Paricalcitol 2 ug Capsule, Liquid Filled, 30-count — NDC 65862-937-30 (Billing 65862-0937-30)

12 CLINICAL PHARMACOLOGY Secondary hyperparathyroidism is characterized by an elevation in parathyroid hormone (PTH) associated with inadequate levels of active vitamin D hormone. The source of vitamin D in the body is from synthesis in the skin as vitamin D 3 and from dietary intake as either vitamin D 2 or D 3 . Both vitamin D 2 and D 3 require two sequential hydroxylations in the liver and the kidney to bind to and to activate the vitamin D receptor (VDR).

The endogenous VDR activator, calcitriol [1,25(OH) 2 D 3 ], is a hormone that binds to VDRs that are present in the parathyroid gland, intestine, kidney, and bone to maintain parathyroid function and calcium and phosphorus homeostasis, and to VDRs found in many other tissues, including prostate, endothelium and immune cells. VDR activation is essential for the proper formation and maintenance of normal bone. In the diseased kidney, the activation of vitamin D is diminished, resulting in a rise of PTH, subsequently leading to secondary hyperparathyroidism and disturbances in the calcium and phosphorus homeostasis.

Decreased levels of 1,25(OH) 2 D 3 have been observed in early stages of chronic kidney disease. The decreased levels of 1,25(OH) 2 D 3 and resultant elevated PTH levels, both of which often precede abnormalities in serum calcium and phosphorus, affect bone turnover rate and may result in renal osteodystrophy.

12.1Mechanism of Action Paricalcitol is a synthetic, biologically active vitamin D 2 analog of calcitriol. Preclinical and in vitro studies have demonstrated that paricalcitol's biological actions are mediated through binding of the VDR, which results in the selective activation of vitamin D responsive pathways. Vitamin D and paricalcitol have been shown to reduce parathyroid hormone levels by inhibiting PTH synthesis and secretion.

12.2Pharmacodynamics Paricalcitol decreases serum intact parathyroid hormone (iPTH) and increases serum calcium and serum phosphorous in both HD and PD patients. This observed relationship was quantified using a mathematical model for HD and PD patient populations separately. Computer-based simulations of 100 trials in HD or PD patients (N = 100) using these relationships predict slightly lower efficacy (at least two consecutive ≥ 30% reductions from baseline iPTH) with lower hypercalcemia rates (at least two consecutive serum calcium ≥ 10.5 mg/dL) for lower iPTH-based dosing regimens.

Further lowering of hypercalcemia rates was predicted if the treatment with paricalcitol is initiated in patients with lower serum calcium levels at screening. Based on these simulations, a dosing regimen of iPTH/80 with a screening serum calcium ≤ 9.5 mg/dL, approximately 76.5% (95% CI: 75.6% to 77.3%) of HD patients are predicted to achieve at least two consecutive weekly ≥ 30% reductions from baseline iPTH over a duration of 12 weeks. The predicted incidence of hypercalcemia is 0.8% (95% CI: 0.7% to 1%).

In PD patients, with this dosing regimen, approximately 83.3% (95% CI: 82.6% to 84%) of patients are predicted to achieve at least two consecutive weekly ≥ 30% reductions from baseline iPTH. The predicted incidence of hypercalcemia is 12.4% (95% CI: 11.7% to 13%) [see Clinical Studies (14.2) and Dosage and Administration (2.2) ] .

12.3Pharmacokinetics Absorption The mean absolute bioavailability of paricalcitol capsules under low-fat fed condition ranged from 72% to 86% in healthy adult volunteers, CKD Stage 5 patients on HD, and CKD Stage 5 patients on PD. A food effect study in healthy adult volunteers indicated that the C max and AUC 0-∞ were unchanged when paricalcitol was administered with a high fat meal compared to fasting. Food delayed T max by about 2 hours.

