CLINICAL PHARMACOLOGY
Mechanism of Action
Fluticasone furoate is a synthetic trifluorinated corticosteroid with potent anti-inflammatory activity. The precisemechanism through which fluticasone furoate affects rhinitis symptoms is not known. Corticosteroids have been shown to have a wide range of actions on multiple cell types (e.g., mast cells, eosinophils, neutrophils, macrophages, lymphocytes) and mediators (e.g., histamine, eicosanoids, leukotrienes, cytokines) involved in inflammation. Specific effects of fluticasone furoate demonstrated in in vitro and in vivo models included activation of the glucocorticoid response element, inhibition of pro-inflammatory transcription factors such as NFkB, and inhibition of antigen-induced lung eosinophilia in sensitized rats.
Fluticasone furoate has been shown in vitro to exhibit a binding affinity for the human glucocorticoid receptor that is approximately 29.9 times that of dexamethasone and 1.7 times that of fluticasone propionate. The clinical relevance of these findings is unknown.
Pharmacodynamics
Adrenal Function
The effects of VERAMYST Nasal Spray on adrenal function have been evaluated in 4 controlled clinical trials in patients with perennial allergic rhinitis. Two 6-week clinical trials were designed specifically to assess the effect of VERAMYST Nasal Spray on the HPA axis with assessments of both 24-hour urinary cortisol excretion and serum cortisol levels in domiciled patients. In addition, one 52-week safety study and one 12-week safety and efficacy study included assessments of 24-hour urinary cortisol excretion. Details of the studies and results are described below. In all 4 studies, since serum fluticasone determinations were generally below the limit of quantification, compliance was assured by efficacy assessments.
Clinical Trials Specifically Designed to Assess Hypothalamic-Pituitary-Adrenal Axis Effect
In a 6-week randomized, double-blind, parallel-group study in adult and adolescent patients 12 years of age and older with perennial allergic rhinitis, VERAMYST Nasal Spray 110 mcg was compared to both placebo nasal spray and prednisone as a positive-control group that received prednisone 10 mg orally once daily for the final 7 days of the treatment period. Adrenal function was assessed by 24-hour urinary cortisol excretion before and after 6 weeks of treatment and by serial serum cortisol levels. Patients were domiciled for collection of 24-hour urinary cortisol. After 6 weeks of treatment, there was a change from baseline in the mean 24-hour urinary cortisol excretion in the group treated with VERAMYST Nasal Spray (n = 43) of -1.16 mcg/day compared to -3.48 mcg/day in the placebo group (n = 42). The difference from placebo in the group treated with VERAMYST Nasal Spray was 2.32 mcg/day (95% CI: -6.76, 11.39). Urinary cortisol data were not available for the positive-control (prednisone) treatment group. For serum cortisol levels, after 6 weeks of treatment there was a change from baseline in the mean (0-24 hours) of -0.38 and 0.08 mcg/dL for the group treated with VERAMYST Nasal Spray (n = 43) and the placebo group (n = 44), respectively, with a difference between the group treated with VERAMYST Nasal Spray and the placebo group of -0.47 mcg/dL (95% CI: -1.31, 0.37). For comparison, in the positive-control (prednisone, n = 12) treatment group, there was a change in mean serum cortisol (0-24 hours) from baseline of -4.49 mcg/dL with a difference between the prednisone and placebo group of -4.57 mcg/dL (95% CI: -5.83, -3.31).
The second 6-week study conducted in children 2 to 11 years of age was of similar design to the adult study, including adrenal function assessments, but did not include a prednisone positive-control arm. Patients were treated once daily with VERAMYST Nasal Spray 110 mcg or placebo nasal spray. After 6 weeks of treatment, there was a change in the mean 24-hour urinary cortisol excretion in the group treated with VERAMYST Nasal Spray (n = 43) of 0.49 mcg/day compared to 1.92 mcg/day in the placebo group (n = 41), with a difference between the group treated with VERAMYST Nasal Spray and the placebo group of -1.43 mcg/day (95% CI: -5.21, 2.35). For serum cortisol levels, after 6 weeks, there was a change from baseline in mean (0-24 hours) of -0.34 and -0.23 mcg/dL for the group treated with VERAMYST Nasal Spray (n = 48) and for the placebo group (n = 47), respectively, with a difference between the group treated with VERAMYST Nasal Spray and the placebo group of -0.11 mcg/dL (95% CI: -0.88, 0.66).
