Cyproterone acetate--mechanism of action and clinical effectiveness in prostate cancer treatment

Regulation of HNRNP family by post-translational modifications in cancer

Heterogeneous nuclear ribonucleoproteins (HNRNPs) represent a large family of RNA-binding proteins consisting of more than 20 members and have attracted great attention with their distinctive roles in cancer progression by regulating RNA splicing, transcription, and translation. Nevertheless, the cancer-specific modulation of HNRNPs has not been fully elucidated. The research of LC-MS/MS technology has documented that HNRNPs were widely and significantly targeted by different post-translational modifications (PTMs), which have emerged as core regulators in shaping protein functions and are involved in multiple physiological processes. Accumulating studies have highlighted that several PTMs are involved in the mechanisms of HNRNPs regulation in cancer and may be suitable therapeutic targets. In this review, we summarize the existing evidence describing how PTMs modulate HNRNPs functions on gene regulation and the involvement of their dysregulation in cancer, which will help shed insights on their clinical impacts as well as possible therapeutic tools targeting PTMs on HNRNPs.

Discovery of (2S)-N-(6-Cyano-5-(trifluoromethyl)pyridin-3-yl)-3-(6-(4-cyanophenyl)-3,6-diazabicyclo[3.1.1]heptan-3-yl)-2-hydroxy-2-methylpropanamide as a Highly Potent and Selective Topical Androgen Receptor Antagonist for Androgenetic Alopecia Treatment

Androgenetic alopecia (AGA) is the most prevalent form of progressive hair loss disorder in both men and women, significantly impacting their appearance and overall quality of life. Overactivation of the AR signaling pathway in dermal papilla cells (DPCs) plays a crucial role in the development and progression of AGA. Considering the severe systemic side effects associated with oral AR antagonists, the idea of developing of topical AR antagonists with rapid metabolic deactivation properties emerged as a promising approach. Herein, through systematic structural optimization, we successfully identified compound 30a as a potent and selective AR antagonist with favorable pharmacokinetic properties, resulting in high skin exposure and low plasma exposure following topical administration. Importantly, in both hair-growth and AGA mouse models, compound 30a showed potent hair-growth-promoting effects without any noticeable toxicity. These findings suggest that compound 30a holds significant potential as a topical AR antagonist for treating AGA patients.

The effect of short-term use of finasteride versus cyproterone acetate on perioperative blood loss with monopolar transurethral resection of prostate

Background

Perioperative bleeding is the most common complication related to transurethral resection of prostate; the aim of the study was to compare the effect of pre-operative use of finasteride versus cyproterone acetate (CPA) on blood loss with monopolar TURP.

Methods

This prospective randomized controlled study was conducted on (60) patients with BPH underwent monopolar TURP between July 2019 and July 2020. Patients were distributed into three equal groups; CPA group: 20 patients received cyproterone acetate 50 mg tab BID for two weeks before TURP, finasteride group: 20 patients received single daily dose of finasteride 5 mg for two weeks before TURP, control group: 20 patients received no treatment before TURP, all patients underwent monopolar TURP, and then histopathological examination of the resected tissues was done with assessment of the microvascular density of the prostate.

Results

Our study showed that there was significant decrease in intraoperative blood loss and operative time in CPA and finasteride groups in comparison with control group (p = 0.0012) (p < 0.0001), respectively, significant decrease in post-operative Hb and HCT value in finasteride and control groups in comparison with CPA group (p < 0.01), significant increase in specimen weight in CPA group compared to other groups (p < 0.01), and there was also significant decrease in microvascular density in CPA group in comparison with other groups (p < 0.01).

Conclusion

Cyproterone acetate is more effective than finasteride in decreasing perioperative bleeding with TURP by decreasing microvascular density of the prostate.

Targeting steroid hormone receptors for anti-cancer therapy-A review on small molecules and nanotherapeutic approaches

