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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 the Plasmodium falciparum cyclic amine resistance locus (PfCARL) and P. falciparum acetyl CoA transporter (PfACT), 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 targets are unknown. The tyramine of (S)-SW703 is shared with some reported PfCARL-associated compounds; however, we observed that strict S-stereochemistry was required for the activity of (S)-SW703, suggesting differences in the mechanism of action or binding mode. (S)-SW703 provides a new chemical series with broad activity for multiple life-cycle stages and a fast-killing mechanism of action, available for lead optimization to generate new treatments for malaria.

The development of new antimalarials is required because of the threat of resistance to current antimalarial therapies. To discover new antimalarial chemotypes, we screened the Janssen Jumpstarter library against the P. falciparum asexual parasite and identified the 7-N-substituted-3-oxadiazole quinolone hit class. We established the structure-activity relationship and optimized the antimalarial potency. The optimized analog WJM228 (17) showed robust metabolic stability in vitro, although the aqueous solubility was limited. Forward genetic resistance studies uncovered that WJM228 targets the Qo site of cytochrome b (cyt b), an important component of the mitochondrial electron transport chain (ETC) that is essential for pyrimidine biosynthesis and an established antimalarial target. Profiling against drug-resistant parasites confirmed that WJM228 confers resistance to the Qo site but not Qi site mutations, and in a biosensor assay, it was shown to impact the ETC via inhibition of cyt b. Consistent with other cyt b targeted antimalarials, WJM228 prevented pre-erythrocytic parasite and male gamete development and reduced asexual parasitemia in a P. berghei mouse model of malaria. Correcting the limited aqueous solubility and the high susceptibility to cyt b Qo site resistant parasites found in the clinic will be major obstacles in the future development of the 3-oxadiazole quinolone antimalarial class.

BackgroundInsurance benefit design influences whether individuals with diabetes who require a continuous glucose monitor (CGM) to provide real-time feedback on their blood glucose levels can obtain the CGM device from either a pharmacy or a durable medical equipment supplier. The impact of the acquisition channel on device adherence and health care costs has not been systematically evaluated. ObjectiveThis study aims to compare the adherence rates for patients new to CGM therapy and the costs of care for individuals who obtained CGM devices from a pharmacy versus acquisition through a durable medical equipment supplier using retrospective claims analysis. MethodsUsing the Mariner commercial claims database, individuals aged >18 years with documented diabetes and an initial CGM claim during the first quarter of 2021 (2021 Q1, index date) were identified. Patients had to maintain uninterrupted enrollment for a duration of 15 months but file no CGM claim during the 6 months preceding the index date. We used direct matching to establish comparable pharmacy and durable medical equipment cohorts. Outcomes included quarterly adherence, reinitiation, and costs for the period from 2021 Q1 to the third quarter of 2022 (2022 Q3). Between-cohort differences in adherence rates and reinitiation rates were analyzed using z tests, and cost differences were analyzed using 2-tailed t tests. ResultsDirect matching was used to establish comparable pharmacy and durable medical equipment cohorts. A total of 2356 patients were identified, with 1178 in the pharmacy cohort and 1178 in the durable medical equipment cohorts. Although adherence declined over time in both cohorts, the durable medical equipment cohort exhibited significantly superior adherence compared to the pharmacy cohort at 6 months (pharmacy n=615, 52% and durable medical equipment n=761, 65%; P

New antimalarial drug candidates that act via novel mechanisms are urgently needed to combat malaria drug resistance. Here, we describe the multi-omic chemical validation of Plasmodium M1 alanyl metalloaminopeptidase as an attractive drug target using the selective inhibitor, MIPS2673. MIPS2673 demonstrated potent inhibition of recombinant Plasmodium falciparum (PfA-M1) and Plasmodium vivax (PvA-M1) M1 metalloaminopeptidases, with selectivity over other Plasmodium and human aminopeptidases, and displayed excellent in vitro antimalarial activity with no significant host cytotoxicity. Orthogonal label-free chemoproteomic methods based on thermal stability and limited proteolysis of whole parasite lysates revealed that MIPS2673 solely targets PfA-M1 in parasites, with limited proteolysis also enabling estimation of the binding site on PfA-M1 to within ~5 Å of that determined by X-ray crystallography. Finally, functional investigation by untargeted metabolomics demonstrated that MIPS2673 inhibits the key role of PfA-M1 in haemoglobin digestion. Combined, our unbiased multi-omic target deconvolution methods confirmed the on-target activity of MIPS2673, and validated selective inhibition of M1 alanyl metalloaminopeptidase as a promising antimalarial strategy.

