Browsing by Author "Waterson, David"

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    Open Access
    Fast in vitro methods to determine the speed of action and the stage-specificity of anti-malarials in Plasmodium falciparum
    (BioMed Central Ltd, 2013) Le Manach, Claire; Scheurer, Christian; Sax, Sibylle; Schleiferbock, Sarah; Cabrera, Diego; Younis, Yassir; Paquet, Tanya; Street, Leslie; Smith, Peter; Ding, Xavier; Waterson, David; Witty, Michael; Leroy, Didier; Chibale, Kelly; Wittlin, Sergio
    BACKGROUND: Recent whole cell in vitro screening campaigns identified thousands of compounds that are active against asexual blood stages of Plasmodium falciparum at submicromolar concentrations. These hits have been made available to the public, providing many novel chemical starting points for anti-malarial drug discovery programmes. Knowing which of these hits are fast-acting compounds is of great interest. Firstly, a fast action will ensure rapid relief of symptoms for the patient. Secondly, by rapidly reducing the parasitaemia, this could minimize the occurrence of mutations leading to new drug resistance mechanisms.An in vitro assay that provides information about the speed of action of test compounds has been developed by researchers at GlaxoSmithKline (GSK) in Spain. This assay also provides an in vitro measure for the ratio between parasitaemia at the onset of drug treatment and after one intra-erythrocytic cycle (parasite reduction ratio, PRR). Both parameters are needed to determine in vitro killing rates of anti-malarial compounds. A drawback of the killing rate assay is that it takes a month to obtain first results. METHODS: The approach described in the present study is focused only on the speed of action of anti-malarials. This has the advantage that initial results can be achieved within 4-7 working days, which helps to distinguish between fast and slow-acting compounds relatively quickly. It is expected that this new assay can be used as a filter in the early drug discovery phase, which will reduce the number of compounds progressing to secondary, more time-consuming assays like the killing rate assay. RESULTS: The speed of action of a selection of seven anti-malarial compounds was measured with two independent experimental procedures using modifications of the standard [3H]hypoxanthine incorporation assay. Depending on the outcome of both assays, the tested compounds were classified as either fast or non-fast-acting. CONCLUSION: The results obtained for the anti-malarials chloroquine, artesunate, atovaquone, and pyrimethamine are consistent with previous observations, suggesting the methodology is a valid way to rapidly identify fast-acting anti-malarial compounds. Another advantage of the approach is its ability to discriminate between static or cidal compound effects.
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    Identification of Plasmodium PI4 kinase as target of MMV390048 by chemoproteomics
    (BioMed Central Ltd, 2014) Ghidelli-Disse, Sonja; Lafuente-Monasterio, Maria; Waterson, David; Witty, Michael; Younis, Yassir; Paquet, Tanya; Street, Leslie; Chibale, Kelly; Gamo-Benito, Francisco; Bantscheff, Marcus; Drewes, Gerard
    Most antimalarial drugs face decreased efficacy due to the emergence of resistant parasites. Therefore, the discovery of new antimalarial medicines is focused on new drugs that act by novel mechanisms and are active against different P. falciparum development stages. Screening of a focused compound library for antiparasitic activity, lead to identification of a novel class of compounds with activity against P. falciparum, 2-aminopyridines. The selected hits were validated and subjected to a lead optimization program resulting in the pre-clinical candidate MMV390048. Here we report an unbiased chemoproteomics strategy for the identification of targets of MMV390048.