The steroid hormone receptors (SHRs) among nuclear hormone receptors (NHRs) are steroid ligand-dependent transcription factors that play important roles in the regulation of transcription of genes promoted via hormone responsive elements in our genome. Aberrant expression patterns and context-specific regulation of these receptors in cancer, have been routinely reported by multiple research groups. These gave an window of opportunity to target those receptors in the context of developing novel, targeted anticancer therapeutics. Besides the development of a plethora of SHR-targeting synthetic ligands and the availability of their natural, hormonal ligands, development of many SHR-targeted, anticancer nano-delivery systems and theranostics, especially based on small molecules, have been reported. It is intriguing to realize that these cytoplasmic receptors have become a hot target for cancer selective delivery. This is in spite of the fact that these receptors do not fall in the category of conventional, targetable cell surface bound or transmembrane receptors that enjoy over-expression status. Glucocorticoid receptor (GR) is one such exciting SHR that in spite of it being expressed ubiquitously in all cells, we discovered it to behave differently in cancer cells, thus making it a truly druggable target for treating cancer. This review selectively accumulates the knowledge generated in the field of SHR-targeting as a major focus for cancer treatment with various anticancer small molecules and nanotherapeutics on progesterone receptor, mineralocorticoid receptor, and androgen receptor while selectively emphasizing on GR and estrogen receptor. This review also briefly highlights lipid-modification strategy to convert ligands into SHR-targeted cancer nanotherapeutics. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Lipid-Based Structures Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Combined oral contraceptives promote androgen receptor and oestrogen receptor alpha upregulation in the female prostate (Skene’s paraurethral glands) of adult gerbils (Meriones unguiculatus)

The aim of this study was to evaluate the effects of cyproterone acetate (CPA) and ethinyloestradiol (EE) alone or in combination on the female prostate of adult gerbils. Adult females were exposed for 21 days to daily oral doses of CPA (1 mg kg−1), EE (10 µg kg−1) or a combination of CPA and EE. Female prostatic complexes were removed, weighed and subjected to morphological, stereological, immunohistochemical and ultrastructural analyses. CPA treatment caused epithelial atrophy and decreased prostate secretory activity. The EE treatment group showed glandular hyperplasia, a high cell-proliferation index and an increase in androgen and oestrogen receptor α (AR and ERα) immunoreactivity. Combined treatment (CPA+EE) caused adverse effects, such as an increase in cell proliferation, higher AR and ERα immunoreactivity, prostatic intraepithelial neoplasia, cell degeneration and aging. In conclusion, the CPA-only treatment promoted antiandrogenic effects on the female gerbil prostate, whereas EE-only had a potent oestrogenic activity. However, when combined, EE overlapped the effects of CPA, changing the pattern of glandular hormonal regulation and stimulating the development of prostatic lesions in female gerbils.

Therapeutic Rationales, Progresses, Failures, and Future Directions for Advanced Prostate Cancer

Patients with localized prostate cancer (PCa) have several therapeutic options with good prognosis. However, survival of patients with high-risk, advanced PCa is significantly less than patients with early-stage, organ-confined disease. Testosterone and other androgens have been directly linked to PCa progression since 1941. In this review, we chronicle the discoveries that led to modern therapeutic strategies for PCa. Specifically highlighted is the biology of androgen receptor (AR), the nuclear receptor transcription factor largely responsible for androgen-stimulated and castrate-recurrent (CR) PCa. Current PCa treatment paradigms can be classified into three distinct but interrelated categories: targeting AR at pre-receptor, receptor, or post-receptor signaling. The continuing challenge of disease relapse as CR and/or metastatic tumors, destined to occur within three years of the initial treatment, is also discussed. We conclude that the success of PCa therapies in the future depends on targeting molecular mechanisms underlying tumor recurrence that still may affect AR at pre-receptor, receptor, and post-receptor levels.

Cyproterone acetate induces a wide spectrum of acute liver damage including corticosteroid-responsive hepatitis: report of 22 cases

BACKGROUND & AIMS

Cyproterone acetate (CPA), an anti-androgenic drug for prostate cancer, has been associated with drug-induced liver injury (DILI). We aim to expand the knowledge on the spectrum of phenotypes and outcomes of CPA-induced DILI.

METHODS

Twenty-two males (70 ± 8 years; range 54-83) developing liver damage as a result of CPA therapy (dose: 150 ± 50 mg/day; range 50-200) were included. Severity index and causality by RUCAM were assessed.

