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We report a systematic, cellular phenotype-based antimalarial screening of the Medicines for Malaria Venture Pathogen Box collection, which facilitated the identification of specific blockers of late-stage intraerythrocytic development of Plasmodium falciparum First, from standard growth inhibition assays, we identified 173 molecules with antimalarial activity (50% effective concentration [EC50] ≤ 10 μM), which included 62 additional molecules over previously known antimalarial candidates from the Pathogen Box. We identified 90 molecules with EC50 of ≤1 μM, which had significant effect on the ring-trophozoite transition, while 9 molecules inhibited the trophozoite-schizont transition and 21 molecules inhibited the schizont-ring transition (with ≥50% parasites failing to proceed to the next stage) at 1 μM. We therefore rescreened all 173 molecules and validated hits in microscopy to prioritize 12 hits as selective blockers of the schizont-ring transition. Seven of these molecules inhibited the calcium ionophore-induced egress of Toxoplasma gondii, a related apicomplexan parasite, suggesting that the inhibitors may be acting via a conserved mechanism which could be further exploited for target identification studies. We demonstrate that two molecules, MMV020670 and MMV026356, identified as schizont inhibitors in our screens, induce the fragmentation of DNA in merozoites, thereby impairing their ability to egress and invade. Further mechanistic studies would facilitate the therapeutic exploitation of these molecules as broadly active inhibitors targeting late-stage development and egress of apicomplexan parasites relevant to human health.

The emergence of drug-resistant malaria parasites to artemisinin and its partner drugs highlights the need to increase the arsenal of new antimalarials with novel mechanisms of action. To help achieve this aim, this study tested the potency of three Malaria Box compounds (MMV006087, MMV085203, and MMV008956) against five laboratory strains and twenty clinical isolates of Plasmodium falciparum using optimized in vitro growth inhibitory assays. The results were compared to the response from four standard antimalarials-artesunate, chloroquine, mefloquine, and halofantrine. From the results, MMV006087 was the most potent compound with an average IC50 of 22.13 nM compared to MMV085203 (average IC50 of 137.90 nM) and MMV008956 (average IC50 of 262.30 nM). On average, the laboratory strains were also less susceptible to the three Malaria Box compounds (average IC50 of 162.30 nM) compared to the clinical isolates (average IC50 of 135.40 nM). Additionally, MMV006087 was less potent than artesunate but twice more efficacious than chloroquine against the laboratory strains and clinical isolates. The data from this study validate the potency of MMV006087 and MMV085203 as promising antimalarials worthy of further exploration. This study further substantiates the need to include clinical isolates in antimalarial compound screening activities.

The increase in the prevalence and severity of fungal infections and the resistance to available antifungals highlights the imperative need for novel therapeutics and the search for new targets. High-content screening of libraries containing hundreds of compounds is a powerful strategy for searching for new drug candidates. In this study, we screened the Pandemic Response Box library (Medicines for Malaria Venture) of 400 diverse molecules against the Sporothrix pathogenic species. The initial screen identified twenty-four candidates that inhibited the growth of Sporothrix brasiliensis by more than 80%. Some of these compounds are known to display antifungal activity, including olorofim (MMV1782354), a new antifungal drug. Olorofim inhibited and killed the yeasts of S. brasiliensis, S. schenckii, and S. globosa at concentrations lower than itraconazole, and it also showed antibiofilm activity. According to the results obtained by fluorimetry, electron microscopy, and particle characterization analyses, we observed that olorofim induced profound alterations on the cell surface and cell cycle arrest in S. brasiliensis yeasts. We also verified that these morphophysiological alterations impaired their ability to adhere to keratinocytes in vitro. Our results indicate that olorofim is a promising new antifungal against sporotrichosis agents. [ABSTRACT FROM AUTHOR]

