Walter Krauwinkel

Absorption, Metabolism and Excretion of [14C]Mirabegron (YM178), a Potent and Selective β3-Adrenoceptor Agonist, after Oral Administration to Healthy Male Volunteers

The mass balance and metabolite profiles of 2-(2-amino-1,3-thiazol-4-yl)-N-[4-(2-{[(2R)-2-hydroxy-2-phenylethyl]amino}ethyl)[U-14C]phenyl]acetamide ([14C]mirabegron, YM178), a β3-adrenoceptor agonist for the treatment of overactive bladder, were characterized in four young, healthy, fasted male subjects after a single oral dose of [14C]mirabegron (160 mg, 1.85 MBq) in a solution. [14C]Mirabegron was rapidly absorbed with a plasma tmax for mirabegron and total radioactivity of 1.0 and 2.3 h postdose, respectively. Unchanged mirabegron was the most abundant component of radioactivity, accounting for approximately 22% of circulating radioactivity in plasma. Mean recovery in urine and feces amounted to 55 and 34%, respectively. No radioactivity was detected in expired air. The main component of radioactivity in urine was unchanged mirabegron, which accounted for 45% of the excreted radioactivity. A total of 10 metabolites were found in urine. On the basis of the metabolites found in urine, major primary metabolic reactions of mirabegron were estimated to be amide hydrolysis (M5, M16, and M17), accounting for 48% of the identified metabolites in urine, followed by glucuronidation (M11, M12, M13, and M14) and N-dealkylation or oxidation of the secondary amine (M8, M9, and M15), accounting for 34 and 18% of the identified metabolites, respectively. In feces, the radioactivity was recovered almost entirely as the unchanged form. Eight of the metabolites characterized in urine were also observed in plasma. These findings indicate that mirabegron, administered as a solution, is rapidly absorbed after oral administration, circulates in plasma as the unchanged form and metabolites, and is recovered in urine and feces mainly as the unchanged form.

Effect of Ipragliflozin (ASP1941), a Novel Selective Sodium-Dependent Glucose Co-Transporter 2 Inhibitor, on Urinary Glucose Excretion in Healthy Subjects

AbstractBackground: Hyperglycaemia is associated with serious complications, significant morbidity and death. Despite the availability of a wide range of therapeutic options, many patients with diabetes mellitus fail to achieve or maintain recommended glycaemic goals. Ipragliflozin (ASP1941) is a novel, selective inhibitor of the sodium-dependent glucose co-transporter 2, which is highly expressed in the proximal tubules of the kidneys. It suppresses renal glucose reabsorption and increases urinary glucose excretion (UGE), potentially providing an insulin-independent treatment option for type 2 diabetes. Methods: This multiple ascending-dose study assessed the safety, tolerability, pharmacokinetics and pharmacodynamics of ipragliflozin in healthy subjects after single doses and multiple once-daily doses for 10 days (dose levels: 5–600 mg). Results: Ipragliflozin was well tolerated following single and multiple once-daily oral dosing. Ipragliflozin was rapidly absorbed with a median time to reach the maximum plasma concentration of 1.3 hours after the last dose. The area under the plasma concentration-time curve increased proportionally with increasing dose. The mean elimination half-life was 12 hours following the last dose. Ipragliflozin dose dependently increased UGE up to a maximum of approximately 59 g (327 mmol) of glucose excreted over 24 hours following multiple doses, without affecting plasma glucose levels in healthy subjects. Conclusion: Administration of ipragliflozin was well tolerated and resulted in a rapid, dose-dependent increase in glucosuria. Pharmacodynamic and pharmacokinetic data suggest that ipragliflozin is suitable for prolonged once-daily oral treatment. Trial Registration: ClinicalTrials.gov Identifier: NCT01288898.

Pharmacokinetics and Safety of Solifenacin Succinate in Healthy Young Men

The pharmacokinetic profile of solifenacin succinate (YM905; Vesicare), a new once‐daily bladder‐selective muscarinic receptor antagonist, was examined in 2 controlled trials of healthy young men. A single‐dose study evaluated 5‐, 10‐, 20‐, 40‐, 60‐, 80‐, and 100‐mg doses. A multidose study evaluated 5‐, 10‐, 20‐, and 30‐mg doses. In the single‐dose study, mean time to maximal concentration and elimination half‐life ranged from 3.3 to 4.8 and from 40.2 to 57.6 hours, respectively; in the multidose study, the corresponding ranges were 2.9 to 5.8 and 45.0 to 64.8. Plasma concentration and area under the curve increased linearly with single doses in both trials. At steady state, a less regular increase was seen, with higher values in the 20‐mg group than in the 30‐mg group. All doses in the single‐dose study were well tolerated. At steady state, only the 30‐mg dose was not well tolerated. The most commonly reported adverse events were dry mouth, blurred vision, and headache. Solifenacin 5 and 10 mg, either as single doses or at steady state, had minimal effect on salivary flow, visual nearpoint, and the incidence of adverse events. Solifenacin was well tolerated up to single doses of 100 mg and after multiple doses of 20 mg. Its pharmacokinetic profile makes it suitable for qd administration.

