Unbound AUC Research Articles

Open-label, Single-dose Studies of the Pharmacokinetics of Edaravone in Subjects with Mild, Moderate, or Severe Hepatic Impairment Compared to Subjects with Normal Hepatic Functioning

PurposeTwo studies were conducted to assess the pharmacokinetic (PK) properties and tolerability of edaravone in Japanese subjects with mild to moderate hepatic impairment or normal hepatic functioning (study 1), and in white subjects with severe hepatic impairment compared to subjects with normal hepatic functioning (study 2). MethodsStudies 1 and 2 were multicenter, open-label, single-dose studies that included subjects aged 18–75 years. In study 1, subjects were stratified into 3 different groups of hepatic functioning according to Child-Pugh score: mild hepatic impairment, score 5 or 6 (n = 8); moderate hepatic impairment, score 7–9 (n = 6); or normal hepatic functioning (n = 8). In study 2, subjects had severe hepatic impairment (Child-Pugh score 10–14; n = 6) or normal hepatic functioning (n = 6). In both studies, all subjects were given edaravone 30 mg IV infused over 60 min on the morning of day 1. Blood samples for use in PK analyses were collected from days 1–3. The PK properties (Cmax, AUC0–last, and AUC0–∞) of edaravone and its sulfate conjugate metabolite were measured. FindingsIn study 1, the geometric least-squares mean (GLSM) Cmax and AUC0–∞ of unchanged edaravone were 1.203- and 1.065-fold greater, respectively, in subjects with mild hepatic impairment versus normal hepatic functioning, and were 1.235- and 1.142-fold greater, respectively, in subjects with moderate hepatic impairment versus normal hepatic functioning. In study 2, GLSM Cmax and AUC0–∞ of unchanged edaravone were 1.203- and 1.190-fold greater, respectively, in subjects with severe hepatic impairment versus normal hepatic functioning. In both studies the AUC0–last, AUC0–∞, unbound AUC from time zero to infinity, and Cmax of unchanged edaravone were increased slightly with increases in Child-Pugh classification. No adverse events considered related to edaravone were reported, except for 1 case of sinus bradycardia in a subject with normal hepatic functioning in study 2. The event was moderate in severity, considered as possibly related to edaravone, and resolved during the study. ImplicationsMild to moderate and severe hepatic impairment had no apparent clinically significant effects on the PK profile of edaravone in Japanese and white subjects, respectively, relative to individuals with normal hepatic functioning, and there were no notable tolerability concerns. Thus, edaravone dosage adjustments are unlikely to be needed in edaravone-treated patients with mild to moderate and severe hepatic impairment. ClinicalTrials.gov identifiers: NCT03289234 (mild to moderate hepatic impairment) and NCT03664544 (severe hepatic impairment).

A phase 1, open-label, single-dose study of the pharmacokinetics of zanubrutinib in subjects with varying degrees of hepatic impairment

The pharmacokinetics and safety of single-dose zanubrutinib (80 mg) were assessed in subjects with mild, moderate, and severe hepatic impairment (n = 6 each, Child–Pugh class A, B, and C) relative to healthy controls (n = 11). Zanubrutinib median Tmax was 1.25–2.25 h in all groups. Compared to control group, mean zanubrutinib exposure (AUC0–inf) in the mild and moderate hepatic impairment groups was increased by 1.1- and 1.2-fold, which is within the range of PK variability for zanubrutinib. The total and unbound AUC of zanubrutinib were 1.60- and 2.9-fold higher in subjects with severe hepatic impairment compared to healthy controls. Terminal half-life was comparable between subjects with hepatic impairment and matched healthy controls. Zanubrutinib was generally well-tolerated when administered as a single, 80-mg dose to subjects in this study. Results of this study will be used, in conjunction with clinical safety and efficacy data, to develop dose recommendations for patients with hepatic impairment.

Pharmacokinetics of the Novel Nonsteroidal Mineralocorticoid Receptor Antagonist Finerenone (BAY 94-8862) in Individuals with Mild or Moderate Hepatic Impairment.

Finerenone(BAY 94-8862) is a selective, nonsteroidal mineralocorticoid receptor antagonist. The aim of this study was to assess the effect of mild or moderate hepatic impairment on the pharmacokinetics, safety and tolerability of finerenone. The study was conducted in a single-center, nonrandomized, noncontrolled, nonblinded observational design with group stratification. A single oral 5-mg dose of finerenone was administered as a tablet to participants with mild or moderate hepatic impairment (Child-Pugh A, score 5-6 [n = 9], or Child-Pugh B, score 7-9 [n = 9], respectively) and to age-, weight- and sex-matched healthy participants (n = 9). The pharmacokinetics of finerenone and its metabolites were assessed in plasma and urine, and safety and tolerability were monitored. Finerenone area under the plasma concentration-time curve (AUC) and unbound AUC were 38% and 55% greater, respectively, in participants with moderate hepatic impairment than in healthy participants, whereas maximum plasma concentration (Cmax) was unchanged. No clear effects on AUC or Cmax were seen in participants with mild hepatic impairment. Finerenone was safe and well tolerated in all participants. The effects of mild or moderate hepatic impairment on systemic exposure of finerenone are small, consistent with its low hepatic extraction and preponderance of gastrointestinal over hepatic first-pass clearance. Considering the small increases in AUC and the absence of changes in Cmax, a dose adaptation does not appear to be warranted in patients with mild or moderate hepatic impairment.

