RESUMO
Toxoplasma gondii and Neospora caninum are major worldwide morbidity-causing pathogens. Bumped kinase inhibitors (BKIs) are a compound class that has been optimized to target the apicomplexan calcium-dependent protein kinase 1 (CDPK1) - and several members of this class have proven to be safe and highly active in vitro and in vivo. BKI-1708 is based on a 5-aminopyrazole-4-carboxamide scaffold, and exhibited in vitro IC50 values of 120 nM for T. gondii and 480 nM for N. caninum ß-galactosidase expressing strains, and did not affect human foreskin fibroblast (HFF) viability at concentrations up to 25 µM. Electron microscopy established that exposure of tachyzoite-infected fibroblasts to 2.5 µM BKI-1708 in vitro induced the formation of multinucleated schizont-like complexes (MNCs), characterized by continued nuclear division and harboring newly formed intracellular zoites that lack the outer plasma membrane. These zoites were unable to finalize cytokinesis to form infective tachyzoites. BKI-1708 did not affect zebrafish (Danio rerio) embryo development during the first 96 h following egg hatching at concentrations up to 2 µM. Treatments of mice with BKI-1708 at 20 mg/kg/day during five consecutive days resulted in drug plasma levels ranging from 0.14 to 4.95 µM. In vivo efficacy of BKI-1708 was evaluated by oral application of 20 mg/kg/day from day 9-13 of pregnancy in mice experimentally infected with N. caninum (NcSpain-7) tachyzoites or T. gondii (TgShSp1) oocysts. This resulted in significantly decreased cerebral parasite loads and reduced vertical transmission in both models without drug-induced pregnancy interference.
Assuntos
Coccidiose , Fibroblastos , Neospora , Pirazóis , Toxoplasma , Animais , Neospora/efeitos dos fármacos , Toxoplasma/efeitos dos fármacos , Camundongos , Coccidiose/tratamento farmacológico , Coccidiose/parasitologia , Pirazóis/farmacologia , Feminino , Fibroblastos/efeitos dos fármacos , Fibroblastos/parasitologia , Humanos , Antiprotozoários/farmacologia , Concentração Inibidora 50 , Toxoplasmose/tratamento farmacológico , Toxoplasmose/parasitologia , Modelos Animais de Doenças , Inibidores de Proteínas Quinases/farmacologia , Proteínas QuinasesRESUMO
Cryptosporidium parvum is an apicomplexan parasite causing persistent diarrhea in humans and animals. Issuing from target-based drug development, calcium-dependent protein kinase 1 inhibitors, collectively named bumped kinase inhibitors (BKIs), with excellent efficacies in vitro and in vivo have been generated. Some BKIs including BKI-1748 share a core structure with similarities to the first-generation antiprotozoal drug quinine, which is known to exert notorious side effects. Unlike quinine, BKI-1748 rapidly interfered with C. parvum proliferation in the human colon tumor (HCT) cell line HCT-8 cells and caused dramatic effects on the parasite ultrastructure. To identify putative BKI targets in C. parvum and in host cells, we performed differential affinity chromatography with cell-free extracts from non-infected and infected HCT-8 cells using BKI-1748 and quinine epoxy-activated sepharose columns followed by mass spectrometry. C. parvum proteins of interest were identified in eluates from columns coupled to BKI-1748, or in eluates from both BKI-1748 and quinine columns. However, no C. parvum proteins could be identified binding exclusively to BKI-1748. In contrast, 25 BKI-1748-specific binding proteins originating from HCT-8 cells were detected. Moreover, 29 C. parvum and 224 host cell proteins were identified in both BKI-1748 as well as in quinine eluates. In both C. parvum and host cells, the largest subset of binding proteins was involved in RNA binding and modification, with a focus on ribosomal proteins and proteins involved in RNA splicing. These findings extend previous results, showing that BKI-1748 interacts with putative targets involved in common, essential pathways such as translation and RNA processing.
