Treatment of patients with advanced cancer of the prostate using a slow-release (depot) formulation of the LHRH agonist ICI 118630 (Zoladex)

Advances with androgen deprivation therapy for prostate cancer

INTRODUCTION

Androgen deprivation therapy (ADT) has been a treatment of choice for prostate cancer in almost all phases, particularly in the locally advanced, metastatic setting in both hormone-sensitive and castration-resistant diseaseand in those who are unfit for any local therapy. Different ways of administering ADT comes in the form of surgical or chemical castration with the use of gonadotropin-releasing hormone (GnRH-agonists) being the foremost way of delivering ADT.

AREAS COVERED

This review encompasses ADT history, use of leuprolide, degarelix, and relugolix, with contextual use of ADT in combination with androgen-signaling inhibitors and potential mechanisms of resistance. Novel approaches with regard to hormone therapy are also discussed.

EXPERT OPINION

The use of GnRH-agonists and GnRH-antagonists yields efficacy that is likely equivalent in resulting in testosterone suppression. While the side-effect profile with ADT are generally equivalent, effects on cardiovascular morbidity may be improved with the use of oral relugolix though this is noted with caution since the cardiovascular side-effects were a result of secondary subgroup analyses. The choice of ADT hinges upon cost, availability, ease of administration, and preference amongst physicians and patients alike.

Second-Generation Androgen Receptor Antagonists as Hormonal Therapeutics for Three Forms of Prostate Cancer

Enzalutamide is the first second-generation nonsteroidal androgen receptor (AR) antagonist with a strong binding affinity to AR. Most significantly, enzalutamide can prolong not only overall survival time and metastatic free survival time for patients with lethal castration-resistant prostate cancer (CRPC), but also castration-resistant free survival time for patients with castration-sensitive prostate cancer (CSPC). Enzalutamide has thus been approved by the US Food and Drug Administration (FDA) for the treatment of both metastatic (in 2012) and non-metastatic (in 2018) CRPC, as well as CSPC (2019). This is an inspiring drug discovery story created by an amazing interdisciplinary collaboration. Equally important, the successful clinical use of enzalutamide proves the notion that the second-generation AR antagonists can serve as hormonal therapeutics for three forms of advanced prostate cancer. This has been further verified by the recent FDA approval of the other two second-generation AR antagonists, apalutamide and darolutamide, for the treatment of prostate cancer. This review focuses on the rational design and discovery of these three second-generation AR antagonists, and then highlights their syntheses, clinical studies, and use. Strategies to overcome the resistance to the second-generation AR antagonists are also reviewed.

Agonists of luteinizing hormone-releasing hormone in prostate cancer

INTRODUCTION

Androgen deprivation therapy (ADT) has been the first-line standard of care for treating patients with hormone-sensitive advanced prostate cancer (PCa) for many decades. The agonists of luteinizing hormone-releasing hormone (LHRH), also called gonadotropin-releasing hormone, are still the most frequently used form of medical ADT.

AREAS COVERED

This article reviews the available data and most recent information concerning the use of LHRH agonists in advanced PCa. This article also reviews the discovery and development of LHRH agonists and summarizes the clinical evidence for their efficacy in PCa.

EXPERT OPINION

The introduction and application of agonists of LHRH has modernized and improved the treatment of advanced PCa. The life-saving benefits of LHRH agonists are well established, yet underestimated. Despite their efficacy, agonists of LHRH have several disadvantages or drawbacks including disease flare. The approach to ADT has been recently further refined with the development of the LHRH antagonist degarelix. Degarelix, a highly clinically effective third-generation LHRH antagonist, is currently available in most countries for therapy of advanced PCa. This new drug offers attractive alternatives to LHRH agonists for treatment of advanced PCa. A therapy for castration-resistant PCa based on a targeted cytotoxic analog of LHRH, AEZS-108, is also emerging.

Could bone tissue be a target for luteinizing hormone/chorionic gonadotropin?

