GnRH antagonists

Live birth rate of gonadotropin-releasing hormone antagonist versus luteal phase gonadotropin-releasing hormone agonist protocol in IVF/ICSI: a systematic review and meta-analysis

In vitro fertilization (IVF) and embryo transfer and intracytoplasmic sperm injection (ICSI) have allowed millions of infertile couples to achieve pregnancy. As an essential part of IVF/ICSI enabling the retrieval of a high number of oocytes in one cycle, controlled ovarian stimulation (COS) treatment mainly composes of the standard long gonadotrophin-releasing hormone agonist (GnRH-a) protocol and the gonadotrophin-releasing hormone antagonist (GnRH-ant) protocol. However, the effectiveness of GnRH-ant protocol is still debated because of inconsistent conclusions and insufficient subgroup analyses. This systematic review and meta-analysis included a total of 52 studies, encompassing 5193 participants in the GnRH-ant group and 4757 in the GnRH-a group. The findings of this study revealed that the GnRH-ant protocol is comparable with the long GnRH-a protocol when considering live birth as the primary outcome, and it is a favourable protocol with evidence reducing the incidence of ovarian hyperstimulation syndrome in women undergoing IVF/ICSI, especially in women with polycystic ovary syndrome. Further research is needed to compare the subsequent cumulative live birth rate between the two protocols among the general and poor ovarian response patients since those patients have a lower clinical pregnancy rate, fewer oocytes retrieved or fewer high-grade embryos in the GnRH-ant protocol.

Finding of the optimal preparation and timing of endometrium in frozen-thawed embryo transfer: a literature review of clinical evidence

Frozen-thawed embryo transfer (FET) has been a viable alternative to fresh embryo transfer in recent years because of the improvement in vitrification methods. Laboratory-based studies indicate that complex molecular and morphological changes in endometrium during the window of implantation after exogenous hormones with controlled ovarian stimulation may alter the interaction between the embryo and endometrium, leading to a decreased implantation potential. Based on the results obtained from randomized controlled studies, increased pregnancy rates and better perinatal outcomes have been reported following FET. Compared to fresh embryo transfer, fewer preterm deliveries, and reduced incidence of ovarian hyperstimulation syndrome were found after FETs, yet there is a trend of increased pregnancy-related hypertensive diseases in women receiving FET. Despite the increased application of FET, the search for the most optimal priming protocol for the endometrium is still undergoing. Three available FET protocols have been proposed to prepare the endometrium: i) natural cycle (true natural cycle and modified natural cycle) ii) artificial cycle (AC) or hormone replacement treatment cycle iii) mild ovarian stimulation (mild-OS) cycle. Emerging evidence suggests that the optimal timing for FET using warmed blastocyst transfer is the LH surge+6 day, hCG administration+7 day, and the progesterone administration+6 day in the true natural cycle, modified natural cycle, and AC protocol, respectively. Although still controversial, better clinical pregnancy rates and live birth rates have been reported using the natural cycle (true natural cycle/modified natural cycle) compared with the AC protocol. Additionally, a higher early pregnancy loss rate and an increased incidence of gestational hypertension have been found in FETs using the AC protocol because of the lack of a corpus luteum. Although the common clinical practice is to employ luteal phase support (LPS) in natural cycles and mild-OS cycles for FET, the requirement for LPS in these protocols remains equivocal. Recent findings obtained from RCTs do not support the routine application of endometrial receptivity testing to optimize the timing of FET. More RCTs with rigorous methodology are needed to compare different protocols to prime the endometrium for FET, focusing not only on live birth rate, but also on maternal, obstetrical, and neonatal outcomes.

Gonadotropin-Releasing Hormone (GnRH)/GnRH Receptors and Their Role in the Treatment of Endometriosis

Endometriosis, defined as the development of endometrial tissue outside of the uterine cavity, is a common gynecological disorder. The prevalence of pelvic endometriosis approaches 6%-10% in the general female population, and in women with pain, infertility, or both, the frequency is 35%-50%. The gold standard recommended process for diagnosing endometriosis is laparoscopy, an invasive surgical procedure, with or without histologic verification. The currently available nonsurgical treatments include oral contraceptives (estrogen-progestogen preparations), progestogen preparations (containing progesterone derivatives), androgenic hormones (danazol), and gonadotropin-releasing hormone (GnRH) agonists and antagonists. Two GnRH types have been discovered in mammals, GnRH I and GnRH II. In particular, GnRH I is released by the hypothalamus; however, it can be present in various tissues and organs of the body, including neural tissue, where it exerts neuroendocrine, autocrine, and paracrine actions in the peripheral and central nervous system (CNS). Interestingly, another GnRH isoform, GnRH III, has been identified, which has 60% similarity with GnRH I from which it varies by four amino acids. This peptide has been shown to have a significant role in reproduction, specifically in gametogenesis and steroidogenesis. Further research is needed to identify innovative treatment options for endometriosis, such as the therapeutic exogenous administration of GnRH II or antagonists of the GnRH I receptor. In this review, we examined the role of GnRH in endometriosis, outlining the specific actions of GnRH and GnRH receptors (GnRHRs). The innovative use of GnRH analogs and antagonists in the treatment of endometriosis is also discussed.

Ovarian stimulation in IVF couples with severe male factor infertility: GnRH antagonist versus long GnRH agonist

OBJECTIVE

To examine the efficacy of gonadotropin releasing hormone (GnRH) antagonist (GnRH-ant) protocol and the long GnRH agonist (GnRH-a) protocol during in vitro fertilization (IVF) therapy in patients with severe male infertile factors.

