Degarelix

A synthetic decapeptide GnRH receptor antagonist, FDA approved since 2008 as a monthly subcutaneous depot for advanced prostate cancer, that suppresses LH, FSH, and testosterone within days without the initial testosterone surge produced by GnRH agonists.

Also referenced as: Degarelix acetate, Firmagon, FE200486, FE 200486, Degarelix Accord, Gonax

Also appears in: Other

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What is Degarelix?

Degarelix is a synthetic linear decapeptide amide, a 10-amino-acid analog of gonadotropin-releasing hormone (GnRH) in which seven residues are unnatural amino acids, five of them D-configured. Developed by Ferring under the code FE200486 and marketed as Firmagon, it was approved by the FDA on December 24, 2008 for the treatment of advanced prostate cancer, and in the European Union on February 17, 2009. It belongs to the third generation of GnRH antagonists, molecules engineered for long duration of action and low histamine release after the first-generation antagonists proved too allergenic for clinical use.

Degarelix is a prostate-cancer drug, not a performance or wellness compound, and it has almost no footprint in the research-peptide market. It appears here because it completes the GnRH family alongside the agonists (leuprolide, triptorelin, goserelin) and the fertility-clinic antagonists (cetrorelix, ganirelix), and because the difference between an agonist and an antagonist at the same receptor is a recurring point of confusion in discussions of hormone-axis peptides.

How it works

Degarelix acts at the pituitary GnRH receptor, where it blocks rather than stimulates. The functional consequence is immediate suppression of the gonadal axis without the transient stimulation that defines agonist therapy:

• Competitive, reversible GnRH receptor antagonism — degarelix binds pituitary GnRH receptors and blocks the endogenous pulse, cutting release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) and therefore testicular testosterone production. Because no receptor activation occurs, there is no initial LH and testosterone surge; the approved label describes this directly, and castrate testosterone (≤50 ng/dL) was reached by day 3 in 96% of CS21 patients on the approved degarelix regimen versus 0% on leuprolide (Klotz et al., BJU International, 2008, 102(11):1531–1538)
• A self-forming subcutaneous depot — degarelix precipitates into a gel depot at the injection site, from which it is released over weeks. In the original preclinical characterization, a single 2 mg/kg subcutaneous dose suppressed LH and testosterone for more than 40 days in intact and castrated rats and in ovariectomized rhesus monkeys, outlasting abarelix, ganirelix, cetrorelix, and azaline B in the same models (Broqua et al., Journal of Pharmacology and Experimental Therapeutics, 2002, 301(1):95–102)
• Low histamine-releasing activity — the same preclinical work showed only weak histamine release in vitro, unlike cetrorelix and in line with ganirelix and abarelix; this property is what allowed a long-acting antagonist to be given at depot doses. It also separates degarelix in practice from abarelix, an earlier antagonist whose U.S. product (Plenaxis) was approved in 2003 under a restricted program because of immediate-onset systemic allergic reactions and was withdrawn from the U.S. market within a few years (Broqua et al., Journal of Pharmacology and Experimental Therapeutics, 2002)
• FSH suppression beyond that of agonists — in CS21 and its extension, FSH was rapidly suppressed and stayed suppressed on degarelix, and it fell further when patients crossed from leuprolide to degarelix, consistent with antagonist blockade of a pathway that agonist desensitization suppresses only partially (Crawford et al., Journal of Urology, 2011, 186(3):889–897)

Research status

Degarelix has a completed pivotal program, an approval that has stood for 17 years, and one large safety trial that ended without an answer.

CS21 (NCT00295750). The pivotal open-label Phase 3 trial enrolled 620 men with prostate cancer, 610 of whom were randomized and treated with degarelix 240 mg loading followed by 80 mg or 160 mg every 28 days, or with leuprolide 7.5 mg intramuscularly monthly, for 12 months. The primary endpoint was the cumulative probability of maintaining testosterone at or below 0.5 ng/mL from day 28 to day 364: 97.2% for degarelix 240/80 mg, 98.3% for 240/160 mg, and 96.4% for leuprolide, meeting the noninferiority criterion. Degarelix lowered testosterone and PSA faster, with no testosterone surge and no need for antiandrogen flare protection; injection-site reactions were far more common with the subcutaneous antagonist than with the intramuscular agonist (40% versus under 1%), and there were no systemic allergic reactions (Klotz et al., BJU International, 2008, 102(11):1531–1538). The 240/80 mg regimen became the approved dose; the 160 mg maintenance arm was not taken forward. A protocolled secondary analysis reported a lower risk of PSA progression or death on degarelix 240/80 mg than on leuprolide (P = 0.05), with recurrences occurring almost exclusively in men with metastatic disease or baseline PSA above 20 ng/mL; the authors framed it as hypothesis-generating rather than a demonstration of survival benefit (Tombal et al., European Urology, 2010, 57(5):836–842).