Ovariectomy (OVX) and Zoladex administration to adult rats gave conflicting results with respect to the excretion of total urinary hydroxyproline (OH-Pro), a valuable indicator of bone collagen catabolism. Whereas OVX culminated in early (1 week) increases in OH-Pro, the use of Zoladex actually lowered OH-Pro and showed no sign of increasing over controls for a 2-month period. Since both OVX and Zoladex produce a state of estrogen deficiency we reasoned that the differential effects of the two procedures on OH-Pro were attributed to LH status. Receptors for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) have been identified in many, non-gonadal, estrogen sensitive sites and although bone is receptive to estrogen what effects LH/hCG might have upon bone metabolism have received scant attention. Treatment of osteoblasts in culture with a urinary derived formulation of hCG resulted in increased alkaline phosphatase (ALP) activity, raised matrix mettaloproteinase-2 (MMP-2) levels and increased expression of type I collagen. Further studies, using murine calvaria, supported a bone-resorbing effect of hCG. Taken together our initial findings suggested that raised hCG and/or LH might lead to an overall increase in bone matrix turnover as reported for puberty, pregnancy and the menopause. However, when the urinary derived preparation of hCG was replaced with recombinant hormone no changes in osteoblast activity were found implying the presence of contaminating agents in the urine derived hCG. Herein we describe that epidermal growth factor (EGF) could account for the changes observed for urinary derived hCG in osteoblast cultures and that the effects of LH/hCG on bone tissue are probably indirect.

Luteinizing hormone-releasing hormone agonists in the treatment of prostate cancer: A review of their discovery, development, and place in therapy

BACKGROUND

Early identification of the biological activity of luteinizing hormone-releasing hormone (LHRH) paved the way for the synthesis of analogues with enhanced potency and biological properties. Early testing in animal models and humans provided insight into the potential clinical uses of these substances, and, within 10 years, LHRH-agonist therapy had become available for use in patients with advanced prostate cancer (PC). Over time, the role of LHRH-agonist therapy has expanded to include use as part of multimodal treatment regimens throughout the course of the disease.

OBJECTIVES

This article reviews the discovery and development of LHRH agonists and summarizes the clinical evidence for their efficacy in PC.

METHODS

Relevant clinical studies were identified through searches of the English-language literature indexed on MEDLINE through May 2006. The main search terms were prostate cancer and LHRH agonist.

RESULTS

Results of the initial therapeutic trials of sustained-release depot formulations of LHRH agonists in patients with PC were reported in the mid-1980s, indicating that these agents were effective and well tolerated in improving clinical symptoms and producing medical castration. Longer-term studies and subsequent meta-analyses of randomized controlled trials in patients with advanced PC found no significant differences in overall survival when single-therapy androgen suppression was achieved through the use of LHRH-agonist therapy or orchiectomy. Randomized trials have reported significant improvements in disease-free and overall survival in patients with locally advanced or high-grade PC treated with LHRH agonists in addition to radiotherapy. Several prospective randomized trials have reported decreases in rates of positive surgical margins with short-term (6 weeks to 4 months) neoadjuvant LHRH-agonist therapy in patients with stage T1 to T3a PC undergoing prostatectomy. Definitive comparisons of immediate and delayed treatment in patients with biochemical relapse have not been reported. However, the results of several studies suggest that immediate LHRH-agonist therapy (or orchiectomy) may improve the course of disease progression and survival. The risks of long-term treatment (eg, osteoporosis; fracture; anabolic loss of muscle mass, with a tendency toward weight gain) must be considered carefully in patients who are likely to receive chronic LHRH-agonist therapy. Intermittent schedules have been developed to reduce the adverse effects associated with LHRH-agonist therapy; some reports support sparing effects on bone and muscle mass and relative improvements in toxicities during off-therapy periods, whereas others have documented continuing decreases in bone mineral density (BMD), with the rate of bone loss highest during the early cycles of therapy. Bisphosphonate therapy has been shown to increase BMD in patients with PC and may therefore be beneficial when overt symptoms of osteopenia or osteoporosis are present.

CONCLUSIONS

LHRH-agonist therapy has been the mainstay of treatment for advanced PC for >20 years. Clinical evidence supports expanding use of these agents at an earlier stage of disease and as part of multimodal regimens that include radiotherapy. There is a need for further study of the efficacy of adjuvant LHRH-agonist therapy along with prostatectomy, in patients with biochemical failure, in intermittent regimens, and in conjunction with cytotoxic therapies in late-stage disease.

Optimisation of treatment by applying programmable rate-controlled drug delivery technology

A number of programmable rate-controlled drug delivery technologies have been developed during the last two decades with the aim of regulating the rate of drug delivery, sustaining the duration of therapeutic action and/or targeting the delivery of drug to a specific tissue. As a result, several therapeutically beneficial outcomes can be achieved, such as: (i) controlled delivery of a therapeutic dose at a desirable rate of delivery; (ii) maintenance of drug concentrations within an optimal therapeutic range for prolonged duration of treatment; (iii) maximisation of efficacy-dose relationship; (iv) reduction of adverse effects; (v) minimisation of the need for frequent dose intake; and (vi) enhancement of patient compliance. The treatment of illness can thus be optimised. To gain a better understanding of how to optimise the treatment of illnesses by applying programmable rate-controlled drug delivery technologies, this article reviews the scientific concepts and technical principles behind the development of various programmable rate-controlled drug delivery systems that have been marketed or are under active development. Finally, the roles of these technologies in optimising therapeutic outcomes in nine therapeutic areas are discussed.