Solifenacin Demonstrates High Absolute Bioavailability in Healthy Men

ObjectiveSolifenacin succinate (YM905; Vesicare®) is a promising new bladder selective muscarinic receptor antagonist under investigation for the treatment of overactive bladder. This study was designed to assess the absolute bioavailability of a single oral dose of solifenacin 10mg, which is twice the suggested starting dose.Study designSingle-centre, open-label, randomised, two-period, crossover, single-dose study.MethodsSolifenacin was administered orally as a 10mg dose and intravenously as a 5mg dose. Oral and intravenous (IV) doses were divided by a washout period of ≥14 days.Study participantsThe study group consisted of 12 healthy young men, aged 20–45 years, nine of whom completed the study.ResultsThe pharmacokinetic analysis comprised nine subjects. A single oral dose of solifenacin 10mg had a high absolute bioavailability of 88.0% (95% confidence interval 75.8, 102.1), low clearance (9.39 L/h [SD 2.68]), and an extensive mean volume of distribution at steady state (599L [SD 86]). Only 7% of solifenacin was excreted intact in the urine. Single oral and IV administration of solifenacin was well tolerated in this study. The most common adverse events related to drug treatment were headache and somnolence.ConclusionsPharmacokinetic analyses of single oral and IV doses of solifenacin demonstrated that the drug has a high absolute oral availability of 88%. This finding suggests that solifenacin may have a higher and less variable bioavailability than other antimuscarinic agents.

A Generic Multi-Compartmental CNS Distribution Model Structure for 9 Drugs Allows Prediction of Human Brain Target Site Concentrations

PurposePredicting target site drug concentration in the brain is of key importance for the successful development of drugs acting on the central nervous system. We propose a generic mathematical model to describe the pharmacokinetics in brain compartments, and apply this model to predict human brain disposition.MethodsA mathematical model consisting of several physiological brain compartments in the rat was developed using rich concentration-time profiles from nine structurally diverse drugs in plasma, brain extracellular fluid, and two cerebrospinal fluid compartments. The effect of active drug transporters was also accounted for. Subsequently, the model was translated to predict human concentration-time profiles for acetaminophen and morphine, by scaling or replacing system- and drug-specific parameters in the model.ResultsA common model structure was identified that adequately described the rat pharmacokinetic profiles for each of the nine drugs across brain compartments, with good precision of structural model parameters (relative standard error <37.5%). The model predicted the human concentration-time profiles in different brain compartments well (symmetric mean absolute percentage error <90%).ConclusionsA multi-compartmental brain pharmacokinetic model was developed and its structure could adequately describe data across nine different drugs. The model could be successfully translated to predict human brain concentrations.

No pharmacokinetic interaction between ipragliflozin and sitagliptin, pioglitazone, or glimepiride in healthy subjects.

To investigate the effect of ipragliflozin on the pharmacokinetics of sitagliptin, pioglitazone or glimepiride and vice versa in healthy subjects.

A Semiphysiological Population Model for Prediction of the Pharmacokinetics of Drugs under Liver and Renal Disease Conditions

The application of model-based drug development in special populations becomes increasingly important for clinical trial optimization, mostly by providing a rationale for dose selection and thereby aiding risk-benefit assessment. In this article, a semiphysiological approach is presented, enabling the extrapolation of the pharmacokinetics from healthy subjects to patients with different disease conditions. This semiphysiological approach was applied to solifenacin, using clinical data on total and free plasma and urine concentrations in healthy subjects. The analysis was performed using nonlinear mixed-effects modeling and relied on the use of a general partitioning framework to account for binding to plasma proteins and to nonplasma tissues together with principles from physiology that apply to the main pharmacokinetic process, i.e., bioavailability, distribution, and elimination. Application of these physiology principles allowed quantification of the impact of key physiological parameters (i.e., body composition, glomerular function, liver enzyme capacity, and liver blood flow) on the pharmacokinetics of solifenacin. The prediction of the time course of the drug concentration in liver- and renal-impaired patients only required adjustment of the physiological parameters that are known to change upon liver and renal dysfunction without modifying the pharmacokinetic model structure and/or its respective parameter estimates. Visual predictive checks showed that the approach applied was able to adequately predict the pharmacokinetics of solifenacin in liver- and renal-impaired patients. In addition, better insight into the pharmacokinetic properties of solifenacin was obtained. In conclusion, the proposed semiphysiological approach is attractive for prediction of altered pharmacokinetics of compounds influenced by liver and renal disease conditions.

