Biochemical and Structural Characterization of Selective Allosteric Inhibitors of the Plasmodium falciparum Drug Target, Prolyl-tRNA-synthetase

Plasmodium falciparum (<i>Pf</i>) prolyl-tRNA synthetase (ProRS) is one of the few chemical-genetically validated drug targets for malaria, yet highly selective inhibitors have not been described. In this paper, approximately 40,000 compounds were screened to identify compounds that selectively inhibit <i>Pf</i>ProRS enzyme activity versus Homo sapiens (<i>Hs</i>) ProRS. X-ray crystallography structures were solved for apo, as well as substrate- and inhibitor-bound forms of <i>Pf</i>ProRS. We identified two new inhibitors of <i>Pf</i>ProRS that bind outside the active site. These two allosteric inhibitors showed >100 times specificity for <i>Pf</i>ProRS compared to <i>Hs</i>ProRS, demonstrating this class of compounds could overcome the toxicity related to <i>Hs</i>ProRS inhibition by halofuginone and its analogues. Initial medicinal chemistry was performed on one of the two compounds, guided by the cocrystallography of the compound with <i>Pf</i>ProRS, and the results can instruct future medicinal chemistry work to optimize these promising new leads for drug development against malaria

Lysyl-tRNA synthetase as a drug target in malaria and cryptosporidiosis

Malaria and cryptosporidiosis, caused by apicomplexan parasites, remain major drivers of global child mortality. New drugs for the treatment of malaria and cryptosporidiosis, in particular, are of high priority; however, there are few chemically validated targets. The natural product cladosporin is active against blood- and liver-stage; Plasmodium falciparum; and; Cryptosporidium parvum; in cell-culture studies. Target deconvolution in; P. falciparum; has shown that cladosporin inhibits lysyl-tRNA synthetase (; Pf; KRS1). Here, we report the identification of a series of selective inhibitors of apicomplexan KRSs. Following a biochemical screen, a small-molecule hit was identified and then optimized by using a structure-based approach, supported by structures of both; Pf; KRS1 and; C. parvum; KRS (; Cp; KRS). In vivo proof of concept was established in an SCID mouse model of malaria, after oral administration (ED; 90; = 1.5 mg/kg, once a day for 4 d). Furthermore, we successfully identified an opportunity for pathogen hopping based on the structural homology between; Pf; KRS1 and; Cp; KRS. This series of compounds inhibit; Cp; KRS and; C. parvum; and; Cryptosporidium hominis; in culture, and our lead compound shows oral efficacy in two cryptosporidiosis mouse models. X-ray crystallography and molecular dynamics simulations have provided a model to rationalize the selectivity of our compounds for; Pf; KRS1 and; Cp; KRS vs. (human); Hs; KRS. Our work validates apicomplexan KRSs as promising targets for the development of drugs for malaria and cryptosporidiosis

Development of a Novel Lead that Targets <i>M. tuberculosis</i> Polyketide Synthase 13

Widespread resistance to first-line TB drugs is a major problem that will likely only be resolved through the development of new drugs with novel mechanisms of action. We have used structure-guided methods to develop a lead molecule that targets the thioesterase activity of polyketide synthase Pks13, an essential enzyme that forms mycolic acids, required for the cell wall of Mycobacterium tuberculosis. Our lead, TAM16, is a benzofuran class inhibitor of Pks13 with highly potent in vitro bactericidal activity against drug-susceptible and drug-resistant clinical isolates of M. tuberculosis. In multiple mouse models of TB infection, TAM16 showed in vivo efficacy equal to the first-line TB drug isoniazid, both as a monotherapy and in combination therapy with rifampicin. TAM16 has excellent pharmacological and safety profiles, and the frequency of resistance for TAM16 is ∼100-fold lower than INH, suggesting that it can be developed as a new antitubercular aimed at the acute infection. A small molecule inhibitor of M. tuberculosis polyketide synthase shows strong efficacy in murine models of infection.</p

