP synthase of Mycobacteria; however recently it has been shown to act on mitochondrial ATP synthase, inhibiting both ATP synthesis and hydrolysis in low micromolar concentrations. In this study, we investigated whether preconditioning with BDQ can alleviate ischemia/reperfusion-induced brain injury in Wistar rats after middle cerebral artery occlusion-reperfusion and whether it affects mitochondrial functions. We found that BDQ was effective in limiting necrosis and neurological dysfunction during ischemia-reperfusion. BDQ also caused inhibition of ATPase activity, mild uncoupling of respiration, and stimulated mitochondrial respiration both in healthy and ischemic mitochondria. Mitochondrial calcium retention capacity was unaffected by BDQ preconditioning. We concluded that BDQ has neuroprotective properties associated with its action on mitochondrial respiration and ATPase activity.

Pretomanid: A novel therapeutic paradigm for treatment of drug resistant tuberculosis

Tuberculosis is currently an anticipated driver of pandemic diseases. It remains an imminent issue accounting for about 1.4 million deaths annually across the world. Since the evolution of human entity drug susceptible tuberculosis was managed through potent first line therapies. Unfortunately, the emergence of newer multitude strains refractory amongst available drugs in Drug resistant TB has led to an emergence MDR-TB and XDR-TB. Moreover, the increasing incidence of drug susceptible TB in developing countries paved way to development of new guidelines for treating various form of tuberculosis. Furthermore, newer regimens are warranted to combat resistance that preferably cause a reduction in mortality. Until now, various ongoing trials are being carried in order to potentially evaluate the suitable novel drug candidates, repurposed drugs and host directed therapies that will optimistically be safe, easy to tolerate, cost effective and non-toxic that will modify the prospects for treating drug resistant TB and latent TB. In context, the current scenario seems to impose a significant challenge on health care researchers in the field of drug discovery owing to complexities, prolong treatment duration, and is cumbersome. Pretomanid is a novel drug with potent bactericidal properties emerging a key advancement used in combination along with other drug therapies This review details the role of pretomanid in treating tuberculosis and the clinical trials in adultsd.

Mass Spectrometric Imaging of the Brain Demonstrates the Regional Displacement of 6-Monoacetylmorphine by Naloxone

Overdose is the main cause of mortality among heroin users. Many of these overdose-induced deaths can be prevented through the timely administration of naloxone (NLX), a nonselective mu (μ)-, kappa (κ)-, and delta (δ)-opioid receptor antagonist. NLX competitively inhibits opioid-overdose-induced respiratory depression without eliciting any narcotic effect itself. The aim of this study was to investigate the antagonistic action of NLX by comparing its distribution to that of 6-monacetylmorphine (6-MAM), heroin's major metabolite, in a rodent model using mass spectrometric imaging (MSI) in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Male Sprague-Dawley rats (n = 5) received heroin (10 mg kg^-1) intraperitoneally, NLX (10 mg kg^-1) intranasally, and NLX injected intranasally 5 min after heroin administration. The animals were sacrificed 15 min after dose and brain tissues were harvested. The MSI image analysis showed a region-specific distribution of 6-MAM in the brain regions including the corpus callosum, hippocampal formation, cerebral cortex, corticospinal tracts, caudate putamen, thalamus, globus pallidus, hypothalamus, and basal forebrain regions of the brain. The antagonist had a similar biodistribution throughout the brain in both groups of animals that received NLX or NLX after heroin administration. The MSI analysis demonstrated that the intensity of 6-MAM in these brain regions was reduced following NLX treatment. The decrease in 6-MAM intensity was caused by its displacement by the antagonist and its binding to these receptors in these specific brain regions, consequently enhancing the opioid elimination. These findings will contribute to the evaluation of other narcotic antagonists that might be considered for use in the treatment of drug overdose via MSI.

Improved Synthesis and Isolation of Bedaquiline

Bedaquiline (BDQ) is the most critical pharmaceutical in the world for treating multidrug-resistant Mycobacterium tuberculosis. Despite it being highly effective, BDQ asymmetric synthesis remains a challenge. Herein, the influence of chiral bases, namely, bis(1-phenylethyl)amine, bisoxazoline, and sparteine on the diastereoselective lithiation reaction to obtain BDQ was investigated. The highest diastereoselective ratio (dr) emerged as 90:10 from the (+)-bis[(R)-1-phenylethyl] lithium amide. This is a significant improvement from the 50:50 dr achieved from the commercial synthesis. Thereafter, the desired (90:10 RS, SR) diastereomeric mixture was easily isolated via a gravity column and subjected to chiral supercritical fluid chromatography (SFC) to access the desired enantiomer (1R, 2S)-BDQ. The advantages of this procedure are enhanced diastereoselection as well as a greener, faster way to achieve excellent enantioseparation (up to 1.0 g scale).

Radiosynthesis and PET Bioimaging of 76Br-Bedaquiline in a Murine Model of Tuberculosis

Bedaquiline is a promising drug against tuberculosis (TB), but limited data are available on its intralesional pharmacokinetics. Moreover, current techniques rely on invasive tissue resection, which is difficult in humans and generally limited even in animals. In this study, we developed a novel radiosynthesis for 76Br-bedaquiline and performed noninvasive, longitudinal whole-body positron emission tomography (PET) in live, Mycobacterium tuberculosis-infected mice over 48 h. After the intravenous injection, 76Br-bedaquiline distributed to all organs and selectively localized to adipose tissue and liver, with excellent penetration into infected lung lesions (86%) and measurable penetration into the brain parenchyma (15%). Ex vivo high resolution, two-dimensional autoradiography, and same section hematoxylin/eosin and immunofluorescence provided detailed intralesional drug biodistribution. PET bioimaging and high-resolution autoradiography are novel techniques that can provide detailed, multicompartment, and intralesional pharmacokinetics of new and existing TB drugs. These technologies can significantly advance efforts to optimize drug dosing.