Assuntos
Antineoplásicos , Antiprotozoários , Criptosporidiose , Cryptosporidium parvum , Cryptosporidium , Animais , Humanos , Quinina/farmacologia , Antiprotozoários/farmacologia , Antineoplásicos/farmacologiaRESUMO
Each year, approximately 50,000 children under 5 die as a result of diarrhea caused by Cryptosporidium parvum, a protozoan parasite. There are currently no effective drugs or vaccines available to cure or prevent Cryptosporidium infection, and there are limited tools for identifying and validating targets for drug or vaccine development. We previously reported a high throughput screening (HTS) of a large compound library against Plasmodium N-myristoyltransferase (NMT), a validated drug target in multiple protozoan parasite species. To identify molecules that could be effective against Cryptosporidium, we counter-screened hits from the Plasmodium NMT HTS against Cryptosporidium NMT. We identified two potential hit compounds and validated them against CpNMT to determine if NMT might be an attractive drug target also for Cryptosporidium. We tested the compounds against Cryptosporidium using both cell-based and NMT enzymatic assays. We then determined the crystal structure of CpNMT bound to Myristoyl-Coenzyme A (MyrCoA) and structures of ternary complexes with MyrCoA and the hit compounds to identify the ligand binding modes. The binding site architectures display different conformational states in the presence of the two inhibitors and provide a basis for rational design of selective inhibitors.
Assuntos
Criptosporidiose , Cryptosporidium , Plasmodium , Criança , Humanos , Criptosporidiose/tratamento farmacológico , Desenvolvimento de MedicamentosRESUMO
Recent advances on the development of bumped kinase inhibitors for treatment of cryptosporidiosis have focused on the 5-aminopyrazole-4-carboxamide scaffold, due to analogs that have less hERG inhibition, superior efficacy, and strong in vitro safety profiles. Three compounds, BKI-1770, -1841, and -1708, showed strong efficacy in C. parvum infected mice. Both BKI-1770 and BKI-1841 had efficacy in the C. parvum newborn calf model, reducing diarrhea and oocyst excretion. However, both compounds caused hyperflexion of the limbs seen as dropped pasterns. Toxicity experiments in rats and calves dosed with BKI-1770 showed enlargement of the epiphyseal growth plate at doses only slightly higher than the efficacious dose. Mice were used as a screen to check for bone toxicity, by changes to the tibia epiphyseal growth plate, or neurological causes, by use of a locomotor activity box. These results showed neurological effects from both BKI-1770 and BKI-1841 and bone toxicity in mice from BKI-1770, indicating one or both effects may be contributing to toxicity. However, BKI-1708 remains a viable treatment candidate for further evaluation as it showed no signs of bone toxicity or neurological effects in mice.
Assuntos
Antineoplásicos , Antiprotozoários , Criptosporidiose , Cryptosporidium parvum , Animais , Bovinos , Camundongos , Ratos , Criptosporidiose/tratamento farmacológico , Antiprotozoários/farmacologia , Antineoplásicos/farmacologia , Inibidores de Proteínas Quinases/farmacologia , OocistosRESUMO
A phenotypic screen of the ReFRAME compound library was performed to identify cell-active inhibitors that could be developed as therapeutics for giardiasis. A primary screen against Giardia lamblia GS clone H7 identified 85 cell-active compounds at a hit rate of 0.72%. A cytotoxicity counterscreen against HEK293T cells was carried out to assess hit compound selectivity for further prioritization. Mavelertinib (PF-06747775), a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), was identified as a potential new therapeutic based on indication, activity, and availability after reconfirmation. Mavelertinib has in vitro efficacy against metronidazole-resistant 713-M3 strains. Other EGFR-TKIs screened in follow-up assays exhibited insignificant inhibition of G. lamblia at 5 µM, suggesting that the primary molecular target of mavelertinib may have a different mechanistic binding mode from human EGFR-tyrosine kinase. Mavelertinib, dosed as low as 5 mg/kg of body weight or as high as 50 mg/kg, was efficacious in the acute murine Giardia infection model. These results suggest that mavelertinib merits consideration for repurposing and advancement to giardiasis clinical trials while its analogues are further developed.