CS21A extension. Patients completing CS21 continued on degarelix or were re-randomized from leuprolide to degarelix in a one-arm crossover extension with a median follow-up of 27.5 months. Testosterone and PSA suppression were maintained, and the PSA progression-free survival hazard rate in the crossover group fell significantly after the switch, while the rate in men who stayed on degarelix matched their first year (Crawford et al., Journal of Urology, 2011, 186(3):889–897). An extension with a single-arm crossover cannot distinguish a drug effect from regression to the mean or selection of patients who tolerated the first year, so the result supports rather than proves the year-one PSA finding.

Pooled comparative analyses. A pooled analysis of individual patient data from five randomized Phase 3 and 3b trials (1,925 men; degarelix versus leuprolide or goserelin) reported better PSA progression-free survival on degarelix (hazard ratio 0.71), a higher overall survival estimate (hazard ratio 0.47), and fewer joint, musculoskeletal, and urinary-tract adverse events (Klotz et al., European Urology, 2014, 66(6):1101–1108). A separate pooled analysis of six trials (2,328 men) found that among men with pre-existing cardiovascular disease, the risk of a cardiac event in the first year was less than half as high on the antagonist as on agonists (hazard ratio 0.44, 95% CI 0.26–0.74), with the authors stating plainly that a post hoc analysis can only generate a hypothesis (Albertsen et al., European Urology, 2014, 65(3):565–573). These trials were designed to show testosterone noninferiority, not survival or cardiovascular outcomes, and the cardiac signal is the hypothesis that PRONOUNCE was built to test.

PRONOUNCE (NCT02663908) — the question remains open. PRONOUNCE was the first international randomized trial to compare the cardiovascular safety of a GnRH antagonist with a GnRH agonist in men with prostate cancer and established atherosclerotic cardiovascular disease. It randomized 545 men 1:1 to degarelix or leuprolide for 12 months, with adjudicated major adverse cardiovascular events (MACE: death, myocardial infarction, or stroke) as the primary endpoint. MACE occurred in 15 (5.5%) patients on degarelix and 11 (4.1%) on leuprolide (hazard ratio 1.28, 95% CI 0.59–2.79; P = 0.53). The trial was planned for 900 patients and was stopped early because of slow recruitment and a lower-than-expected event rate; the registry entry states the sponsor’s decision was not based on safety concerns or knowledge of the results. The authors’ conclusion was that the relative cardiovascular safety of antagonists versus agonists remains unresolved (Lopes et al., Circulation, 2021, 144(16):1295–1307). This is the key counterweight to the pooled retrospective analyses above: the one prospective trial designed to confirm a cardiovascular advantage did not find one, and it was underpowered to exclude one.

Three-month formulation. A three-monthly maintenance regimen was developed by Astellas in Japan. A Phase 2 study randomized 155 Japanese patients to 360 mg or 480 mg every 84 days after a 240 mg loading dose; the 480 mg arm reached a 97.2% cumulative castration rate and was chosen for Phase 3, with injection-site reactions the most frequent adverse event but no discontinuations because of them (Ozono et al., Japanese Journal of Clinical Oncology, 2017, 47(5):438–446). The Phase 3 trial then showed noninferiority of 480 mg degarelix every 84 days to 10.8 mg goserelin in 234 men (cumulative castration 95.1% versus 100%), with faster testosterone, LH, FSH, and PSA declines on degarelix (Ozono et al., Cancer Science, 2018, 109(6):1920–1929). Japan approved the 480 mg per 12 weeks regimen in January 2019 and Astellas launched it in June 2019 as an additional dosage of Gonax, the Japanese brand. Three-month regimens were also studied earlier in Ferring-sponsored trials registered as NCT00468286 (CS18) and NCT00268892 (CS15A). The three-month depot is not an FDA-approved product; the only U.S. presentation remains the one-month regimen.

Regulatory record as of October 2026. FDA approval under NDA 022201 on December 24, 2008 (new molecular entity). The U.S. prescribing information was last revised in February 2020 (labeling supplement 16, adding an embryo-fetal toxicity warning), with a DailyMed republication on January 30, 2024. In the European Union, Firmagon has been authorized since February 17, 2009, and its label is broader than the U.S. one: advanced hormone-dependent prostate cancer, high-risk localized or locally advanced disease in combination with radiotherapy, and neoadjuvant use before radiotherapy. A generic (Degarelix Accord) was authorized in the EU on September 29, 2023. In the United States, an abbreviated application for degarelix acetate 80 mg and 120 mg from Chia Tai Tianqing (ANDA 215791) received tentative approval on August 18, 2025, meaning it met FDA standards but could not yet be marketed because of remaining patent or exclusivity protection; no fully approved U.S. generic was on record as of October 2026. No new indication, formulation, or safety-labeling change was approved in the U.S. in 2025 or 2026.

