Publications by authors named "Francisco-Javier Gamo"

67 Publications

MalDA, Accelerating Malaria Drug Discovery.

Trends Parasitol 2021 Jun 26;37(6):493-507. Epub 2021 Feb 26.

Department of Pediatrics, School of Medicine, University of California, San Diego (UCSD), La Jolla, CA 92093, USA. Electronic address:

The Malaria Drug Accelerator (MalDA) is a consortium of 15 leading scientific laboratories. The aim of MalDA is to improve and accelerate the early antimalarial drug discovery process by identifying new, essential, druggable targets. In addition, it seeks to produce early lead inhibitors that may be advanced into drug candidates suitable for preclinical development and subsequent clinical testing in humans. By sharing resources, including expertise, knowledge, materials, and reagents, the consortium strives to eliminate the structural barriers often encountered in the drug discovery process. Here we discuss the mission of the consortium and its scientific achievements, including the identification of new chemically and biologically validated targets, as well as future scientific directions.
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http://dx.doi.org/10.1016/j.pt.2021.01.009DOI Listing
June 2021

Novel Antimalarial Tetrazoles and Amides Active against the Hemoglobin Degradation Pathway in .

J Med Chem 2021 Mar 23;64(5):2739-2761. Epub 2021 Feb 23.

Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States.

Malaria control programs continue to be threatened by drug resistance. To identify new antimalarials, we conducted a phenotypic screen and identified a novel tetrazole-based series that shows fast-kill kinetics and a relatively low propensity to develop high-level resistance. Preliminary structure-activity relationships were established including identification of a subseries of related amides with antiplasmodial activity. Assaying parasites with resistance to antimalarials led us to test whether the series had a similar mechanism of action to chloroquine (CQ). Treatment of synchronized parasites with active analogues revealed a pattern of intracellular inhibition of hemozoin (Hz) formation reminiscent of CQ's action. Drug selections yielded only modest resistance that was associated with amplification of the multidrug resistance gene 1 (). Thus, we have identified a novel chemical series that targets the historically druggable heme polymerization pathway and that can form the basis of future optimization efforts to develop a new malaria treatment.
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http://dx.doi.org/10.1021/acs.jmedchem.0c02022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7997635PMC
March 2021

The antimalarial efficacy and mechanism of resistance of the novel chemotype DDD01034957.

Sci Rep 2021 Jan 21;11(1):1888. Epub 2021 Jan 21.

Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK.

New antimalarial therapeutics are needed to ensure that malaria cases continue to be driven down, as both emerging parasite resistance to frontline chemotherapies and mosquito resistance to current insecticides threaten control programmes. Plasmodium, the apicomplexan parasite responsible for malaria, causes disease pathology through repeated cycles of invasion and replication within host erythrocytes (the asexual cycle). Antimalarial drugs primarily target this cycle, seeking to reduce parasite burden within the host as fast as possible and to supress recrudescence for as long as possible. Intense phenotypic drug screening efforts have identified a number of promising new antimalarial molecules. Particularly important is the identification of compounds with new modes of action within the parasite to combat existing drug resistance and suitable for formulation of efficacious combination therapies. Here we detail the antimalarial properties of DDD01034957-a novel antimalarial molecule which is fast-acting and potent against drug resistant strains in vitro, shows activity in vivo, and possesses a resistance mechanism linked to the membrane transporter PfABCI3. These data support further medicinal chemistry lead-optimization of DDD01034957 as a novel antimalarial chemical class and provide new insights to further reduce in vivo metabolic clearance.
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http://dx.doi.org/10.1038/s41598-021-81343-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820608PMC
January 2021

A novel class of fast-acting antimalarial agents: Substituted 15-membered azalides.

Br J Pharmacol 2021 Jan 16;178(2):363-377. Epub 2020 Dec 16.

GlaxoSmithKline Research Centre Zagreb Ltd., Zagreb, Croatia.

Background And Purpose: Efficacy of current antimalarial treatments is declining as a result of increasing antimalarial drug resistance, so new and potent antimalarial drugs are urgently needed. Azithromycin, an azalide antibiotic, was found useful in malaria therapy, but its efficacy in humans is low.

Experimental Approach: Four compounds belonging to structurally different azalide classes were tested and their activities compared to azithromycin and chloroquine. in vitro evaluation included testing against sensitive and resistant Plasmodium falciparum, cytotoxicity against HepG2 cells, accumulation and retention in human erythrocytes, antibacterial activity, and mode of action studies (delayed death phenotype and haem polymerization). in vivo assessment enabled determination of pharmacokinetic profiles in mice, rats, dogs, and monkeys and in vivo efficacy in a humanized mouse model.

Key Results: Novel fast-acting azalides were highly active in vitro against P. falciparum strains exhibiting various resistance patterns, including chloroquine-resistant strains. Excellent antimalarial activity was confirmed in a P. falciparum murine model by strong inhibition of haemozoin-containing trophozoites and quick clearance of parasites from the blood. Pharmacokinetic analysis revealed that compounds are metabolically stable and have moderate oral bioavailability, long half-lives, low clearance, and substantial exposures, with blood cells as the preferred compartment, especially infected erythrocytes. Fast anti-plasmodial action is achieved by the high accumulation into infected erythrocytes and interference with parasite haem polymerization, a mode of action different from slow-acting azithromycin.

