Degarelix
Degarelix (Firmagon), GnRH receptor antagonist
Written by Aaron CuhaReviewed Sep 2026
Also known as: Firmagon, FE200486
A GnRH antagonist approved in 2008 for advanced prostate cancer. In its 610-patient phase 3, testosterone was at or below 0.5 ng/mL by day 3 in about 96 percent of degarelix patients and in none of the leuprolide patients, and it met non-inferiority over 12 months. Injection site reactions occurred in 40 percent versus under 1 percent with intramuscular leuprolide, and the trial designed to test whether it is safer for the heart was terminated early and found no difference.
Overview
Degarelix is a synthetic decapeptide containing five D-amino acids that blocks the GnRH receptor directly instead of overstimulating it. The FDA approved it on 24 December 2008 under NDA 022201 for treatment of patients with advanced prostate cancer. That single short indication is the whole approved use.
The clinical argument for the antagonist class is speed and the absence of a flare. Because the receptor is blocked rather than desensitised, luteinising hormone and testosterone fall immediately. In the pivotal trial, by day 3, testosterone was at or below the castrate threshold of 0.5 ng/mL in 96.1 and 95.5 percent of patients in the two degarelix arms and in none of the patients on leuprolide. No antiandrogen cover is needed.
That advantage comes with two costs that are easy to find in the data and easy to leave out of a summary. The first is tolerability at the injection site: 40 percent of subcutaneous degarelix patients had injection site reactions, against under 1 percent with intramuscular leuprolide, which is a real adherence problem for a drug given monthly and indefinitely. The second is that the promised cardiovascular advantage has not been demonstrated. PRONOUNCE was designed to test exactly that, in men with prostate cancer and established atherosclerotic cardiovascular disease. It was terminated after randomising 545 of a planned 900 patients, and it found 15 major adverse cardiovascular events on degarelix versus 11 on leuprolide, hazard ratio 1.28, P equal to 0.53.
The correct reading of PRONOUNCE is the one its own authors give: the relative cardiovascular safety of GnRH antagonists and agonists remains unresolved. The trial did not show degarelix is worse, and it did not show it is better. It was stopped before it could show anything.
Mechanism of action
Direct competitive antagonism at the pituitary GnRH receptor. Blocking the receptor stops luteinising hormone and follicle-stimulating hormone release immediately, so testosterone falls within days with no initial surge. This is the mechanistic opposite of the agonists leuprolide, goserelin and triptorelin, which produce their suppression by first overstimulating the same receptor. Degarelix also forms a subcutaneous depot at the injection site from which it releases slowly, which explains both the long terminal half-life and the high rate of local reactions.
Human evidence
One large randomised phase 3 establishing non-inferior testosterone suppression against leuprolide with faster onset and no flare, and one terminated randomised cardiovascular outcomes trial that found no difference in major adverse cardiac events.
- Phase 3, 610 patients, 12 months: castrate testosterone maintained in 97.2 and 98.3 percent on degarelix versus 96.4 percent on leuprolide. Non-inferiority met.
- Day 3 castrate testosterone: about 96 percent on degarelix, zero percent on leuprolide. This is the class difference in one number.
- Injection site reactions 40 percent versus under 1 percent. Urinary tract infection 3 versus 9 percent, arthralgia 4 versus 9 percent, chills 4 versus 0 percent.
- PRONOUNCE, 545 randomised of 900 planned, terminated: hazard ratio for major adverse cardiovascular events 1.28 (95 percent CI 0.59 to 2.79), P equal to 0.53.
- Label adverse reactions at 10 percent or more: injection site reactions, hot flushes, and rises in transaminases and gamma-glutamyltransferase.
What this does not tell you: The primary endpoint of the pivotal trial is testosterone, a surrogate. No trial has shown that degarelix produces longer survival, fewer fractures, or fewer cardiac events than a GnRH agonist. The pivotal trial was open-label, which matters for subjectively reported adverse events. PRONOUNCE was underpowered by design failure rather than by intent and cannot be read as a negative result. The 53-day terminal half-life means that if a patient does not tolerate it, the exposure persists for weeks after the last dose.
Reading the research record
PRONOUNCE is the most instructive thing on this page and it is almost always described wrongly.
The hypothesis was reasonable: observational data and a meta-analysis had suggested GnRH antagonists might carry less cardiovascular risk than agonists, so a trial enrolled men who already had atherosclerotic cardiovascular disease, the population in whom a difference should be easiest to see. It needed 900 patients. It randomised 545 and was terminated, because enrolment was slower than projected and events were fewer than projected.
