This is a phase 1, open-label study in two sites. There will be four different renal function groups.~For all subjects:~Subjects will be allocated to the normal and severely impaired renal function groups based on estimated glomerular filtration rate (eGFR), calculated with the abbreviated modification of diet in renal disease (MDRD) equation. The eGFR will be based on the serum creatinine concentration and is assessed at screening and at day -2. The eGFR obtained at screening will determine the allocation.~Subjects will be allocated to the ESRD groups based on their dialysis requirements.~Subjects with normal and severely impaired renal function, and subjects with ESRD on CAPD or APD:~Screening will take place from day -30 to day -3 and the subjects will be admitted to the clinical unit on day -2. The treatment period lasts 8 days, during which the subjects will receive a single oral dose of roxadustat in the morning of day 1 Subjects will complete the treatment period on day 6, provided that all required assessments have been performed and there are no medical reasons for a prolonged follow-up. The study will be completed with an end-of-study visit (ESV), which will take place between 5 and 9 days after the last treatment period-defined assessment (or after early withdrawal).~Subjects with ESRD on HD or HDF:~Screening will take place from day -30 to day -3 and subjects will complete 2 treatment periods of 8 days (period 1) and 7 days (period 2) in order to evaluate the pharmacokinetics of roxadustat with a single oral dose of roxadustat on day 1 of both periods after and before dialysis.~Subjects will complete the treatment period 1 on day 6 followed by a wash-out period which is minimally 1 week and maximally 3 weeks. Subjects will complete period 2 on day 6, provided that all required assessments have been performed and there are no medical reasons for a prolonged follow-up. The study will be completed with an end-of-study visit (ESV), which will take place between 5 and 9 days after the last treatment period-defined assessment (or after early withdrawal).~All subjects:~Safety assessments will be performed throughout the study. An optional biobanking sample may be taken for potential exploratory, retrospective, gene polymorphism analysis. Roxadustat plasma, urine, and dialysate samples will be stored for potential exploratory metabolic profiling or exploratory biomarker analysis after the study.
For subjects with normal renal function or severely impaired renal function, this study will evaluate the pharmacokinetics of roxadustat and its main metabolites in plasma and urine.~For subjects with end stage renal disease (ESRD) on continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD), this study will evaluate the pharmacokinetics of roxadustat and its main metabolites in plasma, urine and dialysate.~For subjects with ESRD on hemodialysis (HD) or hemodiafiltration (HDF), this study will evaluate the pharmacokinetics of roxadustat and its main metabolites in plasma, urine and dialysate and also the effect of dialysis on the pharmacokinetics of roxadustat and its main metabolites.