Salinomycin and Other Ionophores as a New Class of Antimalarial Drugs with Transmission-Blocking Activity

ABSTRACTThe drug target profile proposed by the Medicines for Malaria Venture for a malaria elimination/eradication policy focuses on molecules active on both asexual and sexual stages ofPlasmodium, thus with both curative and transmission-blocking activities. The aim of the present work was to investigate whether the class of monovalent ionophores, which includes drugs used in veterinary medicine and that were recently proposed as human anticancer agents, meets these requirements. The activity of salinomycin, monensin, and nigericin onPlasmodium falciparumasexual and sexual erythrocytic stages and on the development of thePlasmodium bergheiandP. falciparummosquito stages is reported here. Gametocytogenesis of theP. falciparumstrain 3D7 was inducedin vitro, and gametocytes at stage II and III or stage IV and V of development were treated for different lengths of time with the ionophores and their viability measured with the parasite lactate dehydrogenase (pLDH) assay. The monovalent ionophores efficiently killed both asexual parasites and gametocytes with a nanomolar 50% inhibitory concentration (IC50). Salinomycin showed a fast speed of kill compared to that of standard drugs, and the potency was higher on stage IV and V than on stage II and III gametocytes. The ionophores inhibited ookinete development and subsequent oocyst formation in the mosquito midgut, confirming their transmission-blocking activity. Potential toxicity due to hemolysis was excluded, since only infected and not normal erythrocytes were damaged by ionophores. Our data strongly support the downstream exploration of monovalent ionophores for repositioning as new antimalarial and transmission-blocking leads.

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Evaluation of Two Sexual-stage Antigens as Bivalent Transmission-blocking Vaccines in Rodent Malaria

10.21203/rs.3.rs-154052/v1 ◽

2021 ◽

Author(s):

Fan Yang ◽

Fei Liu ◽

Xinxin Yu ◽

Wenqi Zheng ◽

Yudi Wu ◽

...

Keyword(s):

Fusion Protein ◽

Chimeric Protein ◽

Transmission Blocking ◽

Native Proteins ◽

Blocking Activity ◽

Antibody Titers ◽

Sexual Stages ◽

Transmission Blocking Vaccines

Abstract Background: Transmission-blocking vaccine (TBV) is a promising strategy for malaria elimination. It is hypothesized that mixing or fusing two antigens targeting different stages of sexual development may provide higher transmission-blocking activity than these antigens are used individually.Methods: We designed a chimeric protein composed of fragments of Pbg37 and PSOP25 and expressed the recombinant protein in Escherichia coli Rosetta-gami B (DE3). After immunizing mice with mixing or fusing recombinant proteins, the antibody titers of sera were analyzed by ELISA. IFA and Western blot were performed to test the reactivity of the antisera with the native proteins of the parasite. The transmission blocking activity were assessed in vitro and in vivo assay. Results: When Pbg37 and PSOP25 were co-administered in a mixture or as a fusion protein, they elicited similar antibody responses in mice as single antigens without causing immunological interference with each other. Antibodies against the mixed or fused antigens recognized the target proteins in the gametocyte, gamete, zygote and ookinete stages. The two bivalent vaccines (mixed proteins or a fusion protein) produced the superior TBA compared to that of the antibodies against individual antigens.Conclusions: There was no immunological interference between the two antigens of bivalent vaccines. And the bivalent vaccines produced significantly stronger transmission-blocking activities than single antigens. Altogether, these data provide the theoretical basis for the development of combination TBVs targeting different sexual stages.

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Baculovirus-Vectored Multistage Plasmodium vivax Vaccine Induces Both Protective and Transmission-Blocking Immunities against Transgenic Rodent Malaria Parasites

Infection and Immunity ◽

10.1128/iai.02040-14 ◽

2014 ◽

Vol 82 (10) ◽

pp. 4348-4357 ◽

Cited By ~ 24

Author(s):

Masanori Mizutani ◽

Mitsuhiro Iyori ◽

Andrew M. Blagborough ◽

Shinya Fukumoto ◽

Tomohiro Funatsu ◽

...