Skin and soft tissue concentrations of tedizolid (formerly torezolid), a novel oxazolidinone, following a single oral dose in healthy volunteers

Plasma concentrations of antimicrobial drugs have long been used to correlate exposure with effect, yet one cannot always assume that unbound plasma and tissue concentrations are similar. Knowledge about unbound tissue concentrations is important in the development of antimicrobial drugs, since most infections are localised in tissues. Therefore, a clinical microdialysis study was conducted to evaluate the distribution of tedizolid (TR-700), the active moiety of the antimicrobial prodrug tedizolid phosphate (TR-701), into interstitial fluid (ISF) of subcutaneous adipose and skeletal muscle tissues following a single oral 600mg dose of tedizolid phosphate in fasting conditions. Twelve healthy adult subjects were enrolled. Two microdialysis probes were implanted into the thigh of each subject, one into the vastus medialis muscle and one into subcutaneous adipose tissue. Probes were calibrated using retrodialysis. Dialysate samples were collected every 20min for 12h following a single oral dose of 600mg tedizolid phosphate, and blood samples were drawn over 24h. Unbound tedizolid levels in plasma were similar to those in muscle and adipose tissue. The ratios of unbound (free) AUC in tissues over unbound AUC in plasma (fAUCtissue/fAUCplasma) were 1.1±0.2 and 1.2±0.2 for adipose and muscle tissue, respectively. The median half-life was 8.1, 9.2 and 9.6h for plasma, adipose tissue and muscle tissue, respectively. Mean protein binding was 87.2±1.8%. The study drug was very well tolerated. The results of this study show that tedizolid distributes well into ISF of adipose and muscle tissues. Unbound levels of tedizolid in plasma, adipose tissue and muscle tissue were well correlated. Free plasma levels are indicative of unbound levels in the ISF of muscle and adipose tissues.

Effect of streptozotocin‐induced diabetes mellitus on the pharmacokinetics of nelfinavir in rats

The HIV protease inhibitor, nelfinavir (NFV), has been used widely for HIV infection. The drug exhibits high binding characteristics to serum protein (unbound fraction: 0.01). The effect of experimentally induced diabetes mellitus on the pharmacokinetics of NFV was investigated, focusing on the change of protein-binding due to the glycosylation of albumin in streptozotocin-induced diabetes mellitus rats (diabetic rats). The unbound fraction of NFV in diabetic rats (0.04) was greater than that in the control (0.015). In diabetic rats, although the AUC of NFV was decreased after both intravenous (control: 1.75+/-0.08, diabetic: 1.36+/-0.17 microg h/ml) and intraduodenal (control: 1.69+/-0.25, diabetic: 1.19+/-0.39 microg h/ml) administrations, the unbound AUC was increased significantly (intravenous, control: 0.026+/-0.001, diabetic: 0.054+/-0.007 microg h/ml, intraduodenal, control: 0.025+/-0.004, diabetic: 0.048+/-0.016 microg h/ml). The unbound total clearance (control: 131.3+/-6.0, diabetic: 64.3+/-8.0 l/h/kg) and the unbound steady state distribution volume (control: 274.0+/-18.0, diabetic: 123.0+/-14.0 l/kg) were decreased significantly; therefore, greater pharmacological effects can be expected in diabetes mellitus. The contribution of increasing the unbound fraction to these results was significantly higher. In addition, there were no significant differences in the systemic and hepatic availability, peak time and mean absorption time between the diabetic and control rats, suggesting that diabetes mellitus did not affect the absorption of NFV.

