Tazarotene (Page 3 of 6)

11 DESCRIPTION

Tazarotene cream, 0.05% and 0.1% is for topical use and contains the active ingredient, tazarotene. Each gram of tazarotene cream, 0.05% and 0.1% contains 0.5 and 1 mg of tazarotene, respectively in a white cream base.

Tazarotene is a member of the acetylenic class of retinoids. Chemically, tazarotene is ethyl 6-[(4,4-dimethylthiochroman-6-yl)ethynyl]nicotinate. The compound has an empirical formula of C21 H21 NO2 S and molecular weight of 351.46. The structural formula is shown below:

The structural formula for Tazarotene is a member of the acetylenic class of retinoids. Chemically, tazarotene is ethyl 6-[(4,4-dimethylthiochroman-6-yl)ethynyl]nicotinate. The compound has an empirical formula of C21H21NO2S and molecular weight of 351.46.
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Tazarotene cream contains the following inactive ingredients: benzyl alcohol 1%; carbomer 1342; carbomer homopolymer type B; edetate disodium; medium chain triglycerides; mineral oil; purified water; sodium hydroxide; sodium thiosulfate; and sorbitan monooleate.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Tazarotene is a retinoid prodrug which is converted to its active form, the carboxylic acid of tazarotene, by deesterification. Tazarotenic acid binds to all three members of the retinoic acid receptor (RAR) family: RARα, RARβ, and RARγ, but shows relative selectivity for RARβ, and RARγ and may modify gene expression. The clinical significance of these findings is unknown.

12.3 Pharmacokinetics

Following topical application, tazarotene undergoes esterase hydrolysis to form its active metabolite, tazarotenic acid. Little parent compound could be detected in the plasma. Tazarotenic acid was highly bound to plasma proteins (greater than 99%). Tazarotene and tazarotenic acid were metabolized to sulfoxides, sulfones and other polar metabolites which were eliminated through urinary and fecal pathways. The half-life of tazarotenic acid was approximately 18 hours, following topical application of tazarotene to normal, acne or psoriatic skin.

In a multiple dose trial with a once daily dose for 14 consecutive days in 9 psoriatic subjects (male=5; female=4), measured doses of tazarotene cream, 0.1% were applied by medical staff to involved skin without occlusion (5 to 35% of total body surface area: mean ± SD: 14 ± 11%). The Cmax of tazarotenic acid was 2.31 ± 2.78 ng/mL occurring 8 hours after the final dose, and the AUC0-24h was 31.2 ± 35.2 ng•hr/mL on day 15 in the five subjects who were administered clinical doses of 2 mg cream/cm2.

During clinical trials with tazarotene cream, 0.05% or 0.1% treatment for plaque psoriasis, three out of 139 subjects with their systemic exposure monitored had detectable plasma tazarotene concentrations, with the highest value at 0.09 ng/mL. Tazarotenic acid was detected in 78 out of 139 subjects (LLOQ = 0.05 ng/mL). Three subjects using tazarotene cream 0.1% had plasma tazarotenic acid concentrations greater than 1 ng/mL. The highest value was 2.4 ng/mL. However, because of the variations in the time of blood sampling, the area of psoriasis involvement, and the dose of tazarotene applied, actual maximal plasma levels are unknown.

Tazarotene cream 0.1% was applied once daily to either the face (N=8) or to 15% of body surface area (N=10) of female subjects with moderate to severe acne vulgaris. The mean Cmax and AUC values of tazarotenic acid peaked at day 15 for both dosing groups during a 29 day treatment period. Mean Cmax and AUC0-24h values of tazarotenic acid from subjects in the 15% body surface area dosing group were more than 10 times higher than those from subjects in the face-only dosing group. The single highest Cmax throughout the trial period was 1.91 ng/mL on day 15 in the exaggerated dosing group. In the face-only group, the mean ± SD values of Cmax and AUC0-24h of tazarotenic acid on day 15 were 0.10 ± 0.06 ng/mL and 1.54 ± 1.01 ng∙hr/mL, respectively, whereas in the 15% body surface area dosing group, the mean ± SD values of Cmax and AUC0-24h of tazarotenic acid on day 15 were 1.20 ± 0.41 ng/mL and 17.01 ± 6.15 ng∙hr/mL, respectively. The steady state pharmacokinetics of tazarotenic acid had been reached by day 8 in the face-only and by day 15 in the 15% body surface area dosing groups.