Enhancing initial release of peptide from poly(d,l-lactide-co-glycolide) (PLGA) microspheres by addition of a porosigen and increasing drug load

The objective of this study was to evaluate formulation variables such as drug load and addition of a porosigen in achieving an increased initial release of peptide from poly(d,l-lactide-co-glycolide) (PLGA) microspheres by altering carrier characteristics. Leuprolide acetate-loaded PLGA microspheres were prepared by a solvent-extraction-evaporation process and were characterized for their drug load (HPLC assay), bulk density (tapping method), size distribution (dynamic light scattering), specific surface area (Brunauer-Emmett-Teller [BET] analysis), surface morphology (scanning electron microscopy), in vitro drug release (at 37 degrees C), and in vivo efficacy (suppression of rat serum testosterone). Increasing the drug load, and adding various amounts of calcium chloride to organic and aqueous phases of the emulsion during processing yielded particles with increased porosity, lower bulk density, higher specific surface area, and accordingly higher initial release. In an animal model, these formulations showed a faster onset of testosterone suppression compared to microspheres without higher drug load or calcium chloride. The approaches employed in this study were found to be effective in avoiding the therapeutic lag phase usually observed with microencapsulated macromolecular drugs.

A short term (accelerated release) approach to evaluate peptide release from PLGA depot-formulations

An accelerated method to evaluate peptide release from poly(dl-lactide-co-glycolide) (PLGA) depot formulations in short time is described. Peptide-loaded microspheres were made from hydrophilic 50:50 PLGA by a dispersion-solvent extraction technique, and peptide release was studied at 37 degrees C and at higher temperatures in various media. For all accelerated conditions, release was faster at temperatures above the glass transition, Tg, of the host polymer. Complete release of peptide from 8600 MW PLGA was achieved in 35 hours at 50 degrees C in buffered and nonbuffered media containing 0.5% polyvinyl alcohol (PVA). Type of release media and concentration of PVA influenced the release profiles. A PVA concentration of 0.1 to 0.5% was found to prevent aggregation of microspheres at higher temperatures, with an increase in release at the higher PVA concentration. Peptide release was associated with a reduction of pH of the releasing media and increased mass loss. Complete peptide release at pH 4 from 8.6 kd and 28 kd PLGA at 50 and 60 degrees C occurred within 30-40 hours and correlated well with the real-time release at 37 degrees C and pH 7.0. At the higher molecular weight, a slightly longer accelerated release time and higher temperature were required to correlate with the real-time release. The data suggest that by optimization of release conditions such as temperature, surfactant concentration, buffer component, and pH, an accelerated study could be employed to evaluate depot formulations for a given polymer type.

Effects of long-term continuous GnRH administration on the pituitary–gonadal axis in Eld's deer stags (Cervus eldi thamin)

Eld's deer stags (Cervus eldi thamin) (in groups of three) were continuously administered gonadotropin-releasing hormone (GnRH) in control, low, medium, or high doses (0, 20.1 ± 0.7, 83.3 ± 2.6, and 292.9 ± 4.9 ng∙kg−1∙d−1, respectively) via osmotic minipumps for ~80 d to investigate the potential for precociously reactivating the pituitary–testicular axis during the nonbreeding season. Secretory patterns of LH, FSH, and testosterone concentrations were qualitatively similar among treatments. However, in the low-dose group, basal LH and FSH concentrations were both increased (p < 0.05) and pituitary responsiveness to a superimposed GnRH challenge was augmented (p < 0.05) after 12 weeks of treatment compared with all other groups. Despite these endocrine changes, continuous low-dose GnRH administration was not effective for precociously inducing testicular activity in this seasonally breeding species. High-dose GnRH administration initially induced a transient increase in LH, FSH, and testosterone secretion and delayed, but did not prevent, the seasonal decline in spermatogenesis. After 6–12 weeks of high-dose GnRH administration, however, attenuated pituitary responsiveness appeared to delay the normal seasonal reactivation of the pituitary–gonadal axis. In conclusion, prolonged, continuous low-dose GnRH administration did not effectively translate into a precocious onset of testicular activity; therefore, this specific approach is unlikely to be useful for prolonging the fertile period in this seasonally breeding species.

Is disease flare a problem?