The AUC 0-∞ of paricalcitol increased proportionally over the dose range of 0.06 to 0.48 mcg/kg in healthy adult volunteers. Distribution Paricalcitol is extensively bound to plasma proteins (≥ 99.8%). The mean apparent volume of distribution following a 0.24 mcg/kg dose of pari… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action Paricalcitol is a synthetic, biologically active vitamin D 2 analog of calcitriol. Preclinical and in vitro studies have demonstrated that paricalcitol's biological actions are mediated through binding of the VDR, which results in the selective activation of vitamin D responsive pathways. Vitamin D and paricalcitol have been shown to reduce parathyroid hormone levels by inhibiting PTH synthesis and secretion.

12.3Pharmacokinetics Absorption The mean absolute bioavailability of paricalcitol capsules under low-fat fed condition ranged from 72% to 86% in healthy adult volunteers, CKD Stage 5 patients on HD, and CKD Stage 5 patients on PD. A food effect study in healthy adult volunteers indicated that the C max and AUC 0-∞ were unchanged when paricalcitol was administered with a high fat meal compared to fasting. Food delayed T max by about 2 hours.

The AUC 0-∞ of paricalcitol increased proportionally over the dose range of 0.06 to 0.48 mcg/kg in healthy adult volunteers. Distribution Paricalcitol is extensively bound to plasma proteins (≥ 99.8%). The mean apparent volume of distribution following a 0.24 mcg/kg dose of paricalcitol in healthy adult volunteers was 34 L.

The mean apparent volume of distribution following a 4 mcg dose of paricalcitol in CKD Stage 3 and a 3 mcg dose in CKD Stage 4 patients is between 44 and 46 L. Metabolism After oral administration of a 0.48 mcg/kg dose of 3 H-paricalcitol, parent drug was extensively metabolized, with only about 2% of the dose eliminated unchanged in the feces, and no parent drug was found in the urine. Several metabolites were detected in both the urine and feces.

Most of the systemic exposure was from the parent drug. Two minor metabolites, relative to paricalcitol, were detected in human plasma. One metabolite was identified as 24(R)-hydroxy paricalcitol, while the other metabolite was unidentified.

The 24(R)-hydroxy paricalcitol is less active than paricalcitol in an in vivo rat model of PTH suppression. In vitro data suggest that paricalcitol is metabolized by multiple hepatic and non-hepatic enzymes, including mitochondrial CYP24, as well as CYP3A4 and UGT1A4. The identified metabolites include the product of 24(R)-hydroxylation, 24,26- and 24,28-dihydroxylation and direct glucuronidation.

Elimination Paricalcitol is eliminated primarily via hepatobiliary excretion; approximately 70% of the radiolabeled dose is recovered in the feces and 18% is recovered in the urine. While the mean elimination half-life of paricalcitol is 4 to 6 hours in healthy adult volunteers, the mean elimination half-life of paricalcitol in CKD Stages 3, 4, and 5 (on HD and PD) patients ranged from 14 to 20 hours. Table 7.

Paricalcitol Capsule Pharmacokinetic Parameters (mean ± SD) in CKD Stages 3, 4, and 5 Adult Patients Pharmacokinetic Parameters (units) CKD Stage 3 n = 15* CKD Stage 4 n = 14* CKD Stage 5 HD** n = 14 CKD Stage 5 PD** n = 8 C max (ng/mL) 0.11 ± 0.04 0.06 ± 0.01 0.575 ± 0.17 0.413 ±

0.06AUC 0-∞ (ng . h/mL) 2.42 ± 0.61 2.13 ± 0.73 11.67 ± 3.23 13.41 ±

5.48CL/F (L/h) 1.77 ± 0.5 1.52 ± 0.36 1.82 ± 0.75 1.76 ±

0.77V/F (L) 43.7 ± 14.4 46.4 ± 12.4 38 ± 16.4 48.7 ± 15.6 t 1/2 16.8 ± 2.65 19.7 ± 7.2 13.9 ± 5.1 17.7 ±

9.6HD: hemodialysis; PD: peritoneal dialysis. * Four mcg paricalcitol capsules were given to CKD Stage 3 patients; three mcg paricalcitol capsules were given to CKD Stage 4 patients. ** CKD Stage 5 HD and PD patients received a 0.24 mcg/kg dose of paricalcitol as capsules. Specific Populations Geriatric The pharmacokinetics of paricalcitol has not been investigated in geriatric patients greater than 65 years [see Use in Specific Populations (8.5) ]. Pediatric Paricalcitol C max, AUC, and t 1/2 values were similar between Stage 3 and Stage 4 CKD pediatric patients 10 to 16 years of age.

