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Enjuvia

CLINICAL PHARMACOLOGY

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, secreted by the adrenal cortex, to estrone by 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 follicle-stimulating hormone (FSH), through a negative feedback mechanism. Estrogens act to reduce the elevated levels of these hormones in postmenopausal women.

A. Absorption

Synthetic conjugated estrogens, B are soluble in water and are well absorbed from the gastrointestinal tract after release from the drug formulation. ENJUVIA tablets release synthetic conjugated estrogens, B slowly over a period of several hours. Table 1 and Table 2 summarize the mean pharmacokinetic parameters for unconjugated (free) and conjugated (total) estrogens following single administration of two 0.625 mg tablets to 21 healthy postmenopausal women under fasting conditions. The effect of food on the bioavailability of synthetic conjugated estrogens, B following administration of ENJUVIA (synthetic conjugated estrogens, b) tablets has not been studied. However, the presence of food did not significantly affect the pharmacokinetics of a similar formulation of synthetic conjugated estrogens, B.

Table 1. Mean Pharmacokinetic Parameters of Unconjugated (Free) Estrogens Following a Single Dose of 2 x 0.625 mg ENJUVIA (synthetic conjugated estrogens, b) Tablets Under Fasting Conditions*


  Cmax
(pg/mL)
tmax
(hr)
t½
(hr)
AUC0-48h
(pg•hr/mL)
Baseline-corrected estrone
(% CV)
75.87
(39)
9.29
(25)
23.46
(59)
1601.59
(41)
Equilin
(% CV)
41.94
(49)
8.38
(27)
15.09
(55)
707.21
(46)
Cmax = peak plasma concentration; tmax = time peak concentration occurs; t½ = apparent terminal-phase disposition half-life; AUC0-48h = total area under the concentration-time curve from time zero to time of last quantifiable concentration (48h); *Δ8,9Dehydroestrone (free) levels were below the assay limit of quantitation; CV= Coefficient of Variance

Table 2. Mean Pharmacokinetic Parameters of Conjugated (Total) Estrogens Following a Single Dose of 2 x 0.625 mg ENJUVIA (synthetic conjugated estrogens, b) Tablets Under Fasting Conditions


  Cmax
(pg/mL)
tmax
(h)
t½
(h)
AUC0-48h
(ng•h/mL)
Baseline-corrected estrone
(% CV)
3.74
(29)
8.00
(27)
14.26
(26)
62.03
(34)
Equilin
(% CV)
3.69
(44)
8.05
(36)
11.28
(28)
58.25
(53)
Δ8,9 Dehydroestrone
(%CV)
0.74
(32)
7.55
(37)
14.14
(26)
12.93
(39)
Cmax = peak plasma concentration; tmax = time peak concentration occurs; t½ = apparent terminal-phase disposition half-life; AUC0-48h = total area under the concentration-time curve from time zero to time of last quantifiable concentration (48h); CV= Coefficient of Variance

B. 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 sex hormone binding globulin (SHBG) and albumin.

C. 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 the 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 portion of the circulating estrogens exists as sulfate conjugates, especially estrone sulfate, which serves as a circulating reservoir for the formation of more active estrogens.

D. Excretion

Estradiol, estrone, and estriol are excreted in the urine along with glucuronide and sulfate conjugates. The mean (SD) apparent terminal elimination half-life (t½) of conjugated estrone is 14 (± 6) hours and conjugated equilin is 11 (± 6) hours.

E. Special Populations

No pharmacokinetic studies were conducted in special populations, including patients with renal or hepatic impairment.

F. Drug Interactions

In vitro and in vivo studies have shown that estrogens are metabolized partially by cytochrome P450 3A4 (CYP3A4). Therefore, inducers or inhibitors of CYP3A4 may affect estrogen drug metabolism. Inducers of CYP3A4, such as St. John's Wort preparations (Hypericum perforatum), phenobarbital, carbamazepine, and rifampin, may reduce plasma concentrations of estrogens, possibly resulting in a decrease in therapeutic effects and/or changes in the uterine bleeding profile. Inhibitors of CYP3A4, such as erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir, and grapefruit juice, may increase plasma concentrations of estrogens and may result in side effects.

Clinical Studies

Effects on Vasomotor Symptoms

A randomized, double-blind, placebo-controlled, dose-ranging, multi-center clinical study was conducted to evaluate the safety and effectiveness of ENJUVIA (synthetic conjugated estrogens, b) tablets for the treatment of vasomotor symptoms in 281 naturally or surgically postmenopausal women aged 26 to 65 years who were experiencing a minimum of seven moderate to severe hot flushes per day or 50 per week at randomization. The majority (81%) of patients were Caucasian (n=228) and 17.4% were Black (n= 49). Patients were randomized to receive ENJUVIA (synthetic conjugated estrogens, b) tablets 0.3 mg, 0.625 mg, 1.25 mg, or placebo once daily for 12 weeks.

