Degarelix
An approved injectable that shuts down testosterone within days for advanced prostate cancer, without the initial surge GnRH agonists cause; its injection-site reactions and the unsettled question of heart safety are the trade-offs.
Degarelix (Firmagon) blocks the pituitary's receptor for gonadotropin-releasing hormone, so LH, FSH and testosterone fall at once. In its pivotal trial testosterone reached castrate levels by day 3 in 96% of men, against none on leuprolide. It is a medicine for prostate cancer, not a performance or wellness peptide.
What is it?
Most prostate cancers need testosterone to grow, so lowering it, androgen-deprivation therapy, is standard for advanced disease. For decades that meant GnRH agonists such as leuprolide, which overstimulate the pituitary until it stops responding. Their drawback is the start: testosterone first surges for a week or two, which can worsen bone pain or urinary blockage, so men often need extra anti-androgen tablets to cover the flare. GnRH antagonists block the receptor instead, so hormones fall immediately. Earlier antagonists released histamine and were hard to formulate; degarelix, with several unnatural amino acids, avoided that and forms a slow-release depot under the skin.
The pivotal phase 3 trial, CS21, compared degarelix with monthly leuprolide in 610 men for a year. Both kept testosterone at castrate levels in about 97% of men from day 28, so degarelix was not inferior, but it got there far faster: by day 3, 96% on degarelix against none on leuprolide, with a quicker fall in PSA and no flare. An extension followed men for a median of 27.5 months and found men switched from leuprolide to degarelix kept their suppression. On that evidence FDA approved it as Firmagon in December 2008, and it was later approved in the EU and in Japan.
Two questions followed it. The first is the injection: degarelix is a large subcutaneous injection, and injection-site reactions occurred in about 40% of men in the trials against under 1% with intramuscular leuprolide, mostly pain, redness and swelling that ease over time. The second is the heart. Pooled trial data and later meta-analyses suggested fewer cardiovascular events than with agonists in men with existing heart disease, but the one prospective randomised test, PRONOUNCE, stopped early with too few events and found no difference at one year, so the question remains open.
Newer uses test it before prostate surgery, alone or with anti-androgen drugs, and an oral GnRH antagonist, relugolix, now competes with it; a network meta-analysis found similar efficacy without injection reactions, and men stayed on relugolix longer in insurance-claims data. Degarelix is a prescription medicine given by clinicians, not something sold or used outside prostate cancer care.
Mechanism of Action
Degarelix competes with the body's GnRH at the pituitary receptor. With the receptor blocked, LH and FSH fall within hours, and testosterone follows, with no initial stimulation phase.
Blocks the GnRH receptor
As an antagonist it prevents the receptor from signalling at all, unlike agonists, which first stimulate it and only later exhaust it.
LH, FSH and testosterone fall at once
In CS21, testosterone was at castrate levels by day 3 in 96% of men on degarelix and in none on leuprolide, and PSA fell faster over the first 14 to 28 days.
A slow-release depot
Injected under the skin, degarelix forms a gel depot that releases it over weeks, which allows monthly maintenance doses after a 240 mg loading dose.
FSH and the heart
Degarelix lowers FSH more completely than agonists, one proposed reason for fewer cardiovascular events in men with heart disease; the prospective trial meant to settle this did not.
Published Research
Our evidence set holds 38 papers that name degarelix. Twenty name it in their titles and have an abstract; 16 are carded below: 7 studies in people and 9 reviews, appraisals, practice notes or meta-analyses, including the pivotal trial, its extension, the cardiovascular safety trial and the NICE and Cochrane appraisals. Degarelix is an approved drug, so this evidence is far deeper than for the research peptides on this site.
CS21: pivotal phase 3 vs leuprolide, 610 men
Men with prostate cancer of any stage received degarelix 240 mg then 80 or 160 mg monthly, or leuprolide 7.5 mg monthly, for a year. Testosterone stayed at or below 0.5 ng/mL from day 28 to day 364 in 97.2%, 98.3% and 96.4%. By day 3, 96.1% and 95.5% on degarelix were castrate against none on leuprolide, and degarelix needed no anti-androgen cover for flare.
Why antagonists took so long
Lowering testosterone surgically or with a GnRH agonist is the standard of care for metastatic prostate cancer. The review explains that GnRH antagonists were long held back by histamine-releasing activity and formulation problems, and presents degarelix as a new antagonist that overcame them.
