RESUMO
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.
Assuntos
Antimaláricos/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Malária/parasitologia , Plasmodium/efeitos dos fármacos , Plasmodium/metabolismo , Biossíntese de Proteínas/efeitos dos fármacos , Quinolinas/farmacologia , Animais , Antimaláricos/administração & dosagem , Antimaláricos/efeitos adversos , Antimaláricos/farmacocinética , Descoberta de Drogas , Feminino , Estágios do Ciclo de Vida/efeitos dos fármacos , Fígado/efeitos dos fármacos , Fígado/parasitologia , Malária/tratamento farmacológico , Masculino , Modelos Moleculares , Fator 2 de Elongação de Peptídeos/antagonistas & inibidores , Fator 2 de Elongação de Peptídeos/metabolismo , Plasmodium/genética , Plasmodium/crescimento & desenvolvimento , Plasmodium berghei/efeitos dos fármacos , Plasmodium berghei/fisiologia , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/metabolismo , Plasmodium vivax/efeitos dos fármacos , Plasmodium vivax/metabolismo , Quinolinas/administração & dosagem , Quinolinas/química , Quinolinas/farmacocinéticaRESUMO
BACKGROUND: Protein kinases have been shown to be key drug targets, especially in the area of oncology. It is of interest to explore the possibilities of protein kinases as a potential target class in Plasmodium spp., the causative agents of malaria. However, protein kinase biology in malaria is still being investigated. Therefore, rather than assaying against individual protein kinases, a library of 4731 compounds with protein kinase inhibitor-like scaffolds was screened against the causative parasite, Plasmodium falciparum. This approach is more holistic and considers the whole kinome, making it possible to identify compounds that inhibit more than one P. falciparum protein kinase, or indeed other malaria targets. RESULTS: As a result of this screen, 9 active compound series were identified; further validation was carried out on 4 of these series, with 3 being progressed into hits to lead chemistry. The detailed evaluation of one of these series is described. DISCUSSION: This screening approach proved to be an effective way to identify series for further optimisation against malaria. Compound optimisation was carried out in the absence of knowledge of the molecular target. Some of the series had to be halted for various reasons. Mode of action studies to find the molecular target may be useful when problems prevent further chemical optimisation. CONCLUSIONS: Progressible series were identified through phenotypic screening of a relatively small focused kinase scaffold chemical library.
Assuntos
Antimaláricos/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Avaliação Pré-Clínica de MedicamentosRESUMO
African sleeping sickness or human African trypanosomiasis, caused by Trypanosoma brucei spp., is responsible for approximately 30,000 deaths each year. Available treatments for this disease are poor, with unacceptable efficacy and safety profiles, particularly in the late stage of the disease when the parasite has infected the central nervous system. Here we report the validation of a molecular target and the discovery of associated lead compounds with the potential to address this lack of suitable treatments. Inhibition of this target-T. brucei N-myristoyltransferase-leads to rapid killing of trypanosomes both in vitro and in vivo and cures trypanosomiasis in mice. These high-affinity inhibitors bind into the peptide substrate pocket of the enzyme and inhibit protein N-myristoylation in trypanosomes. The compounds identified have promising pharmaceutical properties and represent an opportunity to develop oral drugs to treat this devastating disease. Our studies validate T. brucei N-myristoyltransferase as a promising therapeutic target for human African trypanosomiasis.