ENJUVIA (synthetic conjugated estrogens, b) (0.3 mg, 0.625 mg and 1.25 mg tablets) was shown to be statistically better than placebo at weeks 4 and 12 for relief of both the frequency and severity of moderate to severe vasomotor symptoms (Table 3 and 4).

Table 3. Mean Number and Mean Change in Number of Moderate to Severe Hot Flushes Per Week ITT Population With LOCF


  0.3 mg
n=66
0.625 mg
n=71
1.25 mg
n=69
Placebo
n=70
Baseline        
  Mean (SD) 104.3 (57.7) 97.3 (82.1) 86.8 (42.1) 96.4 (58.2)
Week 4        
  Mean (SD) 47.0 (52.9) 23.3 (26.9) 24.6 (47.0) 57.8 (47.5)
  Mean Change from Baseline (SE) -49.8 (5.2) -72.8 (5.0) -68.3 (5.1) -37.2 (5.0)
  p-value versus placebo 0.005 < 0.001 < 0.001 ---
Week 12        
  Mean (SD) 30.7 (47.7) 12.2 (18.7) 12.4 (26.3) 47.5 (49.8)
  Mean Change from Baseline (SE) -66.3 (4.6) -84.6 (4.4) -82.6 (4.5) -48.3 (4.5)
  p-value versus placebo < 0.001 < 0.001 < 0.001 ---
ITT= Intent to treat; LOCF= Last Observation Carried Forward, SD= Standard Deviation; SE= Standard Error

Table 4. Mean Change in Severity of Moderate to Severe Hot Flushes Per Week, ITT Population with LOCF


  0.3 mg
n=66
0.625 mg
n=71
1.25 mg
n=69
Placebo
n=70
Baseline        
  Mean (SD) 2.5 (0.3) 2.5 (0.3) 2.5 (0.3) 2.5 (0.3)
Week 4        
  Mean (SD) 2.1 (0.8) 1.9 (1.0) 1.5 (1.1) 2.2 (0.8)
  Mean Change from Baseline (SE) -0.5 (0.1) -0.6 (0.1) -1.0 (0.1) -0.3 (0.1)
  p-value versus placebo 0.036 0.002 < 0.001 ---
Week 12        
  Mean (SD) 1.5 (1.2) 1.1 (1.2) 1.0 (1.1) 1.9 (1.1)
  Mean Change from Baseline (SE) -1.0 (0.1) -1.4 (0.1) -1.5 (0.1) -0.6 (0.1)
  p-value versus placebo 0.023 < 0.001 < 0.001 ---
ITT= Intent to treat; LOCF= Last Observation Carried Forward, SD= Standard Deviation; SE= Standard Error
Effects on Vulvar and Vaginal Atrophy

A randomized, double-blind, placebo-controlled, multi-center clinical study was conducted to evaluate the safety and effectiveness of ENJUVIA (synthetic conjugated estrogens, b) 0.3 mg tablets for the treatment of symptoms of vulvar and vaginal atrophy in 248 naturally or surgically postmenopausal women between 32 to 81 years of age (mean 58.6 years) who at baseline had ≤ 5% superficial cells on a vaginal smear, a vaginal pH > 5.0, and who identified their most bothersome moderate to severe symptom of vulvar and vaginal atrophy. The majority (82%) of the women were Caucasian (n=203), 11% were Hispanic (n=26), 4% were Black (n=9) and 3% were Asian (n=6). All patients were assessed for improvement in the mean change from baseline to Week 12 for three co-primary efficacy variables: most bothersome symptom of vulvar and vaginal atrophy (defined as the moderate to severe symptom that had been identified by the patient as most bothersome to her at baseline); percentage of vaginal superficial cells and percentage of vaginal parabasal cells; and vaginal pH.

In this study, a statistically significant mean change between baseline and week 12 for the group treated with ENJUVIA (synthetic conjugated estrogens, b) 0.3 mg tablets compared to placebo was observed for the symptoms, vaginal dryness and pain with intercourse. See Table 5. ENJUVIA (synthetic conjugated estrogens, b) 0.3 mg tablets increased superficial cells by a mean of 17.1% as compared to 2.0% for placebo (statistically significant). A corresponding statistically significant mean reduction from baseline in parabasal cells (41.7% for ENJUVIA (synthetic conjugated estrogens, b) 0.3mg tablets and 6.8% for placebo) was observed at week 12. The mean reduction between baseline and week 12 in the pH was 1.69 in the ENJUVIA (synthetic conjugated estrogens, b) 0.3 mg tablets group and 0.45 in the placebo group (statistically significant).

