CLINICAL PHARMACOLOGY
Mechanism Of Action
Leuprolide acetate is a
long-acting GnRH analog. A single injection of LUPRON DEPOT results in an
initial stimulation followed by a prolonged suppression of pituitary
gonadotropins. Repeated dosing at quarterly (LUPRON DEPOT 11.25 mg) intervals
results in decreased secretion of gonadal steroids. Consequently, tissues and
functions that depend on gonadal steroids for their maintenance become
quiescent. This effect is reversible on discontinuation of drug therapy.
Leuprolide acetate is not
active when given orally.
Pharmacodynamics
In a pharmacokinetic/pharmacodynamic study of LUPRON DEPOT 11.25 mg in healthy
female subjects (N=20), the onset of estradiol suppression was observed for
individual subjects between day 4 and week 4 after dosing. By the third week
following the injection, the mean estradiol concentration (8 pg/mL) was in the
menopausal range. Throughout the remainder of the dosing period, mean serum
estradiol levels ranged from the menopausal to the early follicular range.
Serum estradiol was suppressed
to ≤20 pg/mL in all subjects within four weeks and remained suppressed
(≤40 pg/mL) in 80% of subjects until the end of the 12-week dosing
interval, at which time two of these subjects had a value between 40 and 50
pg/mL. Four additional subjects had at least two consecutive elevations of
estradiol (range 43-240 pg/mL) levels during the 12-week dosing interval, but
there was no indication of luteal function for any of the subjects during this
period.
Pharmacokinetics
Absorption
Following a single injection of
the three month formulation of LUPRON DEPOT 11.25 mg in female subjects, a mean
plasma leuprolide concentration of 36.3 ng/mL was observed at 4 hours.
Leuprolide appeared to be released at a constant rate following the onset of
steady-state levels during the third week after dosing and mean levels then
declined gradually to near the lower limit of detection by 12 weeks. The mean
(± standard deviation) leuprolide concentration from 3 to 12 weeks was 0.23 ±
0.09 ng/mL. However, intact leuprolide and an inactive major metabolite could
not be distinguished by the assay which was employed in the study. The initial
burst, followed by the rapid decline to a steady-state level, was similar to
the release pattern seen with the monthly formulation.
In a pharmacokinetic/pharmacodynamic study of endometriosis patients, intramuscular
11.25 mg LUPRON DEPOT (n=19) every 12 weeks or intramuscular 3.75 mg LUPRON
DEPOT (n=15) every 4 weeks was administered for 24 weeks. There was no
statistically significant difference in changes of serum estradiol
concentration from baseline between the 2 treatment groups.
Distribution
The mean steady-state volume of
distribution of leuprolide following intravenous bolus administration to
healthy male volunteers was 27 L. In vitro binding to human plasma proteins
ranged from 43% to 49%.
Metabolism
In healthy male volunteers, a 1
mg bolus of leuprolide administered intravenously revealed that the mean
systemic clearance was 7.6 L/h, with a terminal elimination half-life of
approximately 3 hours based on a two compartment model.
Metabolite I, a smaller
inactive peptide, plasma concentrations measured in 5 prostate cancer patients
reached maximum concentration 2 to 6 hours after dosing and were approximately
6% of the peak parent drug concentration. One week after dosing, mean plasma
M-I concentrations were approximately 20% of mean leuprolide concentrations.
Excretion
Following administration of
LUPRON DEPOT 3.75 mg to 3 patients, less than 5% of the dose was recovered as
parent and M-I metabolite in the urine.
Use In Specific Populations
The pharmacokinetics of LUPRON
DEPOT have not been evaluated in patients with hepatic and renal impairment.
Drug Interactions
No drug-drug interaction
studies have been conducted with LUPRON DEPOT 11.25 mg. However, because
leuprolide acetate for depot suspension is a peptide that is primarily degraded
by peptidase and not by cytochrome P-450 enzymes, drug interactions associated
with cytochrome P-450 enzyme would not be expected to occur.
Clinical Studies
The safety and efficacy of LUPRON DEPOT 11.25 mg for
3-month administration for the following indications has been established based
on adequate and well-controlled adult studies (See Table 8) of LUPRON DEPOT
3.75 mg for 1-month administration and on a single trial of LUPRON DEPOT 11.25
mg for 3-month administration:
- The management of endometriosis, including pain relief
and reduction of endometriotic lesions
- The initial management of endometriosis and for
management of recurrence of symptoms (with norethindrone acetate add-back
therapy)
- Preoperative hematologic improvement of patients with
anemia caused by uterine leiomyomata (with iron therapy)
See Clinical Studies for the results of the
adequate and well-controlled studies in these conditions.