Conclusion And Implications: The hybrid derivatives described here represent excellent antimalarial drug candidates with the potential for clinical use in malaria therapy.
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http://dx.doi.org/10.1111/bph.15292DOI Listing
January 2021

Synthesis and Structure-Activity Relationship of Dual-Stage Antimalarial Pyrazolo[3,4-]pyridines.

J Med Chem 2020 10 1;63(20):11902-11919. Epub 2020 Oct 1.

Medicines for Malaria Venture (MMV), P.O. Box 1826, 20, Route de Pré-Bois, Geneva 1215, Switzerland.

Malaria remains one of the most deadly infectious diseases, causing hundreds of thousands of deaths each year, primarily in young children and pregnant mothers. Here, we report the discovery and derivatization of a series of pyrazolo[3,4-]pyridines targeting , the deadliest species of the malaria parasite. Hit compounds in this series display sub-micromolar activity against the intraerythrocytic stage of the parasite as well as little to no toxicity against the human fibroblast BJ and liver HepG2 cell lines. In addition, our hit compounds show good activity against the liver stage of the parasite but little activity against the gametocyte stage. Parasitological profiles, including rate of killing, docking, and molecular dynamics studies, suggest that our compounds may target the Q binding site of cytochrome .
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http://dx.doi.org/10.1021/acs.jmedchem.0c01152DOI Listing
October 2020

Design and tests of prospective property predictions for novel antimalarial 2-aminopropylaminoquinolones.

J Comput Aided Mol Des 2020 11 24;34(11):1117-1132. Epub 2020 Aug 24.

Simulations Plus, Inc., 42505 10th Street West, Lancaster, CA, 93534-7059, USA.

There is a pressing need to improve the efficiency of drug development, and nowhere is that need more clear than in the case of neglected diseases like malaria. The peculiarities of pyrimidine metabolism in Plasmodium species make inhibition of dihydroorotate dehydrogenase (DHODH) an attractive target for antimalarial drug design. By applying a pair of complementary quantitative structure-activity relationships derived for inhibition of a truncated, soluble form of the enzyme from Plasmodium falciparum (s-PfDHODH) to data from a large-scale phenotypic screen against cultured parasites, we were able to identify a class of antimalarial leads that inhibit the enzyme and abolish parasite growth in blood culture. Novel analogs extending that class were designed and synthesized with a goal of improving potency as well as the general pharmacokinetic and toxicological profiles. Their synthesis also represented an opportunity to prospectively validate our in silico property predictions. The seven analogs synthesized exhibited physicochemical properties in good agreement with prediction, and five of them were more active against P. falciparum growing in blood culture than any of the compounds in the published lead series. The particular analogs prepared did not inhibit s-PfDHODH in vitro, but advanced biological assays indicated that other examples from the class did inhibit intact PfDHODH bound to the mitochondrial membrane. The new analogs, however, killed the parasites by acting through some other, unidentified mechanism 24-48 h before PfDHODH inhibition would be expected to do so.
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http://dx.doi.org/10.1007/s10822-020-00333-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7533260PMC
November 2020

variant distribution in sub-Saharan Africa and potential risks of using chloroquine/hydroxychloroquine based treatments for COVID-19.

medRxiv 2020 Jun 2. Epub 2020 Jun 2.

Chloroquine/hydroxychloroquine have been proposed as potential treatments for COVID-19. These drugs have warning labels for use in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Analysis of whole-genome sequence data of 458 individuals from sub-Saharan Africa showed significant variation across the continent. We identified nine variants, of which four are potentially deleterious to G6PD function, and one (rs1050828) that is known to cause G6PD deficiency. We supplemented data for the rs1050828 variant with genotype array data from over 11,000 Africans. Although this variant is common in Africans overall, large allele frequency differences exist between sub-populations. African sub-populations in the same country can show significant differences in allele frequency (e.g. 16.0% in Tsonga vs 0.8% in Xhosa, both in South Africa, ρ=2.4×10 ). The high prevalence of variants in the gene found in this analysis suggests that it may be a significant interaction factor in clinical trials of chloroquine and hydrochloroquine for treatment of COVID-19 in Africans.
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http://dx.doi.org/10.1101/2020.05.27.20114066DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7302299PMC
June 2020

In vitro selection predicts malaria parasite resistance to dihydroorotate dehydrogenase inhibitors in a mouse infection model.

Sci Transl Med 2019 12;11(521)

Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA.