Table 5. Change from Baseline to Week 12 in the Severity of Vaginal Dryness and Pain with Intercourse, Symptoms That Were Identified by the Menopausal Study Patient as Her Most Bothersome Symptom of Vulvar and Vaginal Atrophy at Baseline


Most Bothersome Symptom at Baseline* ENJUVIA 0.3 mg Placebo
Vaginal Dryness    
  n 56 54
  Baseline Severity 2.52 2.54
  Mean Severity at Week 12 0.80 1.81
  Mean Change in Severity from Baseline (s.d.) -1.71 (0.85) -0.72 (0.66)
  p-value vs. placebo < 0.001 -
Pain With Intercourse    
  n 35 40
  Baseline Severity 2.74 2.70
  Mean Severity at Week 12 0.94 1.95
  Mean Change in Severity from Baseline (s.d.) -1.80 (1.02) -0.75 (0.95)
  p-value vs. placebo < 0.001 -
* Treatment differences assessed by ANCOVA or rank ANCOVA (% cell data) with baseline as covariate for the modified intent-to-treat population, last-observation-carried-forward data set.
Women's Health Initiative Studies

The WHI enrolled approximately 27,000 predominantly healthy postmenopausal women in two substudies to assess the risks and benefits of either the use of oral conjugated estrogens (CE 0.625 mg) alone per day or in combination with medroxyprogesterone acetate (CE 0.625 mg/MPA 2.5 mg) per day compared to placebo in the prevention of certain chronic diseases. The primary endpoint was the incidence of coronary heart disease (CHD) (nonfatal myocardial infarction (MI), silent MI and CHD death), with invasive breast cancer as the primary adverse outcome studied. A "global index" included the earliest occurrence of CHD, invasive breast cancer, stroke, pulmonary embolism (PE), endometrial cancer (only in the estrogen plus progestin substudy), colorectal cancer, hip fracture, or death due to other causes. The study did not evaluate the effects of CE or CE/MPA on menopausal symptoms.

The estrogen-alone substudy 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. Results of the estrogen-alone substudy, 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 6.8 years are presented in Table 6.

Table 6: Relative And Absolute Risk Seen In The Estrogen-Alone Substudy Of WHIa


Eventc Relative Risk
CE vs. Placebo
(95% nCIa)
Placebo
n = 5,429
CE
n = 5,310
Absolute Risk per 10,000
Women-Years
CHD eventsb
Nonfatal MIb
CHD death
b
0.95 (0.79- 1.16)
0.91 (0.73-1.14)
1.01(0.71- 1.43)
56
43
16
53
40
16
Strokec 1.39 (1.10-1.77) 32 44
Deep vein thrombosisb,d 1.47 (1.06-2.06) 15 23
Pulmonary embolismb 1.37 (0.90-2.07) 10 14
Invasive breast cancerb 0.80 (0.62-1.04) 34 28
Colorectal cancerc 1.08 (0.75-1.55) 16 17
Hip fracturec 0.61 (0.41-0.91) 17 11
Vertebral fracturesc, d 0.62 (0.42-0.93) 17 11
Total fracturesc, d 0.70 (0.63-0.79) 195 139
Death due to other causesc, e 1.08 (0.88-1.32) 50 53
Overall mortalityc, d 1.04 (0.88-1.32) 78 81
Global indexc, f 1.01 (0.91-1.12) 190 192
a)   Nominal confidence intervals unadjusted for multiple looks and multiple comparisons
b)  Results are based on centrally adjudicated data for an average follow-up of 7.1 years
c)   Results are based on an average follow-up of 6.8 years
d)  Not included in Global Index
e)   All deaths, except from breast or colorectal cancer, definite/probable CHD, PE or cerebrovascular disease
f)   A subset of the events was combined in a "global index", defined as the earliest occurrence of CHD events, invasive breast cancer, stroke, pulmonary embolism, colorectal cancer, hip fracture, or death due to other causes

For those outcomes included in the WHI "global index" that reached statistical significance, the absolute excess risk per 10,000 women-years in the group treated with estrogen-alone was 12 more strokes, while the absolute risk reduction per 10,000 women-years was 6 fewer hip fractures. The absolute excess risk of events included in the "global index" was a nonsignificant 2 events per 10,000 women-years. There was no difference between the groups in terms of all-cause mortality. (See BOXED WARNINGS, WARNINGS, and PRECAUTIONS.)

Final centrally adjudicated results for CHD events and centrally adjudicated results for invasive breast cancer incidence from the estrogen-alone substudy, after an average follow-up of 7.1 years, reported 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 with placebo (see Table 6).

The estrogen-plus-progestin substudy was also stopped early because, according to the predefined stopping rule, after an average follow-up of 5.2 years of treatment, the increased risk of breast cancer and cardiovascular events exceeded the specified benefits included in the "global index." The absolute excess risk of events included in the "global index" was 19 per 10,000 women-years (RR 1.15, 95% nCI 1.03-1.28).