RESULTS

From 1993 to 2013, 22 patients were retrieved. Latency was 163 ± 97 days. Most patients were symptomatic, showing hepatocellular injury (91%) and jaundice. Liver tests at onset were: ALT 18 ± 13 × ULN, ALP 0.7 ± 0.7 × ULN and total serum bilirubin 14 ± 10 mg/dl. International normalized ratio values higher than 1.5 were observed in 14 (66%) patients. Severity was mild in 1 case (4%), moderate in 7 (32%), severe in 11 (50%) and fatal in 3 (14%). Five patients developed ascitis, and four encephalopathy. One patient had a liver injury that resembled autoimmune hepatitis. Eleven (50%) were hospitalized. Nineteen patients recovered after CPA withdrawal, although three required steroid therapy (two of them had high ANA titres). Liver biopsy was performed in seven patients (two hepatocellular collapse, one submassive necrosis, two cholestatic hepatitis, one cirrhosis with iron overload and one autoimmune hepatitis). RUCAM category was 'highly probable' in 19 (86%), 'probable' in 1 (4%), and 'possible' in 2 (9%).

CONCLUSIONS

CPA-induced liver injury is severe and can be fatal, and may occasionally resemble autoimmune DILI. The benefit/risk ratio of this drug should be thoroughly assessed in each patient.

Advances in the Treatment of Metastatic Prostate Cancer

During the past several years, there has been substantial progress in the development of treatments for advanced prostate cancer with the approval of multiple new life-prolonging agents using different mechanisms of action. Such progress was attainable because of advances in our understanding of the biology behind mechanisms of androgen receptor pathway activation, complex tumor-microenvironment interaction of bone metastasis, antitumor immunology, and new oncogenic pathways. Continuous efforts are being made to develop new therapeutics with novel mechanisms of action, define the optimal sequences and/or combinations of current agents, and identify reliable surrogate end points to facilitate new drug development.

Androgen receptor antagonists for prostate cancer therapy

Androgen deprivation is the mainstay therapy for metastatic prostate cancer (PCa). Another way of suppressing androgen receptor (AR) signaling is via AR antagonists or antiandrogens. Despite being frequently prescribed in clinical practice, there is conflicting evidence concerning the role of AR antagonists in the management of PCa. In the castration-resistant settings of PCa, docetaxel has been the only treatment option for decades. With recent evidence that castration-resistant PCa is far from AR-independent, there has been an increasing interest in developing new AR antagonists. This review gives a concise overview of the clinically available antiandrogens and the experimental AR antagonists that tackle androgen action with a different approach.

A novel steroidal antiandrogen targeting wild type and mutant androgen receptors

Prostate cancer (PCa) progression is enhanced by androgen and treatment with antiandrogens represents an alternative to castration. While patients initially respond favorably to androgen ablation therapy, most experience a relapse of the disease within 1-2 years by expressing androgen receptor (AR) mutants. Such mutations, indeed, promote unfavorable agonistic behavior from classical antagonists. Here, we have synthesized and screened 37 novel compounds derived from dihydrotestosterone (DHT), cyanolutamide and hydroxyflutamide. These derivatives were tested for their potential antagonistic activity using a luciferase reporter gene assay and binding properties were determined for wild type (WT) and mutant ARs (T877A, W741C, W741L, H874Y). In the absence and presence of antiandrogens, androgen dependent cellular proliferation and prostate specific antigen (PSA) expression were assayed in the prostate cancer cell line LNCaP by crystal violet, real time PCR and by Western blots. Also, cellular proliferation and PSA expression were assayed in 22Rv1. A novel compound RB346, derived from DHT, was found to be an antagonist for all tested AR forms, preventing DHT induced proliferation and PSA expression in LNCaP and 22Rv1 cells. RB346 displayed no agonistic activity, in contrast to the non-steroidal antiandrogen bicalutamide (Casodex) with unfavorable agonistic activity for W741L-AR. Additionally, RB346 has a slightly higher binding affinity for WT-AR, T877A-AR and H874Y-AR than bicalutamide. Thus, RB346 is the first potent steroidal antiandrogen with efficacy for WT and various AR mutants.

Endocrine therapy for prostate cancer

Endocrine therapy of prostate cancer has mostly been reserved to patients with advanced stages of the disease. The principle for endocrine treatment of prostate cancer is elimination of stimulatory effects of testicular androgens on the prostate tumour cells. This can be achieved by surgical removal of the testes, by inhibition of pituitary gonadotrohin secretion by GnRH-angonsists or antagonists, by oestrogens or by non-steroidal antiandrogens. Since non-steroidal antiandrogens have fewer side-effects than castrational therapies, there is an increased interest for using endocrine treatment as adjuvant therapy after localized treatment. At least in certain stages of the disease, early hormonal treatment may have survival benefits. The timing of endocrine therapy, the usage of combined androgen blockade and intermittent endocrine therapy will be discussed in this overview.

