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Aims: The objective of this meta‐analysis was to determine whether maternal exposure to folate antagonists is associated with increased rates of congenital heart disease in offspring. Methods: A comprehensive search for articles in the MEDLINE (PubMed) and EMBASE databases published up to 21 August 2023 was performed. The search strategy was not limited by study design but only for articles in the English language. Results: Analysis of 6 cohort studies and 5 cross‐sectional studies, published between 1976 and 2020, showed significant increase in rate of congenital heart disease (odds ratio 1.55, 95% confidence interval, 1.28–1.87) when exposed to folate antagonists compared with the control. Further subgroup analysis showed the increased rate for exposure to both dihydrofolate reductase inhibitors and antiepileptic drugs separately. No differences were observed when analyses were stratified by timing of study. Conclusion: Administration of folate antagonists within the 12‐week period preceding conception and throughout the second and third months of gestation exhibited a statistically significant elevation in the susceptibility to congenital heart diseases. Notably, the protective effect of folic acid supplementation was reported in cases of congenital heart disease linked to dihydrofolate reductase inhibitors but not that associated with antiepileptic drugs. [ABSTRACT FROM AUTHOR]

Malaria, leishmaniasis, and African trypanosomiasis are protozoan diseases that constitute major global health problems, especially in developing countries; however, the development of drug resistance coupled with the toxicity of current treatments has hindered their management. The involvement of certain enzymes (dihydrofolate reductase [DHFR]) or proteins (potassium channels) in the pathogenesis of these protozoan diseases is undeniable. In this study, a series of three DHFR inhibitors (6-5 fused heterocyclic derivatives X, Y, and Z) and one K+ channel blocker (E4031) were screened for their inhibitory effects on Leishmania donovani, Plasmodium falciparum, and Trypanosoma brucei. A resazurin assay was used to assess the antitrypanosomal and antileishmanial activities of the test compounds, whereas the antiplasmodial activity was evaluated through the SYBR Green I test. Moreover, the cytotoxicities of the test compounds were evaluated in Vero, Raw 264.7, and HepG-2 cells using a resazurin-based test, while their pharmacokinetic properties were predicted using the online tool, pkCSM. As a result, compound Y exhibited selective (selectivity index range: from 2.69 to >61.4; Vero, Raw 264.7, and HepG-2 cells) and broad-spectrum antiprotozoal activity against L. donovani promastigotes (IC50: 12.4 µM), amastigotes (IC50: 4.28 µM), P. falciparum (IC50: 0.028 µM), and T. brucei brucei (IC50: 0.81 µM). In addition, compound X inhibited the growth of P. falciparum (IC50: 0.0052 µM) and T. brucei brucei (IC50: 6.49 µM). In silico screening of the active antiprotozoal compounds revealed positive drug likeness scores, as none of the criteria for Lipinski's rule were violated by these compounds. However, in-depth pharmacokinetic and mechanistic studies are warranted to support the discovery of novel antiprotozoal agents against malaria, leishmaniasis, and African trypanosomiasis by repurposing K+ channel blockers and DHFR inhibitors. [ABSTRACT FROM AUTHOR]

Malaria, leishmaniasis, and African trypanosomiasis are protozoan diseases that constitute major global health problems, especially in developing countries; however, the development of drug resistance coupled with the toxicity of current treatments has hindered their management. The involvement of certain enzymes (dihydrofolate reductase [DHFR]) or proteins (potassium channels) in the pathogenesis of these protozoan diseases is undeniable. In this study, a series of three DHFR inhibitors (6-5 fused heterocyclic derivatives X, Y, and Z) and one K+ channel blocker (E4031) were screened for their inhibitory effects on Leishmania donovani, Plasmodium falciparum, and Trypanosoma brucei. A resazurin assay was used to assess the antitrypanosomal and antileishmanial activities of the test compounds, whereas the antiplasmodial activity was evaluated through the SYBR Green I test. Moreover, the cytotoxicities of the test compounds were evaluated in Vero, Raw 264.7, and HepG-2 cells using a resazurin-based test, while their pharmacokinetic properties were predicted using the online tool, pkCSM. As a result, compound Y exhibited selective (selectivity index range: from 2.69 to >61.4; Vero, Raw 264.7, and HepG-2 cells) and broad-spectrum antiprotozoal activity against L. donovani promastigotes (IC50: 12.4 µM), amastigotes (IC50: 4.28 µM), P. falciparum (IC50: 0.028 µM), and T. brucei brucei (IC50: 0.81 µM). In addition, compound X inhibited the growth of P. falciparum (IC50: 0.0052 µM) and T. brucei brucei (IC50: 6.49 µM). In silico screening of the active antiprotozoal compounds revealed positive drug likeness scores, as none of the criteria for Lipinski’s rule were violated by these compounds. However, in-depth pharmacokinetic and mechanistic studies are warranted to support the discovery of novel antiprotozoal agents against malaria, leishmaniasis, and African trypanosomiasis by repurposing K+ channel blockers and DHFR inhibitors.