METHODS

A total of 983 women with severe male factor infertility undergoing IVF therapy from 2017 to 2020 at one center were retrospectively analyzed. Patients were divided into the GnRH-ant group (n=527) and the GnRH-a group (n=456) according to their ovarian stimulation protocols. Patient baseline characteristics, ovarian stimulation characteristics, and clinical pregnancy outcomes were compared between the groups. The live birth rate was considered the main pregnancy outcome.

RESULTS

GnRH-a group had a higher live birth rate compared with the GnRH-ant group (41.0% versus 31.3%, p=0.002). Moreover, the implantation (32.8% vs. 28.1%, p=0.033), biochemical pregnancy (52.4% versus 44.8%, p=0.017), clinical pregnancy (49.3% versus 39.7%, p=0.002) and ongoing pregnancy rates (43.2% vs. 34.9%, p=0.008) were higher in GnRH-a group. For patients with one embryo transferred, the GnRH-a group demonstrated higher live birth (37.0% vs. 19.4%, p=0.010) and ongoing pregnancy rate (38.9% vs. 24.5%, p=0.046) than the GnRH-ant group. Among patients with two embryos transferred, the live birth rate was also higher in the GnRH-a group than in the GnRH-ant group, with no statistical difference. No significant differences were observed in the biochemical abortion rate, clinical miscarriage rate, early miscarriage rate, late miscarriage rate, heterotopic pregnancy rate, twin pregnancy rate, and birth sex ratio between the two groups.

CONCLUSION

For individuals with severe male infertility undergoing IVF, the GnRH-a protocol is considered a more efficient and feasible strategy with a higher live birth rate compared to the GnRH-ant protocol, especially in single embryo transfer.

Gonadotropin-Releasing Hormone and GnRH Receptor: Structure, Function and Drug Development

BACKGROUND

Gonadotropin-Releasing Hormone (GnRH) is a key element in sexual maturation and regulation of the reproductive cycle in the human organism. GnRH interacts with the pituitary cells through the activation of the Gonadotropin Releasing Hormone Receptors (GnRHR). Any impairments/dysfunctions of the GnRH-GnRHR complex lead to the development of various cancer types and disorders. Furthermore, the identification of GnRHR as a potential drug target has led to the development of agonist and antagonist molecules implemented in various treatment protocols. The development of these drugs was based on the information derived from the functional studies of GnRH and GnRHR.

OBJECTIVE

This review aims at shedding light on the versatile function of GnRH and GnRH receptor and offers an apprehensive summary regarding the development of different agonists, antagonists and non-peptide GnRH analogues.

CONCLUSION

The information derived from these studies can enhance our understanding of the GnRH-GnRHR versatile nature and offer valuable insight into the design of new more potent molecules.

Cost-effectiveness analysis of GnRH-agonist long-protocol and GnRH-antagonist protocol for in vitro fertilization

The gonadotropin releasing hormone agonist (GnRH-a) long-protocols and the GnRH-antagonist protocols are two commonly used protocols for in vitro fertilization (IVF), but their cost-effectiveness has not been studied, especially in China. A retrospective study involving 1638 individuals in GnRH-a long-protocol and 621 in GnRH-antagonist protocol were conducted and a decision tree model analysis was used to analyze the cost-effectiveness. Both direct and indirect costs were calculated. As a result, during the fresh embryo transplantation cycles, there was no significant difference in the rate of ongoing pregnancy between the two protocols, the average cost of per ongoing pregnancy in the GnRH-antagonist protocol was $ 16970.85, and that in the GnRH-agonist long-protocol was $19902.24. The probability of cumulative ongoing pregnancy per start cycle was estimated at 60.65% for the GnRH-antagonist protocol and 71.6% for the GnRH-agonist long-protocol (P < 0.01). Considering the cumulative ongoing pregnancy rate, the mean costs per ongoing pregnancy were estimated at $8176.76 and at $7595.28 with GnRH-antagonist protocol and GnRH-agonist long protocol, respectively. In conclusion, in fresh embryo transplantation cycle, the GnRH-antagonist protocol has economic advantage. However, the GnRH-agonist long protocol is more cost effective considering the cumulative ongoing pregnancy rate in the fresh embryo and frozen embryo transplantation cycles.

Neonatal outcomes following different ovarian stimulation protocols in fresh single embryo transfer

Previous studies suggested ovarian stimulation was associated with lower birth weight and higher risk of preterm delivery (PTD) from fresh embryo transfers (ETs). However, whether the increased risk differs between distinct ovarian stimulation protocols remains unknown. A retrospective cohort study of 38,220 singleton deliveries after fresh single ETs from 2007 to 2013 was conducted. Main outcomes were birth weight and gestational length. Compared with the natural cycle, all ovarian stimulation protocols were associated with a significantly increased risk for PTD, low birth weight (LBW) and small for gestational age (SGA). In subgroup analysis of maternal age under 35 years, luteal support using progesterone, and early cleavage ETs, the significant associations remained for LBW and SGA in gonadotropin-releasing hormone (GnRH) antagonist protocol and for LBW in GnRH agonist protocol. Ovarian stimulation using clomiphene citrate (CC) had the highest increased risks for LBW (Adjusted odds ratio [AOR], 1.58, 95% confidence interval [95% CI], 1.43-1.73) and SGA (AOR, 1.65, 95% CI, 1.50-1.82) compared with natural cycles, and was further associated with PTD and cesarean section. These findings suggest ovarian stimulation was associated with lower birth weight, and CC may have adverse effect on neonatal outcomes in fresh cycles.

