DESCRIPTION

ELIGARD® is a sterile polymeric matrix formulation of leuprolide acetate for subcutaneous injection. It is designed to deliver leuprolide acetate at a controlled rate over a one-, three-, four- or six-month therapeutic period.

Leuprolide acetate is a synthetic nonapeptide analog of naturally occurring gonadotropin releasing hormone (GnRH or LH-RH) that, when given continuously, inhibits pituitary gonadotropin secretion and suppresses testicular and ovarian steroidogenesis. The analog possesses greater potency than the natural hormone. The chemical name is 5-oxo-L-prolyl-L-histidyl-L-tryptophyl-L-seryl-L-tyrosyl-D-leucyl-L-leucyl-L-arginyl-N-ethyl-L-prolinamide acetate (salt) with the following structural formula:

ELIGARD® is prefilled and supplied in two separate, sterile syringes whose contents are mixed immediately prior to administration. The two syringes are joined and the single dose product is mixed until it is homogenous. ELIGARD® is administered subcutaneously, where it forms a solid drug delivery depot.

One syringe contains the ATRIGEL® Delivery System and the other contains leuprolide acetate. ATRIGEL® is a polymeric (non-gelatin containing) delivery system consisting of a biodegradable poly (DL-lactide-co-glycolide) (PLGH or PLG) polymer formulation dissolved in a biocompatible solvent, N-methyl-2-pyrrolidone (NMP).

Refer to Table 1 for the delivery system composition and constituted product formulation for each ELIGARD® product.

CLINICAL PHARMACOLOGY

Leuprolide acetate, an LH-RH agonist, acts as a potent inhibitor of gonadotropin secretion when given continuously in therapeutic doses. Animal and human studies indicate that after an initial stimulation, chronic administration of leuprolide acetate results in suppression of testicular and ovarian steroidogenesis. This effect is reversible upon discontinuation of drug therapy.

In humans, administration of leuprolide acetate results in an initial increase in circulating levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH), leading to a transient increase in levels of the gonadal steroids (testosterone and dihydrotestosterone in males, and estrone and estradiol in premenopausal females). However, continuous administration of leuprolide acetate results in decreased levels of LH and FSH. In males, testosterone is reduced to below castrate threshold (≤ 50 ng/dL). These decreases occur within two to four weeks after initiation of treatment. Long-term studies have shown that continuation of therapy with leuprolide acetate maintains testosterone below the castrate level for up to seven years.

PHARMACODYNAMICS

Following the first dose of ELIGARD®, mean serum testosterone concentrations transiently increased, then fell to below castrate threshold (≤ 50 ng/dL) within three weeks for all ELIGARD® concentrations.

Continued monthly treatment with ELIGARD® 7.5 mg maintained castrate testosterone suppression throughout the study. No breakthrough of testosterone concentrations above castrate threshold (> 50 ng/dL) occurred at any time during the study once castrate suppression was achieved (Figure 1).

One patient received less than a full dose of ELIGARD® 22.5 mg at baseline, never suppressed and withdrew from the study at Day 73. Of the 116 patients remaining in the study, 115 (99%) had serum testosterone levels below the castrate threshold by Month 1 (Day 28). By Day 35, 116 (100%) had serum testosterone levels below the castrate threshold. Once testosterone suppression was achieved, one patient (< 1%) demonstrated breakthrough (concentrations > 50 ng/dL after achieving castrate levels) following the initial injection; that patient remained below the castrate threshold following the second injection (Figure 2).

One patient withdrew from the ELIGARD® 30 mg study at Day 14. Of the 89 patients remaining in the study, 85 (96%) had serum testosterone levels below the castrate threshold by Month 1 (Day 28). By Day 42, 89 (100%) of patients attained castrate testosterone suppression. Once castrate testosterone suppression was achieved, three patients (3%) demonstrated breakthrough (concentrations > 50 ng/dL after achieving castrate levels) (Figure 3).