Why do winners keep winning? Androgen mediation of winner but not loser effects in cichlid fish

Animal conflicts are influenced by social experience such that a previous winning experience increases the probability of winning the next agonistic interaction, whereas a previous losing experience has the opposite effect. Since androgens respond to social interactions, increasing in winners and decreasing in losers, we hypothesized that socially induced transient changes in androgen levels could be a causal mediator of winner/loser effects. To test this hypothesis, we staged fights between dyads of size-matched males of the Mozambique tilapia (Oreochromis mossambicus). After the first contest, winners were treated with the anti-androgen cyproterone acetate and losers were supplemented with 11-ketotestosterone. Two hours after the end of the first fight, two contests were staged simultaneously between the winner of the first fight and a naive male and between the loser of first fight and another naive male. The majority (88%) of control winners also won the second interaction, whereas the majority of control losers (87%) lost their second fight, thus confirming the presence of winner/loser effects in this species. As predicted, the success of anti-androgen-treated winners in the second fight decreased significantly to chance levels (44%), but the success of androgenized losers (19%) did not show a significant increase. In summary, the treatment with anti-androgen blocks the winner effect, whereas androgen administration fails to reverse the loser effect, suggesting an involvement of androgens on the winner but not on the loser effect.

Hepatotoxicity induced by antiandrogens: a review of the literature

INTRODUCTION

Hepatotoxicity is a serious adverse reaction potentially induced by all antiandrogens. We have reviewed here the published cases of hepatotoxicity induced by steroidal and nonsteroidal antiandrogens, and compared the type and characteristics of liver damage.

METHODS

Using two different databases: MEDLINE and IDIS (Iowa Drug Information Service), we searched for published cases of liver injury induced by antiandrogens. Analysis was made of the type of hepatotoxicity, therapeutic indication, other pharmacological treatments and evolution. Mean values of latency and recovery periods of the adverse reactions and liver function tests were also evaluated.

RESULTS

Hepatitis was the most common type of hepatotoxicity reported, and was associated with all antiandrogens. This adverse reaction does not seem to be dependent on the patients age, therapeutic indication or the dose prescribed. Hepatitis showed a longer latency period for cyproterone acetate than for flutamide. Some transaminase levels were significantly higher for flutamide than for cyproterone acetate, although the evolution was no worse in the cases reported for flutamide. We also found occasional reports of hepatocellular carcinoma and hepatic cirrhosis suspected of being induced by cyproterone acetate.

CONCLUSION

Although there are differences in the clinical features of hepatotoxicity induced by steroidal and nonsteroidal antiandrogens, these do not predict which patients will develop hepatotoxicity during treatment or evolution. Serial liver function tests are required for early detection of liver damage.

Bicalutamide vs cyproterone acetate in preventing flare with LHRH analogue therapy for prostate cancer—a pilot study

OBJECTIVE

To evaluate the efficacy of bicalutamide vs cyproterone acetate in preventing PSA flare (as a surrogate for tumour flare) for patients requiring luteinizing hormone-releasing hormone (LHRH) analogue therapy for prostate cancer.

PATIENTS AND METHODS

In this pilot study, 40 men were randomized 1 : 1 to bicalutamide 50 mg o.d. or cyproterone acetate 100 mg t.i.d. 5 days prior to goserelin acetate and continued for 21 days thereafter. PSA, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone were obtained before treatment and on days 6, 8, 10, 16, 21 and 28. Primary end point was PSA. Hormone profile and clinical features including urinary symptoms and bone pain were secondary end points.

RESULTS

Both groups were equally matched apart from serum creatinine and ALP. The speed and magnitude of the percentage change in median PSA from baseline was increased for the CPA group but there was no statistically significant difference in the two groups. Although those receiving bicalutamide all showed a testosterone peak, this remained within the normal range. No difference in the frequency of drug-specific adverse events was found. None of the patients died or developed cord compression during the study period.

CONCLUSION

Bicalutamide is able to suppress the initial PSA surge as effectively as cyproterone acetate albeit slightly delayed. A statement whether bicalutamide is equally good at preventing clinical flare cannot be made and should be assessed in an appropriately powered study.