When given for the first time to previously untreated patients with advanced prostate cancer, luteinizing hormone-releasing hormone (LHRH) analogs induce a transient rise in pituitary luteinizing hormone levels. As a consequence of this increase of LH, there is, within the first 2 to 3 days, a surge of testosterone, which can cause an exacerbation of the symptoms. First reports concerning this flare have been anecdotal, and in most studies, flare is reported with an incidence of 4-33%. This variance is due mainly to the confusion about the definition of the flare phenomenon. No distinctions have been made between clinical flare, with its manifestations of subjective or objective aggravation of cancer related symptoms, and the biochemical flare that results of the LHRH analog administration and that occurs in a majority of patients and is characterized by increases in testosterone, prostatic acid phosphatase, and prostate specific antigen. As the possible interference of the flare phenomenon on the ultimate aftermath of the patient's response to therapy is not yet known, it seems mandatory that flare prevention should be carried out whenever LHRH analogs are prescribed in monotherapy.

Combination treatment in M1 prostate cancer

The treatment of advanced prostate cancer is based on hormone manipulation to eliminate the trophic effect of testosterone on sensitive androgen tissue of the tumor. In this study, we evaluated the efficacy of the partial androgen blockage versus the complete androgen blockage. One hundred, twenty-two patients were entered in this study and randomly were treated with buserelin alone or with buserelin and flutamide. The group that received buserelin was given cyproterone acetate (200 mg/day) during first 3 weeks of treatment to avoid "flare-up". During the follow-up (range 0-244 +/- 1 weeks), we evaluated 59 patients (61.4%) that had positive response and 37 patients (38.6%) that showed progressive disease: There were no statistically significant differences between the two treatment groups, not even in the evaluation of median time to response and of median time to treatment failure. In conclusion, the results emphasize that total androgenic blockage is as effective as a luteinizing hormone-releasing hormone analog used alone.

Is there a best castration?

Androgen ablation by bilateral orchidectomy has long been considered the gold standard against which other forms of treatment for the management of advanced prostate cancer can be evaluated. It now is recognized that the use of luteinizing hormone-releasing hormone analogs provides a form of primary endocrine therapy that is as effective as surgical castration for the treatment of disseminated disease.

Pituitary hyperplasia after goserelin (LHRH-analogue) therapy

A 78-year-old male was treated with goserelin (Zoladex) for 16 months for metastasizing prostate carcinoma. This therapy is clinically equivalent to orchidectomy, as the application of the luteinizing hormone-releasing hormone (LHRH)-analogue Zoladex causes suppression of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) by down-regulation of pituitary receptors. Consequently, testicular androgen production is inhibited and testosterone levels are decreased to castration levels. In the present case we found diffuse, partially nodular hyperplasia of growth hormone (GH) and adrenocorticotropin (ACTH) producing cells in the anterior pituitary gland at autopsy. As Zoladex reduces pituitary receptors for releasing hormones (RH), a globally increased hypothalamic secretion of RH might be responsible for the ACTH- and the GH-cell hyperplasia. We cannot exclude that Zoladex may cause not only adenomas in rat pituitary glands as reported previously, but also a (nodular) hyperplasia of the pituitary gland in man.

Response to orchiectomy following Zoladex therapy for metastatic prostate carcinoma

Serum testosterone and prostate-specific antigen (PSA) levels were measured in 3 patients with Stage D2 prostate cancer before and after discontinuation of the long-acting LHRH agonist, goserelin acetate (Zoladex). The patients had received goserelin acetate for ten, sixteen, and thirty months prior to discontinuing the drug because of progressive metastatic disease. In all 3 patients, PSA and testosterone levels increased after goserelin acetate was discontinued. In 2 patients the testosterone level reached normal levels. A bilateral orchiectomy was performed one hundred sixty, one hundred, and seven days, respectively, after the drug was discontinued. In all 3 cases PSA and testosterone levels were reduced following castration, although PSA levels again began to increase within two weeks of orchiectomy in 2 of the 3 patients. These findings suggest that suppression of testosterone by LHRH agonists is not permanent and if tumor progression occurs, maintaining hormone suppression may still be beneficial.