Endometriosis
LUPRON DEPOT Monotherapy
In controlled clinical studies, LUPRON DEPOT 3.75 mg
monthly for six months was shown to be comparable to danazol 800 mg/day in
relieving the clinical sign/symptoms of endometriosis (pelvic pain,
dysmenorrhea, dyspareunia, pelvic tenderness, and induration) and in reducing
the size of endometrial implants as evidenced by laparoscopy.
The clinical significance of a decrease in endometriotic
lesions is not known, and laparoscopic staging of endometriosis does not
necessarily correlate with the severity of symptoms.
LUPRON DEPOT 3.75 mg monthly induced amenorrhea in 74%
and 98% of the patients after the first and second treatment months
respectively. Most of the remaining patients reported episodes of only light
bleeding or spotting. In the first, second and third post-treatment months,
normal menstrual cycles resumed in 7%, 71% and 95% of patients, respectively,
excluding those who became pregnant.
Figure 8 illustrates the percent of patients with
symptoms at baseline, final treatment visit and sustained relief at 6 and 12
months following discontinuation of treatment for the various symptoms
evaluated during the two controlled clinical studies. A total of 166 patients
received LUPRON DEPOT 3.75 mg. Seventy-five percent (N=125) of these elected to
participate in the follow-up period. Of these patients, 36% and 24% are
included in the 6 month and 12 month follow-up analysis, respectively. All the
patients who had a pain evaluation at baseline and at a minimum of one
treatment visit are included in the Baseline (B) and final treatment visit (F)
analysis.
Figure 1: Percent of Patients with Signs/Symptoms of
Endometriosis at Baseline, Final Treatment Visit, and After 6 and 12 Months of
Follow-Up
In a pharmacokinetic/pharmacodynamic study of healthy female subjects (N=20) LUPRON
DEPOT 11.25 mg induced amenorrhea in 85% (N=17) of subjects during the initial
month and 100% during the second month following the injection. All subjects
remained amenorrheic through the remainder of the 12-week dosing interval.
Episodes of light bleeding and spotting were reported by a majority of subjects
during the first month after the injection and in a few subjects at later
time-points. Menses resumed on average 12 weeks (range 2.9 to 20.4 weeks)
following the end of the 12-week dosing interval.
LUPRON DEPOT 11.25 mg produced
similar pharmacodynamic effects in terms of hormonal and menstrual suppression
to those achieved with monthly injections of LUPRON DEPOT 3.75 mg during the
controlled clinical trials for the management of endometriosis and the anemia
caused by uterine fibroids. See also CLINICAL PHARMACOLOGY.
A six-month
pharmacokinetic/pharmacodynamic post-marketing study in 41 women that included
both the 3.75 mg dose (N=20) administered once monthly and the 11.25 mg dose
(N=21) administered once every three months did not reveal clinically
significant differences in terms of efficacy in reducing painful symptoms of
endometriosis or magnitude of the decrease in bone mineral density (BMD)
associated with use of leuprolide acetate. In both treatment groups,
suppression of menses (defined as no new menses for at least 60 consecutive
days) was achieved in 100% of the patients who remained in the study for at
least 60 days. Vertebral bone density measured by dual energy x-ray
absorptiometry (DEXA) decreased compared with baseline by an average of 3.0%
and 2.8% at six months for the two groups, respectively.
LUPRON DEPOT With Norethindrone Acetate Add-Back Therapy
Two clinical studies with treatment duration of 12 months
were conducted to evaluate the effect of coadministration of LUPRON DEPOT and
norethindrone acetate on the loss of bone mineral density (BMD) associated with
LUPRON DEPOT and on the efficacy of LUPRON DEPOT in relieving symptoms of
endometriosis. (All patients in these studies received calcium supplementation
with 1000 mg elemental calcium). A total of 242 women were treated with monthly
administration of leuprolide acetate 3.75 mg (13 injections) and 191 of them
were co-administered 5 mg norethindrone acetate taken daily. The population age
range was 17-43 years old. The majority of patients were Caucasian (87%).
One co-administration study was a controlled, randomized
and double-blind study included 51 women treated monthly with LUPRON DEPOT
alone (See Table 8) and 55 women treated monthly with LUPRON DEPOT plus
norethindrone acetate daily. Women in this trial were followed for up to 24
months after completing one year of treatment. The other study was an
open-label single arm clinical study in 136 women of one year of treatment with
LUPRON DEPOT and daily norethindrone acetate 5 mg, with follow-up for up to 12
months after completing treatment.
