ORCID Profile
0000-0002-4049-2113
Current Organisation
University of California, San Diego
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Publisher: Springer Science and Business Media LLC
Date: 18-09-2018
DOI: 10.1038/S41467-018-05777-2
Abstract: Spread of parasite resistance to artemisinin threatens current frontline antimalarial therapies, highlighting the need for new drugs with alternative modes of action. Since only 0.2–1% of asexual parasites differentiate into sexual, transmission-competent forms, targeting this natural bottleneck provides a tangible route to interrupt disease transmission and mitigate resistance selection. Here we present a high-throughput screen of gametogenesis against a ~70,000 compound ersity library, identifying seventeen drug-like molecules that target transmission. Hit molecules possess varied activity profiles including male-specific, dual acting male–female and dual-asexual-sexual, with one promising N -((4-hydroxychroman-4-yl)methyl)-sulphonamide scaffold found to have sub-micromolar activity in vitro and in vivo efficacy. Development of leads with modes of action focussed on the sexual stages of malaria parasite development provide a previously unexplored base from which future therapeutics can be developed, capable of preventing parasite transmission through the population.
Publisher: Hindawi Limited
Date: 05-04-2013
DOI: 10.1111/CMI.12137
Publisher: Public Library of Science (PLoS)
Date: 30-11-2017
Publisher: Springer Science and Business Media LLC
Date: 15-06-2016
DOI: 10.1038/NCOMMS11901
Abstract: Microbial resistance to chemotherapy has caused countless deaths where malaria is endemic. Chemotherapy may fail either due to pre-existing resistance or evolution of drug-resistant parasites. Here we use a erse set of antimalarial compounds to investigate the acquisition of drug resistance and the degree of cross-resistance against common resistance alleles. We assess cross-resistance using a set of 15 parasite lines carrying resistance-conferring alleles in pfatp4 , cytochrome bc 1 , pfcarl , pfdhod, pfcrt , pfmdr, pfdhfr, cytoplasmic prolyl t-RNA synthetase or hsp90 . Subsequently, we assess whether resistant parasites can be obtained after several rounds of drug selection. Twenty-three of the 48 in vitro selections result in resistant parasites, with time to resistance onset ranging from 15 to 300 days. Our data indicate that pre-existing resistance may not be a major hurdle for novel-target antimalarial candidates, and focusing our attention on fast-killing compounds may result in a slower onset of clinical resistance.
Publisher: Elsevier BV
Date: 10-2018
Publisher: Springer Science and Business Media LLC
Date: 02-10-2018
DOI: 10.1038/S42004-018-0062-7
Abstract: The quinolone decoquinate is coadministered with feed for treatment of parasites which cause coccidiosis in poultry. However, from a drug-development perspective, the biological activity is often not adequately exploited due to poor physicochemical properties. Here we convert decoquinate into N -alkyl quinolone amides that, in contrast to decoquinate, are active against the tuberculosis bacterium with MIC 90 values ranging from 1.4 to 3.64 µM, and quinoline O -carbamates active against apicomplexan parasites that cause malaria, toxoplasmosis, and neosporosis with IC 50 values of 0.32–1.5 nM for the best derivative. Uniquely for the TB-active amides, disruption of cell wall homoeostasis is identified as one target. With IC 50 values against fetal lung fibroblast cells of 40 to μM, the derivatives are selective for the pathogens. Structures of the most active derivatives are determined by NMR spectroscopy and X-ray crystallography. Analogues lacking the decyl side chain of decoquinate are inactive.
Publisher: Elsevier BV
Date: 06-2002
DOI: 10.1016/S1471-4922(02)02268-7
Abstract: Among the leading causes of death in African children is cerebral malaria caused by the parasitic protozoan Plasmodium falciparum. Endemic forms of this disease are thought to have originated in central Africa 5000-10000 years ago, coincident with the innovation of slash-and-burn agriculture and the ersification of the Anopheles gambiae complex of mosquito vectors. Population genetic studies of P. falciparum have yielded conflicting results. Some evidence suggests that today's population includes multiple ancient lineages pre-dating human speciation. Other evidence suggests that today's population derives from only one, or a small number, of these ancient lineages. Resolution of this issue is important for the evaluation of the long-term efficacy of drug and immunological control strategies.