Influence of different types of antiandrogens on luteinizing hormone-releasing hormone analogue-induced testosterone surge in patients with metastatic carcinoma of the prostate

The long-term effect of the luteinizing hormone-releasing hormone analogue-induced initial testosterone surge in the treatment of patients with metastatic carcinoma of the prostate still is unknown. However, acute worsening of the disease has been reported in up to 10% of the patients. To prevent such tumor flare we investigated the endocrinological effects of different types of antiandrogens administered in addition to a luteinizing hormone-releasing hormone analogue. Patients with newly diagnosed metastatic prostate cancer were pre-treated with either the steroidal antiandrogen cyproterone acetate (6) or the nonsteroidal antiandrogen flutamide (5) for 1 week before the initial injection of the depot luteinizing hormone-releasing hormone analogue Zoladex. In another 5 patients flutamide was first given 24 hours before Zoladex therapy was started. Luteinizing hormone, testosterone and prostatic acid phosphatase during month 1 of luteinizing hormone-releasing hormone analogue therapy were compared to data obtained in 5 patients treated by Zoladex alone. Only pre-treatment with cyproterone acetate was capable of preventing the Zoladex-induced testosterone surge. However, both pre-treatment regimens with either cyproterone acetate or flutamide for 1 week prevented an initial increase in prostatic acid phosphatase beyond pre-treatment levels in all patients. In contrast, in 4 of 5 patients treated with Zoladex alone and in 2 of 5 pre-treated with flutamide for 1 day an initial increase in prostatic acid phosphatase beyond the pre-treatment values was seen. Our data indicate that pre-treatment with flutamide for only 1 day may not be sufficient to prevent a luteinizing hormone-releasing hormone analogue-induced tumor flare in all cases.

Secondary treatment of advanced cancer of the prostate with Zoladex

Twelve patients with advanced prostatic carcinoma and relapse following previous hormone manipulation therapy were treated with Zoladex-depot every 4 weeks. The treatment was well tolerated and the endocrine response was satisfactory. However, no clinically important improvement was obtained.

The role of endocrine therapy in prostatic cancer

When judged by randomized clinical trial, current endocrine therapies offer symptomatic relief to prostatic cancer patients for an average period of 1-2 years following initiation of therapy. Medical castration with LHRH analogues is a safe and effective way of achieving 'castrate' levels of circulating androgens without the undesirable aspects of surgery. While there is some evidence for the value of combined therapies using these agents in combination with anti-androgens for 'total androgen blockade' in some patients, overall this approach has not been shown to offer advantages over castration, either surgical or medical, alone in controlled trials. Secondary endocrine therapy does not offer convincing objective response rates, suggesting that disease progression is independent of androgens.

Suppression of plasma androgens by the antiandrogen flutamide in prostatic cancer patients treated with Zoladex, a GnRH analogue

Chronic treatment with the GnRH (gonadotrophin hormone releasing hormone) agonist Zoladex causes suppression of testicular androgens. Use of antiandrogens has been advocated to block the effects of the initial surge of androgens, and to block any presumed effects of adrenal androgens. We have measured plasma concentrations of androgens and possible precursors before and during treatment in the following prostate cancer patients: 10 who received Zoladex alone (Z), nine who received Zoladex + the anti-androgen flutamide (Z + F) and five who were orchidectomized (O). Testosterone fell in the Z + F group to 0.84 +/- 0.21 nmol/l (mean +/- SD) significantly lower (Wilcoxon P less than 0.05) than after Z (1.58 +/- 1.84 nmol/l) alone. Progesterone and 17 alpha-hydryxyprogesterone did not change significantly in any group. Androstenedione and dehydroepiandrosterone sulphate (DHAS) showed significant falls in Z + F (from 3.44 +/- 0.34 to 1.92 +/- 0.18 mumol/l and from 3.88 +/- 0.64 to 1.92 +/- 0.36 mumol/l respectively) but not in other groups. These results are consistent with our demonstration of an inhibitory effect of flutamide, hydroxyflutamide and other antiandrogens on human adrenal microsomal 17 alpha-hydroxylase and 17,20-lyase activities in vitro.

Inhibition of the pituitary-gonadal axis by a single intramuscular administration of D-Trp-6-LH-RH (decapeptyl) in a sustained-release formulation in patients with prostatic carcinoma

For the past 6 years we used daily injection of luteinizing hormone-releasing hormone (LH-RH) agonists to treat patients with advanced prostate carcinoma. In this study we determined the hormonal response of the pituitary-testicular axis over a 2-month period and evaluated the safety and tolerance of the single intramuscular administration of sustained-release formulations of D-Trp-6-LH-RH microcapsules designed to release 50, 100, or 200 micrograms/day for over 1 month. Serum levels of LH, testosterone, and D-Trp-6-LH-RH were measured by RIA for up to 60 days in 10 patients with advanced prostatic carcinoma who had not received any previous drug therapy. After the administration of the microcapsules there was a biphasic increase in D-Trp-6-LH-RH serum levels. The maximal peak was obtained between 1 and 3 hr, and a second peak occurred between weeks 4 and 6. LH levels increased initially, with a maximal peak at 60 min, and elevated serum LH values persisted for more than 24 hr. LH levels began to fall on the second day, reaching subnormal values after 1 week. Serum testosterone rose during the first week and fell subsequently to less than 100 ng/dl. A rebound in LH and testosterone was seen about the 50th day after the microcapsule administration. Following the first week of therapy, we observed in all patients a significant decrease in bone pain, improvement in urinary flow obstruction, and a reversal of the signs of prostatism. No side effects were observed, and acceptance of the microcapsules was very good. Our results show that a single dose of D-Trp-6-LH-RH microcapsules suppresses of the pituitary-testicular axis for at least 50 days. D-Trp-6-LH-RH microcapsules facilitate the treatment and should lead to an improvement in the therapeutic response.