Assuntos
Giardia lamblia , Giardíase , Animais , Receptores ErbB , Giardíase/tratamento farmacológico , Células HEK293 , Humanos , Camundongos , Inibidores de Proteínas Quinases/farmacologia , Inibidores de Proteínas Quinases/uso terapêuticoRESUMO
The intestinal protozoan Cryptosporidium is a leading cause of diarrheal disease and mortality in young children. There is currently no fully effective treatment for cryptosporidiosis, which has stimulated interest in anticryptosporidial development over the last â¼10 years, with numerous lead compounds identified, including several tRNA synthetase inhibitors. Here, we report the results of a dairy calf efficacy trial of the methionyl-tRNA (Cryptosporidium parvum MetRS [CpMetRS]) synthetase inhibitor 2093 and the spontaneous emergence of drug resistance. Dairy calves experimentally infected with Cryptosporidium parvum initially improved with 2093 treatment, but parasite shedding resumed in two of three calves on treatment day 5. Parasites shed by each recrudescent calf had different amino acid-altering mutations in the gene encoding CpMetRS (CpMetRS), yielding either an aspartate 243-to-glutamate (D243E) or a threonine 246-to-isoleucine (T246I) mutation. Transgenic parasites engineered to have either the D243E or T246I CpMetRS mutation using CRISPR/Cas9 grew normally but were highly 2093 resistant; the D243E and T246I mutant-expressing parasites, respectively, had 2093 half-maximal effective concentrations (EC50s) that were 613- and 128-fold that of transgenic parasites with wild-type CpMetRS. In studies using recombinant enzymes, the D243E and T246I mutations shifted the 2093 IC50 >170-fold. Structural modeling of CpMetRS based on an inhibitor-bound Trypanosoma brucei MetRS crystal structure suggested that the resistance mutations reposition nearby hydrophobic residues, interfering with compound binding while minimally impacting substrate binding. This is the first report of naturally emerging Cryptosporidium drug resistance, highlighting the need to address the potential for anticryptosporidial resistance and establish strategies to limit its occurrence.
Assuntos
Doenças dos Bovinos , Criptosporidiose , Cryptosporidium parvum , Cryptosporidium , Animais , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Criança , Pré-Escolar , Criptosporidiose/tratamento farmacológico , Cryptosporidium/genética , Cryptosporidium parvum/genética , Resistência a Medicamentos/genética , Fezes , HumanosRESUMO
This is a review of the development of bumped-kinase inhibitors (BKIs) for the therapy of One Health parasitic apicomplexan diseases. Many apicomplexan infections are shared between humans and livestock, such as cryptosporidiosis and toxoplasmosis, as well as livestock only diseases such as neosporosis. We have demonstrated proof-of-concept for BKI therapy in livestock models of cryptosporidiosis (newborn calves infected with Cryptosporidium parvum), toxoplasmosis (pregnant sheep infected with Toxoplasma gondii), and neosporosis (pregnant sheep infected with Neospora caninum). We discuss the potential uses of BKIs for the treatment of diseases caused by apicomplexan parasites in animals and humans, and the improvements that need to be made to further develop BKIs.
Assuntos
Antiparasitários/farmacologia , Criptosporidiose/tratamento farmacológico , Saúde Única , Piperidinas/farmacologia , Pirimidinas/farmacologia , Quinolinas/farmacologia , Animais , Apicomplexa , HumanosRESUMO
Bumped kinase inhibitors (BKIs) are effective against a variety of apicomplexan parasites. Fifteen BKIs with promising in vitro efficacy against Neospora caninum tachyzoites, low cytotoxicity in mammalian cells, and no toxic effects in non-pregnant BALB/c mice were assessed in pregnant mice. Drugs were emulsified in corn oil and were applied by gavage for 5 days. Five BKIs did not affect pregnancy, five BKIs exhibited ~15-35% neonatal mortality and five compounds caused strong effects (infertility, abortion, stillbirth and pup mortality). Additionally, the impact of these compounds on zebrafish (Danio rerio) embryo development was assessed by exposing freshly fertilised eggs to 0.2-50 µM of BKIs and microscopic monitoring of embryo development in a blinded manner for 4 days. We propose an algorithm that includes quantification of malformations and embryo deaths, and established a scoring system that allows the calculation of an impact score (Si) indicating at which concentrations BKIs visibly affect zebrafish embryo development. Comparison of the two models showed that for nine compounds no clear correlation between Si and pregnancy outcome was observed. However, the three BKIs affecting zebrafish embryos only at high concentrations (≥40 µM) did not impair mouse pregnancy at all, and the three compounds that inhibited zebrafish embryo development already at 0.2 µM showed detrimental effects in the pregnancy model. Thus, the zebrafish embryo development test has limited predictive value to foresee pregnancy outcome in BKI-treated mice. We conclude that maternal health-related factors such as cardiovascular, pharmacokinetic and/or bioavailability properties also contribute to BKI-pregnancy effects.
