In Reply Dr Hai and colleagues are concerned that the starting dose of etelcalcetide was 5 mg (not the lowest dose) whereas the starting dose of cinacalcet was 30 mg (the lowest dose). This clinical trial, using a double-dummy active control, dosed cinacalcet in strict accordance with the approved package insert and in a manner consistent with previous clinical trials of similar duration using similar biochemical end points.1,2 Our finding of a mean decrease in PTH of approximately 40% over 26 weeks in patients treated with cinacalcet is similar to findings of the phase 3 trials with cinacalcet (43% decrease in mean PTH over 26 weeks).1 The dosing of etelcalcetide was approved by the US Food and Drug Administration. Because cinacalcet and etelcalcetide are different drugs, there is no a priori reason to believe that their dosing schemes should be identical.
Block GA, Chertow GM. Dosing of Etelcalcetide vs Cinacalcet for Secondary Hyperparathyroidism—Reply. JAMA. 2017;317(20):2132–2133. doi:10.1001/jama.2017.4746
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