What is Abarelix?Abarelix is being marketed under the trade name Plenaxis® for the treatment of advanced or already metastatic hormone-dependent prostate cancer, where other therapies are no longer helpful.
Abarelix belongs to the group of gonadotropin releasing hormone antagonists (GnRH antagonists) and is a synthetic decapeptide. It is an alternative to surgical castration or therapy with GnRH analogues. Unlike GnRH analogues, Abarelix does not cause a - albeit short-term - increase in the hormone testosterone.
Such an increase can lead to an exacerbation of the symptoms - for example, to symptomatic bone metastases with spinal canal compression. On the other hand, when Abarelix is administered, there is an immediate, rapid and reliable decrease in the serum testosterone concentration to less than 0.2 ng / ml.
The drug is available as a powder as well as a solvent for preparing a suspension for injection.
Currently, long-term experience with Abarelix therapy is limited. Above all, even more exact results are missing regarding allergic reactions of the immediate type and to cardiac side effects.
If treated with Abarelix, the drug is injected intramuscularly. Abarelix acts as a competitive receptor antagonist in competition with GnRH for the relevant receptors for testosterone production. The drug blocks the responsible receptors. The testosterone production then expires immediately.
Since this works so well, without there being a first brief increase in the testosterone level, the combination with anti-androgens is unnecessary. Even after the first injection, testosterone levels drop to castration levels within a few days - up to one week - in around 70% of patients. As a result of a second injection on the 15th day of therapy with Abarelix, the desired target value is found in almost all patients. Compared to other medicines, Abarelix not only works intensively, but also significantly faster.
As with surgical castration, drug therapy with Abarelix can lead to: impotence, hot flashes, weight gain, and weakness due to the greatly reduced levels of testosterone.
Medical application & use
For advanced and already metastatic prostate cancer, Abarelix has a new type of drug at hand. The drug is especially recommended when other forms of therapy promise no more success.
Abarelix dramatically reduces testosterone levels in conjunction with rapid and ongoing control of the prostate tumor. It lowers the PSA level and reduces the volume of the prostate. Unlike conventional GnRH agonists, the GnRH Antigonist Abarelix does not initially lead to a short-term increase in testosterone levels.
The agent initiates the desired effect immediately after the first intramuscular injection. Hormone-sensitive prostate cancer respond very well to medication with Abarelix. The medicine is an excellent supplement or even an alternative to radiation or surgery for advanced carcinoma of the prostate.
Attention should be paid to the patient for at least 30 minutes following administration of the injection, as Abarelix may cause anaphylactoid reaction in just under 4% of those treated. Immediate treatment for a potentially life-threatening allergic reaction must be guaranteed.
In the preliminary discussion with the patient for the treatment with Abarelix it should absolutely be pointed out that after termination of the treatment with Abarelix the effect is reversible. After drug reduction even a rapid normalization of testosterone levels is to be expected because Abarelix does not alter the receptors. Concomitants such as hot flashes can be replaced quickly.
If necessary, a later therapy with Abarelix can be started later.
Risks & Side Effects
Within 30 minutes of Abarelix injection, very rare cases of severe systemic allergic reaction of the immediate type may occur. The symptoms are itching, urticaria, hypotension and possibly syncope.
Other potential side effects include disorders of the gastrointestinal tract and more frequent respiratory infections.
Abarelix is contraindicated in the heart's long QT syndrome as well as kidney and liver dysfunction. Like all GnRH antagonists, Abarelix should not be prescribed in the case of surgical castration.