Plasma Protein Binding Research Articles

Clinical Pharmacology of Asciminib: A Review.

Asciminib is a first-in-class allosteric inhibitor of the kinase activity of BCR::ABL1, specifically targeting the ABL myristoyl pocket (STAMP). This review focuses on the pharmacokinetic (PK) and pharmacodynamic data of asciminib, which is approved at a total daily dose of 80 mg for the treatment of adult patients with chronic myeloid leukemia in chronic phase who are either resistant or intolerant to ≥ 2 tyrosine kinase inhibitors or those harboring the T315I mutation (at a dose of 200 mg twice daily). Asciminib is predicted to be almost completely absorbed from the gut, with an absolute bioavailability (F) of approximately 73%. It should be administered in a fasted state, as food (particularly high-fat meals) reduces exposure. Asciminib displays a slightly greater than dose-proportional increase in exposure, with no time-dependent changes in PK observed following repeated dosing. This drug shows low clearance (6.31 L/h), with a moderate volume of distribution (111 L) and high human plasma protein binding (97.3%). The apparent terminal elimination half-life (t1/2) across studies was estimated to be between 7 and 15h. The PK of asciminib is not substantially affected by body weight, age, gender, race, or renal or hepatic impairment. Asciminib is primarily metabolized via CYP3A4-mediated oxidation (36.0%) and UGT2B7- and UGT2B17-mediated glucuronidation (13.3% and 7.8%, respectively); biliary secretion via breast cancer resistance protein contributes to about 31.1% to total systemic clearance, which is mainly through hepatic metabolism and biliary secretion through the fecal pathway, with renal excretion playing a minor role. The potential for PK drug interaction for asciminib both as a victim and a perpetrator has been summarized here based on clinical and predicted drug-drug interaction studies. Robust exposure-response models characterized asciminib exposure-efficacy and exposure-safety relationships. In patients without the T315I mutation, the exposure-efficacy analysis of the time course of BCR::ABL1IS percentages highlighted the existence of a slightly positive, albeit not clinically significant, relationship. Higher exposure was required for efficacy in patients harboring the T315I mutation compared with those who did not. The exposure-safety relationship analysis showed no apparent association between exposure and adverse events of interest over the broad range of exposure or dose levels investigated. Asciminib has also been shown to have no clinically relevant effect on cardiac repolarization. Here, we review the clinical pharmacology data available to date for asciminib that supported its clinical development program and regulatory applications.

Changes in Plasma Clearance of CYP450 Probe Drugs May Not be Specific for Altered In Vivo Enzyme Activity Under (Patho)Physiological Conditions: How to Interpret Findings of Probe Cocktail Studies.

CYP450 (CYP) phenotyping involves quantifying an individual's plasma clearance of CYP-specific probe drugs, as a proxy for in vivo CYP enzyme activity. It is increasingly applied to study alterations in CYP enzyme activity under various (patho)physiological conditions, such as inflammation, obesity, or pregnancy. The phenotyping approach assumes that changes in plasma clearance of probe drugs are driven by changes in CYP enzyme activity. However, plasma clearance is also influenced by protein binding, blood-to-plasma ratio, and hepatic blood flow, all of which may change under (patho)physiological conditions. Using a physiologically based pharmacokinetic (PBPK) workflow, we aimed to evaluate whether the plasma clearance of commonly used CYP probe drugs is indeed directly proportional to alterations in CYP enzyme activity (sensitivity), and to what extent alterations in protein binding, blood-to-plasma ratio, and hepatic blood flow observed under (patho)physiological conditions impact plasma clearance (specificity). Plasma clearance of CYP probe drugs is sensitive to alterations in CYP enzyme activity, since alterations in intrinsic clearance between - 90% and + 150% resulted in near-proportional changes in plasma clearance, except for midazolam in the case of > 50% CYP3A4 induction. However, plasma clearance also changed near-proportionally with alterations in the unbound drug fraction, diminishing probe specificity. This was particularly relevant for high protein-bound probe drugs, as alterations in plasma protein binding resulted in larger relative changes in the unbound drug fraction. Alterations in the blood-to-plasma ratio and hepatic blood flow of ± 50% resulted in plasma clearance changes of less than ± 16%, meaning they limitedly impacted plasma clearance of CYP probe drugs, except for midazolam. In order to correct for the impact of non-metabolic determinants on probe drug plasma clearance, an R script was developed to calculate how much the CYP enzyme activity is actually altered under (patho)physiological conditions, when alterations in the unbound drug fraction, blood-to-plasma ratio, and/or hepatic blood flow also impact probe drug plasma clearance. As plasma protein binding can change under (patho)physiological conditions, alterations in unbound drug fraction should be accounted for when using CYP probe drug plasma clearance as a proxy for CYP enzyme activity in patient populations. The tool developed in this study can support researchers in determining alterations in CYP enzyme activity in patients with (patho)physiological conditions.

