Gonax

Gonax is a gonadotrophin releasing hormone (GnRH) antagonist indicated for treatment of adult male patients with advanced hormone-dependent prostate cancer.

Posology

The first maintenance dose should be given one month after the starting dose.

The therapeutic effect of degarelix should be monitored by clinical parameters and prostate specific antigen (PSA) serum levels. Clinical studies have shown that testosterone (T) suppression occurs immediately after administration of the starting dose with 96% of the patients having serum testosterone levels corresponding to medical castration (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).

In case the patient's clinical response appears to be sub-optimal, it should be confirmed that serum testosterone levels are remaining sufficiently suppressed.

Since degarelix does not induce a testosterone surge it is not necessary to add an anti-androgen as surge protection at initiation of therapy.

Special populations

Elderly, hepatically or renally impaired patients:

There is no need to adjust the dose for the elderly or in patients with mild or moderate liver or kidney function impairment. Patients with severe liver or kidney impairment have not been studied and caution is therefore warranted.

Paediatric population

There is no relevant use of Gonax in children and adolescents in the treatment of adult male patients with advanced hormone-dependent prostate cancer.

Method of administration

Gonax must be reconstituted prior to administration.

Gonax is for subcutaneous use ONLY, not to be administered intravenously. Intramuscular administration is not recommended as it has not been studied.

Gonax is administered as a subcutaneous injection in the abdominal region. The injection site should vary periodically. Injections should be given in areas where the patient will not be exposed to pressure e.g. not close to waistband or belt and not close to the ribs.

Hypersensitivity to the active substance or to any of the excipients listed in section 6.

Effect on QT/QTc interval

Long-term androgen deprivation therapy may prolong the QT interval. In the confirmatory study comparing Gonax to leuprorelin periodic (monthly) electrocardiograms (ECGs) were performed; both therapies showed QT/QTc intervals exceeding 450 msec in approximately 20% of the patients, and 500 msec in 1% and 2% of the degarelix and leuprorelin patients, respectively.

Gonax 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. Therefore in such patients, the benefit/risk ratio of Gonax must be thoroughly appraised.

A thorough QT study showed that there was no intrinsic effect of degarelix on QT/QTc interval.

Hepatic impairment

Patients with known or suspected hepatic disorder have not been included in long-term clinical trials with degarelix. Mild, transient increases in ALT and AST have been seen, these were not accompanied by a rise in bilirubin or clinical symptoms. Monitoring of liver function in patients with known or suspected hepatic disorder is advised during treatment. The pharmacokinetics of degarelix has been investigated after single intravenous administration in subjects with mild to moderate hepatic impairment.

Renal impairment

Degarelix has not been studied in patients with severe renal impairment and caution is therefore warranted.

Hypersensitivity

Degarelix has not been studied in patients with a history of severe untreated asthma, anaphylactic reactions or severe urticaria or angioedema.

Changes in bone density

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. Bone density has not been measured during treatment with degarelix.

Glucose tolerance

A reduction in glucose tolerance has been observed in men who have had orchiectomy or who have been treated with a GnRH agonist. Development or aggravation of diabetes may occur; therefore diabetic patients may require more frequent monitoring of blood glucose when receiving androgen deprivation therapy. The effect of degarelix on insulin and glucose levels has not been studied.

Cardiovascular disease

Cardiovascular disease such as stroke and myocardial infarction has been reported in the medical literature in patients with androgen deprivation therapy. Therefore, all cardiovascular risk factors should be taken into account.

Gonax has no or negligible influence on the ability to drive and use machines. Fatigue and dizziness are common adverse reactions that might influence the ability to drive and use machines.

Summary of the safety profile

The most commonly observed adverse reactions during degarelix therapy in the confirmatory phase III study (N=409) were due to the expected physiological effects of testosterone suppression, including hot flushes and weight increase (reported in 25% and 7%, respectively, of patients receiving treatment for one year), or injection site adverse reactions. Transient chills, fever or influenza like illness were reported to occur hours after dosing (in 3%, 2% and 1% of patients, respectively).

The injection site adverse reactions reported were mainly pain and erythema, reported in 28% and 17% of patients, respectively, less frequently reported were swelling (6%), induration (4%) and nodule (3%). These events occurred primarily with the starting dose whereas during maintenance therapy with the 80 mg dose, the incidence of these events pr 100 injections was: 3 for pain and <1 for erythema, swelling, nodule and induration. The reported events were mostly transient, of mild to moderate intensity and led to very few discontinuations (<1%). Serious injection site reactions were very rarely reported such as injection site infection, injection site abscess or injection site necrosis that could require surgical treatment/drainage.