Publisher: American Society for Microbiology
Date: 08-2011
DOI: 10.1128/AAC.01793-10
Abstract: The combination of piperaquine and dihydroartemisinin has recently become the official first-line therapy in several Southeast Asian countries. The pharmacokinetic mismatching of these drugs, whose plasma half-lives are ∼20 days and ∼1 h, respectively, implies that recrudescent or new infections emerging shortly after treatment cessation will encounter piperaquine as a monotherapy agent. This creates substantial selection pressure for the emergence of resistance. To elucidate potential resistance determinants, we subjected cloned Plasmodium falciparum Dd2 parasites to continuous piperaquine pressure in vitro (47 nM ∼2-fold higher than the Dd2 50% inhibitory concentration [IC 50 ]). The phenotype of outgrowth parasites was assayed in two clones, revealing an IC 50 against piperaquine of 2.1 μM and 1.7 μM, over 100-fold greater than that of the parent. To identify the genetic determinant of resistance, we employed comparative whole-genome hybridization analysis. Compared to the Dd2 parent, this analysis found (in both resistant clones) a novel single-nucleotide polymorphism in P. falciparum crt ( pfcrt ), de lification of an 82-kb region of chromosome 5 (that includes pfmdr1 ), and lification of an adjacent 63-kb region of chromosome 5. Continued propagation without piperaquine selection pressure resulted in “revertant” piperaquine-sensitive parasites. These retained the pfcrt polymorphism and further de lified the chromosome 5 segment that encompasses pfmdr1 however, these two independently generated revertants both lost the neighboring 63-kb lification. These results suggest that a copy number variation event on chromosome 5 (825600 to 888300) is associated with piperaquine resistance. Transgene expression studies are underway with in idual genes in this segment to evaluate their contribution to piperaquine resistance.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 30-08-2019
Abstract: Malaria elimination goals are constantly eroded by the challenge of emerging drug and insecticide resistance. Alam et al. have taken established drug targets—CLK protein kinases involved in regulation of RNA splicing—and investigated how inhibition of the parasite's enzymes blocks completion of its complex life cycle. They identified an inhibitor of the parasite's CLK protein kinase that was 100-fold less active against the most closely related human protein kinase and effective at clearing rodent malaria parasites. Not only does this compound halt the development of sexual stages but it also limits transmission to the mosquito vector of the parasite, a key requirement for malaria drugs. Science , this issue p. eaau1682
Publisher: American Chemical Society (ACS)
Date: 20-02-2020
Publisher: American Chemical Society (ACS)
Date: 28-02-2023
Publisher: Public Library of Science (PLoS)
Date: 28-07-2016
Publisher: American Association for the Advancement of Science (AAAS)
Date: 12-01-2018
Abstract: Malaria is a deadly disease with no effective vaccine. Physicians thus depend on antimalarial drugs to save lives, but such compounds are often rendered ineffective when parasites evolve resistance. Cowell et al. systematically studied patterns of Plasmodium falciparum genome evolution by analyzing the sequences of clones that were resistant to erse antimalarial compounds across the P. falciparum life cycle (see the Perspective by Carlton). The findings identify hitherto unrecognized drug targets and drug-resistance genes, as well as additional alleles in known drug-resistance genes. Science , this issue p. 191 see also p. 159
Publisher: Public Library of Science (PLoS)
Date: 07-02-2013
Publisher: Wiley
Date: 07-05-2016
DOI: 10.1111/MMI.13397
Publisher: Frontiers Media SA
Date: 10-01-2020
Publisher: Springer Science and Business Media LLC
Date: 31-08-2023
Publisher: Wiley
Date: 03-07-2019
Publisher: Proceedings of the National Academy of Sciences
Date: 21-09-2021
Abstract: Here, we describe inhibitors of the Plasmodium proteasome, an enzymatic complex that malaria parasites rely on to degrade proteins. Starting from inhibitors developed to treat cancer, derivatives were designed and synthesized with the aim of increasing potency against the Plasmodium proteasome and decreasing activity against the human enzyme. Biochemical and cellular assays identified compounds that exhibit selectivity and potency, both in vitro and in vivo, at different stages of the parasite’s lifecycle. Cryo-electron microscopy revealed that the inhibitors bind in a hydrophobic pocket that is structurally different in the human proteasome—underpinning their selectivity. The work will help develop antimalarial therapeutics, which are desperately needed to treat a disease that kills nearly half a million people annually.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Springer Science and Business Media LLC