Comparisons of GnRH antagonist protocol versus GnRH agonist long protocol in patients with normal ovarian reserve: A systematic review and meta-analysis

OBJECTIVE

To evaluate the effectiveness and safety of gonadotropin-releasing hormone antagonist (GnRH-ant) protocol and gonadotropin-releasing hormone agonist (GnRH-a) long protocol in patients with normal ovarian reserve.

METHODS

We searched the PubMed (1992-2016), Cochrane Library (1999-2016), Web of Science (1950-2016), Chinese Biomedical Database (CBM, 1979-2016), and China National Knowledge Infrastructure (CNKI, 1994-2016). Any randomized controlled trials (RCTs) that compared GnRH-ant protocol and GnRH-a long protocol in patients with normal ovarian reserve were included, and data were extracted independently by two reviewers. The meta-analysis was performed by Revman 5.3 software.

RESULTS

Twenty-nine RCTs (6399 patients) were included in this meta-analysis. Stimulation days (mean difference (MD) [95% confidence interval (CI)] = -0.8 [-1.36, -0.23], P = 0.006), gonadotrophin (Gn) dosage (MD [95% CI] = -3.52 [-5.56, -1.48], P = 0.0007), estradiol (E2) level on the day of human chorionic gonadotrophin (HCG) administration (MD [95% CI] = -365.49 [-532.93, -198.05], P<0.0001), the number of oocytes retrieved (MD [95% CI] = -1.41 [-1.84, -0.99], P<0.00001), the embryos obtained (MD [95% CI] = -0.99 [-1.38, -0.59], P<0.00001), incidence of ovarian hyperstimulation syndrome (OHSS) (OR [95% CI] = 0.69 [0.57, 0.83], P<0.0001) were statistically significantly lower in GnRH-ant protocol than GnRH-a long protocol. However, the clinical pregnancy rate (OR [95% CI] = 0.90 [0.80, 1.01], P = 0.08), ongoing pregnancy rate (OR [95% CI] = 0.88 [0.77, 1.00], P = 0.05), live birth rate (OR [95% CI] = 0.95 [0.74, 1.09], P = 0.27), miscarriage rate (OR [95% CI] = 0.98 [0.69, 1.40], P = 0.93), and cycle cancellation rate (OR [95% CI] = 0.86 [0.52, 1.44], P = 0.57) showed no significant differences between the two groups.

CONCLUSION

GnRH-ant protocol substantially decreased the incidence of OHSS without influencing the pregnancy rate and live birth rate compared to GnRH-a long protocol among patients with normal ovarian reserve.

Triptorelin and cetrorelix induce immune responses and affect uterine development and expressions of genes and proteins of ESR1, LHR, and FSHR of mice

CONTEXT

GnRH immunity can reduce the expression of pituitary GnRH levels, and cause the changes in reproductive behaviors. It is unclear whether triptorelin (TRI) and cetrorelix (CET) immunity influences uterine development and expression of follicle-stimulating hormone receptor (FSHR), luteinizing hormone receptor (LHR), and estradiol receptor 1 (ERS1) in the uterus.

OBJECTIVE

The study investigated the effects of active immunity of GnRH agonist and antagonist on uterine development, microstructures, expression of hormone receptors mRNAs, and proteins in uteri.

MATERIALS AND METHODS

One hundred and five mice were assigned into CET, TRI, and control groups (CG). Mice in CET-1, CET-2, and CET-3 (n = 15) were subcutaneously injected with 10, 20, and 40 μg CET antigens for seven days, respectively. Mice in TRI-1, TRI-2, and TRI-3 were injected with 10, 20, and 40 μg TRI antigens for seven days, respectively. The qPCR and Western blot were implemented to determine expressions of ESR1, LHR and FSHR mRNAs, and proteins.

RESULTS

Compared with CG, the uterine weights of CET-1, CET-2, and CET-3 increased by 42.86, 62.86, and 10.00% on day 35 (p < 0.05), respectively. Uterine weights of TRI-2, TRI-3 reduced by 28.57% and 11.43% (p < 0.05), respectively. The uterine cavity in CET-1, CET-2, and CET-3 increased; the uterine wall became thick. The cytoplasm of endometrial epithelial cells (EEC) increased slightly. In TRI group, the uterine wall thinned. Uterine cavity became narrow slightly in TRI-1. Numbers of uterine glands reduced. The endometrium epithelial thickness (EET) in CET-1 and CET-2 increased by 68.21% and 79.46% (p < 0.05), respectively. EET in TRI-1 was decreased by 13.69%. Uterine wall thicknesses (UWT) in CET-1 and CET-2 were higher than CG, with the increment of 28.59% and 30.72%. UWT of TRI-1, TRI-2, and TRI-3 reduced by 29.35, 15.36, and 14.41%, respectively. Expressions of ESR1, FSHR, and LHR mRNAs in CET and TRI mice increased. ESR1 and FSHR protein levels increased in all experimental mice (p < 0.05), with a maximum of TRI-3. LHR protein levels of the CET decreased. LHR protein levels of TRI group increased, with a maximum of TRI-3 (p < 0.05). ESR1 protein level had significant negative correlations to mRNA expressions of ESR1, LHR, and FSHR.

CONCLUSIONS

CET immunity promoted the uterine development, improved EET and UWT, and also promoted the expressions of ESR1 and FSHR protein levels. It lessened the LHR protein levels. TRI immunity blocked EET and UWT, inhibited uterine growth and development. The efficacy of CET immunity was more obvious than TRI.