A pharmacokinetic study of Genetaxyl (G) together with cyclosporin A (CsA) administered orally in cancer patients

12002 Background: Oral administration of paclitaxel given with CsA has shown promising activity in Phase II trials, but the apparent bioavailability is low and dose-dependent due to the presence of high concentrations of Cremophor EL (CrEL). We hypothesized that the use of a novel oral paclitaxel formulation containing only 20% CrEL (Genetaxyl [G]; Genovate Biotechnology Ltd., Taiwan), given with CsA is associated with an improved pharmacokinetic (PK) profile. Methods: Cohorts of 6 patients with cancer were treated with oral G at a dose of 60, 120, or 180 mg/m2 and 10 mg/kg of oral CsA in cycle 1. In cycle 2, patients received IV G (175 mg/m2, 3-h infusion). Three additional patients received generic IV paclitaxel (GIP). Serial blood samples were analyzed by LC/MS/MS and equilibrium dialysis, to determine total and unbound paclitaxel PK. Results: The mean (± SD) total paclitaxel AUCs were 1299±189, 1682±636, and 2204±1407 ng.h/mL at the 3 consecutive dose levels, suggesting nonlinear PK. However, based on unbound AUC, the oral bioavailability was dose-independent (P=.62), with a mean value of 37.2±18.6% (n=15). As expected, the total paclitaxel AUC following IV G (9024±4648 ng·h/mL) was lower than that for IV GIP (13,732±3983 ng·h/mL), as a result of increased clearance (39.6 vs 18.3 L/h) and a larger volume of distribution (768 vs 268 L). Interestingly, the unbound paclitaxel AUC was similar between the two IV formulations (P=.25), as the ratio of unbound/total paclitaxel for G was 2.5 times higher than that for GIP (12.5 vs 4.9%). Toxicity profiles were mild, with only 2 patients experiencing ≥ Gr 3 myelosuppression following oral G at 180 mg/m2. Conclusions: The mean bioavailability of paclitaxel following oral Genetaxyl with CsA was about 37%, which is higher than that observed previously with paclitaxel (range, 21–31%). Further clinical exploration of oral Genetaxyl in taxane-sensitive diseases is warranted. [Table: see text]

Mycophenolate Mofetil in Islet Cell Transplant: Variable Pharmacokinetics but Good Correlation Between Total and Unbound Concentrations

The authors investigated the pharmacokinetics of mycophenolic acid over 1 year in 8 Caucasian women undergoing islet cell transplantation. Total mycophenolic acid AUC(0-12) mcg x h/mL before day 60 was 62.1-67.8, declining to 33.6-64.7 thereafter (P = .61). Median total trough concentrations were 1.16-2.90 mcg/mL. Unbound AUC(0-12) was 412-673 ng x h/mL and did not change over time (P = .30). Median percent unbound mycophenolic acid was 0.95% of total concentrations. Individual unbound and total mycophenolic acid concentrations were highly correlated (r2 = 0.94). Total mycophenolic acid trough concentration and total AUC(0-12) were modestly correlated (r2 = 0.65). Intra- and interpatient variability of systemic mycophenolic acid exposure was high. Six patients required dose reductions prior to day 60 due to adverse effects. All subjects achieved insulin independence; 3 later lost graft function. The trend toward higher exposure in the early periods followed by dose reductions suggests that lower initial doses and therapeutic drug monitoring may be necessary.

In vivo specific binding characteristics and pharmacokinetics of a 1,4-dihydropyridine calcium channel antagonist in the senescent mouse brain.

To characterize the in vivo specific binding and pharmacokinetics of a 1,4-dihydropyridine (DHP) calcium channel antagonist, PN 200-110, in the senescent brain, using senescence-accelerated prone mice (SAMP8) and senescence-resistant mice (SAMR1). Blood, brain, and heart samples were taken periodically from SAMR1 and SAMP8 following intravenous injection of (+)-[3H]PN 200-110, and the concentration of (+)-[3H]PN 200-110 in the plasma and tissues was determined. In addition, the in vivo specific binding of (+)-[3H]PN 200-110 in the brains of SAMRI and SAMP8 was measured periodically after intravenous injection of the radioligand. There was very little significant difference between SAMR1 and SAMP8 in terms of the half-life (t(1/2)), total body clearance (CL(tot)), steady-state volume of distribution (Vd(ss)). and AUC for the plasma concentration of (+)-[3H]PN 200-110 after intravenous injection of the radioligand. The brain concentration (AUCbrain) for (+)-[3H]PN 200-110 and the brain/plasma AUC ratio (AUCbrain/AUCplasma) were significantly lower in SAMP8 than in SAMR1, and the heart concentration (AUCheart) and the heart/plasma AUC ratio (AUCheart/AUCplasma) were similar in both strains. Also, the brain/plasma unbound AUC ratio (AUCbrain/AUCplasma-free) for (+)-[3H]PN 200-110 was significantly lower in SAMP8 than in SAMRI. The in vivo specific binding (AUCspecific binding, maximal number of binding sites: Bmax) of (+)-[3H]PN 200-110 was significantly lower in brain particulate fractions of SAMP8 than SAMR1. The concentration and in vivo specific binding of (+)-[3H]PN 200-110 was significantly reduced in the senescent brain. The simultaneous analysis of the concentrations of centrally acting drugs and the in vivo specific binding in the brain in relation to their pharmacokinetics may be valuable in evaluating their CNS effects.