Additional Hypothalamic-Pituitary-Adrenal Axis Assessments
In the 52-week safety trial in adolescents and adults 12 years of age and older with perennial allergic rhinitis, VERAMYST Nasal Spray 110 mcg (n = 605) was compared to placebo nasal spray (n = 201). Adrenal function was assessed by 24-hour urinary cortisol excretion in a subset of patients who received VERAMYST Nasal Spray (n = 370) or placebo (n = 120) before and after 52 weeks of treatment. After 52 weeks of treatment, the mean change from baseline 24-hour urinary cortisol excretion was 5.84 mcg/day in the group treated with VERAMYST Nasal Spray and 3.34 mcg/day in the placebo group. The difference from placebo in mean change from baseline 24-hour urinary cortisol excretion was 2.50 mcg/day (95% CI: -5.49, 10.49).
In the 12-week safety and efficacy trial in children 2 to 11 years of age with perennial allergic rhinitis, VERAMYST Nasal Spray 55 mcg (n = 185) and VERAMYST Nasal Spray 110 mcg (n = 185) were compared to placebo nasal spray (n = 188). Adrenal function was assessed by measurement of 24-hour urinary free cortisol in a subset of patients who were 6 to 11 years of age (103 to 109 patients per group) before and after 12 weeks of treatment. After 12 weeks of treatment, there was a decrease in mean 24-hour urinary cortisol excretion from baseline in the group treated with VERAMYST Nasal Spray 55 mcg (n = 109) of -2.93 mcg/day and in the group treated with VERAMYST Nasal Spray 110 mcg (n = 103) of -2.07 mcg/day compared to an increasein the placebo group (n = 107) of 0.08 mcg/day. The difference from placebo in mean change from baseline in 24-hour urinary cortisol excretion for the group treated with VERAMYST Nasal Spray 55 mcg was -3.01 mcg/day (95% CI: -6.16, 0.13) and -2.14 mcg/day (95% CI: -5.33, 1.04) for the group treated with VERAMYST Nasal Spray 110 mcg.
When the results of the HPA axis assessments described above are taken as a whole, an effect of intranasal fluticasone furoate on adrenal function cannot be ruled out, especially in pediatric patients.
Cardiac Effects
A QT/QTc study did not demonstrate an effect of fluticasone furoate administration on the QTc interval. The effect of a single dose of 4,000 mcg of orally inhaled fluticasone furoate on the QTc interval was evaluated over 24 hours in 40 healthy male and female subjects in a placebo and positive (a single dose of 400 mg oral moxifloxacin) controlled cross-over study. The QTcF maximal mean change from baseline following fluticasone furoate was similar to that observed with placebo with a treatment difference of 0.788 msec, 90%CI: -1.802, 3.378. In contrast, moxifloxacin given as a 400-mg tablet resulted in prolongation of the QTcF maximal mean change from baseline compared with placebo with a treatment difference of 9.929 msec, 90% CI: 7.339,12.520. While a single dose of fluticasone furoate had no effect on the QTc interval, the effects of fluticasone furoate may not be at steady state following single dose. The effect of fluticasone furoate on the QTc interval following multiple dose administration is unknown.
Pharmacokinetics
Absorption
Following intranasal administration of fluticasone furoate, most of the dose is eventually swallowed and undergoes incomplete absorption and extensive first-pass metabolism in the liver and gut, resulting in negligible systemic exposure. At the highest recommended intranasal dosage of 110 mcg once daily for up to 12 months in adults and up to 12 weeks in children, plasma concentrations of fluticasone furoate are typically not quantifiable despite the use of a sensitive HPLC-MS/MS assay with a lower limit of quantification (LOQ) of 10 pg/mL. However, in a few isolated cases (<0.3%) fluticasone furoate was detected in high concentrations above 500 pg/mL, and in a single case the concentration was as high as 1,430 pg/mL in the 52-week study. There was no relationship between these concentrations and cortisol levels in these subjects. The reasons for these high concentrations are unknown.
