26 results on '"Alvarez-Sánchez R"'
Search Results
2. Nitrided FeB amorphous thin films for magneto mechanical systems
- Author
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Fernández-Martinez, I., Martín-González, M.S., González-Arrabal, R., Álvarez-Sánchez, R., Briones, F., and Costa-Krämer, J.L.
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- 2008
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3. Analytical model for shape anisotropy in thin-film nanostructured arrays: Interaction effects
- Author
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Álvarez-Sánchez, R., Costa-Krämer, J.L., and Briones, F.
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- 2006
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4. Use of the Distribution Coefficient in Brain Polar Lipids for the Assessment of Drug-Induced Phospholipidosis Risk.
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Ceccarelli, M., Wagner, B., Alvarez-Sánchez, R., Cruciani, G., and Goracci, L.
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- 2017
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5. Magnetism and Magneto Optics in Nanostructure Arrays.
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Costa-Krämer, J.L., Alvarez-Sánchez, R., Bengoechea, A., and Briones, F.
- Subjects
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MAGNETISM , *MAGNETOOPTICS , *NANOSTRUCTURES , *FERROMAGNETISM , *THIN films , *MAGNETIZATION - Abstract
Recent developments at the authors’ lab in the study of magnetic and magneto optical (MO) properties of nanostructure arrays are reviewed. The study focus on the effect on the magnetic and MO properties that patterning has in single layer ferromagnetic thin films, and thin films made of ferromagnetic insulator heterostructures. It is demonstrated the outmost importance of the magnetostatic coupling to describe the magnetization processes of the arrays, where fields and magnetization lay in plane. In single layer patterned arrays the magnetostatic coupling is responsible of the array behaving magnetically in a collective fashion below a certain threshold interelement separation distance. As expected, shining light on a periodic structure produces reflected and diffracted spots, and the significance of MO measurements in the diffracted beams is briefly addressed. For metal/insulator/metal array structures it is again the magnetostatic coupling, and the freedom of the magnetic flux to close now in the film growth direction, the determining factor in the measured magnetization processes. This produces and antiparallel alignment of the magnetizations of top and bottom electrode at zero field when the insulating barrier is thick enough to exchange decouple the electrodes. When the tunnel junction array is fabricated in such a way that instead of having physically separated junctions the junctions share the bottom electrode, the magnetostatic coupling is still the determining factor. This happens independently of the degree of overetching of the bottom electrode below the insulating tunnel barrier, and has allowed the fabrication of 1D and 2D periodic domain patterns in continuous flat ferromagnetic films. Fabricating this kind of structures (an array on top of a continuous film) on transparent substrates allows the MO measurements at either the patterned or the flat sides of the structures. At magnetic saturation the continuous film behaves as a mirror as expected, while at selected field values, where the periodic domain structure appears, it diffracts. This is a confirmation of a pure magneto optic diffraction due to a periodic domain structure. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]
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- 2005
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6. Pure Magnetooptic Diffraction and Kerr Microscopy of Periodic Domain Structures.
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J. L. Costa-Krämer, Bengoechea, A., Alvarez-Sánchez, R., and Briones, F.
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FERROMAGNETIC materials ,MAGNETIC domain ,THIN films ,FERROMAGNETISM ,MAGNETOOPTICS ,MAGNETIC films ,METALLIC films - Abstract
The fabrication of a periodic domain structure in a ferromagnetic thin film is reported. This periodic domain structure is formed in a thin continuous magnetic film by coupling it to a periodic array of magnetic elements grown on top. When the array and the continuous film are exchange decoupled, magnetostatic interactions produce in the continuous layer a domain structure replica of the topographic pattern at selected field values. The present work reports a direct confirmation of this periodic domain structure in the flat continuous film by Kerr microscopy, which is responsible for the pure magnetooptic diffraction. The effect on the magnetization processes of one- and two-dimensional structures with different periodicities and dimensions is studied in detail and compared with micromagnetic simulations, for Co and Fe films. [ABSTRACT FROM AUTHOR]
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- 2005
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7. Comprehensive Pharmacokinetic Evaluation of High Melanin Binder Levofloxacin in Rabbits Shows Potential of Topical Eye Drops for Posterior Segment Treatment.