Assuntos
Desenvolvimento Embrionário/efeitos dos fármacos , Naftalenos/toxicidade , Neospora/efeitos dos fármacos , Piperidinas/toxicidade , Pirazóis/toxicidade , Pirimidinas/toxicidade , Quinolinas/toxicidade , Toxoplasma/efeitos dos fármacos , Animais , Linhagem Celular , Coccidiose/tratamento farmacológico , Feminino , Células Hep G2 , Humanos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Naftalenos/farmacocinética , Naftalenos/farmacologia , Neospora/crescimento & desenvolvimento , Piperidinas/farmacocinética , Piperidinas/farmacologia , Gravidez , Complicações na Gravidez/induzido quimicamente , Proteínas Quinases/efeitos dos fármacos , Proteínas Quinases/metabolismo , Pirazóis/farmacocinética , Pirazóis/farmacologia , Pirimidinas/farmacocinética , Pirimidinas/farmacologia , Quinolinas/farmacocinética , Quinolinas/farmacologia , Toxoplasma/crescimento & desenvolvimento , Toxoplasmose/tratamento farmacológico , Peixe-Zebra/embriologiaRESUMO
Bumped Kinase Inhibitors, targeting Calcium-dependent Protein Kinase 1 in apicomplexan parasites with a glycine gatekeeper, are promising new therapeutics for apicomplexan diseases. Here we will review advances, as well as challenges and lessons learned regarding efficacy, safety, and pharmacology that have shaped our selection of pre-clinical candidates.
Assuntos
Apicomplexa/efeitos dos fármacos , Coccidiose/tratamento farmacológico , Inibidores de Proteínas Quinases , Animais , Apicomplexa/metabolismo , Criptosporidiose/tratamento farmacológico , Cryptosporidium/efeitos dos fármacos , Cryptosporidium/metabolismo , Humanos , Inibidores de Proteínas Quinases/efeitos adversos , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Proteínas Quinases/efeitos dos fármacos , Proteínas Quinases/metabolismo , Toxoplasma/efeitos dos fármacos , Toxoplasma/metabolismo , Toxoplasmose/tratamento farmacológicoRESUMO
BACKGROUND: Methionyl-tRNA synthetase (MetRS) inhibitors are under investigation for the treatment of intestinal infections caused by Giardia lamblia. OBJECTIVES: To properly analyse the therapeutic potential of the MetRS inhibitor 1717, experimental tools including a robust cell-based assay and a murine model of infection were developed based on novel strains of G. lamblia that employ luciferase reporter systems to quantify viable parasites. METHODS: Systematic screening of Giardia-specific promoters and luciferase variants led to the development of a strain expressing the click beetle green luciferase. Further modifying this strain to express NanoLuc created a dual reporter strain capable of quantifying parasites in both the trophozoite and cyst stages. These strains were used to develop a high-throughput cell assay and a mouse infection model. A library of MetRS inhibitors was screened in the cell assay and Compound-1717 was tested for efficacy in the mouse infection model. RESULTS: Cell viability in in vitro compound screens was quantified via bioluminescence readouts while infection loads in mice were monitored with non-invasive whole-animal imaging and faecal analysis. Compound-1717 was effective in clearing mice of Giardia infection in 3 days at varying doses, which was supported by data from enzymatic and phenotypic cell assays. CONCLUSIONS: The new in vitro and in vivo assays based on luciferase expression by engineered G. lamblia strains are useful for the discovery and development of new therapeutics for giardiasis. MetRS inhibitors, as validated by Compound-1717, have promising anti-giardiasis properties that merit further study as alternative therapeutics.
