Firmagon
Evidence Grade A — Regulatory approved. 369 published studies. 84 registered clinical trials.
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Degarelix (sold as Firmagon) is a monthly injection for advanced prostate cancer that suppresses testosterone — the hormone that fuels prostate cancer growth. Unlike older hormone treatments that cause a temporary surge in testosterone before shutting it down, degarelix blocks hormone signals immediately. This matters most for patients with symptoms like bone pain, where a hormone surge could make things worse.
369 published studies: 242 human, 28 animal, 17 in-vitro, 73 reviews
Degarelix is marketed as Firmagon (approved December 2008) for advanced prostate cancer. It is administered as a monthly subcutaneous injection, with a loading dose of 240 mg followed by 80 mg monthly. Injection-site reactions are common (pain in 35%, redness in 32%).
The key clinical advantage of degarelix over traditional GnRH agonists is the absence of testosterone flare, making it particularly suitable for patients with symptomatic metastatic disease where a hormone surge could worsen bone pain or urinary obstruction. It achieves castrate testosterone levels within three days. However, monthly injections with notable injection-site discomfort have limited its uptake compared to longer-acting GnRH agonist depots, and the oral GnRH antagonist relugolix has emerged as a more convenient alternative with potential cardiovascular advantages.
Unlike GnRH agonists (such as leuprolide and goserelin) which overstimulate and then exhaust the hormone system, degarelix directly blocks the GnRH receptor in the pituitary gland, preventing hormone signals from getting through at all. This means testosterone levels drop immediately — within days rather than weeks — and critically, there is no initial hormone surge or 'flare' effect. This distinction matters clinically because the flare can temporarily worsen prostate cancer symptoms and requires additional medication to manage.
Degarelix achieves castrate testosterone levels within three days, avoiding the one-to-two-week hormone surge ("flare") seen with older GnRH agonist treatments. The CS21 trial showed faster initial disease marker suppression compared to the agonist leuprolide. For patients at risk of flare-related complications — such as spinal cord compression or urinary obstruction from tumour swelling — this immediate suppression is a meaningful clinical advantage. However, degarelix requires monthly injections that frequently cause injection-site pain (35%) and redness (32%), which has limited its uptake compared to longer-acting alternatives. The oral GnRH antagonist relugolix (Orgovyx) has further reduced degarelix's niche by offering the same flare-free suppression in a daily tablet with potential cardiovascular advantages, as demonstrated in the HERO trial.
Open-Label, Randomised Parallel-Group Study
A Study of BMS986365 in Combination With Degarelix in People With Prostate Cancer
Study of Radiation Therapy in Combination With Darolutamide + Degarelix in Intermediate Risk Prostate Cancer
Cardiometabolic Consequences of the Loss of Ovarian Function
NeoAdjuvant Theranostic Lutetium Study: The Nautilus Trial
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Histrelin is available as Supprelin LA for central precocious puberty (approved 2007). The Vantas implant for prostate cancer was approved in 2004 but discontinued in 2021. The implant requires a minor surgical procedure for insertion and removal/replacement each year. Supprelin LA's main clinical advantage is its 12-month duration — the longest of any GnRH agonist — which is particularly valuable in paediatric patients where treatment compliance over years is important. Clinical studies demonstrated effective suppression of puberty markers in over 97% of patients. The implant has also seen significant off-label use in gender-affirming care as a puberty blocker, where its annual dosing schedule offers practical benefits for adolescent patients and their families.
Goserelin is marketed as Zoladex by AstraZeneca, available as 3.6 mg monthly and 10.8 mg three-monthly subcutaneous implants. First approved in 1989, it is used in advanced prostate cancer, premenopausal breast cancer, endometriosis, and for thinning the uterine lining before surgical procedures. Goserelin achieves castrate-level testosterone suppression (below 50 ng/dL) within two to four weeks. Its unique implant delivery system means there is no liquid injection, reconstitution, or refrigeration required — a practical advantage in some clinical settings. Like all GnRH agonists, it causes an initial hormone flare before suppression takes effect. Goserelin holds an important niche in breast cancer treatment, where it is used to suppress ovarian function in premenopausal women with hormone-receptor-positive disease, often in combination with aromatase inhibitors.
Nafarelin is marketed as Synarel (approved 1990) for endometriosis and central precocious puberty. It requires administration as one spray in each nostril twice daily — a higher frequency than injectable alternatives but avoids needles entirely, which can be a significant advantage for some patients, particularly children. Clinical trials showed symptom improvement in 75–92% of endometriosis patients. However, absorption can be affected by nasal congestion or concurrent use of nasal decongestants, which can be a practical limitation. As with all GnRH agonists, prolonged use leads to bone density loss, and treatment for endometriosis is typically limited to six months. Nafarelin occupies a niche for patients who prefer non-injectable hormone suppression, though it has become less commonly prescribed as longer-acting depot injections and oral alternatives have become available.
