In silico evaluation and exploration of antibiotic tuberculosis treatment regimens

Abstract Background Improvement in tuberculosis treatment regimens requires selection of antibiotics and dosing schedules from a large design space of possibilities. Incomplete knowledge of antibiotic and host immune dynamics in tuberculosis granulomas impacts clinical trial design and success, and variations among clinical trials hamper side-by-side comparison of regimens. Our objective is to systematically evaluate the efficacy of isoniazid and rifampin regimens, and identify modifications to these antibiotics that improve treatment outcomes. Results We pair a spatio-temporal computational model of host immunity with pharmacokinetic and pharmacodynamic data on isoniazid and rifampin. The model is calibrated to plasma pharmacokinetic and granuloma bacterial load data from non-human primate models of tuberculosis and to tissue and granuloma measurements of isoniazid and rifampin in rabbit granulomas. We predict the efficacy of regimens containing different doses and frequencies of isoniazid and rifampin. We predict impacts of pharmacokinetic/pharmacodynamic modifications on antibiotic efficacy. We demonstrate that suboptimal antibiotic concentrations within granulomas lead to poor performance of intermittent regimens compared to daily regimens. Improvements from dose and frequency changes are limited by inherent antibiotic properties, and we propose that changes in intracellular accumulation ratios and antimicrobial activity would lead to the most significant improvements in treatment outcomes. Results suggest that an increased risk of drug resistance in fully intermittent as compared to daily regimens arises from higher bacterial population levels early during treatment. Conclusions Our systems pharmacology approach complements efforts to accelerate tuberculosis therapeutic development.http://deepblue.lib.umich.edu/bitstream/2027.42/116019/1/12918_2015_Article_221.pd

Mass spectrometry imaging of levofloxacin distribution in TB-infected pulmonary lesions by MALDI-MSI and continuous liquid microjunction surface sampling

A multi-modal mass spectrometry imaging (MSI) and profiling approach has been applied to assess the partitioning of the anti-TB fluoroquinolone levofloxacin into pulmonary lesions. Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) and a commercial liquid microjunction surface sampling technology (LMJ-SSP), or flowprobe, have been used to both spatially profile and image drug distributions in lung tissue sections from TB-infected rabbits following oral administration of a single human-equivalent dose., Levofloxacin levels were highest at 6 h post-dose in normal lung, cellular granuloma, and necrotic caseum compartments. The drug accumulated in the cellular granuloma regions with lower amounts partitioning into central caseous compartments. Flowprobe imaging at 630 μm (limited by the probe tip diameter) enabled visualization of drug distribution into lesion compartments, including limited differentiation of relative drug abundance in cellular versus caseous regions of the lesions., MALDI-MSI analysis at 75 μm provided more detailed drug distribution, which clearly accumulated in the cellular region immediately surrounding the central caseum core. Imaging and profiling data acquired by flowprobe and MALDI-MSI were validated by quantitative LC/MS/MS analysis of lung and granuloma homogenates taken from the same animals., The results of the investigation show flowprobe imaging and sampling as a rapid and sensitive alternative to MALDI-MSI for profiling drug distributions into tissues when spatial resolution of data below the threshold of the probe diameter is not required

High-resolution mapping of fluoroquinolones in TB rabbit lesions reveals specific distribution in immune cell types.

Understanding the distribution patterns of antibiotics at the site of infection is paramount to selecting adequate drug regimens and developing new antibiotics. Tuberculosis (TB) lung lesions are made of various immune cell types, some of which harbor persistent forms of the pathogen, Mycobacterium tuberculosis. By combining high resolution MALDI MSI with histology staining and quantitative image analysis in rabbits with active TB, we have mapped the distribution of a fluoroquinolone at high resolution, and identified the immune-pathological factors driving its heterogeneous penetration within TB lesions, in relation to where bacteria reside. We find that macrophage content, distance from lesion border and extent of necrosis drive the uneven fluoroquinolone penetration. Preferential uptake in macrophages and foamy macrophages, where persistent bacilli reside, compared to other immune cells present in TB granulomas, was recapitulated in vitro using primary human cells. A nonlinear modeling approach was developed to help predict the observed drug behavior in TB lesions. This work constitutes a methodological advance for the co-localization of drugs and infectious agents at high spatial resolution in diseased tissues, which can be applied to other diseases with complex immunopathology

Fluoroquinolone Efficacy against Tuberculosis Is Driven by Penetration into Lesions and Activity against Resident Bacterial Populations.