Therapeutic drug monitoring (TDM) of β-lactam/β-lactamase inhibitor (BL/BLI) drug combinations: insights from a pharmacometric simulation study.

The emergence of β-lactamase-producing bacteria has led to the use of β-lactam (BL) antibiotic and β-lactamase inhibitor (BLI) drug combinations. Despite therapeutic drug monitoring (TDM) being endorsed for BLs, the impact of TDM on BLIs remains unclear. Evaluate whether BLIs are available in effective exposures at the site of infection and assess if TDM of BLIs could be of interest. Population pharmacokinetic models for 9 BL and BLI compounds were used to simulate drug concentrations at infection sites following EMA-approved dose regimens, considering plasma protein binding and tissue penetration. Predicted target site concentrations were used for probability of target attainment (PTA) analysis. Using EUCAST targets, satisfactory (≥90%) PTA was observed for BLs in patients with typical renal clearance (CrCL of 80 mL/min) across various sites of infection. However, results varied for BLIs. Avibactam achieved satisfactory PTA only in plasma, with reduced PTAs in abdomen (78%), lung (73%) and prostate (23%). Similarly, tazobactam resulted in unsatisfactory PTAs in intra-abdominal infections (79%), urinary tract infections (64%) and prostatitis (34%). Imipenem-relebactam and meropenem-vaborbactam achieved overall satisfactory PTAs, except in prostatitis and high-MIC infections for the latter combination. This study highlights the risk of solely relying on TDM of BLs, as this can indicate acceptable exposures of the BL while the BLI concentration, and consequently the combination, can result in suboptimal performance in terms of bacterial killing. Thus, dose adjustments also based on plasma concentration measurements of BLIs, in particular for avibactam and tazobactam, can be valuable in clinical practice to obtain effective exposures at the target site.

Plasma protein binding of arsenic species in acute promyelocytic leukemia patients and their relationships with hepatic and renal function

ABSTRACT Objectives Percentage protein binding (%PB) of arsenic species in acute promyelocytic leukemia (APL) patients treated with arsenic trioxide remains unclear. It can be different depending on the status of hepatic or renal function. Methods This study obtained steady-state blood samples from normal APL patients and those with hepatic or renal impairment. %PB of inorganic arsenic (iAs), monomethylarsonic acid (MMAV), and dimethylarsinic acid (DMAV) was determined by analyzing free and total plasma concentrations using ultrafiltration method by HPLC-HG-AFS. Results There is a linear relationship between free and total plasma concentrations for iAs (r2 = 0.952), MMAV (r2 = 0.603), and DMAV (r2 = 0.945). For patients with normal hepatic and renal function, mean %PB was as follows: iAs at 26.7 ± 14.3%, MMAV at 53.3 ± 11.9%, and DMAV at 24.7 ± 7.8%. %PB decreased in patients with renal impairment, with MMAV and DMAV showing statistically significant differences (p < 0.05 for MMAV, p < 0.01 for DMAV). No significant differences in %PB between normal and hepatic impairment group were observed. Conclusion Free arsenic species fraction can be estimated by total concentration. DMAV and iAs present low %PB, while MMAV exhibits a relatively high %PB in plasma. Level of %PB is more likely to be affected by renal function and age.

Larvicidal activity, molecular docking, and molecular dynamics studies of 7-(trifluoromethyl)indolizine derivatives against Anopheles arabiensis.