Resistance has developed in malaria parasites to every antimalarial drug in clinical use, prompting the need to characterize the pathways mediating resistance. Here, we report a framework for assessing development of resistance of to new antimalarial therapeutics. We investigated development of resistance by to the dihydroorotate dehydrogenase (DHODH) inhibitors DSM265 and DSM267 in tissue culture and in a mouse model of infection. We found that resistance to these drugs arose rapidly both in vitro and in vivo. We identified 13 point mutations mediating resistance in the parasite DHODH in vitro that overlapped with the DHODH mutations that arose in the mouse infection model. Mutations in DHODH conferred increased resistance (ranging from 2- to ~400-fold) to DHODH inhibitors in in vitro and in vivo. We further demonstrated that the drug-resistant parasites carrying the C276Y mutation had mitochondrial energetics comparable to the wild-type parasite and also retained their fitness in competitive growth experiments. Our data suggest that in vitro selection of drug-resistant can predict development of resistance in a mouse model of malaria infection.
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http://dx.doi.org/10.1126/scitranslmed.aav1636DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7444640PMC
December 2019

Identification of Small Molecules Disrupting the Ubiquitin Proteasome System in Malaria.

ACS Infect Dis 2019 12 7;5(12):2105-2117. Epub 2019 Nov 7.

Tres Cantos Medicines Development Campus, Diseases of the Developing World . GlaxoSmithKline , Severo Ochoa 2 , Tres Cantos , 28760 Madrid , Spain.

The ubiquitin proteasome system (UPS) is one of the main proteolytic pathways in eukaryotic cells, playing an essential role in key cellular processes such as cell cycling and signal transduction. Changes in some of the components of this pathway have been implicated in various conditions, including cancer and infectious diseases such as malaria. The success of therapies based on proteasome inhibitors has been shown in human clinical trials. In addition to its proven tractability, the essentiality of the UPS underlines its potential as a source of targets to identify new antimalarial treatments. Two assays, previously developed to quantify the parasite protein ubiquitylation levels in a high throughput format, have been used to identify compounds that inhibit parasite growth by targeting UPS. Among the positive hits, specific inhibitors of the proteasome have been identified and characterized. Hits identified using this approach may be used as starting points for development of new antimalarial drugs. They may also be used as tools to further understand proteasome function and to identify new targets in UPS.
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http://dx.doi.org/10.1021/acsinfecdis.9b00216DOI Listing
December 2019

Fueling Open Innovation for Malaria Transmission-Blocking Drugs: Hundreds of Molecules Targeting Early Parasite Mosquito Stages.

Front Microbiol 2019 13;10:2134. Epub 2019 Sep 13.

Department of Life Sciences, Imperial College London, London, United Kingdom.

Background: Despite recent successes at controlling malaria, progress has stalled with an estimated 219 million cases and 435,000 deaths in 2017 alone. Combined with emerging resistance to front line antimalarial therapies in Southeast Asia, there is an urgent need for new treatment options and novel approaches to halt the spread of malaria. , the parasite responsible for malaria propagates through mosquito transmission. This imposes an acute bottleneck on the parasite population and transmission-blocking interventions exploiting this vulnerability are recognized as vital for malaria elimination.

Methods: 13,533 small molecules with known activity against asexual parasites were screened for additional transmission-blocking activity in an ookinete development assay. Active molecules were then counterscreened in dose response against HepG2 cells to determine their activity/cytotoxicity window and selected non-toxic representative molecules were fully profiled in a range of transmission and mosquito infection assays. Furthermore, the entire dataset was compared to other published screens of the same molecules against gametocytes and female gametogenesis.

Results: 437 molecules inhibited ookinete formation with an IC < 10 μM. of which 273 showed >10-fold parasite selectivity compared to activity against HepG2 cells. Active molecules grouped into 49 chemical clusters of three or more molecules, with 25 doublets and 94 singletons. Six molecules representing six major chemical scaffolds confirmed their transmission-blocking activity against male and female gametocytes and inhibited oocyst formation in the standard membrane feeding assay at 1 μM. When screening data in the development ookinete assay was compared to published screens of the same library in assays against gametocytes and female gametogenesis, it was established that each assay identified distinct, but partially overlapping subsets of transmission-blocking molecules. However, selected molecules unique to each assay show transmission-blocking activity in mosquito transmission assays.

Conclusion: The ookinete development assay is an excellent high throughput assay for efficiently identifying antimalarial molecules targeting early mosquito stage parasite development. Currently no high throughput transmission-blocking assay is capable of identifying all transmission-blocking molecules.
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http://dx.doi.org/10.3389/fmicb.2019.02134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6753678PMC
September 2019

Validation of the protein kinase CLK3 as a multistage cross-species malarial drug target.

Science 2019 08;365(6456)

Diseases of the Developing World, GlaxoSmithKline, 28760 Tres Cantos, Madrid, Spain.

The requirement for next-generation antimalarials to be both curative and transmission-blocking necessitates the identification of previously undiscovered druggable molecular pathways. We identified a selective inhibitor of the protein kinase CLK3, which we used in combination with chemogenetics to validate CLK3 as a drug target acting at multiple parasite life stages. Consistent with a role for CLK3 in RNA splicing, inhibition resulted in the down-regulation of more than 400 essential parasite genes. Inhibition of CLK3 mediated rapid killing of asexual liver- and blood-stage and blockade of gametocyte development, thereby preventing transmission, and also showed parasiticidal activity against and Hence, our data establish CLK3 as a target for drugs, with the potential to offer a cure-to be prophylactic and transmission blocking in malaria.
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http://dx.doi.org/10.1126/science.aau1682DOI Listing
August 2019

Substituted Aminoacetamides as Novel Leads for Malaria Treatment.