Fluoroquinolones represent the pillar of multidrug-resistant tuberculosis (MDR-TB) treatment, with moxifloxacin, levofloxacin, or gatifloxacin being prescribed to MDR-TB patients. Recently, several clinical trials of "universal" drug regimens, aiming to treat drug-susceptible and drug-resistant TB, have included a fluoroquinolone. In the absence of clinical data comparing their side-by-side efficacies in controlled MDR-TB trials, a pharmacological rationale is needed to guide the selection of the most efficacious fluoroquinolone. The present studies were designed to test the hypothesis that fluoroquinolone concentrations (pharmacokinetics) and activity (pharmacodynamics) at the site of infection are better predictors of efficacy than the plasma concentrations and potency measured in standard growth inhibition assays and are better suited to determinations of whether one of the fluoroquinolones outperforms the others in rabbits with active TB. We first measured the penetration of these fluoroquinolones in lung lesion compartments, and their potency against bacterial populations that reside in each compartment, to compute lesion-centric pharmacokinetic-pharmacodynamic (PK/PD) parameters. PK modeling methods were used to quantify drug penetration from plasma to tissues at human-equivalent doses. On the basis of these metrics, moxifloxacin emerged with a clear advantage, whereas plasma-based PK/PD favored levofloxacin (the ranges of the plasma AUC/MIC ratio [i.e., the area under the concentration-time curve over 24 h in the steady state divided by the MIC] are 46 to 86 for moxifloxacin and 74 to 258 for levofloxacin). A comparative efficacy trial in the rabbit model of active TB demonstrated the superiority of moxifloxacin in reducing bacterial burden at the lesion level and in sterilizing cellular and necrotic lesions. Collectively, these results show that PK/PD data obtained at the site of infection represent an adequate predictor of drug efficacy against TB and constitute the baseline required to explore synergies, antagonism, and drug-drug interactions in fluoroquinolone-containing regimens

Inhibition of fatty acid oxidation promotes macrophage control of Mycobacterium tuberculosis

Macrophage activation involves metabolic reprogramming to support antimicrobial cellular functions. How these metabolic shifts influence the outcome of infection by intracellular pathogens remains incompletely understood

Linezolid pharmacokinetics in MDR-TB : a systematic review, meta-analysis and Monte Carlo simulation

This work was supported by the Wellcome Trust (grant numbers 109129/Z/15/Z to JM and 105620/Z/14/Z to DS and MC).Objectives The oxazolidinone linezolid is an effective component of drug - resistant TB treatment, but use is limited by toxicity and the optimum dose is uncertain . Current strategies are not informed by clinical pharmacokinetic/pharmacodynamic (PK/PD) data, we aimed to aimed to address this gap. Methods We defined linezolid PK/PD targets for efficacy; free area under the time - concentration curve: minimum inhibitory concentration ratio (ƒAUC0-24:M IC) >119m g/L/hr and safety; free minimum concentration (Cmin) <1.38mg/L . We extracted individual - level linezolid PK data from existing studies on TB patients and performed meta - analysis; producing summary estimates of ƒAUC0-24 and ƒCmin for published doses . Combining these with a published MIC distribution, we performed Monte Carlo simulations of target attainment. Results The efficacy target was attained in all simulated individuals at 300mg q12h and 600mg q12h , but only 20.7% missed the safety target at 300mg q12h versus 98.5% at 600mg q12h . Although suggesting 300mg q12h should be used preferentially, these data were reliant on a single centre . Efficacy and safety targets were missed by 41.0% and 24.2% respectively at 300mg q24h , and 44.5% and 27.5% at 600mg q24h . However, the confounding effect of between study heterogeneity on target attainment for q24h regimens was considerable. Conclusions 300mg q12h linezolid dosing may retain the efficacy of the 600mg q12h licensed dosing with improved safety. Data to evaluate commonly used 300mg q24h and 600mg q24h doses is limited. Comprehensive, prospectively obtained PK/PD data for linezolid doses in drug - resistant TB treatment are required.Publisher PDFPeer reviewe

Experimental Tuberculosis in the Wistar Rat: A Model for Protective Immunity and Control of Infection

BACKGROUND: Despite the availability of many animal models for tuberculosis (TB) research, there still exists a need for better understanding of the quiescent stage of disease observed in many humans. Here, we explored the use of the Wistar rat model for the study of protective immunity and control of Mycobacterium tuberculosis (Mtb) infection. METHODOLOGY/PRINCIPAL FINDINGS: The kinetics of bacillary growth, evaluated by the colony stimulating assay (CFU) and the extent of lung pathology in Mtb infected Wistar rats were dependent on the virulence of the strains and the size of the infecting inoculums. Bacillary growth control was associated with induction of T helper type 1 (Th1) activation, the magnitude of which was also Mtb strain and dose dependent. Histopathology analysis of the infected lungs demonstrated the formation of well organized granulomas comprising epithelioid cells, multinucleated giant cells and foamy macrophages surrounded by large numbers of lymphocytes. The late stage subclinical form of disease was reactivated by immunosuppression leading to increased lung CFU. CONCLUSION: The Wistar rat is a valuable model for better understanding host-pathogen interactions that result in control of Mtb infection and potentially establishment of latent TB. These properties together with the ease of manipulation, relatively low cost and well established use of rats in toxicology and pharmacokinetic analyses make the rat a good animal model for TB drug discovery

Novel Cephalosporins Selectively Active on Nonreplicating Mycobacterium tuberculosis

We report two series of novel cephalosporins that are bactericidal to Mycobacterium tuberculosis alone of the pathogens tested, which only kill M. tuberculosis when its replication is halted by conditions resembling those believed to pertain in the host, and whose bactericidal activity is not dependent upon or enhanced by clavulanate, a β-lactamase inhibitor. The two classes of cephalosporins bear an ester or alternatively an oxadiazole isostere at C-2 of the cephalosporin ring system, a position that is almost exclusively a carboxylic acid in clinically used agents in the class. Representatives of the series kill M. tuberculosis within macrophages without toxicity to the macrophages or other mammalian cells