Markos Tadele, 1,* Solomon M Abay, 2,* Eyasu Makonnen, 2, 3 Asrat Hailu 3, 4 1Animal Health Research Program, Ethiopian Institute of Agricultural Research, Holetta, Ethiopia; 2Department of Pharmacology and Clinical Pharmacy, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia; 3Center for Innovative Drug Development and Therapeutic Trials for Africa (CDT Africa), College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia; 4Department of Microbiology, Immunology and Parasitology, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia*These authors contributed equally to this workCorrespondence: Solomon M Abay P.O. Box 9086, Addis Ababa, EthiopiaTel +251 941 22 2169Email solomonabay@gmail.comIntroduction: Leishmaniasis is a collective term used to describe various pathological conditions caused by an obligate intracellular protozoan of the genus Leishmania. It is one of the neglected diseases and has been given minimal attention by drug discovery and development stakeholders to narrow the safety and efficacy gaps of the drugs currently used to treat leishmaniasis. The challenge is further exacerbated by the emergence of drug resistance by the parasites.Methods: Aiming to look for potential anti-leishmanial hits and leads, we screened Medicines for Malaria Venture (MMV) Pathogen Box compounds against clinically isolated Leishmania donovani strain. In this medium-throughput primary screening assay, the compounds were screened against promastigotes, and then against amastigote stages.Results: From the total 400 compounds screened, 35 compounds showed > 50% inhibitory activity on promastigotes in the initial screen (1 μM). Out of these compounds, nine showed > 70% inhibition, with median inhibitory concentration (IC 50) ranging from 12 to 491 nM using the anti-promastigote assay, and from 53 to 704 nM using the intracellular amastigote assay. Identified compounds demonstrated acceptable safety profiles on THP-1 cell lines and sheep red blood cells, and had appropriate physicochemical properties suitable for further drug development. Two compounds (MMV690102 and MMV688262) were identified as leads. The anti-tubercular agent MMV688262 (delamanid) showed a synergistic effect with amphotericin B, indicating the prospect of using this compound for combination therapy.Conclusion: The current study indicates the presence of additional hits which may hold promise as starting points for anti-leishmanial drug discovery and in-depth structure–activity relationship studies.Keywords: Leishmania donovani, Pathogen Box compounds, Medicines for Malaria Venture, drug discovery

Abstract Background The erythrocytic stage of Plasmodium falciparum parasites in humans is clinically important, as the parasites at this growth stage causes malarial symptoms. Most of the currently available anti-malarial drugs target this stage, but the emergence and spread of parasites resistant to anti-malarial drugs are a major challenge to global eradication efforts; therefore, the development of novel medicines is urgently required. In this study, the in vitro anti-malarial activity of five current anti-malarial drugs (artemisinin, atovaquone, chloroquine, mefloquine, and pyrimethamine) and 400 compounds from the Pathogen Box provided by the Medicines for Malaria Venture on P. falciparum parasites was characterized using the XN-30 analyzer. Furthermore, the outcomes obtained using the analyser were classified according to the parasitaemias of total and each developmental stages. Results The growth inhibition rate and the half-maximal (50%) inhibitory concentration (IC50) of the five current anti-malarial drugs were calculated from the parasitaemia detected using the XN-30 analyzer. Respective strains and drugs presented strongly fitted sigmoidal curves, and the median SD at all tested concentrations was 1.6, suggesting that the variation in values measured with the analyser was acceptably low for the comparison of drug efficacy. Furthermore, the anti-malarial activity of the 400 compounds from the Pathogen Box was tested, and 141 drugs were found to be effective. In addition, the efficacy was classified into 4 types (Type I, parasites were arrested or killed without DNA replication; Type II, parasites were arrested or killed similar to Type I, and the parasitaemia was apparently decreased; Type III, parasites progressed to trophozoite without sufficient DNA replication; and Type IV, parasites were arrested at late trophozoite or schizont after DNA replication). Conclusion The current study demonstrates that the XN-30 analyzer objectively, reproducibly, and easily evaluated and characterized the anti-malarial efficacy of various compounds. The results indicate the potential of the XN-30 analyzer as a powerful tool for drug discovery and development in addition to its use as an important diagnostic tool.

