Effect of the Intramolecular Hydrogen Bond on the Active Metabolite Analogs of Leflunomide for Blocking the Plasmodium falciparum Dihydroorotate Dehydrogenase Enzyme: QTAIM, NBO, and Docking Study.

BACKGROUND: Leflunomide (LFM) and its active metabolite, teriflunomide (TFM), have drawn a lot of attention for their anticancer activities, treatment of rheumatoid arthritis and malaria due to their capability to inhibit dihydroorotate dehydrogenase (DHODH) and Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) enzyme. In this investigation, the strength of intramolecular hydrogen bond (IHB) in five analogs of TFM (ATFM) was analyzed employing density functional theory (DFT) using B3LYP/6-311++G (d, p) level and molecular orbital analysis in the gas phase and water solution. A detailed electronic structure study was performed using the quantum theory of atoms in molecules (QTAIM) and the hydrogen bond energies (EHB) of stable conformer obtained in the range of 76-97 kJ/mol, as a medium hydrogen bond. The effect of substitution on the IHB nature was studied by natural bond orbital analysis (NBO). 1H NMR calculations showed an upward trend in the proton chemical shift of the enolic proton in the chelated ring (14.5 to 15.7ppm) by increasing the IHB strength. All the calculations confirmed the strongest IHB in 5-F-ATFM and the weakest IHB in 2-FATFM. Molecular orbital analysis, including the HOMO-LUMO gap and chemical hardness, was performed to compare the reactivity of inhibitors. Finally, molecular docking analysis was carried out to identify the potency of inhibition of these compounds against PfDHODH enzyme. TFM acts as an inhibitor of dihydroorotate dehydrogenase (DHODH) and Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) enzyme. Leflunomide and its active metabolite teriflunomide have been identified as drugs for treatment of some diseases, such as multiple sclerosis (MS), rheumatoid arthritis (RA), malaria, and cancer. Hydrogen bonds play a key role in the interaction between drugs and enzymes. OBJECTIVES: The aim of the present work is to investigate the effect of the strength of intramolecular hydrogen bonds (IHBs) in the active metabolite analogs of leflunomide or analogs of teriflunomide (ATFMs) and study the interaction of these inhibitors against the PfDHODH enzyme using quantum mechanical methods. METHODS: At first, intramolecular hydrogen bonds in five ATFMs were evaluated by the DFT method, quantum theory of atoms in molecules (QTAIM), nuclear magnetic resonance (NMR), natural bond orbital (NBO), and molecular orbital (MO) analyses. Then, the interaction of these inhibitors against the PfDHODH enzyme were compared using molecular docking study. RESULTS: All the computed results confirm the following trend in the intramolecular hydrogen bond strength in five mono-halo-substituted 2-cyano-3-hydroxy-N-phenylbut-2-enamide (ATFM): 5-FATFM> 4-Br-ATFM ≈ 3-Br-ATFM>3-Cl-ATFM>TFM-Z>2-F-ATFM which is in agreement with QTAIM, NMR, and NBO results. Docking results show that 5-F-ATFM (EHB=97kJ/mol) has the minimum MolDock score due to its considerable IHB strength. CONCLUSION: For strong IHBs (EHB>100kJ/mol), C=O and O-H group are involved in the intramolecular interactions and do not contribute to the external interactions. Also, the docking study revealed maximum binding energy between TFM-Z and PfDHODH enzyme.

Selective Binding of Cyclodextrins with Leflunomide and Its Pharmacologically Active Metabolite Teriflunomide.

The selectivity of encapsulation of leflunomide and teriflunomide by native α-, ß- and γ-cyclodextrins was investigated through 1H NMR and molecular modeling. Thermodynamic analysis revealed the main driving forces involved in the binding. For α-cyclodextrin, the partial encapsulation was obtained while deep penetration was characterized for the other two cyclodextrins, where the remaining polar fragment of the molecule is located outside the macrocyclic cavity. The interactions via hydrogen bonding are responsible for high negative enthalpy and entropy changes accompanying the complexation of cyclodextrins with teriflunomide. These results were in agreement with the molecular modeling calculations, which provide a clearer picture of the involved interactions at the atomic level.

