Estradiol .5 mg/.5g Gel, 30 packets — NDC 69238-2451-3 (Billing 69238-2451-03)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action Endogenous estrogens are largely responsible for the development and maintenance of the female reproductive system and secondary sexual characteristics. Although circulating estrogens exist in a dynamic equilibrium of metabolic interconversions, estradiol is the principal intracellular human estrogen and is substantially more potent than its metabolites, estrone and estriol, at the receptor level. The primary source of estrogen in normally cycling adult women is the ovarian follicle, which secretes 70 to 500 mcg of estradiol daily, depending on the phase of the menstrual cycle.

After menopause, most endogenous estrogen is produced by conversion of androstenedione, which is secreted by the adrenal cortex, to estrone in the peripheral tissues. Thus, estrone and the sulfate conjugated form, estrone sulfate, are the most abundant circulating estrogens in postmenopausal women. Estrogens act through binding to nuclear receptors in estrogen-responsive tissues.

To date, two estrogen receptors have been identified. These vary in proportion from tissue to tissue. Circulating estrogens modulate the pituitary secretion of the gonadotropins, luteinizing hormone (LH) and FSH, through a negative feedback mechanism.

Estrogens act to reduce the elevated levels of these hormones seen in postmenopausal women.

12.2Pharmacodynamics Generally, a serum estrogen concentration does not predict an individual woman’s therapeutic response to estradiol gel nor her risk for adverse outcomes. Likewise, exposure comparisons across different estrogen products to infer efficacy or safety for the individual woman may not be valid.

12.3Pharmacokinetics Absorption Estradiol diffuses across intact skin and into the systemic circulation by a passive absorption process, with diffusion across the stratum corneum being the rate-limiting factor. In a 14-day, Phase 1, multiple-dose study, estradiol gel demonstrated linear and approximately dose-proportional estradiol pharmacokinetics at steady-state for both AUC 0-24 and C max following once daily dosing to the skin of either the right or left upper thigh (Table 2). Table 2: Mean (%CV) Pharmacokinetic Parameters for Estradiol (uncorrected for baseline) on Day 14 Following Multiple Daily Doses of Estradiol Gel 0.1% Parameter (units) Estradiol Gel 0.25 grams Estradiol Gel 0.5 grams Estradiol Gel 1 gram AUC 0-24 (pg•h/mL) 236 (94) 504 (149) 732 (81) C max (pg/mL) 14.7 (84) 28.4 (139) 51.5 (86) C avg (pg/mL) 9.8 (92) 21 (148) 30.5 (81) t max * (h) 16 (0, 72) 10 (0, 72) 8 (0, 48) E2:E1 ratio 0.42 0.65 0.65 *Median (Min, Max).

Steady-state serum concentration of estradiol are achieved by day 12 following daily application of estradiol gel to the skin of the upper thigh. The mean (SD) serum estradiol levels following once daily dosing at day 14 are shown in Figure 1. Figure 1: Mean (SD) Serum Estradiol Concentrations (Values Uncorrected for Baseline) on Day 14 Following Multiple Daily Doses of Estradiol Gel 0.1% The effect of sunscreens and other topical lotions on the systemic exposure of estradiol gel has not been evaluated.

Studies conducted using topical estrogen gel approved products have shown that sunscreens have the potential for changing the systemic exposure of topically applied estrogen gels. Distribution The distribution of exogenous estrogens is similar to that of endogenous estrogens. Estrogens are widely distributed in the body and are generally found in higher concentrations in the sex hormone target organs.

Estrogens circulate in the blood largely bound to SHBG and albumin. Metabolism Exogenous estrogens are metabolized in the same manner as endogenous estrogens. Circulating estrogens exist in a dynamic equilibrium of metabolic interconversions.

These transformations take place mainly in the liver. Estradiol is converted reversibly to estrone, and both can be converted to estriol, which is a major urinary metabolite. Estrogens also undergo enterohepatic recir… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action Endogenous estrogens are largely responsible for the development and maintenance of the female reproductive system and secondary sexual characteristics. Although circulating estrogens exist in a dynamic equilibrium of metabolic interconversions, estradiol is the principal intracellular human estrogen and is substantially more potent than its metabolites, estrone and estriol, at the receptor level. The primary source of estrogen in normally cycling adult women is the ovarian follicle, which secretes 70 to 500 mcg of estradiol daily, depending on the phase of the menstrual cycle.

