Paricalcitol

Paricalictol capsules are indicated for the prevention and treatment of secondary hyperparathyroidism associated with Chronic Kidney Disease (CKD) Stages 3 and 4.

Paricalcitol capsules are indicated for the prevention and treatment of secondary hyperparathyroidism associated with CKD Stage 5 in patients on hemodialysis (HD) or peritoneal dialysis (PD).

Paricalcitol capsules may be administered daily or three times a week. When dosing three times weekly, the dose should be administered not more frequently than every other day. The total weekly doses for both daily and three times a week dosage regimens are similar [see Clinical Studies (14.1)].

Paricalcitol capsules may be taken without regard to food. No dosing adjustment is required in patients with mild and moderate hepatic impairment.

Initial Dose

The initial dose of paricalcitol capsules for CKD Stages 3 and 4 patients is based on baseline intact parathyroid hormone (iPTH) levels.

Dose Titration

Dosing must be individualized and based on serum or plasma iPTH levels, with monitoring of serum calcium and serum phosphorus. The following is a suggested approach to dose titration.

If a patient is taking the lowest dose, 1 mcg, on the daily regimen and a dose reduction is needed, the dose can be decreased to 1 mcg three times a week. If a further dose reduction is required, the drug should be withheld as needed and restarted at a lower dosing frequency. If a patient is on a calcium-based phosphate binder, the phosphate-binder dose may be decreased or withheld, or the patient may be switched to a non-calcium-based phosphate binder. If hypercalcemia or an elevated Ca x P is observed, the dose of paricalcitol capsules should be reduced or withheld until these parameters are normalized.

Serum calcium and phosphorus levels should be closely monitored after initiation of paricalcitol capsules, during dose titration periods and during co-administration with strong CYP3A inhibitors [see Warnings and Precautions (5.3), Drug Interactions (7) and Clinical Pharmacology (12.3)].

Paricalcitol capsules are to be administered three times a week, not more frequently than every other day.

Paricalcitol capsules may be taken without regard to food. No dosing adjustment is required in patients with mild and moderate hepatic impairment.

Initial Dose

The initial dose of paricalcitol capsules in micrograms is based on a baseline iPTH level (pg/mL)/80. To minimize the risk of hypercalcemia patients should be treated only after their baseline serum calcium has been adjusted to 9.5 mg/dL or lower [see Clinical Pharmacology (12.2) and Clinical Studies (14.2)].

Dose Titration

Subsequent dosing should be individualized and based on iPTH, serum calcium and phosphorus levels. A suggested dose titration of paricalcitol capsules is based on the following formula:

Titration dose (micrograms) = most recent iPTH level (pg/ml)/80

Serum calcium and phosphorus levels should be closely monitored after initiation, during dose titration periods, and with co-administration of strong P450 3A inhibitors. If an elevated serum calcium or elevated Ca x P is observed and the patient is on a calcium-based phosphate binder, the binder dose may be decreased or withheld, or the patient may be switched to a non-calcium-based phosphate binder. If serum calcium or Ca x P are elevated, the dose should be decreased by 2 to 4 micrograms lower than that calculated by the most recent iPTH/80. If further adjustment is required, the dose of paricalcitol capsules should be reduced or withheld until these parameters are normalized.

As iPTH approaches the target range, small, individualized dose adjustments may be necessary in order to achieve a stable iPTH. In situations where monitoring of iPTH, Ca or P occurs less frequently than once per week, a more modest initial and dose titration ratio (e.g., iPTH/100) may be warranted.

Progressive hypercalcemia due to overdosage of vitamin D and its metabolites may be so severe as to require emergency attention [see Overdosage (10)]. Acute hypercalcemia may exacerbate tendencies for cardiac arrhythmias and seizures and may potentiate the action of digitalis. Chronic hypercalcemia can lead to generalized vascular calcification and other soft-tissue calcification. Concomitant administration of high doses of calcium-containing preparations or thiazide diueretics with paricalcitol capsules may increase the risk of hypercalcemia. High intake of calcium and phosphate concomitant with vitamin D compounds may lead to serum abnormalities requiring more frequent patient monitoring and individualized dose titration. Patients also should be informed about the symptoms of elevated calcium, which include feeling tired, difficulty thinking clearly, loss of appetite, nausea, vomiting, constipation, increased thirst, increased urination and weight loss.

