Efficacy and safety of ganirelix acetate versus leuprolide acetate in women undergoing controlled ovarian hyperstimulation

Gonadotropin-releasing-hormone-receptor antagonists

Pulsatile gonadotropin-releasing hormone (GnRH) stimulates the pituitary secretion of both luteinising hormone (LH) and follicle-stimulating hormone (FSH) and thus controls the hormonal and reproductive function of the gonads. Blockade of GnRH effects may be wanted for a variety of reasons-eg, to prevent untimely luteinisation during assisted reproduction or in the treatment of sex-hormone-dependent disorders. Selective blockade of LH/FSH secretion and subsequent chemical castration have previously been achieved by desensitising the pituitary to continuously administered GnRH or by giving long-acting GnRH agonists. Only recently have GnRH-receptor antagonists, that immediately block GnRH's effects, been developed for clinical use with acceptable pharmacokinetic, safety, and commercial profiles. In assisted reproduction, these compounds seem to be as effective as established therapy but with shorter treatment times, less use of gonadotropic hormones, improved patient acceptance, and fewer follicles and oocytes. All current indications for GnRH-agonist desensitisation may prove to be indications for a GnRH antagonist, including endometriosis, leiomyoma, and breast cancer in women, benign prostatic hypertrophy and prostatic carcinoma in men, and central precocious puberty in children. However, the best clinical evidence so far has been in assisted reproduction and prostate cancer.

Use of third generation gonadotropin-releasing hormone antagonists in in vitro fertilization-embryo transfer: a review

Before gonadotropin-releasing hormone agonists (GnRHa) became available, approximately 20% of stimulated cycles within an in vitro fertilization (IVF) program were cancelled due to premature LH surges. By using the GnRHa to prevent LH surges via gonadotrope GnRH receptor down-regulation and desensitization, this percentage decreased to about 2%, and concomitantly, the IVF and pregnancy rates per cycle initiated were increased. Several treatment schedules currently are in use, including the so-called "long protocol," in which the GnRHa is begun in the luteal phase and down-regulation occurs before the start of the gonadotropin-stimulation treatment phase. This is generally the most effective regimen and is presently the most frequently used protocol. However, it has some disadvantages, such as hypoestrogenic side effects and an increase in the number of ampules of FSH or hMG required for adequate stimulation. There is a new generation of GnRH antagonists now clinically available, that has been able to minimize the potential side effects and provide reliable antagonism at the GnRH receptor. These agents seem better suited than GnRHa for assisted reproductive technology (ART) cycles inasmuch as they can prevent LH surges without requiring complete gonadotropin suppression. We have reviewed the current literature concerning their use in IVF cycles.

Gonadotrophin-releasing hormone antagonists for assisted conception

BACKGROUND

Over the last two decades, a long protocol of Gonadotrophin-releasing hormone agonist (GnRHa) to prevent premature LH surges has been the standard treatment for ovarian stimulation in assisted reproduction. In the long protocols (with GnRHa started either in the mid luteal phase or in the early follicular phase of the preceding cycle) gonadotrophin administration is delayed until pituitary desensitization has been achieved, which usually takes 2-3 weeks. Gonadotrophin-releasing hormone antagonists produce immediate suppression of gonadotrophin secretion, hence, they can be given after starting gonadotrophin administration. This will result in dramatic reduction in the duration of treatment cycle and will avoid estrogen deprivation symptoms associated with GnRH agonist induced down-regulation. Assuming comparable clinical outcome, these benefits would justify a change from the standard long protocol of GnRH agonists to the new GnRH antagonist regimens.

OBJECTIVES

To compare the efficacy of gonadotrophin-releasing hormone (GnRH) antagonists with the standard long protocol of GnRH agonists for controlled ovarian hyperstimulation in assisted conception.

SEARCH STRATEGY

Search strategies included on-line searching of the MEDLINE and EMBASE databases and the Cochrane Menstrual Disorders and Subfertility Group's Specialised Register from 1982 to 2001, and hand searching of bibliographies of relevant publications and reviews, and abstracts of scientific meetings.

SELECTION CRITERIA

Only randomised controlled studies comparing different protocols of GnRH antagonists with GnRH agonists in assisted conception cycles were included in this review.

DATA COLLECTION AND ANALYSIS

Data were extracted into 2 x 2 tables. For the primary outcomes, clinical pregnancy per woman randomised and prevention of premature LH surge, the overall common odds ratio (OR) and the risk difference with 95% confidence interval (CI) were calculated after verifying the presence of homogeneity of treatment effect across all trials. Secondary outcomes considered were the number of oocytes retrieved, clinical pregnancy per oocyte retrieval and per embryo transfer, spontaneous abortion, incidence of severe ovarian hyperstimulation syndrome and the amount of gonadotrophins used. Where relevant data were missing or unclear the authors were consulted.

MAIN RESULTS

Five trials comparing the new fixed protocol of GnRH antagonist to the long protocol of GnRH agonist fulfilled the inclusion criteria and were included. In four studies, the multiple low-dose (0.25 mg) antagonist regimen was applied and in one study, the single high-dose (3 mg) antagonist regimen was investigated. In all trials, reference treatment included a long protocol of GnRHa (buserelin, leuprorelin or triptorelin) starting in the mid-luteal phase of the preceding cycle. In comparison to the long protocol of GnRHa, the overall OR for the prevention of premature LH surges was 1.76 (95% CI 0.75, 4.16), which is not statistically significant. There was a significantly fewer clinical pregnancies in those treated with GnRH antagonists (OR 0.78, 95% CI 0.62, 0.97). The absolute treatment effect (ATE) was calculated to be 5%. The number needed to treat (NNT) was 20. There was a statistically significant reduction in incidence of severe ovarian hyperstimulation syndrome, (RR 0.36, 95% CI 0.16, 0.80) using antagonist regimens as compared to the long GnRHa protocol.

REVIEWER'S CONCLUSIONS

The new fixed GnRH antagonist protocol (i.e. with antagonist start fixed on day 6 of gonadotrophin stimulation) is a short and simple protocol with a significant reduction in incidence of severe OHSS but a lower pregnancy rate compared to the GnRH agonist long protocol. There is a non significant difference between both protocols regarding prevention of premature LH surge. The clinical outcome may be further improved by developing more flexible antagonist regimens taking into account individual patient characteristics. The GnRH antagonist flexible regimen should be the area of research in the near future.