Date: 07-09-2016
DOI: 10.1038/NATURE19804
Publisher: Cold Spring Harbor Laboratory
Date: 12-02-2003
DOI: 10.1101/GR.541303
Abstract: We have developed a high-throughput genotyping platform by hybridizing genomic DNA from Arabidopsis thaliana accessions to an RNA expression GeneChip (AtGenome1). Using newly developed analytical tools, a large number of single-feature polymorphisms (SFPs) were identified. A comparison of two accessions, the reference strain Columbia (Col) and the strain Landsberg erecta (L er ), identified nearly 4000 SFPs, which could be reliably scored at a 5% error rate. L er sequence was used to confirm 117 of 121 SFPs and to determine the sensitivity of array hybridization. Features containing sequence repeats, as well as those from high copy genes, showed greater polymorphism rates. A linear clustering algorithm was developed to identify clusters of SFPs representing potential deletions in 111 genes at a 5% false discovery rate (FDR). Among the potential deletions were transposons, disease resistance genes, and genes involved in secondary metabolism. The applicability of this technique was demonstrated by genotyping a recombinant inbred line. Recombination break points could be clearly defined, and in one case delimited to an interval of 29 kb. We further demonstrate that array hybridization can be combined with bulk segregant analysis to quickly map mutations. The extension of these tools to organisms with complex genomes, such as Arabidopsis , will greatly increase our ability to map and clone quantitative trait loci (QTL). [Supplemental material is available online at www.genome.org .]
Publisher: American Chemical Society (ACS)
Date: 29-10-2018
Publisher: Rockefeller University Press
Date: 28-06-2010
DOI: 10.1084/JEM.20091975
Abstract: Sporozoites, the invasive form of malaria parasites transmitted by mosquitoes, are quiescent while in the insect salivary glands. Sporozoites only differentiate inside of the hepatocytes of the mammalian host. We show that sporozoite latency is an active process controlled by a eukaryotic initiation factor-2α (eIF2α) kinase (IK2) and a phosphatase. IK2 activity is dominant in salivary gland sporozoites, leading to an inhibition of translation and accumulation of stalled mRNAs into granules. When sporozoites are injected into the mammalian host, an eIF2α phosphatase removes the PO4 from eIF2α-P, and the repression of translation is alleviated to permit their transformation into liver stages. In IK2 knockout sporozoites, eIF2α is not phosphorylated and the parasites transform prematurely into liver stages and lose their infectivity. Thus, to complete their life cycle, Plasmodium sporozoites exploit the mechanism that regulates stress responses in eukaryotic cells.
Publisher: Elsevier BV
Date: 06-2021
Publisher: American Society for Microbiology
Date: 09-2014
DOI: 10.1128/AAC.02727-13
Abstract: Renewed global efforts toward malaria eradication have highlighted the need for novel antimalarial agents with activity against multiple stages of the parasite life cycle. We have previously reported the discovery of a novel class of antimalarial compounds in the imidazolopiperazine series that have activity in the prevention and treatment of blood stage infection in a mouse model of malaria. Consistent with the previously reported activity profile of this series, the clinical candidate KAF156 shows blood schizonticidal activity with 50% inhibitory concentrations of 6 to 17.4 nM against P. falciparum drug-sensitive and drug-resistant strains, as well as potent therapeutic activity in a mouse models of malaria with 50, 90, and 99% effective doses of 0.6, 0.9, and 1.4 mg/kg, respectively. When administered prophylactically in a sporozoite challenge mouse model, KAF156 is completely protective as a single oral dose of 10 mg/kg. Finally, KAF156 displays potent Plasmodium transmission blocking activities both in vitro and in vivo . Collectively, our data suggest that KAF156, currently under evaluation in clinical trials, has the potential to treat, prevent, and block the transmission of malaria.
