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Ganirelix (Ganirelix Acetate) - Description and Clinical Pharmacology

 
 



FOR SUBCUTANEOUS USE ONLY

DESCRIPTION

Ganirelix Acetate Injection is a synthetic decapeptide with high antagonistic activity against naturally occurring gonadotropin-releasing hormone (GnRH). Ganirelix Acetate is derived from native GnRH with substitutions of amino acids at positions 1, 2, 3, 6, 8, and 10 to form the following molecular formula of the peptide: N-acetyl-3-(2-naphthyl)-D-alanyl-4-chloro-D-phenylalanyl-3-(3-pyridyl)-D-alanyl-L-seryl-L-tyrosyl-N9,N10-diethyl-D-homoarginyl-L-leucyl-N9,N10-diethyl-L-homoarginyl-L-prolyl-D-alanylamide acetate. The molecular weight for Ganirelix Acetate is 1570.4 as an anhydrous free base. The structural formula is as follows:

Ganirelix Acetate

Ganirelix Acetate Injection is supplied as a colorless, sterile, ready-to-use, aqueous solution intended for SUBCUTANEOUS administration only. Each sterile, prefilled syringe contains 250 mcg/0.5 mL of Ganirelix Acetate, 0.1 mg glacial acetic acid, 23.5 mg mannitol, and water for injection adjusted to pH 5.0 with acetic acid, NF and/or sodium hydroxide, NF.

CLINICAL PHARMACOLOGY

The pulsatile release of GnRH stimulates the synthesis and secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The frequency of LH pulses in the mid and late follicular phase is approximately 1 pulse per hour. These pulses can be detected as transient rises in serum LH. At midcycle, a large increase in GnRH release results in an LH surge. The midcycle LH surge initiates several physiologic actions including: ovulation, resumption of meiosis in the oocyte, and luteinization. Luteinization results in a rise in serum progesterone with an accompanying decrease in estradiol levels.

Ganirelix Acetate acts by competitively blocking the GnRH receptors on the pituitary gonadotroph and subsequent transduction pathway. It induces a rapid, reversible suppression of gonadotropin secretion. The suppression of pituitary LH secretion by Ganirelix Acetate is more pronounced than that of FSH. An initial release of endogenous gonadotropins has not been detected with Ganirelix Acetate, which is consistent with an antagonist effect. Upon discontinuation of Ganirelix Acetate, pituitary LH and FSH levels are fully recovered within 48 hours.

Pharmacokinetics

The pharmacokinetic parameters of single and multiple injections of Ganirelix Acetate Injection in healthy adult females are summarized in Table I. Steady-state serum concentrations are reached after 3 days of treatment. The pharmacokinetics of Ganirelix Acetate are dose-proportional in the dose range of 125 to 500 mcg.

TABLE I: Mean (SD) pharmacokinetic parameters of 250 mcg of Ganirelix Acetate following a single subcutaneous (SC) injection (n=15) and daily SC injections (n=15) for seven days.
tmax
h
t1/2
h
Cmax
ng/mL
AUC
ng∙h/mL
CL/F
L/h
Vd/F
L
tmax        Time to maximum concentration
t1/2          Elimination half-life
Cmax      Maximum serum concentration
AUC      Area under the curve; Single dose: AUC0–∞; multiple dose: AUC0–24
Vd          Volume of distribution
CL         Clearance = Dose/AUC0–∞
F            Absolute bioavailability
Ganirelix Acetate
single dose
1.1 (0.3) 12.8 (4.3) 14.8 (3.2) 96 (12) 2.4 (0.2) 1 43.7 (11.4)
Ganirelix Acetate
multiple dose
1.1 (0.2) 16.2 (1.6) 11.2 (2.4) 77.1 (9.8) 3.3 (0.4) 76.5 (10.3)

1 Based on intravenous administration

Absorption

Ganirelix Acetate is rapidly absorbed following subcutaneous injection with maximum serum concentrations reached approximately one hour after dosing. The mean absolute bioavailability of Ganirelix Acetate following a single 250 mcg subcutaneous injection to healthy female volunteers is 91.1%.