Population pharmacokinetic analysis shows that the pharmacokinetics of paricalcitol in Stage 5 CKD pediatric patients appear to be similar to those observed in Stage 3 and Stage 4 pediatric patients. Table 8. Paricalcitol Capsules Pharmacokinetic Parameters (mean ± SD) in CKD Stages 3 and 4 Patients 10 to 16 Years of Age Pharmacokinetic Parameter (units) CKD Stage 3 n = 6 CKD Stage 4 N = 5 C max (ng/mL) 0.12 ± 0.06 0.13 ±

0.05AUC ∞ (ng•h/mL) 2.63 ± 0.76 3.2 ±

0.99CL/F (L/h) 1.23 ± 0.38 1.02 ±

0.35V/F (L) 27.78 ± 18.60 24.36 ± 5.92 t 1/2 (h) 15.0 ± 6.1 17.5 ± 5.9 * Three 1 mcg paricalcitol capsules… [Excerpted — this section continues on DailyMed.]

12.2Pharmacodynamics Paricalcitol decreases serum intact parathyroid hormone (iPTH) and increases serum calcium and serum phosphorous in both HD and PD patients. This observed relationship was quantified using a mathematical model for HD and PD patient populations separately. Computer-based simulations of 100 trials in HD or PD patients (N = 100) using these relationships predict slightly lower efficacy (at least two consecutive ≥ 30% reductions from baseline iPTH) with lower hypercalcemia rates (at least two consecutive serum calcium ≥ 10.5 mg/dL) for lower iPTH-based dosing regimens.

Further lowering of hypercalcemia rates was predicted if the treatment with paricalcitol is initiated in patients with lower serum calcium levels at screening. Based on these simulations, a dosing regimen of iPTH/80 with a screening serum calcium ≤ 9.5 mg/dL, approximately 76.5% (95% CI: 75.6% to 77.3%) of HD patients are predicted to achieve at least two consecutive weekly ≥ 30% reductions from baseline iPTH over a duration of 12 weeks. The predicted incidence of hypercalcemia is 0.8% (95% CI: 0.7% to 1%).

In PD patients, with this dosing regimen, approximately 83.3% (95% CI: 82.6% to 84%) of patients are predicted to achieve at least two consecutive weekly ≥ 30% reductions from baseline iPTH. The predicted incidence of hypercalcemia is 12.4% (95% CI: 11.7% to 13%) [see Clinical Studies (14.2) and Dosage and Administration (2.2) ] .

14 CLINICAL STUDIES

14.1Chronic Kidney Disease Stages 3 and 4 Adults The safety and efficacy of paricalcitol capsules were evaluated in three, 24-week, double blind, placebo-controlled, randomized, multicenter, Phase 3 clinical studies in CKD Stages 3 and 4 patients. Two studies used an identical three times a week dosing design, and one study used a daily dosing design. A total of 107 patients received paricalcitol capsules and 113 patients received placebo.

The mean age of the patients was 63 years, 68% were male, 71% were Caucasian, and 26% were African-American. The average baseline iPTH was 274 pg/mL (range: 145 to 856 pg/mL). The average duration of CKD prior to study entry was 5.7 years.

At study entry 22% were receiving calcium based phosphate binders and/or calcium supplements. Baseline 25-hydroxyvitamin D levels were not measured. The initial dose of paricalcitol capsules was based on baseline iPTH.

If iPTH was ≤ 500 pg/mL, paricalcitol capsules were administered 1 mcg daily or 2 mcg three times a week, not more than every other day. If iPTH was > 500 pg/mL, paricalcitol capsules were administered 2 mcg daily or 4 mcg three times a week, not more than every other day. The dose was increased by 1 mcg daily or 2 mcg three times a week every 2 to 4 weeks until iPTH levels were reduced by at least 30% from baseline.