Prescription-based doses of vitamin D and its derivatives should be withheld during paricalcitol capsules treatment to avoid hypercalcemia.

Digitalis toxicity is potentiated by hypercalcemia of any cause. Use caution when paricalcitol capsules are prescribed concomitantly with digitalis compounds.

During the initial dosing or following any dose adjustment of medication, serum calcium, serum phosphorus, and serum or plasma iPTH should be monitored at least every two weeks for 3 months, then monthly for 3 months, and every 3 months thereafter.

Aluminum-containing preparations (e.g., antacids, phosphate binders) should not be administered chronically with paricalcitol capsules, as increased blood levels of aluminum and aluminum bone toxicity may occur.

CKD Stages 3 and 4

The safety of paricalcitol capsules has been evaluated in three 24-week (approximately six-month), double-blind, placebo-controlled, multicenter clinical studies involving 220 CKD Stages 3 and 4 patients. Six percent (6%) of paricalcitol capsules treated patients and 4% of placebo treated patients discontinued from clinical studies due to an adverse event. Adverse events occurring in the paricalcitol capsules group at a frequency of 2% or greater and more frequently than in the placebo group are presented in Table 1:

The following adverse reactions, with a causal relationship to paricalcitol capsules, occurred in <2% of the paricalcitol capsules treated patients in the above double-blind, placebo-controlled clinical trial data set.

Gastrointestinal Disorders: Dry mouth

Investigations: Hepatic enzyme abnormal

Nervous System Disorders: Dysgeusia

Skin and Subcutaneous Tissue Disorders: Urticaria

CKD Stage 5

The safety of paricalcitol capsules has been evaluated in one 12-week, double-blind, placebo-controlled, multicenter clinical study involving 88 CKD Stage 5 patients. Sixty-one patients received paricalcitol capsules and 27 patients received placebo.

The proportion of patients who terminated prematurely from the study due to adverse events was 7% for paricalcitol capsules treated patients and 7% for placebo patients.

Adverse events occurring in the paricalcitol capsules group at a frequency of 2% or greater and more frequently than in the placebo group are as follows:

The following adverse reactions, with a causal relationship to paricalcitol capsules, occurred in <2% of the paricalcitol capsules treated patients in the above double-blind, placebo-controlled clinical trial data set.

Gastrointestinal Disorders: Gastroesophageal reflux disease

Metabolism and Nutrition Disorders: Decreased appetite, hypercalcemia, hypocalcemia

Reproductive System and Breast Disorders: Breast tenderness

Skin and Subcutaneous Tissue Disorders:Acne

The following additional adverse reactions have been reported during post-approval use with the active ingredient in paricalcitol capsules: angioedema (including laryngeal edema).

To report SUSPECTED ADVERSE REACTIONS, contact Rising Pharmaceuticals, Inc. at 1-866-562-4597 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch

Since paricalcitol is partially metabolized by CYP3A, exposure of paricalcitol will be increased while paricalcitol is co-administered with strong CYP3A inhibitors including the following drugs but not limited to: ketoconazole, atazanavir, clarithromycin, indinavir, itraconazole, nefazodone, nelfinavir, ritonavir, saquinavir, telithromycin or voriconazole. Dose adjustment of paricalcitol capsules may be required, and iPTH and serum calcium concentrations should be closely monitored if a patient initiates or discontinues therapy with a strong CYP3A4 inhibitor [see Clinical Pharmacology (12.3)].

Drugs that impair intestinal absorption of fat-soluble vitamins, such as cholestyramine, may interfere with the absorption of paricalcitol capsules.

The use of mineral oil or other substances that may affect absorption of fat may influence the absorption of paricalcitol capsules.