Keyword(s):

Fusion Protein ◽

Plasmodium Vivax ◽

Mammalian Cells ◽

Expression System ◽

Viral Envelope ◽

Vaccine Platform ◽

Transmission Blocking ◽

Content Type ◽

Sexual Stages

ABSTRACTA multistage malaria vaccine targeting the pre-erythrocytic and sexual stages ofPlasmodiumcould effectively protect individuals against infection from mosquito bites and provide transmission-blocking (TB) activity against the sexual stages of the parasite, respectively. This strategy could help prevent malaria infections in individuals and, on a larger scale, prevent malaria transmission in communities of endemicity. Here, we describe the development of a multistagePlasmodium vivaxvaccine which simultaneously expressesP. vivaxcircumsporozoite protein (PvCSP) and P25 (Pvs25) protein of this species as a fusion protein, thereby acting as a pre-erythrocytic vaccine and a TB vaccine, respectively. A new-concept vaccine platform based on the baculovirus dual-expression system (BDES) was evaluated. The BDES-Pvs25-PvCSP vaccine displayed correct folding of the Pvs25-PvCSP fusion protein on the viral envelope and was highly expressed upon transduction of mammalian cellsin vitro. This vaccine induced high levels of antibodies to Pvs25 and PvCSP and elicited protective (43%) and TB (82%) efficacies against transgenicP. bergheiparasites expressing the correspondingP. vivaxantigens in mice. Our data indicate that our BDES, which functions as both a subunit and DNA vaccine, can offer a promising multistage vaccine capable of delivering a potent antimalarial pre-erythrocytic and TB response via a single immunization regimen.

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In vitro antimalarial interaction and transmission-blocking activity of cryptolepine

Planta Medica ◽

10.1055/s-0036-1596329 ◽

2016 ◽

Vol 81 (S 01) ◽

pp. S1-S381

Author(s):

A Donkor Forkuo ◽

C Ansah ◽

B Gyan ◽

D Mancama ◽

A Theron

Keyword(s):

Transmission Blocking ◽

Blocking Activity

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N-Acetylglucosamine-1-Phosphate Transferase, WecA, as a Validated Drug Target in Mycobacterium tuberculosis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01310-17 ◽

2017 ◽

Vol 61 (11) ◽

Cited By ~ 6

Author(s):

Stanislav Huszár ◽

Vinayak Singh ◽

Alica Polčicová ◽

Peter Baráth ◽

María Belén Barrio ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Drug Target ◽

Functional Characterization ◽

Drug Candidate ◽

Content Type ◽

Chemical Libraries ◽

Whole Cells ◽

Encoding Gene

ABSTRACT The mycobacterial phosphoglycosyltransferase WecA, which initiates arabinogalactan biosynthesis in Mycobacterium tuberculosis, has been proposed as a target of the caprazamycin derivative CPZEN-45, a preclinical drug candidate for the treatment of tuberculosis. In this report, we describe the functional characterization of mycobacterial WecA and confirm the essentiality of its encoding gene in M. tuberculosis by demonstrating that the transcriptional silencing of wecA is bactericidal in vitro and in macrophages. Silencing wecA also conferred hypersensitivity of M. tuberculosis to the drug tunicamycin, confirming its target selectivity for WecA in whole cells. Simple radiometric assays performed with mycobacterial membranes and commercially available substrates allowed chemical validation of other putative WecA inhibitors and resolved their selectivity toward WecA versus another attractive cell wall target, translocase I, which catalyzes the first membrane step in the biosynthesis of peptidoglycan. These assays and the mutant strain described herein will be useful for identifying potential antitubercular leads by screening chemical libraries for novel WecA inhibitors.

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Triazolopyrimidinium salts: discovery of a new class of agents for cancer therapy

Future Medicinal Chemistry ◽

10.4155/fmc-2019-0317 ◽

2020 ◽

Vol 12 (5) ◽

pp. 387-402

Author(s):

Mariateresa Badolato ◽

Fabrizio Manetti ◽

Antonio Garofalo ◽

Francesca Aiello

Keyword(s):