Active work. Degarelix continues to appear on ClinicalTrials.gov mainly as the androgen-deprivation backbone in prostate-cancer trials of other agents, including the EORTC Phase 3b trial of radiotherapy with long-term GnRH antagonist versus agonist plus flare protection in very-high-risk localized or locally advanced disease (NCT02799706, active, not recruiting) and several Phase 2 neoadjuvant and intermittent-therapy studies. Outside prostate cancer, it has been tested in premenopausal women as neoadjuvant ovarian suppression alongside letrozole in endocrine-responsive breast cancer (the TREND trial, degarelix versus triptorelin) and in a small proof-of-concept study of single luteal-phase dosing in controlled ovarian stimulation. There is no registered human program outside oncology and reproductive endocrinology.

Common dosage forms

• Firmagon kit, 120 mg vials (two per starting kit) — lyophilized degarelix acetate powder for subcutaneous use.
• Firmagon kit, 80 mg vial (maintenance kit) — lyophilized degarelix acetate powder for subcutaneous use.
• 480 mg three-month presentation (Gonax, Japan) — approved in January 2019 and marketed since June 2019 as a 480 mg three-month maintenance presentation; not an FDA-approved format.
• Generic degarelix for injection — authorized in the European Union (Degarelix Accord, 2023) in the same vial strengths; U.S. generics held only tentative approval as of October 2026.
• Research supply — degarelix acetate is available as a lyophilized reference compound from chemical suppliers for laboratory pharmacology, but it is rarely listed by research-peptide vendors, which is consistent with a molecule whose only pharmacology is chemical castration.

Key considerations

• The U.S. approval is for advanced prostate cancer, and nothing else. Degarelix’s FDA Approved status reflects that an approved drug product containing the molecule exists. Its sole U.S. labeled indication is advanced prostate cancer (the EU label adds high-risk localized and locally advanced disease treated with radiotherapy); its effect in any user is profound suppression of testosterone (or, in women, ovarian hormones), with the labeled consequences of androgen deprivation: hot flashes, weight gain, loss of bone mineral density, fatigue, sexual dysfunction, and metabolic changes. There is no framing under which it is a hormone-optimization or performance compound.
• Antagonist, not agonist — the flare distinction matters. GnRH agonists such as leuprolide, triptorelin, and goserelin first stimulate the receptor, producing a testosterone surge of one to two weeks before desensitization drives it down, which is why agonists are often started with an antiandrogen. Degarelix blocks the receptor immediately, with castrate testosterone in 96% of patients by day 3 and no surge. Descriptions grouping degarelix with “LHRH agonists” or calling it a “long-acting Lupron” are wrong about its mechanism.
• Degarelix is not relugolix. Relugolix (Orgovyx, FDA approved December 2020) is a small-molecule, non-peptide, once-daily oral GnRH receptor antagonist; in the HERO trial it sustained castrate testosterone in 96.7% of men versus 88.8% on leuprolide and showed faster testosterone recovery after discontinuation (Shore et al., New England Journal of Medicine, 2020, 382(23):2187–2196). Degarelix is a peptide given as a monthly subcutaneous depot. The two share a receptor and a class but differ in chemistry, route, half-life, and reversibility.
• The cardiovascular advantage is a hypothesis, not a finding. Retrospective pooled analyses suggested fewer cardiac events on degarelix than on agonists in men with existing cardiovascular disease. PRONOUNCE, the trial designed to test that prospectively, was stopped early and found no significant difference (5.5% versus 4.1% MACE, HR 1.28). The label carries the class warning that androgen deprivation may prolong the QT interval, and hypersensitivity reactions including anaphylaxis, urticaria, and angioedema have been reported post-marketing. A prior severe hypersensitivity reaction is a labeled contraindication.
• Injection-site reactions are the dominant tolerability issue. The depot that makes monthly dosing possible is also the source of the most common adverse reactions: injection-site pain (28%), erythema (17%), swelling (6%), induration (4%), and nodules (3%) in the pivotal trial, mostly transient and mild to moderate but materially more frequent than with intramuscular agonist depots. In the Japanese three-month trials, injection-site reactions were likewise the most common adverse event.