The present work deals with synthesis and biological evaluation of novel compounds as potential inhibitors of dihydrofolate reductase (DHFR) from opportunistic microorganisms – Pneumocystis carinii (pc), Toxoplasma gondii (tg) and Mycobacterium avium (ma). A set of 6 lipophilic and 1 classical antifolates of thieno[2,3-d]pyrimidine series were designed and synthesised with key pharmacophoric features of DHFR inhibitors and aminomethylene bridge joining the aromatic part and 2-amino-4-oxothieno[2,3-d]pyrimidine nucleus. Investigation of the DHFR inhibitory activity of the synthesised compounds revealed that 2-amino-6-[(4-methoxyphenylamino)-, 6--[(4-chlorophenylamino)- and 6-[(2,5-dichlorophenylamino)methyl]thieno[2,3-d]pyrimidin-4(3H)- ones had a moderate activity (IC50 56.5, 49.9 and 23 μM, respectively) against pcDHFR. Activity of those compounds against tgDHFR (IC50 6.0, 2.8 and 2.3 μM, respectively) was comparable to that of trimethoprim (IC50 2.7 μM). No synthesised lipophilic antifolates showed activity towards maDHFR. The classical antifolate 2-{4-[(2-amino-4-oxo-3,4- dihydrothieno[2,3-d]pyrimidin-6-yl)methylamino]benzamido}-L-glutamic acid inhibited DHFRs from all microorganisms (IC50 6.6 μM for pcDHFR, 1.06 μM for tgDHFR and 16.9 μM for maDHFR). [ABSTRACT FROM AUTHOR]

Dihydrofolate reductase (DHFR) enzyme is a crucial component of cell growth and proliferation in the human body, making it an important target for treating cancer diseases. This study aims to predict the inhibitory activity (pXC50) of dihydrofolate reductase inhibitors in terms of the quantitative structure-activity relationship (QSAR) model. Interpretation of the QSAR model is vital for understanding the physicochemical processes and to assist structural optimisation. Multivariate adaptive regression splines (MARS), a non-parametric technique, is proposed to model the non-linear relationship between the predictor variables and the response variable of a high-dimensional dataset. The dataset used in this research consists of pXC50 activity of 778 DHFR inhibitors. For our study, the data is divided into 80% training set for model building and 20% testing set for model validation. In comparison, the baseline methods deep neural network (DNN) and partial least squares (PLS) are also applied to QSAR modeling. The testing results show that MARS has the best prediction accuracy according to different measures, where RMSE, MAE, MAPE, and RMSPE are 0.96, 0.69, 0.11, and 0.15 respectively. The efficiency of MARS is apparent in its robust interaction of variables, prediction accuracy, and ability to overcome the neural network’s black box system. Thus, MARS technique can be considered an excellent tool for modeling QSAR high-dimensional datasets while exploring the non-linear patterns of data.

Folate enzymes, namely, dihydrofolate reductase (DHFR) and pteridine reductase (PTR1) are acknowledged targets for the development of antiparasitic agents against Trypanosomiasis and Leishmaniasis. Based on the amino dihydrotriazine motif of the drug Cycloguanil (Cyc), a known inhibitor of both folate enzymes, we have identified two novel series of inhibitors, the 2-amino triazino benzimidazoles ( 1 ) and 2-guanidino benzimidazoles ( 2 ), as their open ring analogues. Enzymatic screening was carried out against PTR1, DHFR, and thymidylate synthase (TS). The crystal structures of Tb DHFR and Tb PTR1 in complex with selected compounds experienced in both cases a substrate-like binding mode and allowed the rationalization of the main chemical features supporting the inhibitor ability to target folate enzymes. Biological evaluation of both series was performed against T. brucei and L. infantum and the toxicity against THP-1 human macrophages. Notably, the 5,6-dimethyl-2-guanidinobenzimidazole 2g resulted to be the most potent ( K i = 9 nM) and highly selective Tb DHFR inhibitor, 6000-fold over Tb PTR1 and 394-fold over h DHFR. The 5,6-dimethyl tricyclic analogue 1g , despite showing a lower potency and selectivity profile than 2g , shared a comparable antiparasitic activity against T. brucei in the low micromolar domain. The dichloro-substituted 2-guanidino benzimidazoles 2c and 2d revealed their potent and broad-spectrum antitrypanosomatid activity affecting the growth of T. brucei and L. infantum parasites. Therefore, both chemotypes could represent promising templates that could be valorized for further drug development.

