OR10-05 Efficacy and Safety of Palopegteriparatide Treatment in Adults With Hypoparathyroidism: 3-Year Results From The Phase 3 PaTHway Trial

Abstract Disclosure: A.A. Khan: Alexion Pharmaceuticals, Inc., Amgen Inc, Amolyt Pharma, Ascendis Pharma. B.L. Clarke: Amolyt Pharma, Ascendis Pharma, EnteraBio, Extend Bio, Takeda. M.R. Rubin: Ascendis Pharma, MBX Biosciences. P.E. Schwarz: Aventis Pharmaceuticals, Genmab, Novo Nordisk. D.M. Shoback: Ascendis Pharma. C. Gagnon: Amgen Inc, Ascendis Pharma, Novo Nordisk, Shire, Takeda. A. Palermo: None. L.G. Abbott: Abbott Laboratories, Ascendis Pharma, Clarus, Shire, Takeda. L. Kohlmeier: Amgen Inc, Ascendis Pharma, Radius Health, Inc. E. Tsourdi: Alexion Pharmaceuticals, Inc., Ascendis Pharma, Kyowa Kirin, Takeda, UCB. F. Cetani: None. R. Jain: Amgen Inc, Ascendis Pharma. C. Zhao: Ascendis Pharma. B. Lai: Ascendis Pharma. M.A. Makara: Ascendis Pharma. J. Ukena: Ascendis Pharma. C.T. Sibley: Ascendis Pharma. A.D. Shu: Ascendis Pharma. L. Rejnmark: Amolyt Pharma, Ascendis Pharma, BridgeBio, Kyowa Kirin, Takeda. Background: Hypoparathyroidism is an endocrine disease caused by insufficient levels of parathyroid hormone (PTH) and is associated with reduced quality of life and a high comorbidity burden. Conventional therapy for hypoparathyroidism (active vitamin D and elemental calcium) aims to alleviate hypocalcemia but does not address insufficient PTH and may increase the risk of renal complications. Palopegteriparatide is a prodrug of PTH(1-34), administered subcutaneously once daily, designed to provide active PTH within the physiological range for 24 hours/day. It is approved by the Food and Drug Administration, European Commission, and Medicines and Healthcare products Regulatory Agency. This analysis evaluated the long-term efficacy and safety of palopegteriparatide in adults with chronic hypoparathyroidism through week 156 of the PaTHway trial. Methods: PaTHway is a phase 3 trial with a 26-week randomized, double-blind, placebo-controlled period followed by an ongoing open-label extension period. Serum biochemistries were assessed at baseline and regular intervals. Renal function was assessed by estimated glomerular filtration rate (eGFR). Safety assessments included 24-hour urine calcium and treatment-emergent adverse events (TEAEs). Results: At week 156, 89% (73/82) of participants remained in the trial; of those, 96% were independent from conventional therapy (no active vitamin D and ≤600 mg/day elemental calcium) and 88% had normal albumin-adjusted serum calcium levels (8.3-10.6 mg/dL) with a mean (SD) of 8.9 (0.6) mg/dL. Mean (SD) serum phosphate (3.4 [0.6] mg/dL) and calcium x phosphate product (30.6 [5.4] mg2/dL2) levels remained within normal ranges through week 156. Mean (SD) eGFR at week 156 was 78.0 (14.5) mL/min/1.73 m2, reflecting a mean (SD) increase of 8.8 (11.9) mL/min/1.73 m2 from baseline (P<0.0001); 59% and 43% of participants had an increase in eGFR of ≥5 mL/min/1.73 m2 and ≥10 mL/min/1.73 m2, respectively. Among participants with baseline eGFR <60 mL/min/1.73 m2 (n=23), the mean (SD) increase in eGFR was 14.0 (8.9) mL/min/1.73 m2 from baseline to week 156. Mean (SD) 24-hour urine calcium levels normalized with palopegteriparatide treatment, remaining below the upper limit of normal (≤250 mg/day) through week 156 (162.1 [117.8] mg/day). TEAEs were mostly grade 1 or 2, with no new safety signals identified. Conclusion: Through year 3 of the PaTHway trial, retention rate was high and palopegteriparatide demonstrated consistent longer-term safety and efficacy, which included the maintenance of serum and urine biochemistries within normal levels and sustained improvement in renal function. Presentation: Saturday, July 12, 2025