Therapeutic potential review
Across two phase 2 dose-finding trials and the phase 3 trial, 240 mg followed by 80 or 160 mg monthly kept testosterone at or below 0.5 ng/mL, and degarelix was non-inferior to leuprolide. Injection-site reactions (40% vs under 1%) and chills (4% vs 0%) were commoner with degarelix, and it was then available only as a monthly depot.
Switching from leuprolide
134 men who had completed a year of monthly leuprolide were switched to degarelix 240 mg then monthly maintenance. Testosterone and PSA suppression were sustained over the first three months, and 4% stopped for treatment-related events, mostly injection-site pain.
Extension to a median 27.5 months
Men continued degarelix or crossed over from leuprolide in an extension of the pivotal trial. Suppression continued, adverse event rates were similar between groups and fell over time, and the data supported the PSA progression-free survival advantage for degarelix seen in year one.
Cardiovascular events in 9 pooled trials
Across 1,704 men treated for an average of 22 months, cardiovascular event rates were similar before and after starting degarelix. Events were concentrated in men with pre-existing cardiovascular disease and shaped by age and modifiable risk factors; the authors called for randomised trials against agonists.
Liver safety (LiverTox)
Degarelix is associated with serum liver-enzyme elevations during therapy but has not been linked to clinically apparent acute liver injury.
Review of its use in prostate cancer
Approved as Firmagon in the US and EU and as Gonax in Japan. In the pivotal trial degarelix 240 mg then 80 mg monthly was non-inferior to leuprolide; adverse events were mostly mild to moderate, with injection-site reactions and effects of testosterone suppression such as hot flushes and weight gain the commonest.
Pharmacokinetics and pharmacodynamics
A review of how degarelix avoids the agonists' testosterone surge, suppresses FSH more completely and reaches castrate testosterone more reliably. It discusses the post hoc finding of fewer cardiovascular events in men with pre-existing heart disease, which the author considered real but needing prospective confirmation.
Making the injection easier
Subcutaneous degarelix causes more injection-site reactions than intramuscular agonists. Clinicians and nurses described the techniques and strategies they developed to reduce the discomfort of the injection.
NICE appraisal
The independent Evidence Review Group found the manufacturer's evidence insufficient to estimate cost-effectiveness. NICE recommended degarelix for advanced hormone-dependent prostate cancer only in men with spinal metastases, and only at a discounted price.
PRONOUNCE: cardiovascular safety trial
545 men with prostate cancer and atherosclerotic cardiovascular disease were randomised to degarelix or leuprolide for 12 months; enrolment stopped early, short of the planned 900, because of slow recruitment and few events. Major adverse cardiovascular events occurred in 5.5% on degarelix and 4.1% on leuprolide (hazard ratio 1.28, P = 0.53), so relative cardiovascular safety remains unresolved.
Cochrane review
Compared with standard androgen suppression for advanced hormone-sensitive prostate cancer, the evidence on survival and progression was uncertain, and degarelix likely increases injection-site pain. Follow-up in the included trials was at most 14 months, and the reviewers called for better long-term studies.
ARNEO: before prostatectomy
In a randomised phase 2 trial in high-risk prostate cancer, three months of degarelix plus apalutamide before radical prostatectomy produced significantly more minimal residual disease at surgery than degarelix plus placebo. Whether that improves long-term outcomes is not yet known.
Staying on treatment in practice
In US insurance-claims data from 2017 to 2022, men stayed on oral relugolix for a median of 13.5 months, on GnRH agonists for 8.8 months and on injectable degarelix for 3.1 months, with the differences most marked in metastatic disease.
Cardiovascular meta-analysis
Pooling comparative studies, degarelix was associated with fewer major adverse cardiovascular events than GnRH agonists, while some individual outcomes did not differ significantly. The authors called for further studies to confirm a safety advantage.
Dosing Data
Degarelix is dosed by label. The approved regimen is a 240 mg loading dose given as two 120 mg subcutaneous injections, then 80 mg once a month under the skin of the abdomen, with testosterone and PSA monitored during treatment.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
From the trials and reviews above and the label.
Contraindications & Cautions
From the prescribing information and the trials; a clinician decides.
Legal Status
Degarelix is an approved prescription medicine.
Frequently Asked Questions
?How is degarelix different from leuprolide?
Leuprolide is a GnRH agonist: it first raises testosterone before suppressing it. Degarelix is an antagonist: it blocks the receptor, so testosterone falls within days with no flare. In the pivotal trial 96% on degarelix were castrate by day 3 against none on leuprolide; by a month both worked equally well.
?Is degarelix safer for the heart?
Unclear. Pooled trial data and meta-analyses suggested fewer cardiovascular events than with agonists in men with heart disease, but the prospective PRONOUNCE trial stopped early with too few events and found no significant difference (5.5% vs 4.1% at one year).
