Degarelix

In plain language

Degarelix (brand name Firmagon) is an FDA-approved medicine for advanced prostate cancer. It is a lab-made peptide of 10 amino acids.

Many prostate cancers need testosterone to grow. Degarelix quickly lowers testosterone by blocking the signal from the brain that tells the testes to make it. Unlike some older drugs, it does not cause a short spike in testosterone at the start. It is given as a monthly injection under the skin.

For students

Degarelix is a synthetic decapeptide (about 1,632 Da) containing several unnatural D-amino acids. It is a gonadotropin-releasing hormone (GnRH) receptor antagonist: it competitively blocks pituitary GnRH receptors, reducing LH and FSH and therefore testosterone.

Because it blocks rather than overstimulates the receptor, it avoids the initial "flare" seen with GnRH agonists such as leuprolide. After subcutaneous injection it forms a depot that releases the drug slowly, allowing monthly maintenance doses. It was approved in 2008.

For researchers and instructors

Pharmacology. Testosterone reaches castrate levels within about three days in most patients, compared with two to four weeks for agonists.

Clinical evidence. The pivotal 12-month trial versus leuprolide showed non-inferior testosterone suppression with faster onset and no surge.

Safety. Injection-site reactions are common. Androgen-deprivation effects include hot flashes, weight gain, bone loss and QT prolongation risk.

Status. FDA-approved (Firmagon). Oral non-peptide GnRH antagonists (relugolix) now offer an alternative.