Degarelix: a new approach for the treatment of prostate cancer

Urea-based anticancer agents. Exploring 100-years of research with an eye to the future

Suramin was the first urea-based drug to be approved in clinic, and in the following century a number of milestone drugs based on this scaffold were developed. Indeed, urea soon became a privileged scaffold in medicinal chemistry for its capability to establish a peculiar network of drug−target interactions, for its physicochemical properties that are useful for tuning the druggability of the new chemical entities, and for its structural and synthetic versatility that opened the door to numerous drug design possibilities. In this review, we highlight the relevance of the urea moiety in the medicinal chemistry scenario of anticancer drugs with a special focus on the kinase inhibitors for which this scaffold represented and still represents a pivotal pharmacophoric feature. A general outlook on the approved drugs, recent patents, and current research in this field is herein provided, and the role of the urea moiety in the drug discovery process is discussed form a medicinal chemistry standpoint. We believe that the present review can benefit both academia and pharmaceutical companies’ medicinal chemists to prompt research towards new urea derivatives as anticancer agents.

Differences in sex hormone recovery profile after cessation of 12-week gonadotropin-releasing hormone antagonist versus agonist therapy

BACKGROUND

Pharmacobiological behavior differs between gonadotropin-releasing hormone (GnRH) antagonists and GnRH agonists. However, reliable evidence clarifying the difference between them is limited.

OBJECTIVES

We aimed to elucidate the difference in recovery profile between GnRH antagonist (degarelix) and GnRH agonist (leuprorelin acetate or goserelin acetate) as short-term (12 weeks) neoadjuvant androgen deprivation therapy (ADT) prior to 125I-transperineal prostate brachytherapy (TPPB) for localized prostate cancer.

MATERIALS AND METHODS

This study was initially designed as a single-center, prospective, open-label, randomized controlled trial. The primary endpoint was a serum testosterone level above the castration range (>50 ng/dl) after the cessation of 12-week neoadjuvant ADT (GnRH antagonist or GnRH agonists). All patients underwent 12 weeks of neoadjuvant ADT. The recovery profiles of hormones, prostate-specific antigen, total prostate volume (TPV), bone mineral density, and quality of life scores were investigated.

RESULTS

Testosterone recovery duration after the last injection was significantly longer in the GnRH antagonist arm than in the GnRH agonist arm (median, 27.3 vs. 4.8 weeks, p < 0.001). The serum levels of luteinizing hormone and follicle-stimulating hormone in the GnRH antagonist arm also remained significantly lower than those in the GnRH agonist arm between 16 and 24 weeks (p < 0.01). Meanwhile, reduction in TPV at the time of TPPB was comparable between both arms (p = 0.128). There were also no significant between-arm differences in the International Prostate Symptom Score and the International Index of Erectile Function scores.

DISCUSSION AND CONCLUSION

The recovery patterns of hormonal profiles after short-term (12 weeks) neoadjuvant ADT differ between GnRH antagonists and GnRH agonists. The choice between these drugs matters and may have a clinical impact depending on the primary objective of ADT.

Homing Peptides for Cancer Therapy

Tumor-homing peptides are widely used for improving tumor selectivity of anticancer drugs and imaging agents. The goal is to increase tumor uptake and reduce accumulation at nontarget sites. Here, we describe current approaches for tumor-homing peptide identification and validation, and provide comprehensive overview of classes of tumor-homing peptides undergoing preclinical and clinical development. We focus on unique mechanistic features and applications of a recently discovered class of tumor-homing peptides, tumor-penetrating C-end Rule (CendR) peptides, that can be used for tissue penetrative targeting of extravascular tumor tissue. Finally, we discuss unanswered questions and future directions in the field of development of peptide-guided smart drugs and imaging agents.

Differential Impact of Gonadotropin-releasing Hormone Antagonist Versus Agonist on Clinical Safety and Oncologic Outcomes on Patients with Metastatic Prostate Cancer: A Meta-analysis of Randomized Controlled Trials

CONTEXT

Androgen deprivation therapy is the mainstay treatment of metastatic prostate cancer, achieved mainly by gonadotropin-releasing hormone (GnRH) agonists or antagonists.

OBJECTIVE

To investigate the differential impact of GnRH agonists and antagonists on clinical safety and oncologic outcomes.

EVIDENCE ACQUISITION

This meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A literature search using the electronic databases (MEDLINE, Web of Science, Cochrane Library, and Scopus) included randomized controlled trials comparing the clinical safety and oncologic outcomes of GnRH agonists and antagonists. The endpoints of interest were the following: (1) treatment-related adverse effects (AEs), (2) prostate-specific antigen (PSA) progression, and (3) overall mortality. The relative risk (RR) was used as the summary statistic, and results were reported with 95% confidence intervals (CIs).

