Astellas Pharma Europe BV

Roxadustat is an orally active hypoxia-inducible factor prolyl hydroxylase inhibitor for anemia in chronic kidney disease. The pharmacokinetics, metabolic profile, and pharmacodynamics of roxadustat were investigated in subjects with different degrees of kidney function.

This phase 1 open-label study enrolled subjects with normal and severely impaired kidney function, and end-stage renal disease (ESRD) on continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD) or hemodialysis/hemodiafiltration (HD/HDF). All subjects received a single 100-mg dose of oral roxadustat. Within a single-sequence, two-treatment period design (P1/P2), subjects with ESRD on HD/HDF received roxadustat 2 h after (P1) and 2 h before (P2) a dialysis session. Area under the plasma concentration-time curve (AUC) from administration to infinity (AUC_inf), maximum concentration (C_max), and terminal elimination half-life (t_1/2) were assessed for roxadustat; AUC and C_max were assessed for erythropoietin.

Thirty-four subjects were enrolled and received roxadustat (normal kidney function, n = 12; severely impaired kidney function, n = 9; ESRD on CAPD/APD, n = 1; ESRD on HD/HDF, n = 12). The geometric least-square mean ratio of AUC_inf was 223% and 195% in subjects with severely impaired kidney function and ESRD on HD/HDF, respectively, relative to subjects with normal kidney function; C_max and t_1/2 were comparable. The pharmacokinetic profile of roxadustat was not affected by HD/HDF. AUC_inf and t_1/2 for the metabolites of roxadustat increased in subjects with kidney impairment. The AUC and C_max of erythropoietin increased in subjects with severely impaired kidney function or ESRD on HD/HDF. Roxadustat was well tolerated.

Kidney function impairment increased the AUC of roxadustat and its metabolites. The C_max and t_1/2 of roxadustat were comparable among groups. Roxadustat and its metabolites were not cleared by HD/HDF. Clinical Trials Registration Number: NCT02965040.

ASP8477 (molecular weight 325.36 g/mol) is a fatty acid amide hydrolase inhibitor intended for the treatment of neuropathic pain. Results from in vitro studies indicated that ASP8477 is a direct inhibitor of cytochrome P450 (CYP) 2C8, 2C9, 2C19, 2D6, and 3A4 enzymes at expected efficacious concentrations, with the strongest effect on CYP2C19; a phase 1 study confirmed ASP8477 to be a CYP2C19 inhibitor. To further evaluate the interaction potential of ASP8477, a cocktail interaction study was performed using the probe substrates of the validated Inje cocktail containing losartan (CYP2C9), omeprazole (CYP2C19), dextromethorphan (CYP2D6), and midazolam (CYP3A4). Because ASP8477 shows nonlinear pharmacokinetics, 3 doses (20, 60, and 100 mg) were evaluated. This study revealed changes in exposure (area under the concentration-time curve) of the probe substrates after treatment with 20, 60, and 100 mg ASP8477, respectively, compared with substrates alone with geometric mean ratios of: midazolam, 119%, 151%, and 158%; losartan, 107%, 144%, and 190%; omeprazole, 213%, 456%, and 610%; and dextromethorphan, 138%, 340%, and 555% (with increasing doses, respectively). Overall, ASP8477 was a weak inhibitor for CYP3A4 and CYP2C9, a moderate to strong inhibitor for CYP2C19, and a weak to strong inhibitor for CYP2D6, with doses from 20 to 100 mg. This study confirmed that the Inje cocktail approach was able to detect relevant drug-drug interactions impacting further development of ASP8477 and future therapeutic use. With the approach used here, the inhibiting effect of a perpetrator drug on different CYP enzymes can be evaluated, and at different doses, thereby supporting dose recommendations for potential interactions.

Mirabegron is the first registered β3-adrenoceptor agonist for treatment of overactive bladder as an alternative to antimuscarinics. Previously four liquid chromatography-tandem mass spectrometry assays were published to determine mirabegron and eight metabolites (M5, M8, M11-M16) in human plasma. In order to support paediatric development, the assays were further optimized to reduce the required blood volume and increase the sensitivity. The assays were miniaturized by using 96-well supported liquid extraction plates (mirabegron, M5, M16) or 96-well mixed-mode cation exchange solid phase extraction plates (M8, M11-M15) and a more sensitive MS-system was used. For the analytes, up to fivefold increase in assay sensitivity was achieved. The required blood sample volume was reduced from 10 to 2 mL for each timepoint. Validation demonstrated that the assays were accurate, precise and selective in the determination of mirabegron and metabolites. The assays were successfully applied to evaluate the pharmacokinetics of mirabegron in a paediatric population.