Publisher: American Chemical Society (ACS)
Date: 17-06-2016
Publisher: Cold Spring Harbor Laboratory
Date: 17-10-2022
DOI: 10.1101/2022.10.16.512381
Abstract: Current malaria treatments are threatened by drug resistance and new drugs are urgently needed. In a phenotypic screen for new antimalarials, we identified ( S )-SW228703 (( S )-SW703), a tyrosine amide with asexual blood and liver stage activity and a fast-killing profile. Resistance to ( S )-SW703 is associated with mutations in Plasmodium falciparum cyclic amine resistance locus ( Pf CARL) and P. falciparum acetyl CoA transporter ( Pf ACT), similarly to several other compounds that share features such as fast activity and liver-stage activity. Compounds with these resistance mechanisms are thought to act in the ER, though their target(s) are unknown. The tyramine of ( S )-SW703 is shared with some reported Pf CARL-associated compounds however, we observed that strict S-stereochemistry was required for activity of ( S )-SW703, suggesting differences in mechanism of action or binding mode. ( S )-SW703 provides a new chemical series with broad activity on multiple life-cycle stages and a fast-killing mechanism of action, available for lead optimization to generate new treatments for malaria.
Publisher: Elsevier BV
Date: 08-2018
Publisher: Springer Science and Business Media LLC
Date: 03-05-2019
DOI: 10.1038/S42003-019-0397-3
Abstract: Atovaquone-proguanil (Malarone®) is used for malaria prophylaxis and treatment. While the cytochrome bc1-inhibitor atovaquone has potent activity, proguanil’s action is attributed to its cyclization-metabolite, cycloguanil. Evidence suggests that proguanil has limited intrinsic activity, associated with mitochondrial-function. Here we demonstrate that proguanil, and cyclization-blocked analogue tBuPG, have potent, but slow-acting, in vitro anti-plasmodial activity. Activity is folate-metabolism and isoprenoid biosynthesis-independent. In yeast dihydroorotate dehydrogenase-expressing parasites, proguanil and tBuPG slow-action remains, while bc1-inhibitor activity switches from comparatively fast to slow-acting. Like proguanil, tBuPG has activity against P. berghei liver-stage parasites. Both analogues act synergistically with bc1-inhibitors against blood-stages in vitro, however cycloguanil antagonizes activity. Together, these data suggest that proguanil is a potent slow-acting anti-plasmodial agent, that bc1 is essential to parasite survival independent of dihydroorotate dehydrogenase-activity, that Malarone® is a triple-drug combination that includes antagonistic partners and that a cyclization-blocked proguanil may be a superior combination partner for bc1-inhibitors in vivo.
Publisher: Springer Science and Business Media LLC
Date: 14-08-2017
Publisher: American Chemical Society (ACS)
Date: 15-09-2021
Publisher: Springer Science and Business Media LLC
Date: 16-03-2023
DOI: 10.1038/S41467-023-36921-2
Abstract: Identifying how small molecules act to kill malaria parasites can lead to new “chemically validated” targets. By pressuring Plasmodium falciparum asexual blood stage parasites with three novel structurally-unrelated antimalarial compounds (MMV665924, MMV019719 and MMV897615), and performing whole-genome sequence analysis on resistant parasite lines, we identify multiple mutations in the P. falciparum acyl-CoA synthetase (ACS) genes Pf ACS10 (PF3D7_0525100, M300I, A268D/V, F427L) and Pf ACS11 (PF3D7_1238800, F387V, D648Y, and E668K). Allelic replacement and thermal proteome profiling validates Pf ACS10 as a target of these compounds. We demonstrate that this protein is essential for parasite growth by conditional knockdown and observe increased compound susceptibility upon reduced expression. Inhibition of Pf ACS10 leads to a reduction in triacylglycerols and a buildup of its lipid precursors, providing key insights into its function. Analysis of the Pf ACS11 gene and its mutations point to a role in mediating resistance via decreased protein stability.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-12-2018
Abstract: Malaria parasites are evolutionarily prepared to resist drug attack. Resistance is emerging to even the latest frontline combination therapies, which target the blood stages of the Plasmodium parasite. As an alternative strategy, Antonova-Koch et al. investigated the possibilities of drugs against liver-stage parasites (see the Perspective by Phillips and Goldberg). To do so, they devised a luciferase-reporter drug screen for the rodent parasite Plasmodium berghei. Three rounds of increasingly stringent screening were used. From this regime, several chemotypes that inhibit Plasmodium mitochondrial electron transport were identified. Excitingly, several new scaffolds, with as-yet-unknown modes of action but solely targeting the parasites' liver stages, emerged as promising drug leads for further development. Science , this issue p. eaat9446 see also p. 1112