New antimalarial treatments with novel mechanism of action are needed to tackle Plasmodium falciparum infections that are resistant to first-line therapeutics. Here we report the exploration of MMV692140 (2) from the Pathogen Box, a collection of 400 compounds that was made available by Medicines for Malaria Venture (MMV) in 2015. Compound 2 was profiled in in vitro models of malaria and was found to be active against multiple life-cycle stages of Plasmodium parasites. The mode of resistance, and putatively its mode of action, was identified as Plasmodium falciparum translation elongation factor 2 (PfeEF2), which is responsible for the GTP-dependent translocation of the ribosome along mRNA. The compound maintains activity against a series of drug-resistant parasite strains. The structural motif of the tetrahydroquinoline (2) was explored in a chemistry program with its structure-activity relationships examined, resulting in the identification of an analog with 30-fold improvement of antimalarial asexual blood stage potency.

INTRODUCTION 1736 I. WHY APPLY THE RULES TO BENCH TRIALS? 1740 A. Reasons for Applying the Rules 1741 B. Reasons for Not Applying the Rules, and Responses 1745 1. The [...]

In this non-empirical article, which is intended as a decision-making resource for researchers, we identify issues surrounding data integrity that commonly arise in online survey research and we propose remediation strategies based on challenges we encountered during a particular pilot study as well as our collective experience with conducting online survey research. Using the metaphor of an onion, we peel off the layers of this complex problem, synthesize the various available strategies used across disciplines, and propose some novel ones based on our perspective as psychologists. Corresponding to this multi-layered problem, we propose multi-layered solutions to prevent illegitimate responding—by both humans and non-humans (robots or “bots” for short)—from compromising the quality of data collected via online survey research. The first layer entails strategic item selection and protective programming in survey development. The second layer involves astute advertising and recruitment tactics to minimize illegitimate responses during survey dissemination. The third layer includes algorithms and other mechanisms to identify suspicious responses for possible exclusion during data verification. When we peel off the layers and reach the core problem of illegitimate responses to online surveys—financial incentives—we will propose ways of navigating respondent reimbursement to mitigate their inadvertent harmful impacts on the research process. By proposing these solutions, we aim to protect the integrity of scientific inquiry in psychology, especially given how often this method is used in the discipline.

ABSTRACT To combat the global burden of malaria, development of new drugs to replace or complement current therapies is urgently required. Here, we show that the compound MMV1557817 is a selective, nanomolar inhibitor of both Plasmodium falciparum and Plasmodium vivax aminopeptidases M1 and M17, leading to inhibition of end-stage hemoglobin digestion in asexual parasites. MMV1557817 can kill sexual-stage P. falciparum, is active against murine malaria, and does not show any shift in activity against a panel of parasites resistant to other antimalarials. MMV1557817-resistant P. falciparum exhibited a slow growth rate that was quickly outcompeted by wild-type parasites and were sensitized to the current clinical drug, artemisinin. Overall, these results confirm MMV1557817 as a lead compound for further drug development and highlights the potential of dual inhibition of M1 and M17 as an effective multi-species drug-targeting strategy.IMPORTANCEEach year, malaria infects approximately 240 million people and causes over 600,000 deaths, mostly in children under 5 years of age. For the past decade, artemisinin-based combination therapies have been recommended by the World Health Organization as the standard malaria treatment worldwide. Their widespread use has led to the development of artemisinin resistance in the form of delayed parasite clearance, alongside the rise of partner drug resistance. There is an urgent need to develop and deploy new antimalarial agents with novel targets and mechanisms of action. Here, we report a new and potent antimalarial compound, known as MMV1557817, and show that it targets multiple stages of the malaria parasite lifecycle, is active in a preliminary mouse malaria model, and has a novel mechanism of action. Excitingly, resistance to MMV15578117 appears to be self-limiting, suggesting that development of the compound may provide a new class of antimalarial.

