RESUMO
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 Plasmodium 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.
Assuntos
Antimaláricos/farmacologia , Quimioprevenção , Descoberta de Drogas , Malária/prevenção & controle , Plasmodium/efeitos dos fármacos , Antimaláricos/química , Antimaláricos/isolamento & purificação , Antimaláricos/uso terapêutico , Avaliação Pré-Clínica de Medicamentos , Humanos , Mitocôndrias/efeitos dos fármacos , Plasmodium/crescimento & desenvolvimentoRESUMO
The potential of azaaurones as dual-stage antimalarial agents was investigated by assessing the effect of a small library of azaaurones on the inhibition of liver and intraerythrocytic lifecycle stages of the malaria parasite. The whole series was screened against the blood stage of a chloroquine-resistant Plasmodium falciparum strain and the liver stage of P.â berghei, yielding compounds with dual-stage activity and sub-micromolar potency against erythrocytic parasites. Studies with genetically modified parasites, using a phenotypic assay based on the P.â falciparum Dd2-ScDHODH line, which expresses yeast dihydroorotate dehydrogenase (DHODH), showed that one of the azaaurone derivatives has the potential to inhibit the parasite mitochondrial electron-transport chain. The global urgency in finding new therapies for malaria, especially against the underexplored liver stage, associated with chemical tractability of azaaurones, warrants further development of this chemotype. Overall, these results emphasize the azaaurone chemotype as a promising scaffold for dual-stage antimalarials.
Assuntos
Antimaláricos/química , Antimaláricos/farmacologia , Complexos de Coordenação/farmacologia , Eritrócitos/efeitos dos fármacos , Eritrócitos/parasitologia , Fígado/efeitos dos fármacos , Fígado/parasitologia , Plasmodium berghei/efeitos dos fármacos , Plasmodium falciparum/efeitos dos fármacos , Antimaláricos/síntese química , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Relação Dose-Resposta a Droga , Células HEK293 , Humanos , Estrutura Molecular , Testes de Sensibilidade Parasitária , Plasmodium berghei/crescimento & desenvolvimento , Plasmodium falciparum/crescimento & desenvolvimento , Relação Estrutura-AtividadeRESUMO
Toxoplasma gondii, the most common parasitic infection of human brain and eye, persists across lifetimes, can progressively damage sight, and is currently incurable. New, curative medicines are needed urgently. Herein, we develop novel models to facilitate drug development: EGS strain T. gondii forms cysts in vitro that induce oocysts in cats, the gold standard criterion for cysts. These cysts highly express cytochrome b. Using these models, we envisioned, and then created, novel 4-(1H)-quinolone scaffolds that target the cytochrome bc1 complex Qi site, of which, a substituted 5,6,7,8-tetrahydroquinolin-4-one inhibits active infection (IC50, 30 nM) and cysts (IC50, 4 µM) in vitro, and in vivo (25 mg/kg), and drug resistant Plasmodium falciparum (IC50, <30 nM), with clinically relevant synergy. Mutant yeast and co-crystallographic studies demonstrate binding to the bc1 complex Qi site. Our results have direct impact on improving outcomes for those with toxoplasmosis, malaria, and ~2 billion persons chronically infected with encysted bradyzoites.
Assuntos
Descoberta de Drogas , Quinolonas/farmacologia , Toxoplasma/efeitos dos fármacos , Toxoplasmose/tratamento farmacológico , Animais , Gatos , Citocromos b/genética , Modelos Animais de Doenças , Resistência a Medicamentos/genética , Fezes/parasitologia , Humanos , Oocistos/efeitos dos fármacos , Oocistos/patogenicidade , Contagem de Ovos de Parasitas , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/patogenicidade , Toxoplasma/genética , Toxoplasma/patogenicidade , Toxoplasmose/genética , Toxoplasmose/parasitologiaRESUMO
A series of 3-piperidin-4-yl-1H-indoles with building block diversity was synthesized based on a hit derived from an HTS whole-cell screen against Plasmodium falciparum. Thirty-eight compounds were obtained following a three-step synthetic approach and evaluated for anti-parasitic activity. The SAR shows that 3-piperidin-4-yl-1H-indole is intolerant to most N-piperidinyl modifications. Nevertheless, we were able to identify a new compound (10d) with lead-like properties (MW = 305; cLogP = 2.42), showing antimalarial activity against drug-resistant and sensitive strains (EC50 values â¼ 3 µM), selectivity for malaria parasite and no cross-resistance with chloroquine, thus representing a potential new chemotype for further optimization towards novel and affordable antimalarial drugs.