One patient at Day 1 and another patient at Day 29 were withdrawn from the ELIGARD® 45 mg study. Of the 109 patients remaining in the study, 108 (99.1%) had serum testosterone levels below the castrate threshold by Month 1 (Day 28). One patient did not achieve castrate suppression and was withdrawn from the study at Day 85. Once castrate testosterone suppression was achieved, one patient (< 1%) demonstrated breakthrough (concentrations > 50 ng/dL after achieving castrate levels) (Figure 4).

Leuprolide acetate is not active when given orally.

PHARMACOKINETICS

Absorption

ELIGARD® 7.5 mg

The pharmacokinetics/pharmacodynamics observed during three once-monthly injections in 20 patients with advanced prostate cancer is shown in Figure 1. Mean serum leuprolide concentrations following the initial injection rose to 25.3 ng/mL (Cmax) at approximately 5 hours after injection. After the initial increase following each injection, serum concentrations remained relatively constant (0.28 – 2.00 ng/mL).
 

Figure 1 Pharmacokinetic/Pharmacodynamic Response (N=20) to ELIGARD® 7.5 mg – Patients Dosed Initially and at Months 1 and 2

A reduced number of sampling timepoints resulted in the apparent decrease in Cmax values with the second and third doses of ELIGARD® 7.5 mg (Figure 1).

ELIGARD® 22.5 mg

The pharmacokinetics/pharmacodynamics observed during two injections every three months (ELIGARD® 22.5 mg) in 22 patients with advanced prostate cancer is shown in Figure 2. Mean serum leuprolide concentrations rose to 127 ng/mL and 107 ng/mL at approximately 5 hours following the initial and second injections, respectively. After the initial increase following each injection, serum concentrations remained relatively constant (0.2 – 2.0 ng/mL).
 

Figure 2 Pharmacokinetic/Pharmacodynamic Response (N=22) to ELIGARD® 22.5 mg – Patients Dosed Initially and at Month 3

ELIGARD® 30 mg

The pharmacokinetics/pharmacodynamics observed during injections administered initially and at four months (ELIGARD® 30 mg ) in 24 patients with advanced prostate cancer is shown in Figure 3. Mean serum leuprolide concentrations following the initial injection rose rapidly to 150 ng/mL (Cmax) at approximately 3.3 hours after injection. After the initial increase following each injection, mean serum concentrations remained relatively constant (0.1 – 1.0 ng/mL).
 

Figure 3 Pharmacokinetic/Pharmacodynamic Response (N=24) to ELIGARD® 30 mg – Patients Dosed Initially and at Month 4

ELIGARD® 45 mg

The pharmacokinetics/pharmacodynamics observed during injections administered initially and at six months (ELIGARD® 45 mg) in 27 patients with advanced prostate cancer is shown in Figure 4. Mean serum leuprolide concentrations rose to 82.0 ng/mL and 102 ng/mL (Cmax) at approximately 4.5 hours following the initial and second injections, respectively. After the initial increase following each injection, mean serum concentrations remained relatively constant (0.2 – 2.0 ng/mL).
 

Figure 4 Pharmacokinetic/Pharmacodynamic Response (N=27) to ELIGARD® 45 mg - Patients Dosed Initially and at Month 6

There was no evidence of significant accumulation during repeated dosing. Nondetectable leuprolide plasma concentrations have been occasionally observed during ELIGARD® administration, but testosterone levels were maintained at castrate levels.

Distribution

The mean steady-state volume of distribution of leuprolide following intravenous bolus administration to healthy male volunteers was 27 L.1 In vitro binding to human plasma proteins ranged from 43% to 49%.

1

Sennello LT et al. Single-dose pharmacokinetics of leuprolide in humans following intravenous and subcutaneous administration. J Pharm Sci 1986; 75(2): 158–160.

Metabolism

In healthy male volunteers, a 1-mg bolus of leuprolide administered intravenously revealed that the mean systemic clearance was 8.34 L/h, with a terminal elimination half-life of approximately 3 hours based on a two compartment model.1

No drug metabolism study was conducted with ELIGARD®. Upon administration with different leuprolide acetate formulations, the major metabolite of leuprolide acetate is a pentapeptide (M-1) metabolite.