Effects of long term GnRH analogue treatment on hormone levels and spermatogenesis in patients with carcinoma of the prostate

The effects of long term GnRH treatment with the biodegradable depot formulation of ICI 118.630 on hormone levels and spermatogenesis were investigated in 18 males with advanced prostate cancer. Plasma levels of FSH, LH, testosterone, DHEA-S and SHBG were monitored at regular intervals. The drug suppressed FSH, LH and testosterone significantly and did not affect DHEA-S and SHBG plasma levels. Tissue specimens for histologic assessment and quantitative analysis of germinal cell types were obtained at secondary orchidectomy in 16 patients immediately following GnRH analogue treatment. Germinal cell maturation was arrested at the spermatogonial stage. In two patients discontinuing treatment histologic assessment of secondary orchidectomy specimens 9 and 10 months after the last GnRH analogue depot injection resulted in germinal cell maturation to late spermatids in part of the tubule cross sections. These results indicate that long term administration of the GnRH analogue fails to produce complete testicular sclerosis and spermatogenic arrest might be reversible.

Gonadotropin-releasing hormone analogs and prostatic cancer

Analogs of GnRH constitute a new category of drugs available for the treatment of advanced prostatic cancer. The efficacy and safety of GnRH analogs in the treatment of this disease is now well established. These compounds represent an important alternative therapy for advanced prostatic cancer patients who do not wish to undergo orchiectomy or for whom DES is not tolerable because of the risk of cardiovascular complications. The advent of the monthly depot form of these drugs will make treatment more convenient and less invasive and will enhance patient compliance.

Endocrinologic and clinical evaluation following a single administration of a gonadotrophin-releasing hormone agonist (Zoladex), in a depot formulation, to premenopausal women

A single 3.6-mg Zoladex subcutaneous depot injection was effective in suppressing the pituitary-ovarian function for about 5 weeks in nine regularly menstruating, premenopausal volunteers. Menses returned approximately 9 weeks after the injection. Zoladex depot is a novel approach in the administration of GnRH agonists and offers great therapeutic potential.

Phase II study of Zoladex depot in advanced prostatic cancer with special reference to criteria of response and survival

Zoladex is a potent decapeptide analogue of luteinising hormone releasing hormone (LHRH). The drug is formulated as a 3.6 mg depot dispersed in a matrix of d,l-lactide-glycolide copolymer, which is totally biodegradable. This formula releases drug continuously for at least 28 days and reliably suppresses serum testosterone into the castrate range. The effect of the depot was studied in 29 patients with locally advanced or metastatic carcinoma of the prostate. Average age at entry was 71 years (range 52-87) and follow-up was from 13.5 to 34.5 months (median 23). Endocrine studies showed that medical castration was maintained in all cases. Three patients experienced bone pain in the first month of treatment and two others had temporary nephrostomies for worsening ureteric obstruction. Subjective improvement was seen in 23/28 cases (82%). There were no complete responses, but partial response was seen in 24/28 (85.7%) using our own criteria, 24/28 (85.7%) using the criteria recommended by the British Prostate Group (BPG) and 15/28 (53.6%) using NPCP criteria. Stable disease was seen in 3/28 patients (10.7%) by our own or BPG criteria, and in 12/28 patients (42.9%) according to NPCP criteria. Progression of disease was measurable in 21 patients (72.4%) whatever criteria were applied; 11/29 (37.9%) have died, giving a median survival of 10 months (range 2.4-26). Following these encouraging results, a multicentre randomised comparative study with stilboestrol 3 mg daily is being undertaken.

The treatment of metastatic prostatic cancer with the slow release LH-RH analogue Zoladex ICI 118630

The clinical and endocrine response to a depot preparation of the LH-RH analogue ICI 118630 (Zoladex) was assessed in 55 untreated patients with advanced prostatic cancer. Whereas gonadal androgen suppression was achieved in all patients, subjective and objective clinical response occurred in only 69%, indicated by a relief of bone pain, a decrease in the size of the primary tumour and lymph node metastases and improvement in bone scan appearances. A third of these patients, however, subsequently showed progression of their disease. Serious side effects were not encountered in this study. The depot formulation is a simple, safe and convenient method of administering Zoladex and offers an alternative treatment for metastatic prostatic cancer.

