FIRMAGON

What it is

Degarelix is a third generation gonadotrophin releasing hormone (GnRH) antagonist (blocker). It is a synthetic decapeptide, which forms a depot following subcutaneous injection; this depot formation results in a sustained release of degarelix. FIRMAGON delivers degarelix acetate, equivalent to 120 mg of degarelix for the starting dose, and 80 mg of degarelix for the maintenance dose.

Approved indications

— Treatment of patients with prostate cancer in whom androgen deprivation is warranted.

Dosing overview

The starting dose is 240 mg administered as two subcutaneous injections of 120 mg at a concentration of 40 mg/mL. The maintenance dose is 80 mg administered as one subcutaneous injection at a concentration of 20 mg/mL, given monthly. The first maintenance dose should be given one month after the starting dose. Testosterone suppression occurs immediately after administration of the starting dose with 96% of the patients having plasma testosterone at medical castration levels (T ≤ 0.5 ng/mL) after three days and 100% after one month. Long term treatment with the maintenance dose up to 1 year shows that 97% of the patients have sustained suppressed testosterone levels (T ≤ 0.5 ng/mL).

Key safety warnings

Long-term androgen deprivation therapy may prolong the QT interval. FIRMAGON has not been studied in patients with a history of a corrected QT interval over 450 msec, in patients with a history of or risk factors for torsades de pointes and in patients receiving concomitant medicinal products that might prolong the QT interval (such as Class IA or Class III antiarrhythmic medications). Therefore in such patients, the benefit/risk ratio of FIRMAGON must be thoroughly appraised. Decreased bone density has been reported in the medical literature in men who have had orchiectomy or who have been treated with a GnRH agonist. It can be anticipated that long periods of testosterone suppression in men will have effects on bone density. The most commonly observed adverse reactions during FIRMAGON therapy were hot flushes and weight increase, reported in 25% and 7%, respectively, of patients receiving treatment for one year, and injection site adverse events. The injection site adverse events reported were mainly pain and erythema, reported in 28% and 17% of patients, respectively.

Contraindications

Hypersensitivity to degarelix or any other GnRH antagonists, or to any of the product excipients. FIRMAGON is not indicated in women or paediatric patients.

PBS listing

FIRMAGON is listed on the PBS in two strengths: powder for injection 80 mg (as acetate) with ex-manufacturer price of A$314.73, and powder for injection 120 mg (as acetate) with ex-manufacturer price of A$329.45. Both listings are restricted benefit.

Regulatory history

FIRMAGON was first approved on 16 February 2010. FIRMAGON degarelix (as acetate) composite packs for both 80 mg and 120 mg were first listed on the ARTG on 31 October 2012. In March 2017, the PBAC recommended a change to amend the listing from Authority Required (Streamlined) to a Restricted Benefit to be consistent with other listed GnRH analogues, for treatment of locally advanced or metastatic carcinoma of the prostate.