scholarly journals Mechanism-Based Pharmacokinetic-Pharmacodynamic Models of In Vitro Fungistatic and Fungicidal Effects against Candida albicans

2008 ◽  
Vol 52 (3) ◽  
pp. 937-943 ◽  
Author(s):  
Nicolas Venisse ◽  
Nicolas Grégoire ◽  
Manuella Marliat ◽  
William Couet
Keyword(s):  
Drug Effects ◽  
Compartment Model ◽  
In Vitro Models ◽  
Maximal Effect ◽  
Fungistatic Activity ◽  
Drug Concentrations ◽  
Elimination Half ◽  
Drug Pharmacokinetics ◽  
Over Time

ABSTRACT Mechanism-based pharmacokinetic-pharmacodynamic (PK-PD) models describing the fungistatic activity of fluconazole and the fungicidal activity of caspofungin were developed using dynamic in vitro models. Antifungal-drug pharmacokinetics was simulated in vitro, assuming a one-compartment model with an elimination half-life of 3 h and using a wide (1 to 10,000) range of initial concentrations. The number of CFUs over time was determined for up to 31 h and used for PK-PD modeling. A model incorporating first-order natural growth and natural death, plus a maximum number of viable Candida cells, was used to characterize Candida growth in the absence of a drug. Fluconazole was considered to inhibit Candida growth and caspofungin to stimulate Candida death according to an E max pharmacodynamic model. The data were analyzed with Nonmem, using a population approach. A good fit of the data was obtained with satisfactory estimates of PK-PD parameters, especially with drug concentrations producing 50% of the maximal effect: 50% inhibitory concentrations for fluconazole growth inhibition and 50% effective concentrations for caspofungin death stimulation. In conclusion, mechanistic PK-PD models were successfully developed to describe, respectively, the fungistatic and fungicidal activities of fluconazole and caspofungin in vitro. These models provide much better information on the drug effects over time than the traditional PK-PD index based on MICs. However, they need to be further characterized.

scholarly journals In Vitro Synergistic Interactions of Isavuconazole and Echinocandins against Candida auris

Antibiotics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 355
Author(s):  
Unai Caballero ◽  
Sarah Kim ◽  
Elena Eraso ◽  
Guillermo Quindós ◽  
Valvanera Vozmediano ◽  
...  
Keyword(s):  
Interaction Model ◽  
Antifungal Drugs ◽  
Health Concern ◽  
Candida Auris ◽  
Fungistatic Activity ◽  
Drug Concentrations ◽  
Low Concentrations ◽  
Wide Range ◽  
Time Kill

Candida auris is an emergent fungal pathogen that causes severe infectious outbreaks globally. The public health concern when dealing with this pathogen is mainly due to reduced susceptibility to current antifungal drugs. A valuable alternative to overcome this problem is to investigate the efficacy of combination therapy. The aim of this study was to determine the in vitro interactions of isavuconazole with echinocandins against C. auris. Interactions were determined using a checkerboard method, and absorbance data were analyzed with different approaches: the fractional inhibitory concentration index (FICI), Greco universal response surface approach, and Bliss interaction model. All models were in accordance and showed that combinations of isavuconazole with echinocandins resulted in an overall synergistic interaction. A wide range of concentrations within the therapeutic range were selected to perform time-kill curves. These confirmed that isavuconazole–echinocandin combinations were more effective than monotherapy regimens. Synergism and fungistatic activity were achieved with combinations that included isavuconazole in low concentrations (≥0.125 mg/L) and ≥1 mg/L of echinocandin. Time-kill curves revealed that once synergy was achieved, combinations of higher drug concentrations did not improve the antifungal activity. This work launches promising results regarding the combination of isavuconazole with echinocandins for the treatment of C. auris infections.

scholarly journals Endothelialized silicone aneurysm models for in vitro evaluation of flow diverters

