ABSTRACT
Screening of a library of small polar molecules against Mycobacterium tuberculosis (Mtb) led to the identification of a potent benzoheterocyclic oxime carbamate hit series. This series was subjected to medicinal chemistry progression underpinned by structure-activity relationship studies toward identifying a compound for proof-of-concept studies and defining a lead optimization strategy. Carbamate and free oxime frontrunner compounds with good stability in liver microsomes and no hERG channel inhibition liability were identified and evaluated in vivo for pharmacokinetic properties. Mtb-mediated permeation and metabolism studies revealed that the carbamates were acting as prodrugs. Toward mechanism of action elucidation, selected compounds were tested in biology triage assays to assess their activity against known promiscuous targets. Taken together, these data suggest a novel yet unknown mode of action for these antitubercular hits.
Subject(s)
Antitubercular Agents/pharmacology , Carbamates/pharmacology , Heterocyclic Compounds/pharmacology , Mycobacterium tuberculosis/drug effects , Oximes/pharmacology , Antitubercular Agents/chemistry , Antitubercular Agents/metabolism , Carbamates/chemistry , Carbamates/metabolism , Dose-Response Relationship, Drug , Heterocyclic Compounds/chemistry , Heterocyclic Compounds/metabolism , Microbial Sensitivity Tests , Molecular Structure , Mycobacterium tuberculosis/metabolism , Oximes/chemistry , Oximes/metabolism , Structure-Activity RelationshipABSTRACT
A novel diazaspiro[3.4]octane series was identified from a Plasmodium falciparum whole-cell high-throughput screening campaign. Hits displayed activity against multiple stages of the parasite lifecycle, which together with a novel sp3-rich scaffold provided an attractive starting point for a hit-to-lead medicinal chemistry optimization and biological profiling program. Structure-activity-relationship studies led to the identification of compounds that showed low nanomolar asexual blood-stage activity (<50 nM) together with strong gametocyte sterilizing properties that translated to transmission-blocking activity in the standard membrane feeding assay. Mechanistic studies through resistance selection with one of the analogues followed by whole-genome sequencing implicated the P. falciparum cyclic amine resistance locus in the mode of resistance.
Subject(s)
Antimalarials/pharmacology , Plasmodium falciparum/drug effects , Spiro Compounds/pharmacology , Animals , Anopheles/drug effects , Antimalarials/chemical synthesis , Antimalarials/metabolism , Female , Germ Cells/drug effects , High-Throughput Screening Assays , Humans , Male , Mice , Microsomes, Liver/metabolism , Molecular Structure , Parasitic Sensitivity Tests , Rats , Spiro Compounds/chemical synthesis , Spiro Compounds/metabolism , Structure-Activity RelationshipABSTRACT
A series of 2,4-disubstituted imidazopyridines, originating from a SoftFocus Kinase library, was identified from a high throughput phenotypic screen against the human malaria parasite Plasmodium falciparum. Hit compounds showed moderate asexual blood stage activity. During lead optimization, several issues were flagged such as cross-resistance against the multidrug-resistant K1 strain, in vitro cytotoxicity, and cardiotoxicity and were addressed through structure-activity and structure-property relationship studies. Pharmacokinetic properties were assessed in mice for compounds showing desirable in vitro activity, a selectivity window over cytotoxicity, and microsomal metabolic stability. Frontrunner compound 37 showed good exposure in mice combined with good in vitro activity against the malaria parasite, which translated into in vivo efficacy in the P. falciparum NOD-scid IL-2Rγnull (NSG) mouse model. Preliminary mechanistic studies suggest inhibition of hemozoin formation as a contributing mode of action.