The overall average weekly dose of paricalcitol capsules was 9.6 mcg/week in the daily regimen and 9.5 mcg/week in the three times a week regimen. In the clinical studies, doses were titrated for any of the following reasons: if iPTH fell to < 60 pg/mL, or decreased > 60% from baseline, the dose was reduced or temporarily withheld; if iPTH decreased < 30% from baseline and serum calcium was ≤ 10.3 mg/dL and serum phosphorus was ≤ 5.5 mg/dL, the dose was increased; and if iPTH decreased between 30 to 60% from baseline and serum calcium and phosphorus were ≤ 10.3 mg/dL and ≤ 5.5 mg/dL, respectively, the dose was maintained.

Additionally, if serum calcium was between 10.4 to 11 mg/dL, the dose was reduced irrespective of iPTH, and the dose was withheld if serum calcium was > 11 mg/dL. If serum phosphorus was > 5.5 mg/dL, dietary counseling was provided, and phosphate binders could have been initiated or increased. If the elevation persisted, the paricalcitol capsules dose was decreased.

Seventy-seven percent (77%) of the paricalcitol capsules treated patients and 82% of the placebo treated patients completed the 24-week treatment. The primary efficacy endpoint of at least two consecutive ≥ 30% reductions from baseline iPTH was achieved by 91% of paricalcitol capsules treated patients and 13% of the placebo treated patients (p < 0.001). The proportion of paricalcitol capsules treated patients achieving two consecutive ≥ 30% reductions was similar between the daily and the three times a week regimens (daily: 30/33, 91%; three times a week: 62/68, 91%).

The incidence of hypercalcemia (defined as two consecutive serum calcium values > 10.5 mg/dL), and hyperphosphatemia in paricalcitol capsules treated patients was similar to placebo. There were no treatment related adverse events associated with hypercalcemia or hyperphosphatemia in the paricalcitol capsules group. No increases in urinary calcium or phosphorous were detected in paricalcitol capsules treated patients compared to placebo.

The pattern of change in the mean values for serum iPTH during the studies is shown in Figure 1. The mean changes from baseline to final treatment visit in serum iPTH, calcium, phosphorus, and bone-specific alkaline phosphatase are shown in Table 9. Table 9.

Mean Changes from Baseline to Final Treatment Visit in Serum iPTH, Bone Specific Alkaline Phosphatase, Calcium, Phosphorus, and Calcium x Phosphorus Product in Three Combined Double-Blind, Placebo-Controlled, Phase 3, CKD Stages 3 and 4 Studies Paricalcitol Capsules Placebo iPTH (pg/mL) n = 104 n = 110 Mean Baseline Value 266 279 Mean Final Treatment Value 162 315 Mean Change fr… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility In a 104-week carcinogenicity study in CD-1 mice, an increased incidence of uterine leiomyoma and leiomyosarcoma was observed at subcutaneous doses of 1, 3, 10 mcg/kg given three times weekly (2 to 15 times the AUC at a human dose of 14 mcg, equivalent to 0.24 mcg/kg based on AUC). The incidence rate of uterine leiomyoma was significantly different than the control group at the highest dose of 10 mcg/kg. In a 104-week carcinogenicity study in rats, there was an increased incidence of benign adrenal pheochromocytoma at subcutaneous doses of 0.15, 0.5, 1.5 mcg/kg (< 1 to 7 times the exposure following a human dose of 14 mcg, equivalent to 0.24 mcg/kg based on AUC).

The increased incidence of pheochromocytomas in rats may be related to the alteration of calcium homeostasis by paricalcitol. Paricalcitol did not exhibit genetic toxicity in vitro with or without metabolic activation in the microbial mutagenesis assay (Ames Assay), mouse lymphoma mutagenesis assay (L5178Y), or a human lymphocyte cell chromosomal aberration assay. There was also no evidence of genetic toxicity in an in vivo mouse micronucleus assay.

Paricalcitol had no effect on fertility (male or female) in rats at intravenous doses up to 20 mcg/kg/dose (equivalent to 13 times a human dose of 14 mcg based on surface area, mcg/m 2 ).