2020 ◽  
pp. neurintsurg-2020-016859
Author(s):  
Alyssa McCulloch ◽  
Ashley Turcott ◽  
Gabriella Graham ◽  
Sergey Frenklakh ◽  
Kristen O'Halloran Cardinal
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Umbilical Vein ◽  
Flow Diverter ◽  
In Vitro Models ◽  
Cell Coverage ◽  
Platelet Endothelial Cell Adhesion ◽  
Umbilical Vein Endothelial Cells ◽  
Over Time

ObjectiveThe goal of this work was to endothelialize silicone aneurysm tubes for use as in vitro models for evaluating endothelial cell interactions with neurovascular devices. The first objective was to establish consistent and confluent endothelial cell linings and to evaluate the silicone vessels over time. The second objective was to use these silicone vessels for flow diverter implantation and assessment.MethodsSilicone aneurysm tubes were coated with fibronectin and placed into individual bioreactor systems. Human umbilical vein endothelial cells were deposited within tubes to create silicone vessels, then cultivated on a peristaltic pump and harvested at 2, 5, 7, or 10 days to evaluate the endothelial cell lining. A subset of silicone aneurysm vessels was used for flow diverter implantation, and evaluated for cell coverage over device struts at 3 or 7 days after deployment.ResultsSilicone vessels maintained confluent, PECAM-1 (platelet endothelial cell adhesion molecule 1) positive endothelial cell linings over time. These vessels facilitated and withstood flow diverter implantation, with robust cell linings disclosed after device deployment. Additionally, the endothelial cells responded to implanted devices through coverage of the flow diverter struts with increased cell coverage over the aneurysm seen at 7 days after deployment as compared with 3 days.ConclusionsSilicone aneurysm models can be endothelialized and successfully maintained in vitro over time. Furthermore, these silicone vessels can be used for flow diverter implantation and assessment.

scholarly journals Population Pharmacokinetic Modeling of VL-2397, a Novel Systemic Antifungal Agent: Analysis of a Single- and Multiple-Ascending-Dose Study in Healthy Subjects

2019 ◽  
Vol 63 (6) ◽  
Author(s):  
Laura L. Kovanda ◽  
Sean M. Sullivan ◽  
Larry R. Smith ◽  
Amit V. Desai ◽  
Pete L. Bonate ◽  
...  
Keyword(s):  
Antifungal Agent ◽  
Healthy Subjects ◽  
Phase 1 ◽  
Plasma Concentrations ◽  
Population Pharmacokinetic ◽  
Binding Model ◽  
Saturable Binding ◽  
Drug Concentrations ◽  
Over Time

ABSTRACT VL-2397, a novel, systemic antifungal agent, has potent in vitro and in vivo fungicidal activity against Aspergillus species. Plasma concentrations from a phase 1 study were used to construct a population pharmacokinetic (PPK) model for VL-2397. Healthy subjects aged 18 to 55 years received single doses of VL-2397, ranging from 3 to 1,200 mg, multiple daily doses of 300, 600, or 1,200 mg for 7 days, or 300 mg three times/day for 7 days followed by 600 mg daily for 21 days. Plasma samples were collected throughout the dosing intervals. Sixty-six subjects provided 1,908 concentrations. Drug concentrations over time were increased less than dose proportionally for doses above 30 mg. Dose-normalized concentrations plotted over time did not overlap. A 3-compartment nonlinear saturable binding model fit the data well. Clearance increased with dose, and mean values ranged from 0.4 liters/h at 3 mg to 8.5 liters/h at 1,200 mg. Mean volume in the central compartment ranged from 4.8 to 6.9 liters across doses. In the first 24 h, once-daily dosing results in a rapid decrease in concentrations by hour 16 to approximately 1 mg/liter, regardless of dose, with slow clearance over time. Administration of 300 mg every 8 h achieved concentrations above 1 mg/liter over an entire 24-h period. There was a significant relationship between body surface area and clearance. The data suggest that VL-2397 has nonlinear saturable binding kinetics. Protein binding is the likely primary source of the nonlinearity. The PPK model can now be used to optimize dosing by bridging the kinetics to efficacious pharmacodynamic targets.

scholarly journals Pharmacodynamic Modeling of Clarithromycin against Macrolide-Resistant [PCR-Positive mef(A) or erm(B)] Streptococcus pneumoniae Simulating Clinically Achievable Serum and Epithelial Lining Fluid Free-Drug Concentrations