- Author
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Bahrpeyma S, Jakubiak P, Alvarez-Sánchez R, Caruso A, Leuthardt M, Senn C, Del Amo EM, and Urtti A
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- Animals, Rabbits, Tandem Mass Spectrometry, Chromatography, Liquid, Posterior Eye Segment metabolism, Area Under Curve, Biological Availability, Tissue Distribution, Administration, Topical, Male, Levofloxacin pharmacokinetics, Levofloxacin administration & dosage, Ophthalmic Solutions pharmacokinetics, Melanins metabolism, Anti-Bacterial Agents pharmacokinetics, Anti-Bacterial Agents administration & dosage, Intravitreal Injections
- Abstract
Purpose: The purpose of this work was to understand the impact of melanin binding on ocular pharmacokinetics after administration of a high-binder model drug via different administration routes., Methods: We applied levofloxacin to pigmented and albino rabbits as eye drops (single and multiple), as well as by intravitreal and intravenous injections. Ocular tissues and plasma were analyzed for levofloxacin concentrations with liquid chromatography-mass spectrometry (LC-MS/MS), and pharmacokinetic parameters were calculated., Results: The data show enrichment of levofloxacin and weeks-long retention in pigmented tissues. Upon intravitreal injection, the area under the curve (AUC) values in pigmented tissues were about 9 to 15 times higher than the respective values in the albino rabbits, but this difference expanded to 255- to 951-fold following topical eye drop administration. Multiple dosing of eye drops led to substantial accumulation of levofloxacin in the pigmented tissues: AUC values were 3 to 12 times higher than after intravitreal injection. The AUCs were much lower after single topical or intravenous drug administrations. High drug levels (0.1-35 µM) were always observed in the neural retinas of pigmented eyes; the highest exposure was seen after intravitreal administration followed by multiple doses of topical drops. Single topical instillation and intravenous injections to the albino rabbits resulted in vitreal bioavailability values of 0.009% and 0.003%, respectively., Conclusions: Melanin binding can be used to achieve targeted drug delivery and extended retention in pigmented ocular tissues. The results from topical multiple dosing experiments suggest that eye drop treatment may yield drug exposures and responses comparable to intravitreal delivery, even in the retinal pigment epithelium and choroid.
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- 2024
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8. Ocular Pharmacokinetics of Intravitreally Injected Protein Therapeutics: Comparison among Standard-of-Care Formats.
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Jakubiak P, Alvarez-Sánchez R, Fueth M, Broders O, Kettenberger H, Stubenrauch K, and Caruso A
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- Angiogenesis Inhibitors administration & dosage, Angiogenesis Inhibitors chemistry, Animals, Antibodies, Monoclonal, Humanized administration & dosage, Antibodies, Monoclonal, Humanized chemistry, Antibodies, Monoclonal, Humanized pharmacokinetics, Half-Life, Intravitreal Injections, Macaca fascicularis, Models, Animal, Molecular Weight, Ranibizumab administration & dosage, Ranibizumab chemistry, Ranibizumab pharmacokinetics, Receptors, Vascular Endothelial Growth Factor administration & dosage, Receptors, Vascular Endothelial Growth Factor chemistry, Recombinant Fusion Proteins administration & dosage, Recombinant Fusion Proteins chemistry, Recombinant Fusion Proteins pharmacokinetics, Angiogenesis Inhibitors pharmacokinetics, Aqueous Humor metabolism, Vitreous Body metabolism
- Abstract
The current standard of care for antivascular endothelial growth factor (VEGF) treatment requires frequent intravitreal (IVT) injections of protein therapeutics, as a result of limited retention within the eye. A thorough understanding of the determinants of ocular pharmacokinetics (PK) and its translation across species is an essential prerequisite for developing more durable treatments. In this work, we studied the ocular PK in macaques of the protein formats that comprise today's anti-VEGF standard of care. Cynomolgus monkeys received a single IVT injection of a single-chain variable fragment (scFv, brolucizumab), antigen-binding fragment (Fab, ranibizumab), fragment crystallizable-fusion protein (Fc-fusion, aflibercept), or immunoglobulin G monoclonal antibody (IgG, VA2 CrossMAb). Drug concentrations were determined in aqueous humor samples collected up to 42 days postinjection using immunoassay methods. The ocular half-life ( t
1/2 ) was 2.28, 2.62, 3.13, and 3.26 days for scFv, Fab, Fc-fusion, and IgG, respectively. A correlation with human t1/2 values from the literature confirmed the translational significance of the cynomolgus monkey as an animal model for ocular research. The relation between ocular t1/2 and molecular size was also investigated. Size was inferred from the molecular weight (MW) or determined experimentally by dynamic light scattering. The MW and hydrodynamic radius were found to be good predictors for the ocular t1/2 of globular proteins. The analysis showed that molecular size is a determinant of ocular disposition and may be used in lieu of dedicated PK studies in animals.- Published
- 2021
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9. Understanding the Half-Life Extension of Intravitreally Administered Antibodies Binding to Ocular Albumin.
