Safety and Efficacy of Recombinant Human Parathyroid Hormone in Adults With Hypoparathyroidism Randomly Assigned to Receive Fixed 25-μg or 50-μg Daily Doses

Purpose The present study examined the efficacy and safety of a lower rhPTH(1–84) dose. Methods RELAY was a dose-blinded, multicenter, 8-week study of patients with hypoparathyroidism randomized to fixed 25- or 50-μg/d doses of subcutaneous rhPTH(1–84). The primary end point was the percentage of patients at week 8 with supplement reductions in calcium to ≤500 mg/d and in calcitriol to ≤0.25 μg/d, while maintaining serum calcium levels between 1.875 mmol/L and the upper limit of normal. The secondary end point was the percentage of patients at week 8 with a ≥50% reduction in calcium and calcitriol doses, while maintaining serum calcium levels between 1.875 mmol/L and the upper limit of normal. Findings Forty-two patients were randomized (25-μg group, n = 19; 50-μg group, n = 23). At week 8, the primary end point was achieved by 4 (21%; 95% CI, 6%–46%) and 6 (26%; 95% CI, 10%–48%) of the patients receiving 25 and 50 μg/d of rhPTH(1–84), respectively. The secondary end point was achieved by 2 (11%; 95% CI, 1%–33%) and 6 (26%; 95% CI, 10%–48%) of the patients receiving 25 and 50 μg/d of rhPTH(1–84), respectively. Treatment-emergent adverse events were reported by 11 (58%) patients in the 25-μg group and 17 (74%) patients in the 50-μg group. Implications Doses as low as 25 µg/d of rhPTH(1–84) are well tolerated and may be effective for a subset of patients. ClinicalTrials.gov identifier: NCT01268098.