In a Phase 3 clinical trial, tazarotene cream, 0.1% was applied once daily for 12 weeks to each of 48 subjects (22 females and 26 males) with facial acne vulgaris. The mean ± SD values of plasma tazarotenic acid at weeks 4 and 8 were 0.078 ± 0.073 ng/mL (N=47) and 0.052 ± 0.037 ng/mL (N=42), respectively. The highest observed individual plasma tazarotenic acid concentration was 0.41 ng/mL at week 4 from a female subject. The magnitude of plasma tazarotenic acid concentrations appears to be independent of gender, age, and body weight.

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis
A long-term study of tazarotene following oral administration of 0.025, 0.050, and 0.125 mg/kg/day to rats showed no indications of increased carcinogenic risks. Based on pharmacokinetic data from a shorter term study in rats, the highest dose of 0.125 mg/kg/day was anticipated to give systemic exposure in the rat equivalent to 0.6 times that seen in a psoriatic patient treated with 0.1% tazarotene cream at 2 mg/kg/cm2 over a 35% body surface area in a controlled pharmacokinetic study. This estimated systemic exposure in rats was 2 times the maximum systemic exposure in acne patients treated with tazarotene cream, 0.1% cream at 2 mg/cm2 over a 15% body surface area.

A long-term topical application study of up to 0.1% of tazarotene in a gel formulation in mice terminated at 88 weeks showed that dose levels of 0.05, 0.125, 0.25, and 1 mg/kg/day (reduced to 0.5 mg/kg/day for males after 41 weeks due to severe dermal irritation) revealed no apparent carcinogenic effects when compared to vehicle control animals. Systemic exposures at the highest dose was 3.9 times that seen in a psoriatic patient treated with 0.1% tazarotene cream at 2 mg/cm2 over a 35% body surface area in a controlled pharmacokinetic study, and 13 times the maximum systemic exposure in acne patients treated with tazarotene cream, 0.1% at 2 mg/cm2 over a 15% body surface area.

In evaluation of photo co-carcinogenicity, median time to onset of tumors was decreased, and the number of tumors increased in hairless mice following chronic topical dosing with intercurrent exposure to ultraviolet radiation at tazarotene concentrations of 0.001%, 0.005%, and 0.01% in a gel formulation for up to 40 weeks.

Mutagenesis
Tazarotene was found to be non-mutagenic in the Ames assay and did not produce structural chromosomal aberrations in a human lymphocyte assay. Tazarotene was non-mutagenic in the CHO/HGPRT mammalian cell forward gene mutation assay and was non-clastogenic in the in vivo mouse micronucleus test.

Impairment of Fertility
No impairment of fertility occurred in rats when male animals were treated for 70 days prior to mating and female animals were treated for 14 days prior to mating and continuing through gestation and lactation with topical doses of tazarotene gel up to 0.125 mg/kg/day. Based on data from another study, the systemic drug exposure in the rat would be equivalent to 0.6 times that observed in a psoriatic patient treated with 0.1% tazarotene cream at 2 mg/cm2 over a 35% body surface area in a controlled pharmacokinetic study, and 2 times the maximum systemic exposure in acne patients treated with tazarotene cream, 0.1% at 2 mg/cm2 over a 15% body surface area.

No impairment of mating performance or fertility was observed in male rats treated for 70 days prior to mating with oral doses of up to 1 mg/kg/day tazarotene. That dose produced a systemic exposure that was 1.9 times that observed in a psoriatic patient treated with 0.1% tazarotene cream at 2 mg/cm2 over a 35% body surface area, and 6.3 times the maximum systemic exposure in acne patients treated with tazarotene cream, 0.1% at 2 mg/cm2 over a 15% body surface area.

No impairment of mating performance or fertility was observed in female rats treated for 15 days prior to mating and continuing through gestation day 7 with oral doses up to 2 mg/kg/day of tazarotene. However, there was a significant decrease in the number of estrous stages and an increase in developmental effects at that dose [see Use in Specific Populations ( 8.1)]. That dose produced a systemic exposure that was 3.4 times that observed in a psoriatic patient treated with 0.1% tazarotene cream at 2 mg/cm2 over a 35% body surface area and 11 times the maximum systemic exposure in acne patients treated with tazarotene cream, 0.1% at 2 mg/cm2 over a 15% body surface area.

Reproductive capabilities of F1 animals, including F2 survival and development, were not affected by topical administration of tazarotene gel to female F0 parental rats from gestation day 16 through lactation day 20 at the maximum tolerated dose of 0.125 mg/kg/day. Based on data from another study, the systemic drug exposure in the rat would be equivalent to 0.6 times that observed in a psoriatic patient treated with 0.1% tazarotene cream at 2 mg/cm2 over a 35% body surface area, and 2 times the maximum systemic exposure in acne patients treated with tazarotene cream, 0.1% at 2 mg/cm2 over a 15% body surface area.

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