Pregnancy Category C.

Paricalcitol has been shown to cause minimal decreases in fetal viability (5%) when administered daily to rabbits at a dose 0.5 times a human dose of 14 mcg or 0.24 mcg/kg (based on body surface area, mcg/m²), and when administered to rats at a dose two times the 0.24 mcg/kg human dose (based on body surface area, mcg/m²). At the highest dose tested, 20 mcg/kg administered three times per week in rats (13 times the 14 mcg human dose based on surface area, mcg/m²), there was a significant increase in the mortality of newborn rats at doses that were maternally toxic and are known to produce hypercalcemia in rats. No other effects on offspring development were observed.

Paricalcitol was not teratogenic at the doses tested.

Paricalcitol (20 mcg/kg) has been shown to cross the placental barrier in rats. There are no adequate and well-controlled clinical studies in pregnant women. Paricalcitol capsules should be used during pregnancy only if the potential benefit to the mother justifies the potential risk to the fetus.

Studies in rats have shown that paricalcitol is present in the milk. It is not known whether paricalcitol is excreted in human milk. In the nursing patient, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

Safety and efficacy of paricalcitol capsules in pediatric patients have not been established.

Of the total number (n = 220) of CKD Stages 3 and 4 patients in clinical studies of paricalcitol capsules, 49% were age 65 and over, while 17% were age 75 and over. Of the total number (n = 88) of CKD Stage 5 patients in the pivotal study of paricalcitol capsules, 28% were age 65 and over, while 6% were age 75 and over. No overall differences in safety and effectiveness were observed between these patients and younger patients, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

Paricalcitol is a synthetic, biologically active vitamin D₂ 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.

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% – 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% – 1.0%). In PD patients, with this dosing regimen, approximately 83.3% (95% CI: 82.6% – 84.0%) 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% - 13.0%) [see Clinical Studies (14.2) and Dosage and Administration (2.2) ].

Absorption

The mean absolute bioavailability of paricalcitol capsules under low-fat fed condition ranged from 72% to 86% in healthy subjects, CKD Stage 5 patients on HD, and CKD Stage 5 patients on PD. A food effect study in healthy subjects 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 subjects.

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 subjects 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 ³H-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 subjects, 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.

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

The pharmacokinetics of paricalcitol has not been investigated in patients less than 18 years of age.

Gender

The pharmacokinetics of paricalcitol following single doses over the 0.06 to 0.48 mcg/kg dose range was gender independent.

Hepatic Impairment

The disposition of paricalcitol (0.24 mcg/kg) was compared in patients with mild (n = 5) and moderate (n = 5) hepatic impairment (as indicated by the Child-Pugh method) and subjects with normal hepatic function (n = 10). The pharmacokinetics of unbound paricalcitol was similar across the range of hepatic function evaluated in this study. No dose adjustment is required in patients with mild and moderate hepatic impairment. The influence of severe hepatic impairment on the pharmacokinetics of paricalcitol has not been evaluated.

Renal Impairment

Following administration of paricalcitol capsules, the pharmacokinetic profile of paricalcitol for CKD Stage 5 on HD or PD was comparable to that in CKD 3 or 4 patients. Therefore, no special dose adjustments are required other than those recommended in the Dosage and Administration section [see Dosage and Administration (2) ].

Drug Interactions

An in vitro study indicates that paricalcitol is neither an inhibitor of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 or CYP3A nor an inducer of CYP2B6, CYP2C9 or CYP3A. Hence, paricalcitol is neither expected to inhibit nor induce the clearance of drugs metabolized by these enzymes.

Omeprazole

The effect of omeprazole (40 mg capsule), a strong inhibitor of CYP2C19, on paricalcitol (four 4 mcg capsules) pharmacokinetics was investigated in a single dose, crossover study in healthy subjects. The pharmacokinetics of paricalcitol was not affected when omeprazole was administered approximately 2 hours prior to the paricalcitol dose.