A novel series of 7-(trifluoromethyl)indolizine derivatives (4a-4n) was synthesized using a 1,3-Dipolar cycloaddition reaction. Structure elucidation of the synthesized compounds was done using various spectroscopic techniques. Compounds were assessed for their larvicidal activity against Anopheles arabiensis. Exposure of Anopheles arabiensis larvae to a series of 7-(trifluoromethyl)indolizine at 4µg/mL for 24 and 48h resulted in moderate to high larval mortality rates. Among them, compounds 4b, 4a, 4g, and 4m exhibited the most promising larvicidal activities, with mortality rates of 94.4%, 93.3%, 80.00%, and 85.6%, respectively, compared to controls, Acetone and Temephos. The structural activity relationship analysis of the evaluated compounds revealed that substitution with halogens or electron-withdrawing groups (CN, F, Cl, Br) at the para position of the benzoyl group is crucial for achieving promising larvicidal activity. Molecular docking studies were carried out involving six potential larvicidal target proteins to predict how the tested compounds might work. Compounds 4a and 4b showed strong binding to the Mosquito Juvenile Hormone-Binding Protein (5V13). Molecular dynamics (MD) simulations confirmed the stability of the protein-ligand complexes over the simulation period, reinforcing the reliability of the docking results. Compounds 4a and 4b also exhibited favourable ADMET profiles, showing high oral bioavailability, good permeability, moderate distribution, low plasma protein binding, sufficient metabolic stability, efficient renal clearance and low toxicity. Given the crucial role of Juvenile Hormone in regulating gene expression and developmental pathways through receptor interactions, compounds 4a and 4b show promise as inhibitors of this protein. Inhibiting this process could hinder larval growth and reproduction, presenting a promising approach for early-stage mosquito larvicidal activity. Therefore, compounds 4a and 4b represent lead candidates for further optimization and the development of new larvicidal agents.

Target-site cefiderocol pharmacokinetics in soft tissues of healthy volunteers.

Cefiderocol may potentially be used to treat skin and soft tissue infections (SSTIs). However, the pharmacokinetics of cefiderocol in human soft tissues have not yet been determined. The objective of the present PK study was to investigate whether target-site concentrations of cefiderocol are sufficiently high for the treatment of SSTIs. In this pharmacokinetic study, a single intravenous dose of 2 g cefiderocol was administered to eight healthy male volunteers. Drug concentrations were determined in plasma, muscle and subcutis over 8 h. Free plasma concentrations were calculated using the plasma protein binding determined with ultrafiltration. Free tissue concentrations were obtained using microdialysis. Penetration ratios were calculated as AUC0-8h_free_tissue/AUC0-8h_free_plasma. A population pharmacokinetic model was developed, and the probability of target attainment (PTA) was determined using Monte Carlo simulations. Cefiderocol showed good tissue penetration, with mean penetration ratios ± standard deviation of 0.99 ± 0.33 and 0.92 ± 0.30 for subcutis and muscle, respectively. Cefiderocol pharmacokinetics in plasma were best described with a two-compartment model, and tissue concentrations were described by scaling the tissue concentrations to concentrations in the peripheral compartment of the plasma model. For a thrice-daily regimen with 2 g doses intravenously infused over 3 h, PTA was ≥90% for MIC values up to 4 mg/L, both based on free plasma and soft tissue pharmacokinetics. This study indicates that a dose of 2 g cefiderocol achieves concentrations in plasma considered sufficient for treating relevant bacterial species. Assuming a comparable PK/PD target for soft tissues, sufficiently high concentrations would also be achieved in soft tissues.

Intercalating compounds alongside DNA helicase Q1 Plasmodium falciparum 3D7: Assessments of the Pharmacokinetic Properties Prediction of ADME.

Quantum chemical & molecular docking practices to deliver new perceptions into how etoposide, novobiocin, nogalamycin and netropsin interact with the biological targets PF3D7_0918600 (Plasmodium falciparum 3D7). Further the pharmacokinetics of a drug candidate which influenced by a variety of factors, including P- glycoprotein (Pgp) transport, PBB (Plasma protein binding), & BBB (Blood-brain barrier) permeation help to forecast the pharmacological characteristics of acetyl-CoA reductase inhibitors (ADMEs) and their metabolites. At this point, we have elevated four compounds such as etoposide, novobiocin, nogalamycin & netropsin. We have also studied molecular docking against the target protein of the Plasmodium falciparum (PF3D7_0918600) through exhausting the AutoDock Vina platform and AutoDock-Tools (ADT) and pharmacokinetic properties were carried out using the ADMET 2.0. The relative results of molecular docking recommended a greater binding affinity of novobiocin with the selected receptors among other compounds. In-silico ADME screening is a computational approach utilised to forecast the pharmacological characteristics of acetyl- CoA reductase inhibitors (ADMEs) and their metabolites. The ADMEs are based on the adsorption-desorption kinetics and pharmacopoeia. Adsorption and distribution analysis are used to assess the potential of the drug candidate. In vitro ADME is exploited to expect the effect of Pgp transport on the drug candidates. ADME has been used to predict CYP1A2 inhibitors and to predict PPB and BBB penetration. This paper summarizes the current knowledge on molecular docking, ADME and identifies potential drug candidates for ADME in vitro and in vivo.

