Marloes Schaddelee

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.

An example of optimal phase II design for exposure response modelling

This paper presents an example of how optimal design methodology was used to help design a phase II clinical study. The planned analysis would relate the clinical endpoint to exposure (measured via the area under the curve (AUC)), rather than dose. Optimal design methodology was used to compare a number of candidate phase II designs, and an algorithm for finding optimal designs was employed. The sigmoidal Emax with baseline (E0) model was used to relate the clinical endpoint to individual subject AUCs, and the primary metrics were D optimality and the standard error (SE) of the AUC required to yield a clinically relevant change in the clinical endpoint. The performance of the candidate designs were compared across four different ‘true’ exposure response relationships (determined from the analysis of an earlier proof of concept (PoC) study). The results suggested the total sample size should be increased from the planned 540 individuals, and that the optimal design with 700 individuals would be equivalent to 812 individuals with the reference design (a 16% gain). The performance with this design was considered acceptable, although all designs performed poorly if the true exposure response relationship was very flat. This work allowed a prospective assessment of the likely performance and precision from the exposure response modelling prior to the start of the phase II study, and hence allowed the design to be revised to ensure the subsequent analysis would be of most value.

The Hypoxia-inducible Factor Prolyl-Hydroxylase Inhibitor Roxadustat (FG-4592) and Warfarin in Healthy Volunteers: A Pharmacokinetic and Pharmacodynamic Drug–Drug Interaction Study

PURPOSE Roxadustat is a small-molecule hypoxia-inducible factor prolyl-hydroxylase inhibitor in late-stage clinical development for the treatment of anemia in patients with chronic kidney disease (CKD). Warfarin is an oral anticoagulant with a narrow therapeutic window that is often prescribed to treat coexisting cardiovascular diseases in patients with CKD. This clinical trial was designed to evaluate the effect of roxadustat on warfarin pharmacokinetic and pharmacodynamic parameters. METHODS This open-label, single-sequence crossover study was conducted in healthy volunteers (male or female) aged 18 to 55 years with a body mass index of 18.5 to 30.0 kg/m(2). The study consisted of 2 periods separated by a minimum washout period of 14 days. After an overnight fast, volunteers received a single oral dose of 25 mg (5 × 5 mg tablets) warfarin on Day 1 of Period 1 and Day 7 of Period 2. Volunteers received oral doses of 200 mg (2 × 100 mg tablets) roxadustat on Days 1, 3, 5, 7 (concomitant with warfarin), 9, 11, 13, and 15 of Period 2. Plasma S- and R-warfarin (unbound and total concentrations) and prothrombin time were determined at multiple time points up to 216 hours postdose. Pharmacokinetic and pharmacodynamic parameters were estimated via noncompartmental methods. Tolerability was evaluated by monitoring adverse events, laboratory assays, vital signs, and 12-lead ECGs. FINDINGS The geometric mean ratios and 90% CIs for Cmax and AUC∞ of total and unbound S- and R-warfarin (with and without roxadustat) were within the standard bioequivalence interval of 80.00% to 125.00%. Roxadustat increased the geometric mean (GM) prothrombin (PT) and international normalized ratio (INR) AUC from time zero to last measurable sample (AUCPT,last and AUCINR,last) by 24.4%. Coadministration of roxadustat and warfarin in healthy volunteers was associated with a favorable tolerability profile, with most treatment-associated adverse events mild in severity. IMPLICATIONS Based on the lack of clinically significant pharmacokinetic interactions and the limited influence on warfarin pharmacodynamic parameters, no dose adjustment of warfarin should be required when coadministered with roxadustat. ClinicalTrials.gov identifier: NCT02252731.