Assuntos
Aciltransferases/antagonistas & inibidores , Antiparasitários/farmacologia , Antiparasitários/uso terapêutico , Trypanosoma brucei brucei/efeitos dos fármacos , Trypanosoma brucei brucei/enzimologia , Tripanossomíase Africana/tratamento farmacológico , Tripanossomíase Africana/parasitologia , Aciltransferases/metabolismo , Aminopiridinas/química , Aminopiridinas/metabolismo , Aminopiridinas/farmacologia , Aminopiridinas/uso terapêutico , Animais , Antiparasitários/química , Antiparasitários/metabolismo , Ensaios Enzimáticos , Inibidores Enzimáticos/química , Inibidores Enzimáticos/metabolismo , Inibidores Enzimáticos/farmacologia , Inibidores Enzimáticos/uso terapêutico , Feminino , Humanos , Camundongos , Estrutura Molecular , Pirazóis/química , Pirazóis/metabolismo , Pirazóis/farmacologia , Pirazóis/uso terapêutico , Ratos , Sulfonamidas/química , Sulfonamidas/metabolismo , Sulfonamidas/farmacologia , Sulfonamidas/uso terapêutico , Fatores de Tempo , Trypanosoma brucei brucei/crescimento & desenvolvimentoRESUMO
Visceral leishmaniasis is a neglected tropical disease with significant health impact. The current treatments are poor, and there is an urgent need to develop new drugs. Primary screening assays used for drug discovery campaigns have typically used free-living forms of the Leishmania parasite to allow for high-throughput screening. Such screens do not necessarily reflect the physiological situation, as the disease-causing stage of the parasite resides inside human host cells. Assessing the drug sensitivity of intracellular parasites on scale has recently become feasible with the advent of high-content screening methods. We describe here a 384-well microscopy-based intramacrophage Leishmania donovani assay and compare it to an axenic amastigote system. A panel of eight reference compounds was tested in both systems, as well as a human counterscreen cell line, and our findings show that for most clinically used compounds both axenic and intramacrophage assays report very similar results. A set of 15,659 diverse compounds was also screened using both systems. This resulted in the identification of seven new antileishmanial compounds and revealed a high false-positive rate for the axenic assay. We conclude that the intramacrophage assay is more suited as a primary hit-discovery platform than the current form of axenic assay, and we discuss how modifications to the axenic assay may render it more suitable for hit-discovery.
Assuntos
Antiprotozoários/farmacologia , Leishmania donovani/efeitos dos fármacos , Leishmaniose Visceral/tratamento farmacológico , Testes de Sensibilidade Parasitária , Cultura Axênica , Linhagem Celular , Descoberta de Drogas , Ensaios de Triagem em Larga Escala , Humanos , Macrófagos/parasitologiaRESUMO
While treatment options for human African trypanosomiasis (HAT) have improved significantly, there is still a need for new drugs with eradication now a realistic possibility. Here, we report the development of 2,4-diaminothiazoles that demonstrate significant potency against Trypanosoma brucei, the causative agent of HAT. Using phenotypic screening to guide structure-activity relationships, potent drug-like inhibitors were developed. Proof of concept was established in an animal model of the hemolymphatic stage of HAT. To treat the meningoencephalitic stage of infection, compounds were optimized for pharmacokinetic properties, including blood-brain barrier penetration. However, in vivo efficacy was not achieved, in part due to compounds evolving from a cytocidal to a cytostatic mechanism of action. Subsequent studies identified a nonessential kinase involved in the inositol biosynthesis pathway as the molecular target of these cytostatic compounds. These studies highlight the need for cytocidal drugs for the treatment of HAT and the importance of static-cidal screening of analogues.
Assuntos
Citostáticos , Tripanossomicidas , Trypanosoma brucei brucei , Tripanossomíase Africana , Animais , Humanos , Tripanossomíase Africana/tratamento farmacológico , Tripanossomicidas/uso terapêutico , Tripanossomicidas/farmacocinética , Citostáticos/uso terapêutico , Barreira HematoencefálicaRESUMO
Quinols have been developed as a class of potential anti-cancer compounds. They are thought to act as double Michael acceptors, forming two covalent bonds to their target protein(s). Quinols have also been shown to have activity against the parasite Trypanosoma brucei, the causative organism of human African trypanosomiasis, but they demonstrated little selectivity over mammalian MRC5 cells in a counter-screen. In this paper, we report screening of further examples of quinols against T. brucei. We were able to derive an SAR, but the compounds demonstrated little selectivity over MRC5 cells. In an approach to increase selectivity, we attached melamine and benzamidine motifs to the quinols, because these moieties are known to be selectively concentrated in the parasite by transporter proteins. In general these transporter motif-containing analogues showed increased selectivity; however they also showed reduced levels of potency against T. brucei.