Distribution

The mean (SD) volume of distribution of Ganirelix Acetate in healthy females following intravenous administration of a single 250-mcg dose is 43.7 (11.4) liters (L). In vitro protein binding to human plasma is 81.9%.

Metabolism

Following single-dose intravenous administration of radiolabeled Ganirelix Acetate to healthy female volunteers, Ganirelix Acetate is the major compound present in the plasma (50–70% of total radioactivity in the plasma) up to 4 hours and urine (17.1–18.4% of administered dose) up to 24 hours. Ganirelix Acetate is not found in the feces. The 1–4 peptide and 1–6 peptide of Ganirelix Acetate are the primary metabolites observed in the feces.

Excretion

On average, 97.2% of the total radiolabeled Ganirelix Acetate dose is recovered in the feces and urine (75.1% and 22.1%, respectively) over 288 h following intravenous single dose administration of 1 mg [14C]-Ganirelix Acetate. Urinary excretion is virtually complete in 24 h, whereas fecal excretion starts to plateau 192 h after dosing.

Special Populations

The pharmacokinetics of Ganirelix Acetate Injection have not been determined in special populations such as geriatric, pediatric, renally impaired and hepatically impaired patients (see PRECAUTIONS).

Drug-Drug Interactions

Formal in vivo or in vitro drug-drug interaction studies have not been conducted (see PRECAUTIONS). Since Ganirelix Acetate can suppress the secretion of pituitary gonadotropins, dose adjustments of exogenous gonadotropins may be necessary when used during controlled ovarian hyperstimulation (COH).

Clinical Studies

The efficacy of Ganirelix Acetate Injection was established in two adequate and well-controlled clinical studies which included women with normal endocrine and pelvic ultrasound parameters. The studies intended to exclude subjects with polycystic ovary syndrome (PCOS) and subjects with low or no ovarian reserve. One cycle of study medication was administered to each randomized subject. For both studies, the administration of exogenous recombinant FSH [Follistim® (follitropin beta for injection)] 150 IU daily was initiated on the morning of Day 2 or 3 of a natural menstrual cycle. Ganirelix Acetate Injection was administered on the morning of Day 7 or 8 (Day 6 of recombinant FSH administration). The dose of recombinant FSH administered was adjusted according to individual responses starting on the day of initiation of Ganirelix Acetate. Both recombinant FSH and Ganirelix Acetate were continued daily until at least three follicles were 17 mm or greater in diameter at which time hCG [Pregnyl® (chorionic gonadotropin for injection, USP)] was administered. Following hCG administration, Ganirelix Acetate and recombinant FSH administration were discontinued. Oocyte retrieval, followed by in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI), was subsequently performed.

In a multicenter, double-blind, randomized, dose-finding study, the safety and efficacy of Ganirelix Acetate Injection were evaluated for the prevention of LH surges in women undergoing COH with recombinant FSH. Ganirelix Acetate Injection doses ranging from 62.5 mcg to 2000 mcg and recombinant FSH were administered to 332 patients undergoing COH for IVF (see TABLE II). Median serum LH on the day of hCG administration decreased with increasing doses of Ganirelix Acetate. Median serum E2 (17β-estradiol) on the day of hCG administration was 1475, 1110, and 1160 pg/mL for the 62.5-, 125-, and 250-mcg doses, respectively. Lower peak serum E2 levels of 823, 703, and 441 pg/mL were seen at higher doses of Ganirelix Acetate 500, 1000, and 2000 mcg, respectively. The highest pregnancy and implantation rates were achieved with the 250-mcg dose of Ganirelix Acetate Injection as summarized in Table II.