ChemMedChem 2019 07 3;14(14):1329-1335. Epub 2019 Jul 3.

Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.

Herein we describe the optimization of a phenotypic hit against Plasmodium falciparum based on an aminoacetamide scaffold. This led to N-(3-chloro-4-fluorophenyl)-2-methyl-2-{[4-methyl-3-(morpholinosulfonyl)phenyl]amino}propanamide (compound 28) with low-nanomolar activity against the intraerythrocytic stages of the malaria parasite, and which was found to be inactive in a mammalian cell counter-screen up to 25 μm. Inhibition of gametes in the dual gamete activation assay suggests that this family of compounds may also have transmission blocking capabilities. Whilst we were unable to optimize the aqueous solubility and microsomal stability to a point at which the aminoacetamides would be suitable for in vivo pharmacokinetic and efficacy studies, compound 28 displayed excellent antimalarial potency and selectivity; it could therefore serve as a suitable chemical tool for drug target identification.
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http://dx.doi.org/10.1002/cmdc.201900329DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6899483PMC
July 2019

Lysyl-tRNA synthetase as a drug target in malaria and cryptosporidiosis.

Proc Natl Acad Sci U S A 2019 04 20;116(14):7015-7020. Epub 2019 Mar 20.

Department of Life Sciences, Imperial College, South Kensington, SW7 2AZ London, United Kingdom.

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 and in cell-culture studies. Target deconvolution in has shown that cladosporin inhibits lysyl-tRNA synthetase (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 KRS1 and KRS (KRS). In vivo proof of concept was established in an SCID mouse model of malaria, after oral administration (ED = 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 KRS1 and KRS. This series of compounds inhibit KRS and and 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 KRS1 and KRS vs. (human) KRS. Our work validates apicomplexan KRSs as promising targets for the development of drugs for malaria and cryptosporidiosis.
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http://dx.doi.org/10.1073/pnas.1814685116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6452685PMC
April 2019

Overexpression of plasmepsin II and plasmepsin III does not directly cause reduction in Plasmodium falciparum sensitivity to artesunate, chloroquine and piperaquine.

Int J Parasitol Drugs Drug Resist 2019 04 1;9:16-22. Epub 2018 Dec 1.

Parasites and Microbes Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, CB10 1SA, United Kingdom. Electronic address:

Artemisinin derivatives and their partner drugs in artemisinin combination therapies (ACTs) have played a pivotal role in global malaria mortality reduction during the last two decades. The loss of artemisinin efficacy due to evolving drug-resistant parasites could become a serious global health threat. Dihydroartemisinin-piperaquine is a well tolerated and generally highly effective ACT. The implementation of a partner drug in ACTs is critical in the control of emerging artemisinin resistance. Even though artemisinin is highly effective in parasite clearance, it is labile in the human body. A partner drug is necessary for killing the remaining parasites when the pulses of artemisinin have ceased. A population of Plasmodium falciparum parasites in Cambodia and adjacent countries has become resistant to piperaquine. Increased copy number of the genes encoding the haemoglobinases Plasmepsin II and Plasmepsin III has been linked with piperaquine resistance by genome-wide association studies and in clinical trials, leading to the use of increased plasmepsin II/plasmepsin III copy number as a molecular marker for piperaquine resistance. Here we demonstrate that overexpression of plasmepsin II and plasmepsin III in the 3D7 genetic background failed to change the susceptibility of P. falciparum to artemisinin, chloroquine and piperaquine by both a standard dose-response analysis and a piperaquine survival assay. Whilst plasmepsin copy number polymorphism is currently implemented as a molecular surveillance resistance marker, further studies to discover the molecular basis of piperaquine resistance and potential epistatic interactions are needed.
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http://dx.doi.org/10.1016/j.ijpddr.2018.11.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6304341PMC
April 2019

Evaluation of 4-Amino 2-Anilinoquinazolines against and Other Apicomplexan Parasites and in a Humanized NOD- IL2Rγ Mouse Model of Malaria.

Antimicrob Agents Chemother 2019 03 26;63(3). Epub 2019 Feb 26.

The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia

A series of 4-amino 2-anilinoquinazolines optimized for activity against the most lethal malaria parasite of humans, , was evaluated for activity against other human parasites and related apicomplexans that infect humans and animals. Four of the most promising compounds from the 4-amino 2-anilinoquinazoline series were equally as effective against the asexual blood stages of the zoonotic , suggesting that they could also be effective against the closely related , another important human pathogen. The 2-anilinoquinazoline compounds were also potent against an array of parasites resistant to clinically available antimalarial compounds, although slightly less so than against the drug-sensitive 3D7 parasite line. The apicomplexan parasites , , and were less sensitive to the 2-anilinoquinazoline series with a 50% effective concentration generally in the low micromolar range, suggesting that the yet to be discovered target of these compounds is absent or highly divergent in non- parasites. The 2-anilinoquinazoline compounds act as rapidly as chloroquine and when tested in rodents displayed a half-life that contributed to the compound's capacity to clear blood stages in a humanized mouse model. At a dose of 50 mg/kg of body weight, adverse effects to the humanized mice were noted, and evaluation against a panel of experimental high-risk off targets indicated some potential off-target activity. Further optimization of the 2-anilinoquinazoline antimalarial class will concentrate on improving efficacy and addressing adverse risk.
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http://dx.doi.org/10.1128/AAC.01804-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6395901PMC
March 2019

Open-source discovery of chemical leads for next-generation chemoprotective antimalarials.