Assuntos
Sistemas de Liberação de Medicamentos , Hidroquinonas/farmacologia , Tripanossomicidas/farmacologia , Trypanosoma brucei brucei/efeitos dos fármacos , Benzamidinas/síntese química , Benzamidinas/química , Benzamidinas/farmacologia , Linhagem Celular , Humanos , Hidroquinonas/síntese química , Hidroquinonas/química , Concentração Inibidora 50 , Modelos Moleculares , Estrutura Molecular , Triazinas/síntese química , Triazinas/química , Triazinas/farmacologia , Tripanossomicidas/síntese química , Tripanossomicidas/químicaRESUMO
The propensity of human embryonic stem cells to die upon enzymatic disaggregation or low-density plating is an obstacle to their isolation and routine use in drug discovery and basic research. Equally, the very low rate of establishment of implanted cells hinders cell therapy. In the present study we have developed a high-content assay for human embryonic stem cell survival and used this to screen a range of libraries of 'lead-like' small molecules and known bioactives. From this we identified 18 confirmed hits with four structural classes being represented by multiple compounds: a series of 5-(acyl/alkyl-amino)indazoles, compounds with a 4-(acylamino)pyridine core, simple N6,N6-dialkyladenines and compounds with a 5-(acylamino)indolinone core. In vitro kinase profiling indicated that the ROCK (Rho-associated kinase)/PRK2 (protein kinase C-related kinase 2) protein kinases are of pivotal importance for cell survival and identified previously unreported compound classes that inhibited this important biological activity. An evaluation using an extensive panel of protein kinases showed that six of our hit compounds exhibited better selectivity for ROCK inhibition than the routinely used commercially available ROCK inhibitor Y-27632. In this screen we also identified the K(+)-ATP channel opener pinacidil and show that it probably promotes cell survival, by 'off-target' inhibition of ROCK/PRK2. We have therefore identified novel pro-survival compounds of greater specificity, equivalent potency and reduced toxicity relative to the routinely employed ROCK inhibitor Y-27632.
Assuntos
Proliferação de Células/efeitos dos fármacos , Células-Tronco Embrionárias/efeitos dos fármacos , Compostos Heterocíclicos/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Amidas/farmacologia , Técnicas de Cultura de Células , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos/métodos , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Compostos Heterocíclicos/química , Humanos , Indazóis/química , Indazóis/farmacologia , Estrutura Molecular , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C/metabolismo , Inibidores de Proteínas Quinases/química , Piridinas/química , Piridinas/farmacologia , Fatores de Tempo , Quinases Associadas a rho/antagonistas & inibidores , Quinases Associadas a rho/metabolismoRESUMO
In the search for new therapeutics for the treatment of human African trypanosomiasis, many potential drug targets in Trypanosoma brucei have been validated by genetic means, but very few have been chemically validated. Trypanothione synthetase (TryS; EC 6.3.1.9; spermidine/glutathionylspermidine:glutathione ligase (ADP-forming)) is one such target. To identify novel inhibitors of T. brucei TryS, we developed an in vitro enzyme assay, which was amenable to high throughput screening. The subsequent screen of a diverse compound library resulted in the identification of three novel series of TryS inhibitors. Further chemical exploration resulted in leads with nanomolar potency, which displayed mixed, uncompetitive, and allosteric-type inhibition with respect to spermidine, ATP, and glutathione, respectively. Representatives of all three series inhibited growth of bloodstream T. brucei in vitro. Exposure to one of our lead compounds (DDD86243; 2 x EC(50) for 72 h) decreased intracellular trypanothione levels to <10% of wild type. In addition, there was a corresponding 5-fold increase in the precursor metabolite, glutathione, providing strong evidence that DDD86243 was acting on target to inhibit TryS. This was confirmed with wild-type, TryS single knock-out, and TryS-overexpressing cell lines showing expected changes in potency to DDD86243. Taken together, these data provide initial chemical validation of TryS as a drug target in T. brucei.