2002 ◽  
Vol 46 (12) ◽  
pp. 4029-4034 ◽  
Author(s):  
Ayman M. Noreddin ◽  
Danielle Roberts ◽  
Kim Nichol ◽  
Aleksandra Wierzbowski ◽  
Daryl J. Hoban ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Compartment Model ◽  
Free Drug ◽  
Pharmacodynamic Modeling ◽  
Epithelial Lining ◽  
Bacterial Killing ◽  
Epithelial Lining Fluid ◽  
Initial Inoculum ◽  
Drug Concentrations

ABSTRACT The association between macrolide resistance mechanisms and clinical outcomes remains understudied. The present study, using an in vitro pharmacodynamic model, assessed clarithromycin (CLR) activity against mef(A)-positive and erm(B)-negative Streptococcus pneumoniae isolates by simulating free-drug concentrations in serum and both total (protein-bound and free) and free drug in epithelial lining fluid (ELF). Five mef(A)-positive and erm(B)-negative strains, one mef(A)-negative and erm(B)-positive strain, and a control [mef(A)-negative and erm(B)-negative] strain of S. pneumoniae were tested. CLR was modeled using a one-compartment model, simulating a dosage of 500 mg, per os, twice a day (in serum, free-drug Cp maximum of 2 μg/ml, t 1/2 of 6 h; in ELF, C ELF(total) maximum of 35μg/ml, t 1/2 of 6 h; CELF(free) maximum of 14 μg/ml, t 1/2 of 6 h). Starting inocula were 106 CFU/ml in Mueller-Hinton broth with 2% lysed horse blood. With sampling at 0, 4, 8, 12, 20, and 24 h, the extent of bacterial killing was assessed. Achieving CLR T/MIC values of ≥90% (AUC0-24/MIC ratio, ≥61) resulted in bacterial eradication, while T>MIC values of 40 to 56% (AUC0-24/MIC ratios of ≥30.5 to 38) resulted in a 1.2 to 2.0 log10 CFU/ml decrease at 24 h compared to that for the initial inoculum. CLR T/MIC values of ≤8% (AUC0-24/MIC ratio, ≤17.3) resulted in a static effect or bacterial regrowth. The high drug concentrations in ELF that were obtained clinically with CLR may explain the lack of clinical failures with mef(A)-producing S. pneumoniae strains, with MICs up to 8 μg/ml. However, mef(A) isolates for which MICs are ≥16 μg/ml along with erm(B) may result in bacteriological failures.

scholarly journals The PK/PD Integration and Resistance of Tilmicosin against Mycoplasma hyopneumoniae

Pathogens ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 487 ◽  
Author(s):  
Zilong Huang ◽  
Zixuan Hu ◽  
Haorui Zheng ◽  
Xirui Xia ◽  
Xiaoyan Gu ◽  
...  
Keyword(s):  
Compartment Model ◽  
Mycoplasma Hyopneumoniae ◽  
23S Rrna ◽  
Economic Losses ◽  
Resistant Bacteria ◽  
Time Curve ◽  
Microdilution Method ◽  
Optimal Dosing ◽  
Drug Concentrations