Publisher: Wiley
Date: 19-02-2019
Publisher: Wiley
Date: 13-09-2017
Abstract: In this work we aimed to develop parasite-selective histone deacetylase inhibitors (HDAC) inhibitors with activity against the disease-causing asexual blood stages of Plasmodium as well as causal prophylactic and/or transmission blocking properties. We report the design, synthesis, and biological testing of a series of 13 terephthalic acid-based HDAC inhibitors. All compounds showed low cytotoxicity against human embryonic kidney (HEK293) cells (IC
Publisher: Cold Spring Harbor Laboratory
Date: 10-11-2017
DOI: 10.1101/216721
Abstract: A critical step towards malaria elimination will be the interruption of Plasmodium transmission from the human host to the mosquito. At the core of the transmission cycle lies Plasmodium sexual reproduction leading to zygote formation and mosquito midgut colonisation by ookinetes. Whilst in vitro ookinete culture from the murine and avian malaria parasites, Plasmodium berghei and P. gallinaceum , has greatly increased our knowledge of transmission biology efforts to mimic the process in the human parasite P. falciparum have, to date, had only limited success. Using fluorescence microscopy and flow cytometry with antibodies specific to the male gametocyte and developing ookinetes, we sought to evaluate P. falciparum ookinete production using previously published in vitro protocols. We then compared in vitro versus in vivo ookinete production in both P. falciparum and P. berghei parasites, exploring potential barriers to complete development. Finally, we sought to test a wide range of literature-led culture conditions towards further optimisation of in vitro P. falciparum ookinete production. Despite extensive testing, our efforts to replicate published methods did not produce appreciable quantities of fully formed P. falciparum ookinetes in vitro . In parallel, however, gametocyte cultures that failed to differentiate fully in vitro successfully developed into ookinetes in vivo with an efficiency approximating that of P. berghei . Flow cytometry analysis showed that this disparity likely lies with the poor fertilization of P. falciparum gametes in vitro . Attempts to improve gametocyte fertility or define conditions more permissive to fertilisation/ookinete survival in vitro were also unsuccessful. Current in vitro conditions for P. falciparum ookinete production are not optimal for gamete fertilisation either due to the lack of parasite-species-specific mosquito factors missing from in vitro culture, or non-permissive cues contaminating culture preparations.
Publisher: American Chemical Society (ACS)
Date: 20-04-2021
Publisher: Elsevier BV
Date: 07-2014
Publisher: Elsevier BV
Date: 02-2020
Publisher: American Chemical Society (ACS)
Date: 06-09-2013
DOI: 10.1021/JM400325J
Publisher: Elsevier BV
Date: 02-2013
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-03-2023
DOI: 10.1126/SCITRANSLMED.ADC9249
Abstract: Development of antimalarial compounds into clinical candidates remains costly and arduous without detailed knowledge of the target. As resistance increases and treatment options at various stages of disease are limited, it is critical to identify multistage drug targets that are readily interrogated in biochemical assays. Whole-genome sequencing of 18 parasite clones evolved using thienopyrimidine compounds with submicromolar, rapid-killing, pan–life cycle antiparasitic activity showed that all had acquired mutations in the P. falciparum cytoplasmic isoleucyl tRNA synthetase (cIRS). Engineering two of the mutations into drug-naïve parasites recapitulated the resistance phenotype, and parasites with conditional knockdowns of cIRS became hypersensitive to two thienopyrimidines. Purified recombinant P. vivax cIRS inhibition, cross-resistance, and biochemical assays indicated a noncompetitive, allosteric binding site that is distinct from that of known cIRS inhibitors mupirocin and reveromycin A. Our data show that Plasmodium cIRS is an important chemically and genetically validated target for next-generation medicines for malaria.