Assuntos
Amida Sintases/antagonistas & inibidores , Antiprotozoários/farmacocinética , Inibidores Enzimáticos/farmacologia , Proteínas de Protozoários/antagonistas & inibidores , Trypanosoma brucei brucei/enzimologia , Tripanossomíase Africana/tratamento farmacológico , Tripanossomíase Africana/enzimologia , Regulação Alostérica/efeitos dos fármacos , Regulação Alostérica/genética , Amida Sintases/genética , Amida Sintases/metabolismo , Animais , Antiprotozoários/química , Antiprotozoários/uso terapêutico , Avaliação Pré-Clínica de Medicamentos , Inibidores Enzimáticos/química , Inibidores Enzimáticos/uso terapêutico , Humanos , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/crescimento & desenvolvimentoRESUMO
Activity of the pterin- and folate-salvaging enzymes pteridine reductase 1 (PTR1) and dihydrofolate reductase-thymidylate synthetase (DHFR-TS) is commonly measured as a decrease in absorbance at 340 nm, corresponding to oxidation of nicotinamide adenine dinucleotide phosphate (NADPH). Although this assay has been adequate to study the biology of these enzymes, it is not amenable to support any degree of routine inhibitor assessment because its restricted linearity is incompatible with enhanced throughput microtiter plate screening. In this article, we report the development and validation of a nonenzymatically coupled screening assay in which the product of the enzymatic reaction reduces cytochrome c, causing an increase in absorbance at 550 nm. We demonstrate this assay to be robust and accurate, and we describe its utility in supporting a structure-based design, small-molecule inhibitor campaign against Trypanosoma brucei PTR1 and DHFR-TS.
Assuntos
Colorimetria/métodos , Citocromos c/metabolismo , Oxirredutases/metabolismo , Tetra-Hidrofolato Desidrogenase/metabolismo , Domínio Catalítico , Cristalografia por Raios X , Cinética , Metotrexato/farmacologia , NADP/metabolismo , Oxirredução , Trypanosoma brucei brucei/enzimologiaRESUMO
Chitin is an essential structural component of the fungal cell wall. Chitinases are thought to be important for fungal cell wall remodelling, and inhibition of these enzymes has been proposed as a potential strategy for development of novel anti-fungals. The fungal pathogen Aspergillus fumigatus possesses two distinct multi-gene chitinase families. Here we explore acetazolamide as a chemical scaffold for the inhibition of an A. fumigatus 'plant-type' chitinase. A co-crystal structure of AfChiA1 with acetazolamide was used to guide synthesis and screening of acetazolamide analogues that yielded SAR in agreement with these structural data. Although acetazolamide and its analogues are weak inhibitors of the enzyme, they have a high ligand efficiency and as such are interesting leads for future inhibitor development.
Assuntos
Acetazolamida/química , Antifúngicos/química , Quitinases/antagonistas & inibidores , Inibidores Enzimáticos/química , Proteínas Fúngicas/antagonistas & inibidores , Acetazolamida/síntese química , Acetazolamida/farmacologia , Sequência de Aminoácidos , Antifúngicos/síntese química , Antifúngicos/farmacologia , Aspergillus fumigatus/enzimologia , Sítios de Ligação , Quitinases/metabolismo , Cristalografia por Raios X , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/farmacologia , Proteínas Fúngicas/metabolismo , Dados de Sequência Molecular , Alinhamento de Sequência , Relação Estrutura-AtividadeRESUMO
Herein we describe the optimization of a phenotypic hit against Plasmodium falciparum based on an aminoacetamide scaffold. This led to N-(3-chloro-4-fluorophenyl)-2-methyl-2-{[4-methyl-3-(morpholinosulfonyl)phenyl]amino}propanamide (compound 28) with low-nanomolar activity against the intraerythrocytic stages of the malaria parasite, and which was found to be inactive in a mammalian cell counter-screen up to 25â µm. Inhibition of gametes in the dual gamete activation assay suggests that this family of compounds may also have transmission blocking capabilities. Whilst we were unable to optimize the aqueous solubility and microsomal stability to a point at which the aminoacetamides would be suitable for inâ vivo pharmacokinetic and efficacy studies, compound 28 displayed excellent antimalarial potency and selectivity; it could therefore serve as a suitable chemical tool for drug target identification.