Assuntos
Giardia lamblia , Giardíase , Metionina tRNA Ligase , Animais , Giardíase/tratamento farmacológico , Ensaios de Triagem em Larga Escala , Luciferases/genética , CamundongosRESUMO
Neisseria gonorrhoeae (Ng) and Chlamydia trachomatis (Ct) are the most commonly reported sexually transmitted bacteria worldwide and usually present as co-infections. Increasing resistance of Ng to currently recommended dual therapy of azithromycin and ceftriaxone presents therapeutic challenges for syndromic management of Ng-Ct co-infections. Development of a safe, effective, and inexpensive dual therapy for Ng-Ct co-infections is an effective strategy for the global control and prevention of these two most prevalent bacterial sexually transmitted infections. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a validated drug target with two approved drugs for indications other than antibacterials. Nonetheless, any new drugs targeting GAPDH in Ng and Ct must be specific inhibitors of bacterial GAPDH that do not inhibit human GAPDH, and structural information of Ng and Ct GAPDH will aid in finding such selective inhibitors. Here, we report the X-ray crystal structures of Ng and Ct GAPDH. Analysis of the structures demonstrates significant differences in amino acid residues in the active sites of human GAPDH from those of the two bacterial enzymes suggesting design of compounds to selectively inhibit Ng and Ct is possible. We also describe an efficient in vitro assay of recombinant GAPDH enzyme activity amenable to high-throughput drug screening to aid in identifying inhibitory compounds and begin to address selectivity.
Assuntos
Chlamydia trachomatis/enzimologia , Gliceraldeído-3-Fosfato Desidrogenases/química , Neisseria gonorrhoeae/enzimologia , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Gliceraldeído-3-Fosfato Desidrogenases/antagonistas & inibidores , Gliceraldeído-3-Fosfato Desidrogenases/metabolismo , Humanos , Modelos Moleculares , Proteínas Recombinantes/metabolismo , Relação Estrutura-AtividadeRESUMO
Based on crystal structures of Trypanosoma brucei methionyl-tRNA synthetase (TbMetRS) bound to inhibitors, we designed, synthesized, and evaluated two series of novel TbMetRS inhibitors targeting this parasite enzyme. One series has a 1,3-dihydro-imidazol-2-one containing linker, the other has a rigid fused aromatic ring in the linker. For both series of compounds, potent inhibition of parasite growth was achieved with EC50 < 10 nM and most compounds exhibited low general toxicity to mammalian cells with CC50s > 20 000 nM. Selectivity over human mitochondrial methionyl tRNA synthetase was also evaluated, using a cell-based mitochondrial protein synthesis assay, and selectivity in a range of 20-200-fold was achieved. The inhibitors exhibited poor permeability across the blood brain barrier, necessitating future efforts to optimize the compounds for use in late stage human African trypanosomiasis.
RESUMO
Cryptosporidium is a leading cause of pediatric diarrhea worldwide. Currently, there is neither a vaccine nor a consistently effective drug available for this disease. Selective 5-aminopyrazole-4-carboxamide-based bumped-kinase inhibitors (BKIs) are effective in both in vitro and in vivo models of Cryptosporidium parvum. Potential cardiotoxicity in some BKIs led to the continued exploration of the 5-aminopyrazole-4-carboxamide scaffold to find safe and effective drug candidates for Cryptosporidium. A series of newly designed BKIs were tested for efficacy against C. parvum using in vitro and in vivo (mouse infection model) assays and safety issues. Compound 6 (BKI 1708) was found to be efficacious at 8 mg/kg dosed once daily (QD) for 5 days with no observable signs of toxicity up to 200 mg/kg dosed QD for 7 days. Compound 15 (BKI 1770) was found to be efficacious at 30 mg/kg dosed twice daily (BID) for 5 days with no observable signs of toxicity up to 300 mg/kg dosed QD for 7 days. Compounds 6 and 15 are promising preclinical leads for cryptosporidiosis therapy with acceptable safety parameters and efficacy in the mouse model of cryptosporidiosis.
