Ovarian stimulation for assisted reproduction with HMG and ...

Human Reproduction vol.15 no.5 pp.1015–1020, 2000

Ovarian stimulation for assisted reproduction with HMG and concomitant midcycle administration of the GnRH antagonist Cetrorelix according to the multiple dose protocol: a prospective uncontrolled phase III study R.E.Felberbaum1,4, C.Albano2, M.Ludwig1, H.Riethmu¨ller-Winzen3, M.Grigat3, P.Devroey2 and K.Diedrich1, on behalf of the European Cetrorelix Study Group* 1Department

of Obstetrics and Gynaecology at the Medical University of Lu¨beck, Germany, 2Centre for Reproductive Medicine of the Dutch-Speaking Free University of Brussels, Belgium and 3ASTA-Medica AG, Frankfurt/Main, Germany 4To

whom correspondence should be addressed

A total of 346 women with normal ovulatory function was stimulated with human menopausal gonadotrophins (HMG) to attain ovarian stimulation for IVF or intracytoplasmic sperm injection (ICSI). Stimulation with HMG started on cycle day 2 or 3. After 6 days of stimulation, Cetrorelix in its minimum effective multiple dose of 0.25 mg/day, was administered daily until induction of ovulation. In total, 333 patients (96.2%) reached the day of HCG administration, and 324 (93.6%) underwent oocyte retrieval. A mean of 25.2 ampoules of HMG was applied for a mean of 10.4 days. Cetrorelix was administered for a mean time lapse of 5.7 days. The mean normal fertilization rate was 60% in the IVF group and 59% in the ICSI group. Seventy pregnancies were attained, reflecting an ongoing clinical pregnancy rate of 24% per transfer. The ongoing clinical implantation rate was 11.4%. Only three cases of raised luteinizing hormone (LH) (≥10 IU/l) with increased progesterone secretion (≥1 ng/ml) were observed after initiation of Cetrorelix administration, reflecting an incidence of premature luteinization of 0.9%. The abortion rate was 17%. The incidence of severe ovarian hyperstimulation syndrome (World Health Organization grade III) was as low as 0.6%. Key words: Cetrorelix/gonadotrophin-releasing hormone antagonists/human menopausal gonadotrophins/ovarian stimulation

*Prof. Dr K.H.R.Diedrich and Dr med. R.E.Felberbaum, Lu¨beck, Germany; Prof. Dr M.Breckwoldt, Dr med. C.Keck and Dr med. D.Vogelsang, Freiburg, Germany; Prof. Dr H. van der Ven, Prof. Dr D. Krebs, Dr D.M.Indefrei and Dr C.C.Dibelius, Bonn, Germany; Dr E.Siebzehnru¨bl and Prof. Dr N. Lang, Erlangen, Germany; Prof. Dr F.Fischl and Dr A.Obruca, Wien, Vienna, Austria; Prof. Dr W.Urdl, Dr H.Auner and Dr A.Giuliani, Graz, Austria; Prof. Dr J.-R.Zorn, Dr N.Ledee and Dr A.Coffineau, Paris, France; Prof. Dr B.C.Tarlatzis, Thessaloniki, Greece; Prof. Dr P.G.Crosignani and Dr G.Ragni, Milan, Italy; Prof. Dr M.Filicori, Prof. Dr C.Flamigni and Dr G.E.Cognigni, Bologna, Italy; Prof. Dr R.Ron-El, Zerefin, Israel; Dr P.N.Barri and Dr F.Martinez, Barcelona, Spain; Dr V.von Du¨ring and Prof. Dr A.Sunde, Trondheim, Norway. © European Society of Human Reproduction and Embryology