Tabulated list of adverse reactions

The frequency of undesirable effects listed below is defined using the following convention: Very common (> 1/10); common (> 1/100 to < 1/10); uncommon (> 1/1,000 to < 1/100), rare (> 1/10,000 to <1/1,000) and very rare (<1/10,000). Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness.

Table 1: Frequency of adverse drug reactions reported in 1,259 patients treated for a total of 1781 patient years (phase II and III studies) and from post-marketing reports

*Known physiological consequence of testosterone suppression

Description of selected adverse reactions

Changes in laboratory parameters

Changes in laboratory values seen during one year of treatment in the confirmatory phase III study (N=409) were in the same range for degarelix and a GnRH-agonist (leuprorelin) used as comparator. Markedly abnormal (>3*ULN) liver transaminase values (ALT, AST and GGT) were seen in 2-6% of patients with normal values prior to treatment, following treatment with both medicinal products. Marked decrease in haematological values, hematocrit (≤0.37) and hemoglobin (≤115 g/l) were seen in 40% and 13-15%, respectively, of patients with normal values prior to treatment, following treatment with both medicinal products. It is unknown to what extent this decrease in haematological values was caused by the underlying prostate cancer and to what extent it was a consequence of androgen deprivation therapy. Markedly abnormal values of potassium (>5.8 mmol/l), creatinine (>177 μmol/l) and BUN (>10.7 mmol/l) in patients with normal values prior to treatment, were seen in 6%, 2% and 15% of degarelix treated patients and 3%, 2% and 14% of leuprorelin treated patients, respectively.

Changes in ECG measurements

Changes in ECG measurements seen during one year of treatment in the confirmatory phase III study (N=409) were in the same range for degarelix and a GnRH-agonist (leuprorelin) used as comparator. Three (<1%) out of 409 patients in the degarelix group and four (2%) out of 201 patients in the leuprorelin 7.5 mg group, had a QTcF > 500 msec. From baseline to end of study the median change in QTcF for degarelix was 12.0 msec and for leuprorelin was 16.7 msec.

The lack of intrinsic effect of degarelix on cardiac repolarisation (QTcF), heart rate, AV conduction, cardiac depolarisation, or T or U wave morphology was confirmed in a thorough QT study in healthy subjects (N=80) receiving an i.v. infusion of degarelix over 60 min, reaching a mean C_max of 222 ng/mL, approx. 3-4-fold the C_max obtained during prostate cancer treatment.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme, website: www.mhra.gov.uk/yellowcard.

There is no clinical experience with the effects of an acute overdose with degarelix. In the event of an overdose the patient should be monitored and appropriate supportive treatment should be given, if considered necessary.

Pharmacotherapeutic group: Endocrine therapy, Other hormone antagonists and related agents, ATC code: L02BX02

Mechanism of action

Degarelix is a selective gonadotrophin releasing-hormone (GnRH) antagonist that competitively and reversibly binds to the pituitary GnRH receptors, thereby rapidly reducing the release of the gonadotrophins, luteinizing hormone (LH) and follicle stimulating hormone (FSH), and thereby reducing the secretion of testosterone (T) by the testes. Prostatic carcinoma is known to be androgen sensitive and responds to treatment that removes the source of androgen. Unlike GnRH agonists, GnRH antagonists do not induce a LH surge with subsequent testosterone surge/tumour stimulation and potential symptomatic flare after the initiation of treatment.

A single dose of 240 mg degarelix, followed by a monthly maintenance dose of 80 mg, rapidly causes a decrease in the concentrations of LH, FSH and subsequently testosterone. The serum concentration of dihydrotestosterone (DHT) decreases in a similar manner to testosterone.

Degarelix is effective in achieving and maintaining testosterone suppression well below medical castration level of 0.5 ng/ml. Maintenance monthly dosing of 80 mg resulted in sustained testosterone suppression in 97% of patients for at least one year. No testosterone microsurges were observed after re-injection during degarelix treatment. Median testosterone levels after one year of treatment were 0.087 ng/ml (interquartile range 0.06-0.15) N=167.