Abstract Chemotherapy of East Coast fever, a lymphoproliferative cancer-like disease of cattle causing significant economic losses in Africa, is largely dependent on the use of buparvaquone, a drug that was developed in the late 1980's. The disease is caused by the tick-borne protozoan pathogen Theileria parva. Buparvaquone can be used prophylactically and it is also active against tropical theileriosis, caused by the related parasite Theileria annulata. Recently, drug resistance was reported in T. annulata , and could occur in T. parva. Using a 3H-thymidine incorporation assay we screened 796 open source compounds from the Medicines for Malaria Venture (MMV) to discover novel chemicals with potential inhibitory activity to T. parva. We identified nine malaria box compounds and eight pathogen box compounds that inhibited the proliferation of F100TpM, a T. parva infected lymphocyte cell line. However, only two compounds, MMV008212 and MMV688372 represent promising leads with IC 50 values of 0.78 and 0.61 μM, respectively, and CC 50 values > 5 μM. The remaining compounds exhibited a high degree of toxicity (CC 50 values < 1.09 μM) on the proliferation of bovine peripheral blood mononuclear cells stimulated with concanavalin A. We also tested the anti-cancer drug, dasatinib, used in the chemotherapy of some leukemias. Dasatinib was as active and safe as buparvaquone in vitro , with an IC 50 of 5 and 4.2 nM, respectively, and CC 50 > 10 μM. Our preliminary data suggest that it may be possible to repurpose compounds from the cancer field as well as MMV as novel anti- T. parva molecules. Graphical abstract Image 1 Highlights • 17 of 796 MMV compounds inhibited proliferation of T parva infected lymphocytes. • 15 of the 17 hit compounds also inhibited proliferation of control cells. • MMV008212 and MMV688372 represent promising leads, therapeutic index >8. • Dasatinib was as active and safe as buparvaquone in vitro, therapeutic index >2000. [ABSTRACT FROM AUTHOR]

ABSTRACT: BACKGROUND: To fight herbicide‐resistant weeds, new herbicides are needed; particularly ones with new modes of action. Building on the revelation that many antimalarial drugs are herbicidal, here we focus on the Medicines for Malaria Venture antimalarial lead compound MMV007978 that has herbicidal activity against the model plant Arabidopsis thaliana. RESULTS: Twenty‐two variations of the lead compound thiophenyl motif revealed that change was tolerated provided ring size and charge were retained. MMV007978 was active against select monocot and dicot weeds, and physiological profiling indicated that its mode of action is related to germination and cell division. Of interest is the fact that the compound has a profile that is currently not found among known herbicides. CONCLUSION: We demonstrate that the antimalarial compound MMV007978 is also herbicidal and that exploiting lead compounds that are often understudied could lead to the identification of interesting herbicidal scaffolds. Further structural investigation of MMV007978 could provide improved herbicidal chemistries with a potential new mode of action. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

[Display omitted] The development of resistance to current antimalarial therapies remains a significant source of concern. To address this risk, new drugs with novel targets in distinct developmental stages of Plasmodium parasites are required. In the current study, we have targeted P. falciparum Tubulin (Pf Tubulin) proteins which represent some of the potential drug targets for malaria chemotherapy. Plasmodial Microtubules (MTs) play a crucial role during parasite proliferation, growth, and transmission, which render them highly desirable targets for the development of next-generation chemotherapeutics. Towards this, we have evaluated the antimalarial activity of Tubulin targeting compounds received from the Medicines for Malaria Venture (MMV) "Pathogen Box" against the human malaria parasite, P. falciparum including 3D7 (chloroquine and artemisinin sensitive strain), RKL-9 (chloroquine-resistant strain), and R539T (artemisinin-resistant strain). At nanomolar concentrations, the filtered-out compounds exhibited pronounced multistage antimalarial effects across the parasite life cycle, including intra-erythrocytic blood stages, liver stage parasites, gametocytes, and ookinetes. Concomitantly, these compounds were found to impede male gamete ex-flagellation, thus showing their transmission-blocking potential. Target mining of these potent compounds, by combining in silico , biochemical and biophysical assays, implicated Pf Tubulin as their molecular target, which may possibly act by disrupting MT assembly dynamics by binding at the interface of α-βTubulin-dimer. Further, the promising ADME profile of the parent scaffold supported its consideration as a lead compound for further development. Thus, our work highlights the potential of targeting Pf Tubulin proteins in discovering and developing next-generation, multistage antimalarial agents against Multi-Drug Resistant (MDR) malaria parasites. [ABSTRACT FROM AUTHOR]