The assessment of efficacy was based on the
investigator's or the patient's monthly assessment of five signs or symptoms of
endometriosis (dysmenorrhea, pelvic pain, deep dyspareunia, pelvic tenderness
and pelvic induration).
Table 8 below provides detailed efficacy data regarding
relief of symptoms of endometriosis based on the two studies of
co-administration of leuprolide acetate and norethindrone acetate.
Table 8: Percentages of Patients with Symptoms of
Endometriosis and Mean Clinical Severity Scores
Variable |
Study |
Group |
Percent of Patients with Symptoms |
Clinical Pain Severity Score |
Baseline |
Final |
Baseline |
Final |
N1 |
(%)2 |
(%) |
N1 |
Value3 |
Change |
Dysmenorrhea |
Controlled Study |
LD*4 |
51 |
(100) |
(4) |
50 |
3.2 |
-2.0 |
LD/N† |
55 |
(100) |
(4) |
54 |
3.1 |
-2.0 |
Open Label Study |
LD/N5 |
136 |
(99) |
(9) |
134 |
3.3 |
-2.1 |
Pelvic Pain |
Controlled Study |
LD4 |
51 |
(100) |
(66) |
50 |
2.9 |
-1.1 |
LD/N |
55 |
(96) |
(56) |
54 |
3.1 |
-1.1 |
Open Label Study |
LD/N5 |
136 |
(99) |
(63) |
134 |
3.2 |
-1.2 |
Deep Dyspareunia |
Controlled Study |
LD |
42 |
(83) |
(37) |
25 |
2.4 |
-1.0 |
LD/N |
43 |
(84) |
(45) |
30 |
2.7 |
-0.8 |
Open Label Study |
LD/N |
102 |
(91) |
(53) |
94 |
2.7 |
-1.0 |
Pelvic Tenderness |
Controlled Study |
LD4 |
51 |
(94) |
(34) |
50 |
2.5 |
-1.0 |
LD/N |
54 |
(91) |
(34) |
52 |
2.6 |
-0.9 |
Open Label Study |
LD/N5 |
136 |
(99) |
(39) |
134 |
2.9 |
-1.4 |
Pelvic Induration |
Controlled Study |
LD4 |
51 |
(51) |
(12) |
50 |
1.9 |
-0.4 |
LD/N |
54 |
(46) |
(17) |
52 |
1.6 |
-0.4 |
Open Label Study |
LD/N5 |
136 |
(75) |
(21) |
134 |
2.2 |
-0.9 |
* LD = LUPRON DEPOT 3.75 mg assessment
† LD/N = LUPRON DEPOT 3.75 mg plus norethindrone acetate 5 mg
1 Number of patients that were included in the assessment
2 Percentage of patients with the symptom/sign
3 Value description: 1=none; 2= mild; 3= moderate; 4= severe
4 6-month study duration of treatment
5 12months study duration of treatment with 12 months follow up |
Suppression of menses (menses was defined as three or more consecutive days of menstrual bleeding) was
maintained throughout treatment in 84% and 73% of patients receiving leuprolide
acetate and norethindrone acetate, in the controlled study and open label
study, respectively. The median time for menses resumption after treatment with
leuprolide acetate and norethindrone acetate was 8 weeks.
Changes In Bone Density
The effect of LUPRON DEPOT and
norethindrone acetate on bone mineral density was evaluated by dual energy
x-ray absorptiometry (DEXA) scan in the two clinical trials. For the open-label
study, success in mitigating BMD loss was defined as the lower bound of the 95%
confidence interval around the change from baseline at one year of treatment not
to exceed -2.2%. The bone mineral density data of the lumbar spine from these
two studies are presented in Table 9.
Table 9: Mean Percent Change From Baseline in Bone
Mineral Density of Lumbar Spine
|
LUPRON DEPOT 3.75 mg |
LUPRON DEPOT 3.75 mg plus norethindrone acetate 5 mg daily |
Controlled Study |
Controlled Study |
Open Label Study |
N |
Change (Mean, 95% CI)# |
N |
Change (Mean, 95% CI)# |
N |
Change (Mean, 95% CI)# |
Week 24* |
41 |
-3.2%
(-3.8, -2.6) |
42 |
-0.3%
(-0.8, 0.3) |
115 |
-0.2%
(-0.6, 0.2) |
Week 52† |
29 |
-6.3%
(-7.1, -5.4) |
32 |
-1.0%
(-1.9, -0.1) |
84 |
-1.1%
(-1.6, -0.5) |
* Includes on-treatment measurements that fell within
2-252 days after the first day of treatment.
† Includes on-treatment measurements >252 days after the first day of
treatment.