Subject(s)
Antimalarials/chemistry , Hemeproteins/antagonists & inhibitors , Imidazoles/chemistry , Plasmodium falciparum/physiology , Protozoan Proteins/antagonists & inhibitors , Pyridines/chemistry , Animals , Antimalarials/metabolism , Antimalarials/pharmacology , Antimalarials/therapeutic use , Disease Models, Animal , Half-Life , Hemeproteins/metabolism , Imidazoles/metabolism , Imidazoles/pharmacology , Imidazoles/therapeutic use , Life Cycle Stages/drug effects , Malaria/drug therapy , Malaria/pathology , Mice , Mice, Inbred BALB C , Mice, Inbred NOD , Mice, SCID , Microsomes, Liver/metabolism , Plasmodium falciparum/drug effects , Plasmodium falciparum/metabolism , Protozoan Proteins/metabolism , Pyridines/metabolism , Pyridines/pharmacology , Pyridines/therapeutic use , Structure-Activity RelationshipABSTRACT
A phenotypic whole cell high-throughput screen against the asexual blood and liver stages of the malaria parasite identified a benzimidazole chemical series. Among the hits were the antiemetic benzimidazole drug Lerisetron 1 (IC50 NF54 = 0.81 µM) and its methyl-substituted analogue 2 (IC50 NF54 = 0.098 µM). A medicinal chemistry hit to lead effort led to the identification of chloro-substituted analogue 3 with high potency against the drug-sensitive NF54 (IC50 NF54 = 0.062 µM) and multidrug-resistant K1 (IC50 K1 = 0.054 µM) strains of the human malaria parasite Plasmodium falciparum. Compounds 2 and 3 gratifyingly showed in vivo efficacy in both Plasmodium berghei and P. falciparum mouse models of malaria. Cardiotoxicity risk as expressed in strong inhibition of the human ether-a-go-go-related gene (hERG) potassium channel was identified as a major liability to address. This led to the synthesis and biological assessment of around 60 analogues from which several compounds with improved antiplasmodial potency, relative to the lead compound 3, were identified.
ABSTRACT
The in vivo antimalarial efficacies of two phosphatidylinositol 4-kinase (PI4K) inhibitors, a 3,5-diaryl-2-aminopyrazine sulfoxide and its corresponding sulfone metabolite, were evaluated in the NOD-scid IL2Rγnull (NSG) murine malaria disease model of Plasmodium falciparum infection. We hypothesized that the sulfoxide would serve as a more soluble prodrug for the sulfone, which would lead to improved drug exposure with oral dosing. Both compounds had similar efficacy (90% effective dose [ED90], 0.1 mg kg-1 of body weight) across a quadruple-dose regimen. Pharmacokinetic profiling revealed rapid sulfoxide clearance via conversion to sulfone, with sulfone identified as the major active metabolite. When the sulfoxide was dosed, the exposure of the sulfone achieved was as much as 2.9-fold higher than when the sulfone was directly dosed, thereby demonstrating that the sulfoxide served as an effective prodrug for the treatment of malaria.
Subject(s)
Antimalarials/pharmacology , Malaria, Falciparum/drug therapy , Parasitemia/drug therapy , Prodrugs/pharmacology , Pyrazines/pharmacology , Sulfones/pharmacology , Sulfoxides/pharmacology , 1-Phosphatidylinositol 4-Kinase/antagonists & inhibitors , 1-Phosphatidylinositol 4-Kinase/genetics , 1-Phosphatidylinositol 4-Kinase/metabolism , Animals , Antimalarials/blood , Antimalarials/chemical synthesis , Antimalarials/pharmacokinetics , Biotransformation , Disease Models, Animal , Dose-Response Relationship, Drug , Erythrocytes/drug effects , Erythrocytes/metabolism , Erythrocytes/parasitology , Gene Expression , Humans , Malaria, Falciparum/metabolism , Malaria, Falciparum/parasitology , Malaria, Falciparum/pathology , Male , Mice , Mice, Inbred NOD , Mice, SCID , Parasitemia/pathology , Plasmodium falciparum/drug effects , Plasmodium falciparum/enzymology , Plasmodium falciparum/growth & development , Prodrugs/chemical synthesis , Prodrugs/pharmacokinetics , Pyrazines/blood , Pyrazines/chemical synthesis , Pyrazines/pharmacokinetics , Sulfones/blood , Sulfones/chemical synthesis , Sulfones/pharmacokinetics , Sulfoxides/blood , Sulfoxides/chemical synthesis , Sulfoxides/pharmacokinetics , Treatment OutcomeABSTRACT
A lead-optimization program around a 2,6-imidazopyridine scaffold was initiated based on the two early lead compounds, 1 and 2, that were shown to be efficacious in an in vivo humanized Plasmodium falciparum NODscidIL2Rγnull mouse malaria infection model. The observation of atypical dose-response curves when some compounds were tested against multidrug resistant malaria parasite strains guided the optimization process to define a chemical space that led to typical sigmoidal dose-response and complete kill of multidrug resistant parasites. After a structure and property analysis identified such a chemical space, compounds were prepared that displayed suitable activity, ADME, and safety profiles with respect to cytotoxicity and hERG inhibition.