Summary: Traditional pharmaceutical research and development (R&D) strategy has failed to address the desperate need for new antimalarial drugs. The populations affected are too poor to attract commercially-driven R&D. Over the last few years, a new model, the public-private partnership for product development, has radically changed the antimalarial R&D landscape. The partnerships bring together academic and industry expertise with funding from governmental, philanthropic and charitable sources. The Medicines for Malaria Venture, a not-for-profit foundation based in Geneva, aims to develop new antimalarials for developing countries through public-private partnership. It is currently managing a portfolio of around 20 projects at various stages of development. However, as in all drug R&D, some of these projects will fail. The portfolio approach helps to maximize the chances of success, but there are obvious challenges, including financial and managerial ones. Proactive management of the two vital interfaces in the drug supply chain is important for success. Upstream, basic research must be aligned with translational research in order to ensure a continuous supply of leads into the development pipeline. Meanwhile, downstream, drug discovery and development must be aligned with access to ensure optimal health impact. All stages require partnership, sustainable financing and the engagement of disease-endemic countries. The recent G8 report on Africa has lent support to mechanisms aimed at improving health and achieving the Millenium Development Goals. [Copyright &y& Elsevier]

Summary: Major changes in research and development (R&D) for drugs to treat tropical and neglected diseases have occurred in the past five years. Public-private partnerships for product development (PD PPPs) have emerged since rising drug development costs pushed pharmaceutical companies out of R&D for these diseases of the developing world and are now having an impact on the discovery and development of new medicines to treat them. PD PPPs can be an efficient model for bridging the translational research gap between basic research and clinical development by bringing together expertise from academia, the pharmaceutical industry and the public sector. Sustainability of funding is a serious problem. At present, one or two key philanthropic organisations provide a large proportion of the funding. Drug development typically takes 10 years and only 10 per cent of initial projects make it into the clinic. The partnerships need to widen their funding base and ensure that the funders understand the high level of attrition. Public-private partnerships have proved that they can move compounds quickly through the R&D pipeline. The challenge is to ensure that the products are delivered to the people who need them and to ensure that scientists in endemic countries are involved in the whole process. [Copyright &y& Elsevier]

Background: The erythrocytic stage of Plasmodium falciparum parasites in humans is clinically important, as the parasites at this growth stage causes malarial symptoms. Most of the currently available anti-malarial drugs target this stage, but the emergence and spread of parasites resistant to anti-malarial drugs are a major challenge to global eradication efforts; therefore, the development of novel medicines is urgently required. In this study, the in vitro anti-malarial activity of five current anti-malarial drugs (artemisinin, atovaquone, chloroquine, mefloquine, and pyrimethamine) and 400 compounds from the Pathogen Box provided by the Medicines for Malaria Venture on P. falciparum parasites was characterized using the XN-30 analyzer. Furthermore, the outcomes obtained using the analyser were classified according to the parasitaemias of total and each developmental stages. Results: The growth inhibition rate and the half-maximal (50%) inhibitory concentration (IC50) of the five current anti-malarial drugs were calculated from the parasitaemia detected using the XN-30 analyzer. Respective strains and drugs presented strongly fitted sigmoidal curves, and the median SD at all tested concentrations was 1.6, suggesting that the variation in values measured with the analyser was acceptably low for the comparison of drug efficacy. Furthermore, the anti-malarial activity of the 400 compounds from the Pathogen Box was tested, and 141 drugs were found to be effective. In addition, the efficacy was classified into 4 types (Type I, parasites were arrested or killed without DNA replication; Type II, parasites were arrested or killed similar to Type I, and the parasitaemia was apparently decreased; Type III, parasites progressed to trophozoite without sufficient DNA replication; and Type IV, parasites were arrested at late trophozoite or schizont after DNA replication). Conclusion: The current study demonstrates that the XN-30 analyzer objectively, reproducibly, and easily evaluated and characterized the anti-malarial efficacy of various compounds. The results indicate the potential of the XN-30 analyzer as a powerful tool for drug discovery and development in addition to its use as an important diagnostic tool. [ABSTRACT FROM AUTHOR]

