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An Antiparasitic Compound from the Medicines for Malaria Venture Pathogen Box Promotes Leishmania Tubulin Polymerization.

ABSTRACT: The few frontline antileishmanial drugs are poorly effective and toxic. To search for new drugs for this neglected tropical disease, we tested the activity of compounds in the Medicines for Malaria Venture (MMV) "Pathogen Box" against Leishmania amazonensis axenic amastigotes. Screening yielded six discovery antileishmanial compounds with EC₅₀ values from 50 to 480 nM. Concentration-response assays demonstrated that the best hit, MMV676477, had mid-nanomolar cytocidal potency against intracellular Leishmania amastigotes, Trypanosoma brucei, and Plasmodium falciparum, suggesting broad antiparasitic activity. We explored structure-activity relationships (SAR) within a small group of MMV676477 analogs and observed a wide potency range (20-5000 nM) against axenic Leishmania amastigotes. Compared to MMV676477, our most potent analog, SW41, had ∼5-fold improved antileishmanial potency. Multiple lines of evidence suggest that MMV676477 selectively disrupts Leishmania tubulin dynamics. Morphological studies indicated that MMV676477 and analogs affected L. amazonensis during cell division. Differential centrifugation showed that MMV676477 promoted partitioning of cellular tubulin toward the polymeric form in parasites. Turbidity assays with purified Leishmania and porcine tubulin demonstrated that MMV676477 promoted leishmanial tubulin polymerization in a concentration-dependent manner. Analogs' antiparasitic activity correlated with their ability to facilitate purified Leishmania tubulin polymerization. Chemical cross-linking demonstrated binding of the MMV676477 scaffold to purified Leishmania tubulin, and competition studies established a correlation between binding and antileishmanial activity. Our studies demonstrate that MMV676477 is a potent antiparasitic compound that preferentially promotes Leishmania microtubule polymerization. Due to its selectivity for and broad-spectrum activity against multiple parasites, this scaffold shows promise for antiparasitic drug development.

SUBMITTER: Ullah I

PROVIDER: S-EPMC8059355 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:IntroductionLeishmania aethiopica (L. aethiopica) is responsible for different forms of cutaneous leishmaniasis (CL) in Ethiopia. Treatment heavily depends on limited drugs, together with drawbacks like toxicity and microbial resistance. The current research aimed to investigate in vitro growth inhibitory activity of Medicines for Malaria Ventures - Pathogen Box (MMV - PB) compounds against L. aethiopica clinical isolate.MethodologyFour hundred MMV - PB compounds were screened against L. aethiopica using resazurin based colourimetric assay. Compounds with > 70% inhibition were further tested using macrophage based intracellular amastigote assay. Cytotoxic and hemolytic activity of candidate hits were assessed on THP1- cells and sheep red blood cells (RBCs), respectively. In vitro drug interaction study was also conducted for the most potent hit using the combination index method.ResultsAt the test concentration of 1 μM, twenty-three compounds showed > 50% inhibition of promastigotes parasite growth, of which 11 compounds showed > 70% inhibition. The 50% growth inhibition (IC50) of the 11 compounds was ranged from 0.024 to 0.483 μM in anti-promastigote assay and from 0.064 to 0.899 μM in intracellular amastigote assay. Candidate compounds demonstrated good safety on sheep RBCs and THP-1 cell lines. MMV688415 demonstrated a slight hemolytic activity on sheep RBC (5.3% at 25 μM) and THP-1 cell line (CC20 = 25 μM) while MMV690102 inhibited half of THP-1 cells at 36.5 μM (selectivity index = 478). No synergistic activity was observed from the combinations of MMV690102 and amphotericin B (CI > 1), and MMV690102 and Pentamidine (CI > 1) at lower and higher combination points.ConclusionThe present study identified a panel of compounds that can be used as a novel starting point for lead optimization. MMV690102 appears to be the most potent inhibitor against L. aethiopica promastigotes and amastigotes. Future works should investigate the antileishmanial mechanism of action and in vivo antileishmanial activities of identified hits.

Project description:Diminazene aceturate (DA) and imidocarb dipropionate are commonly used in livestock as antipiroplasm agents. However, toxic side effects are common in animals treated with these two drugs. Therefore, evaluations of novel therapeutic agents with high efficacy against piroplasm parasites and low toxicity to host animals are of paramount importance. In this study, the 400 compounds in the Pathogen Box provided by the Medicines for Malaria Venture foundation were screened against Babesia bovis, Babesia bigemina, Babesia caballi, and Theileria equi. A fluorescence-based method using SYBR Green 1 stain was used for initial in vitro screening and determination of the half maximal inhibitory concentration (IC50). The initial in vitro screening performed using a 1 μM concentration as baseline revealed nine effective compounds against four tested parasites. Two "hit" compounds, namely MMV021057 and MMV675968, that showed IC50 < 0.3 μM and a selectivity index (SI)> 100 were selected. The IC50s of MMV021057 and MMV675968 against B. bovis, B. bigemina, T. equi and B. caballi were 23, 39, 229, and 146 nM, and 2.9, 3, 25.7, and 2.9 nM, respectively. In addition, a combination of MMV021057 and DA showed additive or synergistic effects against four tested parasites, while combinations of MMV021057 with MMV675968 and of MMV675968 with DA showed antagonistic effects. In mice, treated with 50 mg/kg MMV021057 and 25 mg/kg MMV675968 inhibited the growth of Babesia microti by 54 and 64%, respectively, as compared to the untreated group on day 8. Interestingly, a combination treatment with 6.25 mg/kg DA and 25 mg/kg MMV021057 inhibited B. microti by 91.6%, which was a stronger inhibition than that by single treatments with 50 mg/kg MMV021057 and 25 mg/kg DA, which showed 54 and 83% inhibition, respectively. Our findings indicated that MMV021057, MMV675968, and the combination treatment with MMV021057 and DA are prospects for further development of antipiroplasm drugs.

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An Antiparasitic Compound from the Medicines for Malaria Venture Pathogen Box Promotes Leishmania Tubulin Polymerization.

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