Subject(s)
Antimalarials/chemistry , Antimalarials/pharmacology , Drug Resistance, Multiple/drug effects , Imidazoles/chemistry , Imidazoles/pharmacology , Plasmodium falciparum/drug effects , Pyridines/chemistry , Pyridines/pharmacology , Absorption, Physicochemical , Animals , Antimalarials/metabolism , Antimalarials/pharmacokinetics , Dose-Response Relationship, Drug , Imidazoles/metabolism , Imidazoles/pharmacokinetics , Mice , Pyridines/metabolism , Pyridines/pharmacokinetics , Structure-Activity Relationship , Tissue DistributionABSTRACT
The 2-aminopyridine MMV048 was the first drug candidate inhibiting Plasmodium phosphatidylinositol 4-kinase (PI4K), a novel drug target for malaria, to enter clinical development. In an effort to identify the next generation of PI4K inhibitors, the series was optimized to improve properties such as solubility and antiplasmodial potency across the parasite life cycle, leading to the 2-aminopyrazine UCT943. The compound displayed higher asexual blood stage, transmission-blocking, and liver stage activities than MMV048 and was more potent against resistant Plasmodium falciparum and Plasmodium vivax clinical isolates. Excellent in vitro antiplasmodial activity translated into high efficacy in Plasmodium berghei and humanized P. falciparum NOD-scid IL-2Rγ null mouse models. The high passive permeability and high aqueous solubility of UCT943, combined with low to moderate in vivo intrinsic clearance, resulted in sustained exposure and high bioavailability in preclinical species. In addition, the predicted human dose for a curative single administration using monkey and dog pharmacokinetics was low, ranging from 50 to 80 mg. As a next-generation Plasmodium PI4K inhibitor, UCT943, based on the combined preclinical data, has the potential to form part of a single-exposure radical cure and prophylaxis (SERCaP) to treat, prevent, and block the transmission of malaria.
ABSTRACT
A novel 2,8-disubstituted-1,5-naphthyridine hit compound stemming from the open access Medicines for Malaria Venture Pathogen Box formed a basis for a hit-to-lead medicinal chemistry program. Structure-activity relationship investigations resulted in compounds with potent antiplasmodial activity against both chloroquine sensitive (NF54) and multidrug resistant (K1) strains of the human malaria parasite Plasmodium falciparum. In the humanized P. falciparum mouse efficacy model, one of the frontrunner compounds showed in vivo efficacy at an oral dose of 4 × 50 mg·kg-1. In vitro mode-of-action studies revealed Plasmodium falciparum phosphatidylinositol-4-kinase as the target.
Subject(s)
1-Phosphatidylinositol 4-Kinase/antagonists & inhibitors , Malaria/drug therapy , Naphthyridines/chemistry , Naphthyridines/pharmacology , Plasmodium falciparum/drug effects , Plasmodium falciparum/enzymology , 1-Phosphatidylinositol 4-Kinase/chemistry , Animals , Antimalarials/chemistry , Antimalarials/pharmacokinetics , Antimalarials/pharmacology , Antimalarials/therapeutic use , Disease Models, Animal , Drug Design , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacokinetics , Enzyme Inhibitors/pharmacology , Enzyme Inhibitors/therapeutic use , Humans , Mice , Models, Molecular , Naphthyridines/pharmacokinetics , Naphthyridines/therapeutic use , Plasmodium falciparum/physiology , Protein Conformation , Structure-Activity Relationship , Tissue DistributionABSTRACT
Optimization of a chemical series originating from whole-cell phenotypic screening against the human malaria parasite, Plasmodium falciparum, led to the identification of two promising 2,6-disubstituted imidazopyridine compounds, 43 and 74. These compounds exhibited potent activity against asexual blood stage parasites that, together with their in vitro absorption, distribution, metabolism, and excretion (ADME) properties, translated to in vivo efficacy with clearance of parasites in the PfSCID mouse model for malaria within 48 h of treatment.