Ketoconazole

The effect of multiple doses of ketoconazole, a strong inhibitor of CYP3A, administered as 200 mg BID for 5 days on the pharmacokinetics of paricalcitol (4 mcg capsule) has been studied in healthy subjects. The C_max of paricalcitol was minimally affected, but AUC_0-∞ approximately doubled in the presence of ketoconazole. The mean half-life of paricalcitol was 17.0 hours in the presence of ketoconazole as compared to 9.8 hours, when paricalcitol was administered alone [see Drug Interactions (7) ].

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/m²).

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: 145-856 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 11.0 mg/dL, the dose was reduced irrespective of iPTH, and the dose was withheld if serum calcium was > 11.0 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), hyperphosphatemia and elevated Ca x P product 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.

Figure 1. Mean Values for Serum iPTH Over Time in the Three Double-Blind, Placebo-Controlled, Phase 3, CKD Stages 3 and 4 Studies Combined

The mean changes from baseline to final treatment visit in serum iPTH, calcium, phosphorus, calcium-phosphorus product (Ca x P), and bone-specific alkaline phosphatase are shown in Table 4.

The safety and efficacy of paricalcitol capsules were evaluated in a Phase 3, 12-week, double blind, placebo-controlled, randomized, multicenter study in patients with CKD Stage 5 on HD or PD. The study used a three times a week dosing design. A total of 61 patients received paricalcitol capsules and 27 patients received placebo. The mean age of the patients was 57 years, 67% were male, 50% were Caucasian, 45% were African- American, and 53% were diabetic. The average baseline iPTH was 701 pg/mL (range: 216-1933 pg/mL). The average time since first dialysis across all subjects was 3.3 years.

The initial dose of paricalcitol capsules was based on baseline iPTH/60. Subsequent dose adjustments were based on iPTH/60 as well as primary chemistry results that were measured once a week. Starting at Treatment Week 2, study drug was maintained, increased or decreased weekly based on the results of the previous week’s calculation of iPTH/60. Paricalcitol capsules were administered three times a week, not more than every other day.

The proportion of patients achieving at least two consecutive weekly ≥ 30% reductions from baseline iPTH was 88% of paricalcitol capsules treated patients and 13% of the placebo treated patients. The proportion of patients achieving at least two consecutive weekly ≥ 30% reductions from baseline iPTH was similar for HD and PD patients.

The incidence of hypercalcemia (defined as two consecutive serum calcium values > 10.5 mg/dL) in patients treated with paricalcitol capsules was 6.6% as compared to 0% for patients given placebo. In PD patients the incidence of hypercalcemia in patients treated with paricalcitol capsules was 21% as compared to 0% for patients given placebo. The patterns of change in the mean values for serum iPTH are shown in Figure 2. The rate of hypercalcemia with paricalcitol capsules may be reduced with a lower dosing regimen based on the iPTH/80 formula as shown by computer simulations. The hypercalcemia rate can be further predicted to decrease, if the treatment is initiated in only those with baseline serum calcium ≤ 9.5 mg/dL [see Clinical Pharmacology (12.2) and Dosage and Administration (2.2) ].

Figure 2. Mean Values for Serum iPTH Over Time in a Phase 3, Double-Blind, Placebo-Controlled CKD Stage 5 Study

Patients should be advised:

• of the most common adverse reactions with use of paricalcitol capsules, which include diarrhea, hypertension, dizziness and vomiting.
• to adhere to instructions regarding diet and phosphorus restriction.
• to contact a health care provider if you develop symptoms of elevated calcium, (e.g. feeling tired, difficulty thinking clearly, loss of appetite, nausea, vomiting, constipation, increased thirst, increased urination and weight loss).
• to return to the physician's office for routine monitoring. More frequent monitoring is necessary during the initiation of therapy, following dose changes or when potentially interacting medications are started or discontinued.
• to inform their physician of all medications, including prescription and nonprescription drugs, supplements, and herbal preparations they are taking and any change to their medical condition. Patients should also be advised to inform their physicians prescribing a new medication that they are taking paricalcitol capsules.