Ganirelix

Description

Ganirelix acetate was introduced in Germany as prefilled syringes for subcutaneous injections that inhibit premature luteinizing hormone surges in women undergoing controlled ovarian hyperstimulation. This decapeptide analog of luteinizing hormonereleasing hormone (LH-RH) is the second third-generation LH-RH antagonist to be launched after citrorelix (Asta Medica). This highly bioavailable compound immediately blocks the endogenous release by the pituitary gland of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), the hormone that induces ovulation. After discontinuation of the treatment, the pituitary-gonadal function is rapidly recovered due to its short-half life. As a consequence, ganirelix at daily doses of 0.25 mg S.C. efficiently prevented LH surges during clinical trials in infertile women under controlled ovarian hyperstimulation with recombinant FSH before in vitro fertilization or similar reproductive techniques. Unlike first and second-generation gonadotropin-releasing hormone antagonists, ganirelix has minimal histamine-releasing effects thus avoiding the formation of edema of the face and extremities. Ganirelix is very resistant to hydrolysis and, in contrast to the already established cetrorelix, has good water solubility.

Originator

Roche Bioscience (US)

The Uses of Ganirelix

Decapeptide LH-RH antagonist. Used in treatment of infertility.

Manufacturing Process

The abbreviations for common aminoacids are those recommended by IUPACIUB Comission on Biochemical Nomenclature. Other abbreviations useful in describing the replacements of aminoacids in the natural LH-RH peptide are following:
Nal(2) - 3-(2-naphthyl)alanyl; p-Cl-Phe - 3-(p-chlorophenyl)alanyl; Pal(3) - 3- (3-pyridyl)alanyl; ; hArg(Et)2 - NG,NG - bis(ethtyl)homoarginyl; Boc - tbutyloxycarbonyl.
Ganirelix (N-Ac-Nal(2)-D-pCl-Phe-D-Pal(3)-Ser-Tyr-D-hArg(Et)2-Leu-hArg(Et)2- Pro-Ala-NH2) was prepared using the following side chain protection protocol: salt protection for L- and D-hArg(Et)2 (as the chloride) and t-butyl protection for serine.
Amino acids were added to the Nα-Boc-D-Ala-O-Resin (1.0 mmol of resin was replaced in the reaction vessel of 5.0 L Vega 296 automated solid phase peptide synthesizer; in the following sequence:
Acetic anhydride
An acetylation (capping of the resin) was done after Ala, Pro and Leu with N,N'-diisopropyl carbodiimide - 1-hydroxybenztriazole (HBt). Excess HBt (2 equiv.) was used for the coupling of the basic amino acids, hArg(Et)2 and Pal(3).
The following protocols were used to remove the Nα-protecting group following each addition.
Program A: The resin was first washed with CH2Cl2 1 times/1 min, TFA-CH2Cl2 (40/60) 1 times/1 min, TFA-CH2Cl2 (40/60) 1 times/30 min, CH2Cl2 2 5 times/1 min, Et3N-CH2Cl2 (5/95) 3 times/1 min, CH2Cl2 4 times/1 min.
Program B: The resin was first washed with CH2Cl2 1 times/1 min, 4-4.5 N HCl in CH2Cl2/i-PrOH (1/1) 1 times/1 min, 4-4.5 N HCl in CH2Cl2/i-PrOH (1/1) 1 times/30 min, CH2Cl2 3 times/1 min, DMF 1 times/1 min, Et3N-CH2Cl2 (5/95) 3 times/1 min, DMF 1 times/1 min, CH2Cl2 4 times/1 min.
After each deprotecting and washing step, following protocol A or B, the next amino acid in sequence was added and the resin washed with CH2Cl2 3 times/1 min, MeOH 4 times/1 min, DMF 2 times/1 min and CH2Cl2 4 times/1 min.
Program A was used for the removal of the protecting groups on Ala, Pro, LhArg(Et)2, Leu and D-Nal(2).
Program B was used for the removal of the protecting groups on D-hArg(Et)2, Tyr, Ser, D-Pal(3) and p-Cl-Phe.
The crude peptide was first dissolved in 2 M acetic acid and converted to its acetate salt by passage through a column of AG3-X4A resin (Bio-Rad). The acetate was subjected to chromatography on a silica gel column (CH2Cl2/iPrOH/MeOH/H2O/HOAc solvent); the acetate fractions dissolved in H2O and loaded onto a reversed-phase column (Vydec C-18, 15-20 μ), and purified using acetonitrile/TEAP (pH 3). Fractions of the desired purity were combined and diluted with water and reloaded on a reversed-phase HPLC column, then washed with 1% acetic acid in water. The peptide was stripped with a mixture of MeOH/CH3CN/HOAc/H2O (44/50/1/5). The residue was dissolved in acetic acid and precipitated over ether, filtered, washed with ether and dried under vacuum. Amino acid analyses were performed on a Beckman 119CL amino acid analyzer. Samples for amino acid analyses were hydrolyzed with 6 N HCl at 110°C for 20 hrs. Analytical HPLC was performed on a Spectra Physics 8800 chromatograph. Synthesis of ganirelix was confirmed by the presence of a main peak at rt 18 min; no other peak over 1% was noted at rt 16 min.

brand name

Orgalutran

Therapeutic Function

LHRH antagonist

Biochem/physiol Actions

Ganirelix is a decapeptide GnRH antagonist. Ganirelix acts by blocking the action of GnRH upon the pituitary, thus rapidly suppressing the production and action of LH and FSH.