After menopause, most endogenous estrogen is produced by conversion of androstenedione, which is secreted by the adrenal cortex, to estrone in the peripheral tissues. Thus, estrone and the sulfate conjugated form, estrone sulfate, are the most abundant circulating estrogens in postmenopausal women. Estrogens act through binding to nuclear receptors in estrogen-responsive tissues.

To date, two estrogen receptors have been identified. These vary in proportion from tissue to tissue. Circulating estrogens modulate the pituitary secretion of the gonadotropins, luteinizing hormone (LH) and FSH, through a negative feedback mechanism.

Estrogens act to reduce the elevated levels of these hormones seen in postmenopausal women.

12.3Pharmacokinetics Absorption Estradiol diffuses across intact skin and into the systemic circulation by a passive absorption process, with diffusion across the stratum corneum being the rate-limiting factor. In a 14-day, Phase 1, multiple-dose study, estradiol gel demonstrated linear and approximately dose-proportional estradiol pharmacokinetics at steady-state for both AUC 0-24 and C max following once daily dosing to the skin of either the right or left upper thigh (Table 2). Table 2: Mean (%CV) Pharmacokinetic Parameters for Estradiol (uncorrected for baseline) on Day 14 Following Multiple Daily Doses of Estradiol Gel 0.1% Parameter (units) Estradiol Gel 0.25 grams Estradiol Gel 0.5 grams Estradiol Gel 1 gram AUC 0-24 (pg•h/mL) 236 (94) 504 (149) 732 (81) C max (pg/mL) 14.7 (84) 28.4 (139) 51.5 (86) C avg (pg/mL) 9.8 (92) 21 (148) 30.5 (81) t max * (h) 16 (0, 72) 10 (0, 72) 8 (0, 48) E2:E1 ratio 0.42 0.65 0.65 *Median (Min, Max).

Steady-state serum concentration of estradiol are achieved by day 12 following daily application of estradiol gel to the skin of the upper thigh. The mean (SD) serum estradiol levels following once daily dosing at day 14 are shown in Figure 1. Figure 1: Mean (SD) Serum Estradiol Concentrations (Values Uncorrected for Baseline) on Day 14 Following Multiple Daily Doses of Estradiol Gel 0.1% The effect of sunscreens and other topical lotions on the systemic exposure of estradiol gel has not been evaluated.

Studies conducted using topical estrogen gel approved products have shown that sunscreens have the potential for changing the systemic exposure of topically applied estrogen gels. Distribution The distribution of exogenous estrogens is similar to that of endogenous estrogens. Estrogens are widely distributed in the body and are generally found in higher concentrations in the sex hormone target organs.

Estrogens circulate in the blood largely bound to SHBG and albumin. Metabolism Exogenous estrogens are metabolized in the same manner as endogenous estrogens. Circulating estrogens exist in a dynamic equilibrium of metabolic interconversions.

These transformations take place mainly in the liver. Estradiol is converted reversibly to estrone, and both can be converted to estriol, which is a major urinary metabolite. Estrogens also undergo enterohepatic recirculation via sulfate and glucuronide conjugation in the liver, biliary secretion of conjugates into the intestine, and hydrolysis in the intestine followed by reabsorption.

In postmenopausal women, a significant proportion of the circulating estrogens exist as sulfate conjugates, especially estrone sulfate, which serves as a circulating reservoir for the formation of more active estrogens. Although the clinical significance has not been determined , estradiol from estradiol gel does not undergo first pass metabolism and provides estradiol to estrone ratios at steady-state in the range of 0.42 to 0.65. Excretion Estradiol, estrone, and estriol are excreted in the urine along with glucuronide and sulfate conjugates.

The apparent terminal half-life for estradiol was about 10 hours following administration of estradiol gel. Potential for Estradiol Transfer The effect of estradiol transfer was evaluated in healthy postmenopausal women who topically applied 1 gram of estradiol gel (single dose) on one thigh. One and 8 hours after gel application, they engaged in direct thigh-to-arm contact with a partner for 15 minutes.

While some elevation of estradiol levels over baseline was seen in the male subjects, the degree of transferability in this study was inconclusive. Effects of Washing The effect of application site washing on skin surface levels and serum concentrations of estradiol was determined in 16 healthy postmenopausal women after application of 1 gram of estradiol gel to a 200 cm 2 area on the thigh. Washing the application site with soap and water 1 hour after application removed all detectable amounts of estradiol from the surface of the skin a… [Excerpted — this section continues on DailyMed.]