For those outcomes included in the WHI "global index" that reached statistical significance after 5.6 years of follow-up, the absolute excess risks per 10,000 women years in the group treated with CE/MPA were 6 more CHD events, 7 more strokes, 10 more PEs, and 8 more invasive breast cancers, while the absolute risk reductions per 10,000 women-years were 7 fewer colorectal cancers and 5 fewer hip fractures. (See BOXED WARNINGS, WARNINGS, and PRECAUTIONS.)

Results of the estrogen-plus-progestin substudy, which included 16,608 women (average age of 63 years, range 50 to 79; 83.9% White, 6.8% Black, 5.4% Hispanic, 3.9% Other) are presented in Table 7 below.

Table 7. Relative And Absolute Risk Seen in the Estrogen-Plus Progestin Substudy of WHI at an Average of 5.6 Yearsa


Eventc Relative Risk
CE/MPA vs. Placebo
(95% nCIb)
Placebo
n = 8102
CE/MPA
n = 8506
Absolute Risk per 10,000 women-years
CHD events
Non-fatal MI
CHD death
1.24 (1.00-1.54)
1.28 (1.00-1.63)
1.10 (0.70-1.75)
33
25
8
39
31
8
All strokes 1.31 (1.02-1.68) 24 31
Ischemic stroke 1.44 (1.09 -1.90) 18 26
Deep vein thrombosis 1.95 (1.43 - 2.67) 13 26
Pulmonary embolism 2.13 (1.45-3.11) 8 18
Invasive breast cancerc 1.24 (1.01-1.54) 3 41
Invasive colorectal cancer 0.56 (0.38-0.81) 16 9
Endometrial cancer 0.81 (0.48-1.36) 7 6
Cervical cancer 1.44 (0.47-4.42) 1 2
Hip fracture 0.67 (0.47-0.96) 16 11
Vertebral fractures 0.65 (0.46-0.92) 17 11
Lower arm/wrist fractures 0.71 (0.59-0.85) 62 44
Total fractures 0.76 (0.69-0.83) 199 152
a)Results are based on centrally adjudicated data. Mortality data was not part of the adjudicated data; however, data at 5.2 years of follow-up showed no difference between the groups in terms of all-cause mortality (RR 0.98, 95% nCI 0.82-1.18)
b)Nominal confidence intervals unadjusted for multiple looks and multiple comparisons
c)Includes metastatic and non-metastatic breast cancer, with the exception of in situ breast cancer
Women's Health Initiative Memory Study

The estrogen-alone Women's Health Initiative Memory Study (WHIMS), a substudy of WHI study, enrolled 2,947 predominantly healthy postmenopausal women 65 years of age and older (45% were age 65 to 69 years, 36% were 70 to 74 years, and 19% were 75 years of age and older) to evaluate the effects of conjugated estrogens (CE 0.625 mg) on the incidence of probable dementia (primary outcome) compared with placebo.

After an average follow-up of 5.2 years, 28 women in the estrogen-alone group (37 per 10,000 women-years) and 19 in the placebo group (25 per 10,000 women-years) were diagnosed with probable dementia. The relative risk of probable dementia in the estrogen-alone group was 1.49 (95% CI 0.83-2.66) compared to placebo. It is unknown whether these findings apply to younger postmenopausal women. (See BOXED WARNINGS, WARNINGS, Dementia and PRECAUTIONS, Geriatric Use.)

The estrogen-plus-progestin WHIMS substudy enrolled 4,532 predominantly healthy postmenopausal women 65 years of age and older (47% were aged 65 to 69 years, 35% were 70 to 74 years, and 18% were 75 years of age and older) to evaluate the effects of CE 0.625 mg plus MPA 2.5 mg on the incidence of probable dementia (primary outcome) compared with placebo.

After an average follow-up of 4 years, 40 women in the estrogen plus progestin group (45 per 10,000 women-years) and 21 in the placebo group (22 per 10,000 women-years) were diagnosed with probable dementia. The relative risk of probable dementia in the hormone therapy group was 2.05 (95% CI 1.21-3.48) compared to placebo. Differences between groups became apparent in the first year of treatment. It is unknown whether these findings apply to younger postmenopausal women. (See BOXED WARNING, WARNINGS, Dementia, and PRECAUTIONS, Geriatric Use.)

When data from the two populations were pooled as planned in the WHIMS protocol, the reported overall relative risk for probable dementia was 1.76 (95% CI 1.19-2.60). It is unknown whether these findings apply to younger postmenopausal women. (See BOXED WARNING, WARNINGS, Dementia, and PRECAUTIONS, Geriatric Use.)

Last reviewed on RxList: 8/7/2007
This monograph has been modified to include the generic and brand name in many instances.

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