In this work, co-crystal screening was carried out for two important dihydrofolate reductase (DHFR) inhibitors, trimethoprim (TMP) and pyrimethamine (PMA), and for 2,4-diaminopyrimidine (DAP), which is the pharmacophore of these active pharmaceutical ingredients (API). The isomeric pyridinecarboxamides and two xanthines, theophylline (THEO) and caffeine (CAF), were used as co-formers in the same experimental conditions, in order to evaluate the potential for the pharmacophore to be used as a guide in the screening process. In silico co-crystal screening was carried out using BIOVIA COSMOquick and experimental screening was performed by mechanochemistry and supported by (solid + liquid) binary phase diagrams, infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). The in silico prediction of low propensities for DAP, TMP and PMA to co-crystallize with pyridinecarboxamides was confirmed: a successful outcome was only observed for DAP + nicotinamide. Successful synthesis of multicomponent solid forms was achieved for all three target molecules with theophylline, with DAP co-crystals revealing a greater variety of stoichiometries. The crystalline structures of a (1:2) TMP:THEO co-crystal and of a (1:2:1) DAP:THEO:ethyl acetate solvate were solved. This work demonstrated the possible use of the pharmacophore of DHFR inhibitors as a guide for co-crystal screening, recognizing some similar trends in the outcome of association in the solid state and in the molecular aggregation in the co-crystals, characterized by the same supramolecular synthons.

Antimicrobial agents are currently the mainstay of treatment for bacterial infections worldwide. However, due to the increased use of antimicrobials in both human and animal medicine, pathogens have now evolved to possess high levels of multi-drug resistance, leading to the persistence and spread of difficult-to-treat infections. Several current antibacterial agents active against Gram-positive bacteria will be rendered useless in the face of increasing resistance rates. There are several emerging antibiotics under development, some of which have been shown to be more effective with an improved safety profile than current treatment regimens against Gram-positive bacteria. We will extensively discuss these antibiotics under clinical development (phase I-III clinical trials) to combat Gram-positive bacteria, such as Staphylococcus aureus, Enterococcus faecium and Streptococcus pneumoniae. We will delve into the mechanism of actions, microbiological spectrum, and, where available, the pharmacokinetics, safety profile, and efficacy of these drugs, aiming to provide a comprehensive review to the involved stakeholders.

Objective: The present study focussed on the synthesis of pyridazine analogs to explore broad-spectrum antimicrobial study. Since pyridazine analogs are not conventionally found in nature, and hence, its analogs are studied later. Materials and Methods: All the synthesized compounds were characterized by spectroscopic techniques, namely, UV, IR,1HNMR, and mass spectrometry. Antimicrobial activity was screened by serial dilution method and absorbance was recorded using ELISA reader, subsequently minimum inhibitory concentrations were determined. Docking study was done into the active site of dihydrofolate reductase using Auto Dock 4.2. Results: The present investigation about synthesis, characterization, and biological studies of some new pyridazine analogs were carried out to obtain potent and pharmacologically active compounds. The free energy of binding was in the range of −5.12 to −8.97 kcal/mole. In silico study report was in good tune with laboratory experiments. Conclusions: Most of the compounds were moderate-to-good toward the antimicrobial activity. Compound AJ27 was found to be most active. Results of anti-microbial activity establishes the importance of N3, N6-diphenylpyridazine-3,6-diamine as the basic skeleton required for the antimicrobial activity. [ABSTRACT FROM AUTHOR]

Objectives/Background: Dihydrofolate reductase (DHFR) is one of the validated drug targets in Mycobacterium tuberculosis (Mtb) infection. DHFR inhibitors have been used to treat various life-threatening diseases such as cancer, malaria, and several bacterial infections. However, all clinically effective DHFR inhibitors are non-selective, and inhibit both human and pathogenic DHFRs more or less to a similar extent. The crystal structure of various DHFRs complexed with nicotinamide adenine dinucleotide phosphate and different inhibitors is available in the protein data bank. The crystal structures are validated and have been used for new drug designing. M. tuberculosis DHFRs and human (h) DHFRs show 26% structure similarity, but their active sites are not identical and this characteristic forms the basis of this study. Because most of the reported inhibitors of M. tuberculosis DHFR are pteridine based and nonselective in nature, that is, they inhibit both microbial and host DHFRs, this study aimed to design and develop selective nonpteridine M. tuberculosis DHFR inhibitors. Method: In the ternary complex of methotrexate with M. tuberculosis DHFR, whose structure is also available in the protein data bank, the side of the aminopterin ring is accessible to the solvent; additionally, a glycerol “A” molecule is found in a depression nearby. This glycerol molecule interacts with the side chains of Trp22, Asp27, and Gln28, which form a pocket in M. tuberculosis DHFR; by contrast, glycerol is absent in h-DHFR. In the h-DHFRs (complexed with folate or N-(4-carboxy-{-[(2, 4-diamino pteridine-6-yl methyl)-amino]-benzoyl amino} -butyl) pthalamic acid (COP)), the site is well packed with three hydrophobic residue side chains, Leu22, Pro26, and Phe31, which correspond to Leu20, Arg23, and Gln28, respectively, found in M. tuberculosis DHFR. Therefore, compounds with side chain, which could mimic the binding mode of glycerol to protein, may bind to M. tuberculosis DHFR selectively. Such a derivative should be sterically and chemically hindered from forming a complex with h-DHFR. This assumption forms the basis of this study and this understanding has been used for designing selective inhibitors of M. tuberculosis DHFR. Results: A number of novel nonpteridine-based molecules have been identified after the virtual screening of three databases (MDPI, NCI and inhouse databases). The best molecules identified after screening the three databases have been synthesized and tested for antitubercular activity. The results are promising and require further work in this direction. Conclusion: Structure based drug design can be used as an effective tool for the design of new cheiocal entity. Number of novel agents have been identified as antitubercular agents whose mechanism of action needs to be ascertained.

