Degarelix (Firmagon): Uses, Mechanism, and Side Effects

Men diagnosed with advanced prostate cancer often want to understand how hormone-blocking therapy actually works before starting treatment. Degarelix, sold under the brand name Firmagon, is one option used to lower testosterone in this setting.

Key takeaways

• Degarelix is a GnRH receptor antagonist approved for advanced prostate cancer, marketed as Firmagon.
• It works by blocking pituitary GnRH receptors, which lowers gonadotropin release and reduces testosterone.
• More than 170 registered clinical trials have studied degarelix, including comparisons against other hormone therapies.
• The most frequently reported adverse events involve injection site reactions and general fatigue-type symptoms.
• The label does not carry a boxed warning.

What Degarelix Is

Degarelix belongs to a class of drugs called GnRH receptor antagonists. It binds reversibly to GnRH receptors in the pituitary gland. This binding reduces the release of gonadotropins, hormones that in turn signal the testes to produce testosterone. The net effect is a drop in circulating testosterone, which is the therapeutic target in hormone-sensitive prostate cancer.

What Degarelix Is Approved For

Degarelix, marketed as Firmagon, is indicated for the treatment of patients with advanced prostate cancer. The label does not include a boxed warning. No other approved uses are listed on the label.

What the Evidence Shows

Degarelix has been studied across 173 registered clinical trials. One completed Phase 2 trial examined PET-PSMA imaging combined with androgen blockade in localized prostate adenocarcinoma. A Phase 3 trial comparing the cardiovascular safety of degarelix versus leuprolide in patients with advanced prostate cancer and cardiovascular disease was terminated. Separately, a Phase 3 trial known as PREDICT-RT is evaluating treatment intensity in high-risk prostate cancer based on gene risk scoring and remains active but not recruiting.

Reported Side Effects

Reported side effect data reflect counts of adverse event reports submitted to a safety database, not confirmed incidence or proof of causation. The most frequently reported reactions relate to injection site reactions, including pain, erythema, and swelling, alongside general symptoms of fatigue, asthenia, and hot flush. Death and product storage error were also reported, each with 209 reports, though these entries reflect report volume rather than established cause.