RESUMEN
Malaria, caused by Plasmodium falciparum, remains a significant health burden. A barrier for developing anti-malarial drugs is the ability of the parasite to rapidly generate resistance. We demonstrated that Salinipostin A (SalA), a natural product, kills parasites by inhibiting multiple lipid metabolizing serine hydrolases, a mechanism with a low propensity for resistance. Given the difficulty of employing natural products as therapeutic agents, we synthesized a library of lipidic mixed alkyl/aryl phosphonates as bioisosteres of SalA. Two constitutional isomers exhibited divergent anti-parasitic potencies which enabled identification of therapeutically relevant targets. We also confirm that this compound kills parasites through a mechanism that is distinct from both SalA and the pan-lipase inhibitor, Orlistat. Like SalA, our compound induces only weak resistance, attributable to mutations in a single protein involved in multidrug resistance. These data suggest that mixed alkyl/aryl phosphonates are a promising, synthetically tractable anti-malarials with a low-propensity to induce resistance.
RESUMEN
The Plasmodium proteasome is a promising antimalarial drug target due to its essential role in all parasite lifecycle stages. Furthermore, proteasome inhibitors have synergistic effects when combined with current first-line artemisinin and related analogues. Linear peptides that covalently inhibit the proteasome are effective at killing parasites and have a low propensity for inducing resistance. However, these scaffolds generally suffer from poor pharmacokinetics and bioavailability. Here we describe the development of covalent, irreversible, macrocyclic inhibitors of the Plasmodium falciparum proteasome. We identified compounds with excellent potency and low cytotoxicity; however, the first generation suffered from poor microsomal stability. Further optimization of an existing macrocyclic scaffold resulted in an irreversible covalent inhibitor carrying a vinyl sulfone electrophile that retained high potency and low cytotoxicity and had acceptable metabolic stability. Importantly, unlike the parent reversible inhibitor that selected for multiple mutations in the proteasome, with one resulting in a 5,000-fold loss of potency, the irreversible analogue only showed a 5-fold loss in potency for any single point mutation. Furthermore, an epoxyketone analogue of the same scaffold retained potency against a panel of known proteasome mutants. These results confirm that macrocycles are optimal scaffolds to target the malarial proteasome and that the use of a covalent electrophile can greatly reduce the ability of the parasite to generate drug resistance mutations.
RESUMEN
A series of novel thiazole-containing amides were synthesized. A structure-activity relationship study of these compounds led to the identification of potent and selective PfFPPS/GGPPS inhibitors with good in vitro ADME profiles. The most promising candidate molecules were progressed to mouse in vivo PK studies and demonstrated adequate free drug exposure to warrant further investigation.
Asunto(s)
Antimaláricos/farmacología , Difosfonatos/farmacología , Inhibidores Enzimáticos/farmacología , Farnesiltransferasa/antagonistas & inhibidores , Geraniltranstransferasa/antagonistas & inhibidores , Plasmodium falciparum/efectos de los fármacos , Antimaláricos/síntesis química , Antimaláricos/química , Difosfonatos/síntesis química , Difosfonatos/química , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/química , Farnesiltransferasa/metabolismo , Geraniltranstransferasa/metabolismo , Estructura Molecular , Pruebas de Sensibilidad Parasitaria , Plasmodium falciparum/enzimología , Relación Estructura-ActividadRESUMEN
This corrects the article DOI: 10.1038/ncomms14158.
RESUMEN
Human respiratory syncytial virus (RSV) is the main cause of lower respiratory tract infections in young children. The RSV fusion protein (F) is highly conserved and is the only viral membrane protein that is essential for infection. The prefusion conformation of RSV F is considered the most relevant target for antiviral strategies because it is the fusion-competent form of the protein and the primary target of neutralizing activity present in human serum. Here, we describe two llama-derived single-domain antibodies (VHHs) that have potent RSV-neutralizing activity and bind selectively to prefusion RSV F with picomolar affinity. Crystal structures of these VHHs in complex with prefusion F show that they recognize a conserved cavity formed by two F protomers. In addition, the VHHs prevent RSV replication and lung infiltration of inflammatory monocytes and T cells in RSV-challenged mice. These prefusion F-specific VHHs represent promising antiviral agents against RSV.
Asunto(s)
Anticuerpos Neutralizantes/inmunología , Infecciones por Virus Sincitial Respiratorio/inmunología , Virus Sincitial Respiratorio Humano/inmunología , Anticuerpos de Dominio Único/inmunología , Proteínas Virales de Fusión/inmunología , Animales , Camélidos del Nuevo Mundo/inmunología , Chlorocebus aethiops , Humanos , Ratones , Monocitos/inmunología , Monocitos/virología , Unión Proteica , Infecciones por Virus Sincitial Respiratorio/virología , Virus Sincitial Respiratorio Humano/fisiología , Linfocitos T/inmunología , Linfocitos T/virología , Células Vero , Replicación Viral/inmunologíaRESUMEN
Prevention efforts for respiratory syncytial virus (RSV) have been advanced due to the recent isolation and characterization of antibodies that specifically recognize the prefusion conformation of the RSV fusion (F) glycoprotein. These potently neutralizing antibodies are in clinical development for passive prophylaxis and have also aided the design of vaccine antigens that display prefusion-specific epitopes. To date, prefusion-specific antibodies have been shown to target two antigenic sites on RSV F, but both of these sites are also present on monomeric forms of F. Here we present a structural and functional characterization of human antibody AM14, which potently neutralized laboratory strains and clinical isolates of RSV from both A and B subtypes. The crystal structure and location of escape mutations revealed that AM14 recognizes a quaternary epitope that spans two protomers and includes a region that undergoes extensive conformational changes in the pre- to postfusion F transition. Binding assays demonstrated that AM14 is unique in its specific recognition of trimeric furin-cleaved prefusion F, which is the mature form of F on infectious virions. These results demonstrate that the prefusion F trimer contains potent neutralizing epitopes not present on monomers and that AM14 should be particularly useful for characterizing the conformational state of RSV F-based vaccine antigens.