Sustained Reduction of Elevated Intact Parathyroid Hormone Concentrations with Extended-Release Calcifediol Slows Chronic Kidney Disease Progression in Secondary Hyperparathyroidism Patients

Introduction: Chronic kidney disease (CKD) drives onerous human and healthcare costs, underscoring an urgent need to avert disease progression. Secondary hyperparathyroidism (SHPT) develops as CKD advances, and persistently elevated parathyroid hormone (PTH) may be nephrotoxic and associated with earlier dialysis onset. This study examines, for the first time, the hypothesis that sustained reduction of elevated intact PTH (iPTH) with extended-release calcifediol (ERC) reduces the nephrotoxic impact of SHPT and forestalls renal decline. Methods: Changes in estimated glomerular filtration rate (eGFR) were analyzed post hoc in 126 adults with SHPT, stage 3-4 CKD, and low serum 25-hydroxyvitamin D (25D) treated for 1 year with ERC in pivotal trials. ERC was administered at 30 mu g/day increasing, as needed, to 60 mu g/day to achieve >= 30% reductions in iPTH. Calcium, phosphorus, 25D, 1,25-dihydroxyvitamin D (1,25D), iPTH, eGFR, fibroblast growth factor-23 (FGF23), bone turnover markers (BTMs), and urine albumin-to-creatinine ratio (uACR) were measured at baseline and regular intervals. Participants were categorized by achievement (or not) of sustained >= 30% iPTH reductions over the last 2 quarters of treatment to evaluate differences in eGFR decline. Results: For all participants, 25D increased 58.5 +/- 2.3 (SE) ng/mL (p < 0.001) by the end of treatment (EOT), 1,25D increased 10.1 +/- 1.8 pg/mL (p < 0.001), iPTH decreased from 143.8 +/- 5.8 pg/mL to 108.8 +/- 7.2 (p < 0.001), BTMs improved (p < 0.01), and eGFR declined 2.2 +/- 0.5 mL/min/1.73 m(2) (p < 0.001). The rate of eGFR decline was >5-fold higher (p = 0.014) in participants who did not achieve sustained iPTH reductions of >= 30% (3.2 +/- 0.7; 12.7 +/- 2.2%) than in those who did (0.6 +/- 0.8; 2.9 +/- 2.4%). It was highest in the 30 participants who did not exhibit an iPTH lowering response in both of the last 2 quarters of treatment (5.4 +/- 0.9; 20.9 +/- 3.4%). Duration of iPTH reduction had no impact on safety parameters. Degree of iPTH reduction at EOT was also associated with slower CKD progression. Conclusion: Sustained reduction of elevated iPTH with ERC treatment was associated with slower rates of eGFR decline in patients with SHPT and stage 3-4 CKD without raising safety concerns. A prospective trial is warranted to confirm this finding.