Docking, Synthesis, and In vitro Anti-depressant Activity of Certain Isatin Derivatives.

In vitro, the molecular docking method has been suggested for estimating the biological affinity of the pharmacophores with physiologically active compounds. It is the latter stage in molecular docking, and the docking scores are examined using the AutoDock 4.2 tool program. The chosen compounds can be evaluated for in vitro activity based on the binding scores, and the IC50 values can be computed. The purpose of this work was to create methyl isatin compounds as potential antidepressants, compute physicochemical characteristics, and carry out docking analysis. The protein data bank of the RCSB (Research Collaboratory for Structural Bioinformatics) was used to download the PDB structures of monoamine oxidase (PDB ID: 2BXR) and indoleamine 2,3-dioxygenase (PDB ID: 6E35). Based on the literature, methyl isatin derivatives were chosen as the lead chemicals. By determining their IC50 values, the chosen compounds were tested for in vitro anti-depressant activity. The binding scores for the interactions of SDI 1 and SD 2 with indoleamine 2,3 dioxygenase were found to be -10.55 kcal/mol and -11.08 kcal/mol, respectively, while the scores for their interactions with monoamine oxidase were found to be -8.76 kcal/mol and -9.28 kcal/mol, respectively, using AutoDock 4.2. The relationship between biological affinity and pharmacophore electrical structure was examined using the docking technique. The chosen compounds were tested for their ability to inhibit MAO, and the IC50 values for each were found to be 51.20 and 56, respectively. This investigation has identified many novel and effective MAO-A inhibitors from the family of chemicals known as methyl isatin derivatives. Lead optimization was applied to the SDI 1 and SDI 2 derivatives. The superior bioactivity, pharmacokinetic profile, BBB penetration, pre-ADMET profiles, such as HIA (human intestinal absorption) and MDCK (Madin-Darby canine kidney), plasma protein binding, toxicity assessment, and docking outcomes, have been obtained. According to the study, synthesised isatin 1 and SDI 2 derivatives exhibited a stronger MAO inhibitory activity and effective binding energy, which may help prevent stress-induced depression and other neurodegenerative disorders caused by a monoamine imbalance.

The state-of-the-art machine learning model for Plasma Protein Binding Prediction: computational modeling with OCHEM and experimental validation

The state-of-the-art machine learning model for Plasma Protein Binding Prediction: computational modeling with OCHEM and experimental validation

Synthesis and structure-affinity relationships of spirocyclic σ1 receptor ligands with tetrahydropyran scaffold

The σ1 receptor plays a key role in the regulation of various processes in the human body; it is involved in the development of neurodegenerative and neuropsychiatric diseases and is overexpressed in several human tumors rendering it an important target for potential drug candidates. In this project, spirocyclic σ1 receptor ligands with different substituents in 4- and 9-position were synthesized and investigated for their σ1 receptor affinity and selectivity over related targets. The σ1 affinity of the ligands was correlated with their lipophilicity (logD7.4 value) giving insight into their lipophilic ligand efficiency (LLE). The (pyridin-3-yl)methyl derivative 5i showed a promising balance of high σ1 affinity (Ki(σ1) = 3.9 nM) and selectivity (> 250-fold) as well as high LLE of 5.8. 5i has a high plasma protein binding (89%) and promising metabolic stability in the presence of mouse liver microsomes and NADPH (83% intact after 90 min). Increasing the size of the piperidine ring of the spirocyclic ligands 5 to an azepane ring led to considerably increased σ1 affinity (Ki(5a) = 1.2 nM, Ki(23a) = 0.42 nM) and selectivity over σ2 receptors (5a: 45-fold, 23a: 150-fold).