Science 2018 12;362(6419)

Center for Tropical and Emerging Global Diseases, University of Georgia, 500 D. W. Brooks Drive, Athens, GA 30602, USA.

To discover leads for next-generation chemoprotective antimalarial drugs, we tested more than 500,000 compounds for their ability to inhibit liver-stage development of luciferase-expressing spp. parasites (681 compounds showed a half-maximal inhibitory concentration of less than 1 micromolar). Cluster analysis identified potent and previously unreported scaffold families as well as other series previously associated with chemoprophylaxis. Further testing through multiple phenotypic assays that predict stage-specific and multispecies antimalarial activity distinguished compound classes that are likely to provide symptomatic relief by reducing asexual blood-stage parasitemia from those which are likely to only prevent malaria. Target identification by using functional assays, in vitro evolution, or metabolic profiling revealed 58 mitochondrial inhibitors but also many chemotypes possibly with previously unidentified mechanisms of action.
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http://dx.doi.org/10.1126/science.aat9446DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6516198PMC
December 2018

Isoxazolopyrimidine-Based Inhibitors of Dihydroorotate Dehydrogenase with Antimalarial Activity.

ACS Omega 2018 Aug 15;3(8):9227-9240. Epub 2018 Aug 15.

Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd, Dallas, Texas 75390-9038, United States.

Malaria kills nearly 0.5 million people yearly and impacts the lives of those living in over 90 countries where it is endemic. The current treatment programs are threatened by increasing drug resistance. Dihydroorotate dehydrogenase (DHODH) is now clinically validated as a target for antimalarial drug discovery as a triazolopyrimidine class inhibitor () is currently undergoing clinical development. We discovered a related isoxazolopyrimidine series in a phenotypic screen, later determining that it targeted DHODH. To determine if the isoxazolopyrimidines could yield a drug candidate, we initiated hit-to-lead medicinal chemistry. Several potent analogues were identified, including a compound that showed in vivo antimalarial activity. The isoxazolopyrimidines were more rapidly metabolized than their triazolopyrimidine counterparts, and the pharmacokinetic data were not consistent with the goal of a single-dose treatment for malaria.
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http://dx.doi.org/10.1021/acsomega.8b01573DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120730PMC
August 2018

UCT943, a Next-Generation Plasmodium falciparum PI4K Inhibitor Preclinical Candidate for the Treatment of Malaria.

Antimicrob Agents Chemother 2018 09 27;62(9). Epub 2018 Aug 27.

Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Pretoria, South Africa.

The 2-aminopyridine MMV048 was the first drug candidate inhibiting phosphatidylinositol 4-kinase (PI4K), a novel drug target for malaria, to enter clinical development. In an effort to identify the next generation of PI4K inhibitors, the series was optimized to improve properties such as solubility and antiplasmodial potency across the parasite life cycle, leading to the 2-aminopyrazine UCT943. The compound displayed higher asexual blood stage, transmission-blocking, and liver stage activities than MMV048 and was more potent against resistant and clinical isolates. Excellent antiplasmodial activity translated into high efficacy in and humanized NOD-γ mouse models. The high passive permeability and high aqueous solubility of UCT943, combined with low to moderate intrinsic clearance, resulted in sustained exposure and high bioavailability in preclinical species. In addition, the predicted human dose for a curative single administration using monkey and dog pharmacokinetics was low, ranging from 50 to 80 mg. As a next-generation PI4K inhibitor, UCT943, based on the combined preclinical data, has the potential to form part of a single-exposure radical cure and prophylaxis (SERCaP) to treat, prevent, and block the transmission of malaria.
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http://dx.doi.org/10.1128/AAC.00012-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6125526PMC
September 2018

High-throughput microsphiltration to assess red blood cell deformability and screen for malaria transmission-blocking drugs.

Nat Protoc 2018 06 24;13(6):1362-1376. Epub 2018 May 24.

Diseases of the Developing World (DDW), GlaxoSmithKline, Tres Cantos, Spain.