GnRH and GnRH receptors in the pathophysiology of the human female reproductive system

BACKGROUND

Human reproduction depends on an intact hypothalamic-pituitary-gonadal (HPG) axis. Hypothalamic gonadotrophin-releasing hormone (GnRH) has been recognized, since its identification in 1971, as the central regulator of the production and release of the pituitary gonadotrophins that, in turn, regulate the gonadal functions and the production of sex steroids. The characteristic peculiar development, distribution and episodic activity of GnRH-producing neurons have solicited an interdisciplinary interest on the etiopathogenesis of several reproductive diseases. The more recent identification of a GnRH/GnRH receptor (GnRHR) system in both the human endometrium and ovary has widened the spectrum of action of the peptide and of its analogues beyond its hypothalamic function.

METHODS

An analysis of research and review articles published in international journals until June 2015 has been carried out to comprehensively summarize both the well established and the most recent knowledge on the physiopathology of the GnRH system in the central and peripheral control of female reproductive functions and diseases.

RESULTS

This review focuses on the role of GnRH neurons in the control of the reproductive axis. New knowledge is accumulating on the genetic programme that drives GnRH neuron development to ameliorate the diagnosis and treatment of GnRH deficiency and consequent delayed or absent puberty. Moreover, a better understanding of the mechanisms controlling the episodic release of GnRH during the onset of puberty and the ovulatory cycle has enabled the pharmacological use of GnRH itself or its synthetic analogues (agonists and antagonists) to either stimulate or to block the gonadotrophin secretion and modulate the functions of the reproductive axis in several reproductive diseases and in assisted reproduction technology. Several inputs from other neuronal populations, as well as metabolic, somatic and age-related signals, may greatly affect the functions of the GnRH pulse generator during the female lifespan; their modulation may offer new possible strategies for diagnostic and therapeutic interventions. A GnRH/GnRHR system is also expressed in female reproductive tissues (e.g. endometrium and ovary), both in normal and pathological conditions. The expression of this system in the human endometrium and ovary supports its physiological regulatory role in the processes of trophoblast invasion of the maternal endometrium and embryo implantation as well as of follicular development and corpus luteum functions. The GnRH/GnRHR system that is expressed in diseased tissues of the female reproductive tract (both benign and malignant) is at present considered an effective molecular target for the development of novel therapeutic approaches for these pathologies. GnRH agonists are also considered as a promising therapeutic approach to counteract ovarian failure in young female patients undergoing chemotherapy.

CONCLUSIONS

Increasing knowledge about the regulation of GnRH pulsatile release, as well as the therapeutic use of its analogues, offers interesting new perspectives in the diagnosis, treatment and outcome of female reproductive disorders, including tumoral and iatrogenic diseases.

Can steroidal ovarian suppression during the luteal phase after oocyte retrieval reduce the risk of severe OHSS?

Background

Ovarian stimulation in IVF cycle results in luteal supraphysiological steroid concentrations especially for high response patients. The aim of this study was to evaluate the efficacy of ovarian steroid hormone suppression in luteal phase after oocyte retrieval for preventing severe ovarian hyperstimulation syndrome (OHSS) in high-risk patients with embryo cryopreservation.

Methods

281 patients with high risk of OHSS were enrolled in this study among 4735 infertile women undergoing their first IVF treatment. The subjects were allocated into treatment and control group. The treatment group (n = 161) received letrozole (n = 43), mifepristone (n = 51), cetrotide (n = 39) and three-drug combinations (n = 28) during the luteal phase after oocyte retrieval, respectively. The control group (n = 120) received no medicine. Fertilization rate, good embryo rate, serum steroid concentration, clinical outcome, and incidence of severe OHSS were compared between the two groups.

Results

On days 2, 5 and 8 after oocyte retrieval, serum estradiol levels in the letrozole and three-drug combination therapy group were significantly lower than in the other three groups at the same time (P < 0.001, respectively). There were no significantly difference of serum luteinizing hormone concentration on days 2, 5 and 8 and progesterone concentration on day 8 after oocyte retreival among the five groups (P > 0.05, respectively). Compared with the control group, the incidence of severe OHSS, the paracentesis rate, the duration of hospitalization and the days of luteal phase in each subgroup of treatment groups was not significantly decreased (P > 0.05, respectively).

Conclusions

Our findings indicate that steroidal ovarian suppression in luteal phase after oocyte retrieval seems to be unable to prevent severe OHSS in high-risk patients with embryo cryopreservation.

Use of the gonadotrophin-releasing hormone antagonist azaline B to control the oestrous cycle in the koala (Phascolarctos cinereus)