Chronopharmacokinetics: A Brief Analysis of the Influence of Circadian Rhythm on the Absorption, Distribution, Metabolism, and Elimination of Drugs

Chronopharmacokinetics is a specialized field within pharmacokinetics that focuses on how the timing of drug administration affects the absorption, distribution, metabolism, and elimination of drugs. The circadian rhythm, governed by the body's biological clock, plays a crucial role in pharmacokinetics, which encompasses the absorption, distribution, metabolism, and elimination of drugs. These pharmacokinetic processes are subject to daily variations influenced by the circadian rhythm. Drug absorption can fluctuate due to changes in gastrointestinal function, such as motility and gastric pH, and blood circulation. Similarly, the distribution of drugs in the body is influenced by factors such as tissue perfusion, plasma protein binding, and cell membrane permeability, all of which are modulated by the circadian rhythm. Metabolism, especially hepatic metabolism, can also experience circadian variations that affect the rate at which drugs are processed and converted into active or inactive metabolites. Finally, the elimination of drugs, primarily through renal function, can show circadian rhythms that impact the excretion of compounds from the body. Understanding these circadian fluctuations is essential to optimize the efficacy and safety of pharmacological treatments, as dosages and administration times could be adjusted to align with the peaks of biological clock activity. Thus, treatments can be more effective and have fewer side effects by leveraging the circadian variability in pharmacokinetic processes.

Effect of Renal and Hepatic Impairment on the Pharmacokinetics of Pritelivir and Its Metabolites.

Two trials were performed to evaluate the effect of renal and hepatic impairment on the pharmacokinetics of pritelivir and its metabolites. The renal impairment trial included subjects with mild, moderate, and severe impairment, while the hepatic impairment trial included subjects with moderate impairment. Both trials recruited a matched control group of healthy subjects. Following a single oral dose of 100mg of pritelivir, mild and moderate renal impairment and moderate hepatic impairment did not have a clinically relevant effect on the pharmacokinetics of pritelivir. In subjects with severe renal impairment, pritelivir exposure (area under the plasma concentration-time curve from time 0 to infinity (AUC0- inf) was 57% higher compared with controls. Pritelivir plasma protein binding was similar in subjects and controls with renal impairment, while the free fraction was higher in subjects with moderate hepatic impairment, increasing unbound pritelivir exposure by 23%. For the metabolites pyridinyl phenyl acetic acid (PPA), amino thiazole sulfonamide (ATS), and PPA-acyl glucuronide, generally higher exposure was observed with increasing degree of renal impairment (ie, moderate to severe), but not with mild impairment. A modest effect of moderate hepatic impairment was observed for PPA and ATS. Pritelivir was safe and well tolerated in healthy subjects and subjects with renal or hepatic impairment.

Development and Validation of an LC-MS/MS Assay for the Quantitation of MO-OH-Nap Tropolone in Mouse Plasma: Application to In Vitro and In Vivo Pharmacokinetic Studies.

A rapid, selective, and sensitive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantitation of MO-OH-Nap tropolone (MO-OH-Nap) in mouse plasma. MO-OH-Nap is an α-substituted tropolone with anti-proliferative properties in various cancer cell lines. Detection and separation of analytes was achieved on an ACE Excel C18 (1.7 µm, 100 × 2.1 mm, MAC-MOD Analytical, Chadds Ford, PA, USA) column with mobile phase consisting of 0.05% trifluoroacetic acid in water (mobile phase A) and 0.05% trifluoroacetic acid in acetonitrile (mobile phase B), with an isocratic elution of 15:85% (A:B) at a total flow rate of 0.25 mL/min. The LC-MS/MS system was operated at unit resolution in multiple reaction monitoring (MRM) mode, using precursor ion > product ion combination of 249.10 > 202.15 m/z for MO-OH-Nap and 305.10 > 215.05 m/z for the internal standard (IS), BA-SM-OM. The MS/MS response was linear over a concentration range of 1 to 500 ng/mL with a correlation coefficient (r2) of ≥0.987. The within- and between-batch precision (%RSD) and accuracy (%Bias) were within acceptable limits. The validated method was successfully applied to determine MO-OH-Nap metabolic stability, plasma protein binding, and bio-distribution studies of MO-OH-Nap in CD-1 mice.