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Hauri S, Jakubiak P, Fueth M, Dengl S, Belli S, Alvarez-Sánchez R, and Caruso A
- Abstract
The burden associated with frequent injections of current intravitreal (IVT) therapeutics may be reduced by long-acting delivery strategies. Binding to serum albumin has been shown to extend the ocular half-life in rabbits, however, the underlying molecular mechanisms and translational relevance remain unclear. The aim of this work was to characterize the in vitro and in vivo formation of complexes between human serum albumin (HSA) and an antigen-binding fragment of a rabbit antibody linked to an anti-HSA nanobody (FabA). The ocular and systemic pharmacokinetics of
3 H-labeled FabA (0.05 mg/eye IVT) co-formulated with HSA (1 and 15 nmol/eye) were assessed in Dutch belted rabbits. Next, FabA was incubated in vitreous samples from cynomolgus monkeys and human donors (healthy and diseased) supplemented with species-specific serum albumin. Finally, the FabA-albumin complexes formed in vitro and in vivo were analyzed by radio-size exclusion chromatography. A 3-fold increase in FabA vitreal exposure and half-life was observed in rabbits co-administered with 15 nmol HSA compared to 1 nmol and a control arm. The different pharmacokinetic behavior was explained with the formation of higher molecular weight FabA-albumin complexes. The analysis of vitreous samples revealed the existence of predominantly 1:1 complexes at endogenous or low concentrations of supplemented albumin. A shift towards 1:2 complexes was observed with increasing albumin concentrations. Overall, these results suggest that endogenous vitreal albumin concentrations are insufficient for half-life extension and warrant supplementation in the dosing formulation.- Published
- 2020
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10. Ocular Half-Life of Intravitreal Biologics in Humans and Other Species: Meta-Analysis and Model-Based Prediction.
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Caruso A, Füth M, Alvarez-Sánchez R, Belli S, Diack C, Maass KF, Schwab D, Kettenberger H, and Mazer NA
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- Animals, Antibodies, Monoclonal, Humanized pharmacokinetics, Biological Products pharmacokinetics, Diffusion, Half-Life, Haplorhini, Humans, Hydrodynamics, Rabbits, Rats, Recombinant Fusion Proteins pharmacokinetics, Retinal Diseases drug therapy, Swine, Tissue Distribution, Vitreous Body drug effects, Vitreous Body metabolism, Antibodies, Monoclonal, Humanized administration & dosage, Biological Products administration & dosage, Immunoglobulin Fab Fragments administration & dosage, Immunoglobulin G administration & dosage, Intravitreal Injections methods, Receptors, Vascular Endothelial Growth Factor administration & dosage, Recombinant Fusion Proteins administration & dosage
- Abstract
Therapeutic antibodies administered intravitreally are the current standard of care to treat retinal diseases. The ocular half-life ( t
1/2 ) is a key determinant of the duration of target suppression. To support the development of novel, longer-acting drugs, a reliable determination of t1/2 is needed together with an improved understanding of the factors that influence it. A model-based meta-analysis was conducted in humans and nonclinical species (rat, rabbit, monkey, and pig) to determine consensus values for the ocular t1/2 of IgG antibodies and Fab fragments. Results from multiple literature and in-house pharmacokinetic studies are presented within a mechanistic framework that assumes diffusion-controlled drug elimination from the vitreous. Our analysis shows, both theoretically and experimentally, that the ocular t1/2 increases in direct proportion to the product of the hydrodynamic radius of the macromolecule (3.0 nm for Fab and 5.0 nm for IgG) and the square of the radius of the vitreous globe, which varies approximately 24-fold from the rat to the human. Interspecies differences in the proportionality factors are observed and discussed in mechanistic terms. In addition, mathematical formulae are presented that allow prediction of the ocular t1/2 for molecules of interest. The utility of these formulae is successfully demonstrated in case studies of aflibercept, brolucizumab, and PEGylated Fabs, where the predicted ocular t1/2 values are found to be in reasonable agreement with the experimental data available for these molecules.- Published
- 2020
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11. Establishment of an In Vitro-In Vivo Correlation for Melanin Binding and the Extension of the Ocular Half-Life of Small-Molecule Drugs.
- Author
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Jakubiak P, Cantrill C, Urtti A, and Alvarez-Sánchez R
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- ATP Binding Cassette Transporter, Subfamily B, Member 1 metabolism, Animals, Blood Proteins chemistry, Blood Proteins metabolism, Cell Line, Chromatography, Liquid, Half-Life, Humans, Kinetics, Melanins chemistry, Octanols chemistry, Protein Binding, Rats, Rats, Wistar, Tandem Mass Spectrometry, Eye metabolism, Melanins metabolism
- Abstract
A large variety of drugs bind effectively to melanin, and this binding influences their ocular pharmacokinetic and distribution profiles. We aimed to establish a correlation between in vitro melanin binding and in vivo ocular pharmacokinetics (PK). The extent of melanin binding in vitro was determined for a set of model drugs; binding kinetics and binding isotherms were generated and fitted to a mechanistic model to derive the drug-melanin binding parameters ( B
max , KD , kon , and koff ). In addition, in vitro ADME properties such as cellular permeability, P-glycoprotein-mediated efflux, plasma protein binding, and octanol partition coefficients were determined. Moreover, cellular uptake was measured in the nonpigmented ARPE-19 cells and in lightly pigmented human epidermal melanocytes. Finally, in vivo ocular PK studies were performed in albino and pigmented rats using intravenous injections. Substantial drug enrichment accompanied by a very long residence time was observed in pigmented ocular tissues, which could be linked to the melanin binding determined in vitro and to the intracellular drug uptake into the pigmented cells. The resulting ocular PK profile is shown to be a consequence of the interplay of melanin binding with concurrent processes such as systemic clearance, plasma protein binding, cellular permeation, P-glycoprotein efflux, pH partitioning, and tissue binding. Understanding this interplay at a mechanistic level could help in the rational design and development of new small-molecule drug candidates with the desired PK/pharmacodynamic profile to target the back of the eye.- Published
- 2019
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12. Influence of Melanin Characteristics on Drug Binding Properties.