Anticancer Agents ◽

Docking Studies ◽

In Vitro Models ◽

Sh2 Domain ◽

Activity Profile ◽

Cancer Cell Growth ◽

New Class ◽

Src Homology 2 ◽

Src Homology

Aim: The [1,2,4]triazolo[1,5- a]pyrimidine core is highly privileged in medicinal chemistry due to its versatile pharmacological activity profile. Recently, the search for novel anticancer agents has focused on [1,2,4]triazolo[1,5- a]pyrimidine derivatives. Results: Our hit functionalization has led to the discovery of new [1,2,4]triazolo[1,5- a]pyrimidinium salts with potential anticancer activity. Among a small library of molecules, compound 9 significantly inhibits cancer cell growth in a panel of in vitro models. Molecular docking studies and preliminary binding assay have displayed that 9 could directly bind the Src homology 2 (SH2) domain of STAT3 protein. Conclusion: Compound 9 is a novel promising lead compound that motivates additional evaluation of [1,2,4]triazolo[1,5- a]pyrimidinium salts as novel potential chemotherapeutics.

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DSM265 at 400 Milligrams Clears Asexual Stage Parasites but Not Mature Gametocytes from the Blood of Healthy Subjects Experimentally Infected with Plasmodium falciparum

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01837-18 ◽

2019 ◽

Vol 63 (4) ◽

Cited By ~ 10

Author(s):

Katharine A. Collins ◽

Thomas Rückle ◽

Suzanne Elliott ◽

Louise Marquart ◽

Emma Ballard ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Pharmacodynamic Modeling ◽

Dihydroorotate Dehydrogenase ◽

Transmission Blocking ◽

Content Type ◽

Blocking Activity ◽

Cutaneous Rash ◽

Phase 1B ◽

Study Support ◽

Previous Phase

ABSTRACT DSM265 is a novel antimalarial drug in clinical development that acts as a selective inhibitor of Plasmodium dihydroorotate dehydrogenase. In a previous phase 1b study, a single 150-mg dose of DSM265 showed partial efficacy against experimentally induced blood-stage Plasmodium falciparum malaria (IBSM). Pharmacokinetic/pharmacodynamic modeling predicted a human efficacious dose of 340 mg. The primary objectives of the current study were to determine the safety and efficacy of a single oral 400-mg dose of DSM265 against P. falciparum in the IBSM model. Eight healthy participants were inoculated intravenously with 2,800 parasites and treated with DSM265 7 days later. Unexpectedly, one participant did not develop parasitemia during the study. All other participants developed parasitemia, with the complete clearance of asexual parasites occurring following DSM265 treatment. All seven subjects also became gametocytemic. The secondary objectives were to investigate the gametocytocidal and transmission-blocking activity of a second 400-mg dose of DSM265, which was administered 23 days after inoculation. Gametocytes were not cleared by the second dose of DSM265, and transmission-blocking activity could not be determined due to low gametocyte densities. Three DSM265-related adverse events occurred, including a cutaneous rash in one subject on the day of the second DSM265 dose. The results obtained in this study support the prediction of the efficacious dose of DSM265 and provide further evidence that DSM265 is generally safe and well tolerated. In addition, this study confirms preclinical data indicating that DSM265 permits the development and maturation of gametocytes and does not clear mature circulating gametocytes. (This study has been registered at ClinicalTrials.gov under identifier NCT02573857.)

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Inhibition of LpxC Protects Mice from Resistant Acinetobacter baumannii by Modulating Inflammation and Enhancing Phagocytosis

mBio ◽

10.1128/mbio.00312-12 ◽

2012 ◽

Vol 3 (5) ◽

Cited By ~ 68

Author(s):

Lin Lin ◽

Brandon Tan ◽

Paul Pantapalangkoor ◽

Tiffany Ho ◽

Beverlie Baquir ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Gram Negative ◽