The Pathogen Box is a 400-strong collection of drug-like compounds, selected for their potential against several of the world's most important neglected tropical diseases, including trypanosomiasis, leishmaniasis, cryptosporidiosis, toxoplasmosis, filariasis, schistosomiasis, dengue virus and trichuriasis, in addition to malaria and tuberculosis. This library represents an ensemble of numerous successful drug discovery programmes from around the globe, aimed at providing a powerful resource to stimulate open source drug discovery for diseases threatening the most vulnerable communities in the world. This review seeks to provide an in-depth analysis of the literature pertaining to the compounds in the Pathogen Box, including structure-activity relationship highlights, mechanisms of action, related compounds with reported activity against different diseases, and, where appropriate, discussion on the known and putative targets of compounds, thereby providing context and increasing the accessibility of the Pathogen Box to the drug discovery community., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Toxoplasma gondii is a common zoonotic infection of humans, and estimates indicate that 1-2 billion people are chronically infected. Although largely asymptomatic, chronic infection poses risk of serious disease due to reactivation should immunity decline. Current therapies for toxoplasmosis only control acute infection caused by actively proliferating tachyzoites but do not eradicate the chronic tissue cyst stages. As well, there are considerable adverse side effects of the most commonly used therapy of combined sulfadiazine and pyrimethamine. Targeting the folate pathway is also an effective treatment for malaria, caused by the related parasites Plasmodium spp., suggesting common agents might be used to treat both infections. Here, we evaluated currently approved and newly emerging medicines for malaria to determine if such compounds might also prove useful for treating toxoplasmosis. Surprisingly, the majority of antimalarial compounds being used currently or in development for treatment of malaria were only modestly effective at inhibiting in vitro growth of T. gondii tachyzoites. These findings suggest that many essential processes in P. falciparum that are targeted by antimalarial compounds are either divergent or nonessential in T. gondii, thus limiting options for repurposing of current antimalarial medicines for toxoplasmosis.

Background: To fight herbicide-resistant weeds, new herbicides are needed; particularly ones with new modes of action. Building on the revelation that many antimalarial drugs are herbicidal, here we focus on the Medicines for Malaria Venture antimalarial lead compound MMV007978 that has herbicidal activity against the model plant Arabidopsis thaliana., Results: Twenty-two variations of the lead compound thiophenyl motif revealed that change was tolerated provided ring size and charge were retained. MMV007978 was active against select monocot and dicot weeds, and physiological profiling indicated that its mode of action is related to germination and cell division. Of interest is the fact that the compound has a profile that is currently not found among known herbicides., Conclusion: We demonstrate that the antimalarial compound MMV007978 is also herbicidal and that exploiting lead compounds that are often understudied could lead to the identification of interesting herbicidal scaffolds. Further structural investigation of MMV007978 could provide improved herbicidal chemistries with a potential new mode of action. © 2018 Society of Chemical Industry., (© 2018 Society of Chemical Industry.)

To cope with growing resistance to current antimalarials, new drugs with novel modes of action are urgently needed. Molecules targeting protein synthesis appear to be promising candidates. We identified a compound (MMV665909) from the Medicines for Malaria Venture (MMV) Malaria Box of candidate antimalarials that could produce synergistic growth inhibition with the aminoglycoside antibiotic paromomycin, suggesting a possible action of the compound in mRNA mistranslation. This mechanism of action was substantiated with a Saccharomyces cerevisiae model using available reporters of mistranslation and other genetic tools. Mistranslation induced by MMV665909 was oxygen dependent, suggesting a role for reactive oxygen species (ROS). Overexpression of Rli1 (a ROS-sensitive, conserved FeS protein essential in mRNA translation) rescued inhibition by MMV665909, consistent with the drug's action on translation fidelity being mediated through Rli1. The MMV drug also synergized with major quinoline-derived antimalarials which can perturb amino acid availability or promote ROS stress: chloroquine, amodiaquine, and primaquine. The data collectively suggest translation fidelity as a novel target of antimalarial action and support MMV665909 as a promising drug candidate., (Copyright © 2017 Vallières and Avery.)

Rapid triaging of three series of related hits selected from the Tres Cantos Anti-Malarial Set (TCAMS) are described. A triazolopyrimidine series was deprioritized due to delayed inhibition of parasite growth. A lactic acid series has derivatives with IC50 < 500 nM in a standard Plasmodium falciparum in vitro whole cell assay (Pf assay) but shows half-lives of < 30 min in both human and murine microsomes. Compound 19, from a series of cyclopropyl carboxamides, is a highly potent in vitro inhibitor of P. falciparum (IC50 = 3 nM) and has an oral bioavailability of 55% in CD-1 mice and an ED90 of 20 mg/kg after oral dosing in a nonmyelo-depleted P. falciparum murine model.