Mycoplasma hyopneumoniae is the major pathogen causing enzootic pneumonia in pigs. M. hyopneumoniae infection can lead to considerable economic losses in the pig-breeding industry. Here, this study established a first-order absorption, one-compartment model to study the relationship between the pharmacokinetics/pharmacodynamics (PK/PD) index of tilmicosin against M. hyopneumoniae in vitro. We simulated different drug concentrations of timicosin in the fluid lining the lung epithelia of pigs. The minimum inhibitory concentration (MIC) of tilmicosin against M. hyopneumoniae with an inoculum of 106 CFU/mL was 1.6 μg/mL using the microdilution method. Static time–kill curves showed that if the drug concentration >1 MIC, the antibacterial effect showed different degrees of inhibition. At 32 MIC, the amount of bacteria decreased by 3.16 log10 CFU/mL, thereby achieving a mycoplasmacidal effect. The M. hyopneumoniae count was reduced from 3.61 to 5.11 log10 CFU/mL upon incubation for 96 h in a dynamic model with a dose of 40–200 mg, thereby achieving mycoplasmacidal activity. The area under the concentration-time curve over 96 h divided by the MIC (AUC0–96 h/MIC) was the best-fit PK/PD parameters for predicting the antibacterial activity of tilmicosin against M. hyopneumoniae (R2 = 0.99), suggesting that tilmicosin had concentration-dependent activity. The estimated value for AUC0–96 h/MIC for 2log10 (CFU/mL) reduction and 3log10 (CFU/mL) reduction from baseline was 70.55 h and 96.72 h. Four M. hyopneumoniae strains (M1–M4) with reduced sensitivity to tilmicosin were isolated from the four dose groups. The susceptibility of these strains to tylosin, erythromycin and lincomycin was also reduced significantly. For sequencing analyses of 23S rRNA, an acquired A2058G transition in region V was found only in resistant M. hyopneumoniae strains (M3, M4). In conclusion, in an in vitro model, the effect of tilmicosin against M. hyopneumoniae was concentration-dependent and had a therapeutic effect. These results will help to design the optimal dosing regimen for tilmicosin in M. hyopneumoniae infection, and minimize the emergence of resistant bacteria.

scholarly journals Fractional Maximal Effect Method for In Vitro Synergy between Amoxicillin and Ceftriaxone and between Vancomycin and Ceftriaxone against Enterococcus faecalisand Penicillin-Resistant Streptococcus pneumoniae

2001 ◽  
Vol 45 (12) ◽  
pp. 3328-3333 ◽  
Author(s):  
Norbert Desbiolles ◽  
Lionel Piroth ◽  
Catherine Lequeu ◽  
Catherine Neuwirth ◽  
Henri Portier ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Graphical Representation ◽  
Maximal Effect ◽  
Bacterial Strains ◽  
Indifference Zone ◽  
Testing Method ◽  
Drug Concentrations ◽  
Time Kill ◽  
Effect Method

ABSTRACT In the present study we assessed the use of a new in vitro testing method and graphical representation of the results to investigate the potential effectiveness of combinations of amoxicillin (AMZ) plus ceftriaxone (CRO) and of CRO plus vancomycin (VAN) against strains of Streptococcus pneumoniae highly resistant to penicillin and cephalosporins (PRP strains). We used the fractional maximal effect (FME) method of time-kill curves to calculate adequate concentrations of the drugs to be tested rather than relying on arbitrary choices. The concentrations obtained, each of which corresponded to a fraction of the maximal effect, were tested alone and in combination with the bacterial strains in a broth medium. Synergy was defined as a ratio of observed effect/theoretical effect, called FME, of greater than 1, additivity was defined as an FME equal to 1, and antagonism was defined as an observed effect lower than the best effect of one of the antibiotics used alone. The area between antagonism and additivity is the indifference zone. The well-known synergy between amoxicillin and gentamicin against a reference strain of Enterococcus faecalis was confirmed, with a best FME equal to 1.07. Two strains of PRP, strains PRP-1 and PRP-2, were studied. The MICs for PRP-1 and PRP-2 were as follows: penicillin, 4 and 16 μg/ml, respectively; AMZ, 2 and 8 μg/ml, respectively, CRO, 1 and 4 μg/ml, respectively; and VAN, 0.5 and 0.25 μg/ml, respectively. For PRP-1 the best FME for the combination AMZ-CRO was 1.22 with drug concentrations of 1.68 mg/liter for AMZ and 0.17 mg/liter for CRO; the best FME for the combination VAN-CRO was 1.75 with VAN at 0.57 mg/liter and CRO at 0.17 mg/liter. For PRP-2 the best FME obtained for the combination AMZ-CRO was 1.05 with drug concentrations of 11.28 mg/liter for AMZ and 0.64 mg/liter for CRO; the best FME obtained for the combination VAN-CRO was 1.35 with VAN at 0.25 mg/liter and CRO at 1.49 mg/liter. These results demonstrated the synergy of both combinations, AMZ-CRO and VAN-CRO, against PRP strains at drug concentrations achievable in humans. Consequently, either of the combinations can be proposed for use for the treatment of PRP infections.