Content Type ◽

Novel Treatments ◽

New Class ◽

Virulent Strains ◽

Lethal Infection ◽

Tlr4 Activation ◽

Opsonophagocytic Killing

ABSTRACT New treatments are needed for extensively drug-resistant (XDR) Gram-negative bacilli (GNB), such as Acinetobacter baumannii. Toll-like receptor 4 (TLR4) was previously reported to enhance bacterial clearance of GNB, including A. baumannii. However, here we have shown that 100% of wild-type mice versus 0% of TLR4-deficient mice died of septic shock due to A. baumannii infection, despite having similar tissue bacterial burdens. The strain lipopolysaccharide (LPS) content and TLR4 activation by extracted LPS did not correlate with in vivo virulence, nor did colistin resistance due to LPS phosphoethanolamine modification. However, more-virulent strains shed more LPS during growth than less-virulent strains, resulting in enhanced TLR4 activation. Due to the role of LPS in A. baumannii virulence, an LpxC inhibitor (which affects lipid A biosynthesis) antibiotic was tested. The LpxC inhibitor did not inhibit growth of the bacterium (MIC > 512 µg/ml) but suppressed A. baumannii LPS-mediated activation of TLR4. Treatment of infected mice with the LpxC inhibitor enhanced clearance of the bacteria by enhancing opsonophagocytic killing, reduced serum LPS concentrations and inflammation, and completely protected the mice from lethal infection. These results identify a previously unappreciated potential for the new class of LpxC inhibitor antibiotics to treat XDR A. baumannii infections. Furthermore, they have far-reaching implications for pathogenesis and treatment of infections caused by GNB and for the discovery of novel antibiotics not detected by standard in vitro screens. IMPORTANCE Novel treatments are needed for infections caused by Acinetobacter baumannii, a Gram-negative bacterium that is extremely antibiotic resistant. The current study was undertaken to understand the immunopathogenesis of these infections, as a basis for defining novel treatments. The primary strain characteristic that differentiated virulent from less-virulent strains was shedding of Gram-negative lipopolysaccharide (LPS) during growth. A novel class of antibiotics, called LpxC inhibitors, block LPS synthesis, but these drugs do not demonstrate the ability to kill A. baumannii in vitro. We found that an LpxC inhibitor blocked the ability of bacteria to activate the sepsis cascade, enhanced opsonophagocytic killing of the bacteria, and protected mice from lethal infection. Thus, an entire new class of antibiotics which is already in development has heretofore-unrecognized potential to treat A. baumannii infections. Furthermore, standard antibiotic screens based on in vitro killing failed to detect this treatment potential of LpxC inhibitors for A. baumannii infections.

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Transmission of Artemisinin-Resistant Malaria Parasites to Mosquitoes under Antimalarial Drug Pressure

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00898-20 ◽

2020 ◽

Vol 65 (1) ◽

pp. e00898-20

Author(s):

Kathrin Witmer ◽

Farah A. Dahalan ◽

Michael J. Delves ◽

Sabrina Yahiya ◽

Oliver J. Watson ◽

...

Keyword(s):

Male Gamete ◽

Parasite Clearance ◽

Selective Advantage ◽

Multidrug Resistant ◽

Resistant Isolate ◽

Drug Pressure ◽

Content Type ◽

Sexual Stages ◽

Greater Mekong Subregion

ABSTRACTResistance to artemisinin-based combination therapy (ACT) in the Plasmodium falciparum parasite is threatening to reverse recent gains in reducing global deaths from malaria. While resistance manifests as delayed parasite clearance in patients, the phenotype can only spread geographically via the sexual stages and mosquito transmission. In addition to their asexual killing properties, artemisinin and its derivatives sterilize sexual male gametocytes. Whether resistant parasites overcome this sterilizing effect has not, however, been fully tested. Here, we analyzed P. falciparum clinical isolates from the Greater Mekong Subregion, each demonstrating delayed clinical clearance and known resistance-associated polymorphisms in the Kelch13 (PfK13var) gene. As well as demonstrating reduced asexual sensitivity to drug, certain PfK13var isolates demonstrated a marked reduction in sensitivity to artemisinin in an in vitro male gamete formation assay. Importantly, this same reduction in sensitivity was observed when the most resistant isolate was tested directly in mosquito feeds. These results indicate that, under artemisinin drug pressure, while sensitive parasites are blocked, resistant parasites continue transmission. This selective advantage for resistance transmission could favor acquisition of additional host-specificity or polymorphisms affecting partner drug sensitivity in mixed infections. Favored resistance transmission under ACT coverage could have profound implications for the spread of multidrug-resistant malaria beyond Southeast Asia.