Introduction: Dihydrofolate reductase (DHFR) plays an important role in the biosynthesis of amino acid and folic acid. It participates by reducing dihydrofolate to tetrahydrofolate, in the presence of nicotinamide dinucleotide phosphate cofactor, and has been verified by various clinical studies to use DHFR as a target for the treatment of cancer and various bacterial infections., Area Covered: In this review, we have disclosed patents of synthetics and natural DHFR inhibitors with diaminopyrimidine and quinazoline nucleus from 2001. Additionally, this review highlights the clinical progression of numerous DHFR inhibitors received from the last five years., Expert Opinion: From 2001 to 2021, numerous active chemical scaffolds have been introduced and are exposed as lead candidates that have entered clinical trials as potent DHFR inhibitors. Moreover, researchers have paid considerable attention to the development of a new class of DHFR inhibitors with higher selectivity and potency. This development includes synthesis of synthetic as well as natural compounds that are potent DHFR inhibitors. On the basis of literature review, we can anticipate that there are a huge number of novel active molecules available for the future that could possess superior abilities to target this enzyme with a profound pharmacological profile.

The aim of this work is modeling the activities of 67 E. coli dihydrofolate reductase (DHFR) inhibitors 2,4-diamino-5-(substituted benzyl) pyramidines by optimization of correlation weights of local graph invariants (cwlgis), assisting genetic algorithm (GA). The relationship between the descriptors and molecular activities was modeled using radial basis function partial least squares (rbfPLS). Proper relation between activities and the optimized molecular descriptors were shown, R = 0.92 and r = 0.85. The results indicate promising potential for the optimization of a correlation weights scheme. It is the first application of GA in optimization of cwlgis. The study also shows the ability of rbfPLS, combined with GA, in a factor-based nonlinear QSAR modeling using simple flexible descriptors. [ABSTRACT FROM AUTHOR]

Abstract: Recent evidences suggest that cancer treatment based on combination of cytostatic and conventional chemostatic therapeutics, which are usually cytotoxic, can provide an improved curative option. On the sequence of our previous work on methotrexate (MTX) derivatives, we have developed and evaluated novel MTX analogues, containing a pteridine moiety conjugated with benzenesulfonamide derivatives, thus endowed with the potential capacity for dual inhibition of dihydrofolate reductase (DHFR) and carbonic anhydrases (CA). These enzymes are often overexpressed in tumors and are involved in two unrelated cellular pathways, important for tumor survival and progression. Their simultaneous inhibition may turn beneficial in terms of enhanced antitumor activity. Herein we report the design and synthesis of several diaminopteridine–benzenesulfonamide and -benzenesulfonate conjugates, differing in the nature and size of the spacer group between the two key moieties. The inhibition studies performed on a set of CAs and DHFR, revealed the activities in the low nanomolar and low micromolar ranges of concentration, respectively. Some inhibitors showed selectivity for the tumor-related CA (isozyme IX). Cell proliferation assays using two tumor cell lines (the non-small cell lung carcinoma, A549, and prostate carcinoma, PC-3) showed activities only in the millimolar range. Nevertheless, this fact points out the need of improving the cell intake properties of these new compounds, since the general inhibitory profiles revealed their potential as anticancer agents. [Copyright &y& Elsevier]

Two triazaspirodienes, having similar phenoxy propyloxy side chain, were identified as potent mammalian dihydrofolate reductase inhibitors; one having a 6,5-spiro bicyclic ring system (IC50 = 2.3 nm) and the other a 6,6-spiro bicyclic system (IC50 = 6.9 nm). They also showed more than 50% antiproliferative activity against the MCF-7 breast cancer cells at 20 μm. This study demonstrated the potential lead of the diamino-triazaspirodienes in anticancer chemotherapeutical agents’ discovery. [ABSTRACT FROM AUTHOR]