Spatial distribution of elvitegravir and tenofovir in rat brain tissue: Application of matrix-assisted laser desorption/ionization mass spectrometry imaging and liquid chromatography/tandem mass spectrometry

RATIONALE

The complexity of central nervous system (CNS) drug delivery is the main obstacle with the blood-brain barrier (BBB) known to restrict access of most pharmaceutical drugs into the brain. Mass spectrometry imaging (MSI) offers possibilities for studying drug deposition into the CNS.

METHODS

The deposition and spatial distribution of the two antiretroviral drugs elvitegravir and tenofovir in the brain were investigated in healthy female Sprague-Dawley rats following a single intraperitoneal administration (50 mg/kg). This was achieved by the utilization of quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) and matrix-assisted laser desorption/ionization (MALDI) MSI.

RESULTS

LC/MS/MS showed that elvitegravir has better BBB penetration, reaching maximum concentration in the brain (C_max brain) of 976.5 ng/g. In contrast, tenofovir displayed relatively lower BBB penetration, reaching C_max brain of 54.5 ng/g. MALDI-MSI showed the heterogeneous distribution of both drugs in various brain regions including the cerebral cortex.

CONCLUSIONS

LC/MS/MS and MALDI-MSI provided valuable information about the relative concentration and the spatial distribution of the two common antiretroviral drugs. This study has also shown the capability of MALDI-MSI for direct visualization of pharmaceutical drugs in situ.

Mass spectrometric investigations into the brain delivery of abacavir, stavudine and didanosine in a rodent model

HIV replication in the brain is unopposed due to reduced antiretroviral drug penetration into the central nervous system (CNS). Prevalence of HIV-associated neurocognitive disorder (HAND) has increased severely in patients living with HIV despite current treatments. The aims of this study were to evaluate the brain bio-distribution of alternative nucleoside reverse transcriptase inhibitors, abacavir, stavudine and didanosine in the CNS and to determine their localization patterns in the brain.Sprague-Dawley rats received 50 mg kg^-1 single i.p dose of each drug. Mass spectrometric techniques were then used to investigate the pharmacokinetics and localization patterns of these drugs in the brain using LC-MS/MS and mass spectrometric imaging (MSI), respectively.Abacavir, stavudine and didanosine reached the Brain C_max with concentration of 831.2, 1300 and 43.37 ngmL^-1, respectively. Based on MSI analysis Abacavir and Stavudine were located in brain regions that are strongly implicated in the progression of HAND.Abacavir and Stavudine penetrated into CNS, reaching a C_max that was above the IC₅₀ for HIV (457.6 and 112.0 ngmL^-1, respectively), however, it was noted ddI showed poor entry within the brain, therefore, it is recommended that this drug cannot be considered for treating CNS-HIV.

Rilpivirine as a potential candidate for the treatment of HIV-associated neurocognitive disorders (HAND)

As the HIV epidemic continues to contribute to global morbidity and mortality, the prevalence of HIV-associated neurological disorders (HAND) also continues to be a major concern in infected individuals, despite the widespread use of combination antiretroviral therapy. Therefore, current antiretroviral drugs should be able to reach therapeutic levels in the brain for the treatment of HAND. The brain distribution of the next-generation non-nucleoside reverse transcriptase inhibitor, rilpivirine (RPV) was investigated in healthy female Sprague-Dawley (SD) rats. The presented study involves the use of liquid chromatography-tandem mass spectrometry (LC-MS/MS) to estimate the concentrations of RPV in plasma and brain homogenate samples. The use of matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) provided regional spatial distribution of RPV in brain tissue sections. The localization of RPV was found to be relatively high in the hypothalamus, thalamus and corpus callosum, brain regions known to be associated with neurodegeneration during HAND (including the cerebral cortex). This study has shown that RPV has an excellent blood-brain barrier penetrability. Thus, in combination with other antiretroviral drugs, better central nervous system (CNS) protection against HAND can possibly be achieved.

Tissue Imaging by Mass Spectrometry: A Practical Guide for the Medicinal Chemist

Understanding the tissue distribution of therapeutic molecules is often critical for assessing their efficacy and toxicity. Unfortunately, standard methods for monitoring localized drug distribution are resource-intensive and are typically performed late in the discovery process. As a result, early development efforts often progress without detailed information on the effect that changes in structure and/or formulation have on drug localization. Recent innovations in mass spectrometry (MS) provide new options for mapping the spatial distribution of drug in tissue and allow parallel detection of endogenous species. These advances are improving access to drug distribution data early in discovery and provide insight into local biochemical changes that are directly related to drug activity. The literature on these topics is voluminous, and the technology is advancing rapidly, offering a bewildering array of options for researchers who are new to the field. To guide medicinal chemists who wish to apply these methods in their research, this technology perspective provides our views on practical applications that are currently enabled by various MS imaging (MSI) approaches, along with recommendations for how best to implement these methods in pharmaceutical R&D.