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In VitroandIn VivoActivities of Three Oxazolidinones against Nonreplicating Mycobacterium tuberculosis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02410-14 ◽

2014 ◽

Vol 58 (6) ◽

pp. 3217-3223 ◽

Cited By ~ 35

Author(s):

Ming Zhang ◽

Claudia Sala ◽

Neeraj Dhar ◽

Anthony Vocat ◽

Vasan K Sambandamurthy ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Latent Tuberculosis ◽

Drug Susceptibility ◽

New Combination ◽

Drug Candidate ◽

Bacteriostatic Effect ◽

Content Type ◽

New Class ◽

Modest Activity

ABSTRACTOxazolidinones represent a new class of antituberculosis drugs that exert their function by inhibiting protein synthesis. Here, we compared the activities of three oxazolidinones, linezolid, PNU-100480, and AZD5847, against latent tuberculosis using a simple model employing the streptomycin-starvedMycobacterium tuberculosisstrain 18b. Thein vitrodrug susceptibility results showed that the three oxazolidinones had a bacteriostatic effect against actively growing bacilli but potent bactericidal activity against nonreplicating cells. In the murine model of latent infection withM. tuberculosis18b, the efficacy of the three compounds varied greatly. Indeed, AZD5847 or its prodrug exhibited no activity or only modest activity, respectively, after 2 months of treatment, whereas both linezolid and PNU-100480 were effective against latent bacilli in mice and showed promising outcomes in combination therapy with rifampin. Moreover, the potency of PNU-100480 was significantly greater than that of linezolid, making it an attractive drug candidate in the development of new combination therapies for latent tuberculosis.

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Manogepix (APX001A) In Vitro Activity against Candida auris: Head-to-Head Comparison of EUCAST and CLSI MICs

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00656-20 ◽

2020 ◽

Vol 64 (10) ◽

Cited By ~ 1

Author(s):

Maiken Cavling Arendrup ◽

Anuradha Chowdhary ◽

Karin Meinike Jørgensen ◽

Joseph Meletiadis

Keyword(s):

Efflux Pump ◽

Absolute Difference ◽

Low Grade ◽

Wild Type ◽

Candida Auris ◽

Content Type ◽

New Class ◽

Active Moiety ◽

Upper Limits

ABSTRACT Fosmanogepix is a novel prodrug in a new class of antifungal agents. Manogepix is the active moiety. We evaluated the CLSI and EUCAST MICs of manogepix and eight comparators against Candida auris. CLSI M27-A3 susceptibility testing of manogepix was performed for 122 C. auris isolates and compared to CLSI and EUCAST MICs for manogepix and eight comparators. Differences and agreement were calculated for each compound. Wild-type upper limits (WT-ULs; the upper MIC where the wild-type distribution ends) for manogepix and correlations with other drugs’ MICs were determined. Manogepix MICs (CLSI/EUCAST [mg/liter]) and WT-ULs were as follows: MIC50s, 0.008/0.016; MIC90s, 0.03/0.03; ranges, 0.001 to 0.25/0.001 to 0.125; 97.5% and 99% WT-ULs, 0.03/0.125 and 0.06/0.125, respectively. The manogepix CLSI/EUCAST MIC distributions spanned 9/8 dilutions, respectively. Significant correlation was found for all azoles, particularly fluconazole (r = 0.22 to 0.74, P < 0.05). Isolates with EUCAST manogepix MICs of ≤0.004 had 7.6-/10.2-fold-lower fluconazole CLSI/EUCAST MICs than the remaining isolates that had higher manogepix MICs. The highest essential agreement between CLSI and EUCAST results was observed for manogepix and fluconazole, with a median difference of −1 to 0 2-fold dilutions, 90th percentile absolute difference of 1, and 90 to 92% and 98 to 100% agreement within ±1 and ±2 dilutions. The lowest agreements within ±1 and ±2 dilutions were found for isavuconazole and anidulafungin (44 to 50% and 69 to 76%). The correlation between CLSI and EUCAST manogepix MICs against C. auris was excellent. Differential MICs were found, and these correlated with fluconazole MICs, suggesting that the C. auris population is a mix of wild-type isolates and non-wild-type isolates with low-grade manogepix MIC elevation, probably involving efflux pump expression. However, manogepix was the most potent agent against C. auris in this in vitro study.

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