Assuntos
Acetamidas/farmacologia , Antimaláricos/farmacologia , Acetamidas/síntese química , Acetamidas/farmacocinética , Animais , Antimaláricos/síntese química , Antimaláricos/farmacocinética , Humanos , Camundongos , Microssomos Hepáticos/metabolismo , Estrutura Molecular , Testes de Sensibilidade Parasitária , Plasmodium berghei/efeitos dos fármacos , Plasmodium cynomolgi/efeitos dos fármacos , Plasmodium falciparum/efeitos dos fármacos , Relação Estrutura-AtividadeRESUMO
Crystallography has guided the hybridization of two series of Trypanosoma brucei N-myristoyltransferase (NMT) inhibitors, leading to a novel highly selective series. The effect of combining the selectivity enhancing elements from two pharmacophores is shown to be additive and has led to compounds that have greater than 1000-fold selectivity for TbNMT vs HsNMT. Further optimization of the hybrid series has identified compounds with significant trypanocidal activity capable of crossing the blood-brain barrier. By using CF-1 mdr1a deficient mice, we were able to demonstrate full cures in vivo in a mouse model of stage 2 African sleeping sickness. This and previous work provides very strong validation for NMT as a drug target for human African trypanosomiasis in both the peripheral and central nervous system stages of disease.
Assuntos
Aciltransferases/antagonistas & inibidores , Barreira Hematoencefálica/efeitos dos fármacos , Desenho de Fármacos , Tripanossomicidas/química , Tripanossomicidas/farmacologia , Trypanosoma brucei brucei/efeitos dos fármacos , Tripanossomíase Africana/tratamento farmacológico , Animais , Sobrevivência Celular , Feminino , Humanos , Camundongos , Camundongos Endogâmicos , Modelos Moleculares , Estrutura Molecular , Conformação Proteica , Relação Estrutura-Atividade , Tripanossomíase Africana/microbiologiaRESUMO
Drug discovery is a high-risk, expensive and lengthy process taking at least 12 years and costing upwards of US$500 million per drug to reach the clinic. For neglected diseases, the drug discovery process is driven by medical need and guided by pre-defined target product profiles. Assessment and prioritisation of the most promising targets for entry into screening programmes is crucial for maximising the chances of success. Here, we describe criteria used in our drug discovery unit for target assessment and introduce the 'traffic-light' system as a prioritisation and management tool. We hope this brief review will stimulate basic scientists to acquire additional information necessary for drug discovery.
Assuntos
Antiparasitários/farmacologia , Desenho de Fármacos , Indústria Farmacêutica/economia , Parasitos/efeitos dos fármacos , Doenças Parasitárias/tratamento farmacológico , Animais , Química Farmacêutica , Avaliação Pré-Clínica de Medicamentos/economia , Avaliação Pré-Clínica de Medicamentos/métodos , Humanos , Testes de Sensibilidade Parasitária , Farmacogenética , Projetos de Pesquisa , Resultado do TratamentoRESUMO
In late mitosis and G1, origins of DNA replication must be "licensed" for use in the upcoming S phase by being encircled by double hexamers of the minichromosome maintenance proteins MCM2-7. A "licensing checkpoint" delays cells in G1 until sufficient origins have been licensed, but this checkpoint is lost in cancer cells. Inhibition of licensing can therefore kill cancer cells while only delaying normal cells in G1. In a high-throughput cell-based screen for licensing inhibitors we identified a family of 2-arylquinolin-4-amines, the most potent of which we call RL5a. The binding of the origin recognition complex (ORC) to origin DNA is the first step of the licensing reaction. We show that RL5a prevents ORC forming a tight complex with DNA that is required for MCM2-7 loading. Formation of this ORC-DNA complex requires ATP, and we show that RL5a inhibits ORC allosterically to mimic a lack of ATP.