Results of the confirmatory Phase III study

The efficacy and safety of degarelix was evaluated in an open-label, multi-centre, randomised, active comparator controlled, parallel-group study. The study investigated the efficacy and safety of two different degarelix monthly dosing regimens with a starting dose of 240 mg (40 mg/ml) followed by monthly doses subcutaneous administration of 160 mg (40 mg/ml) or 80 mg (20 mg/ml), in comparison to monthly intramuscular administration of 7.5 mg leuprorelin in patients with prostate cancer requiring androgen deprivation therapy. In total 620 patients were randomised to one of the three treatment groups, of which 504 (81%) patients completed the study. In the degarelix 240/80 mg treatment group 41 (20%) patients discontinued the study, as compared to 32 (16%) patients in the leuprorelin group.

Of the 610 patients treated

- 31% had localised prostate cancer

- 29% had locally advanced prostate cancer

- 20% had metastatic prostate cancer

- 7% had an unknown metastatic status

- 13% had previous curative intent surgery or radiation and a rising PSA

Baseline demographics were similar between the arms. The median age was 74 years (range 47 to 98 years). The primary objective was to demonstrate that degarelix is effective with respect to achieving and maintaining testosterone suppression to below 0.5 ng/ml, during 12 months of treatment.

The lowest effective maintenance dose of 80 mg degarelix was chosen.

Attainment of serum testosterone (T) ≤0.5 ng/ml

Gonax is effective in achieving fast testosterone suppression, see Table 2.

Table 2: Percentage of patients attaining T≤0.5 ng/ml after start of treatment.

Avoidance of testosterone surge

Surge was defined as testosterone exceeding baseline by >15% within the first 2 weeks.

None of the degarelix-treated patients experienced a testosterone surge; there was an average decrease of 94% in testosterone at day 3. Most of the leuprorelin-treated patients experienced testosterone surge; there was an average increase of 65% in testosterone at day 3. This difference was statistically significant (p<0.001).

Figure 1: Percentage change in testosterone from baseline by treatment group until day 28 (median with interquartile ranges).

The primary end-point in the study was testosterone suppression rates after one year of treatment with degarelix or leuprorelin. The clinical benefit for degarelix compared to leuprorelin plus anti-androgen in the initial phase of treatment has not been demonstrated.

Testosterone Reversibility

In a study involving patients with rising PSA after localised therapy (mainly radical prostatectomy and radiation) were administered Gonax for seven months followed by a seven months monitoring period. The median time to testosterone recovery (>0.5 ng/mL, above castrate level) after discontinuation of treatment was 112 days (counted from start of monitoring period, i.e 28 days after last injection). The median time to testosterone >1.5 ng/mL (above lower limit of normal range) was 168 days.

Long-term effect

Successful response in the study was defined as attainment of medical castration at day 28 and maintenance through day 364 where no single testosterone concentration was greater than 0.5 ng/ml.

Table 3: Cumulative probability of testosterone ≤0.5 ng/ml from Day 28 to Day 364.

* Kaplan Meier estimates within group

Attainment of prostate specific antigen (PSA) reduction

Tumour size was not measured directly during the clinical trial programme, but there was an indirect beneficial tumour response as shown by a 95% reduction after 12 months in median PSA for degarelix.

The median PSA in the study at baseline was:

- for the degarelix 240/80 mg treatment group 19.8 ng/ml (interquartile range: P25 9.4 ng/ml, P75 46.4 ng/ml)

- for the leuprorelin 7.5 mg treatment group 17.4 ng/ml (interquartile range: P25 8.4 ng/ml, P75 56.5 ng/ml)

Figure 2: Percentage change in PSA from baseline by treatment group until day 56 (median with interquartile ranges).

This difference was statistically significant (p<0.001) for the pre-specified analysis at day 14 and day 28.

Prostate specific antigen (PSA) levels are lowered by 64% two weeks after administration of degarelix, 85% after one month, 95% after three months, and remained suppressed (approximately 97%) throughout the one year of treatment.

From day 56 to day 364 there were no significant differences between degarelix and the comparator in the percentage change from baseline.

Effect on prostate volume

Three months therapy with degarelix (240/80 mg dose regimen) resulted in a 37% reduction in prostate volume as measured by trans-rectal ultrasound scan (TRUS) in patients requiring hormonal therapy prior to radiotherapy and in patients who were candidates for medical castration. The prostate volume reduction was similar to that attained with goserelin plus anti-androgen protection.

Effect on QT/QTc intervals

In the confirmatory study comparing Gonax to leuprorelin periodic electrocardiograms were performed. Both therapies showed QT/QTc intervals exceeding 450 msec in approximately 20% of the patients. From baseline to end of study the median change for Gonax was 12.0 msec and for leuprorelin it was 16.7 msec.