Assuntos
Antiprotozoários/uso terapêutico , Ácidos Carboxílicos/química , Criptosporidiose/tratamento farmacológico , Pirazóis/farmacologia , Animais , Antiprotozoários/farmacocinética , Linhagem Celular , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Desenvolvimento de Medicamentos , Humanos , Interferon gama/genética , Camundongos , Camundongos Knockout , Pirazóis/química , Pirazóis/farmacocinéticaRESUMO
Activation of disulfides with N-halogen succinimide in the presence of TEMPO allows insertion reaction by an isocyanide, the product of which can further accept a wide range of nucleophiles for the generation of isothioureas and related molecular moieties. This new procedure overcomes previous methods that accept essentially only aryl amines as the third nucleophilic component. The diverse nucleophiles usable in our new protocol make this approach a general method for de novo synthesis of many S-containing heterocycles.
RESUMO
Cryptosporidiosis is one of the leading causes of moderate to severe diarrhea in children in low-resource settings. The therapeutic options for cryptosporidiosis are limited to one drug, nitazoxanide, which unfortunately has poor activity in the most needy populations of malnourished children and HIV-infected persons. We describe here the discovery and early optimization of a class of imidazopyridine-containing compounds with potential for treating Cryptosporidium infections. The compounds target the Cryptosporidium methionyl-tRNA synthetase (MetRS), an enzyme that is essential for protein synthesis. The most potent compounds inhibited the enzyme with Ki values in the low picomolar range. Cryptosporidium cells in culture were potently inhibited with 50% effective concentrations as low as 7 nM and >1,000-fold selectivity over mammalian cells. A parasite persistence assay indicates that the compounds act by a parasiticidal mechanism. Several compounds were demonstrated to control infection in two murine models of cryptosporidiosis without evidence of toxicity. Pharmacological and physicochemical characteristics of compounds were investigated to determine properties that were associated with higher efficacy. The results indicate that MetRS inhibitors are excellent candidates for development for anticryptosporidiosis therapy.
Assuntos
Antiprotozoários/farmacologia , Criptosporidiose/tratamento farmacológico , Cryptosporidium parvum/efeitos dos fármacos , Imidazóis/farmacologia , Metionina tRNA Ligase/antagonistas & inibidores , Piridinas/farmacologia , Animais , Cryptosporidium parvum/genética , Ciclo-Oxigenase 1/efeitos dos fármacos , Modelos Animais de Doenças , Descoberta de Drogas/métodos , Feminino , Células Hep G2 , Humanos , Imidazóis/química , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Piridinas/químicaRESUMO
Bumped kinase inhibitors (BKIs) have been shown to be potent inhibitors of Toxoplasma gondii calcium-dependent protein kinase 1. Pyrazolopyrimidine and 5-aminopyrazole-4-carboxamide scaffold-based BKIs are effective in acute and chronic experimental models of toxoplasmosis. Through further exploration of these 2 scaffolds and a new pyrrolopyrimidine scaffold, additional compounds have been identified that are extremely effective against acute experimental toxoplasmosis. The in vivo efficacy of these BKIs demonstrates that the cyclopropyloxynaphthyl, cyclopropyloxyquinoline, and 2-ethoxyquinolin-6-yl substituents are associated with efficacy across scaffolds. In addition, a broad range of plasma concentrations after oral dosing resulted from small structural changes to the BKIs. These select BKIs include anti-Toxoplasma compounds that are effective against acute experimental toxoplasmosis and are not toxic in human cell assays, nor to mice when administered for therapy. The BKIs described here are promising late leads for improving anti-Toxoplasma therapy.
Assuntos
Inibidores de Proteínas Quinases/uso terapêutico , Proteínas de Protozoários/antagonistas & inibidores , Pirazóis/uso terapêutico , Pirimidinas/uso terapêutico , Toxoplasmose Animal/tratamento farmacológico , Toxoplasmose Cerebral/tratamento farmacológico , Administração Oral , Animais , Área Sob a Curva , Feminino , Técnicas In Vitro , Camundongos , Inibidores de Proteínas Quinases/sangue , Inibidores de Proteínas Quinases/farmacologia , Pirazóis/sangue , Pirazóis/farmacologia , Pirimidinas/sangue , Pirimidinas/farmacologiaRESUMO
Mycobacterium tuberculosis is a pathogenic bacterial infectious agent that is responsible for approximately 1.5 million human deaths annually. Current treatment requires the long-term administration of multiple medicines with substantial side effects. Lack of compliance, together with other factors, has resulted in a worrisome increase in resistance. New treatment options are therefore urgently needed. Here, the crystal structure of methionyl-tRNA synthetase (MetRS), an enzyme critical for protein biosynthesis and therefore a drug target, in complex with its catalytic intermediate methionyl adenylate is reported. Phenylalanine 292 of the M. tuberculosis enzyme is in an `out' conformation and barely contacts the adenine ring, in contrast to other MetRS structures where ring stacking occurs between the adenine and a protein side-chain ring in the `in' conformation. A comparison with human cytosolic MetRS reveals substantial differences in the active site as well as regarding the position of the connective peptide subdomain 1 (CP1) near the active site, which bodes well for arriving at selective inhibitors. Comparison with the human mitochondrial enzyme at the amino-acid sequence level suggests that arriving at inhibitors with higher affinity for the mycobacterial enzyme than for the mitochondrial enzyme might be achievable.