Antimalarial resistance to the first-line partner drug piperaquine (PPQ) threatens the effectiveness of artemisinin-based combination therapy. In vitro piperaquine resistance is characterized by incomplete growth inhibition, i.e. increased parasite growth at higher drug concentrations. However, the 50% inhibitory concentrations (IC50) remain relatively stable across parasite lines. Measuring parasite viability of a drug-resistant Cambodian Plasmodium falciparum isolate in a parasite reduction ratio (PRR) assay helped to better understand the resistance phenotype towards PPQ. In this parasite isolate, incomplete growth inhibition translated to only a 2.5-fold increase in IC50 but a dramatic decrease of parasite killing in the PRR assay. Hence, this pilot study reveals the potential of in vitro parasite viability assays as an important, additional tool when it comes to guiding decision-making in preclinical drug development and post approval. To the best of our knowledge, this is the first time that a compound was tested against a drug-resistant parasite in the in vitro PRR assay.

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 (PfYRS). 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.

The Plasmodium falciparum proteasome is a potential antimalarial drug target. We have identified a series of amino-amide boronates that are potent and specific inhibitors of the P. falciparum 20S proteasome (Pf20S) β5 active site and that exhibit fast-acting antimalarial activity. They selectively inhibit the growth of P. falciparum compared with a human cell line and exhibit high potency against field isolates of P. falciparum and Plasmodium vivax They have a low propensity for development of resistance and possess liver stage and transmission-blocking activity. Exemplar compounds, MPI-5 and MPI-13, show potent activity against P. falciparum infections in a SCID mouse model with an oral dosing regimen that is well tolerated. We show that MPI-5 binds more strongly to Pf20S than to human constitutive 20S (Hs20Sc). Comparison of the cryo-electron microscopy (EM) structures of Pf20S and Hs20Sc in complex with MPI-5 and Pf20S in complex with the clinically used anti-cancer agent, bortezomib, reveal differences in binding modes that help to explain the selectivity. Together, this work provides insights into the 20S proteasome in P. falciparum, underpinning the design of potent and selective antimalarial proteasome inhibitors.

The decision to issue a preliminary injunction is enormously consequential; it has been likened to “judgment and execution before trial.” Yet, courts regularly say that our primary tool for promoting truth seeking at trial—the Federal Rules of Evidence—does not apply at preliminary injunction hearings. Judges frequently consider inadmissible evidence to make what may be the most important ruling in the case. This Article critically examines this widespread evidentiary practice.In critiquing courts’ justifications for abandoning the Rules in the preliminary injunction context, this Article introduces a new concept: “meta-evidence.” Meta-evidence is evidence of what evidence will be presented at trial. I demonstrate that much evidence introduced at the preliminary injunction stage is, in fact, meta-evidence. And I show why meta-evidence that initially appears inadmissible under the Rules is often, in fact, admissible. Applying the Rules at the preliminary injunction stage, then, would not exclude nearly as much evidence as courts may have assumed.I offer two proposals for how courts should use the Rules at the preliminary injunction phase. More ambitiously, I suggest courts should apply the Rules with an exception directly tailored to the dangers of limiting admissible evidence when the parties are under time pressure. Alternatively, I suggest that courts simply recognize when evidence is actually meta-evidence and weigh it appropriately. Courts should acknowledge that meta-evidence is probative only to the extent it tends to show the proponent will produce admissible evidence at trial.

Thanks to its expertise in clinical research, epidemiology, infectious diseases, microbiology, parasitology, public health, translational research and tropical medicine, coupled with deeply rooted partnerships with institutions in low- and middle-income countries (LMICs), the Swiss Tropical and Public Health Institute (Swiss TPH) has been a key contributor in many drug research and development consortia involving academia, pharma and product development partnerships. Our know-how of the maintenance of parasites and their life-cycles in the laboratory, plus our strong ties to research centres and disease control programme managers in LMICs with access to field sites and laboratories, have enabled systems for drug efficacy testing in vitro and in vivo, clinical research, and modelling to support the experimental approaches. Thus, Swiss TPH has made fundamental contributions towards the development of new drugs – and the better use of old drugs – for neglected tropical diseases and infectious diseases of poverty, such as Buruli ulcer, Chagas disease, food-borne trematodiasis (e.g. clonorchiasis, fascioliasis and opisthorchiasis), human African trypanosomiasis, leishmaniasis, malaria, schistosomiasis, soil-transmitted helminthiasis and tuberculosis. In this article, we show case the success stories of molecules to which Swiss TPH has made a substantial contribution regarding their use as anti-infective compounds with the ultimate aim to improve people’s health and well-being.