Publisher: Springer Science and Business Media LLC
Date: 19-09-2016
Publisher: American Chemical Society (ACS)
Date: 23-02-2021
Publisher: American Chemical Society (ACS)
Date: 26-10-2016
DOI: 10.1021/ACS.JMEDCHEM.6B01265
Abstract: Introduction of water-solubilizing groups on the 5-phenyl ring of a 2-aminopyrazine series led to the identification of highly potent compounds against the blood life-cycle stage of the human malaria parasite Plasmodium falciparum. Several compounds displayed high in vivo efficacy in two different mouse models for malaria, P. berghei-infected mice and P. falciparum-infected NOD-scid IL-2Rγ
Publisher: Springer Science and Business Media LLC
Date: 27-11-2013
DOI: 10.1038/NATURE12782
Publisher: Public Library of Science (PLoS)
Date: 06-06-2019
Publisher: American Society for Microbiology
Date: 05-07-2017
Abstract: Current efforts to reduce the global burden of malaria are threatened by the rapid spread throughout Asia of Plasmodium falciparum resistance to artemisinin-based combination therapies, which includes increasing rates of clinical failure with dihydroartemisinin plus piperaquine (PPQ) in Cambodia. Using zinc finger nuclease-based gene editing, we report that addition of the C101F mutation to the chloroquine (CQ) resistance-conferring PfCRT Dd2 isoform common to Asia can confer PPQ resistance to cultured parasites. Resistance was demonstrated as significantly higher PPQ concentrations causing 90% inhibition of parasite growth (IC 90 ) or 50% parasite killing (50% lethal dose [LD 50 ]). This mutation also reversed Dd2-mediated CQ resistance, sensitized parasites to amodiaquine, quinine, and artemisinin, and conferred amantadine and blasticidin resistance. Using heme fractionation assays, we demonstrate that PPQ causes a buildup of reactive free heme and inhibits the formation of chemically inert hemozoin crystals. Our data evoke inhibition of heme detoxification in the parasite’s acidic digestive vacuole as the primary mode of both the bis -aminoquinoline PPQ and the related 4-aminoquinoline CQ. Both drugs also inhibit hemoglobin proteolysis at elevated concentrations, suggesting an additional mode of action. Isogenic lines differing in their pfmdr1 copy number showed equivalent PPQ susceptibilities. We propose that mutations in PfCRT could contribute to a multifactorial basis of PPQ resistance in field isolates. IMPORTANCE The global agenda to eliminate malaria depends on the continued success of artemisinin-based combination therapies (ACTs), which target the asexual blood stages of the intracellular parasite Plasmodium . Partial resistance to artemisinin, however, is now established in Southeast Asia, exposing the partner drugs to increased selective pressure. Plasmodium falciparum resistance to the first-line partner piperaquine (PPQ) is now spreading rapidly in Cambodia, resulting in clinical treatment failures. Here, we report that a variant form of the Plasmodium falciparum chloroquine resistance transporter, harboring a C101F mutation edited into the chloroquine (CQ)-resistant Dd2 isoform prevalent in Asia, can confer PPQ resistance in cultured parasites. This was accompanied by a loss of CQ resistance. Biochemical assays showed that PPQ, like CQ, inhibits the detoxification of reactive heme that is formed by parasite-mediated catabolism of host hemoglobin. We propose that novel PfCRT variants emerging in the field could contribute to a multigenic basis of PPQ resistance.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 26-08-2005
Abstract: The malaria parasite, Plasmodium falciparum , exploits multiple ligand-receptor interactions, called invasion pathways, to invade the host erythrocyte. Strains of P. falciparum vary in their dependency on sialated red cell receptors for invasion. We show that switching from sialic acid–dependent to –independent invasion is reversible and depends on parasite ligand use. Expression of P. falciparum reticulocyte–binding like homolog 4 (PfRh4) correlates with sialic acid–independent invasion, and PfRh4 is essential for switching invasion pathways. Differential activation of PfRh4 represents a previously unknown mechanism to switch invasion pathways and provides P. falciparum with exquisite adaptability in the face of erythrocyte receptor polymorphisms and host immune responses.
