Resistance to thiacetazone derivatives active against Mycobacterium abscessus involves mutations in the MmpL5 transcriptional repressor MAB_4384

Available chemotherapeutic options are very limited against Mycobacterium abscessus, which imparts a particular challenge in the treatment of cystic fibrosis (CF) patients infected with this rapid-growing mycobacterium. New drugs are urgently needed against this emerging pathogen, but the discovery of active chemotypes has not been performed intensively. Interestingly, however, the repurposing of thiacetazone (TAC), a drug once used to treat tuberculosis, has increased following the deciphering of its mechanism of action and the detection of significantly more potent analogues. We, therefore, report studies performed on a library of 38 TAC-related derivatives, previously evaluated for their antitubercular activity. Several compounds, including D6, D15 and D17, were found to exhibit potent activity in vitro against M. abscessus, Mycobacterium massiliense and Mycobacterium bolletii clinical isolates from CF and non-CF patients. Similarly to TAC in M. tuberculosis, the three analogues act as pro-drugs in M. abscessus, requiring bioactivation by the EthA enzyme, MAB_0985. Importantly, mutations in the transcriptional TetR repressor MAB_4384, with concomitant upregulation of the divergently oriented adjacent genes encoding an MmpS5/MmpL5 efflux pump system, accounted for high cross-resistance levels among all three compounds. Overall, this study uncovered a new mechanism of drug resistance in M. abscessus and demonstrated that simple structural optimization of the TAC scaffold can lead to the development of new drug candidates against M. abscessus infections

The Impact of a Public Health Crisis on the Well-Being of UK Senior Care Home Staff: A Qualitative Interview Study

Context: Care homes in the UK were hit badly by the COVID-19 pandemic, with numerous outbreaks and deaths of residents and staff. Objectives: To capture the impact of the pandemic on care home staff well-being and share insights and learning about how to optimise support for the workforce. Methods: Fifteen senior care staff from care homes looking after older people in England were interviewed between December 2020 and March 2021, when the sector was still under strict restriction measures. The topic guide was developed in consultation with care home staff. Interviews were transcribed and analysed using a reflexive thematic analysis approach to identify themes and sub-themes of the impact on staff well-being. Findings: The impact of the pandemic was overwhelmingly negative, with those interviewed reporting both mental and physical health implications. We identified three themes: emotional exhaustion (upset and trauma, increased responsibility and workload, feelings of guilt); frustration (feeling misunderstood, undervalued, unrecognised, abandoned); and relationships (the importance of supportive working relationships within the care home and with external agencies). Limitations: Staff interviewed were managers or in other senior roles; it would be beneficial to synthesise this research with studies involving other care home staff and residents and their relatives. Given the disparate nature of the care home sector, a larger sample may have identified additional insights. Implications: This study provides insight into the resilience of care home staff during the pandemic and challenges to this; this could help to inform future efforts as to support of the workforce and sector

Synthesis, antitubercular activity and mechanism of resistance of highly effective thiacetazone analogues

Defining the pharmacological target(s) of currently used drugs and developing new analogues with greater potency are both important aspects of the search for agents that are effective against drug-sensitive and drug-resistant Mycobacterium tuberculosis. Thiacetazone (TAC) is an anti-tubercular drug that was formerly used in conjunction with isoniazid, but removed from the antitubercular chemotherapeutic arsenal due to toxic side effects. However, several recent studies have linked the mechanisms of action of TAC to mycolic acid metabolism and TAC-derived analogues have shown increased potency against M. tuberculosis. To obtain new insights into the molecular mechanisms of TAC resistance, we isolated and analyzed 10 mutants of M. tuberculosis that were highly resistant to TAC. One strain was found to be mutated in the methyltransferase MmaA4 at Gly101, consistent with its lack of oxygenated mycolic acids. All remaining strains harbored missense mutations in either HadA (at Cys61) or HadC (at Val85, Lys157 or Thr123), which are components of the bhydroxyacyl-ACP dehydratase complex that participates in the mycolic acid elongation step. Separately, a library of 31 new TAC analogues was synthesized and evaluated against M. tuberculosis. Two of these compounds, 15 and 16, exhibited minimal inhibitory concentrations 10-fold lower than the parental molecule, and inhibited mycolic acid biosynthesis in a dose-dependent manner. Moreover, overexpression of HadAB HadBC or HadABC in M. tuberculosis led to high level resistance to these compounds, demonstrating that their mode of action is similar to that of TAC. In summary, this study uncovered new mutations associated with TAC resistance and also demonstrated that simple structural optimization of the TAC scaffold was possible and may lead to a new generation of TAC-derived drug candidates for the potential treatment of tuberculosis as mycolic acid inhibitors