Introduction One of the main causes for a relatively low efficacy of ovarian stimulation with human menopausal gonadotrophin (HMG) only was the onset of premature luteinization in about 15– 20% of treatment cycles. The incidence of this event, with its negative impact on oocyte and embryo quality as well as on the pregnancy rates attained, could be lowered to below 2% by the introduction of gonadotrophin-releasing hormone (GnRH) agonists into stimulation protocols for assisted reproduction techniques (Porter et al., 1984; Stanger and Yovich, 1985; Wildt et al., 1986). The long agonistic protocol, which aims to achieve complete desensitization of GnRH receptors before the start of HMG administration, has become the ‘gold standard’ for ovarian stimulation in assisted reproduction techniques (Biljan and Tan, 1998). Recently, the GnRH antagonist Cetrorelix (ASTA-Medica AG, Frankfurt/Main, Germany) has been investigated for ovarian stimulation in assisted reproduction techniques. Cetrorelix has proved to be reliable in preventing the onset of premature luteinizing hormone (LH) surges during HMG stimulation for assisted reproduction techniques, as well by daily injections from 5 or 6 days of stimulation onwards as by a single injection on stimulation day 7 (Diedrich et al., 1994; Olivennes et al., 1994, 1995; Felberbaum et al., 1995, 1996; Albano et al., 1996). Pregnancy rates of about 30% per transfer reported seemed to be very promising (Albano et al., 1997). However, reports regarding the possibility of lowering the amount of HMG ampoules to obtain satisfactory follicular maturation by using GnRH antagonists instead of a desensitizing protocol have been contradictory (Albano et al., 1996; Felberbaum et al., 1996). No data regarding the incidence of serious ovarian hyperstimulation syndrome (OHSS) under these treatment modalities have been available until now. Overall, there was clearly a need to obtain more data regarding efficacy and safety aspects of this new therapeutic approach to ovarian stimulation for assisted reproduction techniques. This report details a prospective uncontrolled study including 346 patients treated with Cetrorelix in its minimum effective dose of 0.25 mg/day, according to the multiple dose administration protocol.

Materials and methods After having obtained approval from the ethical boards of all medical centres involved in the study, 346 healthy female partners were treated in this open-label, multicentre, multinational phase III study with Cetrorelix in its minimum effective multiple dose of 0.25 mg/ day and HMG according to the multiple dose protocol, which has been described extensively before (Diedrich et al., 1994). Fourteen centres in eight European countries—forming the European Cetrorelix

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Table I. Numbers of patients distributed to the separate centres Country

Centre no.

No. of patients treated (ITT population)

Germany Germany Germany Germany Austria Austria France Greece Italy Italy Italy Israel Spain Norway

01 02 03 04 05 06 07 08 09 10 11 12 13 14

43 11 24 11 30 24 27 47 Never started 24 17 40 19 29

ITT ⫽ intention to treat.

Table II. Main gynaecological characteristics of patients Characteristic

Aetiology

% present

Cause of infertility

Endometriosis Cervical mucus problems Tubal Other Unknown Sterility of male partner Early abortion Late abortion Ectopic pregnancy Parity Ever sterilized If sterilized, reversed PAP I PAP II Absent

6.6 0.3 41.6 6.9 9.2 47.7 24.6 1.7 12.7 14.5 1.4 n⫽2 51.7 48.0 n⫽1

Further fertility characteristics (history of)

Cervical smear results

LH rise (LH 艌10 IU/l and progesterone 艌1 ng/ml) before HMG day 6, Cetrorelix was administered immediately in order to interrupt a possible spontaneous ovulation and therefore to rescue the cycle. Each Cetrorelix injection was given after a blood sample had been taken for hormone assessments [follicle stimulating hormone (FSH), LH, oestradiol and progesterone] at intervals of 24 ⫾ 2 h. In cases of cycle cancellation before HCG administration due to multifollicular development (艌12 follicles ⬎15 mm in diameter) and/or oestradiol concentrations ⬎4000 pg/ml, the Cetrorelix administration was continued for at least one week. This procedure was followed in order to prevent spontaneous ovulation accompanied by the release of multiple oocytes, the increased risk of development of OHSS, and multiple pregnancies. Since the investigation was designed as an open study, all patients were treated in accordance with the same schedule. To proceed with the administration of 10 000 IU of HCG (Predalon®; Serono, Geneva, Switzerland/Choragon®; Ferring GmbH), the following prerequisites had to be fulfilled: at least one follicle with a diameter of 艌20 mm or an oestradiol concentration 艌1200 pg/ml. Luteal phase support was given according to the centre’s rules regarding start, duration, medication and dosage. The protocol allowed two medications: either injections of HCG according to the centre’s rules (though not in the case of oestradiol concentration 艌2000 pg/ ml), or vaginal administration of progesterone (e.g. 600 mg per day for 14 days). Concentrations of LH, FSH, oestradiol and progesterone were measured regularly on the day of screening, HMG day 1, Cetrorelix day 1, and during the Cetrorelix administration on each morning and on the evening of ovulation induction before HCG administration. Furthermore, hormone concentrations were measured at the day of oocyte retrieval, day of embryo transfer, and 6–8 days after embryo transfer. All analyses were performed locally at each centre’s laboratory. However, to enable an additional analysis of these hormones in a central laboratory, a second serum sample was taken at the same time as the morning blood collection. The second serum samples were immediately frozen and stored at –20°C until being analysed at the clinical chemistry laboratory of ASTA-Medica AG.