Pharmacodynamic assessment of ex-vivo canine T-lymphocyte proliferation: Responses to dexamethasone, cyclosporine, mycophenolic acid, and the active metabolite of leflunomide.

A lack of understanding of specific immune defects underlying canine immune-mediated diseases hampers optimal therapy. Failure to tailor treatment to an individual's immune abnormality can result in lack of efficacy, secondary complications, added expense, and drug-potentiated adverse effects. We adopted a small-volume whole-blood flow cytometric assay to determine the effect of immunosuppressant drugs on T-lymphocyte proliferation. Using healthy dogs in this proof-of-principle study, we hypothesized that there would be dose-dependent suppression of T-lymphocyte proliferation in response to dexamethasone, cyclosporine, mycophenolic acid, and the active metabolite of leflunomide (A77 1726). Whole blood was collected from 6 healthy pet dogs and incubated for 4 d with or without the mitogens concanavalin A and lipopolysaccharide and with increasing concentrations of immunosuppressant. Samples were subsequently stained with viability dye and with antibodies against the pan-T-lymphocyte marker CD5 and the cell proliferation marker Ki67. Percentages of proliferating T-lymphocytes were determined by flow cytometry, and the 50% inhibitory concentration (IC50) was calculated. Inhibition of T-lymphocyte proliferation by the panel of immunosuppressants was shown to be dose-dependent, with marked variability among the dogs. The mean IC50 was 394.8 ± 871 (standard deviation) µM for dexamethasone, 18.89 ± 36.2 ng/mL for cyclosporine, 106.3 ± 157.7 nM for mycophenolic acid, and 3.746 ± 6.8 µM for A77 1726. These results support the use of this assay for detecting the efficacy of individual immunosuppressants used to diminish T-lymphocyte proliferation. In future, the assay may be applied to pet dogs with spontaneous immune-mediated disease to help tailor individual treatment.

Un manque de compréhension des défauts immunitaires spécifiques sous-jacents aux maladies à médiation immunitaire canines nuit à une thérapie optimale. L'incapacité à concevoir un traitement approprié à l'anomalie immunitaire d'un individu peut résulter en une perte d'efficacité, des complications secondaires, une dépense supplémentaire, et des effets secondaires indésirables induits par les médicaments. Nous avons adopté un essai de cytométrie en flux sur un petit volume de sang entier afin de déterminer l'effet de médicaments immunosuppresseurs sur la prolifération de lymphocytes-T. En utilisant des chiens en santé dans cette étude de preuve de principe, nous avons émis l'hypothèse qu'il y aurait une suppression dose-dépendante de la prolifération des lymphocytes-T en réponse à la dexaméthasone, à la cyclosporine, à l'acide mycophénolique, et au métabolite actif du leflunomide (A77 1726). Du sang entier fut prélevé de six chiens en santé et incubé pendant 4 j avec et sans les agents mitogènes concanavaline A et lipopolysaccharide et avec des concentrations croissantes d'immunosuppresseurs. Les échantillons étaient par la suite colorés avec des colorants de viabilité et des anticorps contre le marqueur pan-lymphocyte-T CD5 et le marqueur de prolifération cellulaire Ki67. Les pourcentages de lymphocytes-T proliférant étaient déterminés par cytométrie en flux, et la concentration inhibitrice 50 % (IC50) fut calculée. L'inhibition de la prolifération de lymphocytes-T par la panoplie d'immunosuppresseurs a été démontrée comme étant dose-dépendante, avec une variabilité marquée parmi les chiens. L'IC50 moyenne était 394,8 ± 871 (écart-type) µM pour la dexaméthasone, 18,89 ± 36,2 ng/mL pour la cyclosporine, 106,3 ± 157,7 nm pour l'acide mycophénolique, et 3,746 ± 6,8 µM pour le A77 1726. Ces résultats appuient l'utilisation de cet essai pour détecter l'efficacité d'immunosuppresseurs individuels utilisés pour diminuer la prolifération de lymphocytes-T. Dans le futur, cet essai pourrait être utilisé chez des chiens de compagnie avec des maladies à médiation immunitaire spontanées afin d'aider à concevoir des traitements individuels.(Traduit par Docteur Serge Messier).

