Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2022 Publisher: Takeda UK Limited, 1 Kingdom Street, London, W2 6BD, United Kingdom
Pharmacotherapeutic group: Gonadotrophin-Releasing Hormone Analogues
ATC code: L02AE02
PROSTAP 3 contains leuprorelin acetate, a synthetic nonapeptide analogue of naturally occurring gonadotrophin releasing hormone (GnRH) which possesses greater potency than the natural hormone. Leuprorelin acetate is a peptide and therefore unrelated to the steroids. Chronic administration results in an inhibition of gonadotrophin production and subsequent suppression of ovarian and testicular steroid secretion. This effect is reversible on discontinuation of therapy.
Administration of leuprorelin acetate results in an initial increase in circulating levels of gonadotrophins which leads to a transient increase in gonadal steroid levels in both men and women. Continued administration of leuprorelin acetate results in a decrease of gonadotrophin and sex steroid levels. In men serum testosterone levels, initially raised in response to early luteinising hormone (LH) release, fall to castrate levels in about 2-4 weeks.
Leuprorelin acetate is inactive when given orally.
A randomised, open-label, comparative multi-centre study was performed to compare the efficacy and safety of the 3.75 mg and 11.25 mg depots of leuprorelin acetate. 48% of patients included had locally advanced disease (T3N0M0), 52% of patients had metastatic disease. Mean serum testosterone level fell below the threshold for chemical castration (0.5 ng/ml) at one month of treatment, continuing to decrease thereafter and stabilising at a value below the castration threshold. The decline in serum PSA mirrored that of serum testosterone in both groups.
In an open, prospective clinical trial involving 205 patients receiving 3.75 mg leuprorelin acetate on a monthly basis as treatment for metastatic prostate cancer, the long-term efficacy and safety of leuprorelin acetate was assessed. Testosterone levels were maintained below the castrate threshold over the 63-month follow up period. Median survival time exceeded 42.5 months for those receiving monotherapy and 30.9 months for those receiving leuprorelin acetate in combination with anti-androgens (this difference relating to baseline differences between groups)
In a meta-analysis involving primarily patients with metastatic disease, no statistically significant difference in survival was found for patients treated with LHRH analogues compared with patients treated with orchidectomy.
In another randomised, open-label, multi-centre comparative trial, leuprorelin acetate in combination with flutamide has been shown to significantly improve disease-free survival and overall survival when used as an adjuvant therapy to radiotherapy in 88 patients with high-risk localised (T1-T2 and PSA of at least 10 ng/mL or a Gleason score of at least 7), or locally advanced (T3-T4) prostate cancer. The optimum duration of adjuvant therapy has not been established. This US study used a higher dose of leuprorelin acetate (7.5 mg/month) which is therapeutically equivalent to the European licensed dose.
The use of a LHRH agonist may be considered after prostatectomy in selected patients considered at high risk of disease progression. There are no disease-free survival data or survival data with leuprorelin acetate in this setting.
Neoadjuvant leuprorelin acetate prior to radiotherapy has been shown to reduce prostate volume.
There are no data demonstrating effectiveness of the 3-monthly formulation of leuprorelin for ovarian function preservation in premenopausal women undergoing chemotherapy treatment.
Reversible suppression of pituitary gonadotropin release occurs, with a subsequent decrease in oestradiol (E2) or testosterone levels to values in the pre-pubertal range.
Initial gonadal stimulation (flare-up) may cause vaginal bleeding in girls who are already post-menarchal at start of treatment. Withdrawal bleeding may occur at the start of treatment. The bleeding normally stops as treatment continues.
The following therapeutic effects can be demonstrated:
Treatment result is the suppression of the pathologically, prematurely activated hypothalamic-pituitary-gonadal axis according to pre-pubertal age.
In a long-term clinical trial in children treated with leuprorelin at doses up to 15mg monthly for >4 years resumption of pubertal progression were observed after cessation of treatment. Follow up of 20 female subjects to adulthood showed normal menstrual cycles in 80% and 12 pregnancies in 7 of the 20 subjects including multiple pregnancies for 4 subjects.
Leuprorelin acetate is well absorbed after subcutaneous and intramuscular injections. It binds to the LHRH receptors and is rapidly degraded. An initially high plasma level of leuprorelin acetate peaks at around 3 hours after a PROSTAP 3 subcutaneous injection, followed by a decrease to maintenance levels in 7 to 14 days. PROSTAP 3 provides continuous plasma levels for up to 117 days resulting in suppression of testosterone to below castration level within 4 weeks of the first injection in the majority of patients.
The metabolism, distribution and excretion of leuprorelin acetate in humans have not been fully determined.
Figure 1 presents the leuprorelin serum levels in children during the first 6 months of treatment following s.c. administration of leuprorelin acetate 3-month depot (two injections).
From the first injection, the leuprorelin serum levels increase reaching maximal serum levels at month 4 (294.79 pg/ml ± 105.42) and slightly decrease until month 6 (229.02 pg/ml ± 103.33).
Figure 1. Leuprorelin serum levels during the first six months of treatment with the leuprorelin acetate 3-month depot formulation (two s.c. injections) (n=42-43):
Animal studies have shown that leuprorelin acetate has a high acute safety factor. No major overt toxicological problems have been seen during repeated administration. Whilst the development of pituitary adenomas has been noted in chronic toxicity studies at high doses in some animal species, this has not been observed in long-term clinical studies. No evidence of mutagenicity has been shown. Animal reproductive studies showed increased foetal mortality and decreased foetal weights reflecting the pharmacological effects of this GnRH agonist. An increased frequency of malformations was also observed in rabbits but not rats.
© All content on this website, including data entry, data processing, decision support tools, "RxReasoner" logo and graphics, is the intellectual property of RxReasoner and is protected by copyright laws. Unauthorized reproduction or distribution of any part of this content without explicit written permission from RxReasoner is strictly prohibited. Any third-party content used on this site is acknowledged and utilized under fair use principles.
