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OtherEvidence A4 cited

Degarelix

aka Firmagon · FE200486 · GnRH antagonist

Degarelix is a synthetic decapeptide that functions as a gonadotropin-releasing hormone (GnRH) receptor antagonist. Marketed as Firmagon, it is used in the treatment of advanced hormone-dependent prostate cancer. Unlike GnRH agonists such as leuprolide, degarelix does not cause an initial surge in testosterone (the testosterone flare), making it particularly suitable for patients where rapid testosterone suppression is clinically necessary. It achieves castrate-level testosterone within three days of the initial dose, providing immediate therapeutic benefit. Degarelix works by competitively blocking GnRH receptors in the anterior pituitary, directly suppressing LH and FSH secretion without initial receptor stimulation.

Molecular wt
1632.3g/mol
Formula
C82H103ClN18O16
CAS
214766-78-6
Half-life
40 days
established
Tmax
2 days
PubChem
16136245

Sequence

Read this before quoting the sequence
Synthetic linear decapeptide amide containing seven unnatural amino acids, five of which are D-amino acids; a one-letter representation is not possible. FDA label chemical name: 'D-Alaninamide, N-acetyl-3-(2-naphthalenyl)-D-alanyl-4-chloro-D-phenylalanyl-3-(3-pyridinyl)-D-alanyl-L-seryl-4-[[[(4S)-hexahydro-2,6-dioxo-4-pyrimidinyl]carbonyl]amino]-L-phenylalanyl-4-[(aminocarbonyl)amino]-D-phenylalanyl-L-leucyl-N6-(1-methylethyl)-L-lysyl-L-prolyl'. Supplied as the acetate salt.
Source ↗

Mechanism of action

Degarelix competitively binds to GnRH receptors on gonadotroph cells in the anterior pituitary gland, preventing endogenous GnRH from activating these receptors. This immediate blockade results in rapid suppression of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion, leading to swift decline in testosterone production by the testes. Unlike GnRH agonists which initially stimulate the receptor before downregulation occurs, degarelix provides immediate antagonism without any initial hormonal surge or flare phenomenon. Castrate testosterone levels are achieved typically within one to three days.

What the evidence actually shows

Grade A

Degarelix has been extensively evaluated in Phase 3 clinical trials for advanced prostate cancer. The pivotal CS21 trial demonstrated testosterone suppression comparable to leuprolide without the initial flare. Over 95% of patients achieved castrate testosterone levels by day 3. Long-term studies confirm sustained efficacy and show potential advantages in PSA progression-free survival. Approved by FDA, EMA, and MHRA.

Regulatory status

Status
Approved prescription medicine. US: FIRMAGON, NDA 022201, original approval 24 December 2008, sponsor Ferring; marketing status 'Prescription'. EU: Firmagon authorised 17 February 2009, MAH Ferring Pharmaceuticals A/S.
Approved as
FIRMAGON (degarelix for injection), a GnRH receptor antagonist for advanced hormone-dependent prostate cancer; the EU indication also covers high-risk localised disease with radiotherapy and neo-adjuvant use before radiotherapy.
Clinical stage
Approved and marketed; further phase II/III trials ongoing in neoadjuvant and combination settings.
WADA
Not named on the WADA 2026 Prohibited List. S2.2.1 names 'gonadotrophin-releasing hormone (GnRH, gonadorelin) and its agonist analogues (e.g. buserelin, deslorelin, goserelin, histrelin, leuprorelin, nafarelin and triptorelin)' - agonists only; no GnRH antagonist (degarelix, cetrorelix, ganirelix) is named.
Source ↗

Pharmacokinetics

Half-life
40 days
Tmax
2 days
Absorption
subcutaneous
Elimination
hepatic
Washout
60 days
Low-confidence pharmacokinetics
These figures are recorded as established rather than measured in a published PK study. Treat them as an order of magnitude. Anything downstream of them — accumulation, steady state, washout — inherits that uncertainty.

Dosing — what backs each figure

Degarelix is an FDA-approved GnRH receptor antagonist and an oncology drug: 240 mg subcutaneous loading dose (2 x 120 mg) then 80 mg subcutaneously every 28 days, indefinitely, for androgen deprivation in advanced prostate cancer. It is prescription-only chemical castration therapy, not a wellness or performance compound, and there is no such thing as a degarelix 'cycle'.

ClinicalApproved labelling or a published human trial

  • Loading dose 240 mg given as two subcutaneous injections of 120 mg (40 mg/mL); first maintenance dose 28 days later, then 80 mg (20 mg/mL) as a single subcutaneous injection every 28 days. Abdominal injection only; must be given within 1 hour of reconstitution with Sterile Water for Injection

    adult men with advanced prostate cancer (androgen deprivation therapy) · subcutaneous

    FDA prescribing information, FIRMAGON (degarelix) for injection, NDA 022201 ↗

Handling and storage

Lyophilized
Store the FIRMAGON kit at 20 C to 25 C (68 F to 77 F); excursions permitted to 15 C to 30 C (59 F to 86 F) [USP Controlled Room Temperature]. Refrigeration is NOT required and is not specified.
Reconstituted
Reconstituted drug must be administered within one hour after addition of Sterile Water for Injection, USP. No longer-term reconstituted storage is permitted by the label.
Solvent
Sterile Water for Injection, USP (supplied in the kit as a prefilled syringe)

Do not shake the vials during reconstitution (the label instructs gentle swirling only, and explicitly 'Do not shake the vials'). Supplied as a white to off-white lyophilised powder of degarelix acetate with mannitol (150 mg per 120 mg dose; 200 mg per 80 mg dose). The label gives no photostability statement, so lightSensitive is left null rather than guessed.

Source ↗
→ Reconstitution walkthrough→ Reconstitution calculator

Safety

References (4)

Data provenance

Chemistry and citations on this page were checked against primary sources on 2026-08-14. Values that could not be verified were left blank rather than filled with a plausible guess.

Research use only
This profile is educational reference material. It is not medical advice, not a prescription, and not an endorsement of self-administration. Compounds discussed here are research chemicals and most are not approved for human therapeutic use.

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