A direct beta-catenin-independent interaction between androgen receptor and T cell factor 4

T cell factor (Tcf) proteins bind beta-catenin and are downstream effectors of Wnt/beta-catenin signals. A recently demonstrated interaction between beta-catenin and the androgen receptor (AR) ligand binding domain has suggested that AR may be a Tcf-independent Wnt/beta-catenin effector. This study demonstrates that there is a direct interaction between the AR DNA binding domain (DBD) and Tcf4. Tcf4 bound specifically to a glutathione S-transferase-ARDBD fusion protein and could be coimmunoprecipitated with beta-catenin and transfected AR or endogenous AR in prostate cancer cells. Transfected Tcf4 repressed the transcriptional activity of full-length AR and a VP16-ARDBD fusion protein, and this repression was only partially reversed by transfected beta-catenin. AR activation by cyproterone acetate, a partial agonist that did not support beta-catenin binding to the AR, was also repressed by Tcf4, further indicating that repression was not due to beta-catenin sequestration. Tcf4 could recruit beta-catenin to the AR DBD in vitro and to the cyproterone acetate-liganded AR in vivo. Chromatin immunoprecipitation experiments in LNCaP prostate cancer cells showed that endogenous AR was bound to a Tcf4-responsive element in the c-myc promoter. These findings indicate that AR and Tcf4 can interact directly and that this interaction may occur on the promoters or enhancers of particular genes. The direct AR-Tcf4 interaction, in conjunction AR- and Tcf4-beta-catenin binding, provides a mechanism for cooperative and selective gene regulation by AR and the Wnt/beta-catenin-Tcf pathway that may contribute to normal and neoplastic prostate growth.

Influence of sex hormone antagonists on the anticonvulsant action of conventional antiepileptic drugs against amygdala-kindled seizures in male and female rats

The effects of three gonadal steroid antihormones, tamoxifen (TXF, an estrogen antagonist), cyproterone acetate (CYP, an antiandrogen) and mifepristone (MIF, a progesterone antagonist) alone or combined with conventional antiepileptics were evaluated in amygdala-kindled seizures in male and female rats. None of the three antihormones used in this study affected any seizure parameter. TXF (50 mg/kg) and CYP (50 mg/kg), when combined with carbamazepine, or phenobarbital applied at their subprotective doses of 15 mg/kg, resulted in significant reductions of the seizure and afterdischarge durations, both in male and female rats. Additionally, the combination of carbamazepine and CYP markedly increased the afterdischarge threshold in fully-kindled rats of both genders. The interaction between antihormones and carbamazepine, or phenobarbital, was not reversed by respective sex steroid hormones (estradiol, testosterone). However, the TXF- and CYP-induced anticonvulsant effects in combinations with carbamazepine were attenuated by bicuculline, N-methyl-D-aspartate (NMDA) and aminophylline. Kainic acid and strychnine remained ineffective in this respect. The effect of a combination of TXF with phenobarbital was reversed by bicuculline and NMDA and that of CYP with phenobarbital-by bicuculline and aminophylline. Neither TXF nor CYP altered the free plasma concentrations of carbamazepine or phenobarbital, so a pharmacokinetic interaction is not probable. The combined treatment of the two antihormones with antiepileptic drugs did not affect motor performance, and did not result in significant long-term memory deficits. Our data confirm the hypothesis that sex hormone antagonist-mediated events may play some role in seizure processes in the central nervous system and can modulate the protective activity of some conventional antiepileptic drugs against kindled seizures.

Effects of finasteride and cyproterone acetate on hematuria associated with benign prostatic hyperplasia: a prospective, randomized, controlled study

OBJECTIVES

To evaluate the influence of two differently acting antiandrogens, finasteride (FIN) and cyproterone acetate (CPA), on the natural history of hematuria associated with benign prostatic hyperplasia (BPH) in a prospective, randomized, controlled study.

METHODS

Forty-two patients with hematuria episodes due to BPH were randomly allocated to three subgroups of 14 patients each and treated daily with either 5 mg FIN or 100 mg CPA or were placed in a watchful waiting arm. Patients were evaluated at 3-month intervals, and 40 patients had at least 1 year of follow-up.

RESULTS

Four patients in the FIN group (30%) and three in the CPA group (23%) presented with recurrent hematuria. In both groups, the bleeding episodes were treated conservatively and required no hospitalization. In the control group, 8 patients (57%) presented with recurrent bleeding; in 4, the bleeding was severe and required some form of intervention (catheterization or transurethral prostatectomy). When the frequency and severity of the hematuria episodes were analyzed over time, a statistically significant difference for FIN versus control was present at 9 and 12 months (analysis of variance, P = 0.035 and P = 0.009, respectively). A similar difference was evident for CPA versus control at 9 and 12 months (P = 0.028 and P = 0.008, respectively). No statistically significant difference was present between the FIN and CPA groups. Interestingly, no statistically significant effect in bleeding recurrence for both CPA and FIN over controls was present at 3 and 6 months of follow-up.