The present study examined the effectiveness of the gonadotrophin-releasing hormone (GnRH) antagonist azaline B to suppress plasma LH and 17β-oestradiol concentrations in koalas and its potential application for oestrous synchronisation. In Experiment 1, single subcutaneous injections of azaline B successfully blocked the LH response to exogenous mammalian (m) GnRH in a dose-dependent manner; specifically, 0 mg (n = 4) did not suppress the LH response, 1 mg azaline B (n = 6) suppressed the LH response for 24 h (P < 0.05), 3.3 mg azaline B (n = 8) suppressed the LH response significantly in all animals only for 3 h (P < 0.05), although in half the animals LH remained suppressed for up to 3 days, and 10 mg azaline B (n = 4) suppressed the LH response for 7 days (P < 0.05). In Experiment 2, daily 1 mg, s.c., injections of azaline B over a 10-day period during seasonal anoestrus (June-July; n = 6) suppressed (P < 0.01) the LH response to mGnRH consecutively over the 10-day treatment period and, 4 days after cessation of treatment, the LH response had not recovered. Experiment 3 was designed to test the efficacy of daily 1 mg, s.c., azaline B over 10 days to suppress plasma LH and 17β-oestradiol concentrations and ultimately synchronise timed return to oestrus during the breeding season. Although azaline B treatment did not suppress basal LH or 17β-oestradiol, oestrus was delayed in all treated females by 24.2 days, but with high variability (range 9-39 days). Overall, the present study demonstrates that the GnRH antagonist azaline B is able to inhibit the LH response in koalas to exogenous mGnRH and successfully delay the return to oestrus. However, although azaline B clearly disrupts folliculogenesis, it has not been able to effectively synchronise return to oestrus in the koala.

Treatment of ovarian hyperstimulation syndrome using gonadotropin releasing hormone antagonist: a pilot study

OBJECTIVE

This novel study describes an effective outpatient treatment for ovarian hyperstimulation syndrome (OHSS) that results in rapid normalization of symptoms.

STUDY DESIGN

A total of twenty-seven infertile women undergoing assisted reproductive technique with early-onset OHSS were enrolled in this non-randomized clinical trial in an academic infertility center. In all patients, after complete desensitization with long-term protocol ovarian stimulation with gonadotropins was commenced. Final oocyte maturation was triggered with human chorionic gonadotrophin. Oocytes were collected 36-38 h later using transvaginal-guided follicle aspiration under general anaesthesia. All embryos were frozen and study group patients received two consecutive doses of GnRH antagonist (Cetrotide) and the control group received daily dose of cabergoline for a week.

RESULTS

The research revealed that moderate and severe OHSS, hospitalization or acute care for OHSS and ascites tap were significantly lower in the antagonist (Cetrotide) group. The Patients' satisfaction with Cetrotide was noticeable. No side effect was reported in either group.

CONCLUSION

GnRH antagonists seem to be an effective outpatient treatment with rapid onset activity and minimal side effects for the management of early OHSS.

GnRH receptors in cancer: from cell biology to novel targeted therapeutic strategies

The crucial role of pituitary GnRH receptors (GnRH-R) in the control of reproductive functions is well established. These receptors are the target of GnRH agonists (through receptor desensitization) and antagonists (through receptor blockade) for the treatment of steroid-dependent pathologies, including hormone-dependent tumors. It has also become increasingly clear that GnRH-R are expressed in cancer tissues, either related (i.e. prostate, breast, endometrial, and ovarian cancers) or unrelated (i.e. melanoma, glioblastoma, lung, and pancreatic cancers) to the reproductive system. In hormone-related tumors, GnRH-R appear to be expressed even when the tumor has escaped steroid dependence (such as castration-resistant prostate cancer). These receptors are coupled to a G(αi)-mediated intracellular signaling pathway. Activation of tumor GnRH-R by means of GnRH agonists elicits a strong antiproliferative, antimetastatic, and antiangiogenic (more recently demonstrated) activity. Interestingly, GnRH antagonists have also been shown to elicit a direct antitumor effect; thus, these compounds behave as antagonists of GnRH-R at the pituitary level and as agonists of the same receptors expressed in tumors. According to the ligand-induced selective-signaling theory, GnRH-R might assume various conformations, endowed with different activities for GnRH analogs and with different intracellular signaling pathways, according to the cell context. Based on these consistent experimental observations, tumor GnRH-R are now considered a very interesting candidate for novel molecular, GnRH analog-based, targeted strategies for the treatment of tumors expressing these receptors. These agents include GnRH agonists and antagonists, GnRH analog-based cytotoxic (i.e. doxorubicin) or nutraceutic (i.e. curcumin) hybrids, and GnRH-R-targeted nanoparticles delivering anticancer compounds.

Degarelix, a novel GnRH antagonist, causes minimal histamine release compared with cetrorelix, abarelix and ganirelix in an ex vivo model of human skin samples

AIMS

Early studies on gonadotrophin-releasing hormone (GnRH) antagonists pointed out histamine-mediated anaphylactic reactions as a potential adverse effect of these drug candidates. In this study we have compared the histamine-releasing potential of four approved and marketed antagonists, degarelix, cetrorelix, abarelix and ganirelix in an ex vivo model of human skin samples.

METHODS

Human skin samples were obtained during cosmetic plastic surgery and kept in oxygenated saline solution. The samples were incubated either without or at different concentrations of the antagonists (3, 30 or 300 µg ml(-1) for all, except for ganirelix 1, 10 or 100 µg ml(-1) ). The drug-induced effect was expressed as the increase relative to basal release. The histamine-releasing capacity of the skin was verified by a universal histamine releaser, compound 40/80.

RESULTS

Degarelix had no significant effect on basal histamine release in the 3 to 300 µg ml(-1) concentration range. The effect of ganirelix was moderate causing a nonsignificant increase of 81 ± 27% at the 100 µg ml(-1) concentration. At 30 and 300 µg ml(-1) concentrations abarelix (143 ± 29% and 362 ± 58%, respectively, P < 0.05) and cetrorelix (228 ± 111% and 279 ± 46%, respectively, P < 0.05) caused significantly increased histamine release.