The dihydrofolate reductase inhibitors (DHFRIs) are a group of antibiotic compounds with closely related chemical structures. A previous attempt to separate the eight compounds by CZE was successful, but only at low pH (2.1) and high buffer concentration (250?mM phosphate). As a result, baseline noise was high. Additionally, baseline resolution was not quite achieved and the separation took 25 minutes. However, the size-based separation indicated that reversed-phase HPLC might be a good alternative. A three-dimensional overlapping resolution mapping (ORsM) scheme utilised pH, flow rate and percentage organic modifier (for both methanol and acetonitrile). Clear generalised outcomes were observed under isocratic conditions. At higher pHs, where the analytes were largely unionised, retention was excessive. At higher percentages of MeOH or ACN, the more-difficult-to-separate components were poorly resolved. On the other hand, low pHs (2.5 in 50?mM phosphate) with low percentages of the organic modifiers (7% ACN or 11% MeOH) but high flow rates (2.3?mL?min-1) yielded better than baseline resolution in 17 minutes. A partially optimised gradient run (at pH 6.5) again yielded far better than baseline resolution in 12 minutes, but required 4 minutes re-equilibration. Hence, the HPLC separations are superior to the CZE separation in all of runtime (40%), resolution and limit of detection (down by 6). [ABSTRACT FROM AUTHOR]

Three-dimensional quantitative structure-activity relationship (3D-QSAR) modelling using comparative molecular similarity indices analysis (CoMSIA) was applied to a series of 406 structurally diverse dihydrofolate reductase (DHFR) inhibitors fromPneumocystis carinii(pc) and rat liver (rl). X-ray crystal structures of three inhibitors bound to pcDHFR were used for defining the alignment rule. For pcDHFR, a QSAR model containing 6 components was selected using leave-10%-out cross-validation (n=240, q2=0.65), while a 4-component model was selected for rlDHFR (n=237, q2=0.63); both include steric, electrostatic and hydrophobic contributions. The models were validated using a large test set, designed to maximise its diversity and to verify the predictive accuracy of models for extrapolation. The pcDHFR model has r2=0.60 and mean absolute error (MAE) = 0.57 for the test set after removing 4 outliers, and the rlDHFR model has r2=0.60 and MAE = 0.69 after removing 4 test set outliers. In addition, classification models predicting selectivity for pcDHFR over rlDHFR were developed using soft independent modelling by class analogy (SIMCA), with a selectivity ratio of 2 (IC50,rlDHFR/ IC50,pcDHFR) used for delimiting classes. A 5-component model including steric and electrostatic contributions has cross-validated and test set classification rates of 0.67 and 0.68 for selective inhibitors, and 0.85 and 0.72 for unselective inhibitors. The predictive accuracy of models, together with the identification of important contributions in QSAR and classification models, offer the possibility of designing potent selective inhibitors and estimating their activity prior to synthesis. [ABSTRACT FROM AUTHOR]

The nearest neighboring code (NNC) is a local graph invariant. The NNC of a given vertex of the labeled hydrogen filled graph (LHFG) is a function of atom composition of the vertex neighbors. By optimization correlation weights of local invariants of the LHFG one-variable models of dihydrofolate reductase inhibitory activity have been obtained. As local graph invariants Morgan extended connectivity of zero, first, and second orders as well as the NNCs have been used. Best such model has been obtained with the NNC. Statistical characteristics of the model are the follows: Training set: n=33, r2=0.9273, s=0.155, F=395; Test set: n=35, r2=0.8782, s=0.259, F=238; All structures: n=68, r2=0.8855, s=0.213, F=511. [Copyright &y& Elsevier]

Molecular graph descriptors are used, together with a large diversity of geometric, electrostatic, and quantum indices, to model physical, chemical, or biological properties with quantitative structure–property relationships and quantitative structure–activity relationships. The interest of developing new graph descriptors for organic compounds was stimulated in recent years by their use in virtual screening of combinatorial libraries, database mining, similarity and diversity assessment. Recently, we have extended topological indices by defining a series of molecular graph operators, providing an effective systematization and generalization of these structural descriptors. A graph operator uses a mathematical equation to compute a family of related molecular graph descriptors with different molecular matrices and various sets of parameters for atoms and bonds. In this paper we use structural descriptors computed with molecular graph operators to develop quantitative structure–activity relationships (QSAR) models for the dihydrofolate reductase inhibition with diaminopyrimidines. The molecular descriptors are derived from five molecular matrices, namely adjacency A, distance D, reciprocal distance RD, distance-path Dp, and reciprocal distance-path RDp. The QSAR models are obtained by selecting descriptors with a genetic algorithm, and the best models are validated with the leave-one-out cross-validation method. The QSAR models with the highest prediction power are comparable with those obtained with substituent constants and neural networks, but they use a much lower number of parameters. [Copyright &y& Elsevier]

