27th Congress of the Société Internationale d'Urologie, Hawaii, USA
October 5, 2004
Treatment with degarelix, a novel gonadotrophin-releasing hormone (GnRH) blocker, causes significant reductions in testosterone and prostate-specific antigen (PSA) levels.
The first results from trials of degarelix in patients were presented today. The new findings from a multi-centre, phase II trial in 129 men and conducted in the United Kingdom support positive results seen from earlier research on degarelix, and move it closer to phase III trials, say doctors involved in the study.
"Degarelix is one of the first drugs in an emerging, novel class of prostate cancer treatments, in a field where new options to treat tumours that are responsive to hormonal manipulation therapy are desperately needed," commented Mr Philip Weston MCh FRCS (Urol), Consultant Urological Surgeon of Pinderfields Hospital in Wakefield, UK. "Degarelix potentially offers an alternative for these patients, as it may avoid both the drawbacks associated with traditional agonist therapy, such as the severe flare of disease and symptoms caused by the initial testosterone surge, and the permanence of surgical options."
"Prostate cancer is the second leading cause of cancer death among men yet there is considerable dispute on when and how best to treat it. Consequently, there is an ongoing need for better treatments," explained Dr Bo-Eric Persson, Director, Medical Sciences, Urology / Oncology for Ferring Pharmaceuticals, makers of the new compound. "We believe that degarelix has the potential to answer some of these unmet needs in prostate cancer treatment.''
HOW DEGARELIX WORKS
"The majority of tumours found in newly-diagnosed patients are dependent on testosterone for their continued growth and are linked to raised levels of PSA. Rapidly and directly blocking the body's normal production of testosterone with degarelix may represent a value for the patients," Dr Persson continued.
Currently used hormonal treatments for prostate cancer include GnRH agonists. Unlike degarelix, these therapies stimulate the natural hormone's receptor on the pituitary gland. These agents also have a desired clinical effect, but they stimulate testosterone production before shutting it down. This initial stimulation of the receptors stimulate hormone-dependent tumour growth rather than inhibit it, and may lead to a worsening of cancer symptoms or flare.
Degarelix is designed to target and block the GnRH receptor. This rapidly prevents the production of testosterone and avoids the risk of flare.
NEW DEGARELIX STUDY FINDINGS
The effectiveness of degarelix in suppressing testosterone and reducing PSA levels was studied in the reported randomised, phase II study at 13 centres across the UK. The study compared the effectiveness and safety of three different dosing regimens of degarelix in 129 men with early and late-stage prostate cancer, who had an initial median PSA level of 61 ng/ml and were recommended as candidates for androgen (male hormone) deprivation therapy.
All three dosing schemes of degarelix had fast inhibitory effects on testosterone and PSA levels in a dose-dependent manner.
At the highest dose, 97.5 per cent of patients (n=32) experienced a reduction in testosterone to target levels of less than 0.5 ng/ml within three days of treatment. All the patients in this group reached target suppression levels within the first 28 days and this was sustained in 87.5 per cent of the patients on treatment through to the end of the six-month study period. Five weeks after initiation of treatment the median PSA-reduction in patients on treatment was 90 per cent compared to baseline.
There were no serious adverse events during treatment, however six (4.7 per cent) of the 129 patients withdrew from the study. The most frequently reported adverse reactions to therapy were associated with the drug's intended action in decreasing secretion of testosterone.
"Degarelix may solve some key problems associated with currently available GnRH agonists and antagonists," Dr Weston said. "In our study, injection with degarelix rapidly reduced levels of testosterone without the hormonal flare associated with GnRH agonists, and it maintained target levels, resulting in a fast decrease in PSA levels."
In summary, the researchers conclude, "Results from additional, ongoing, dose ranging studies are required to define the optimal treatment regimen, but these results are extremely encouraging in taking degarelix forward to phase III clinical trials."
NOTES FOR EDITORS:
About Prostate Cancer
Prostate cancer is the second leading cause of cancer death in men in industrialized societies, accounting for around 1 in 6 male cancer-related deaths. It is currently only exceeded by lung cancer but, with the ageing population, is expected to overtake lung cancer within the next ten years. According to the American Cancer Society, in 2004, 230,000 men in the United States will be diagnosed.
Current Treatment Options for Prostate Cancer
Current therapeutic options include surgery, radiation therapy, hormonal manipulation therapy or a combination of these. The approach to treatment is influenced by the patient's age and co-existing medical problems, though no agreed treatment pathway exists and treatment patterns vary in different countries. Several different hormonal approaches are available for prostate cancer including bilateral orchiectomy (surgical removal of the testicles), GnRH (gonadotrophin-releasing hormone) analogues and anti-androgens.
GnRH agonists versus blockers
Naturally occurring GnRH binds to the GnRH receptor on cells in the pituitary gland, triggering the production of luteinising hormone (LH), which subsequently stimulates the production of testosterone. Both GnRH agonists and blockers bind to this same receptor target.
Agonists work initially by stimulating release of LH and hence testosterone production, but blockers, like degarelix, directly prevent the release of LH, which means there is no surge in testosterone at the start of treatment leading to characteristic flare responses in symptoms and tumour growth. With blockers there is no need to administer a second hormonal agent, called an anti-androgen, normally used to combat the flare responses that accompany the GnRH agonist usage.
Degarelix is a synthetic peptide GnRH blocker, modeled on the body's own gonadotrophin-releasing hormone.
1. Weston PMT, Hammonds J, Vaughton et al. Degarelix; a novel GnRH antagonist tested in a multicenter, randomised dose-finding study in prostate cancer patients. 27th Congress of the Société Internationale d'Urologie, Hawaii, USA 3-7 October 2004. Podium presentation, 5 October.
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