Pharmacokinetics and Plasma Protein Binding of Flunixin in Rainbow Trout (Oncorhynchus mykiss).

Flunixin's pharmacokinetics, bioavailability, and plasma protein binding were examined in rainbow trout. The experiment involved 252 rainbow trout (Oncorhynchus mykiss) maintained at 12 ± 0.6°C. Flunixin was administered to rainbow trout via intravascular (IV), intramuscular (IM), and oral routes at a dosage of 2.2 mg/kg. Plasma samples were collected at times 0 (control), 0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, 24, 48, 72, and 96 h. High-pressure liquid chromatography-ultraviolet was employed to quantify flunixin concentrations. The elimination half-life (t1/2ʎz) for flunixin was 8.37 h for IV, 8.68 h for IM, and 8.76 h for oral. The t1/2ʎz was similar between administration groups. The volume of distribution at a steady state and total body clearance were 55.81 mL/kg and 6.83 mL/h/kg, respectively, after IV administration. The mean peak plasma concentration was 6.24 ± 0.41 μg/mL at 4 h for oral administration and 13.98 ± 0.86 μg/mL at 2 h for IM administration. The invitro protein binding ratio of flunixin in rainbow trout plasma was 96.34 ± 2.29%. The bioavailability of flunixin after oral (25.74%) administration was lower than that after IM (66.70%) administration. Thus, developing an oral pharmaceutical formulation that can be administered with feed and has high bioavailability could enhance the therapeutic effect.

In vitro ADME, mouse pharmacokinetics of LD14b, and bioanalysis of a novel aβ 17β-HSD10 modulator for the treatment of Alzheimer’s disease

LD14b is an amyloid-β (Aβ) 17β-hydroxysteroid dehydrogenase type 10 (Aβ-17β-HSD10) protein-protein interaction modulator that shows promising in vitro and ex vivo activity to rescue Aβ-induced mitochondrial dysfunction, Aβ-induced toxicity, and Aβ-mediated inhibition of estradiol synthesis. The current study investigated in vitro human S9 fractions metabolic stability, apparent permeability, human and mouse plasma protein binding, in vivo pharmacokinetics, and tissue distribution in Balb/cJ mice. A fast (8-min), sensitive, reliable, and reproducible LC-MS/MS method was developed and validated over the dynamic range of 1-1000 ng/mL for the quantification of LD14b in different biological matrices (plasma, liver, kidney, brain, lungs, heart). LD14b was metabolically stable in human liver S9 fractions with 70% remaining after 90 minutes of incubation, showed intermediate apparent permeability of 3.55 × 10−06 cm/s and 6.16 × 10−06 cm/s for apical-to-basolateral (A-to-B) and basolateral-to-apical (B-to-A), respectively across the Caco-2 monolayer, and was medium/highly bound to human plasma proteins (84.1%), mouse plasma proteins (85.7%), and mouse brain homogenate (95.4%). LD14b showed an in vivo predicted % absorption of 52% in Balb/cJ mice and was well-distributed to the peripheral tissues (liver, kidney, lungs, and heart) including the brain.

Heteroaryl derivatives of suvorexant as OX1R selective PET ligand candidates: Cu-mediated 18F-fluorination of boroxines, in vitro and initial in vivo evaluation