PAP ⫽ Papanicolaou smear test.

Study Group—participated in this study, as outlined in Table I. The infertility could be treated by ovarian stimulation for IVF or intracytoplasmic sperm injection (ICSI), as shown in Table II. The women had to be between 18 and 39 years of age, with normal menstrual cycles of range 24–35 days, and an intra-individual variation of ⫾ 3 days. The mean age of the patients was 32 ⫾ 4 years, and the mean body weight 62 ⫾ 10 kg. No more than three IVF procedures should have taken place in the past. A normal uterus and at least one functioning ovary were basic requirements. All patients started treatment with two ampoules of HMG and remained on that dose for 5 days. Thereafter, the stimulation procedure with respect to the amount of HMG administered per day was handled variably in the separate centres. Cetrorelix (ASTA-Medica AG, Frankfurt/Main, Germany) was to be injected once daily in doses of 0.25 mg s.c. into the lower abdominal wall, starting from day 6 of treatment with HMG (Humegon®; Organon, Oss, The Netherlands/Menogon®, Ferring GmbH, Kiel, Germany) of the ovarian stimulation cycle up to and including the day of human chorionic gonadotrophin (HCG) administration. Although Cetrorelix should always have been initiated on stimulation day 6, some centres started the administration on day 5 in some patients. This was considered to be a minor protocol violation and did not lead to patients’ exclusion. In case, of premature

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Statistical methods All statistical evaluations and analyses were performed using SAS™ 6.09 (SAS Institute Inc., Cary, NC, USA). The primary aim of the present study was to estimate the response rate defined as successful ovarian stimulation, the number of patients reaching the day of HCG, the rate of patients with oocyte retrieval, embryo transfers and pregnancies, as well as to assess serious adverse events. As a response rate of at least 95% was to be expected in order to obtain lower onesided 95% confidence limits (CL) of 92.5%, a sample size of 319 patients was required. Assuming a rate of about 6% for non-evaluable patients, the inclusion of 340 patients seemed to be appropriate. A sample size of 340 patients and a pregnancy rate of about 20% would lead to about 65 babies being delivered. For this reason at least one adverse experience would have been observed with 95% probability given an assumed incidence of 艌4.5%. One-sided 95% lower CL were calculated according to Clopper–Pearson for the efficacy parameters.

Results After having obtained fully informed consent, 352 patients were screened for enrolment into the study and 346 patients started HMG stimulation and concomitant Cetrorelix treatment. Six patients were screened, but received neither HMG nor

Phase III study of HMG with Cetrorelix in ovarian stimulation

Table III. Screening for luteinizing hormone (LH) rises according to local laboratory data Total Yes (n) (n)

LH 艌10 IU/l, including HMG day 6 LH 艌10 IU/l, excluding HMG day 6 LH risesc, including HMG day 6 LH risesc, excluding HMG day 6

Figure 1. Course of median luteinizing hormone (LH) concentrations (IU/l) under ovarian stimulation with human menospausal gonadotrophin (HMG) and concomitant gonadotrophin-releasing hormone antagonist treatment (Cetrorelix, 0.25 mg/day). All hormone analyses were performed in a central laboratory. n ⫽ number of patients with serum samples available for hormone analysis. Vertical line indicates missing HMG treatment days before day of human chorionic gonadotrophin (HCG) administration. ET ⫽ embryo transfer; OPU ⫽ oocyte retrieval.

Cetrorelix. Four patients out of these six did not fulfil the criteria set for the start with HMG, namely because their FSH concentration was ⬎10 mIU/ml or progesterone concentration ⬎1 ng/ml. One patient showed a Papanicolaou (PAP) IV result at screening, which was defined as an exclusion criterion. One patient withdrew due to spontaneous pregnancy after screening. All of the remaining 346 patients were evaluated for efficacy and safety criteria, as well as with respect to compliance. As expected, the HMG stimulation had an important impact on hormone concentrations. FSH rose continuously to a mean concentration of 13.8 mIU/ml (day of HCG administration) as long as the HMG treatment continued. Concentrations of oestradiol increased to a mean of 1544 pg/ml (morning value; central laboratory) on the day of HCG injection. LH concentrations were clearly suppressed during the entire stimulation period (Figure 1). The median evening value on the day of HCG injection was 1.0 IU/l (evening value, central laboratory). The median duration of Cetrorelix treatment was 5 days (mean 5.7 days; range 1–15 days). Among 346 cycles, none had to be cancelled because of allergic, anaphylactoid, local hypersensitivity or other adverse reactions of the patient. A mean of 25.2 ampoules (median 23 ampoules) of HMG were given for a mean of 10.4 days. HMG was administered in all patients for a minimum of 6 and up to a maximum of 19 days. Primary parameters of efficacy Among 346 patients treated according to the described treatment modalities, 333 fulfilled the criteria for administration of HCG to induce final oocyte maturation. This reflected a 96.2% efficacy rate in respect of the primary parameter of success with a lower 95% CL of 94.1%. Two of the patients without HCG administration showed a rise in LH, one on HMG day 7 and one on HMG day 13. In