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Jakubiak P, Lack F, Thun J, Urtti A, and Alvarez-Sánchez R
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- Animals, Models, Theoretical, Particle Size, Protein Binding, Swine, Melanins metabolism, Sepia metabolism
- Abstract
Melanins are biopolymers encompassing a high degree of chemical heterogeneity. Binding of small-molecule drugs to ocular melanin significantly affects the ocular pharmacokinetics, and could serve as a strategy for prolonged drug retention in the eye. The influence of the structural and physical characteristics of melanins originating from different sources on their drug binding properties has not yet been methodically investigated. We performed physical characterization of Sepia officinalis, synthetic and porcine melanin. The particle size distribution was analyzed by laser diffractometry. A dynamic vapor sorption method, requiring small amounts of the material, was developed to analyze the differences in the specific surface area of the melanins. The extent of melanin binding at equilibrium was determined for a set of 34 small-molecule drugs and compared across different melanin types. Despite systematic shifts in the extent of binding within a twofold range, binding data were highly correlated across the melanins. These moderate differences in binding could not be directly explained by the substantial differences in particle size and were more in line with the relatively similar specific surface area of these different melanin materials. Overall, these results suggest that the specific surface area reflects the actual accessibility of a small molecule in the melanin structure and could serve as a surrogate to explain the binding differences observed for the respective melanin materials.
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- 2019
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13. Understanding Molecular Drivers of Melanin Binding To Support Rational Design of Small Molecule Ophthalmic Drugs.
- Author
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Jakubiak P, Reutlinger M, Mattei P, Schuler F, Urtti A, and Alvarez-Sánchez R
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- Chemical Phenomena, Computer Simulation, Drug Evaluation, Preclinical, Ophthalmology, Small Molecule Libraries chemistry, Small Molecule Libraries pharmacology, Drug Design, Melanins metabolism, Small Molecule Libraries metabolism
- Abstract
Binding of drugs to ocular melanin is a prominent biological phenomenon that affects the local pharmacokinetics and pharmacodynamics in the eye. In this work, we report on the development of in vitro and in silico tools for an early assessment and prediction of melanin binding properties of small molecules. A robust high-throughput assay has been established to study the binding of large sets of compounds to melanin. The extremely randomized trees approach was used to develop an in silico model able to predict the extent of melanin binding from the molecular properties of the compounds. After the last iteration of the model, strong melanin binders could prospectively be identified with 91% accuracy. On the basis of in vitro data generated for approximately 3400 chemically diverse drug-like small molecules, pronounced correlations were observed between the extent of melanin binding and the basicity, lipophilicity, and aromaticity of the compounds.
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- 2018
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14. Extension of the dissolution-precipitation model for kinetic elucidation of solvent-mediated polymorphic transformations.
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Jakubiak P, Schuler F, and Alvarez-Sánchez R
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- Crystallization, Ethanol chemistry, Humans, Kinetics, Models, Theoretical, Ritonavir chemistry, Solubility, Temperature, Time Factors, Chemistry, Pharmaceutical methods, Drug Compounding methods, Solvents chemistry
- Abstract
Thorough understanding and control of the different crystal forms of a drug product is key for fine chemistry and materials science; it ultimately determines the product's physicochemical properties and performance. In this work, we extend the application of a mechanistic dissolution-precipitation model to solvent-mediated solid form transformations. To address the relevance of the model, various kinetic solvent-mediated polymorphic transition studies were retrieved from the literature. Our model succeeds in accurately describing the experimental data, shedding light on the molecular steps driving the polymorphic conversion. Given its simplicity and mechanistic character, the model can be viewed as a useful tool to monitor, predict and optimize the solvent-mediated transformations of solid forms., (Copyright © 2016 Elsevier B.V. All rights reserved.)
- Published
- 2016
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15. Development of a Unified Dissolution and Precipitation Model and Its Use for the Prediction of Oral Drug Absorption.
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Jakubiak P, Wagner B, Grimm HP, Petrig-Schaffland J, Schuler F, and Alvarez-Sánchez R
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- Administration, Oral, Computer Simulation, Erlotinib Hydrochloride administration & dosage, Humans, Kinetics, Tissue Distribution, Erlotinib Hydrochloride pharmacokinetics, Gastrointestinal Absorption drug effects, Models, Biological, Permeability drug effects
- Abstract
Drug absorption is a complex process involving dissolution and precipitation, along with other kinetic processes. The purpose of this work was to (1) establish an in vitro methodology to study dissolution and precipitation in early stages of drug development where low compound consumption and high throughput are necessary, (2) develop a mathematical model for a mechanistic explanation of generated in vitro dissolution and precipitation data, and (3) extrapolate in vitro data to in vivo situations using physiologically based models to predict oral drug absorption. Small-scale pH-shift studies were performed in biorelevant media to monitor the precipitation of a set of poorly soluble weak bases. After developing a dissolution-precipitation model from this data, it was integrated into a simplified, physiologically based absorption model to predict clinical pharmacokinetic profiles. The model helped explain the consequences of supersaturation behavior of compounds. The predicted human pharmacokinetic profiles closely aligned with the observed clinical data. In summary, we describe a novel approach combining experimental dissolution/precipitation methodology with a mechanistic model for the prediction of human drug absorption kinetics. The approach unifies the dissolution and precipitation theories and enables accurate predictions of in vivo oral absorption by means of physiologically based modeling.