Subject(s)
Drug Discovery , Imidazoles/chemistry , Imidazoles/pharmacokinetics , Malaria/drug therapy , Plasmodium falciparum/physiology , Pyridines/chemistry , Pyridines/pharmacokinetics , Animals , Disease Models, Animal , Drug Stability , ERG1 Potassium Channel/metabolism , Humans , Imidazoles/metabolism , Imidazoles/therapeutic use , Malaria/genetics , Malaria/metabolism , Mice , Pyridines/metabolism , Pyridines/therapeutic use , Solubility , Structure-Activity Relationship , Tissue Distribution , Water/chemistryABSTRACT
Despite increased research efforts to find new treatments for tuberculosis in recent decades, compounds with novel mechanisms of action are still required. We previously identified a series of novel aryl-oxadiazoles with anti-tubercular activity specific for bacteria using butyrate as a carbon source. We explored the structure activity relationship of this series. Structural modifications were performed in all domains to improve potency and physico-chemical properties. A number of compounds displayed sub-micromolar activity against M. tuberculosis utilizing butyrate, but not glucose as the carbon source. Compounds showed no or low cytotoxicity against eukaryotic cells. Three compounds were profiled in mouse pharmacokinetic studies. Plasma clearance was low to moderate but oral exposure suggested solubility-limited drug absorption in addition to first pass metabolism. The presence of a basic nitrogen in the linker slightly increased solubility, and salt formation optimized aqueous solubility. Our findings suggest that the 1,3,4-oxadiazoles are useful tools and warrant further investigation.
Subject(s)
Anti-Bacterial Agents/pharmacology , Mycobacterium tuberculosis/drug effects , Oxadiazoles/pharmacology , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Dose-Response Relationship, Drug , Microbial Sensitivity Tests , Molecular Structure , Oxadiazoles/chemical synthesis , Oxadiazoles/chemistry , Structure-Activity RelationshipABSTRACT
Mycobacterium tuberculosis ( MTb) possesses two nonproton pumping type II NADH dehydrogenase (NDH-2) enzymes which are predicted to be jointly essential for respiratory metabolism. Furthermore, the structure of a closely related bacterial NDH-2 has been reported recently, allowing for the structure-based design of small-molecule inhibitors. Herein, we disclose MTb whole-cell structure-activity relationships (SARs) for a series of 2-mercapto-quinazolinones which target the ndh encoded NDH-2 with nanomolar potencies. The compounds were inactivated by glutathione-dependent adduct formation as well as quinazolinone oxidation in microsomes. Pharmacokinetic studies demonstrated modest bioavailability and compound exposures. Resistance to the compounds in MTb was conferred by promoter mutations in the alternative nonessential NDH-2 encoded by ndhA in MTb. Bioenergetic analyses revealed a decrease in oxygen consumption rates in response to inhibitor in cells in which membrane potential was uncoupled from ATP production, while inverted membrane vesicles showed mercapto-quinazolinone-dependent inhibition of ATP production when NADH was the electron donor to the respiratory chain. Enzyme kinetic studies further demonstrated noncompetitive inhibition, suggesting binding of this scaffold to an allosteric site. In summary, while the initial MTb SAR showed limited improvement in potency, these results, combined with structural information on the bacterial protein, will aid in the future discovery of new and improved NDH-2 inhibitors.
Subject(s)
Mycobacterium tuberculosis/enzymology , NADH Dehydrogenase/chemistry , Quinazolinones/chemistry , Molecular Structure , NADH Dehydrogenase/antagonists & inhibitors , Quinazolinones/chemical synthesis , Quinazolinones/pharmacology , Structure-Activity RelationshipABSTRACT
Objectives: Novel chemical tools to eliminate malaria should ideally target both the asexual parasites and transmissible gametocytes. Several imidazopyridazines (IMPs) and 2-aminopyridines (2-APs) have been described as potent antimalarial candidates targeting lipid kinases. However, these have not been extensively explored for stage-specific inhibition of gametocytes in Plasmodium falciparum parasites. Here we provide an in-depth evaluation of the gametocytocidal activity of compounds from these chemotypes and identify novel starting points for dual-acting antimalarials. Methods: We evaluated compounds against P. falciparum gametocytes using several assay platforms for cross-validation and stringently identified hits that were further profiled for stage specificity, speed of action and ex vivo efficacy. Physicochemical feature extraction and chemogenomic fingerprinting were applied to explore the kinase inhibition susceptibility profile. Results: We identified 34 compounds with submicromolar activity against late stage gametocytes, validated across several assay platforms. Of these, 12 were potent at <100 nM (8 were IMPs and 4 were 2-APs) and were also active against early stage gametocytes and asexual parasites, with >1000-fold selectivity towards the parasite over mammalian cells. Front-runner compounds targeted mature gametocytes within 48 h and blocked transmission to mosquitoes. The resultant chemogenomic fingerprint of parasites treated with the lead compounds revealed the importance of targeting kinases in asexual parasites and gametocytes. Conclusions: This study encompasses an in-depth evaluation of the kinase inhibitor space for gametocytocidal activity. Potent lead compounds have enticing dual activities and highlight the importance of targeting the kinase superfamily in malaria elimination strategies.
