There are many different types of drugs used for hormone therapy in the treatment of prostate cancer. One of the newer classes of drugs include the GnRH antagonists. Degarelix (aka Firmagon) is the one drug in this class that is currently approved for prostate cancer.
Degarelix, like the other hormone therapy drugs, was developed to suppress testosterone. What makes this class of drugs different is that it also avoids the flare phenomenon that is observed with the GnRH agonists like Lupron.
The flare phenomenon, where the body initially pumps out additional levels of testosterone in response to the GnRH agonist being introduced before the production is cut back is very dangerous, especially for men with either very aggressive or advanced prostate cancer. This flare, although not limited, can be negated when a GnRH drug is used along with another drug called an anti-androgen that blocks the testosterone from being able to interact with the hormone receptors. Examples of an anti-androgen drug commonly used in men undergoing hormone therapy who are still castrate responsive is Casodex, (biculamide).
However, the GnRH antagonists like degarelix has a different mode of action than the GnRH agonist. The GnRH antagonist is designed to bind to the GnRH receptors on the pituitary gonadotropin-producing cells, not stimulating an initial release of LH or FSH that causes the initial large surge in testosterone that we see with the GnRH agonists.
The FDA, because of the positive results that were demonstrated in a phase III trial approved Degarelix. The phase 3 trial consisted of 610 men with prostate cancer who were randomly assigned to receive the then investigational drug, degarelix or the standard of care, Lupron.
The trial demonstrated that degarelix, within three days of starting the drug, suppressed testosterone levels in 96 percent of the men in the trial, a result that was far superior to the alternative Leuprolide (GnRH agonists) drugs. The trial also showed that the suppression of serum testosterone levels was maintained for the duration of the 12-month trial.
There was additional data presented at the 2011 Genitourinary Cancers Symposium that showed that the incidence of PSA failure during the study on degarelix was significantly lower than that experienced by the leuprolide treatment arm.
Secondary analyses from the phase III trial data showed that there was also a greater suppression of serum alkaline phosphatase in the men who took degarelix when compared to those who took the traditional leuprolide drugs. Alkaline phosphatase is a bio-marker for bone metastases.
However, it isn’t clear if greater control of serum alkaline phosphatase translates into better control of skeletal metastasis, but it might.
One of the biggest down sides of degarelix is the frequent local injection site reactions that can be very painful experienced by many men taking degarelix. This complication was much more common in men taking degarelix then the leuprolide drugs.
A secondary analysis of cardiovascular complications in the phase III trial found a similar cardiovascular safety profile for both degarelix and leuprolide drugs.
There was a follow up study where those men who were initially assigned to the experimental degarelix group were continued on maintenance therapy for up to five years, and those originally assigned to the standard of care, the leuprolide group were given the opportunity to cross over to degarelix (take degarelix instead of the leuprolide).
They found that the treatment with degarelix was well tolerated during this maintenance phase and testosterone suppression was sustained throughout this period.
In an individual patient meta-analysis of randomized trials comparing degarelix with either leuprolide or goserelin in 1925 men in five trials it was found that progression-free survival was longer in those treated with degarelix. These results do need to be taken with a little grain of sand as the treatment in these trials was limited to either 3 or 12 months, and there were only four deaths due to prostate cancer in this time period.
When you decide on what might be the best drug for you, you should also remember that degarelix must be given like clock work every thirty days. Since the alternative drugs can be given in one month, three month or six month doses you should consider your ability and willingness to go to the doctor every 30 days to get the degarelix if you decide it is your drug of choice.
Degarelix does seem to be a superior drug, but its economic costs are also higher.
Deciding which drug you takes needs a careful conversation with your doctor as well as a conversation with your insurance company.