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- 2016
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16. Estimation of Drug Binding to Brain Tissue: Methodology and in Vivo Application of a Distribution Assay in Brain Polar Lipids.
- Author
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Belli S, Assmus F, Wagner B, Honer M, Fischer H, Schuler F, and Alvarez-Sánchez R
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- ATP Binding Cassette Transporter, Subfamily B, Member 1 metabolism, Animals, Blood-Brain Barrier metabolism, Male, Mice, Mice, Inbred C57BL, Rats, Rats, Wistar, Biological Assay methods, Brain metabolism, Central Nervous System Agents metabolism, Lipids physiology
- Abstract
The unbound drug concentration-effect relationship in brain is a key aspect in CNS drug discovery and development. In this work, we describe an in vitro high-throughput distribution assay between an aqueous buffer and a microemulsion of porcine brain polar lipids (BPL). The derived distribution coefficient LogDBPL was applied to the prediction of unbound drug concentrations in brain (Cu,b) and nonspecific binding to brain tissue. The in vivo relevance of the new assay was assessed for a large set of proprietary drug candidates and CNS drugs by (1) comparing observed compound concentrations in rat CSF with Cu,b calculated using the LogDBPL assay in combination with total drug brain concentrations, (2) comparing Cu,b derived from LogDBPL and total drug brain concentrations to Cu,b estimated using in vitro P-glycoprotein efflux ratio data and unbound drug plasma levels, and (3) comparing tissue nonspecific binding data from human brain autoradiography studies for 17 PET tracer candidates to distribution in BPL. In summary, the LogDBPL assay provides a predicted drug fraction unbound in brain tissue that is nearly identical to brain homogenate equilibrium dialysis with an estimation of in vivo Cu,b that is superior to LogD in octanol. LogDBPL complements the approach for predicting Cu,b based on in vitro P-glycoprotein efflux ratio and in vivo unbound plasma concentration and stands as a fast and cost-effective tool for nonspecific brain binding optimization of PET ligand candidates.
- Published
- 2015
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17. Importance of critical micellar concentration for the prediction of solubility enhancement in biorelevant media.
- Author
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Ottaviani G, Wendelspiess S, and Alvarez-Sánchez R
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- Biological Availability, Buffers, Chromatography, High Pressure Liquid, Fasting, Humans, Hydrogen-Ion Concentration, Intestinal Absorption, Intestinal Mucosa metabolism, Mass Spectrometry, Phosphates chemistry, Solubility, Spectrophotometry, Ultraviolet, Surface-Active Agents chemistry, Thermodynamics, Chemistry, Pharmaceutical methods, Micelles
- Abstract
This study evaluated if the intrinsic surface properties of compounds are related to the solubility enhancement (SE) typically observed in biorelevant media like fasted state simulated intestinal fluids (FaSSIF). The solubility of 51 chemically diverse compounds was measured in FaSSIF and in phosphate buffer and the surface activity parameters were determined. This study showed that the compound critical micellar concentration parameter (CMC) correlates strongly with the solubility enhancement (SE) observed in FaSSIF compared to phosphate buffer. Thus, the intrinsic capacity of molecules to form micelles is also a determinant for each compound's affinity to the micelles of biorelevant surfactants. CMC correlated better with SE than lipophilicity (logD), especially over the logD range typically covered by drugs (2 < logD < 4). CMC can become useful to guide drug discovery scientists to better diagnose, improve, and predict solubility in biorelevant media, thereby enhancing oral bioavailability of drug candidates.
- Published
- 2015
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18. Discovery and optimisation of 1-hydroxyimino-3,3-diphenylpropanes, a new class of orally active GPBAR1 (TGR5) agonists.
- Author
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Dehmlow H, Alvarez Sánchez R, Bachmann S, Bissantz C, Bliss F, Conde-Knape K, Graf M, Martin RE, Obst Sander U, Raab S, Richter HG, Sewing S, Sprecher U, Ullmer C, and Mattei P
- Subjects
- Administration, Oral, Animals, Inhibitory Concentration 50, Mice, Molecular Structure, Oximes chemistry, Oximes pharmacology, Propane blood, Propane chemical synthesis, Propane chemistry, Propane pharmacology, Blood Glucose drug effects, Drug Discovery, Oximes chemical synthesis, Propane analogs & derivatives, Receptors, G-Protein-Coupled agonists
- Abstract
A series of non-steroidal GPBAR1 (TGR5) agonists was developed from a hit in a high-throughput screening campaign. Lead identification efforts produced biphenyl-4-carboxylic acid derivative (R)-22, which displayed a robust secretion of PYY after oral administration in a degree that can be correlated with the unbound plasma concentration. Further optimisation work focusing on reduction of the lipophilicity provided the 1-phenylpiperidine-4-carboxylic acid derivative (R)-29 (RO5527239), which showed an improved secretion of PYY and GLP-1, translating into a significant reduction of postprandial blood glucose excursion in an oral glucose tolerance test in DIO mice., (Copyright © 2013 Elsevier Ltd. All rights reserved.)