Assuntos
Antimaláricos/química , Antimaláricos/farmacologia , Indóis/farmacologia , Malária/tratamento farmacológico , Niacinamida/análogos & derivados , Plasmodium falciparum/efeitos dos fármacos , Antimaláricos/síntese química , Antimaláricos/uso terapêutico , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Células Hep G2 , Humanos , Indóis/síntese química , Indóis/química , Malária/parasitologia , Estrutura Molecular , Niacinamida/síntese química , Niacinamida/química , Niacinamida/farmacologia , Testes de Sensibilidade Parasitária , Plasmodium falciparum/crescimento & desenvolvimento , Relação Estrutura-AtividadeRESUMO
Here, we describe medicinal chemistry that was accelerated by a diversity-oriented synthesis (DOS) pathway, and in vivo studies of our previously reported macrocyclic antimalarial agent that derived from the synthetic pathway. Structure-activity relationships that focused on both appendage and skeletal features yielded a nanomolar inhibitor of P. falciparum asexual blood-stage growth with improved solubility and microsomal stability and reduced hERG binding. The build/couple/pair (B/C/P) synthetic strategy, used in the preparation of the original screening library, facilitated medicinal chemistry optimization of the antimalarial lead.
Assuntos
Antimaláricos/química , Antimaláricos/farmacologia , Química Farmacêutica/métodos , Relação Estrutura-Atividade , Antimaláricos/metabolismo , Técnicas de Química Sintética , Canal de Potássio ERG1 , Canais de Potássio Éter-A-Go-Go/metabolismo , Lactamas Macrocíclicas/química , Lactamas Macrocíclicas/farmacologia , Plasmodium falciparum/efeitos dos fármacos , SolubilidadeRESUMO
Whole-cell high-throughput screening of the AstraZeneca compound library against the asexual blood stage of Plasmodium falciparum (Pf) led to the identification of amino imidazoles, a robust starting point for initiating a hit-to-lead medicinal chemistry effort. Structure-activity relationship studies followed by pharmacokinetics optimization resulted in the identification of 23 as an attractive lead with good oral bioavailability. Compound 23 was found to be efficacious (ED90 of 28.6 mg·kg(-1)) in the humanized P. falciparum mouse model of malaria (Pf/SCID model). Representative compounds displayed a moderate to fast killing profile that is comparable to that of chloroquine. This series demonstrates no cross-resistance against a panel of Pf strains with mutations to known antimalarial drugs, thereby suggesting a novel mechanism of action for this chemical class.
Assuntos
Antimaláricos/farmacologia , Benzimidazóis/uso terapêutico , Malária Falciparum/tratamento farmacológico , Plasmodium falciparum/efeitos dos fármacos , Animais , Antimaláricos/química , Benzimidazóis/farmacocinética , Benzimidazóis/farmacologia , Disponibilidade Biológica , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Ensaios de Triagem em Larga Escala , Humanos , Concentração Inibidora 50 , Camundongos , Bibliotecas de Moléculas Pequenas , Relação Estrutura-AtividadeRESUMO
Protecting the fetus and placenta from the maternal immune system has long been considered a function of placental trophoblasts. Here, we present two related lines of evidence that contradict this assumption. First, we show that transformed mouse trophoblast cell lines akin to human choriocarcinomas form tumors in syngeneic and immunodeficient mice, yet are rejected in immunocompetent allogeneic mice. Second, we show that wild-type trophoblasts are rapidly killed after i.v. injection into allogeneic mice. In both cases, the pattern of trophoblast killing in different strains of immunodeficient mice indicated that rejection involved host natural killer cells, and this was corroborated by in vitro killing assays. The apparent intrinsic susceptibility of mouse trophoblasts to immune attack strongly suggests that it is instead some property of the pregnant uterus that is of primary importance in preventing rejection of the fetus.