TABLE II: Results from the multicenter, double-blind, randomized, dose-finding study to assess the efficacy of Ganirelix Acetate Injection to prevent premature LH surges in women undergoing COH with recombinant FSH.
Daily dose (mcg) of Ganirelix Acetate Injection
62.5 mcg 125 mcg 250 mcg 500 mcg 1000 mcg 2000 mcg
(Protocol 38602)
No. subjects receiving Ganirelix Acetate 31 66 70 69 66 30
No. subjects with ETET: Embryo Transfer 27 61 62 54 61 27
No. of subjects with LH rise ≥ 10 mIU/mLFollowing initiation of Ganirelix Acetate therapy. Includes subjects who have complied with daily injections 4 6 1 0 0 0
Serum LH (mIU/mL) on day of hCG 1 3.6 2.5 1.7 1.0 0.6 0.3
5th–95th percentiles 0.6–19.9 0.6–11.4 < 0.25–6.4 0.4–4.7 < 0.25–2.2 < 0.25–0.8
Serum E2 (pg/mL) on day of hCG 1475 1110 1160 823 703 441
5th–95th percentiles 645–3720 424–3780 384–3910 279–2720 284–2360 166–1940
Vital pregnancy rateAs evidenced by ultrasound at 5–6 weeks following ET
  per attempt, n (%) 7 (22.6) 17 (25.8) 25 (35.7) 8 (11.6) 9 (13.6) 2 (6.7)
  per transfer, n (%) 7 (25.9) 17 (27.9) 25 (40.3) 8 (14.8) 9 (14.8) 2 (7.4)
Implantation rate (%)Mean (standard deviation) 14.2 (26.8) 16.3 (30.5) 21.9 (30.6) 9.0 (23.7) 8.5 (21.7) 4.9 (20.1)

1 Median values

Transient LH rises alone were not deleterious to achieving pregnancy with Ganirelix Acetate at doses of 125 mcg (3/6 subjects) and 250 mcg (1/1 subjects). In addition, none of the subjects with LH rises ≥ 10 mIU/mL had premature luteinization indicated by a serum progesterone above 2 ng/mL.

A multicenter, open-label, randomized study was conducted to assess the efficacy and safety of Ganirelix Acetate Injection in women undergoing COH. Follicular phase treatment with Ganirelix Acetate 250 mcg was studied using a luteal phase GnRH agonist as a reference treatment. A total of 463 subjects were treated with Ganirelix Acetate by subcutaneous injection once daily starting on Day 6 of recombinant FSH treatment. Recombinant FSH was maintained at 150 IU for the first 5 days of ovarian stimulation and was then adjusted by the investigator on the sixth day of gonadotropin use according to individual responses. The results for the Ganirelix Acetate arm are summarized in Table III.

TABLE III: Results from the multicenter, open-label, randomized study to assess the efficacy and safety of Ganirelix Acetate Injection in women undergoing COH.
Ganirelix Acetate 250 mcg
(Protocol 38607)
Some centers were limited to the transfer of ≤ 2 embryos based on local practice standards
No. subjects treated 463
Duration of GnRH analog (days) 1 2 5.4 (2.0)
Duration of recombinant FSH (days) 9.6 (2.0)
Serum E2 (pg/mL) on day of hCG 3
5th–95th percentiles
1190
373–3105
Serum LH (mIU/mL) on day of hCG
5th–95th percentiles
1.6
0.6–6.9
No. of subjects with LH rise ≥ 10 mIU/mLFollowing initiation of Ganirelix Acetate therapy 13
No. of follicles > 11 mm 10.7 (5.3)
No. of subjects with oocyte retrieval 440
No. of oocytes 8.7 (5.6)
Fertilization rate 62.1%
No. subjects with ETET: Embryo Transfer 399
No. of embryos transferred 2.2 (0.6)
No. of embryos 6.0 (4.5)
Ongoing pregnancy rateAs evidenced by ultrasound at 12–16 weeks following ET
  per attempt, n (%)Includes one patient who achieved pregnancy with intrauterine induction 94 (20.3)
  per transfer, n (%) 93 (23.3)
Implantation rate (%) 15.7 (29)

1 Restricted to subjects with hCG injection
2 Mean (standard deviation)
3 Median values

The mean number of days of Ganirelix Acetate treatment was 5.4 (2–14).

LH Surges

The midcycle LH surge initiates several physiologic actions including: ovulation, resumption of meiosis in the oocyte, and luteinization. In 463 subjects administered Ganirelix Acetate Injection 250 mcg, a premature LH surge prior to hCG administration, (LH rise ≥ 10 mIU/mL with a significant rise in serum progesterone > 2 ng/mL, or a significant decline in serum estradiol) occurred in less than 1% of subjects.

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