- Published
- 2013
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19. PK/PD assessment in CNS drug discovery: Prediction of CSF concentration in rodents for P-glycoprotein substrates and application to in vivo potency estimation.
- Author
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Caruso A, Alvarez-Sánchez R, Hillebrecht A, Poirier A, Schuler F, Lavé T, Funk C, and Belli S
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- Animals, Blood Proteins metabolism, Central Nervous System Agents cerebrospinal fluid, Cluster Analysis, LLC-PK1 Cells, Mice, Models, Theoretical, Rats, Swine, ATP Binding Cassette Transporter, Subfamily B, Member 1 metabolism, Central Nervous System Agents pharmacokinetics, Central Nervous System Agents pharmacology, Drug Discovery
- Abstract
The unbound drug concentration in brain parenchyma is considered to be the relevant driver for interaction with central nervous system (CNS) biological targets. Drug levels in cerebrospinal fluid (C_CSF) are frequently used surrogates for the unbound concentrations in brain. For drugs actively transported across the blood-brain barrier (BBB), C_CSF differs from unbound plasma concentration (Cu_p) to an extent that is commonly unknown. In this study, the relationship between CSF-to-unbound plasma drug partitioning in rats and the mouse Pgp (Mdr1a) efflux ratio (ER) obtained from in vitro transcellular studies has been investigated for a set of 61 CNS compounds exhibiting substantial diversity in chemical structure and physico-chemical properties. In order to understand the in vitro-in vivo extrapolation of Pgp efflux, a mechanistic model was derived relating in vivo CNS distribution kinetics to in vitro active transport. The model was applied to predict C_CSF from Cu_p and ER data for 19 proprietary Roche CNS drug candidates. The calculated CSF concentrations were correlated with CNS pharmacodynamic responses observed in rodent models. The correlation between in vitro and in vivo potency for different pharmacological endpoints indicated that the predicted C_CSF is a valuable surrogate of the concentration at the target site. Overall, C_CSF proved superior description of PK/PD data than unbound plasma or total brain concentration for Mdr1a substrates. Predicted C_CSF can be used as a default approach to understand the PK/PD relationships in CNS efficacy models and can support the extrapolation of efficacious brain exposure for new drug candidates from rodent to man., (Copyright © 2013 Elsevier Inc. All rights reserved.)
- Published
- 2013
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20. 2-Phenoxy-nicotinamides are potent agonists at the bile acid receptor GPBAR1 (TGR5).
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Martin RE, Bissantz C, Gavelle O, Kuratli C, Dehmlow H, Richter HG, Obst Sander U, Erickson SD, Kim K, Pietranico-Cole SL, Alvarez-Sánchez R, and Ullmer C
- Subjects
- Binding Sites, Humans, Molecular Docking Simulation, Niacinamide metabolism, Protein Binding, Protein Structure, Tertiary, Quinolines chemistry, Receptors, G-Protein-Coupled metabolism, Structure-Activity Relationship, Niacinamide chemistry, Receptors, G-Protein-Coupled agonists
- Abstract
Potency with potential: 2-Phenoxy-nicotinamides were identified as potent agonists at the GPBAR1 receptor, a target in the treatment of obesity, type 2 diabetes and metabolic syndrome. Extensive structure-activity relationship studies supported by homology modeling and docking resulted in the identification of optimized GPBAR1 agonists, potent against both human and mouse receptors, endowed with favorable physicochemical properties and good metabolic stability., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2013
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21. Orally active aminopyridines as inhibitors of tetrameric fructose-1,6-bisphosphatase.
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Hebeisen P, Haap W, Kuhn B, Mohr P, Wessel HP, Zutter U, Kirchner S, Ruf A, Benz J, Joseph C, Alvarez-Sánchez R, Gubler M, Schott B, Benardeau A, Tozzo E, and Kitas E
- Subjects
- Administration, Oral, Allosteric Site, Aminopyridines chemistry, Animals, Crystallography, X-Ray, Diabetes Mellitus, Type 2, Disease Models, Animal, Enzyme Inhibitors chemistry, Fructose-Bisphosphatase chemistry, Fructose-Bisphosphatase metabolism, Humans, Inhibitory Concentration 50, Liver enzymology, Mice, Molecular Structure, Aminopyridines pharmacology, Enzyme Activation drug effects, Enzyme Inhibitors pharmacology, Fructose-Bisphosphatase antagonists & inhibitors
- Abstract
A novel sulfonylureido pyridine series exemplified by compound 19 yielded potent inhibitors of FBPase showing significant glucose reduction and modest glycogen lowering in the acute db/db mouse model for Type-2 diabetes. Our inhibitors occupy the allosteric binding site and also extend into the dyad interface region of tetrameric FBPase., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2011
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22. Benzoxazole piperidines as selective and potent somatostatin receptor subtype 5 antagonists.