Encapsulation of Leflunomide (LFD) in a novel niosomal formulation facilitated its delivery to THP-1 monocytic cells and enhanced Aryl hydrocarbon receptor (AhR) nuclear translocation and activation.

BACKGROUND: Leflunomide (LFD) is an Aryl hydrocarbon receptor (AhR) agonist and immunomodulatory drug with several side effects. Niosomes are novel drug delivery systems used to reduce the unfavorable effects of drugs by enhancing their bioavailability, controlling their release and targeting specific sites. OBJECTIVES: Here, we prepared niosomal formulations of LFD, evaluated their properties and delivered to THP-1 monocytic cells to study the activation and nuclear translocation of AhR. METHODS: Four types of non-ionic surfactants were utilized to formulate niosomes by thin film hydration (TFH) method. Entrapment efficiency (EE %) of niosomes were quantified and dynamic light scattering (DLS) was performed. Transmission electron microscopy (TEM) was used to identify the morphology of LFD niosomes. Dialysis method was used to measure LFD release rate. MTS assay was adopted to examine the viability of the cells upon each treatment. The nuclear transfer of AhR was investigated by Immunocytochemistry (ICC). The mRNA expression of IL1ß and CYP1A1 were evaluated using quantitative RT-PCR. RESULTS: Span 60: cholesterol (1:1) showed the highest EE% (70.00 ± 6.24), largest particles (419.00 ± 4.16 nm) and the best uniformity with the lowest PDI (0.291 ± 0.007). TEM micrographs of Span 60 (1:1) nanoparticles showed conventional spherical vesicles with internal aqueous spaces. The release rate of LFD from Span 60 (1:1) vesicles was slower. Although the viability of LFD niosome-treated THP-1 cells was decreased, they were associated with lower cytotoxic effects compared with the free LFD counterparts. Both free and niosomal LFD treatments intensified the nuclear translocation of AhR. The mRNA expression of CYP1A1 was overexpressed while IL1ß was downregulated in both free and niosomal LFD treated combinations. CONCLUSION: LFD encapsulation in Span 60: cholesterol (1:1) niosomal formulation could be introduced as a suitable vehicle of transferring LFD to THP-1 cells, with minimal cytotoxic effects, enhancing the AhR nuclear translocation and activation and inducing immunomodulatory properties. Graphical abstract The Graphical abstract; it demonstrates the workflow of the study and summary of results in brief.

Coated nanostructured lipid carriers targeting the joints - An effective and safe approach for the oral management of rheumatoid arthritis.

Oral treatment of rheumatoid arthritis (RA) with the immunomodulator, leflunomide (LEF), is associated with systemic side effects namely immunosuppression and hepatotoxicity. Herein, attempts to improve LEF therapeutic outcomes via nanostructured lipid carriers (NLCs) targeting inflamed rheumatic joints were executed. LEF-NLCs coated with either chondroitin sulphate (CHS) or chitosan (CS) were around 250 nm in size with negative or positive charge, respectively. Particle coating was evidenced by TEM and FTIR analysis. NLCs generally ensured sustained release profile up to 21 days, particularly extended in coated formulations. In vivo pharmacokinetic study of LEF suspension, uncoated NLCs, CHS- and CS-coated NLCs was carried out. Following oral administration in RA-induced rat model, joint diameter, paw inflammation, liver functions were measured, in addition to histological examination of liver, kidney and joints. Results revealed improved joint healing and reduced hepatotoxicity following treatment with nanoencapsulated LEF compared to LEF suspension, whereby CHS-NLCs ensued the highest Cmax, AUC and lowest TNF-α level. The dual potential of CHS to achieve active targeting to CD44-receptor and hence maximize LEF concentration at the target site in addition to its synergistic effect in joint healing endow promises for a competent oral nanosystem for targeted drug delivery to the joints.

