IV calcimimetic · dialysis PTH control
Etelcalcetide is a short synthetic peptide, built mostly from D-amino acids, that lowers parathyroid hormone (PTH) in people on hemodialysis whose kidney failure has pushed the parathyroid glands into overactivity, a condition called secondary hyperparathyroidism. Marketed as Parsabiv, it is given intravenously at dialysis, unlike the oral calcimimetic cinacalcet.
Parathyroid cells sense blood calcium through the calcium-sensing receptor (CaSR). When the receptor detects enough calcium, the cells release less PTH; when calcium is low, PTH output rises. In chronic kidney disease, mineral balance is disturbed and PTH can stay persistently high, which contributes to calcification outside the skeleton and is associated with higher mortality2. Etelcalcetide binds the CaSR and makes it more responsive to the calcium already present, an allosteric effect3. The gland then behaves as if calcium were higher than it is and releases less PTH. Blood calcium falls as well, which is the source of its main risk3.
Approval rested on human trials in hemodialysis patients. Two parallel 26-week phase 3 trials randomized 1,023 people with moderate to severe secondary hyperparathyroidism to etelcalcetide or placebo. About three in four on etelcalcetide achieved a greater than 30 percent PTH reduction, versus fewer than one in ten on placebo, and about half reached a secondary PTH target; muscle spasms, nausea and vomiting were more common with the drug1.
A double-blind, double-dummy trial in 683 patients compared it head-to-head with oral cinacalcet: etelcalcetide was non-inferior and also met superiority criteria for PTH lowering (68 versus 58 percent achieving a greater than 30 percent drop), while decreased blood calcium was the most common adverse effect in both groups (69 versus 60 percent)2. Both reports say effects on clinical outcomes, and longer-term effects, still need study1,2.
The FDA approved Parsabiv in 2017 for secondary hyperparathyroidism in adults with chronic kidney disease on hemodialysis3. It has not been studied in, and is not recommended for, parathyroid cancer, primary hyperparathyroidism, or kidney disease not treated with hemodialysis.
Low blood calcium is the main risk and can be severe, causing tingling, muscle cramps or spasms, seizures, QT prolongation and abnormal heart rhythms. The label also warns of possible worsening heart failure, upper gastrointestinal bleeding in people at risk, and adynamic (low-turnover) bone if PTH is suppressed too far. The most common reactions (5% or more) were decreased blood calcium, muscle spasms, diarrhea, nausea, vomiting, headache and paresthesia. Allergic reactions, including facial swelling and anaphylaxis, have occurred3.
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