Degarelix

Degarelix (Firmagon®) is a GnRH antagonist mainly used for advanced prostate cancer. It works by rapidly and continuously suppressing LH and FSH, leading to very low testosterone levels. Unlike GnRH agonists, it does not cause an initial hormone flare, making it safer for patients at risk of tumor flare symptoms. Unlike Cetrorelix and Ganirelix, Degarelix is not used in IVF, since its suppression is too prolonged for short-cycle ART needs.

What is Degarelix?

• Degarelix acetate is a synthetic GnRH antagonist.

• Brand name: Firmagon®.

• Unlike Ganirelix or Cetrorelix (used in IVF), Degarelix is primarily used in oncology — specifically, the treatment of advanced hormone-dependent prostate cancer.

• It works by suppressing testosterone production in men.

Mechanism of Action

• Normally, GnRH from the hypothalamus stimulates the pituitary to release LH and FSH, which in men → stimulates the testes to produce testosterone.

• Degarelix binds competitively to GnRH receptors in the pituitary.

• This causes immediate suppression of LH and FSH, leading to a rapid decline in testosterone levels (castration levels within 1–3 days).

Unlike GnRH agonists (e.g., leuprolide, goserelin), Degarelix does not cause an initial “flare” in testosterone. This avoids worsening of symptoms in prostate cancer patients (like bone pain, urinary obstruction, spinal cord compression).

Clinical Uses

• Primary indication:

  • Treatment of advanced hormone-dependent prostate cancer in adult men.

• Off-label/research uses:

  • Endometriosis, uterine fibroids, breast cancer (being studied).

  • Rarely considered in ART/IVF, but not standard due to long suppression.

Formulation & Dosage

• Administered as a subcutaneous injection (usually in the abdominal region).

• Starting dose: 240 mg (two injections of 120 mg).

• Maintenance dose: 80 mg every 28 days.

Benefits

• Immediate testosterone suppression without flare.

• Effective in rapidly reducing PSA levels and controlling prostate cancer symptoms.

• Monthly dosing (after loading dose).

Side Effects

Common (mostly due to low testosterone levels):

• Hot flashes, sweating.

• Weight gain, fatigue.

• Reduced libido, erectile dysfunction.

• Injection site reactions (pain, redness, swelling).

Serious (less common):

• Liver enzyme changes.

• Prolonged QT interval (heart rhythm issues).

• Bone density loss with long-term use.

Contraindications

• Hypersensitivity to Degarelix or formulation components.

• Women (especially in pregnancy and lactation — contraindicated).

• Not indicated for children.

Degarelix isn’t used in IVF, even though it’s a GnRH antagonist like Cetrorelix or Ganirelix, Because:

• Duration of action: Degarelix provides long-term suppression (1 month or more), while IVF protocols only need short-term, reversible suppression (a few days).

• Depth of suppression: Degarelix causes deep suppression of LH/FSH and sex hormones, which would shut down ovarian stimulation completely, making it unsuitable for controlled follicle growth.

• Indication: It’s specifically developed, studied, and approved for advanced prostate cancer, not fertility treatments.

In IVF, we need short, flexible control (Cetrorelix or Ganirelix), not prolonged suppression — that’s why Degarelix isn’t used.