BackgroundThe orexin receptor (OXR) plays a role in drug addiction and is aberrantly expressed in colorectal tumors. Subtype-selective OXR PET ligands suitable for in vivo use have not yet been reported. This work reports the development of 18F-labeled OXR PET ligand candidates derived from the OXR antagonist suvorexant and the OX1R-selective antagonist JH112.ResultsComputational analysis predicted that fluorine substitution (1e) and introduction of the fluorobenzothiazole scaffold (1f) would be suitable for maintaining high OX1R affinity. After multi-step synthesis of 1a–1f, in vitro OXR binding studies confirmed the molecular dynamics calculations and revealed single-digit nanomolar OX1R affinities for 1a–f, ranging from 0.69 to 2.5 nM. The benzothiazole 1f showed high OX1R affinity (Ki = 0.69 nM), along with 77-fold subtype selectivity over OX2R. Cu-mediated 18F-fluorination of boroxine precursors allowed for a shortened reaction time of 5 min to provide the non-selective OXR ligand [18F]1c and its selective OX1R congener [18F]1f in activity yields of 14% and 22%, respectively, within a total synthesis time of 52–76 min. [18F]1c and [18F]1f were stable in plasma and serum in vitro, with logD7.4 of 2.28 ([18F]1c) and 2.37 ([18F]1f), and high plasma protein binding of 66% and 77%, respectively. Dynamic PET imaging in rats showed similar brain uptake of [18F]1c (0.17%ID/g) and [18F]1f (0.15%ID/g). However, preinjection of suvorexant did not significantly block [18F]1c or [18F]1f uptake in the rat brain. Pretreatment with cyclosporine A to study the role of P-glycoprotein (P-gp) in limiting brain accumulation moderately increased brain uptake of [18F]1c and [18F]1f. Accordingly, in vitro experiments demonstrated that the P-gp inhibitor zosuquidar only moderately inhibited polarized, basal to apical transport of 1c (p < 0.05) and had no effect on the transport of 1f, indicating that P-gp does not play a relevant role in brain accumulation of [18F]1c and [18F]1f in vivo.ConclusionsThe in vitro and in vivo results of [18F]1c and [18F]1f provide a solid basis for further development of suitable OXR PET ligands for brain imaging.

An overview of interpretability of two models of unbound fraction that are used in combination with the well-stirred model for predicting hepatic clearance of drugs

Hypothetical and experimental models of unbound fraction have been proposed to facilitate predicting the hepatic clearance (CLH) of drugs from values of intrinsic clearance for the unbound drug (CLint-in vitro-unbound) and the well-stirred model (WSM). The hypothetical model (fu-adjusted) is adjusting the unbound fractions determined in plasma in vitro to estimate the maximum unbound fractions at the hepatocytes if each drug-protein complex in plasma becomes fully dissociated at the membrane by any albumin (ALB)-facilitated hepatic uptake mechanism. The model of fu-adjusted is also adjusting the unbound fraction for a pH gradient effect across the membrane. Alternatively, the new experimental model (fu-dynamic) measures the unbound fractions resulting to the dynamic dissociation kinetics from proteins in the presence of plasma and a liver enzyme in an in vitro assay. The objective of this study was to conduct an in-depth analysis of previous CLH predictions made with these unbound fractions in a companion manuscript. Furthermore, a new dataset on transporter substrates was also included in this study. Finally, the physiological basis of fu-adjusted has been redefined to extend its applicability with more drugs. In this case, there are lower concentrations of binding proteins in liver versus plasma that could also explain the higher unbound fractions for that organ. The outcomes associated to additional analyses pointed out that fu-adjusted, again, generally provided the most accurate predictions of CLH because fu-dynamic has generated superior biases of underpredictions or overpredictions. For slowly metabolized drugs bound to ALB, fu-dynamic was definitively less accurate than fu-adjusted. For other drug properties, fu-dynamic fared better but it was still not generally more accurate than fu-adjusted. Furthermore, experimental values of fu-dynamic were sometimes incoherent. For example, drugs bound to alpha-acid glycoprotein (AGP) did not follow the principle of fu-dynamic (i.e., values of fu-dynamic did not correlate with values of CLint-in vitro-unbound) by contrast to those drugs bound to ALB. Therefore, the current experimental setting for fu-dynamic might be unsuitable in some circumstances. Overall, this study confirmed that calculated values of fu-adjusted were as accurate as experimental values of fu-dynamic and can even be more accurate. A guidance on which unbound fraction to use in the WSM is also provided.

POPULATION PHARMACOKINETICS OF CEFPODOXIME IN BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS).