Subject(s)
Aminopyridines/pharmacology , Antimalarials/pharmacology , Phosphotransferases/antagonists & inhibitors , Plasmodium falciparum/drug effects , Plasmodium falciparum/enzymology , Protein Kinase Inhibitors/pharmacology , Aminopyridines/chemistry , Aminopyridines/isolation & purification , Antimalarials/chemistry , Antimalarials/isolation & purification , Cell Survival/drug effects , Inhibitory Concentration 50 , Parasitic Sensitivity Tests , Plasmodium falciparum/chemistry , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/isolation & purificationABSTRACT
A BioFocus DPI SoftFocus library of â¼35â¯000 compounds was screened against Mycobacterium tuberculosis (Mtb) in order to identify novel hits with antitubercular activity. The hits were evaluated in biology triage assays to exclude compounds suggested to function via frequently encountered promiscuous mechanisms of action including inhibition of the QcrB subunit of the cytochrome bc1 complex, disruption of cell-wall homeostasis, and DNA damage. Among the hits that passed this screening cascade, a 6-dialkylaminopyrimidine carboxamide series was prioritized for hit to lead optimization. Compounds from this series were active against clinical Mtb strains, while no cross-resistance to conventional antituberculosis drugs was observed. This suggested a novel mechanism of action, which was confirmed by chemoproteomic analysis leading to the identification of BCG_3193 and BCG_3827 as putative targets of the series with unknown function. Initial structure-activity relationship studies have resulted in compounds with moderate to potent antitubercular activity and improved physicochemical properties.
Subject(s)
Antitubercular Agents/chemistry , Antitubercular Agents/pharmacology , Mycobacterium tuberculosis/drug effects , Structure-Activity Relationship , Administration, Oral , Animals , Antitubercular Agents/chemical synthesis , Blood Proteins/metabolism , Drug Stability , High-Throughput Screening Assays , Humans , Male , Mice, Inbred C57BL , Microsomes, Liver/drug effects , Mycobacterium tuberculosis/isolation & purification , Proteomics/methods , Pyrimidines/chemistry , Small Molecule Libraries/chemistry , Small Molecule Libraries/pharmacologyABSTRACT
Introduction of water-solubilizing groups on the 5-phenyl ring of a 2-aminopyrazine series led to the identification of highly potent compounds against the blood life-cycle stage of the human malaria parasite Plasmodium falciparum. Several compounds displayed high in vivo efficacy in two different mouse models for malaria, P. berghei-infected mice and P. falciparum-infected NOD-scid IL-2Rγnull mice. One of the frontrunners, compound 3, was identified to also have good pharmacokinetics and additionally very potent activity against the liver and gametocyte parasite life-cycle stages.
Subject(s)
Antimalarials/pharmacology , Life Cycle Stages/drug effects , Malaria/drug therapy , Parasitic Diseases, Animal/drug therapy , Plasmodium berghei/drug effects , Plasmodium falciparum/drug effects , Pyrazines/pharmacology , Animals , Antimalarials/chemistry , Antimalarials/metabolism , Disease Models, Animal , Dose-Response Relationship, Drug , Ether-A-Go-Go Potassium Channels/antagonists & inhibitors , Ether-A-Go-Go Potassium Channels/metabolism , Hep G2 Cells , Humans , Mice , Mice, SCID , Microsomes, Liver/chemistry , Microsomes, Liver/metabolism , Molecular Structure , Parasitic Diseases, Animal/parasitology , Parasitic Sensitivity Tests , Plasmodium berghei/growth & development , Plasmodium falciparum/growth & development , Pyrazines/chemistry , Pyrazines/metabolism , Solubility , Structure-Activity Relationship , Water/chemistryABSTRACT
High-throughput screening of a library of small polar molecules against Mycobacterium tuberculosis led to the identification of a phthalimide-containing ester hit compound (1), which was optimized for metabolic stability by replacing the ester moiety with a methyl oxadiazole bioisostere. A route utilizing polymer-supported reagents was designed and executed to explore structure-activity relationships with respect to the N-benzyl substituent, leading to compounds with nanomolar activity. The frontrunner compound (5h) from these studies was well tolerated in mice. A M. tuberculosis cytochrome bd oxidase deletion mutant (ΔcydKO) was hyper-susceptible to compounds from this series, and a strain carrying a single point mutation in qcrB, the gene encoding a subunit of the menaquinol cytochrome c oxidoreductase, was resistant to compounds in this series. In combination, these observations indicate that this novel class of antimycobacterial compounds inhibits the cytochrome bc1 complex, a validated drug target in M. tuberculosis.