The mechanical retention of rigid erythrocytes in the spleen is central in major hematological diseases such as hereditary spherocytosis, sickle-cell disease and malaria. Here, we describe the use of microsphiltration (microsphere filtration) to assess erythrocyte deformability in hundreds to thousands of samples in parallel, by filtering them through microsphere layers in 384-well plates adapted for the discovery of compounds that stiffen Plasmodium falciparum gametocytes, with the aim of interrupting malaria transmission. Compound-exposed gametocytes are loaded into microsphiltration plates, filtered and then transferred to imaging plates for analysis. High-content imaging detects viable gametocytes upstream and downstream from filters and quantifies spleen-like retention. This screening assay takes 3-4 d. Unlike currently available methods used to assess red blood cell (RBC) deformability, microsphiltration enables high-throughput pharmacological screening (tens of thousands of compounds tested in a matter of months) and involves a cell mechanical challenge that induces a physiologically relevant dumbbell-shape deformation. It therefore directly assesses the ability of RBCs to cross inter-endothelial splenic slits in vivo. This protocol has potential applications in quality control for transfusion and in determination of phenotypic markers of erythrocytes in hematological diseases.
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http://dx.doi.org/10.1038/nprot.2018.035DOI Listing
June 2018

Identification of Collateral Sensitivity to Dihydroorotate Dehydrogenase Inhibitors in Plasmodium falciparum.

ACS Infect Dis 2018 04 22;4(4):508-515. Epub 2018 Jan 22.

Department of Immunology and Infectious Diseases , Harvard T. H. Chan School of Public Health , 665 Huntington Avenue , Boston , Massachusetts 02115 , United States.

Drug resistance has been reported for every antimalarial in use highlighting the need for new strategies to protect the efficacy of therapeutics in development. We have previously shown that resistance can be suppressed with a population biology trap: by identifying situations where resistance to one compound confers hypersensitivity to another (collateral sensitivity), we can design combination therapies that not only kill the parasite but also guide its evolution away from resistance. We applied this concept to the Plasmodium falciparum dihydroorotate dehydrogenase ( PfDHODH) enzyme, a well validated antimalarial target with inhibitors in the development pipeline. Here, we report a high-throughput screen to identify compounds specifically active against PfDHODH resistant mutants. We additionally perform extensive cross-resistance profiling allowing us to identify compound pairs demonstrating the potential for mutually incompatible resistance. These combinations represent promising starting points for exploiting collateral sensitivity to extend the useful lifespan of new antimalarial therapeutics.
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http://dx.doi.org/10.1021/acsinfecdis.7b00217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5899019PMC
April 2018

Mapping the malaria parasite druggable genome by using in vitro evolution and chemogenomics.

Science 2018 01;359(6372):191-199

Malaria Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridgeshire CB10 1SA, UK.

Chemogenetic characterization through in vitro evolution combined with whole-genome analysis can identify antimalarial drug targets and drug-resistance genes. We performed a genome analysis of 262 parasites resistant to 37 diverse compounds. We found 159 gene amplifications and 148 nonsynonymous changes in 83 genes associated with drug-resistance acquisition, where gene amplifications contributed to one-third of resistance acquisition events. Beyond confirming previously identified multidrug-resistance mechanisms, we discovered hitherto unrecognized drug target-inhibitor pairs, including thymidylate synthase and a benzoquinazolinone, farnesyltransferase and a pyrimidinedione, and a dipeptidylpeptidase and an arylurea. This exploration of the resistome and druggable genome will likely guide drug discovery and structural biology efforts, while also advancing our understanding of resistance mechanisms available to the malaria parasite.
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http://dx.doi.org/10.1126/science.aan4472DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5925756PMC
January 2018

Efforts Aimed To Reduce Attrition in Antimalarial Drug Discovery: A Systematic Evaluation of the Current Antimalarial Targets Portfolio.

ACS Infect Dis 2018 04 24;4(4):568-576. Epub 2018 Jan 24.

Tres Cantos Medicines Development Campus, DDW , GlaxoSmithKline , Severo Ochoa, 2 , 28760 Tres Cantos , Madrid , Spain.

Malaria remains a major global health problem. In 2015 alone, more than 200 million cases of malaria were reported, and more than 400,000 deaths occurred. Since 2010, emerging resistance to current front-line ACTs (artemisinin combination therapies) has been detected in endemic countries. Therefore, there is an urgency for new therapies based on novel modes of action, able to relieve symptoms as fast as the artemisinins and/or block malaria transmission. During the past few years, the antimalarial community has focused their efforts on phenotypic screening as a pragmatic approach to identify new hits. Optimization efforts on several chemical series have been successful, and clinical candidates have been identified. In addition, recent advances in genetics and proteomics have led to the target deconvolution of phenotypic clinical candidates. New mechanisms of action will also be critical to overcome resistance and reduce attrition. Therefore, a complementary strategy focused on identifying well-validated targets to start hit identification programs is essential to reinforce the clinical pipeline. Leveraging published data, we have assessed the status quo of the current antimalarial target portfolio with a focus on the blood stage clinical disease. From an extensive list of reported Plasmodium targets, we have defined triage criteria. These criteria consider genetic, pharmacological, and chemical validation, as well as tractability/doability, and safety implications. These criteria have provided a quantitative score that has led us to prioritize those targets with the highest probability to deliver successful and differentiated new drugs.
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http://dx.doi.org/10.1021/acsinfecdis.7b00211DOI Listing
April 2018

A human microdose study of the antimalarial drug GSK3191607 in healthy volunteers.