Here, de Vries et al. perform a pre-clinical characterization of the antimalarial compound MMV693183: the compound targets acetyl-CoA synthetase, has efficacy in humanized mice against Plasmodium falciparum infection, blocks transmission to mosquito vectors, is safe in rats, and pharmacokinetic-pharmacodynamic modeling informs about a potential oral human dosing regimen.

The Plasmodium falciparum cytoplasmic tyrosine tRNA synthetase (PfTyrRS) is an attractive drug target that is susceptible to reaction-hijacking by AMP-mimicking nucleoside sulfamates. We previously identified an exemplar pyrazolopyrimidine ribose sulfamate, ML901, as a potent reaction hijacking inhibitor of PfTyrRS. Here we examined the stage specificity of action of ML901, showing very good activity against the schizont stage, but lower trophozoite stage activity. We explored a series of ML901 analogues and identified ML471, which exhibits improved potency against trophozoites and enhanced selectivity against a human cell line. Additionally, it has no inhibitory activity against human ubiquitin-activating enzyme (UAE) in vitro. ML471 exhibits low nanomolar activity against asexual blood stage P. falciparum and potent activity against liver stage parasites, gametocytes and transmissible gametes. It is fast-acting and exhibits a long in vivo half-life. ML471 is well-tolerated and shows single dose oral efficacy in the SCID mouse model of P. falciparum malaria. We confirm that ML471 is a reaction hijacking inhibitor that is converted into a tight binding Tyr-ML471 conjugate by the PfTyrRS enzyme. A crystal structure of the PfTyrRS/ Tyr-ML471 complex offers insights into improved potency, while molecular docking into UAE provides a rationale for improved selectivity. Author summary: Malaria is a devastating disease caused by the Plasmodium parasite, with more than 200 million cases and 600,000 deaths reported in 2022. Worryingly, the emergence of clinically artemisinin-resistant P. falciparum was first identified in Southeast Asia and more recently detected in Africa. This imposes a significant burden on the healthcare systems of the world's poorest countries. This study continues our previous effort to develop a series of nucleoside sulfamates that targets the P. falciparum cytoplasmic tyrosine tRNA synthetase (PfTyrRS), via a reaction hijacking mechanism. We explored the potency and selectivity of nucleoside sulfamate derivatives and identified a front runner compound, ML471, that shows potent activity against malaria parasites but low toxicity to human cells. Moreover, ML471 shows activity against multiple life stages of the parasite and exhibits single-dose oral efficacy in the SCID mouse model of P. falciparum malaria. We confirmed ML471 is a potent reaction hijacking inhibitor that is converted to Tyr-ML471 by the recombinant PfTyrRS enzyme. The crystal structure of Tyr-ML471 bound PfTyrRS offers molecular insights that could guide future drug design. Taken together, our findings provide a promising direction for developing new antimalarials. [ABSTRACT FROM AUTHOR]

We describe our work resulting in the selection of ACT-451840 ( 38 ) as a novel antimalarial drug with a novel mode of action. The compound was broadly characterized in vitro as well as in vivo in rat PK experiments as well as two different mouse malaria models. In the P. berghei infected mouse model cure could be achieved at oral doses of 300 mg/kg over 3 consecutive days. ACT-451840 was clinically investigated up to an experimental human malaria infection model, where therapeutic effects could be shown.

Background and objectives: For decades, dengue outbreaks have been affecting vast territories of the Americas. In 2010’s decade, Chikungunya and Zika virus (CHIKV and ZIKV) emerged as new arboviruses in the region. While several seroprevalence rates have been reported for dengue virus (DENV) infection in Brazil, serological surveys for the latest are scarce. We aimed to evaluate the seroprevalence of CHIKV, ZIKV, and DENV infections in pregnant women at admission to a public maternity hospital of Nova Iguaçu, state of Rio de Janeiro. Methods: A simple questionnaire was applied, containing limited demographic, obstetric, and clinical data, alongside with blood collection. Different commercial test kits, based on enzyme-linked immunosorbent assay (ELISA), were used. Results: Among 349 pregnant women enrolled from July to December 2017, there was a 28.4% seroreactivity for CHIKV, 47.2% for ZIKV, and 88.8% for DENV. Conclusion: These findings reflect the high dengue endemicity scenario and suggest a significant reach of the recent outbreaks of ZIKV and CHIKV infections in the region.