aLower confidence limit (CL), bData post human menopausal

No n

%

95% CLa

346

27

319

92.2

89.4

346

19b

326b

94.2

91.7

346 346

12 10b

334 335b

96.5 96.8

94.4 94.8

calculated according to Clopper–Pearson. gonadotrophin (HMG) day 6 are missing

from one patient. cAccording to protocol definition: LH 艌10 IU/l and progesterone 艌1 ng/ml.

Table IV. Screening for luteinizing hormone (LH) rises according to central laboratory data Total Yes (n) (n)

LH 艌10 IU/l, including HMG day 6 LH 艌10 IU/l, excluding HMG day 6 LH risesc, including HMG day 6 LH risesc, excluding HMG day 6 aLower confidence limit (CL), bData post human menopausal

337

13

No n

%

95% CLa

324

96.1

93.9

337

6b

330b

97.9

96.1

337 337

6 3b

331 333b

98.2 98.8

96.5 97.3

calculated according to Clopper—Pearson. gonadotrophin (HMG) day 6 are missing

from one patient. cAccording to protocol definition: LH 艌10 IU/l and progesterone 艌1 ng/ml.

the case of the first patient, no central laboratory analysis was available. However, this patient was considered to be one of the major protocol violators, as the FSH concentration at HMG day 1 was ⬎12 mIU/ml, and HMG started on day 4 of the cycle instead of day 2 or 3. Finally, the cycle was cancelled in this case as the woman refused to continue ovarian stimulation. In the case of the second patient, the response to ovarian stimulation was very poor, and although progesterone did not reach a concentration of 1 ng/ml, the cycle was cancelled because LH values were above 24 IU/l. Premature rises of LH The incidence of premature LH rises above 10 IU/l during stimulation, and premature luteinization of the follicles as indicated by progesterone values above 1 ng/ml, were analysed once by the results from the local laboratory, and once by the results from the central laboratory (Tables III and IV). Generally, the central laboratory provided slightly lower LH values. Including HMG day 6 for analysis led to an incidence of LH rises as defined by the study protocol (LH 艌10 IU/l and progesterone 艌1 ng/ml) of 3.5% with 95% CL of 5.6% according to local laboratory values, and 1.8% (95% CL ⫽ 3.5%) according to central laboratory data. This incidence 1017

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Table V. Cumulus–oocyte complexes (COC), fertilization rates, embryos, quality of embryos, implantation rates, pregnancy rates and abortion rate

Patients (n) COC (n) Mature oocytes (IVF) Metaphase II oocytes (ICSI) Fertilization rate (%)b,c Embryos (n) Excellent Good Fair Patients with embryo transfer Clinical pregnancies (treatment cycle) Pregnancy rate/embryo transfer Babies born after embryo transfer Babies born/replaced embryos (%) Miscarriages

aIVF

(n) (% COC)b (n) (% COC)b (n) (% of all) (n) (% of all) (n) (% of all) (n) (n) (%) (n) (%)

IVF

ICSIa

Overall

149 1279 811 63.0 ⫾ 35.6 1252

173 1692

322 2971

60.4 ⫾ 26.3 605 211 34.9 281 46.4 113 18.7 134 30 22.4 33 9.3 6 20.0

74.7 ⫾ 25.0 58.2 ⫾ 24.5 647 219 33.8 298 46.1 130 20.1 163 40 24.5 45 10.2 6 15.0

59.2 ⫾ 25.3 1252 430 34.3 579 46.2 243 19.4 297 70 23.6 78 9.8 12 17.1

and intracytoplasmic sperm injection (ICSI) was performed in 11 patients. ratios. included with total number of obtained oocytes ⬎0.

