Lerisetron Analogues with Antimalarial Properties: Synthesis, Structure-Activity Relationship Studies, and Biological Assessment.

A phenotypic whole cell high-throughput screen against the asexual blood and liver stages of the malaria parasite identified a benzimidazole chemical series. Among the hits were the antiemetic benzimidazole drug Lerisetron (IC NF54 = 0.81 μM) and its methyl-substituted analogue (IC NF54 = 0.

New Drugs for Human African Trypanosomiasis: A Twenty First Century Success Story.

The twentieth century ended with human African trypanosomiasis (HAT) epidemics raging across many parts of Africa. Resistance to existing drugs was emerging, and many programs aiming to contain the disease had ground to a halt, given previous success against HAT and the competing priorities associated with other medical crises ravaging the continent. A series of dedicated interventions and the introduction of innovative routes to develop drugs, involving Product Development Partnerships, has led to a dramatic turnaround in the fight against HAT caused by .

Anti-Trypanosomal Proteasome Inhibitors Cure Hemolymphatic and Meningoencephalic Murine Infection Models of African Trypanosomiasis.

Current anti-trypanosomal therapies suffer from problems of longer treatment duration, toxicity and inadequate efficacy, hence there is a need for safer, more efficacious and 'easy to use' oral drugs. Previously, we reported the discovery of the triazolopyrimidine (TP) class as selective kinetoplastid proteasome inhibitors with in vivo efficacy in mouse models of leishmaniasis, Chagas Disease and African trypanosomiasis (HAT). For the treatment of HAT, development compounds need to have excellent penetration to the brain to cure the meningoencephalic stage of the disease.

A dual fluorescent reporter line reveals in vitro malaria hypnozoite reactivation.

malaria is characterized by repeated episodes of blood stage infection (relapses) resulting from activation of dormant stages in the liver, so-called hypnozoites. Transition of hypnozoites into developing schizonts has never been observed. A barrier for studying this has been the lack of a system in which to monitor growth of liver stages.

Innovations in Addressing Pediatric Diarrhea in Low Resource Settings.

Diarrhea has long been recognized as an important cause of mortality during childhood. In parallel with ensuring access to proven care practices is the imperative to apply modern advances in medicine, science, and technology to accelerate progress against diarrheal disease, particularly in developing countries where the burden of avoidable harm is the greatest. In order to highlight achievements and identify outstanding areas of need, we reviewed the landscape of recent innovations that have significance for the study and clinical management of pediatric diarrhea in low resource settings.

NS5 from Dengue Virus Serotype 2 Can Adopt a Conformation Analogous to That of Its Zika Virus and Japanese Encephalitis Virus Homologues.

Flavivirus nonstructural protein 5 (NS5) contains an N-terminal methyltransferase (MTase) domain and a C-terminal polymerase (RNA-dependent RNA polymerase [RdRp]) domain fused through a 9-amino-acid linker. While the individual NS5 domains are structurally conserved, in the full-length protein, their relative orientations fall into two classes: the NS5 proteins from Japanese encephalitis virus (JEV) and Zika virus (ZIKV) adopt one conformation, while the NS5 protein from dengue virus serotype 3 (DENV3) adopts another. Here, we report a crystallographic structure of NS5 from DENV2 in a conformation similar to the extended one seen in JEV and ZIKV NS5 crystal structures.

Molecular basis of dengue virus serotype 2 morphological switch from 29°C to 37°C.

The ability of DENV2 to display different morphologies (hence different antigenic properties) complicates vaccine and therapeutics development. Previous studies showed most strains of laboratory adapted DENV2 particles changed from smooth to "bumpy" surfaced morphology when the temperature is switched from 29°C at 37°C. Here we identified five envelope (E) protein residues different between two alternative passage history DENV2 NGC strains exhibiting smooth or bumpy surface morphologies.

Generation of Transmission-Competent Human Malaria Parasites with Chromosomally-Integrated Fluorescent Reporters.

Malaria parasites have a complex life cycle that includes specialized stages for transmission between their mosquito and human hosts. These stages are an understudied part of the lifecycle yet targeting them is an essential component of the effort to shrink the malaria map. The human parasite Plasmodium falciparum is responsible for the majority of deaths due to malaria.

Quantitative Proteomic Analysis of Simian Primary Hepatocytes Reveals Candidate Molecular Markers for Permissiveness to Relapsing Malaria Plasmodium cynomolgi.

A major obstacle impeding malaria research is the lack of an in vitro system capable of supporting infection through the entire liver stage cycle of the parasite, including that of the dormant forms known as hypnozoites. Primary hepatocytes lose their liver specific functions in long-term in vitro culture. The malaria parasite Plasmodium initiates infection in hepatocyte.

Robust continuous in vitro culture of the Plasmodium cynomolgi erythrocytic stages.

The ability to culture pathogenic organisms substantially enhances the quest for fundamental knowledge and the development of vaccines and drugs. Thus, the elaboration of a protocol for the in vitro cultivation of the erythrocytic stages of Plasmodium falciparum revolutionized research on this important parasite. However, for P.

Hepatic spheroids used as an in vitro model to study malaria relapse.

Hypnozoites are the liver stage non-dividing form of the malaria parasite that are responsible for relapse and acts as a natural reservoir for human malaria Plasmodium vivax and P. ovale as well as a phylogenetically related simian malaria P. cynomolgi.

The liver-specific protein 2 (LISP2) is an early marker of liver stage development.

hypnozoites persist in the liver, cause malaria relapse and represent a major challenge to malaria elimination. Our previous transcriptomic study provided a novel molecular framework to enhance our understanding of the hypnozoite biology (Voorberg-van der Wel A, et al., 2017).

