Search

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 thesafety and efficacy gaps of the drugscurrently 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 theinitial screen (1 μM). Out of these compounds, nine showed > 70% inhibition, with median inhibitory concentration (IC 50) ranging from 12 to 491 nM using theanti-promastigote assay, and from 53 to 704 nM using theintracellular 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 usingthis 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 forMalaria Venture, drug discovery

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.

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. Electronic supplementary material The online version of this article (10.1186/s12936-019-2642-0) contains supplementary material, which is available to authorized users.

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 3 H-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.

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. Ministry of Education (MOE) Published version A.T.P., G.S., and R.C. acknowledge the following grants: RGAST1503 (A*star-India Collaboration grant) and T1MOE1702 (a Ministry of Education [MoE] Tier 1grant awarded through SUTD). A.T.P. acknowledges the MoE, Singapore, for a president’s graduate fellowship. The infrastructure support provided through the SUTD-MIT International Design Centre (IDC) is greatly acknowledged. M.A.B. and T.H. acknowledge Ph.D. fellowships from the Council of Scientific and Industrial Research, India; D.S.acknowledges the Indo-Singapore Joint Science and Technology Research Cooperationgrant from the Department of Science and Technology, India (grant INT/SIN/P-09/2015), and infrastructure support from the CSIR-National Chemical Laboratory, Pune, India.

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 thesafety and efficacy gaps of the drugscurrently 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 theinitial screen (1 μM). Out of these compounds, nine showed > 70% inhibition, with median inhibitory concentration (IC 50) ranging from 12 to 491 nM using theanti-promastigote assay, and from 53 to 704 nM using theintracellular 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 usingthis 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 forMalaria Venture, drug discovery

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 IC50 values of 0.78 and 0.61 μM, respectively, and CC50 values > 5 μM. The remaining compounds exhibited a high degree of toxicity (CC50 values 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.

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.