Clinical applications of LHRH analogues

What is the current state of clinical application of inhibition of gonadal activity with LHRH agonists or antagonists? It seems unlikely in the short term that antagonists will be widely applied due to the short-acting nature of the present compounds and their troublesome side-effects. In contrast clinical studies with a number of agonists have demonstrated their efficacy in producing a hypogonadal state safely with rapid recovery following cessation of therapy. Although nasal administration may be suitable for short-term suppression (up to 28 days) it seems likely that long-acting depot preparations will be useful for more prolonged suppression. Perhaps the easiest application to determine will be the profound suppression required to produce medical castration in hormone-dependent tumours. The combination of agonist and receptor blocker is attractive particularly when the receptor blocker like cyproterone acetate also suppresses the release of LH, FSH and adrenocorticotrophic hormone. In cancer of the prostate and breast the side-effects due to inhibition of secretion of testosterone and oestradiol are tolerable although the only benefit over castration is the avoidance of minor surgery. The agonists should improve significantly the existing treatment for precocious puberty, endometriosis, uterine fibroids, polycystic ovary syndrome (PCO) and induction of ovulation although large scale trials comparing different therapies and doses are required. Finally, the concept of combination therapies to block further the influence of steroid hormones suggests challenging possibilities for even more effective therapy.

Treatment of patients with advanced cancer of the prostate: phase III trial, zoladex against castration; a study of the British Prostate Group

The interim results of the randomised, Phase III trial of Zoladex against castration in the management of patients with metastatic carcinoma of the prostate is discussed. Trials commenced in October 1984 and incorporated 359 patients when recruitment ceased in January 1986. The preliminary report concerns the first 240 patients who had a minimum of 3 months follow-up. Entry criteria included patients who had no previous treatment with the exception of first-line localised radiotherapy and those who had distant bone or soft tissue metastases. Fourteen patients were excluded on the basis of protocol violations. The objective assessment of response was based on the British Prostate Group Criteria and was performed monthly for the first 3 months and 3-monthly thereafter. Pre-treatment disease characteristics of patients in both groups were similar at entry and there were no significant differences in the subjective response data of patients between the orchidectomy (n = 106) and the Zoladex group (n = 120). Objective response rates at 12 and 24 weeks of treatment were also identical for both treatment groups. Serum testosterone concentrations were below the 'castrate' level (less than 2 nmol/L) for Zoladex group as well as the orchidectomy group up to 48 weeks. The drug was well-tolerated with minimal side effects, those resulting from testosterone withdrawal were similar in both groups. The report therefore indicates clearly that this partical formulation of LH-RH analogue provides a valuable alternative to the surgical procedure in the treatment of carcinoma of the prostate.

Pharmacokinetic and endocrinological parameters of a slow-release depot preparation of the GnRH analogue ICI 118630 (zoladex) compared with a subcutaneous bolus and continuous subcutaneous infusion of the same drug in patients with prostatic cancer

Seventeen patients with advanced prostatic cancer were treated with the gonadotrophin-releasing hormone analogue DSer (tBU)6 AzaGly 10 GnRH (ICI 118630), either as a constant SC infusion, or in the form of a monthly SC slowrelease depot formulation, in which case patients were randomised to receive one of three doses. Six of these patients also received a 250-microgram SC bolus of ICI 118630, for pharmacokinetic studies, before starting the infusion or the depot. Drug levels were measured using a double-antibody radioimmunoassay. In contrast to the SC infusion, which gave a smooth serum 118630 level profile, drug release from the depot preparation was not constant, levels varying in a predictable manner throughout each 28-day period, reaching a peak proportional to the dose of ICI 118630 received, between days 15 and 18 of each cycle. With all methods of administration there was an initial rise in LH, usually followed by a rise in testosterone, after which the SC infusion and the depot were both effective in reducing serum LH to basal levels and testosterone into the castrate range within 1 month. It is too early to make any assessment of clinical response; however, depot treatment was well tolerated: Four patients experienced an initial flare in bone pain, probably related to the initial rise in testosterone, and twelve patients experienced flushing; one patient with pre-existing hydronephrosis and hydroureter developed renal failure, possibly related to a tumour flare reaction. No patients have experienced cardiovascular side effects or local reaction.