EVIDENCE SYNTHESIS

Eight clinical trials (20 published studies) comprising 2632 men met our inclusion criteria; of them, 1646 received GnRH antagonist and 986 had GnRH agonist. Treatment-emerging AEs occurred in 73% patients in the GnRH antagonist group and 68% in the GnRH agonist group (RR: 1.10, 95% CI: 1.04-1.15). Serious AEs occurred in 9.8% of the GnRH antagonist and 11% of the GnRH agonist group (RR: 0.92, 95% CI: 0.73-1.17). Antagonists were associated with higher injection site reaction rates (38%) than agonists (4.8%). GnRH antagonist was associated with fewer cardiovascular events (RR: 0.52, 95% CI: 0.34-0.80). There was no significant difference in PSA progression, but GnRH antagonist was associated with lower overall mortality rates than GnRH agonists (RR: 0.48, 95% CI: 0.26-0.90, p =  0.02).

CONCLUSIONS

Existing data indicate that GnRH antagonist use is associated with significantly lower overall mortality and cardiovascular events as compared with agonists. These findings should be interpreted with caution owing to the short follow-up duration and assessment of cardiovascular events as secondary endpoints in the included trials. Further studies are needed to validate or refute these observations. Injection site reactions were significantly higher in the GnRH antagonist group.

PATIENT SUMMARY

Gonadotropin-releasing hormone (GnRH) antagonist is associated with lower death rates and cardiovascular events than GnRH agonists, based on the data from trials with short follow-up duration. GnRH agonists are associated with lower adverse events, such as decreased libido, hot flushes, erectile dysfunction, back pain, weight gain, constipation, and injection site reactions. There were no significant differences in prostate-specific antigen progression or fatigue.

Stress alters the expression of cancer-related genes in the prostate

Background

Prostate cancer is a major contributor to mortality worldwide, and significant efforts are being undertaken to decipher specific cellular and molecular pathways underlying the disease. Chronic stress is known to suppress reproductive function and promote tumor progression in several cancer models, but our understanding of the mechanisms through which stress contributes to cancer development and progression is incomplete. We therefore examined the relationship between stress, modulation of the gonadotropin-releasing hormone (GnRH) system, and changes in the expression of cancer-related genes in the rat prostate.

Methods

Adult male rats were acutely or repeatedly exposed to restraint stress, and compared to unstressed controls and groups that were allowed 14 days of recovery from the stress. Prostate tissue was collected and frozen for gene expression analyses by PCR array before the rats were transcardially perfused; and brain tissues harvested and immunohistochemically stained for Fos to determine neuronal activation.

Results

Acute stress elevated Fos expression in the paraventricular nucleus of the hypothalamus (PVH), an effect that habituated with repeated stress exposure. Data from the PCR arrays showed that repeated stress significantly increases the transcript levels of several genes associated with cellular proliferation, including proto-oncogenes. Data from another array platform showed that both acute and repeated stress can induce significant changes in metastatic gene expression. The functional diversity of genes with altered expression, which includes transcription factors, growth factor receptors, apoptotic genes, and extracellular matrix components, suggests that stress is able to induce aberrant changes in pathways that are deregulated in prostate cancer.

Conclusions

Our findings further support the notion that stress can affect cancer outcomes, perhaps by interfering with neuroendocrine mechanisms involved in the control of reproduction.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3635-4) contains supplementary material, which is available to authorized users.

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.

An update on the use of degarelix in the treatment of advanced hormone-dependent prostate cancer

Androgen deprivation therapy remains the mainstay of medical treatment for advanced prostate cancer. Commonly, this is achieved with medical androgen deprivation rather than surgical intervention as the permanence and psychological effects of the latter are unacceptable for most patients. Degarelix is a third generation antagonist of luteinizing hormone-releasing hormone (LHRH, also termed gonadotropin-releasing hormone) for the first-line treatment of androgen-dependent advanced prostate cancer. Degarelix acts directly on the pituitary receptors for LHRH, blocking the action of endogenous LHRH. The use of degarelix eliminates the initial undesirable surge in gonadotropin and testosterone levels, which is produced by agonists of LHRH. Degarelix is the most comprehensively studied and widely available LHRH antagonist worldwide. Clinical trials have demonstrated that degarelix has a long-term efficacy similar to the LHRH agonist leuprolide in achieving testosterone suppression in patients with prostate cancer. Degarelix, however, produces a faster suppression of testosterone and prostate-specific antigen (PSA), with no testosterone surges or microsurges, and thus prevents the risk of clinical flare in advanced disease. Recent clinical trials demonstrated that treatment with degarelix results in improved disease control when compared with an LHRH agonist in terms of superior PSA progression-free survival, suggesting that degarelix likely delays progression to castration-resistant disease and has a more significant impact on bone serum alkaline phosphatase and follicle-stimulating hormone. Degarelix is usually well tolerated, with limited toxicity and no evidence of systemic allergic reactions in clinical studies. Degarelix thus represents an important addition to the hormonal armamentarium for therapy of advanced androgen-dependent prostate cancer.