In this work, co-crystal screening was carried out for two important dihydrofolate reductase (DHFR) inhibitors, trimethoprim (TMP) and pyrimethamine (PMA), and for 2,4-diaminopyrimidine (DAP), which is the pharmacophore of these active pharmaceutical ingredients (API). The isomeric pyridinecarboxamides and two xanthines, theophylline (THEO) and caffeine (CAF), were used as co-formers in the same experimental conditions, in order to evaluate the potential for the pharmacophore to be used as a guide in the screening process. In silico co-crystal screening was carried out using BIOVIA COSMOquick and experimental screening was performed by mechanochemistry and supported by (solid + liquid) binary phase diagrams, infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). The in silico prediction of low propensities for DAP, TMP and PMA to co-crystallize with pyridinecarboxamides was confirmed: a successful outcome was only observed for DAP + nicotinamide. Successful synthesis of multicomponent solid forms was achieved for all three target molecules with theophylline, with DAP co-crystals revealing a greater variety of stoichiometries. The crystalline structures of a (1:2) TMP:THEO co-crystal and of a (1:2:1) DAP:THEO:ethyl acetate solvate were solved. This work demonstrated the possible use of the pharmacophore of DHFR inhibitors as a guide for co-crystal screening, recognizing some similar trends in the outcome of association in the solid state and in the molecular aggregation in the co-crystals, characterized by the same supramolecular synthons. [ABSTRACT FROM AUTHOR]

The pharmacokinetics of aditoprim, a new dihydrofolate reductase (DHFR) inhibitor, and trimethoprim (TMP) were studied in heifers following a single intravenous injection of a 10 mg/kg b.w. dose. Aditoprim had a larger volume of distribution at steady state (6.5 ± 0.61/kg) than TMP (1.1 ± 0.11/kg) and this probably reflects a better tissue penetration than TMP. Both antimicrobials had the same high plasma clearance (5.0 ± 1.0 l/min). Accordingly, aditoprim exhibited a longer half-life (4-6.7 h) than TMP which was 1.3 h, as reported by several authors. Moreover, the plasma concentrations of the new antimicrobial were higher than those of TMP, starting from 4 hours after the drug was injected. For these reasons, the duration of the in vivo bacteriostatic activity of aditoprim should be significantly longer than that of TMP. Aditoprim was also injected intravenously into heifers in combination with either sulphadimidine (SDM) or sulphamerazine (SMR) in a 5:1 w/w sulphonamide/aditoprim ratio. The dose was 15 mg of the combination/kg b. w. The pharmacokinetics of the two combinations showed no significant differences. The half-lives of SDM and SMR were both 4 hours, and the pharmacokinetic parameters of aditoprim did not differ significantly from those found when the drug was injected alone. Thus, the half-life of the new DHFR inhibitor appeared to be in the same range as that of the sulphonamides commonly used in veterinary medicine, while its antimicrobial activity was considerably higher. The use of aditoprim as a single drug could thus be envisaged as well as in combination with a sulphonamide. Zusammenfassung Pharmakokinetik von Aditoprim, einem lang wirkenden Dihydrofolatreduktase-Hemmer, bei Kalbinnen: Die Pharmakokinetik von Aditoprim, eines neuen Dihydrofolatreduktase(DHFR)-Hemmers, und von Trimethoprim (TMP) wurden im Anschluß an intravenöse Einzelinjektionen von 10 mg pro kg Körpergewicht an Färsen untersucht. Aditoprim hatte bei Fließgleichgewicht ein größeres Verteilungsvolumen (6,5 ± 0,6 l/kg) als TMP (1,1 ± 0,1 l/kg), was wahrscheinlich auf eine bessere Gewebepenetration gegenüber TMP hinweist. Beide antibakterielle Substanzen besaßen die gleiche, hohe Plasmaclearance (5,0 ± 1,0 l/min). Aditoprim zeigte eine entsprechend längere Halbwertzeit (4-6,7 h) als TMP, das gemäß verschiedenen Autoren eine HWZ von 1,3 h besitzt. Zudem führte das neue Präparat ab der vierten Stunde nach der Injektion zu höheren Plasmakonzentrationen als TMP. Aus diesen Gründen sollte die bakteriostatische Wirkung von Aditoprim in vivo signifikant länger anhalten als diejenige von TMP. Man injizierte außerdem Aditoprim in Kombination mit Sulfadimidin (SDM) oder Sulfamerazin (SMR) intravenös an Färsen, wobei das Gewichtsverhältnis Sulfonamid/Aditoprim 5:1 betrug. Die Kombination wurde in einer Dosis von 15 mg pro kg Körpergewicht verabreicht. Die Pharmakokinetik der beiden Kombinationen zeigte keine signifikanten Unterschiede. Die Halbwertzeit von SDM und SMR betrug je 4 Stunden, und die pharmakokinetischen Parameter von Aditoprim unterschieden sich hierbei nicht signifikant von denjenigen bei alleiniger Injektion des Präparats. Die Halbwertzeit des neuen DHFR-Hemmers scheint daher im gleichen Bereich zu liegen wie diejenige der in der Veterinärmedizin gängig verwendeten Sulfonamide, doch entfaltet er eine wesentlich höhere antibakterielle Aktivität als die letztgenannten Substanzen. Deshalb kann sowohl die Verabreichung von Aditoprim als Einzelpräparat als auch die Kombination mit einem Sulfonamid ins Auge gefaßt werden. [ABSTRACT FROM AUTHOR]