γ-Cyclodextrin-metal organic frameworks as efficient microcontainers for encapsulation of leflunomide and acceleration of its transformation into teriflunomide.

γ-Cyclodextrin-based metal-organic framework (γCD-MOF) crystals were successfully synthesized using a vapor diffusion method. An applicability of γCD-MOF for encapsulation of immunosuppressive disease-modifying antirheumatic drug leflunomide (LEF) was examined. Loading of LEF in γCD-MOF was performed by impregnation and co-crystallization. The empty and loaded γCD-MOFs were characterized using X-ray powder diffraction, N2 adsorption/desorption, thermogravimetric analysis, 1H NMR and FTIR spectroscopy. It was shown that in the presence of γCD-MOF leflunomide is transformed into its pharmacologically active form - teriflunomide that can be also applied alone in the treatment of multiple sclerosis. It was demonstrated that teriflunomide released from γCD-MOF has improved pharmacologically relevant properties such as solubility, dissolution rate and membrane permeability. It can be proposed that γCD-MOF can be considered as novel strategy for delivery of leflunomide.

LC-MS/MS Method for the Quantification of the Leflunomide Metabolite, Teriflunomide, in Human Serum/Plasma.

Leflunomide is a prodrug that is metabolized to the active metabolite, teriflunomide (A77 1726), to inhibit the enzyme dihydroorotate dehydrogenase and decrease the synthesis of pyrimidine nucleotides for DNA and RNA synthesis. Teriflunomide is primarily used for the treatment of rheumatoid arthritis and multiple sclerosis.A liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated to quantify the drug teriflunomide over a concentration range of 5 ng/mL-200 µg/mL in serum or plasma. The calibration curve was divided into two separate overlapping regions of the analytical measurement range, with a high curve and a low curve range. Samples are first analyzed using the high-range calibration curve after a 100-fold dilution of the sample extract. Samples falling below the upper curve region are evaluated again without dilution and quantified, if possible, against the low curve calibration standards. This method can be used to support therapeutic drug monitoring of patients that are administered with leflunomide therapy.

Development of a simple HPLC-MS/MS method to simultaneously determine teriflunomide and its metabolite in human plasma and urine: Application to clinical pharmacokinetic study of teriflunomide sodium and leflunomide.

A simple high-performance liquid chromatography coupled with tandem mass spectrometry method was developed and fully validated to simultaneously determine teriflunomide (TER) and its metabolite 4-trifluoro-methylaniline oxanilic acid (4-TMOA) in human plasma and urine. Merely 50 µL plasma and 20 µL urine were employed in sample preparation using protein precipitation and direct dilution method, respectively. An Agilent Zorbax eclipse plus C18 column was selected to achieve rapid separation for TER and 4-TMOA within 3 min. Electrospray ionization under multiple reaction monitoring was used to monitor the ion transitions for TER (m/z 269.0 → 159.9), 4-TMOA (m/z 231.9 → 160.0), internal standard teriflunomide-d4 (m/z 273.0 → 164.0) and 2-amino-4-trifluoromethyl benzoic acid (m/z 203.8 → 120.1), operating in the negative ion mode. This method proved to have better accuracy and precision over concentration range of 10-5000 ng/mL in plasma as well as 10-10,000 ng/mL in urine. After a full validation, this method was successfully applied in a pharmacokinetic study of teriflunomide sodium and leflunomide in Chinese healthy volunteers.

Efficient Encapsulation of Fluorinated Drugs in the Confined Space of Water-Dispersible Fluorous Supraparticles.

Fluorophobic-driven assemblies of gold nanomaterials were stabilized into water-dispersible fluorous supraparticles by the film-forming protein hydrophobin II. The strategy makes use of fluorous nanomaterials of different dimensions to engineer size and inner functionalization of the resulting confined space. The inner fluorous compartments allow efficient encapsulation and transport of high loadings of partially fluorinated drug molecules in water.