A suite of phenotypic assays to ensure pipeline diversity when prioritizing drug-like Cryptosporidium growth inhibitors.

Cryptosporidiosis is a leading cause of life-threatening diarrhea in children, and the only currently approved drug is ineffective in malnourished children and immunocompromised people. Large-scale phenotypic screens are ongoing to identify anticryptosporidial compounds, but optimal approaches to prioritize inhibitors and establish a mechanistically diverse drug development pipeline are unknown. Here, we present a panel of medium-throughput mode of action assays that enable testing of compounds in several stages of the Cryptosporidium life cycle.

Transcriptomic analysis reveals reduced transcriptional activity in the malaria parasite during progression into dormancy.

Relapses of dormant liver hypnozoites compromise malaria eradication efforts. New radical cure drugs are urgently needed, yet the vast gap in knowledge of hypnozoite biology impedes drug discovery. We previously unraveled the transcriptome of 6 to 7 day-old liver stages, highlighting pathways associated with hypnozoite dormancy (Voorberg-van der Wel et al.

Drug Discovery for Kinetoplastid Diseases: Future Directions.

Kinetoplastid parasites have caused human disease for millennia. Significant achievements have been made toward developing new treatments for leishmaniasis (particularly on the Indian subcontinent) and for human African trypanosomiasis (HAT). Moreover, the sustained decrease in the incidence of HAT has made the prospect of elimination a tantalizing reality.

A recombinant antibody against Plasmodium vivax UIS4 for distinguishing replicating from dormant liver stages.

Background: Plasmodium vivax is the most geographically widespread of the human malaria parasites, causing 50,000 to 100,000 deaths annually. Plasmodium vivax parasites have the unique feature of forming dormant liver stages (hypnozoites) that can reactivate weeks or months after a parasite-infected mosquito bite, leading to new symptomatic blood stage infections. Efforts to eliminate P.

Using a Virion Assembly-Defective Dengue Virus as a Vaccine Approach.

Dengue virus (DENV) is the most prevalent mosquito-transmitted viral pathogen in humans. The recently licensed dengue vaccine has major weaknesses. Therefore, there is an urgent need to develop improved dengue vaccines.

Discovery of Potent Non-nucleoside Inhibitors of Dengue Viral RNA-Dependent RNA Polymerase from Fragment Screening and Structure-Guided Design.

Flavivirus NS5 RNA-dependent RNA polymerase (RdRp) is an important drug target. Whilst a number of allosteric inhibitors have been described for Hepatitis C virus RdRp, few have been described for DENV RdRp. In addition, compound screening campaigns have not yielded suitable leads for this enzyme.

The Dengue Virus Replication Complex: From RNA Replication to Protein-Protein Interactions to Evasion of Innate Immunity.

Viruses from the Flavivirus family are the causative agents of dengue fever, Zika, Japanese encephalitis, West Nile encephalitis or Yellow fever and constitute major or emerging public health problems. A better understanding of the flavivirus replication cycle is likely to offer new opportunities for the design of antiviral therapies to treat severe conditions provoked by these viruses, but it should also help reveal fundamental biological mechanisms of the host cell. During virus replication, RNA synthesis is mediated by a dynamic and membrane-bound multi-protein assembly, named the replication complex (RC).

Structure-activity relationship of uridine-based nucleoside phosphoramidate prodrugs for inhibition of dengue virus RNA-dependent RNA polymerase.

To identify a potent and selective nucleoside inhibitor of dengue virus RNA-dependent RNA polymerase, a series of 2'- and/or 4'-ribose sugar modified uridine nucleoside phosphoramidate prodrugs and their corresponding triphosphates were synthesized and evaluated. Replacement of 2'-OH with 2'-F led to be a poor substrate for both dengue virus and human mitochondrial RNA polymerases. Instead of 2'-fluorination, the introduction of fluorine at the ribose 4'-position was found not to affect the inhibition of the dengue virus polymerase with a reduction in uptake by mitochondrial RNA polymerase.

Imidazolopiperazines Kill both Rings and Dormant Rings in Wild-Type and K13 Artemisinin-Resistant Plasmodium falciparum In Vitro.

Artemisinin (ART) resistance has spread through Southeast Asia, posing a serious threat to the control and elimination of malaria. ART resistance has been associated with mutations in the kelch-13 () propeller domain. Phenotypically, ART resistance is defined as delayed parasite clearance in patients due to the reduced susceptibility of early ring-stage parasites to the active metabolite of ART dihydroartemisinin (DHA).

Development of a Cytopathic Effect-Based Phenotypic Screening Assay against Cryptosporidium.

Cryptosporidiosis is a diarrheal disease predominantly caused by Cryptosporidium parvum ( Cp) and Cryptosporidium hominis ( Ch), apicomplexan parasites which infect the intestinal epithelial cells of their human hosts. The only approved drug for cryptosporidiosis is nitazoxanide, which shows limited efficacy in immunocompromised children, the most vulnerable patient population. Thus, new therapeutics and in vitro infection models are urgently needed to address the current unmet medical need.

A phase 1 evaluation of the pharmacokinetic/pharmacodynamic interaction of the anti-malarial agents KAF156 and piperaquine.

Background: KAF156 is a novel imidazolopiperazine anti-malarial with activity against pre-erythrocytic liver stages, asexual and sexual blood stages. Based on in vitro data, a two-way pharmacokinetic interaction was hypothesized for KAF156 use in combination with piperaquine (PPQ) as both drugs are CYP3A4 substrates and inhibitors. Potential combination effects on the QT interval were also assessed.