Antimicrobial agents are currently the mainstay of treatment for bacterial infections worldwide. However, due to the increased use of antimicrobials in both human and animal medicine, pathogens have now evolved to possess high levels of multi-drug resistance, leading to the persistence and spread of difficult-to-treat infections. Several current antibacterial agents active against Gram-positive bacteria will be rendered useless in the face of increasing resistance rates. There are several emerging antibiotics under development, some of which have been shown to be more effective with an improved safety profile than current treatment regimens against Gram-positive bacteria. We will extensively discuss these antibiotics under clinical development (phase I-III clinical trials) to combat Gram-positive bacteria, such as Staphylococcus aureus, Enterococcus faecium and Streptococcus pneumoniae. We will delve into the mechanism of actions, microbiological spectrum, and, where available, the pharmacokinetics, safety profile, and efficacy of these drugs, aiming to provide a comprehensive review to the involved stakeholders. [ABSTRACT FROM AUTHOR]

• Series of hydrophobic flexible 6-substituent PYR analogues were synthesized. • Compound 27 showed the best inhibition on QM- Pf DHFR with K i of 0.41 nM. • The binding mode of the compounds was shown by X-ray crystallographic analysis. • Hydrophobic substituent at 6-position accommodated well in the hydrophobic pocket. • Optimal length of linker promoted binding of carboxyl group to Arg59 and Arg122. The series of des -Cl (unsubstituted) and m -Cl phenyl analogues of PYR with various flexible 6-substituents were synthesized and studied for the binding affinities with highly resistant quadruple mutant (QM) DHFR. The derivatives carrying 4 atoms linker with a terminal carboxyl substituted on the aromatic ring exhibited good inhibition to the QM enzyme and also showed effective antimalarial activities against resistant P. falciparum bearing the mutant enzymes with relatively low cytotoxicity to mammalian cells. The X-ray crystallographic analysis of the enzyme-inhibitor complexes suggested that the hydrophobic substituent at 6-position was accommodated well in the hydrophobic pocket and the optimal length of the flexible linker could effectively promote the binding of the terminal carboxyl group to the key amino acid residues, Arg59 and Arg122. [ABSTRACT FROM AUTHOR]

Background Trimethoprim inhibits sodium channels in the distal portion of the renal tubule, thereby impairing renal potassium excretion. Trimethoprim has been associated with a greater risk of hyperkalemia compared with other antibiotics (amoxicillin, nitrofurantoin, cefalexin, ciprofloxacin). An analysis of Phase 3 studies was conducted to determine whether iclaprim, under development for ABSSSI and also a selective bacterial dihydrofolate reductase inhibitor like trimethoprim, is associated with hyperkalemia, relative to vancomycin, an antibiotic not associated with hyperkalemia. Methods A post-hoc safety analysis was conducted on pooled results of two Phase 3, double-blind, randomized (1:1), active-controlled trials (REVIVE-1/-2) in patients with ABSSSI. These trials compared iclaprim 80 mg fixed doses with vancomycin 15 mg/kg; both administered intravenously every 12 hours for 5–14 days. Hyperkalemia was defined as serum potassium (K) ≥5.5 mmol/L, if normal at baseline, while on study drug. Hyperkalemia was compared between treatment groups and stratified subgroup comparisons were performed. Results Demographics and baseline disease characteristics were similar between the pooled iclaprim and vancomycin groups (table). Hyperkalemia occurred during treatment in 1.5% (9/592) and 2.5% (15/599) of patients treated with iclaprim and vancomycin, respectively. Of the patients with hyperkalemia, one patient in each treatment group had moderate to severe renal impairment (creatinine clearance [CrCl] 15–59 mL/minute). Among patients with moderate to severe renal impairment on any RAS, KSD or K supplements, hyperkalemia occurred in 1/16 and 0/16 patients in the iclaprim and vancomycin groups, respectively, and in 2/83 and 0/46 patients with mild to no renal impairment. No patients with hyperkalemia experienced adverse events of palpitations, chest pain, myalgia, muscular weakness or fatigue. Conclusion No differences in hyperkalemia were seen between the iclaprim and vancomycin groups in the Phase 3 REVIVE studies. In general, few cases of hyperkalemia occurred among patients with renal impairment treated with concomitant angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers treated with iclaprim. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