Cefpodoxime proxetil is commonly used to treat cetacean patients with suspected or confirmed bacterial infections; however, pharmacokinetic data are needed to guide proper dosing in these species. Cefpodoxime proxetil is a time-dependent, semisynthetic, third-generation cephalosporin, appropriate for once-daily dosing and U.S. Food and Drug Administration-approved for use in dogs with a broad spectrum of activity including gram-positive and gram-negative species. The objective of this study was to evaluate the population pharmacokinetics of cefpodoxime in bottlenose dolphins (Tursiops truncatus). A sparse-sampling design was used, with serum from dolphins receiving cefpodoxime proxetil at 10 mg/kg orally every 24 h to treat suspected or confirmed bacterial infections. Serum samples (n = 57) from 24 dolphins were analyzed at 12 time points from 0 to 96 h postdose. Serum samples were analyzed using liquid chromatography-mass spectrometry. Population pharmacokinetic analysis was performed using nonlinear mixed-effects modeling. One- and two-compartment linear models with first order absorption were tested. Covariates including weight, age, and sex were considered for inclusion in the model, and between-subject variability was incorporated. A two-compartment model performed best, where following an oral dose of 10 mg/kg, serum concentration reached a mean maximum concentration of 23.0 µg/ml, mean time to maximum concentration of 5.0 h, and mean half-life of 11.4 h. With daily dosing, accumulation was approximately 18% and steady state was reached by the second dose. Serum protein binding was 82.8% as determined by equilibrium dialysis, similar to plasma protein binding reported in dogs. Based on the population pharmacokinetic model, once-daily oral dosing was systemically absorbed and quickly reached maximum concentrations. The half-life in dolphins appears to be longer than other species studied to date. Given the paucity of antimicrobial pharmacokinetic studies in dolphins, and limited once-daily oral antibiotic options for this species, these data are helpful for clinicians to make informed antimicrobial choices.

Does Age Influence Immunosuppressant Drug Pharmacokinetics in Kidney Transplant Recipients?

The pharmacokinetics of immunosuppressant drugs may change with advancing age, potentially affecting patient outcomes. To characterise the effects of age on the pharmacokinetic and exposure parameters of tacrolimus, mycophenolate, and prednisolone. Pharmacokinetic profiling, involving whole blood tacrolimus, total and free plasma mycophenolic acid (MPA), total plasma mycophenolic acid glucuronide (MPAG), and total and free plasma prednisolone, was performed in an older and younger adult cohort. Thirteen samples were drawn on a single occasion, pre-oral dose and then at 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 3, 4, 6, 9, and 12h post-dose. Non-compartmental analysis was conducted using the PKNCA package, and pharmacokinetic and exposure parameters were compared between age groups using a Mann-Whitney test. A regression analysis was conducted for free MPA and MPAG using significant variables of interest. This exploratory study included 21 older and 18 younger adults. Dose-adjusted tacrolimus, total MPA and free prednisolone pharmacokineticparameters were not different between age groups; however, for free MPA and MPAG, older recipients had significantly greater minimum and maximum concentrations, trough concentrations, and half-life. There was a two-fold increase in free MPA exposure in older adults (median dose-adjusted AUC0-12: 1284 vs. 684μgh/L, p<0.0001); MPAG exposure similarly increased. Age was significantly associated with free MPA and MPAG exposure, and free MPA exposure was associated with haematocrit (p<0.05). Differences in MPA were found with advancing age and may be due to altered kidney function, haematocrit, plasma protein binding and/or drug absorption. Future research should explore specific covariate contributions to this further.

Pharmacokinetic Profile of Ceftriaxone and Meropenem in Dogs

The principal aim of the study was evaluating the pharmacokinetic of ceftriaxone and meropenem in dogs, eight healthy male dogs were used for this experiment. A microbiological assay was used to determine the pharmacokinetic indices of ceftriaxone and meropenem given intravenously. The values were then fitted to a two-compartment pharmacokinetic open model in order to assess the factors related to distribution and excretion. The obtained results showed that the half-life, volume of distribution, and total body clearance to the samples of plasma of ceftriaxone and meropenem were recorded (0.83 h., 0.35 L/kg and 0.28 L/hr/kg), (0.86 h., 0.48 L/kg and 0.33 L/hr/kg), and the ratio of plasma protein binding were 16.67 %; 9.58 %, respectively. In conclusion, through the pharmacokinetic characteristics of meropenem and ceftriaxone in dogs, they possess an efficacious profile against K. pneumonia as same as other sensitive bacteria which were qualified to be a potential candidate to be one of the most commonly used parenterally administered antibacterial medicines in the treatment of acute bacterial cases that need to be treated quickly in veterinary therapy. However, the differences in the pharmacokinetic profile proved that the effectiveness of meropenem was more than ceftriaxone.