This is a single-center, prospective, dose-escalation, pilot study in 15 end-stage renal disease patients on chronic hemodialysis with secondary hyperparathyroidism.

Fifteen prevalent and stable hemodialysis patients with secondary hyperparathyroidism eligible for treatment with calcium receptor sensitizers according to current KDIGO will be included.

Study phases will begin and end on the day of the first hemodialysis session of the week.

The run-in phase will last 4 weeks. No calcimimetics will be prescribed during the run-in phase.

The treatment phase starts with a dose of etelcalcetide is 2.5mg thrice weekly. Etelcalcetide dose will be escalated every 4 weeks in 2.5mg/dialysis session increments to a maximum dose of 15mg thrice weekly.

The wash-out Phase starts after completion of the 15mg thrice-weekly phase or in case a pre-specified safety endpoint is reached, etelcalcetide will be discontinued and patients will be followed for additional 8 weeks to study any potential reversibility of PTH lowering on T50 results.

For the individual patient, the study duration will be 9 months

Inclusion Criteria:

• Prevalent patients (≥ 3 months on dialysis) treated with thrice weekly hemodialysis (HD) or hemodiafiltration (HDF)
• Secondary hyperparathyroidism defined as PTH levels > 9x ULN according to current KDIGO guidelines if therapy-naïve, or patients already treated with calcium receptor sensitizers with PTH > 2x ULN
• Albumin corrected calcium ≥ 2,08 mmol/l
• Calcium concentrations of dialysate stable for at least 2 weeks prior to screening

Exclusion Criteria:

• Currently receiving treatment in another investigational device or drug study or participation in non-interventional studies
• Current treatment with etelcalcetide (Parsabiv©) or treatment with etelcalcetide within 3 months prior to study inclusion
• Patient has known sensitivity to any of the products or components of Parsabiv©
• Patient has received a parathyroidectomy
• Parathyroidectomy planned or expected during the study period
• Elective kidney transplant scheduled during the study period
• Therapy with bisphosphonates within the past 12 months
• Therapy with denosumab within the past 6 months
• Antacids containing aluminum, calcium, magnesium or bicarbonate
• Patient has a history of symptomatic ventricular arrhythmias or Torsades de Pointes
• Patient has a history of myocardial infarction, coronary angioplasty, or coronary arterial bypass grafting within the past 6 months prior to screening.
• Pregnant or nursing (lactating) women