A 3D spheroid system to evaluate inhibitors of the ABCG2 transporter in drug uptake and penetration

TECHNOLOGY ◽  
2015 ◽  
Vol 03 (01) ◽  
pp. 54-63 ◽  
Author(s):  
Sean Curran ◽  
Toni-Marie Achilli ◽  
Elizabeth Leary ◽  
Benjamin T. Wilks ◽  
Marguerite M. Vantangoli ◽  
...  
Keyword(s):  
Fluorescent Microscopy ◽  
Time Lapse ◽  
Cell Types ◽  
Multidrug Resistant ◽  
In Vitro Models ◽  
Drug Uptake ◽  
Maximal Effect ◽  
Hoechst 33342 ◽  
Duration Of Effect

None of the ABCG2 inhibitors are effective clinically against multidrug resistant tumors overexpressing ABCG2. New in vitro models are needed to characterize inhibitors and discover new ones. We report a 3D spheroid model and image-based method to quantify ABCG2 action. Nonadhesive micro-molds were used to self-assemble spheroids overexpressing ABCG2; these spheroids were then incubated with the transporter substrate Hoechst 33342. Time-lapse fluorescent microscopy was used to determine the transporter-dependent efflux of Hoechst 33342 and dose response of three inhibitors (Ko143, Iressa, Elacridar). This 3D microtissue model was also used to determine the time to maximal effect as well as duration of effect after inhibitor removal. All acted within one hour and Elacridar had a surprisingly long duration of effect, active 5 hours after removal. This model can be used with multiple cell types, provides new insight into the pharmacokinetics of inhibitors, and can be adapted to high throughput analyses.

scholarly journals Influence of Selected Carbon Nanostructures on the CYP2C9 Enzyme of the P450 Cytochrome

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4149
Author(s):  
Justyna Sekretarska ◽  
Jarosław Szczepaniak ◽  
Malwina Sosnowska ◽  
Marta Grodzik ◽  
Marta Kutwin ◽  
...  
Keyword(s):  
Carbon Nanostructures ◽  
Drug Effects ◽  
In Vitro Models ◽  
Protein Levels ◽  
Enzymatic Function ◽  
Graphite Nanoparticles ◽  
Expression Site ◽  
Low Toxicity ◽  
Exogenous Compounds

Carbon nanostructures have recently gained significant interest from scientists due to their unique physicochemical properties and low toxicity. They can accumulate in the liver, which is the main expression site of cytochrome P450 (CYP450) enzymes. These enzymes play an important role in the metabolism of exogenous compounds, such as drugs and xenobiotics. Altered activity or expression of CYP450 enzymes may lead to adverse drug effects and toxicity. The objective of this study was to evaluate the influence of three carbon nanostructures on the activity and expression at the mRNA and protein levels of CYP2C9 isoenzyme from the CYP2C subfamily: Diamond nanoparticles, graphite nanoparticles, and graphene oxide platelets. The experiments were conducted using two in vitro models. A microsome model was used to assess the influence of the three-carbon nanostructures on the activity of the CYP2C9 isoenzyme. The CYP2C9 gene expression at the mRNA and protein levels was determined using a hepatoma-derived cell line HepG2. The experiments have shown that all examined nanostructures inhibit the enzymatic activity of the studied isoenzymes. Moreover, a decrease in the expression at the mRNA and protein levels was also observed. This indicates that despite low toxicity, the nanostructures can alter the enzymatic function of CYP450 enzymes, and the molecular pathways involved in their expression.

scholarly journals Pharmacodynamic Model To Describe the Concentration-Dependent Selection of Cefotaxime-Resistant Escherichia coli