Assuntos
Aminas/farmacologia , Replicação do DNA/efeitos dos fármacos , DNA/metabolismo , Complexo de Reconhecimento de Origem/metabolismo , Trifosfato de Adenosina/metabolismo , Regulação Alostérica , Aminas/química , Aminas/metabolismo , Animais , Proteínas de Ciclo Celular/antagonistas & inibidores , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Cromatina/química , Cromatina/metabolismo , Humanos , Proteínas de Manutenção de Minicromossomo/química , Proteínas de Manutenção de Minicromossomo/metabolismo , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Complexo de Reconhecimento de Origem/antagonistas & inibidores , Quinolinas/farmacologia , Origem de Replicação/genética , Tiazóis/farmacologia , Xenopus , Proteínas de Xenopus/metabolismoRESUMO
N-Myristoyltransferase (NMT) represents a promising drug target within the parasitic protozoa Trypanosoma brucei (T. brucei), the causative agent for human African trypanosomiasis (HAT) or sleeping sickness. We have previously validated T. brucei NMT as a promising druggable target for the treatment of HAT in both stages 1 and 2 of the disease. We report on the use of the previously reported DDD85646 (1) as a starting point for the design of a class of potent, brain penetrant inhibitors of T. brucei NMT.
Assuntos
Aciltransferases/antagonistas & inibidores , Aminopiridinas/química , Aminopiridinas/farmacologia , Sulfonamidas/química , Sulfonamidas/farmacologia , Tripanossomicidas/química , Tripanossomicidas/farmacologia , Trypanosoma brucei brucei/efeitos dos fármacos , Trypanosoma brucei brucei/enzimologia , Tripanossomíase Africana/tratamento farmacológico , Aciltransferases/metabolismo , Aminopiridinas/síntese química , Aminopiridinas/farmacocinética , Animais , Encéfalo/metabolismo , Cristalografia por Raios X , Desenho de Fármacos , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacocinética , Inibidores Enzimáticos/farmacologia , Humanos , Camundongos , Sulfonamidas/síntese química , Sulfonamidas/farmacocinética , Tripanossomicidas/síntese química , Tripanossomicidas/farmacocinética , Tripanossomíase Africana/metabolismoRESUMO
The antiplasmodial activity, DMPK properties, and efficacy of a series of quinoline-4-carboxamides are described. This series was identified from a phenotypic screen against the blood stage of Plasmodium falciparum (3D7) and displayed moderate potency but with suboptimal physicochemical properties and poor microsomal stability. The screening hit (1, EC50 = 120 nM) was optimized to lead molecules with low nanomolar in vitro potency. Improvement of the pharmacokinetic profile led to several compounds showing excellent oral efficacy in the P. berghei malaria mouse model with ED90 values below 1 mg/kg when dosed orally for 4 days. The favorable potency, selectivity, DMPK properties, and efficacy coupled with a novel mechanism of action, inhibition of translation elongation factor 2 (PfEF2), led to progression of 2 (DDD107498) to preclinical development.
Assuntos
Antimaláricos/farmacologia , Descoberta de Drogas , Malária/tratamento farmacológico , Plasmodium falciparum/efeitos dos fármacos , Quinolinas/farmacologia , Animais , Antimaláricos/síntese química , Antimaláricos/química , Modelos Animais de Doenças , Camundongos , Estrutura Molecular , Quinolinas/síntese química , Quinolinas/química , Relação Estrutura-AtividadeRESUMO
In this paper we describe the optimization of a phenotypic hit against Plasmodium falciparum, based on a trisubstituted pyrimidine scaffold. This led to compounds with good pharmacokinetics and oral activity in a P. berghei mouse model of malaria. The most promising compound (13) showed a reduction in parasitemia of 96% when dosed at 30 mg/kg orally once a day for 4 days in the P. berghei mouse model of malaria. It also demonstrated a rapid rate of clearance of the erythrocytic stage of P. falciparum in the SCID mouse model with an ED90 of 11.7 mg/kg when dosed orally. Unfortunately, the compound is a potent inhibitor of cytochrome P450 enzymes, probably due to a 4-pyridyl substituent. Nevertheless, this is a lead molecule with a potentially useful antimalarial profile, which could either be further optimized or be used for target hunting.