Thiacetazone, an Antitubercular Drug that Inhibits Cyclopropanation of Cell Wall Mycolic Acids in Mycobacteria

Background. Mycolic acids are a complex mixture of branched, long-chain fatty acids, representing key components of the highly hydrophobic mycobacterial cell wall. Pathogenic mycobacteria carry mycolic acid sub-types that contain cyclopropane rings. Double bonds at specific sites on mycolic acid precursors are modified by the action of cyclopropane mycolic acid synthases (CMASs). The latter belong to a family of S-adenosyl-methionine-dependent methyl transferases, of which several have been well studied in Mycobacterium tuberculosis, namely, MmaA1 through A4, PcaA and CmaA2. Cyclopropanated mycolic acids are key factors participating in cell envelope permeability, host immunomodulation and persistence of M. tuberculosis. While several antitubercular agents inhibit mycolic acid synthesis, to date, the CMASs have not been shown to be drug targets. Methodology/Principle Findings. We have employed various complementary approaches to show that the antitubercular drug, thiacetazone (TAC), and its chemical analogues, inhibit mycolic acid cyclopropanation. Dramatic changes in the content and ratio of mycolic acids in the vaccine strainMycobacterium bovis BCG, as well as in the related pathogenic speciesMycobacterium marinum were observed after treatment with the drugs. Combination of thin layer chromatography, mass spectrometry and Nuclear Magnetic Resonance (NMR) analyses of mycolic acids purified fromdrug-treated mycobacteria showed a significant loss of cyclopropanation in both the a- and oxygenated mycolate sub-types. Additionally, High-Resolution Magic Angle Spinning (HR-MAS) NMR analyses on whole cells was used to detect cell wall-associated mycolates and to quantify the cyclopropanation status of the cell envelope. Further, overexpression of cmaA2, mmaA2 or pcaA in mycobacteria partially reversed the effects of TAC and its analogue on mycolic acid cyclopropanation, suggesting that the drugs act directly on CMASs. Conclusions/Significance. This is a first report on them echanism of action of TAC, demonstrating the CMASs as its cellular targets in mycobacteria. The implications of this study may be important for the design of alternative strategies for tuberculosis treatment

PCT/GB2009/000064 Weight Reducing Compounds (Tech1660)

The present invention relates to compounds which find use as weight reducing agents, and find use in treating obesity and/or excess adiposity

b-antiTB drugs

Chapter focusing on anti tuberculosis drugs

The identification of 2-aminothiazole-4-carboxylates active against Mycobacterium tuberculosis

The 2009 Gordon Conference on Tuberculosis Drug Development will cover the range of activities involved in producing new antibiotics. This paper examines the identification of 2-aminothiazole-4-carboxylates active against Mycobacterium tuberculosis

Strategies and challenges involved in the discovry of new chemical entities during early-stage tuberculosis drug discovery

There is an increasing flow of new antituberculosis chemical entities entering the tuberculosis drug development pipeline. Although this is encouraging, the current number of compounds is too low to meet the demanding criteria required for registration, shorten treatment duration, treat drug-resistant infection, and address pediatric tuberculosis cases. More new chemical entities are needed urgently to supplement the pipeline and ensure that more drugs and regimens enter clinical practice. Most drug discovery projects under way exploit enzyme systems deemed essential in a specific Mycobacterium tuberculosis biosynthetic pathway or develop chemical scaffolds identified by phenotypic screening of compound libraries, specific pharmacophores or chemical clusters, and natural products. Because the development of a compound for treating tuberculosis is even longer than for treating other infection indications, the identification of selective, potent, and safe chemical entities early in the drug development process is essential to ensure that the pipeline is filled with new candidates that have the best chance to reach the clinic

Written Evidence from TBD-UK, Dr Geoff Coxon

http://www.publications.parliament.uk/pa/cm201012/cmselect/cmintdev/1569/1569vw03.ht

The UK's response to global tuberculosis

This report outlines challenges to tacking tuberculosis (TB) in high TB burden countries and considers ways the UK Government should respond to this pandemic. It seeks to make constructive recommendations to enhance policy and contribute to the debate about how the UK can most effectively work to prevent the unnecessary loss of 10 million lives to TB by 2015.