Cetrorelix

Summary

Cetrorelix is a synthetic decapeptide GnRH antagonist approved for use in assisted reproductive technology. It is administered by subcutaneous injection to achieve rapid, dose‑dependent suppression of luteinising hormone (LH) and follicle‑stimulating hormone (FSH), thereby preventing the ovarian hormonal surge that can complicate controlled ovarian stimulation. Beyond IVF, cetrorelix is being investigated for hormone‑dependent conditions such as uterine fibroids and advanced prostate cancer.

Mechanism of Action

Cetrorelix competitively binds the pituitary GnRH‑R, blocking the natural decapeptide GnRH from activating the receptor. This immediate antagonism halts the pulsatile release of LH and FSH, leading to a rapid decline in ovarian steroidogenesis (estrogen, progesterone) and, in men, a fall in testosterone. Because it does not stimulate the receptor before blockade, it avoids the initial hormonal flare seen with GnRH agonists and provides a reversible, dose‑responsive suppression of the gonadal axis.

What the Research Shows

Randomised trials comparing cetrorelix‑based antagonist protocols with the traditional long GnRH‑agonist regimen in IVF cycles show a shorter, simpler treatment course with markedly lower rates of severe ovarian hyperstimulation syndrome (OHSS) and reduced gonadotropin consumption. However, the same trials report modestly lower clinical pregnancy (OR 0.84) and live‑birth rates (OR 0.82) for the antagonist approach. Meta‑analysis of trials in pre‑menopausal women with uterine fibroids indicates that GnRH antagonists, including cetrorelix, significantly improve bleeding control (RR 5.09) and shrink fibroid volume (mean reduction ≈27%). Early phase studies have demonstrated testosterone suppression for >30 h after a single 2 mg subcutaneous dose, supporting investigation in prostate cancer, though definitive efficacy data remain pending. Reviews highlight the broader therapeutic promise of GnRH antagonists for hormone‑dependent malignancies and benign conditions, citing their rapid onset and lower cardiovascular risk relative to agonists.

Reported Benefits

In assisted reproduction, cetrorelix enables a brief stimulation protocol, reduces the need for high‑dose gonadotropins, and cuts the incidence of severe OHSS, improving patient safety and convenience. In uterine fibroids, antagonism of GnRH reduces menstrual blood loss and decreases fibroid size, offering a non‑surgical therapeutic option. The drug’s rapid, reversible action and lack of an initial hormonal flare also make it attractive for conditions where immediate steroid suppression is desired, such as advanced prostate cancer and potentially endometriosis.

Limitations of the Evidence

Evidence from controlled IVF trials indicates that cetrorelix may yield lower pregnancy and live‑birth rates than the long GnRH‑agonist protocol, necessitating careful patient counselling. Data on fibroid treatment are limited to comparisons with placebo; head‑to‑head studies against other hormonal agents are lacking. Clinical investigations for prostate cancer and other malignancies remain in early phases, so efficacy and safety are not yet established. Moreover, cetrorelix is only formally approved for IVF, and its use in other indications is investigational.

Safety Considerations

Cetrorelix is generally well tolerated; the most notable safety advantage is a significant reduction in severe OHSS during IVF cycles. Short‑term hormonal suppression can produce menopausal‑type symptoms (hot flashes, mood changes) and modest bone‑density loss, as observed in fibroid trials. Early pharmacokinetic studies report testosterone suppression lasting over 30 hours after a single dose, indicating potent endocrine effects. No increased cardiovascular risk has been reported in the reviewed literature, but long‑term safety data outside IVF remain limited.

How It Is Administered

The drug is supplied as a subcutaneous injectable acetate formulation. In IVF protocols, it is given either as a multiple‑dose regimen (0.25 mg daily from stimulation day 6–7 until hCG trigger) or as a single 3 mg dose on stimulation day 7–8. Early studies used a single 2 mg dose for testosterone suppression. Formulations have been optimized to improve aqueous solubility and prevent peptide aggregation, including encapsulation techniques.

Routes of Administration

Goals & Uses

• Prevention of premature LH surge during IVFReproductive EndocrinologyHigh
• Prostate cancerOncologyLow
• Controlled ovarian hyperstimulation supportReproductive EndocrinologyHigh
• Prevent premature LH surgeReproductiveHigh
• Uterine fibroidsGynecologyLow
• Endometriosis treatmentGynecologyLow

Contraindications

• Moderate to severe hepatic impairmentHepaticModerate
• Severe renal impairmentOrganHighKidney function concerns
• PregnancyPopulationHighPotential fetal risk or insufficient safety data
• Hypersensitivity to cetrorelix or excipientsAllergicModerate
• BreastfeedingPopulationHighPotential transfer into breast milk or insufficient safety data
• Hypersensitivity to cetrorelix or extrinsic peptide hormonesAllergyHigh

Adverse Effects

• Injection site reactionsLocalCommon
• HeadacheNeurologicUncommonPain in the head or upper neck
• Hot flashesEndocrine / VasomotorUncommon
• NauseaGastrointestinalUncommonFeeling of sickness or urge to vomit
• Allergic/anaphylactic reactionsImmunologicalRare
• Hot flushesVasomotorCommon
• Ovarian hyperstimulation syndrome (OHSS)ReproductiveUncommon

Drug Interactions

• hCG (human chorionic gonadotropin)Moderate
• Gonadotropins (FSH, hMG)Low
• GnRH agonistsHigh
• Other GnRH analoguesModerate

Population Constraints

• Pediatric patientsAgeAbsolute
• Women with known latex allergyAllergyRelative
• MenSexAbsolute
• Patients with renal impairmentOrgan ImpairmentRelative
• ChildrenPediatricAbsolute
• Postmenopausal womenReproductive StatusAbsolute

Regulatory Status

• European UnionApprovedApproved: Assisted reproductive technology protocolsEMA approved
• United StatesApprovedApproved: Controlled ovarian stimulation in IVFFDA approved as Cetrotide
• United KingdomApprovedApproved: IVF ovarian stimulationMHRA approved

Approved in the US, EU, and UK for use in in vitro fertilization protocols; indicated for women undergoing ovarian stimulation.

Evidence & Sources

• Gonadotrophin-releasing hormone antagonists for assisted conception
  Journal ArticleHighAl-Inany HG, Abou-Setta AM, Aboulghar M2006-01-01T00:00:00.000000Z
• LHRH antagonists
  Journal ArticleModerateHaviv F, et al.1998-01-01T00:00:00.000000Z
• GnRH Peptide Antagonist: Comparative Analysis of Chemistry and Formulation with Implications for Clinical Safety and Efficacy
  Journal ArticleModeratePatel S, et al.2024-01-01T00:00:00.000000Z
• The LHRH antagonist cetrorelix: a review
  Journal ArticleModerateReissmann T, et al.2000-01-01T00:00:00.000000Z
• Efficacy of GnRH antagonists in the treatment of uterine fibroids: a meta-analysis
  Journal ArticleHighSánchez Martín MJ, et al.2025-01-01T00:00:00.000000Z
• Novel Approaches to Possible Targeted Therapies and Prophylaxis of Uterine Fibroids
  Journal ArticleModerateKuznetsova MV, et al.2023-01-01T00:00:00.000000Z

Frequently Asked Questions