Absolute bioavailability was evaluated in 16 male and female subjects following supratherapeutic dosages of fluticasone furoate (880 mcg given intranasally at 8-hour intervals for 10 doses, or 2,640 mcg/day). The average absolute bioavailability was 0.50% (90% CI: 0.34%, 0.74%).
Due to the low bioavailability by the intranasal route, the majority of the pharmacokinetic data was obtained via other routes of administration. Studies using oral solution and intravenous dosing of radiolabeled drug have demonstrated that at least 30% of fluticasone furoate is absorbed and then rapidly cleared from plasma. Oral bioavailability is on average 1.26%, and the majority of the circulating radioactivity is due to inactive metabolites.
Distribution
Following intravenous administration, the mean volume of distribution at steady state is 608 L.
Binding of fluticasone furoate to human plasma proteins is greater than 99%.
Metabolism
In vivo studies have revealed no evidence of cleavage of the furoate moiety to form fluticasone. Fluticasone furoate is cleared (total plasma clearance of 58.7 L/h) from systemic circulation principally by hepatic metabolism via the cytochrome P450 isozyme CYP3A4. The principal route of metabolism is hydrolysis of the S-fluoromethyl carbothioate function to form the inactive 17β-carboxylic acid metabolite.
Elimination
Fluticasone furoate and its metabolites are eliminated primarily in the feces, accounting for approximately 101% and 90% of the orally and intravenously administered dose, respectively. Urinary excretion accounted for approximately 1% and 2% of the orally and intravenously administered dose, respectively. The elimination phase half-life averaged 15.1 hours following intravenous administration.
Population Pharmacokinetics
Fluticasone furoate is typically not quantifiable in plasma following intranasal dosing of 110 mcg once daily with the exception of isolated cases of very high plasma levels (see Absorption). Overall, quantifiable levels (>10 pg/mL) were observed in <31% of patients aged 12 years and older and in <16% of children (aged 2 to 11 years) following intranasal dosing of 110 mcg once daily and in <7% of children following intranasal dosing of 55 mcg once daily. There was no evidence to suggest that the presence or absence of detectable levels of fluticasone furoate was related to gender, age, or race Hepatic Impairment
Reduced liver function may affect the elimination of corticosteroids. Since fluticasone furoate undergoes extensive first-pass metabolism by the hepatic cytochrome P450 isozyme CYP3A4, the pharmacokinetics of fluticasone furoate may be altered in patients with hepatic impairment. A study of a single 400-mcg dose of orally inhaled fluticasone furoate in patients with moderate hepatic impairment (Child-Pugh Class B) resulted in increased Cmax (42%) and AUC(0-∞) (172%), resulting in an approximately 20% reduction in serum cortisol level in patients with hepatic impairment compared to healthy subjects. The systemic exposure would be expected to be higher than that observed had the study been conducted after multiple doses and/or in patients with severe hepatic impairment. Therefore, use VERAMYST Nasal Spray with caution in patients with severe hepatic impairment.
Renal Impairment
Fluticasone furoate is not detectable in urine from healthy subjects following intranasal dosing. Less than 1% of dose-related material is excreted in urine. No dosage adjustment is required in patients with renal impairment.
NONCLINICAL TOXICOLOGY
Carcinogenesis, Mutagenesis, Impairment of Fertility
Fluticasone furoate produced no treatment-related increases in the incidence of tumors in 2-year inhalation studies in rats and mice at doses of up to 9 and 19 mcg/kg/day, respectively (less than the maximum recommended daily intranasal dose in adults and children on a mcg/m2 basis).
Fluticasone furoate did not induce gene mutation in bacteria or chromosomal damage in a mammalian cell mutation test in mouse lymphoma L5178Y cells in vitro . There was also no evidence of genotoxicity in the in vivo micronucleus test in rats.
No evidence of impairment of fertility was observed in reproductive studies conducted in male and female rats at inhaled fluticasone furoate doses of up to 24 and 91 mcg/kg/day, respectively (approximately 2 and 7 times, respectively, the maximum recommended daily intranasal dose in adults on a mcg/m2 basis).
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