Failure of high-dose sustained release luteinizing hormone releasing hormone agonist (buserelin) plus oral testosterone to suppress male fertility

Previously we have demonstrated that sperm counts of normal young men decreased during constant subcutaneous infusion of the LHRH agonist buserelin (118 or 230 micrograms/d). In order to test whether azoospermia can be achieved with higher doses, seven young men received 450 micrograms buserelin subcutaneously daily for 12 weeks via extracorporeal osmotic minipumps. To avoid symptoms of androgen deficiency, oral supplementation with 80 mg/d testosterone undecanoate (TU) was initiated in week 5 and was increased to 120 mg/d by week 8. Follow-up after treatment lasted for another 12 weeks. In order to evaluate possible psychotropic effects of treatment-related endocrine changes, continuous psychometric testing was performed focusing on personality, emotions and sexuality. After an initial rise, both serum LH and FSH returned to normal. FSH was below normal during the 3rd-5th week following treatment. LHRH stimulation tests performed at the end of treatment showed pituitary desensitization. Serum T (always measured between 0800 and 1300 h at least 12 h after last TU) tended to decrease by week 7 and remained slightly depressed until the end of treatment while libido, potency and emotional well-being remained unchanged. While testicular volumes showed a reduction from week 7 of treatment to week 10 post-treatment, sperm counts decreased only insignificantly from 65 +/- 10 to 44 +/- 14 million per ml in week 12 post-treatment. Severe oligo- or azoospermia was not observed in any of the seven men. It is concluded that full androgen substitution by TU can drastically delay if not abolish the antifertility effect of LHRH-induced pituitary desensitization.

A prognostic index for the clinical management of patients with advanced prostatic cancer: a British Prostate Study Group investigation

Patients with histologically proven carcinoma of the prostate (n = 186) were initially assessed and followed up according to the standardized protocol of the British Prostate Study Group, urologists from which contributed patients to this investigation. These patients were given either endocrine therapy or orchidectomy as first line treatment; the ratio of the number of patients receiving these two treatments was similar in each group of subjects compared for survival. Prognostic indices were derived for all patients and for those classified according to the presence (M1) or absence (M0) of metastases. The prognostic indices were derived from clinical and hormone data obtained at initial presentation. Whereas the degree of tumor differentiation and plasma testosterone concentrations were significant prognostic factors in both M0 and M1 disease, growth hormone was only significant in M1 patients, where age was also of borderline significance; elevated growth hormone, higher Gleason grade, younger age, and lower testosterone indicated a poorer prognosis in M1 patients. These findings indicated the feasibility of selecting a poor prognostic group of patients that may derive benefit from a more aggressive therapy.

Investigation of the combination of the agonist D-Trp-6-LH-RH and the antiandrogen flutamide in the treatment of Dunning R-3327H prostate cancer model

The therapy for the treatment of prostate cancer and other sex-steroid-dependent tumors based on agonists of LH-RH has been made more practical and efficacious by the development of a long-acting formulation of microcapsules of D-Trp-6-LH-RH for controlled release. Antiandrogens, which neutralize the effect of endogenous androgens, have been used also in the management of prostate cancer in man. The effects of a simultaneous administration of the antiandrogen flutamide and microcapsules of the agonist D-Trp-6-LH-RH were studied in the Dunning R-3327H rat prostate adenocarcinoma model to determine whether the combination of these two drugs might inhibit tumor growth more effectively than single agents. Microcapsules of D-Trp-6-LH-RH, calculated to release a controlled dose of 25 micrograms/day for a period of 30 days were injected intramuscularly once a month. Flutamide was administered SC at a daily dose of 25 mg/kg. The therapy was started 100 days after the tumor transplantation and continued for 60 days. Tumor weights and volumes were significantly reduced in rats treated with microcapsules or flutamide alone, but the former drug inhibited tumor growth more than the latter. The combined treatment of flutamide and microcapsules significantly decreased tumor weight and volume, but did not exert a synergistic effect on tumor growth, the reduction being smaller for the combination than for the microcapsules alone. There was a significant elevation of serum testosterone, LH, and prolactin in rats treated with flutamide. On the other hand, in rats given microcapsules of D-Trp-6-LH-RH, testosterone fell to castration levels within 7 days and remained at nondetectable values, serum LH and prolactin levels being also suppressed in this group. The combined administration of microcapsules and flutamide also significantly decreased serum testosterone to nondetectable levels by day 7 and suppressed serum LH and prolactin. Our findings raise doubts of whether the daily administration of the combination of LH-RH agonist with an antiandrogen offers an advantage over the use of microcapsules of an agonist like D-Trp-6-LH-RH alone in the treatment of prostatic carcinoma.