bPatient-based cOnly patients

dropped after having started Cetrorelix administration on HMG day 6 to as low as 2.9% (95% CL ⫽ 4.9%) according to local laboratory values and 0.9% (95% CL ⫽ 2.3%) according to central laboratory data. HCG was administered in 12 out of 13 cases with elevations of LH above 10 IU/l without rising concentrations of progesterone. Oocyte retrieval and subsequent fertilization were performed as planned in eight of these patients; cumulus–oocyte complexes were obtained in seven of these cases. The fertilization led to embryos of good to excellent quality in six of the eight cases, and to embryos of fair quality in two cases. The treatment cycle of one of these patients led, after replacement of two embryos of excellent quality, to a viable ongoing clinical pregnancy. On HMG day 6, the frequency of patients with follicles of a given size was distributed as follows: 80% of patients had follicles of 11–14 mm, 33% of 15–19 mm, and 3% large follicles (艌20 mm). This turned on the day of HCG injection when 72% of patients had follicles of 11–14 mm, 96% of 15– 19 mm, and 89% had large follicles (艌20 mm). On the day of HCG administration, 10.1 follicles were seen on average, and the mean number of follicles with a diameter 艌20 mm was 2.4. Fertilization rate, quality of embryos and pregnancy rate Among a total of 324 patients with oocyte retrieval, 2971 cumulus–oocyte complexes were obtained. No oocyte was retrieved from two patients. The mean percentage of mature oocytes, as assessed according to microscopic criteria was 63.7% for patients submitted to IVF, while the mean percentage of metaphase II oocytes for ICSI patients was 75.1% of the oocytes retrieved (Staessen et al., 1989; Van Steirteghem et al., 1018

1993). The fertilization rate, defined as the number of fertilized (two pronuclear, 2PN) oocytes per inseminated (IVF) or injected (ICSI) metaphase II oocyte, was nearly the same for both methods of fertilization, which means 60% for IVF and 59% for ICSI per cumulus–oocyte complex. In total, 149 patients were submitted to the IVF procedure, while metaphase II oocytes of 162 patients were the subject of the microinjection method, and 11 patients were submitted to both procedures (Table V). A total of 2971 cumulus–oocyte complexes was retrieved, and these led to 1253 embryos; 34% of these embryos were of excellent quality according to microscopical morphological criteria, 46% were of good quality, and 19% were of fair quality (Staessen et al., 1989). The replacement of a mean of 2.7 embryos per transfer in 299 transfers induced 70 clinical pregnancies, as assessed by transvaginal sonography documenting fetal heart activity. Thus, the clinical pregnancy rate was 24% per transfer. The ongoing clinical implantation rate was 11.4 ⫾ 22.6% when calculated by the number of embryos seen by transvaginal sonography on days 21–24 after embryo transfer divided by the total number of embryos replaced. This ongoing clinical implantation rate may reflect incomplete data, as the number of gestational sacs in cases of early pregnancy loss or ectopic pregnancies remains unknown. Twelve abortions were observed (abortion rate 17%). Adverse drug reaction Injection site reactions were seen in only three patients (0.9%), while one case of hot flushes was reported and attributed to the use of the GnRH antagonist Cetrorelix. None of these events led to premature discontinuation of the study medication.