CONCLUSIONS

Both FIN and CPA seem to exert a comparable control in hematuria recurrence in patients with BPH, thus confirming the rationale behind the use of antiandrogens for such a purpose. Our results support the hypothesis that any antiandrogen, irrespective of the mode of action, would alter the natural history of BPH-associated hematuria. Interestingly, our results indicate that the speed of action of FIN may not be as rapid as previously described.

Effects of androgen treatment on expression of macrophage Fcgamma receptors

Macrophage Fcgamma receptors (FcgammaRs) play an important role in the host defense against infection and in the pathophysiology of immune cytopenias. Modulation of macrophage FcgammaR expression is a potential therapeutic approach to immune disorders. Glucocorticoids and progesterones decrease macrophage FcgammaR expression. We assessed the effect of treatment with androgens and antiandrogens on the expression of macrophage FcgammaRs using an experimental guinea pig model. Four androgens (testosterone, dihydrotestosterone, mesterolone, and danazol) and five antiandrogens (flutamide, nilutamide, cyproterone acetate, spironolactone, and finasteride) were studied. Following in vivo treatment of guinea pigs, we determined the clearance of immunoglobulin G (IgG)-sensitized erythrocytes in vivo, the binding of IgG-sensitized erythrocytes by isolated splenic macrophages, and splenic macrophage FcgammaR cell surface expression. All of the androgens impaired the clearance of IgG-sensitized erythrocytes by decreasing splenic macrophage FcgammaR expression. Dihydrotestosterone and mesterolone were more effective than testosterone or dihydrotestosterone. Flow cytometry and fluorescence microscopy with monoclonal antibodies demonstrated that the androgens decreased the cell surface expression of FcgammaR1,2 more than that of FcgammaR2. Antiandrogens did not significantly alter macrophage FcgammaR expression. Nevertheless, antiandrogens counteracted the effects of androgens on macrophage FcgammaR expression. These data indicate that androgens impair the clearance of IgG-coated cells by decreasing splenic macrophage FcgammaR expression. Thus, androgens other than danazol are candidate drugs for the treatment of immune disorders.

Clinical pharmacokinetics of the antiandrogens and their efficacy in prostate cancer

Prostatic cancer is the second most common cause of cancer death in males. Treatment by radical prostatectomy and radiotherapy is useful in the early stages of the disease. Whenever metastases occur, patients are usually treated by surgical (orchidectomy) or medical [gonadotropin releasing hormone (GnRH) analogue] castration. This form of treatment is, however, associated with unwanted adverse effects, such as flushing, loss of libido and potency and all patients ultimately escape therapy after a delay of 1 to 2 years. For this reason antiandrogens have been developed as another means of endocrine ablation therapy. Antiandrogens fall in 2 groups of which the first group, the steroidal antiandrogens such as cyproterone acetate (CPA), have a direct blocking effect at the cellular level but also inhibit testosterone production by their additional gestagenic properties blocking gonadotropin secretion. Except in preventing the flare-up associated with the start of GnRH analogue therapy and in reducing flushing, no evidence exist of any superiority for CPA over classical therapy in terms of adverse effects and survival. The second group, the nonsteroidal or 'pure' antiandrogens, only block androgens at the cellular level without any central effects. In contrast with other forms of castration, patients on pure antiandrogens as monotherapy preserve their sexual function and potency, at the expense of a slightly inferior androgen blockade and gynecomastia. These latter effects are explained by a compensatory rise in androgens as a result of the blockade at the central level, which weakens the androgen blockade, and by peripheral aromatisation of the increased androgens to oestrogens. In addition, some evidence exist that pure antiandrogens improve survival if combined with other forms of castration as they also inhibit the adrenal androgens, the so-called maximal androgen blockade (MAB). If patients escape control under MAB, a trial of stopping the antiandrogen must always be considered, as some tumours have 'learned' to be activated by these drugs. At the moment it is not yet clear if antiandrogens are of any benefit in downstaging the extent of disease before prostatectomy and/or radiotherapy. Of the currently known pure antiandrogens, bicalutamide offers some advantages over flutamide as it possesses a much longer half-life, allowing a once daily regimen, and has advantages over nilutamide in terms of fewer adverse effects.