Anti-degarelix antibody

Anti-degarelix antibody development has been observed in 10% of patients after treatment with Gonax for one year and 29% of patients after treatment with Gonax for up to 5.5 years. There is no indication that the efficacy or safety of Gonax treatment is affected by antibody formation after up to 5.5 years of treatment.

Paediatric population

Absorption

Following subcutaneous administration of 240 mg degarelix at a concentration of 40 mg/ml to prostate cancer patients in the pivotal study CS21, AUC_{0-28 days} was 635 (602-668) day*ng/ml, C_max was 66.0 (61.0-71.0) ng/ml and occurred at t_max at 40 (37-42) hours. Mean trough values were approximately 11-12 ng/ml after the starting dose and 11-16 ng/ml after maintenance dosing of 80 mg at a concentration of 20 mg/ml. C_max degarelix plasma concentration decreases in a biphasic fashion, with a mean terminal half-life (t_½) of 29 days for the maintenance dose. The long half-life after subcutaneous administration is a consequence of a very slow release of degarelix from the depot formed at the injection site(s). The pharmacokinetic behaviour of the medicinal product is influenced by its concentration in the solution for injection. Thus, C_max and bioavailability tend to decrease with increasing dose concentration while the half-life is increased. Therefore, no other dose concentrations than the recommended should be used.

Distribution

The distribution volume in healthy elderly men is approximately 1 l/kg. Plasma protein binding is estimated to be approximately 90%.

Biotransformation

Degarelix is subject to common peptidic degradation during the passage of the hepato-biliary system and is mainly excreted as peptide fragments in the faeces. No significant metabolites were detected in plasma samples after subcutaneous administration. In vitro studies have shown that degarelix is not a substrate for the human CYP450 system.

Elimination

In healthy men, approximately 20-30% of a single intravenously administered dose is excreted in the urine, suggesting that 70-80% is excreted via the hepato-biliary system. The clearance of degarelix when administered as single intravenous doses (0.864-49.4 µg/kg) in healthy elderly men was found to be 35-50 ml/h/kg.

Special populations

Patients with renal impairment

No pharmacokinetic studies in renally impaired patients have been conducted. Only about 20-30% of a given dose of degarelix is excreted unchanged by the kidneys. A population pharmacokinetics analysis of the data from the confirmatory Phase III study has demonstrated that the clearance of degarelix in patients with mild to moderate renal impairment is reduced by approximately 23%; therefore, dose adjustment in patients with mild or moderate renal impairment is not recommended. Data on patients with severe renal impairment is scarce and caution is therefore warranted in this patient population.

Patients with hepatic impairment

Degarelix has been investigated in a pharmacokinetic study in patients with mild to moderate hepatic impairment. No signs of increased exposure in the hepatically impaired subjects were observed compared to healthy subjects. Dose adjustment is not necessary in patients with mild or moderate hepatic impairment. Patients with severe hepatic dysfunction have not been studied and caution is therefore warranted in this group.

Animal reproduction studies showed that degarelix caused infertility in male animals. This is due to the pharmacological effect; and the effect was reversible.

In female reproduction toxicity studies degarelix revealed findings expected from the pharmacological properties. It caused a dosage dependent prolongation of the time to mating and to pregnancy, a reduced number of corpora lutea, and an increase in the number of pre- and post-implantation losses, abortions, early embryo/foetal deaths, premature deliveries and in the duration of parturition.

Preclinical studies on safety pharmacology, repeated dose toxicity, genotoxicity, and carcinogenic potential revealed no special hazard for humans. Both in vitro and in vivo studies showed no signs of QT prolongation.

No target organ toxicity was observed from acute, subacute and chronic toxicity studies in rats and monkeys following subcutaneous administration of degarelix. Drug-related local irritation was noted in animals when degarelix was administered subcutaneously in high doses.

In the absence of compatibility studies, this medicinal product must not be mixed with other medicinal products.

The instructions for reconstitution must be followed carefully.

Administration of other concentrations is not recommended because the gel depot formation is influenced by the concentration. The reconstituted solution should be a clear liquid, free of undissolved matter.

NOTE:

- THE VIALS SHOULD NOT BE SHAKEN

The pack contains two vials of powder and two pre-filled syringes with solvent that must be prepared for subcutaneous injection. Hence, the procedure described below need to be repeated a second time.

No special requirements for disposal.