Mechanism Of Action
D3) is a prohormone of the active form of vitamin D3, calcitriol
(1,25-dihydroxyvitamin D3). Calcifediol is converted to calcitriol by
cytochrome P450 27B1 (CYP27B1), also called 1-alpha hydroxylase, primarily in
the kidney. Calcitriol binds to the vitamin D receptor in target tissues and
activates vitamin D responsive pathways that result in increased intestinal
absorption of calcium and phosphorus and reduced parathyroid hormone synthesis.
In repeat-dose clinical studies
with RAYALDEE, increased levels of serum total 25hydroxyvitamin D were
associated with corresponding increases in serum total 1,25-dihydroxyvitamin D
concentrations and reductions in circulating plasma intact PTH observed within
the first two weeks of RAYALDEE treatment [see Clinical Studies].
No food effect study was
conducted with 30 mcg and 60 mcg doses of RAYALDEE. However, a food effect
study with a supratherapeutic dose of 450 mcg in healthy subjects showed an
approximately 5-fold increase in maximum serum calcifediol concentration (Cmax)
and a 3.5-fold increase in AUC0-t when RAYALDEE was administered with a high
fat, high calorie meal compared to fasting.
Exposure to calcifediol
increased proportionally over the dose range of 30 to 90 mcg following repeated
daily administration of RAYALDEE at bedtime to subjects with secondary
hyperparathyroidism, chronic kidney disease and vitamin D insufficiency.
Steady-state levels of serum total 25-hydroxyvitamin D are reached after
approximately 3 months [see Clinical Studies].
Calcifediol is extensively
bound to plasma proteins (>98%). The mean apparent volume of distribution is
8.8 L in healthy subjects following a single oral dose of RAYALDEE, and 30.1 L
in subjects with stage 3 or 4 chronic kidney disease following repeated dosing.
The mean elimination half-life
of calcifediol is approximately 11 days in healthy individuals following a
single dose of RAYALDEE, and approximately 25 days in patients with stage 3 or
stage 4 chronic kidney disease following repeated once daily dosing.
Production of calcitriol from
calcifediol is catalyzed by the 1-alpha-hydroxylase enzyme, CYP27B1, located in
the kidney and other tissues. CYP24A1, located in all vitamin D-responsive
tissues, catabolizes both calcifediol and calcitriol to inactive metabolites.
Excretion of calcifediol occurs
primarily through the biliary fecal route.
Age, Gender And Race
Based on a population
pharmacokinetic analysis, age, gender and race had no meaningful impact on
steady-state concentrations of calcifediol following RAYALDEE administration.
The pharmacokinetics of
RAYALDEE have not been investigated in patients with hepatic impairment.
Based on the population
pharmacokinetics analysis, there was no meaningful difference in calcifediol
steady-state concentrations following repeated RAYALDEE administration in
patients with stage 3 or stage 4 chronic kidney disease.
The efficacy and safety of RAYALDEE were evaluated in two
identical multicenter, randomized, placebo-controlled, double-blind trials in
patients with secondary hyperparathyroidism, stage 3 or 4 chronic kidney
disease and serum total 25-hydroxyvitamin D levels between 10 and 30 ng/mL.
Subjects were stratified by chronic kidney disease stage and randomized in a
2:1 ratio to receive RAYALDEE or a matching placebo at bedtime over 26 weeks.
The dose of RAYALDEE was 30 mcg once daily for the first 12 weeks and either 30
or 60 mcg once daily for the last 14 weeks. The dose was increased to 60 mcg at
the start of week 13 if the plasma intact PTH level was greater than 70 pg/mL,
the serum 25-hydroxyvitamin D level was less than 65 ng/mL and the serum
calcium level was less than 9.8 mg/dL.
A total of 213 subjects were randomized in one trial (72
received placebo and 141 received RAYALDEE), and 216 subjects were randomized
in the second trial (72 received placebo and 144 received RAYALDEE). The
subjects' mean age was 66 years (range 25-85), 50% were male, 65% White, 32%
African-American or Black and 3% Other. At baseline, subjects had secondary
hyperparathyroidism, and stage 3 (52%) or stage 4 (48%) chronic kidney disease
without macroalbuminuria. The most common causes of chronic kidney disease were
diabetes and hypertension and the mean estimated GFR was 31 mL/min/1.73m² .
Mean baseline intact PTH was 130 pg/mL for subjects with stage 3 disease
(n=222) and 166 pg/mL for subjects with stage 4 disease (n=207). Mean serum
calcium was 9.2 mg/dL, mean serum phosphorus was 3.7 mg/dL and mean serum
25-hydroxyvitamin D was 20 ng/mL. Of the 429 subjects randomized, 354 (83%)
completed the studies.
The primary analysis compared the proportion of
individuals who experienced an at least 30% reduction in plasma intact PTH from
baseline to end of trial (average of weeks 20, 22, 24 and 26). A larger
proportion of patients randomized to RAYALDEE experienced an at least 30%
reduction in plasma intact PTH from baseline compared to placebo in both trials
[33% versus 8% in the first trial (P<0.001) and 34% versus 7% in the second
A description of mean (SE) percent change in plasma
intact PTH from baseline across study visits in the two trials combined is
shown in Figure 1. Serum total 25-hydroxyvitamin D levels increased to at least
30 ng/mL in 80% and 83% of subjects treated with RAYALDEE vs. 3% and 7% of
subjects treated with placebo (P<0.001) in the two studies, respectively.
Average steady-state 25-hydroxyvitamin D levels were 50 and 56 ng/mL for
subjects receiving 30 mcg daily, and 69 and 67 ng/mL for subjects receiving 60
mcg daily, in the first and second studies, respectively.
Figure 1: Mean (±SE) Percent Change from Baseline in
Plasma Intact PTH in the Per Protocol Populations (Pooled Data from Two Phase 3
The Per Protocol (PP)
population consisted of all subjects with at least 2 intact PTH values in the
calculated baseline and EAP values and who did not have a major protocol
deviation during the treatment period of the study. The PP population comprised
83% of randomized subjects.