- Author
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Martin RE, Mohr P, Maerki HP, Guba W, Kuratli C, Gavelle O, Binggeli A, Bendels S, Alvarez-Sánchez R, Alker A, Polonchuk L, and Christ AD
- Subjects
- Animals, Benzoxazoles chemical synthesis, Benzoxazoles pharmacokinetics, Crystallography, X-Ray, Male, Molecular Conformation, Piperidines chemical synthesis, Piperidines pharmacokinetics, Rats, Rats, Wistar, Receptors, Somatostatin metabolism, Structure-Activity Relationship, Benzoxazoles chemistry, Piperidines chemistry, Receptors, Somatostatin antagonists & inhibitors
- Abstract
SAR studies of a recently described SST5R selective benzoxazole piperidine lead series are described with particular focus on the substitution pattern on the benzyl and benzoxazole side-chains. Introduction of a second meta substituent at the benzyl unit significantly lowers residual hH1 activity and insertion of substituents onto the benzoxazole periphery entirely removes remaining h5-HT2B activity. Compounds with single digit nM activity, functional antagonism and favorable physicochemical properties endowed with a good pharmacokinetic profile in rats are described which should become valuable tools for exploring the pharmacological role of the SST5 receptor in vivo.
- Published
- 2009
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23. Glutathione conjugates of 4-hydroxy-2(E)-nonenal as biomarkers of hepatic oxidative stress-induced lipid peroxidation in rats.
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Völkel W, Alvarez-Sánchez R, Weick I, Mally A, Dekant W, and Pähler A
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- Acetylcysteine metabolism, Aldehydes chemistry, Animals, Free Radicals metabolism, Glutathione metabolism, Hepatocytes cytology, Hepatocytes metabolism, Lipid Peroxidation, Male, Models, Chemical, Rats, Rats, Inbred F344, Sensitivity and Specificity, Spectrometry, Mass, Electrospray Ionization, Time Factors, Aldehydes metabolism, Biomarkers metabolism, Glutathione chemistry, Liver metabolism, Oxidative Stress
- Abstract
Here we present a simple, specific, and sensitive liquid chromatography/mass spectrometry method to measure 4-hydroxy-2(E)-nonenal-glutathione (HNE-GSH), the major stable hepatic metabolite of HNE after GSH conjugation, as a marker of oxidative stress in rat liver and hepatocytes. Commonly employed methods for the measurement of lipid peroxidation-derived free aldehydes or modified proteins suffer from the artificial formation of HNE or HNE adducts to cellular molecules during sample preparation and derivatization, resulting in an overestimation of background levels. Basal levels of HNE-GSH in liver tissue from untreated rats were detected in amounts of 20 pmol/g liver. Rats exposed to a single dose of iron nitrilotriacetate (Fe(III)NTA; 15 mg Fe/kg bw, ip), a model compound for the induction of oxidative stress, revealed a fivefold increase in the hepatic HNE-GSH levels compared to controls 5 h after dosing. Moreover, a significant increase in HNE-mercapturic acid (HNE-MA) and its reduced metabolite DHN-MA was evident at 5 or 24 h after treatment, which was also reflected in increased plasma concentrations of these secondary HNE-GSH metabolites. In agreement with the in vivo data, a time-dependent increase in the levels of HNE-GSH from <1 to 123 +/- 16 pmol/10(6) cells over 5 h was detected in rat hepatocytes treated with Fe(III)NTA (150 microM). An increase in cellular HNE-GSH from <1.0 to 7.2 +/- 0.3 pmol/10(6) cells could be observed in rat hepatocytes treated with allyl alcohol (500 microM, 3 h), known for generation of HNE in hepatocytes. These data suggest that the direct measurement of the stable GSH conjugation product of cellular HNE in rat primary hepatocytes or its secondary metabolites may represent a reliable biomarker of oxidative stress-induced lipid peroxidation in rat liver in vivo.
- Published
- 2005
- Full Text
- View/download PDF
24. Effect of glutathione on the covalent binding of the 13C-labeled skin sensitizer 5-chloro-2-methylisothiazol-3-one to human serum albumin: identification of adducts by nuclear magnetic resonance, matrix-assisted laser desorption/ionization mass spectrometry, and nanoelectrospray tandem mass spectrometry.
