Extended-release calcifediol for secondary hyperparathyroidism in Chinese adults with stage 3 or 4 chronic kidney disease: a randomized trial

Technical Summary: Extended-release Calcifediol for Secondary Hyperparathyroidism in Chinese Adults with Stage 3 or 4 Chronic Kidney Disease

Problem Statement
Secondary hyperparathyroidism (SHPT) is a prevalent and serious complication of chronic kidney disease (CKD), driving bone disease, vascular calcification, and increased cardiovascular risk. In China, SHPT affects an estimated 85% of CKD patients, a high prevalence largely attributed to widespread vitamin D insufficiency (VDI). While current guidelines recommend monitoring VDI, they rely on sufficiency thresholds (20–30 ng/mL) derived from the general population. Previous randomized controlled trials (RCTs) in the United States demonstrated that achieving clinically meaningful reductions in intact parathyroid hormone (iPTH) in CKD patients requires substantially higher serum 25-hydroxyvitamin D (25D) concentrations than those achievable with standard dietary supplements. However, it remained unknown whether these higher 25D targets were necessary for similar iPTH suppression in the Chinese population, creating a critical evidence gap for clinical management in China.

Methodology
This study was a multi-center, randomized, double-blind, placebo-controlled, parallel-group trial conducted across 38 clinical sites in mainland China.

• Participants: The trial enrolled 100 non-dialysis adults (ages ≥18) with Stage 3 or 4 CKD (eGFR 15–<60 mL/min/1.73m²), elevated iPTH (85–<500 pg/mL), and VDI (serum 25D 10–<30 ng/mL).
• Intervention: Participants were randomized 2:1 to receive daily oral extended-release calcifediol (ERC) or a matching placebo for 26 weeks.
• Dosing Strategy: Treatment began at 30 µg/day. After 12 weeks, the dose could be titrated to 60 µg/day if necessary to achieve a ≥30% reduction in iPTH while maintaining safety.
• Endpoints:
  • Primary: The proportion of participants achieving a mean ≥30% reduction from baseline in plasma iPTH during the last 6 weeks of treatment (Weeks 20–26).
  • Secondary: The proportion achieving a mean serum 25D level of ≥30 ng/mL.
  • Safety: Monitored serum calcium, phosphorus, urine calcium:creatinine ratio, eGFR, and adverse events.
• Analysis: Efficacy was analyzed in the modified intent-to-treat (mITT) population (n=98) and per-protocol (PP) population. Statistical comparisons utilized chi-square tests for proportions and t-tests for continuous variables.

Key Results

• Efficacy on iPTH: The primary endpoint was met with high statistical significance. In the mITT population, 53.0% of participants in the ERC group achieved the target ≥30% reduction in iPTH, compared to only 6.3% in the placebo group (p < 0.0001). This result was consistent in the per-protocol population (55.7% vs. 7.4%).
• Efficacy on 25D Levels: ERC effectively corrected VDI. 90.9% of the ERC-treated mITT population achieved serum 25D levels ≥30 ng/mL, compared to 9.4% in the placebo group (p < 0.0001). Mean serum 25D in the ERC group rose from a baseline of 17.4 ng/mL to a steady-state level of 93.9 ng/mL during the efficacy assessment period.
• Safety: No clinically meaningful differences in safety parameters were observed between groups.
  • Serum calcium increased slightly in the ERC group (mean +0.10 mg/dL) versus a decrease in the placebo group, but confirmed hypercalcemia occurred in only 3% of ERC participants.
  • No significant differences were found in serum phosphorus, urine calcium:creatinine ratios, or eGFR trends between groups.
  • Adverse event profiles were comparable, with the majority of events being mild to moderate and unrelated to treatment.
• Subgroup Analysis: The efficacy of ERC in reducing iPTH and raising 25D was consistent across CKD stages (3 vs. 4), gender, age, and BMI.

Significance and Claims
The paper claims that this trial provides the first evidence that extended-release calcifediol (ERC) is both well-tolerated and effective for treating SHPT in Chinese adults with Stage 3 or 4 CKD and VDI. The study demonstrates that, similar to findings in US populations, Chinese patients require higher serum 25D concentrations to achieve significant iPTH suppression. The authors posit that these elevated 25D levels are necessary to engage extrarenal CYP27B1 enzymes (found in tissues like the parathyroid glands) to produce active 1,25-dihydroxyvitamin D, compensating for the loss of renal hydroxylase activity in advanced CKD.

The authors conclude that the observed treatment responses in this Chinese cohort are consistent with previous US RCTs, supporting the use of ERC as a therapeutic option for SHPT in this specific demographic. They note that while the study confirms efficacy and safety, limitations such as the sample size and treatment duration necessitate larger, longer-term trials to fully clarify the impact of iPTH reduction on long-term clinical outcomes. The study does not claim to establish new safety thresholds beyond what was observed but rather validates the applicability of the ERC mechanism in the Chinese population.