Br J Clin Pharmacol 2018 03 29;84(3):482-489. Epub 2017 Dec 29.

Malaria DPU, Tres Cantos Medicines Development Campus, GlaxoSmithKline, Tres Cantos, Spain.

Aims: GSK3191607, a novel inhibitor of the Plasmodium falciparum ATP4 (PfATP4) pathway, is being considered for development in humans. However, a key problem encountered during the preclinical evaluation of the compound was its inconsistent pharmacokinetic (PK) profile across preclinical species (mouse, rat and dog), which prevented reliable prediction of PK parameters in humans and precluded a well-founded assessment of the potential for clinical development of the compound. Therefore, an open-label microdose (100 μg, six subjects) first time in humans study was conducted to assess the human PK of GSK3191607 following intravenous administration of [14C]-GSK3191607.

Methods: A human microdose study was conducted to investigate the clinical PK of GSK3191607 and enable a Go/No Go decision on further progression of the compound. The PK disposition parameters estimated from the microdose study, combined with preclinical in vitro and in vivo pharmacodynamic parameters, were all used to estimate the potential efficacy of various oral dosing regimens in humans.

Results: The PK profile, based on the microdose data, demonstrated a half-life (~17 h) similar to other antimalarial compounds currently in clinical development. However, combining the microdose data with the pharmacodynamic data provided results that do not support further clinical development of the compound for a single dose cure.

Conclusions: The information generated by this study provides a basis for predicting the expected oral PK profiles of GSK3191607 in man and supports decisions on the future clinical development of the compound.
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http://dx.doi.org/10.1111/bcp.13476DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5809343PMC
March 2018

A potent series targeting the malarial cGMP-dependent protein kinase clears infection and blocks transmission.

Nat Commun 2017 09 5;8(1):430. Epub 2017 Sep 5.

LifeArc, Accelerator Building, Open Innovation Campus, Stevenage, SG1 2FX, UK.

To combat drug resistance, new chemical entities are urgently required for use in next generation anti-malarial combinations. We report here the results of a medicinal chemistry programme focused on an imidazopyridine series targeting the Plasmodium falciparum cyclic GMP-dependent protein kinase (PfPKG). The most potent compound (ML10) has an IC of 160 pM in a PfPKG kinase assay and inhibits P. falciparum blood stage proliferation in vitro with an EC of 2.1 nM. Oral dosing renders blood stage parasitaemia undetectable in vivo using a P. falciparum SCID mouse model. The series targets both merozoite egress and erythrocyte invasion, but crucially, also blocks transmission of mature P. falciparum gametocytes to Anopheles stephensi mosquitoes. A co-crystal structure of PvPKG bound to ML10, reveals intimate molecular contacts that explain the high levels of potency and selectivity we have measured. The properties of this series warrant consideration for further development to produce an antimalarial drug.Protein kinases are promising drug targets for treatment of malaria. Here, starting with a medicinal chemistry approach, Baker et al. generate an imidazopyridine that selectively targets Plasmodium falciparum PKG, inhibits blood stage parasite growth in vitro and in mice and blocks transmission to mosquitoes.
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http://dx.doi.org/10.1038/s41467-017-00572-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5585294PMC
September 2017

Benzoxaborole Antimalarial Agents. Part 5. Lead Optimization of Novel Amide Pyrazinyloxy Benzoxaboroles and Identification of a Preclinical Candidate.

J Med Chem 2017 07 29;60(13):5889-5908. Epub 2017 Jun 29.

Shanghai ChemPartner , 998 Ha-lei Road, Zhangjiang High-tech Park, Pudong New Area, Shanghai 201203, China.

Carboxamide pyrazinyloxy benzoxaboroles were investigated with the goal to identify a molecule with satisfactory antimalarial activity, physicochemical properties, pharmacokinetic profile, in vivo efficacy, and safety profile. This optimization effort discovered 46, which met our target candidate profile. Compound 46 had excellent activity against cultured Plasmodium falciparum, and in vivo against P. falciparum and P. berghei in infected mice. It exhibited good PK properties in mice, rats, and dogs. It was highly active against the other 11 P. falciparum strains, which are mostly resistant to chloroquine and pyrimethamine. The rapid parasite in vitro reduction and in vivo parasite clearance profile of 46 were similar to those of artemisinin and chloroquine, two rapid-acting antimalarials. It was nongenotoxic in an Ames assay, an in vitro micronucleus assay, and an in vivo rat micronucleus assay when dosed orally up to 2000 mg/kg. The combined properties of this novel benzoxaborole support its progression to preclinical development.
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http://dx.doi.org/10.1021/acs.jmedchem.7b00621DOI Listing
July 2017

A tetraoxane-based antimalarial drug candidate that overcomes PfK13-C580Y dependent artemisinin resistance.

Nat Commun 2017 05 24;8:15159. Epub 2017 May 24.

Medicines for Malaria Venture, ICC, Route de Pré-Bois 20, P.O. Box 1826, 1215 Geneva, Switzerland.

