A Phase 2 Study to Evaluate the Safety and Efficacy of VS-505(AP301) to Treat Hyperphosphatemia in Hemodialysis Patients

Inclusion Criteria: * Adults with end stage renal disease who are receiving a stable hemodialysis regimen (3 times per week) with sufficient dialysis adequacy; * Serum phosphorus level range from \>1.94 mmol/L (6.0 mg/dL) to ≤3.23 mmol/L (10.0 mg/dL) at the end of washout phase. Exclusion Criteria: * Kidney transplant patient or scheduled kidney transplant, or change to peritoneal dialysis, home hemodialysis or plan to relocate to another dialysis center during the study period； * Serum phosphorus level is \<1.29 mmol/L（4.0 mg/dL) or \>2.42 mmol/L（7.5 mg/dL) at screening, or documented to be \>3.23 mmol/L（10 mg/dL) within the latest three month prior to screening (screening included); * Serum calcium level is \<8 mg/dL or \>11 mg/dL at the screening; * Serum immunoreactive parathyroid hormone (iPTH)\>1000 pg/mL at the screening; * History of hemochromatosis or serum ferritin value ≥1000 μg/L at screening； * Current clinically significant gastrointestinal (GI) disorder, or history of intestine obstruction, gastrectomy or duodenectomy, or GI tract surgery within 12 weeks prior to screening; * Poorly controlled hypertension, cardiovascular disorders, and history of cerebrovascular disease or cardiovascular disease event within 24 weeks (6 months) prior to screening.