Bottom line
Degarelix (Firmagon) is a synthetic linear decapeptide GnRH receptor antagonist approved for treatment of advanced prostate cancer. Unlike GnRH agonists, degarelix does not cause an initial testosterone surge (tumour flare) — testosterone suppression is rapid, with 96% of patients reaching castrate levels within 3 days. It is administered as a subcutaneous injection with a starting dose of 240 mg (two 120 mg injections) followed by 80 mg monthly maintenance. EU label also includes neo-adjuvant use with radiotherapy for high-risk localised prostate cancer.
Identity and composition
| Field | Verified information |
|---|---|
| Preferred name | Degarelix |
| Key aliases | Firmagon; FE200486 |
| Molecular/sequence identity | Ac-D-2Nal-D-4Cpa-D-3Pal-Ser-4Aph(Hor)-D-4Aph(Cbm)-Leu-Lys(iPr)-Pro-D-Ala-NH2 (decapeptide) |
| Modifications/form | Seven synthetic amino acids; D-amino acids at positions 1,2,3,6,10; acetate salt; lyophilised powder |
| Stable identifiers | PubChem CID 16136245; UNII SX0J4N42QR |
| Identity caveats | Not a GnRH agonist; distinct mechanism (receptor antagonist). Do not confuse with GnRH agonists (leuprolide, goserelin) |
Development and approval status
| Jurisdiction | Status and indication | Product/source | As of |
|---|---|---|---|
| US (FDA) | Approved: advanced prostate cancer | Firmagon (Ferring) NDA 022201 | 2008; label updated 02/2020 |
| EU (EMA) | Approved: advanced prostate cancer; high-risk localised prostate cancer (with RT) | Firmagon (Ferring) | 2009; renewed |
Mechanism and pharmacology
GnRH receptor antagonist. Competitively and reversibly blocks pituitary GnRH receptors, rapidly reducing LH and FSH release → rapid testosterone suppression without the initial surge (flare) seen with GnRH agonists. 96% of patients achieve castrate levels (≤0.5 ng/mL) by Day 3. Subcutaneous injection forms a depot gel for sustained release over 1 month.
Evidence by claim
| Claim/indication | Stage | Grade | Best human evidence | Main result | Important limitations |
|---|---|---|---|---|---|
| Advanced prostate cancer | Approved (FDA, EMA) | A | Phase 3 RCT vs leuprolide (n=610) | Non-inferior testosterone suppression; faster initial suppression; no flare; PSA progression-free survival similar | No overall survival difference shown; more injection site reactions vs leuprolide |
| High-risk localised prostate cancer (with RT) | Approved (EMA) | A | Phase 3 data (combination with RT) | Testosterone suppression maintained during RT | Not FDA-approved for this indication |
Key studies
| Study | Design/population | Exposure studied | Endpoints and result | Limitations |
|---|---|---|---|---|
| Phase 3 (CS21) | RCT; n=610 advanced PCa | Degarelix 240/80 mg SC vs degarelix 240/160 mg SC vs leuprolide 7.5 mg IM q28d | Testosterone suppression ≤0.5 ng/mL: degarelix 97-98% vs leuprolide 96% at Day 28; no testosterone surge with degarelix; faster suppression (Day 3: 96% vs 0%) | Non-inferiority; no OS difference; higher injection site reactions with degarelix |
Dose and administration evidence
Approved labeled regimen
The label summary below is product-, indication-, and jurisdiction-specific; consult the full current label and a licensed clinician/pharmacist.
Starting dose: 240 mg SC (two 120 mg injections, 40 mg/mL each)
Maintenance dose: 80 mg SC (single injection, 20 mg/mL) every 28 days, starting 28 days after starting dose
Route: Subcutaneous only (abdominal region); avoid areas under waistband or ribs
Must be administered by a healthcare professional
EU also approves use as neo-adjuvant/adjuvant with radiotherapy
What is not established
No established or recommended human dose for any unapproved indication.
Safety
Established label risks
Injection site reactions (very common, ~40%: pain, erythema, swelling, nodule).
Hot flashes (~25%).
Weight increase, fatigue, back pain.
Increased hepatic enzymes (transient; monitor LFTs).
QT interval prolongation (androgen deprivation effect).
Hypersensitivity / anaphylaxis — rare but label warning.
No tumour flare (key advantage vs GnRH agonists).
Unknowns and product-quality risks
Long-term (>1 year) safety data less extensive than GnRH agonists.
No oral formulation; injection-only.
Interactions and special populations
Hepatic impairment: Severe hepatic dysfunction is unstudied; use with caution. The sole FDA contraindication is serious hypersensitivity.
Renal impairment: No dose adjustment needed.
Pregnancy: Category X; not indicated in women.
QT-prolonging drugs: Use with caution.
Regulatory, compounding, and sport notes
US FDA: Prescription only; single-dose vials.
EU: Indication includes neo-adjuvant with RT.
WADA: Degarelix was not identified by exact name in the 2026 Prohibited List. S2.2.1 names GnRH and its agonist analogues in males; degarelix is a GnRH antagonist and suppresses LH/testosterone. This review therefore does not classify it as covered by that agonist wording, but athletes should seek a current case-specific determination. The separate 2026 Monitoring Program uses the broad phrase “GnRH analogues in female athletes under 18”; this page does not infer that the phrase includes this antagonist. Monitoring is not prohibition.
Compounding: No broad availability or legality conclusion is made; compounding rules are product-, jurisdiction-, and fact-specific.
Evidence gaps
Head-to-head overall survival data vs GnRH agonists.
Optimal sequencing after progression on GnRH agonists.
Long-term injection site outcome data.
Data in non-metastatic hormone-sensitive prostate cancer subsets.
Search notes
Databases and registries: DailyMed, Drugs@FDA, EMA, PubMed, ClinicalTrials.gov
Search terms: degarelix, Firmagon, GnRH antagonist, prostate cancer
Last searched: 2026-08-06
Inclusion emphasis: FDA label, EMA SmPC, phase 3 RCT
Sources
Firmagon Prescribing Information (Ferring, revised 02/2020). https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/022201s016lbl.pdf
DailyMed – FIRMAGON. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=ab11dd8a-0fd9-4013-89ab-e114557c7e4b
EMA EPAR – Firmagon. https://www.ema.europa.eu/en/documents/product-information/firmagon-epar-product-information_en.pdf
Medscape – Degarelix (Firmagon). https://reference.medscape.com/drug/firmagon-degarelix-999105
Klotz L, et al. Degarelix vs leuprolide in advanced prostate cancer. BJU Int. 2008;102(11):1531-8. PMID 19035858.
PubChem CID 122099 (degarelix).
WADA. 2026 Prohibited List. https://www.wada-ama.org/en/resources/world-anti-doping-program/prohibited-list