K13 gene mutations are a primary marker of artemisinin resistance in Plasmodium falciparum malaria that threatens the long-term clinical utility of artemisinin-based combination therapies, the cornerstone of modern day malaria treatment. Here we describe a multinational drug discovery programme that has delivered a synthetic tetraoxane-based molecule, E209, which meets key requirements of the Medicines for Malaria Venture drug candidate profiles. E209 has potent nanomolar inhibitory activity against multiple strains of P. falciparum and P. vivax in vitro, is efficacious against P. falciparum in in vivo rodent models, produces parasite reduction ratios equivalent to dihydroartemisinin and has pharmacokinetic and pharmacodynamic characteristics compatible with a single-dose cure. In vitro studies with transgenic parasites expressing variant forms of K13 show no cross-resistance with the C580Y mutation, the primary variant observed in Southeast Asia. E209 is a superior next generation endoperoxide with combined pharmacokinetic and pharmacodynamic features that overcome the liabilities of artemisinin derivatives.
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http://dx.doi.org/10.1038/ncomms15159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5458052PMC
May 2017

Antimalarial efficacy of MMV390048, an inhibitor of phosphatidylinositol 4-kinase.

Sci Transl Med 2017 04;9(387)

Department of Veterinary Medicine, Armed Forces Research Institute of Medical Sciences, Bangkok 10400, Thailand.

As part of the global effort toward malaria eradication, phenotypic whole-cell screening revealed the 2-aminopyridine class of small molecules as a good starting point to develop new antimalarial drugs. Stemming from this series, we found that the derivative, MMV390048, lacked cross-resistance with current drugs used to treat malaria. This compound was efficacious against all life cycle stages, apart from late hypnozoites in the liver. Efficacy was shown in the humanized mouse model, and modest reductions in mouse-to-mouse transmission were achieved in the mouse model. Experiments in monkeys revealed the ability of MMV390048 to be used for full chemoprotection. Although MMV390048 was not able to eliminate liver hypnozoites, it delayed relapse in a monkey model. Both genomic and chemoproteomic studies identified a kinase of the parasite, phosphatidylinositol 4-kinase, as the molecular target of MMV390048. The ability of MMV390048 to block all life cycle stages of the malaria parasite suggests that this compound should be further developed and may contribute to malaria control and eradication as part of a single-dose combination treatment.
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http://dx.doi.org/10.1126/scitranslmed.aad9735DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5731459PMC
April 2017

A potent antimalarial benzoxaborole targets a Plasmodium falciparum cleavage and polyadenylation specificity factor homologue.

Nat Commun 2017 03 6;8:14574. Epub 2017 Mar 6.

Department of Medicine, University of California, Box 0811, San Francisco, California 94143, USA.

Benzoxaboroles are effective against bacterial, fungal and protozoan pathogens. We report potent activity of the benzoxaborole AN3661 against Plasmodium falciparum laboratory-adapted strains (mean IC 32 nM), Ugandan field isolates (mean ex vivo IC 64 nM), and murine P. berghei and P. falciparum infections (day 4 ED 0.34 and 0.57 mg kg, respectively). Multiple P. falciparum lines selected in vitro for resistance to AN3661 harboured point mutations in pfcpsf3, which encodes a homologue of mammalian cleavage and polyadenylation specificity factor subunit 3 (CPSF-73 or CPSF3). CRISPR-Cas9-mediated introduction of pfcpsf3 mutations into parental lines recapitulated AN3661 resistance. PfCPSF3 homology models placed these mutations in the active site, where AN3661 is predicted to bind. Transcripts for three trophozoite-expressed genes were lost in AN3661-treated trophozoites, which was not observed in parasites selected or engineered for AN3661 resistance. Our results identify the pre-mRNA processing factor PfCPSF3 as a promising antimalarial drug target.
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http://dx.doi.org/10.1038/ncomms14574DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5343452PMC
March 2017

Open Source Drug Discovery: Highly Potent Antimalarial Compounds Derived from the Tres Cantos Arylpyrroles.

ACS Cent Sci 2016 Oct 14;2(10):687-701. Epub 2016 Sep 14.

Donnelly Centre for Cellular and Biomolecular Research, University of Toronto , 160 College Street, Toronto, Ontario M5S 3E1, Canada.

The development of new antimalarial compounds remains a pivotal part of the strategy for malaria elimination. Recent large-scale phenotypic screens have provided a wealth of potential starting points for hit-to-lead campaigns. One such public set is explored, employing an open source research mechanism in which all data and ideas were shared in real time, anyone was able to participate, and patents were not sought. One chemical subseries was found to exhibit oral activity but contained a labile ester that could not be replaced without loss of activity, and the original hit exhibited remarkable sensitivity to minor structural change. A second subseries displayed high potency, including activity within gametocyte and liver stage assays, but at the cost of low solubility. As an open source research project, unexplored avenues are clearly identified and may be explored further by the community; new findings may be cumulatively added to the present work.
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http://dx.doi.org/10.1021/acscentsci.6b00086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5084075PMC
October 2016