Publisher: American Chemical Society (ACS)
Date: 17-07-2017
DOI: 10.1021/ACS.JMEDCHEM.7B00140
Abstract: Structural optimization of 3-hydroxy-N'-arylidenepropanehydrazonamides provided new analogs with nanomolar to subnanomolar antiplasmodial activity against asexual blood stages of Plasmodium falciparum, excellent parasite selectivity, and nanomolar activity against the earliest forms of gametocyte development. Particularly, derivatives with a 1,3-dihalo-6-trifluoromethylphenanthrene moiety showed outstanding in vivo properties and demonstrated in part curative activity in the Plasmodium berghei mouse model when administered perorally.
Publisher: Proceedings of the National Academy of Sciences
Date: 20-03-2019
Abstract: 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.
Publisher: American Society for Microbiology
Date: 22-12-2020
Abstract: Malaria, caused by Plasmodium parasites, continues to be a devastating global health issue, causing 405,000 deaths and 228 million cases in 2018. Understanding key metabolic processes in malaria parasites is critical to the development of new drugs to combat this major infectious disease. The Plasmodium glycolytic pathway is essential to the malaria parasite, providing energy for growth and replication and supplying important biomolecules for other essential Plasmodium anabolic pathways. Despite this overreliance on glycolysis, no current drugs target glycolysis, and there is a paucity of information on critical glycolysis targets. Our work addresses this unmet need, providing new mechanistic insights into this key pathway.
Publisher: Public Library of Science (PLoS)
Date: 23-06-2006
Publisher: Springer Science and Business Media LLC
Date: 04-2012
DOI: 10.1038/484S22A
Publisher: American Chemical Society (ACS)
Date: 14-09-2016
Publisher: Elsevier BV
Date: 07-2020
Publisher: American Chemical Society (ACS)
Date: 10-09-2016
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-09-2010
Abstract: Spiroindolones were discovered as promising antimalarial drug candidates through a high-throughput screening approach that should be applicable to a range of neglected infectious diseases. Rottmann et al. (p. 1175 see the Perspective by Wells ) present the preclinical profile for an optimized spiroindolone drug candidate, NITD609. They obtained evidence for a decrease in drug sensitivity in strains of the malaria parasite Plasmodium falciparum bearing amino acid mutations in the P-type ATPase, indicating possible mechanisms of action and/or resistance.
Publisher: Cold Spring Harbor Laboratory
Date: 23-11-2022
DOI: 10.1101/2022.11.22.517223
Abstract: Changes in host cell morphology and transcription after apicomplexan parasite infection have long been noted, but there have been few studies of the functional consequences of host cell remodeling. Here we show, using time-dependent immunofluorescence microscopy of multiple human cell lines (HepG2, HC-04, Huh7.5.1 and primary human hepatocytes), infected with multiple Plasmodium species ( Plasmodium berghei, P. falciparum and P. vivax (hypnozoites and schizonts)), and antibodies to multiple human proteins (HsNR4A3, HsMUC13, HsGOLGA8A, HsCGA, HsBiP, HsCXCL2), that human protein trafficking is extensively modified in Plasmodium infected cells. Using conventional as well as ultrastructure expansion microscopy we show that newly-synthesized human proteins are trafficked to the parasitophorous vacuole instead of the infected-cell plasma membrane, nucleus or extracellular space. Universal redirection of human signaling proteins cells the parasitophorous vacuole may provide a mechanistic explanation for how apicomplexan parasites can block host cells response to infection.
Publisher: Public Library of Science (PLoS)
Date: 2006
Publisher: Springer Science and Business Media LLC
Date: 2009
Publisher: Elsevier BV
Date: 04-2005
DOI: 10.1016/J.IJPARA.2005.02.010
Abstract: This study is motivated by two data sets which employ a custom Plasmodium falciparum version of the Affymetrix GeneChip, containing only perfect match (PM) oligonucleotides. A PM-only chip cannot be analysed using the standard Affymetrix-supplied software. We compared the performance of three match-only algorithms on these data: the Match Only Integral Distribution (MOID) algorithm, Robust Multichip Analysis (RMA), and the Model Based Expression Index (MBEI). We validated the differential expression of several genes using quantitative reverse transcriptase-PCR. We also performed a comparison using two publicly available 'benchmarking' data sets: the Latin Square spike-in data set generated by Affymetrix, and the Gene Logic dilution series. Since we know what the true fold changes are in these special data sets, they are helpful for assessment of expression algorithms.