With 26 events in total, the confidence interval around the hazard ratio runs from 0.59 to 2.79. That interval contains a large benefit and a large harm. Citing this trial as evidence that degarelix has no cardiovascular advantage treats an absence of data as a finding.
Testosterone suppression is a surrogate endpoint. It is the thing these drugs were licensed on, and it is reliably achieved, but no randomised trial has shown that any one gonadotrophin-releasing hormone drug produces longer survival than another. The modern trials that include triptorelin or degarelix mostly use them as the background androgen deprivation while testing something else, such as when to give radiotherapy or whether to add chemotherapy. Those trials tell you about the added intervention. They do not rank the hormone drugs against each other.
The evidence, charted
Fig. 1 · evidence composition
3of 3 citations (100%) are in people
Every citation cited here is Human work; no other study type is cited on this page. This count is of our own citation list and understates any literature larger than the sources we cite.
Fig. 2 · evidence over time
Citations here span just two years, 2008 and 2021.
Too few distinct publication years on this page to plot as a timeline.
Fig. 3 · legal status at a glance
US
Approved
UK
Approved
AU
Approved
CA
Approved
Approved in all four jurisdictions shown. A jurisdiction's classification is a regulatory fact, not a verdict on the science; see Legal status below for the full text and any notes.
Fig. 4 · dose response
No human dose response curve exists
We draw this figure where the data supports it. For this compound in humans it does not, so the panel stays empty rather than borrowing an animal curve and implying it transfers.
Key studies & citations
- Human2008
The efficacy and safety of degarelix: a 12-month, comparative, randomized, open-label, parallel-group phase III study in patients with prostate cancer
610 men with prostate adenocarcinoma, median age 72, randomised to two degarelix regimens or monthly intramuscular leuprolide. Testosterone at or below 0.5 ng/mL at every monthly measurement from day 28 to day 364 in 97.2, 98.3 and 96.4 percent respectively, meeting non-inferiority. At day 3, testosterone was at or below 0.5 ng/mL in 96.1 and 95.5 percent of degarelix patients and in none on leuprolide. Injection site reactions 40 percent with subcutaneous degarelix versus under 1 percent with intramuscular leuprolide, P below 0.001.
BJU International - Human2021
Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Prostate Cancer: The Primary Results of the PRONOUNCE Randomized Trial
Randomised, open-label, in men with prostate cancer and known atherosclerotic cardiovascular disease. Enrolment stopped early at 545 of a planned 900 patients across 113 sites in 12 countries. Major adverse cardiovascular events at 12 months: 15 (5.5 percent) on degarelix versus 11 (4.1 percent) on leuprolide, hazard ratio 1.28 (95 percent CI 0.59 to 2.79), P equal to 0.53. The authors conclude that the relative cardiovascular safety of GnRH antagonists and agonists remains unresolved.
Circulation - Human2021
A Trial Comparing Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Advanced Prostate Cancer and Cardiovascular Disease
The registry record for PRONOUNCE. Overall status is TERMINATED, with actual enrolment 545 against a planned 900. Worth citing directly, because the published paper is routinely quoted as evidence that degarelix confers no cardiovascular benefit when the registry entry records a trial that was stopped before it could answer the question either way.
ClinicalTrials.gov
Frequently asked questions
What is degarelix approved for?
Treatment of patients with advanced prostate cancer. That is the entire indication on the United States label, and the licences in the United Kingdom, Australia and Canada are equally narrow.
Why choose degarelix over leuprolide?
Speed and the absence of a testosterone flare. By day 3 about 96 percent of degarelix patients were at castrate testosterone against none on leuprolide, so no antiandrogen cover is needed. Over 12 months the two are equivalent on suppression, and no trial has shown a survival difference.
Does degarelix protect the heart?
That has not been shown. PRONOUNCE tested it directly in men with existing cardiovascular disease, was terminated after 545 of a planned 900 patients, and found 15 events versus 11 with a hazard ratio of 1.28 and P equal to 0.53. The confidence interval is wide enough to include both meaningful benefit and meaningful harm. The question is open, not answered.
How bad are the injection site reactions?
Common. 40 percent of patients on subcutaneous degarelix in the pivotal trial, against under 1 percent on intramuscular leuprolide. Pain, erythema, swelling and induration are all listed at 10 percent or more on the label. For a monthly indefinite injection this is a genuine adherence issue rather than a cosmetic one.
How long do the effects last after stopping?
The terminal half-life is about 53 days, so exposure persists for weeks to months after the final injection. Testosterone recovery is correspondingly slow.