?Why does the injection hurt?
Degarelix is a large subcutaneous dose that forms a depot under the skin; injection-site reactions affected about 40% of men in trials. Clinicians use techniques to reduce the discomfort, and reactions tend to lessen after the first dose.
?What is the dose?
By label, 240 mg as two 120 mg injections to start, then 80 mg every month under the skin of the abdomen, given by a clinician.
?Is there an oral alternative?
Yes. Relugolix is an oral GnRH antagonist; a network meta-analysis found efficacy comparable to degarelix without injection-site reactions, and in claims data men stayed on it longer.
?Why is degarelix on a peptide site?
It is a synthetic peptide drug, and it appears alongside other GnRH peptides such as gonadorelin and leuprolide. It has no role outside prostate cancer treatment.
References
- [fda-pi] Firmagon (degarelix) Prescribing Information. Ferring Pharmaceuticals.
- [Human] Klotz L, et al. "The efficacy and safety of degarelix: a 12-month, comparative, randomized, open-label, parallel-group phase III study in patients with prostate cancer." BJU Int, 2008;102(11):1531-8. PMID: 19035858.
- [Review] Doehn C, et al. "Degarelix for prostate cancer." Expert Opin Investig Drugs, 2009;18(6):851-60. PMID: 19453267.
- [Review] Doehn C, et al. "Degarelix and its therapeutic potential in the treatment of prostate cancer." Clin Interv Aging, 2009;4:215-23. PMID: 19503784.
- [Human] de la Rosette J, et al. "Efficacy and safety of androgen deprivation therapy after switching from monthly leuprolide to monthly degarelix in patients with prostate cancer." Int J Clin Pract, 2011;65(5):559-66. PMID: 21342376.
- [Human] Crawford ED, et al. "A phase III extension trial with a 1-arm crossover from leuprolide to degarelix: comparison of gonadotropin-releasing hormone agonist and antagonist effect on prostate cancer." J Urol, 2011;186(3):889-97. PMID: 21788033.
- [Human] Smith MR, et al. "Gonadotropin-releasing hormone blockers and cardiovascular disease risk: analysis of prospective clinical trials of degarelix." J Urol, 2011;186(5):1835-42. PMID: 21944083.
- [Review] "Degarelix." , 2012. PMID: 31643893.
- [Review] Carter NJ, et al. "Degarelix: a review of its use in patients with prostate cancer." Drugs, 2014;74(6):699-712. PMID: 24756432.
- [Review] Klotz L. "Pharmacokinetic and pharmacodynamic profile of degarelix for prostate cancer." Expert Opin Drug Metab Toxicol, 2015;11(11):1795-802. PMID: 26513436.
- [Review] Barkin J, et al. "Optimizing subcutaneous injection of the gonadotropin-releasing hormone receptor antagonist degarelix." Can J Urol, 2016;23(1):8179-83. PMID: 26892063.
- [Review] Uttley L, et al. "Degarelix for Treating Advanced Hormone-Dependent Prostate Cancer: An Evidence Review Group Perspective of a NICE Single Technology Appraisal." Pharmacoeconomics, 2017;35(7):717-726. PMID: 27943135.
- [Human] Lopes RD, et al. "Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Prostate Cancer: The Primary Results of the PRONOUNCE Randomized Trial." Circulation, 2021;144(16):1295-1307. PMID: 34459214.
- [Review] Zengerling F, et al. "Degarelix for treating advanced hormone-sensitive prostate cancer." Cochrane Database Syst Rev, 2021;8(8):CD012548. PMID: 34350976.
- [Human] Devos G, et al. "ARNEO: A Randomized Phase II Trial of Neoadjuvant Degarelix with or Without Apalutamide Prior to Radical Prostatectomy for High-risk Prostate Cancer." Eur Urol, 2023;83(6):508-518. PMID: 36167599.
- [Human] Hafron J, et al. "Study of persistence and adherence to ADT in prostate cancer: relugolix, degarelix, and GnRH agonists in the US." Future Oncol, 2025;21(10):1219-1230. PMID: 40189880.
- [Review] Odat RM, et al. "Risk of cardiovascular disease following degarelix versus gonadotropin-releasing hormone agonists in patients with prostate cancer: a systematic review and meta-analysis." Urol Oncol, 2025;43(6):359-369. PMID: 39818461.
Sources & Citations
Every citation on this page is PubMed-indexed and has been checked against its record, apart from the Firmagon prescribing information. Grey Peptides sells nothing and links to no vendor.
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