Subject(s)
Antitubercular Agents/chemistry , Antitubercular Agents/pharmacology , Electron Transport Complex III/antagonists & inhibitors , Mycobacterium tuberculosis/drug effects , Mycobacterium tuberculosis/enzymology , Pyrroles/chemistry , Pyrroles/pharmacology , Animals , Antitubercular Agents/metabolism , Antitubercular Agents/pharmacokinetics , Electron Transport Complex III/metabolism , Humans , Mice , Microsomes, Liver/metabolism , Molecular Targeted Therapy , Pyridones/chemistry , Pyridones/metabolism , Pyridones/pharmacokinetics , Pyridones/pharmacology , Pyrroles/metabolism , Pyrroles/pharmacokinetics , Rats , Tuberculosis/drug therapy , Tuberculosis/microbiologyABSTRACT
Whole-cell high-throughput screening of a diverse SoftFocus library against Mycobacterium tuberculosis (Mtb) generated a novel aminopyrazolo[1,5-a]pyrimidine hit series. The synthesis and structure activity relationship studies identified compounds with potent antimycobacterial activity. The SAR of over 140 compounds shows that the 2-pyridylmethylamine moiety at the C-7 position of the pyrazolopyrimidine scaffold was important for Mtb activity, whereas the C-3 position offered a higher degree of flexibility. The series was also profiled for in vitro cytotoxicity and microsomal metabolic stability as well as physicochemical properties. Consequently liabilities to be addressed in a future lead optimization campaign have been identified.
Subject(s)
Antitubercular Agents/pharmacology , Mycobacterium tuberculosis/drug effects , Pyrazoles/chemistry , Pyrimidines/chemistry , Animals , Antitubercular Agents/chemistry , Antitubercular Agents/metabolism , CHO Cells , Cell Survival/drug effects , Cricetinae , Cricetulus , Drug Design , Half-Life , Mice , Microbial Sensitivity Tests , Microsomes, Liver/metabolism , Pyrazoles/chemical synthesis , Pyrazoles/pharmacology , Pyrimidines/chemical synthesis , Pyrimidines/pharmacology , Rats , Solubility , Structure-Activity RelationshipABSTRACT
Toward improving pharmacokinetics, in vivo efficacy, and selectivity over hERG, structure-activity relationship studies around the central core of antimalarial imidazopyridazines were conducted. This study led to the identification of potent pyrazolopyridines, which showed good in vivo efficacy and pharmacokinetics profiles. The lead compounds also proved to be very potent in the parasite liver and gametocyte stages, which makes them of high interest.
Subject(s)
Antimalarials/chemistry , Antimalarials/therapeutic use , Malaria/drug therapy , Plasmodium berghei/drug effects , Plasmodium falciparum/drug effects , Pyrazoles/chemistry , Pyrazoles/therapeutic use , Pyridines/chemistry , Pyridines/therapeutic use , Animals , Antimalarials/pharmacokinetics , Antimalarials/pharmacology , Ether-A-Go-Go Potassium Channels/metabolism , Humans , Liver/parasitology , Malaria/parasitology , Malaria, Falciparum/drug therapy , Malaria, Falciparum/parasitology , Mice , Pyrazoles/pharmacokinetics , Pyrazoles/pharmacology , Pyridines/pharmacokinetics , Pyridines/pharmacology , Rats , Structure-Activity RelationshipABSTRACT
Based on the initial optimization of orally active antimalarial 2,4-diamino-thienopyrimidines and with the help of metabolite identification studies, a second generation of derivatives involving changes at the 2- and 4-positions of the thienopyrimidine core were synthesized. Improvements in the physiochemical properties resulted in the identification of 15a, 17a, 32, and 40 as lead molecules with improved in vivo exposure. Furthermore, analogue 40 exhibited excellent in vivo antimalarial activity when dosed orally at 50 mg/kg once daily for 4 days in the Plasmodium berghei mouse model, which is superior to the activity seen with previously reported compounds, and with a slightly improved hERG profile.