CONCLUSIONS

In this ex vivo human skin model, degarelix displayed the lowest capacity to release histamine followed by ganirelix, abarelix and cetrorelix. These findings may provide indirect hints as to the relative likelihood of systemic anaphylactic reactions in clinical settings.

Luteinizing hormone-releasing hormone antagonists

BACKGROUND

Luteinizing hormone-releasing hormone (LH-RH) plays a central role in the vertebrate reproduction by regulating gonadal activity. Based on its binding to pituitary LH-RH receptors, as well as to LH-RH receptors expressed on cancer cells, LH-RH agonists and antagonists have been developed for different therapeutic applications.

OBJECTIVE/METHOD

Here we give an overview of the most relevant LH-RH antagonists and their therapeutic applications. Recently patented compounds as well as drug formulations and dosage are presented.

CONCLUSION

LH-RH antagonists have found clinical applications in in vitro fertilization, benign prostatic hyperplasia, endometriosis and in the treatment of hormone-dependent tumors. Work in progress is focused on further development of both peptidic and orally active non-peptidic LH-RH antagonists.

GnRH pulsatility, the pituitary response and reproductive dysfunction

GnRH plays an essential role in neuroendocrine control of reproductive function. In mammals, the pattern of gonadotropin secretion includes both pulse and surge phases, which are regulated independently. The pulsatile release of GnRH and LH plays an important role in the development of sexual function and in the normal regulation of the menstrual cycle. The importance of GnRH pulsatility was established in a series of classic studies. Fertility is impaired when GnRH pulsatility is inhibited by chronic malnutrition, excessive caloric expenditure, or aging. A number of reproductive disorders in women with including hypogonadotropic hypogonadism, hypothlamic amenorrhea, hyperprolactinemia and polycystic ovary syndrome (PCOS) are also associated with disruption of the normal pulsatile GnRH secretion. Despite these findings, the molecular mechanisms of this pulsatile GnRH regulation are not well understood. Here, we review recent studies about GnRH pulsatility, signaling and transcriptional response, and its implications for disease.

GnRH antagonists may affect endometrial receptivity

OBJECTIVE

HOXA10 is an essential regulator of endometrial receptivity. To determine the effect of GnRH antagonists on endometrial receptivity, we assessed endometrial HOXA10 expression in GnRH antagonist, GnRH agonist, and natural cycles.

DESIGN

Prospective case-control study.

SETTING

University academic medical center.

PATIENT(S)

Nineteen subjects were included: 12 subjects underwent controlled ovarian hyperstimulation with recombinant FSH and used either a GnRH antagonist or a GnRH agonist; seven control subjects underwent natural cycles.

INTERVENTION(S)

Pipelle endometrial biopsies were obtained 11 days after hCG administration or spontaneous LH surge in untreated cycles, respectively. Immunohistochemistry was used to assess HOXA10 protein expression in endometrial glands and stroma.

MAIN OUTCOME MEASURE(S)

Endometrial HOXA10 protein expression.

RESULT(S)

HOXA10 expression was significantly decreased in endometrial stromal cells in GnRH antagonist-treated cycles compared with GnRH agonist-treated cycles or natural cycle control subjects. There was no significant difference in glandular cell HOXA10 expression among the three groups.

CONCLUSION(S)

Use of GnRH antagonists may be associated with impaired HOXA10 expression in endometrial stromal cells and thus may affect endometrial receptivity.

Evidence of intraovarian follicular dominance effects during controlled ovarian stimulation in a sheep model

OBJECTIVE

To evaluate intraovarian dominance effects in a sheep model and to determine whether local factors, independent of FSH-mediated pathways, are capable of interfering with the final development of subordinate follicles.

DESIGN

Observational, model study.

SETTING

Public research unit.

ANIMAL(S)

Three hundred sixty-four adult Manchega ewes.

INTERVENTION(S)

Synchronization of estrous cycle with intravaginal progestogens and ovarian stimulation with FSH; ovarian ultrasonography, laparoscopies, and embryo recoveries.

MAIN OUTCOME MEASURE(S)

Determination of morphological characteristics and developmental competence of ovarian follicles.

RESULT(S)

The presence of a dominant follicle affects number and viability of embryos from the ipsilateral ovary in females that are treated with high FSH doses; this effect, modulated by season and phase of the estrous cycle, highlights the role of LH in follicular dominance.

CONCLUSION(S)

The current study confirms, in a sheep model, the existence of local effects from dominant follicles over neighboring follicles, by direct action and independently from systemic pathways through FSH modulation.

Effects of gonadotropin-releasing hormone agonist/recombinant follicle-stimulating hormone versus gonadotropin-releasing hormone antagonist/recombinant follicle-stimulating hormone on follicular fluid levels of adhesion molecules during in vitro fertilization

OBJECTIVE

To compare the effects of GnRH-agonist/recombinant rFSH versus GnRH-antagonist/recombinant FSH stimulation on follicular fluid levels of soluble intercellular adhesion molecule (sICAM)-1 and vascular cell adhesion molecule-1 (sVCAM-1) during in vitro fertilization (IVF).

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PATIENT(S)

Seventy-three women underwent IVF.

INTERVENTION(S)

GnRH-agonist/rFSH or GnRH-antagonist/rFSH administration and collection of follicular fluid from 3 small (11-14 mm in diameter) and 3 large (18-21 mm in diameter) follicles on the day of oocyte retrieval.

MAIN OUTCOME MEASURE(S)

Follicular fluid levels of sICAM-1 and sVCAM-1 and intrafollicular estradiol and progesterone were also measured.