An update on the use of gonadotropin-releasing hormone antagonists in prostate cancer

Androgen deprivation therapy (ADT) is the main treatment approach in advanced prostate cancer and in recent years has primarily involved the use of gonadotropin-releasing hormone (GnRH) agonists. However, despite their efficacy, GnRH agonists have several drawbacks associated with their mode of action. These include an initial testosterone surge and testosterone microsurges on repeat administration. GnRH antagonists provide an alternative approach to ADT with a more direct mode of action that involves immediate blockade of GnRH receptors. Antagonists produce a more rapid suppression of testosterone (and prostate-specific antigen [PSA]) without a testosterone surge or microsurges and appear to offer an effective and well tolerated option for the hormonal treatment of prostate cancer. Comparisons with GnRH agonists have shown GnRH antagonists to be at least as effective in achieving and maintaining castrate testosterone levels in patients with prostate cancer. Furthermore, with antagonists, the lack of an initial testosterone surge (which may cause clinical flare) may allow more rapid relief of symptoms related to prostate cancer, avoid the need for concomitant antiandrogens to prevent clinical flare (so avoiding any antiandrogen-associated adverse events) and allow GnRH antagonist use in patients with high tumour burden and/or acute problems such as spinal cord compression. Although several antagonists have been investigated, only degarelix and abarelix are currently available for clinical use in prostate cancer. Currently, degarelix is the most extensively studied and widely available agent in this class. Degarelix is one of a newer generation of antagonists which, in a comprehensive and ongoing clinical development programme, has been shown to provide rapid, profound and sustained testosterone suppression without the systemic allergic reactions associated with earlier antagonists. This review examines the currently available data on GnRH antagonists in prostate cancer.

Immunization with a recombinant GnRH vaccine fused to heat shock protein 65 inhibits mammary tumor growth in vivo

Gonadotrophin-releasing hormone (GnRH) is the prime decapeptide hormone in the regulation of mammalian reproduction. Active immunization against GnRH has been a good treatment option to fight against hormone-dependent disease such as breast cancer. We designed and purified a novel protein vaccine Hsp65-GnRH(6) containing heat shock protein 65 (Hsp65) and six copies of GnRH in linear alignment. Immunization with Hsp65-GnRH(6) evoked strong humoral response in female mice. The generation of specific anti-GnRH antibodies was detected by ELISA and verified by western blot. In addition, anti-GnRH antibodies effectively neutralized endogenous GnRH activity in vivo, as demonstrated by the degeneration of the ovaries and uteri in the vaccinated mice. Moreover, the growth of EMT-6 mammary tumor allografts was inhibited by anti-GnRH antibodies. Histological examinations have shown that there was increased focal necrosis in tumors. Taken together, our results showed that immunization with Hsp65-GnRH(6) elicited high titer of specific anti-GnRH antibodies and further led to atrophy of reproductive organs. The specific antibodies could inhibit the growth of EMT-6 murine mammary tumor probably via an indirect mechanism that includes the depletion of estrogen. In view of these results, the protein vaccine Hsp65-GnRH(6) appears to be a promising candidate vaccine for hormone-dependent cancer therapy.

Evaluation of a stable gonadotropin-releasing hormone analog in mice for the treatment of endocrine disorders and prostate cancer

Gonadotropin-releasing hormone (GnRH) receptor agonists have wide clinical applications including the treatment of prostate cancer and endocrine disorders. However, such agonists are characterized by poor pharmacokinetic properties, often requiring repeated administration or special formulations. Therefore, the development of novel peptide analogs with enhanced in vivo stability could potentially provide therapeutic alternatives. The pharmacological evaluation of a bioactive peptide [Des-Gly¹⁰,Tyr⁵(OMe),D-Leu⁶,Aze-NHEt⁹]GnRH, analog 1, is presented herein and compared with leuprolide. Peptide stability was evaluated using mouse kidney membrane preparations, followed by a liquid chromatography-tandem mass spectrometry-based approach that afforded identification and quantification of its major metabolites. The analog was significantly more stable in vitro in comparison with leuprolide. In vitro and in vivo stability results correlated well, encouraging us to develop a clinically relevant pharmacokinetic mouse model, which facilitated efficacy measurements using testosterone as a biomarker. Analog 1, an agonist of the GnRH receptor with a binding affinity in the nanomolar range, caused testosterone release in mice that was acutely dose-dependent, an effect blocked by the GnRH receptor antagonist cetrorelix. Repeated dosing studies in mice demonstrated that analog 1 was well tolerated and had potency similar to that of leuprolide, based on plasma and testis testosterone reduction and histopathological findings. Analog 1 also shared with leuprolide similar significant antiproliferative activity on androgen-dependent prostate cancer (LNCaP) cells. On the basis of pharmacokinetic advantages, we expect that analog 1 or analogs based on this new design will be therapeutically advantageous for the treatment of cancer and endocrine disorders.