Evaluation of the Pharmacokinetic Interaction Between the β3-Adrenoceptor Agonist Mirabegron and the Muscarinic Receptor Antagonist Solifenacin In Healthy Subjects

Mirabegron, a selective β3‐adrenoceptor agonist, is approved for the treatment of overactive bladder (OAB). Solifenacin is a muscarinic receptor antagonist widely used in the treatment of OAB. This open‐label, 1‐sequence, 2‐arm study investigated whether any pharmacokinetic interaction exists between mirabegron and solifenacin. In arm 1, 21 healthy men and women received 10 mg solifenacin succinate alone and in combination with mirabegron 100 mg qd. In arm 2, 20 healthy men and women received 100 mg mirabegron alone and in combination with solifenacin succinate 10 mg qd. Plasma samples were collected and tolerability was assessed. Following coadministration of mirabegron and solifenacin in arm 1, solifenacin geometric mean ratios (90% confidence interval [CI]) for Cmax and AUCinf were 1.23 (1.15, 1.31) and 1.26 (1.17, 1.35), respectively, compared with solifenacin alone, with a 1.07‐fold increase in mean t1/2. In arm 2, mirabegron ratios (90% CI) for Cmax and AUCinf were 0.99 (0.78, 1.26) and 1.15 (1.01, 1.30), respectively, for the combination relative to mirabegron alone, with an increase in mean tmax of approximately 1 hour. Mirabegron or solifenacin alone or in combination was generally well tolerated.

Tamsulosin shows a higher unbound drug fraction in human prostate than in plasma: a basis for uroselectivity?

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT The efficacy-tolerability profile of tamsulosin in patients with benign prostatic hyperplasia (BPH) is assumed to be associated both with the α1-adrenoceptor selectivity profile of the drug and a small peak : trough ratio in the plasma pharmacokinetic (PK) profile. Tamsulosin is highly bound to plasma proteins, notably α1-acid glycoprotein (AGP). This protein is a high-affinity binding protein and AGP plasma concentration was found to influence the therapeutic (unbound) plasma concentrations for high-AGP-binding drugs. WHAT THIS STUDY ADDS The study actually assessed unbound tamsulosin concentrations in both blood plasma and prostate tissue and reported that the unbound tamsulosin concentrations after multiple dosing in men with BPH, were much higher in prostate than in blood plasma. The assumption is put forward that differential free drug concentrations in prostate and blood plasma may contribute to the relative ‘uroselectivity’ of tamsulosin. AIM The aim of this small patient study was to investigate tamsulosin concentrations in prostate and plasma samples in order to identify potential differences in the pharmacokinetics (PK) in plasma and prostate contributing to its pharmacodynamic activity profile in patients. METHODS Forty-one patients with benign prostatic hyperplasia (BPH) scheduled for open prostatectomy were given tamsulosin 0.4 mg for 6-21 days in order to reach steady-state PK. Patients were randomized over four groups to allow collection of plasma and tissue samples at different time points after last dose administration. Samples were collected during surgery and assayed for tamsulosin HCl. The free fraction (f(u)) of tamsulosin was determined by ultracentrifugation of plasma and prostate tissue spiked with (14)C-tamsulosin. RESULTS C(max) in plasma at 4.4 h for total tamsulosin was 15.2 ng ml(-1) and AUC(0,24 h) was 282 ng ml(-1) h, while for prostate C(max) at 11.4 h post-dose was 5.4 ng ml(-1) and AUC(0,24 h) was 120 ng ml(-1) h. AUC(0,24 h) for total tamsulosin in prostate was 43% of the plasma AUC(0,24 h). f(u) was 0.4 % for plasma and 59.1% for prostate. Therefore calculated on unbound tamsulosin, a ratio of 63 resulted for prostate vs. plasma C(max) concentrations. CONCLUSIONS These data indicate that in patients with confirmed BPH the amount of tamsulosin freely available in the target tissue (prostate) is much higher than in plasma.

Prediction of human CNS pharmacokinetics using a physiologically-based pharmacokinetic modeling approach

ABSTRACT Knowledge of drug concentration‐time profiles at the central nervous system (CNS) target‐site is critically important for rational development of CNS targeted drugs. Our aim was to translate a recently published comprehensive CNS physiologically‐based pharmacokinetic (PBPK) model from rat to human, and to predict drug concentration‐time profiles in multiple CNS compartments on available human data of four drugs (acetaminophen, oxycodone, morphine and phenytoin). Values of the system‐specific parameters in the rat CNS PBPK model were replaced by corresponding human values. The contribution of active transporters for the four selected drugs was scaled based on differences in expression of the pertinent transporters in both species. Model predictions were evaluated with available pharmacokinetic (PK) data in human brain extracellular fluid and/or cerebrospinal fluid, obtained under physiologically healthy CNS conditions (acetaminophen, oxycodone, and morphine) and under pathophysiological CNS conditions where CNS physiology could be affected (acetaminophen, morphine and phenytoin). The human CNS PBPK model could successfully predict their concentration‐time profiles in multiple human CNS compartments in physiological CNS conditions within a 1.6‐fold error. Furthermore, the model allowed investigation of the potential underlying mechanisms that can explain differences in CNS PK associated with pathophysiological changes. This analysis supports the relevance of the developed model to allow more effective selection of CNS drug candidates since it enables the prediction of CNS target‐site concentrations in humans, which are essential for drug development and patient treatment. Graphical abstract Figure. No Caption available.