12.2Pharmacodynamics Generally, a serum estrogen concentration does not predict an individual woman’s therapeutic response to estradiol gel nor her risk for adverse outcomes. Likewise, exposure comparisons across different estrogen products to infer efficacy or safety for the individual woman may not be valid.

14 CLINICAL STUDIES

14.1Effects on Vasomotor Symptoms in Postmenopausal Women A randomized, double-blind, placebo-controlled trial evaluated the efficacy of 12-week treatment with three different daily doses of estradiol gel for vasomotor symptoms in 495 postmenopausal women (86.5 percent White; 10.1 percent Black) between 34 and 89 years of age (mean age 54.6) who had at least 50 moderate to severe hot flushes per week at baseline (2-week period prior to treatment). Women applied placebo, estradiol gel 0.25 grams (0.25 mg estradiol), estradiol gel 0.5 grams (0.5 mg estradiol) or estradiol gel 1 gram (1 mg estradiol) once daily to the thigh.

Reductions in both the median daily frequency and the median daily severity of moderate to severe hot flushes were statistically significant for the 0.5 grams per day and the 1 gram per day estradiol gel doses when compared to placebo at week 4. Statistically significant reductions in both the median daily frequency and the median daily severity of moderate to severe hot flushes for the estradiol gel 0.25 grams per day dose when compared to placebo were delayed to week 7. There were statistically significant reductions in median daily frequency and severity of hot flushes for all three estradiol gel doses (0.25 grams per day, 0.5 grams per day and 1 gram per day) compared to placebo at week 12.

See Table 3 for results. Table 3: Summary of Change From Baseline in the Median Daily Frequency and Severity of Hot Flushes During Estradiol Gel Treatment (ITT Population) Estradiol Gel Placebo Evaluation 0.25 grams/day N=121 0.5 grams/day N=119 1 gram/day N=124 N=124 Frequency of Daily Hot Flushes Baseline Median 9.72 9.24 9.64

9.32Median Change: Week 4 p-value † -5.00 0.132 -5.73 0.011 -7.20 <0.001 -3.63 Median Change: Week 7 p-value † -6.62 <0.001 -7.14 <0.001 -7.71 <0.001 -4.37 Median Change: Week 12 p-value † -6.88 <0.001 -7.29 <0.001 -8.35 <0.001 -4.48 Severity of Daily Hot Flushes Baseline Median 2.52 2.51 2.52

2.54Median Change: Week 4 p-value † -0.07 0.283 -0.18 <0.001 -0.47 <0.001 -0.04 Median Change: Week 7 p-value † -0.24 <0.001 -0.46 <0.001 -1.06 <0.001 -0.06 Median Change: Week 12 p-value † -0.33 0.021 -0.56 0.002 -1.69 <0.001 -0.13 † p-values from the van Elteren’s test stratified by pooled center; comparison in median change was significant if p<0.05.

14.2Women’s Health Initiative Estrogen-Alone Trial The WHI estrogen-alone trial enrolled predominantly healthy postmenopausal women in trial to assess the risks and benefits of daily oral CE (0.625 mg)-alone compared to placebo in the prevention of certain chronic diseases. The primary endpoint was the incidence of CHD (defined as nonfatal MI, silent MI and CHD death), with invasive breast cancer as the primary adverse outcome. A “global index” included the earliest occurrence of CHD, invasive breast cancer, stroke, PE, colorectal cancer, hip fracture, or death due to other cause.

This trial did not evaluate the effects of CE-alone on menopausal symptoms. The WHI estrogen-alone trial was stopped early because an increased risk of stroke was observed, and it was deemed that no further information would be obtained regarding the risks and benefits of estrogen-alone in predetermined primary endpoints. Centrally adjudicated results for stroke events, after an average follow-up of 7.1 years, reported estrogen-alone increased the risk for ischemic stroke compared to placebo, and this excess risk was present in all subgroups of women examined.

No overall difference for primary CHD events (nonfatal MI, silent MI and CHD death) and invasive breast cancer incidence in women receiving CE-alone compared to placebo was reported in final centrally adjudicated results from the estrogen-alone trial, after an average follow-up of 7.1 years. 3,4 Results of the estrogen-alone trial, which included 10,739 women (average age of 63 years, range 50 to 79; 75.3% White, 15.1% Black, 6.1% Hispanic, 3.6% Other), after an average follow-up of 7.1 years are pre… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, and Impairment of Fertility Long-term continuous administration of natural and synthetic estrogens in certain animal species increases the frequency of carcinomas of the breast, uterus, cervix, vagina, testis and liver.