Excretion

No drug excretion study was conducted with ELIGARD®.

Special Populations

Geriatrics

The majority of the patients (approximately 70%) studied in the clinical trials were age 70 and older.

Pediatrics

The safety and effectiveness of ELIGARD® in pediatric patients have not been established (see CONTRAINDICATIONS).

Race

In patients studied, mean serum leuprolide concentrations were similar regardless of race. Refer to Table 2 for distribution of study patients by race.

Renal and Hepatic Insufficiency

The pharmacokinetics of ELIGARD® in hepatically and renally impaired patients have not been determined

Drug-Drug Interactions

No pharmacokinetic drug-drug interaction studies were conducted with ELIGARD®.

CLINICAL STUDIES

One open-label, multicenter study was conducted with each ELIGARD® formulation (7.5 mg, 22.5 mg, 30 mg, and 45 mg) in patients with Jewett stage A though D prostate cancer who were treated with at least a single injection of study drug (Table 3). These studies eva luated the achievement and maintenance of castrate serum testosterone suppression over the duration of therapy (Figures 5–8).

During the AGL9904 study using ELIGARD® 7.5 mg, once testosterone suppression was achieved, no patients (0%) demonstrated breakthrough (concentration >50 ng/dL) at any time in the study.

During the AGL9909 study using ELIGARD® 22.5 mg, once testosterone suppression was achieved, only one patient (< 1%) demonstrated breakthrough following the initial injection; that patient remained below the castrate threshold following the second injection.

During the AGL0001 study using ELIGARD® 30 mg, once testosterone suppression was achieved, three patients (3%) demonstrated breakthrough. In the first of these patients, a single serum testosterone concentration of 53 ng/dL was reported on the day after the second injection. In this patient, castrate suppression was reported for all other timepoints. In the second patient, a serum testosterone concentration of 66 ng/dL was reported immediately prior to the second injection. This rose to a maximum concentration of 147 ng/dL on the second day after the second injection. In this patient, castrate suppression was again reached on the seventh day after the second injection and was maintained thereafter. In the final patient, serum testosterone concentrations > 50 ng/dL were reported at 2 and at 8 hours after the second injection. Serum testosterone concentration rose to a maximum of 110 ng/dL on the third day after the second injection. In this patient, castrate suppression was again reached eighteen days after the second injection and was maintained until the final day of the study, when a single serum testosterone concentration of 55 ng/dL was reported.

During the AGL0205 study using ELIGARD® 45 mg, once testosterone suppression was achieved, one patient (<1%) demonstrated breakthrough. This patient reached castrate suppression at Day 21 and remained suppressed until Day 308 when his testosterone level rose to 112 ng/dL. At Month 12 (Day 336), his testosterone was 210 ng/dL.

Table 3. Summary of ELIGARD® Clinical Studies

			7.5 mg	22.5 mg	30 mg	45 mg
* One patient received less than a full dose at Baseline, never suppressed, and was withdrawn at Day 73 and given an alternate treatment. † All non-eva luable patients who attained castration by Day 28 maintained castration at each timepoint up to and including the time of withdrawal. ‡ One patient withdrew on Day 14. All 7 non-eva luable patients who had achieved castration by Day 28 maintained castration at each timepoint, up to and including the time of withdrawal. § Two patients were withdrawn prior to the Month 1 blood draw. One patient did not achieve castration and was withdrawn on Day 85. All 5 non-eva luable patients who attained castration by Day 28, maintained castration at each timepoint up to and including the time of withdrawal. ¶ Two patients withdrew for reasons unrelated to drug.
Study number			AGL9904	AGL9909	AGL0001	AGL0205
Total Number of patients			120 (117 completed)	117* (111 completed†)	90 (82 completed‡)	111 (103 completed§)
Jewett Stages	Stage A		-	2	2	5
	Stage B		-	19	38	43
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