- Author
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Alvarez-Sánchez R, Divkovic M, Basketter D, Pease C, Panico M, Dell A, Morris H, and Lepoittevin JP
- Subjects
- Binding Sites drug effects, Carbon Isotopes, Chemistry Techniques, Analytical methods, DNA Adducts drug effects, Glutathione chemistry, Histidine chemistry, Histidine metabolism, Humans, In Vitro Techniques, Lysine chemistry, Lysine metabolism, Magnetic Resonance Spectroscopy, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Glutathione pharmacology, Serum Albumin metabolism, Thiazoles isolation & purification, Thiazoles metabolism
- Abstract
The covalent binding of 4-[(13)C]- and 5-[(13)C]-5-chloro-2-methylisothiazol-3-one (MCI) toward human serum albumin (HSA) was followed by (13)C and (1)H[(13)C] NMR spectroscopy. MCI was found to react with histidine through an addition-elimination at position 5, leading to stable substitution adducts, and with lysine to form open adducts of the thioamide or amide type. No other modification could be detected on either cysteine or tyrosine. In the presence of glutathione (GSH), we observed an increased covalent binding to lysine residues. This could be explained by the rapid reaction of GSH with MCI to form a chlorothioacyl intermediate very reactive toward primary amino groups of lysine residues. To further confirm these observations and map covalent binding sites, HSA samples modified by MCI with or without GSH were analyzed by matrix-assisted laser desorption/ionization mass spectrometry of tryptic digests and electrospray tandem mass spectrometry of modified peptides purified by reverse phase HPLC. About 80% of the HSA sequence was mapped, and several modified peptides were identified. When HSA was incubated with MCI without GSH, three peptides modified at histidine residues were characterized while when HSA was incubated in the presence of GSH, five peptides modified at histidine and lysine residues were identified. These experiments confirmed that modifications on lysine residues were of the amide and thioamide types. Observed modifications were in accordance with mass increases corresponding to structures identified by NMR, and an extra adduct corresponding to a double modification of His 338 was observed. Comparison of HSA-MCI and HSA-MCI-GSH samples confirmed that the presence of GSH increased the modification of lysine residues.
- Published
- 2004
- Full Text
- View/download PDF
25. Covalent binding of the 13C-labeled skin sensitizers 5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI) to a model peptide and glutathione.
- Author
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Alvarez-Sánchez R, Basketter D, Pease C, and Lepoittevin JP
- Subjects
- Binding Sites physiology, Carbon Isotopes, Glutathione chemistry, Peptides chemistry, Peptides metabolism, Thiazoles chemistry, Dermatitis, Allergic Contact metabolism, Glutathione metabolism, Thiazoles metabolism
- Abstract
The reactivity of 4-[13C]- and 5-[13C]-5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI) towards a model peptide and glutathione was followed by 13C and 1H[13C] NMR spectroscopy. Both molecules were found to react with GSH but in addition MCI was found to react with histidine and lysine to form adducts of a different nature. Reaction with histidine led to stable substitution adducts through an addition-elimination reaction at position 5 while reaction with lysine led to the formation of open adducts of the thioamide or amide type.
- Published
- 2004
- Full Text
- View/download PDF
26. Studies of chemical selectivity of hapten, reactivity, and skin sensitization potency. 3. Synthesis and studies on the reactivity toward model nucleophiles of the 13C-labeled skin sensitizers, 5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI).
- Author
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Alvarez-Sánchez R, Basketter D, Pease C, and Lepoittevin JP
- Subjects
- Carbon Isotopes, Magnetic Resonance Spectroscopy methods, Skin, Haptens chemistry, Thiazoles chemical synthesis
- Abstract
The skin sensitizers, 5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI), have been synthesized isotopically labeled with (13)C at all carbon positions. The reactivity of 3-[(13)C]-, 4-[(13)C]-, and 5-[(13)C]MCI and MI toward a series of model nucleophiles for protein amino acid residues, i.e., butylamine, imidazole, sodium propanethiolate, and sodium phenoxide, was followed by (13)C and (1)H[(13)C] NMR spectroscopy. While MCI was found to react quantitatively with sodium propanethiolate and butylamine and significantly with imidazole and sodium phenoxide, MI reacted only with sodium propanethiolate. Reaction of MCI with nonthiol nucleophiles proceeded through an initial addition-elimination at position 5, leading to stable substitution adducts in the case of imidazole and sodium phenoxide. In the case of butylamine, the initial adduct was subjected to extra reactions at the sulfur atom through a cleavage of the S-N bond, leading to open adducts of the thioamide or amide type. Experiments carried out with N-acetyl-Cys, in excess or in deficiency, indicated that thiol nucleophiles reacted first at the sulfur atom through a cleavage of the S-N bond followed by extra nucleophilic reactions leading to open adducts of the mercaptothioester or mercaptoester type. Reaction of MCI with thiol nucleophiles gave products consistent with the formation of a reactive thioacyl chloride intermediate able to react with other nucleophiles present in the reaction medium. As a consequence, N-acetyl-Cys was found to be able to activate MCI toward N(alpha)-acetyl-Lys under physiological conditions to form adducts of the thioamide or amide type. Thus MCI, a strong sensitizer, and MI, a weak sensitizer, were found to react with different nucleophiles through different mechanisms. Although both MCI and MI can react with thiol nucleophiles, only MCI is capable of significantly reacting with amino nucleophiles of the Lys or His type. Moreover, MCI could be activated by a prior reaction with thiols.
- Published
- 2003
- Full Text
- View/download PDF
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