Assuntos
Antimaláricos/química , Antimaláricos/uso terapêutico , Malária/tratamento farmacológico , Plasmodium berghei/efeitos dos fármacos , Plasmodium falciparum/efeitos dos fármacos , Pirimidinas/química , Pirimidinas/uso terapêutico , Animais , Antimaláricos/farmacocinética , Antimaláricos/farmacologia , Humanos , Malária/parasitologia , Malária Falciparum/tratamento farmacológico , Malária Falciparum/parasitologia , Camundongos SCID , Parasitemia/tratamento farmacológico , Parasitemia/parasitologia , Pirimidinas/farmacocinética , Pirimidinas/farmacologiaRESUMO
The enzyme N-myristoyltransferase (NMT) from Trypanosoma brucei has been validated both chemically and biologically as a potential drug target for human African trypanosomiasis. We previously reported the development of some very potent compounds based around a pyrazole sulfonamide series, derived from a high-throughput screen. Herein we describe work around thiazolidinone and benzomorpholine scaffolds that were also identified in the screen. An X-ray crystal structure of the thiazolidinone hit in Leishmania major NMT showed the compound bound in the previously reported active site, utilising a novel binding mode. This provides potential for further optimisation. The benzomorpholinone was also found to bind in a similar region. Using an X-ray crystallography/structure-based design approach, the benzomorpholinone series was further optimised, increasing activity against T.â brucei NMT by >1000-fold. A series of trypanocidal compounds were identified with suitable in vitro DMPK properties, including CNS exposure for further development. Further work is required to increase selectivity over the human NMT isoform and activity against T.â brucei.
Assuntos
Aciltransferases/antagonistas & inibidores , Descoberta de Drogas , Inibidores Enzimáticos/farmacologia , Bibliotecas de Moléculas Pequenas/farmacologia , Trypanosoma brucei brucei/enzimologia , Aciltransferases/metabolismo , Sítios de Ligação/efeitos dos fármacos , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Humanos , Modelos Moleculares , Estrutura Molecular , Testes de Sensibilidade Parasitária , Bibliotecas de Moléculas Pequenas/síntese química , Bibliotecas de Moléculas Pequenas/química , Relação Estrutura-Atividade , Trypanosoma brucei brucei/efeitos dos fármacosRESUMO
A screen of a focused kinase inhibitor library against Trypanosoma brucei rhodesiense led to the identification of seven series, totaling 121 compounds, which showed >50 % inhibition at 5â µm. Screening of these hits in a T.â b.â brucei proliferation assay highlighted three compounds with a 1H-imidazo[4,5-b]pyrazin-2(3H)-one scaffold that showed sub-micromolar activity and excellent selectivity against the MRC5 cell line. Subsequent rounds of optimisation led to the identification of compounds that exhibited good in vitro drug metabolism and pharmacokinetics (DMPK) properties, although in general this series suffered from poor solubility. A scaffold-hopping exercise led to the identification of a 1H-pyrazolo[3,4-b]pyridine scaffold, which retained potency. A number of examples were assessed in a T.â b.â brucei growth assay, which could differentiate static and cidal action. Compounds from the 1H-imidazo[4,5-b]pyrazin-2(3H)-one series were found to be either static or growth-slowing and not cidal. Compounds with the 1H-pyrazolo[3,4-b]pyridine scaffold were found to be cidal and showed an unusual biphasic nature in this assay, suggesting they act by at least two mechanisms.