Optimization of TAM16, a Benzofuran That Inhibits the Thioesterase Activity of Pks13; Evaluation toward a Preclinical Candidate for a Novel Antituberculosis Clinical Target

[Image: see text] With increasing drug resistance in tuberculosis (TB) patient populations, there is an urgent need for new drugs. Ideally, new agents should work through novel targets so that they are unencumbered by preexisting clinical resistance to current treatments. Benzofuran 1 was identified as a potential lead for TB inhibiting a novel target, the thioesterase domain of Pks13. Although, having promising activity against Mycobacterium tuberculosis, its main liability was inhibition of the hERG cardiac ion channel. This article describes the optimization of the series toward a preclinical candidate. Despite improvements in the hERG liability in vitro, when new compounds were assessed in ex vivo cardiotoxicity models, they still induced cardiac irregularities. Further series development was stopped because of concerns around an insufficient safety window. However, the demonstration of in vivo activity for multiple series members further validates Pks13 as an attractive novel target for antitubercular drugs and supports development of alternative chemotypes

Chemogenomics identifies acetyl-coenzyme A synthetase as a target for malaria treatment and prevention

We identify the Plasmodium falciparum acetyl-coenzyme A synthetase (PfAcAS) as a druggable target, using genetic and chemical validation. In vitro evolution of resistance with two antiplasmodial drug-like compounds (MMV019721 and MMV084978) selects for mutations in PfAcAS. Metabolic profiling of compound-treated parasites reveals changes in acetyl-CoA levels for both compounds. Genome editing confirms that mutations in PfAcAS are sufficient to confer resistance. Knockdown studies demonstrate that PfAcAS is essential for asexual growth, and partial knockdown induces hypersensitivity to both compounds. In vitro biochemical assays using recombinantly expressed PfAcAS validates that MMV019721 and MMV084978 directly inhibit the enzyme by preventing CoA and acetate binding, respectively. Immunolocalization studies reveal that PfAcAS is primarily localized to the nucleus. Functional studies demonstrate inhibition of histone acetylation in compound-treated wild-type, but not in resistant parasites. Our findings identify and validate PfAcAS as an essential, druggable target involved in the epigenetic regulation of gene expression

Good Health and Well-Being

Referring to the definition of sustainable tourism and taking into consideration the specifics of medical tourism, it can be assumed that sustainable medical tourism is a conscious and sustainable human activity, in which a medical tourist/mobile patient aims to obtain broadly understood healthcare outside their permanent place of residence (at home or abroad), consisting mainly in maintaining (obtaining better) health, and/or aesthetic appearance of one’s own body, often combined with rest and consumption of tourist packages. This balance should address all three aspects – social, economic, and environmental. Therefore, the provision of sustainable medical tourism services, most often by commercial healthcare entities, should be carried out with rational spatial distribution resulting in the strengthening of local economies and improving the quality of life of the society while respecting natural resources and using innovative solutions in the medical tourism business.11-15.Encyclopedia of the UN Sustainable Development Goals, ISSN : 2523-741

The development and testing of a diagnostic tool for assessing VAT compliance costs : pilot study findings

This article presents the findings of a pilot research project designed to evaluate the merits of a prototype diagnostic tool for gauging the nature and likely overall incidence of value added tax (VAT) compliance costs at the country level, and to assess its use in comparative cross-country assessments to promote reform. The project was conducted across 13 countries, representing a mix of advanced and developing economies from all continents.1 Drawing on feedback from participants in the project, the findings appear broadly aligned with community and government expectations, and participants were generally of the view that the tool displays merit in assessing the likely aggregate (or relative) VAT compliance burden and its main drivers. The VAT diagnostic tool survey undertaken as part of the pilot also sought to gather insights into the degree of government and institutional recognition and attention being given to address tax compliance costs as a means of gauging a sense of the ‘maturity’ of each country’s approach to compliance burden management, which was found to be weak in a number of the participating countries.https://www.business.unsw.edu.au/research/publications/atax-journalam2020Taxatio