2005 ◽  
Vol 49 (12) ◽  
pp. 5081-5091 ◽  
Author(s):  
Sara K. Olofsson ◽  
Patricia Geli ◽  
Dan I. Andersson ◽  
Otto Cars
Keyword(s):  
Escherichia Coli ◽  
Pharmacokinetic Parameters ◽  
Time Curve ◽  
Drug Concentrations ◽  
Elimination Half ◽  
Dosing Regimens ◽  
Bacterial Mixtures ◽  
High Level ◽  
Selection Of

ABSTRACT Antibiotic dosing regimens may vary in their capacity to select mutants. Our hypothesis was that selection of a more resistant bacterial subpopulation would increase with the time within a selective window (SW), i.e., when drug concentrations fall between the MICs of two strains. An in vitro kinetic model was used to study the selection of two Escherichia coli strains with different susceptibilities to cefotaxime. The bacterial mixtures were exposed to cefotaxime for 24 h and SWs of 1, 2, 4, 8, and 12 h. A mathematical model was developed that described the selection of preexisting and newborn mutants and the post-MIC effect (PME) as functions of pharmacokinetic parameters. Our main conclusions were as follows: (i) the selection between preexisting mutants increased with the time within the SW; (ii) the emergence and selection of newborn mutants increased with the time within the SW (with a short time, only 4% of the preexisting mutants were replaced by newborn mutants, compared to the longest times, where 100% were replaced); and (iii) PME increased with the area under the concentration-time curve (AUC) and was slightly more pronounced with a long elimination half-life (T 1/2) than with a short T 1/2 situation, when AUC is fixed. We showed that, in a dynamic competition between strains with different levels of resistance, the appearance of newborn high-level resistant mutants from the parental strains and the PME can strongly affect the outcome of the selection and that pharmacodynamic models can be used to predict the outcome of resistance development.

scholarly journals Human-induced pluripotent stem cell-derived cardiomyocytes, 3D cardiac structures, and heart-on-a-chip as tools for drug research

2021 ◽  
Author(s):  
Kalina Andrysiak ◽  
Jacek Stępniewski ◽  
Józef Dulak
Keyword(s):  
Clinical Trials ◽  
Pluripotent Stem Cell ◽  
Drug Research ◽  
Drug Effects ◽  
Induced Pluripotent Stem Cell ◽  
Cell Types ◽  
In Vitro Models ◽  
Cardiac Cell ◽  
Induced Pluripotent

AbstractDevelopment of new drugs is of high interest for the field of cardiac and cardiovascular diseases, which are a dominant cause of death worldwide. Before being allowed to be used and distributed, every new potentially therapeutic compound must be strictly validated during preclinical and clinical trials. The preclinical studies usually involve the in vitro and in vivo evaluation. Due to the increasing reporting of discrepancy in drug effects in animal and humans and the requirement to reduce the number of animals used in research, improvement of in vitro models based on human cells is indispensable. Primary cardiac cells are difficult to access and maintain in cell culture for extensive experiments; therefore, the human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) became an excellent alternative. This technology enables a production of high number of patient- and disease-specific cardiomyocytes and other cardiac cell types for a large-scale research. The drug effects can be extensively evaluated in the context of electrophysiological responses with a use of well-established tools, such as multielectrode array (MEA), patch clamp, or calcium ion oscillation measurements. Cardiotoxicity, which is a common reason for withdrawing drugs from marketing or rejection at final stages of clinical trials, can be easily verified with a use of hiPSC-CM model providing a prediction of human-specific responses and higher safety of clinical trials involving patient cohort. Abovementioned studies can be performed using two-dimensional cell culture providing a high-throughput and relatively lower costs. On the other hand, more complex structures, such as engineered heart tissue, organoids, or spheroids, frequently applied as co-culture systems, represent more physiological conditions and higher maturation rate of hiPSC-derived cells. Furthermore, heart-on-a-chip technology has recently become an increasingly popular tool, as it implements controllable culture conditions, application of various stimulations and continuous parameters read-out. This paper is an overview of possible use of cardiomyocytes and other cardiac cell types derived from hiPSC as in vitro models of heart in drug research area prepared on the basis of latest scientific reports and providing thorough discussion regarding their advantages and limitations.

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