RESULT(S)

Women who underwent GnRH-agonist/rFSH showed higher concentrations of sICAM-1 in both small and large follicles were compared with patients who received GnRH-antagonist/rFSH treatment; follicular fluid levels of sVCAM-1 were similar between the 2 stimulation protocols. Content of sICAM-1 in small and large follicles positively correlated with the number of follicles of > or =15 mm and the number of oocytes that were retrieved in both study groups. Concentrations of follicular fluid sVCAM-1 and progesterone were higher in large than in small follicles and were correlated positively to each other in both follicular classes.

CONCLUSION(S)

In IVF, GnRH-agonist/rFSH is associated with higher follicular fluid levels of sICAM-1 compared with GnRH-antagonist/rFSH regimen. Intrafollicular sICAM-1 content may predict ovarian response, and sVCAM-1 appears as an indicator of the degree of follicular luteinization.

Suppression of Follicle Wave Emergence in Cyclic Ewes by Supraphysiologic Concentrations of Estradiol-17beta and Induction with a Physiologic Dose of Exogenous Ovine Follicle-Stimulating Hormone1

Follicle waves are preceded by follicle-stimulating hormone (FSH) peaks in ewes. The purpose of the present study was to see whether estradiol implant treatment would block FSH peaks to create a model in which the effect of the timing and mode of FSH peaks could be studied by ovine FSH (oFSH) injection. In Experiment 1, 10 ewes received estradiol-17beta implants on Day 4 after ovulation (Day 0, day of ovulation); five ewes received large implants, and five ewes received small implants. Five control ewes received empty implants. In Experiment 2, 12 ewes received large implants on Day 4. On Day 9, six ewes received oFSH twice, 8 h apart (0.5 microg/kg; s.c.). Implants were left in place for 10 days in both experiments. In both studies, ovarian ultrasonography and blood sampling was done daily. In Experiment 1, estradiol concentrations were significantly higher in ewes with large implants (10.4 +/- 0.7 pg/ml) compared with controls (3.9 +/- 0.7 pg/ml) and ewes with small implants (5.4 +/- 0.7 pg/ml; P < 0.001). A significant reduction was found in mean FSH peak concentration (31%; P < 0.05) and FSH peak amplitude (45%; P < 0.05) in ewes with large implants compared with controls. Mean and basal FSH concentrations were unaffected by the large implants. The large implants halted follicle-wave emergence between Day 0 and 8 after implant insertion. The small follicle pool (2-3 mm in diameter) was unaffected by the large implants. When oFSH was injected into ewes with large implants, a follicle wave emerged 1.5 +/- 0.5 days after injection; however, in ewes given saline alone, a follicle wave emerged 4.8 +/- 0.8 days after injection (P < 0.01). We concluded that truncation of FSH peaks by estradiol implants prevented follicle-wave emergence, but injection of physiologic concentrations of oFSH reinitiated follicle-wave emergence.

In vivo characterization of a novel GnRH (gonadotropin-releasing hormone) antagonist, LXT-101, in normal male rats

LXT-101 is a newly developed GnRH (gonadotropin-releasing hormone) analogue. In this study, the in vivo pharmacological profile in intact male rats and binding characters of LXT-101 were illustrated, and regulation of mRNA of hormone receptors related to the pituitary-gonadal axis during and after administration was observed to reveal its molecular mechanism of potent effect and reversibility. After single subcutaneous injections, LXT-101 produced a dose- and time-dependent suppression of serum testosterone level. Multiple administrations and osmotic pump implantation revealed that the time of onset and dose needed to maintain the effect of chemical castration decreased as the frequency of injection increased and gave direct proof that depot formulation could significantly improve the duration of antagonist delivery and pharmacological activities compared to the injectable formulation. And LXT-101 showed excellent character of regulating the pituitary-gonadal axis quickly and reversibly. Competitive binding assay showed that LXT-101 could specifically bind a pituitary GnRH receptor with high affinity. These results indicated that LXT-101 is fit for sustained-release formulation and it might possibly be developed as an ideal candidate for treating sex hormone-sensitive tumors and other disorders.

Long-term suppression of reproductive function by a single dose of gonadotropin-releasing hormone antagonists in a sheep model

OBJECTIVE

To determine the effect of single long-acting doses of GnRH antagonists on reproductive function in a sheep model.

DESIGN

Observational, model study.

SETTING

University-affiliated research unit.

ANIMAL(S)

Nine intact mature Merino sheep in experiment 1 and 12 mature Merino-crossed ewes with the ovary autotransplanted to the neck in experiment 2.

INTERVENTION(S)

Synchronization of estrous cycle either with intravaginal progestins or prostaglandin F2alpha analogues and treatment with a single dose of GnRH antagonist; evaluation of reproductive activity, plasma sampling, and ovarian ultrasonography.

MAIN OUTCOME MEASURE(S)

Determination of estrus behavior; plasma concentrations of P, FSH, LH, and inhibin A; and number and size of ovarian follicles.

RESULT(S)

In both experiments, the concentrations of FSH and LH were suppressed when compared with those in control ewes. In experiment 1, the ovulatory cycles were suppressed for > or = 55 days in treated sheep. In experiment 2, there were no follicles sized > or = 5 mm in treated ewes for 50 days.

CONCLUSION(S)

The suppression of the development of large follicles for > or = 30 days after a single injection of a long-acting GnRH antagonist provides a novel convenient method of pretreatment before COS.