Publisher: Springer Science and Business Media LLC
Date: 20-11-2020
DOI: 10.1038/S42003-020-01424-Z
Abstract: Mitosis has been validated by numerous anti-cancer drugs as being a druggable process, and selective inhibition of parasite proliferation provides an obvious opportunity for therapeutic intervention against malaria. Mitosis is controlled through the interplay between several protein kinases and phosphatases. We show here that inhibitors of human mitotic kinases belonging to the Aurora family inhibit P. falciparum proliferation in vitro with various potencies, and that a genetic selection for mutant parasites resistant to one of the drugs, Hesperadin, identifies a resistance mechanism mediated by a member of a different kinase family, PfNek1 (PF3D7_1228300). Intriguingly, loss of PfNek1 catalytic activity provides protection against drug action. This points to an undescribed functional interaction between Ark and Nek kinases and shows that existing inhibitors can be used to validate additional essential and druggable kinase functions in the parasite.
Publisher: Wiley
Date: 14-01-2019
Abstract: A series of novel 8-aminoquinolines (8-AQs) with an aminoxyalkyl side chain were synthesized and evaluated for in vitro antiplasmodial properties against asexual blood stages, liver stages, and sexual stages of Plasmodium falciparum. 8-AQs bearing 2-alkoxy and 5-phenoxy substituents on the quinoline ring system were found to be the most promising compounds under study, exhibiting potent blood schizontocidal and moderate tissue schizontocidal in vitro activity.
Publisher: Oxford University Press (OUP)
Date: 08-2013
Publisher: American Association for the Advancement of Science (AAAS)
Date: 09-12-2011
Abstract: Imidazolopiperazine compounds inhibit liver-stage malaria parasites with one oral dose in mice.
Publisher: Springer Science and Business Media LLC
Date: 17-06-2015
DOI: 10.1038/NATURE14451
Publisher: Springer Science and Business Media LLC
Date: 14-04-2020
DOI: 10.1038/S41467-020-15440-4
Abstract: A promising new compound class for treating human malaria is the imidazolopiperazines (IZP) class. IZP compounds KAF156 (Ganaplacide) and GNF179 are effective against Plasmodium symptomatic asexual blood-stage infections, and are able to prevent transmission and block infection in animal models. But despite the identification of resistance mechanisms in P. falciparum , the mode of action of IZPs remains unknown. To investigate, we here combine in vitro evolution and genome analysis in Saccharomyces cerevisiae with molecular, metabolomic, and chemogenomic methods in P. falciparum . Our findings reveal that IZP-resistant S. cerevisiae clones carry mutations in genes involved in Endoplasmic Reticulum (ER)-based lipid homeostasis and autophagy. In Plasmodium , IZPs inhibit protein trafficking, block the establishment of new permeation pathways, and cause ER expansion. Our data highlight a mechanism for blocking parasite development that is distinct from those of standard compounds used to treat malaria, and demonstrate the potential of IZPs for studying ER-dependent protein processing.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-06-2022
Abstract: Aminoacyl transfer RNA (tRNA) synthetases (aaRSs) are attractive drug targets, and we present class I and II aaRSs as previously unrecognized targets for adenosine 5′-monophosphate–mimicking nucleoside sulfamates. The target enzyme catalyzes the formation of an inhibitory amino acid–sulfamate conjugate through a reaction-hijacking mechanism. We identified adenosine 5′-sulfamate as a broad-specificity compound that hijacks a range of aaRSs and ML901 as a specific reagent a specific reagent that hijacks a single aaRS in the malaria parasite Plasmodium falciparum , namely tyrosine RS ( Pf YRS). ML901 exerts whole-life-cycle–killing activity with low nanomolar potency and single-dose efficacy in a mouse model of malaria. X-ray crystallographic studies of plasmodium and human YRSs reveal differential flexibility of a loop over the catalytic site that underpins differential susceptibility to reaction hijacking by ML901.
Location: United States of America
No related grants have been discovered for Elizabeth Winzeler.