Assuntos
Desenho de Fármacos , Metionina tRNA Ligase/química , Metionina tRNA Ligase/metabolismo , Mycobacterium tuberculosis/enzimologia , Catálise , Domínio Catalítico , Cristalização , Cristalografia por Raios X , Modelos Moleculares , Ligação Proteica , Conformação ProteicaRESUMO
An inexpensive, in-house made microdialysis device is described that is suitable for measuring the binding of small molecules including drug candidates to serum proteins or other macromolecules. The device is based on the standard equilibrium dialysis method to measure the fraction of low molecular weight compound bound to proteins. It is constructed from a standard polypropylene 96-well plate, dialysis tubing, and low viscosity epoxy resin. The device can be readily prepared for a small fraction of the cost of a commercial, multichamber microdialysis device. Drug-protein binding results are provided, which validates the device.
RESUMO
Selective inhibitors of Cryptosporidium calcium-dependent protein kinase 1 ( CpCDPK1) based on the 1 H-pyrazolo[3,4- d]pyrimidin-4-amine (pyrazolopyrimidine, PP) scaffold are effective in both in vitro and in vivo models of cryptosporidiosis. However, the search for distinct safety and pharmacokinetic (PK) properties has motivated our exploration of alternative scaffolds. Here, we describe a series of 7 H-pyrrolo[2,3- d]pyrimidin-4-amine (pyrrolopyrimidine, PrP)-based analogs of PP CpCDPK1 inhibitors. Most of the PrP-based inhibitors described potently inhibit the CpCDPK1 enzyme, demonstrate no toxicity against mammalian cells, and block proliferation of the C. parvum parasite in the low micromolar range. Interestingly, certain substituents that show reduced CpCDPK1 potency when displayed from a PP scaffold provided notably enhanced efficacy in the context of a PrP scaffold. PK studies on these paired compounds show that some PrP analogs have distinct physiochemical properties compared with their PP counterparts. These results demonstrate that inhibitors based on a PrP scaffold are distinct therapeutic alternatives to previously developed PP inhibitors.
Assuntos
Antiprotozoários/farmacologia , Cryptosporidium parvum/enzimologia , Inibidores Enzimáticos/farmacologia , Proteínas Quinases/metabolismo , Pirimidinas/farmacologia , Pirróis/farmacologia , Animais , Antiprotozoários/síntese química , Antiprotozoários/farmacocinética , Antiprotozoários/toxicidade , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Cryptosporidium parvum/efeitos dos fármacos , Cryptosporidium parvum/crescimento & desenvolvimento , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/farmacocinética , Inibidores Enzimáticos/toxicidade , Humanos , Concentração Inibidora 50 , Camundongos Endogâmicos BALB C , Estrutura Molecular , Pirimidinas/síntese química , Pirimidinas/farmacocinética , Pirimidinas/toxicidade , Pirróis/síntese química , Pirróis/farmacocinética , Pirróis/toxicidade , Relação Estrutura-AtividadeRESUMO
Direct reaction of isocyanides with some sulfenic-acid-generating sulfoxides led to the effective formation of the corresponding thiocarbamic acid S-esters in good to high yields. A multicomponent reaction involving isocyanide, sulfoxide, and a suitable nucleophile has also been developed, providing ready access to a diverse range of sulfur-containing compounds, including isothioureas, carbonimidothioic acid esters, and carboximidothioic acid esters.