The emergence of various drug-resistant Mycobacterium tuberculosis (Mtb) strains has necessitated the exploration of new drugs that lack cross-resistance with existing therapeutics. By screening the MedChemExpress bioactive compound library, ceritinib was identified as a compound with activity against Mtb H37Ra. Ceritinib had a MIC value of 9.0 μM in vitro and demonstrated in vivo efficacy in a BALB/c mouse model infected with autoluminescent H37Ra. Then, 32 novel ceritinib derivatives were synthesized, and their antimycobacterial activities were evaluated in vitro. The antimycobacterial activities of the synthesized compounds were drastically affected by substitutions at position 4 of the pyrimidine nucleus and were enhanced by the presence of 2-isopropoxy-5-methyl-4-(piperidin-4-yl)aniline at position 2 of the pyrimidine nucleus. The in vivo antitubercular activities of the three most potent compounds were evaluated. 5-Chloro-N 2 -(2-isopropoxy-5-methyl-4-(piperidin-4-yl) phenyl)-N 4 -(naph thalen-1-yl) pyrimidine-2,4-diamine (16j) remarkably reduced the Mtb burden of mice. This result suggested the potential of 16j as a novel drug with superior antitubercular activities. The results of experiments on the combination of sulfamethoxazole with 16j and in silico modeling suggest that dihydrofolate reductase is the potential molecular target of 16j., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Objectives/Background Dihydrofolate reductase (DHFR) is one of the validated drug targets in Mycobacterium tuberculosis (Mtb) infection. DHFR inhibitors have been used to treat various life-threatening diseases such as cancer, malaria, and several bacterial infections. However, all clinically effective DHFR inhibitors are non-selective, and inhibit both human and pathogenic DHFRs more or less to a similar extent. The crystal structure of various DHFRs complexed with nicotinamide adenine dinucleotide phosphate and different inhibitors is available in the protein data bank. The crystal structures are validated and have been used for new drug designing. M. tuberculosis DHFRs and human (h) DHFRs show 26% structure similarity, but their active sites are not identical and this characteristic forms the basis of this study. Because most of the reported inhibitors of M. tuberculosis DHFR are pteridine based and nonselective in nature, that is, they inhibit both microbial and host DHFRs, this study aimed to design and develop selective nonpteridine M. tuberculosis DHFR inhibitors. Method In the ternary complex of methotrexate with M. tuberculosis DHFR, whose structure is also available in the protein data bank, the side of the aminopterin ring is accessible to the solvent; additionally, a glycerol “A” molecule is found in a depression nearby. This glycerol molecule interacts with the side chains of Trp22, Asp27, and Gln28, which form a pocket in M. tuberculosis DHFR; by contrast, glycerol is absent in h-DHFR. In the h-DHFRs (complexed with folate or N-(4-carboxy-{-[(2, 4-diamino pteridine-6-yl methyl)-amino]-benzoyl amino} -butyl) pthalamic acid (COP)), the site is well packed with three hydrophobic residue side chains, Leu22, Pro26, and Phe31, which correspond to Leu20, Arg23, and Gln28, respectively, found in M. tuberculosis DHFR. Therefore, compounds with side chain, which could mimic the binding mode of glycerol to protein, may bind to M. tuberculosis DHFR selectively. Such a derivative should be sterically and chemically hindered from forming a complex with h-DHFR. This assumption forms the basis of this study and this understanding has been used for designing selective inhibitors of M. tuberculosis DHFR. Results A number of novel nonpteridine-based molecules have been identified after the virtual screening of three databases (MDPI, NCI and inhouse databases). The best molecules identified after screening the three databases have been synthesized and tested for antitubercular activity. The results are promising and require further work in this direction. Conclusion Structure based drug design can be used as an effective tool for the design of new cheiocal entity. Number of novel agents have been identified as antitubercular agents whose mechanism of action needs to be ascertained. [ABSTRACT FROM AUTHOR]

We previously reported a series of N 2 -disubstituted quinazoline-2,4-diamines as dihydrofolate reductase inhibitors with potent N 4 -disubstituted quinazoline-2,4-diamines as dihydrofolate reductase inhibitors with potent in vitro and in vivo antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) strains. In this work, we extended our previous study to the Gram-negative pathogen Acinetobacter baumannii We determined that optimized N 2 , N 4 -disubstituted quinazoline-2,4-diamines are strongly antibacterial against multidrug-resistant A. baumannii strains when the 6-position is replaced with a halide or an alkyl substituent. Such agents display potent antibacterial activity, with MICs as low as 0.5 μM, while proving to be strongly bactericidal. Interestingly, these compounds also possess the potential for antibiofilm activity, eradicating 90% of cells within a biofilm at or near MICs. Using serial passage assays, we observed a limited capacity for the development of resistance toward these molecules (4-fold increase in MIC) compared to existing folic acid synthesis inhibitors, such as trimethoprim (64-fold increase) and sulfamethoxazole (128-fold increase). We also identified limited toxicity toward human cells, with 50% lethal doses (LD 50 s) of ≤23 μM for lead agents 4 and 5. Finally, we demonstrated that our lead agents have excellent in vivo efficacy, with lead agent 5 proving more efficacious than tigecycline in a murine model of A. baumannii infection (90% survival versus 66%), despite being used at a lower dose (2 versus 30 mg kg -1 ). Together, our results demonstrate that N 2 , N 4 -disubstituted quinazoline-2,4-diamines have strong antimicrobial and antibiofilm activities against both Gram-positive organisms and Gram-negative pathogens, suggesting strong potential for their development as antibacterial agents., (Copyright © 2017 American Society for Microbiology.)