Hitz et al. describe the role of the protein kinase PfCK2α in the development of the human malaria parasite Plasmodium falciparum. Using mutant parasites, they show that PfCK2α is not only essential for asexual but also sexual development of P. falciparum blood stage parasites, and hence it may hold promise as a potential target for antimalarial drugs.

Abstract Background Emergence of anti-malarial drug resistance and perpetual increase in malaria incidence necessitates the development of novel anti-malarials. Histone deacetylases (HDAC) has been shown to be a promising target for malaria, despite this, there are no HDAC inhibitors in clinical trials for malaria treatment. This can be attributed to the poor pharmacokinetics, bioavailability and selectivity of the HDAC inhibitors. Methods A collection of HDAC inhibitors were screened for anti-malarial activity, and the best candidate was profiled in parasite-killing kinetics, growth inhibition of sensitive and multi-drug resistant (MDR) strains and against gametocytes. Absorption, distribution, metabolism and excretion pharmacokinetics (ADME-PK) parameters of FNDR-20123 were determined, and in vivo efficacy was studied in a mouse model for Plasmodium falciparum infection. Results A compound library of HDAC inhibitors (180 in number) was screened for anti-malarial activity, of which FNDR-20123 was the most potent candidate. The compound had been shown to inhibit Plasmodium HDAC with IC50 of 31 nM and human HDAC with IC50 of 3 nM. The IC50 obtained for P. falciparum in asexual blood-stage assay was 42 nM. When compared to atovaquone and pyrimethamine, the killing profiles of FNDR-20123 were better than atovaquone and comparable to pyrimethamine. The IC50 values for the growth inhibition of sensitive and MDR strains were similar, indicating that there is no cross-resistance and a low risk of resistance development. The selected compound was also active against gametocytes, indicating a potential for transmission control: IC50 values being 190 nM for male and > 5 µM for female gametocytes. FNDR-20123 is a stable candidate in human/mouse/rat liver microsomes (> 75% remaining post 2-h incubation), exhibits low plasma protein binding (57% in humans) with no human Ether-à-go–go-Related Gene (hERG) liability (> 100 µM), and does not inhibit any of the cytochrome P450 (CYP) isoforms tested (IC50 > 25 µM). It also shows negligible cytotoxicity to HepG-2 and THP-1 cell lines. The oral pharmacokinetics in rats at 100 mg/kg body weight shows good exposures (Cmax = 1.1 µM) and half-life (T1/2 = 5.5 h). Furthermore, a 14-day toxicokinetic study at 100 mg/kg daily dose did not show any abnormality in body weight or gross organ pathology. FNDR-20123 is also able to reduce parasitaemia significantly in a mouse model for P. falciparum infection when dosed orally and subcutaneously. Conclusion FNDR-20123 may be a suitable candidate for the treatment of malaria, which can be further developed.

Introdução/Objetivo: A escolha apropriada da terapia empírica para infecções urinárias depende do conhecimento dos padrões locais de sensibilidade bacteriana. O objetivo do presente estudo foi avaliar a prevalência e o perfil de sensibilidade antimicrobiana de uropatógenos comunitários e hospitalares observados em cidades da Amazônia Legal. Métodos: Foram avaliadas todas as espécies bacterianas isoladas em uroculturas analisadas em um laboratório clínico da cidade de São Luís, Maranhão, no período de junho a novembro de 2015 (exames de origem comunitária e hospitalar provenientes de serviços públicos e privados da cidade de São Luís e do interior do estado do Maranhão). A identificação dos microrganismos foi feita através da técnica de MALDI-TOF MS (matrix-assisted laser desorption ionization-time of flight mass spectrometry), e a sensibilidade antimicrobiana foi determinada por sistema automatizado. Resultados: Um total de 1690 uroculturas positivas foram analisadas, sendo 78,8% de origem comunitária e 21,2% de origem hospitalar. A idade média dos pacientes foi de 43,2 ± 26,3 anos, e 73,8% eram do sexo feminino. Escherichia coli foi a espécie mais frequentemente isolada. A prevalência de bacilos Gram negativos não fermentadores de glicose foi maior entre os pacientes do sexo masculino e entre os de origem hospitalar (p < 0,001). O percentual de resistência das enterobactérias comunitárias foi de 15,2% para ceftriaxone, 29,6% para ciprofloxacino e inferior a 1,5% para carbapenêmicos e amicacina. A prevalência de resistência a ceftriaxone e ciprofloxacino foi maior entre pacientes do sexo masculino (OR (Odds Ratio): 2,62; IC (intervalo de confiança) 95%: 1,98-3,47 e OR: 2,65; IC 95%: 2,04-3,43, respectivamente) e idosos (OR: 2,56; IC 95%: 1,95-3,35 e OR: 2,88; IC 95%: 2,25-3,67, respectivamente). A sensibilidade de Pseudomonas spp. e Acinetobacter spp. a meropenem foi superior a 90%. Maiores níveis de resistência foram encontrados entre as amostras hospitalares; no entanto, a sensibilidade a amicacina foi elevada para a maioria das espécies isoladas de bacilos Gram negativos. Conclusão: Enterobactérias foram os uropatógenos mais frequentemente isolados. De forma geral, as bactérias isoladas em amostras hospitalares apresentaram níveis mais elevados de resistência. Entre os exames comunitários, ressalta-se a alta resistência das enterobactérias a antibióticos frequentemente utilizados no tratamento das infecções urinárias, como ciprofloxacino e ceftriaxone.