Phase III study of HMG with Cetrorelix in ovarian stimulation

Severe OHSS (grade III) Only two cases of severe OHSS World Health Organization (WHO) grade III were reported, reflecting an incidence of 0.6% (2/346). Discussion Although the clinical development of early generation GnRH antagonists was hampered by their ability to initiate systemic allergic as well as severe local hypersensitivity reactions due to mast cell degranulation and histamine release, these problems have been completely resolved by the introduction of GnRH antagonists such as Cetrorelix (Hahn et al., 1985; Reissmann et al., 1995; Schally and Comaru-Schally, 1997). On the basis of this extremely important observation, it has been possible to introduce Cetrorelix successfully into protocols for ovarian stimulation (Diedrich et al., 1994; Olivennes et al., 1995; Felberbaum et al., 1996; Albano et al., 1997). Daily midcycle administrations with concomitant HMG stimulation and single dose administration at day 7 of HMG stimulation were each able to reliably prevent the onset of premature LH surges. Subsequent phase II dose-finding studies defined 0.25 mg of Cetrorelix per day as the minimum effective dose for the prevention of premature ovulation induced by premature LH surges, according to the multiple dose protocol (Albano et al., 1996, 1997; Felberbaum et al., 1996). Using only 0.1 mg of Cetrorelix per day according to this administration scheme did not prevent the onset of premature rises of LH (Albano et al., 1997). However, to date the number of treated patients using 0.25 mg of Cetrorelix has been very few, and consequently experience with this new compound is limited. For this reason, a large phase III multicentre trial was initiated. This study evaluated the safety and efficacy of Cetrorelix at its minimum effective dose of 0.25 mg/day according to the multiple-dose protocol, and was the first to do so for a GnRH antagonist in ovarian stimulation. In particular, no such database on daily hormonal measurements during stimulation therapy has been reported to date. Patient compliance was excellent, and no patient had to be excluded due to allergic or hypersensitivity reactions, thus demonstrating that clinically relevant histamine release by this compound was avoided. In total, 333 patients showed satisfactory follicular development leading to administration of HCG for final oocyte maturation. In 324 patients, oocyte retrieval was undertaken. After having started Cetrorelix treatment, the incidence of premature LH rises followed by premature luteinization of the growing follicles was 0.9%. This was within the range to be expected after GnRH agonist administration for assisted reproduction techniques, according to the so-called ‘long’ protocol (Smitz et al., 1992). By using Cetrorelix, follicular distribution at the day of HCG administration reflected a fairly homogeneous follicular development with only few small and intermediate follicles. It has been documented that the presence of several intermediate and small follicles at the day of HCG administration may increase the risk of OHSS (Ron El et al., 1991). A mean of 10.2 follicles on the day of HCG treatment seems to be almost favourable, notably in view of the need for softer ovarian stimulation procedure protocols (Edwards et al., 1996). A

median of 23 ampoules of HMG used per stimulation cycle may indicate the possibility of reducing the amount of gonadotrophins in comparison to the long protocol (MacLachlan et al., 1989). Other authors have reported reduced amounts of gonadotrophins of about 28 ampoules per cycle using recombinant FSH (Out et al., 1996, 1997). The results of a large series is awaited to show whether a combination of GnRH antagonists with recombinant FSH will lead to a further reduction in gonadotrophins to be used for ovarian stimulation. The number and quality of recovered oocytes, the percentage of metaphase II oocytes to be used for ICSI, and fertilization rates after ICSI or IVF must be considered absolutely normal as expected after normal oocyte maturation for assisted reproduction techniques (Ku¨ pker et al., 1995; Ubaldi et al., 1995). A clinical pregnancy rate of 24% per transfer is an acceptable result, and within the estimated limits of an open noncomparative study. These results are even higher than that reported in available European national IVF registers (French IVF Registry, 1995; Deech, 1996; Deutsches IVF-Register, 1997). However, this clinical pregnancy rate of 24% may be influenced by the fact that the population of patients recruited for this study excluded difficult cases such as patients suffering from polycystic ovarian disease, known low responders, or women aged more than 39 years. It is reassuring to observe that, when using Cetrorelix, the percentage of babies born per embryo replaced was 10%. An incidence of 0.6% of severe OHSS (WHO grade III) leading to hospitalization of the patient is low in comparison with the incidence (6.6%) reported after long-protocol agonist treatment (Ron-El et al., 1991). Taking into account all the complications and risks that severe OHSS implies for the patient (such as thrombosis, embolism, putative myocardial infarction and even occasional death), this suggests a major improvement in safety aspects. It is possible that modifications of the stimulation procedures, incorporating softer agents such as clomiphene citrate, may allow this severe, purely iatrogenic disease within assisted reproduction treatment to be abolished (Diedrich and Felberbaum, 1998). As yet, it may be too early to predict an end of the agonist era for ovarian stimulation, and these agents will likely retain their importance in special indications such as endometriosis patients in whom assisted reproduction treatment is envisaged. However, if confirmation is obtained in large comparative studies, there may be clear advantages of antagonist cotreatment with gonadotrophins in ovarian stimulation with regard to the patient’s comfort, and reductions in treatment duration, medication and costs, while achieving the same range of therapeutic outcome. In summary, this study has demonstrated the efficacy and safety of Cetrorelix in ovarian stimulation with HMG for IVF, with a pregnancy rate of 24% per embryo transfer being satisfactory. The incidence of severe OHSS grade III as low as 0.6% indicated that Cetrorelix makes an important contribution to the safety of the treatment. Acknowledgements The authors wish to thank the clinical, scientific, nursing and technical staff of all centres participating in this study. We are especially

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grateful to Dr Hermann, Mr Schu¨ ler and Prof. Engel from ASTAMedica AG for their ongoing support. Mr David John Williams, B.Sc. (Biomed Translations Editorial Services, Heidelberg, Germany) corrected the English.

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