Gonadotropins: potential targets for preventive and therapeutic interventions in Alzheimer’s disease

Increased prevalence of Alzheimer’s disease (AD) in women has led to an interest in the role of hormonal changes in the neurodegenerative process. In particular, research has been directed towards investigating the effect of changes in sex hormone levels following reproductive senescence. Clinical trials of hormone-replacement therapy for the prevention of AD are proving contentious, and considerably more research is necessary before the benefit of the hormone replacement strategy can be ascertained. However, evidence is now emerging to support the notion that increased gonadotropin levels may confer an increased risk of AD. Gonadotropins have been implicated in the metabolism of β-amyloid, a key protein that is central to the pathogenesis of AD. Gonadotropin reduction represents a promising new target for therapeutic intervention in AD and, potentially, dementia in general. In this review, the authors discuss the therapeutic and preventive potential of gonadotropin-reducing agents in the management of AD.

Options for Medical Treatment of Myomas

It is evident that complex biochemical interactions are involved in the regulation of myoma growth, and ovarian steroid hormones have significant influence on this process. Current myoma therapies manipulate the hormonal environment to achieve myoma regression and control of bleeding. Although several of these therapies achieve some level of success, further studies are necessary to evaluate the current and long-term effects of these therapies. In clinical medicine each patient must be evaluated thoroughly, and the decision for medical therapy or surgery--and for which medical therapy--needs to be individualized. If one medical therapy does not work, several other effective therapies are available.

Follicular growth, endocrine response and embryo yields in sheep superovulated with FSH after pretreatment with a single short-acting dose of GnRH antagonist

The objective of this study was to characterize follicular development, onset of oestrus and preovulatory LH surge, and in vivo embryo yields of sheep superovulated after treatment with a single dose of 1.5mg of GnRH antagonist (GnRHa). At first FSH dose, ewes treated with GnRH antagonist (n=12) showed a higher number of gonadotrophin-responsive follicles, 2-3mm, than control ewes (n=9, 13.5+/-3.8 versus 5.3+/-0.3, P<0.05). Administration of FSH increased the number of >or=4mm follicles at sponge removal in both groups (19.3+/-3.8, P<0.0005 for treated ewes and 12.7+/-5.4, P<0.01 for controls). Thereafter, a 25% of the GnRHa-treated sheep did not show oestrous behaviour whilst none control sheep failed (P=0.06). The preovulatory LH surge was detected in an 88.9% of control ewes and 66.7% of GnRHa-treated sheep. A 77.8% of control females showed ovulation with a mean of 9.6+/-0.9 CL and 3.3+/-0.7 viable embryos, while ewes treated with GnRHa and showing an LH surge exhibited a bimodal distribution of response; 50% showed no ovulatory response and 50% superovulated with a mean of 12.2+/-1.1 CL and 7.3+/-1.1 viable embryos. In conclusion, a single dose of GnRHa enhances the number of gonadotrophin-dependent follicles able to grow to preovulatory sizes in response to an FSH supply. However, LH secretion may be altered in some females, which can affect the preovulatory LH surge and/or can weak the terminal maturation of ovulatory follicles.

The Evolution of in Vitro Fertilization: Integration of Pharmacology, Technology, and Clinical Care

For the couple having trouble achieving pregnancy, the options and opportunities for assistance have never been brighter. Options such as controlled ovarian hyperstimulation, in vitro fertilization, and intracytoplasmic sperm injection have been developed over the past five decades and provide hope for couples that previously would have been considered infertile. In vitro fertilization and intracytoplasmic sperm injection represent a coalescence of advances in physiology, endocrinology, pharmacology, technology, and clinical care. In vitro fertilization has assisted well over one million couples in their efforts to start or build a family, and the demand for such services continues to increase. The purpose of this manuscript is to review the pharmacological advances that made controlled ovarian hyperstimulation, and therefore in vitro fertilization and intracytoplasmic sperm injection, possible. We will discuss the early stages of gonadotropin use to stimulate ovarian production of multiple mature eggs, the advances in recombinant technology that allowed purified hormone for therapy, and the use of other hormones to regulate the menstrual cycle such that the likelihood of successful oocyte retrieval and embryo implantation is optimized. Finally, we will review current areas that require particular attention if we are to provide more opportunity for infertile couples.

Use of antagonists in ovarian stimulation protocols

Gonadotrophin-releasing hormone (GnRH) antagonists have been introduced in IVF to prevent premature LH surge. They bind competitively to pituitary receptors and prevent endogenous GnRH from exerting any stimulus on pituitary cells, avoiding the initial 'flare-up' effect and decreasing gonadotrophin secretion within a few hours. Pituitary reserve and gonadotrophin synthesis are not affected; therefore, the recovery of pituitary function is rapid. Two different regimes have been described. The multiple-dose protocol involves the administration of 0.25 mg cetrorelix (or ganirelix) daily from day 6-7 of stimulation, or when the leading follicle is 14-15 mm, until human chorionic gonadotrophin (HCG) administration. The single-dose protocol involves the single administration of 3 mg cetrorelix on day 7-8 of stimulation. Both antagonists with either regimen seem to be equally effective in the prevention of the LH surge. Compared with a long luteal agonist protocol, the treatment is shorter and requires a smaller amount of gonadotrophins. Pregnancy rate seems to be lower, but a decrease in the incidence of severe ovarian hyperstimulation syndrome (OHSS) is reported by several studies. A promising aspect of antagonists may be the possibility of making treatment less aggressive. Finally, in antagonist cycles, ovulation triggering is possible by GnRH agonists, avoiding the deleterious effect of HCG and thus preventing OHSS.