With artemisinin-resistant Plasmodium falciparum parasites emerging in Africa, the need for new antimalarial chemotypes is persistently high. The ideal pharmacodynamic parameters of a candidate drug are a rapid onset of action and a fast rate of parasite killing or clearance. To determine these parameters, it is essential to discriminate viable from nonviable parasites, which is complicated by the fact that viable parasites can be metabolically inactive, whilst dying parasites can still be metabolically active and morphologically unaffected. Standard growth inhibition assays, read out via microscopy or [3H] hypoxanthine incorporation, cannot reliably discriminate between viable and nonviable parasites. Conversely, the in vitro parasite reduction ratio (PRR) assay is able to measure viable parasites with high sensitivity. It provides valuable pharmacodynamic parameters, such as PRR, 99.9% parasite clearance time (PCT99.9%) and lag phase. Here we report the development of the PRR assay version 2 (V2), which comes with a shorter assay duration, optimized quality controls and an objective, automated analysis pipeline that systematically estimates PRR, PCT99.9% and lag time and returns meaningful secondary parameters such as the maximal killing rate of a drug (Emax) at the assayed concentration. These parameters can be fed directly into pharmacokinetic/pharmacodynamic models, hence aiding and standardizing lead selection, optimization, and dose prediction.

There is an urgent need for new drugs to treat malaria, with broad therapeutic potential and novel modes of action, to widen the scope of treatment and to overcome emerging drug resistance. Here we describe the discovery of DDD107498, a compound with a potent and novel spectrum of antimalarial activity against multiple life-cycle stages of the Plasmodium parasite, with good pharmacokinetic properties and an acceptable safety profile. DDD107498 demonstrates potential to address a variety of clinical needs, including single-dose treatment, transmission blocking and chemoprotection. DDD107498 was developed from a screening programme against blood-stage malaria parasites; its molecular target has been identified as translation elongation factor 2 (eEF2), which is responsible for the GTP-dependent translocation of the ribosome along messenger RNA, and is essential for protein synthesis. This discovery of eEF2 as a viable antimalarial drug target opens up new possibilities for drug discovery.

Cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) signalling is essential for the proliferation of Plasmodium falciparum malaria blood stage parasites. The mechanisms regulating the activity of the catalytic subunit PfPKAc, however, are only partially understood, and PfPKAc function has not been investigated in gametocytes, the sexual blood stage forms that are essential for malaria transmission. By studying a conditional PfPKAc knockdown (cKD) mutant, we confirm the essential role for PfPKAc in erythrocyte invasion by merozoites and show that PfPKAc is involved in regulating gametocyte deformability. We furthermore demonstrate that overexpression of PfPKAc is lethal and kills parasites at the early phase of schizogony. Strikingly, whole genome sequencing (WGS) of parasite mutants selected to tolerate increased PfPKAc expression levels identified missense mutations exclusively in the gene encoding the parasite orthologue of 3-phosphoinositide-dependent protein kinase-1 (PfPDK1). Using targeted mutagenesis, we demonstrate that PfPDK1 is required to activate PfPKAc and that T189 in the PfPKAc activation loop is the crucial target residue in this process. In summary, our results corroborate the importance of tight regulation of PfPKA signalling for parasite survival and imply that PfPDK1 acts as a crucial upstream regulator in this pathway and potential new drug target.