# 95% CI: 95% Confidence Interval |
The change in BMD following
discontinuation of treatment is shown in Table 10.
Table 10: Mean Percent Change from Baseline in BMD of Lumbar Spine in Post-Treatment Follow-up Period
Post Treatment Measurement |
Controlled Study |
Open Label Study |
LD-Only |
LD/N |
LD/N |
N |
Mean % Change |
95% CI (%) |
N |
Mean % Change |
95% CI (%) |
N |
Mean % Change |
95% CI (%)2 |
Month 8 |
19 |
-3.3 |
(-4.9, -1.8) |
23 |
-0.9 |
(-2.1, 0.4) |
89 |
-0.6 |
(-1.2, 0.0) |
Month 12 |
16 |
-2.2 |
(-3.3, -1.1) |
12 |
-0.7 |
(-2.1, 0.6) |
65 |
0.1 |
(-0.6, 0.7) |
1 Patients with post treatment measurements
2 95% CI (2-sided) of percent change in BMD values from baseline |
These clinical studies demonstrated that co-administration of leuprolide acetate and norethindrone
acetate 5 mg daily is effective in significantly reducing the loss of bone
mineral density that occurs with both LUPRON DEPOT 3.75 mg and 11.25 mg
treatments, and in relieving symptoms of endometriosis.
Fibroids
LUPRON DEPOT 3.75 mg for a period of three to six months was studied in four controlled clinical trials.
In one of these clinical studies, enrollment was based on hematocrit ≤ 30% and/or hemoglobin
≤ 10.2 g/dL. Administration of LUPRON DEPOT 3.75 mg, concomitantly with
iron, produced an increase of ≥ 6% hematocrit and ≥ 2 g/dL
hemoglobin in 77% of patients at three months of therapy. The mean change in
hematocrit was 10.1% and the mean change in hemoglobin was 4.2 g/dL. Clinical
response was judged to be a hematocrit of ≥ 36% and hemoglobin of ≥
12 g/dL, thus allowing for autologous blood donation prior to surgery. At two
and three months respectively, 71% and 75% of patients met this criterion (Table
11). These data suggest however, that some patients may benefit from iron alone
or 1 to 2 months of LUPRON DEPOT 3.75 mg.
Table 11: Percent of
Patients Achieving Hematocrit ≥ 36% and Hemoglobin ≥ 12 GM/DL
Treatment Group |
Week 4 |
Week 8 |
Week 12 |
LUPRON DEPOT 3.75 mg with Iron (N=104) |
40* |
71† |
75* |
Iron Alone (N=98) |
17 |
39 |
49 |
* P-Value < 0.01
† P-Value < 0.001 |
Excessive vaginal bleeding
(menorrhagia or menometrorrhagia) decreased in 80% of patients at three months.
Episodes of spotting and menstrual-like bleeding were noted in 16% of patients
at final visit.
In this same study, a decrease
of ≥25% was seen in uterine and myoma volumes in 60% and 54% of patients
respectively. The mean fibroid diameter was 6.3 cm at pretreatment and
decreased to 5.6 cm at the end of treatment. LUPRON DEPOT 3.75 mg was found to
relieve symptoms of bloating, pelvic pain, and pressure.
In three other controlled
clinical trials, enrollment was not based on hematologic status. Mean uterine
volume decreased by 41% and myoma volume decreased by 37% at final visit as
evidenced by ultrasound or MRI. The mean fibroid diameter was 5.6 cm at
pretreatment and decreased to 4.7 cm at the end of treatment. These patients
also experienced a decrease in symptoms including excessive vaginal bleeding
and pelvic discomfort. Ninety-five percent of these patients became amenorrheic
with 61%, 25%, and 4% experiencing amenorrhea during the first, second, and
third treatment months respectively.
In addition, post-treatment
follow-up was carried out in one clinical trial for a small percentage of
LUPRON DEPOT 3.75 mg patients (N=46) among the 77% who demonstrated a ≥
25% decrease in uterine volume while on therapy. Menses usually returned within
two months of cessation of therapy. Mean time to return to pretreatment uterine
size was 8.3 months. Regrowth did not appear to be related to pretreatment
uterine volume.
Changes In Bone Density
In one of the studies for
fibroids described above, when LUPRON DEPOT 3.75 mg was administered for three
months in uterine fibroid patients, vertebral trabecular bone mineral density
as assessed by quantitative digital radiography (QDR) revealed a mean decrease
of 2.7% compared with baseline. Six months after discontinuation of therapy, a
trend toward recovery was observed.
There is no evidence that pregnancy rates are enhanced or
adversely affected following discontinuation of LUPRON DEPOT 11.25 mg.