Degarelix monotherapy compared with luteinizing hormone-releasing hormone (LHRH) agonists plus anti-androgen flare protection in advanced prostate cancer: an analysis of two randomized controlled trials

Relugolix for the treatment of prostate cancer

INTRODUCTION

Androgen deprivation therapy consists of the cornerstone of prostate cancer medical treatment. Until recently, castration of hypothalamus-hypophysis-gonadal axial was based on injectable medical agents. A few years ago, a novel per os administered GnRH antagonist was approved leading testosterone to castration level. Relugolix was approved by FDA in 2020, and it is the first per os administered GnRH antagonist. The present study is a literature review of the efficacy, safety and clinical perspectives of relugolix.

AREAS COVERED

A literature narrative review was conducted using PubMed/MEDLINE, Scopus, and the Cochrane library. Studies written in English language, considering efficacy, safety and cost-effectiveness of relugolix compared with other androgen deprivation therapies were included in the review.

EXPERT OPINION

Recent studies have examined efficacy of relugolix revealing a testosterone suppression percentage of 78.4% after 48 weeks from treatment initiation. Moreover, relugolix has been associated with less major cardiovascular events as well as better rate of testosterone recovery after treatment completion compared with the GnRH agonists. However, there is no head-to-head trial comparing relugolix with injectable GnRH antagonists, so far. As a result, a trial comparing the methods of antagonists' administration should be performed in the future.

Relugolix in the management of prostate cancer

INTRODUCTION

Relugolix is the first oral gonadotrophin-releasing hormone (GnRH) receptor antagonist. Based on the phase III HERO trial results, relugolix received Food and Drug Administration approval for adult patients with advanced prostate cancer (PCa).

AREAS COVERED

: We provide an overview of the preclinical and clinical development of relugolix and its role in the current treatment landscape of PCa.

EXPERT OPINION

Relugolix leads to rapid inhibition of testicular production of testosterone and its rapid recovery upon discontinuation. In the HERO trial, relugolix was associated with a superior cardiovascular safety profile compared to GnRH agonists. These attributes make relugolix a promising therapy for patients with pre-existing cardiovascular co-morbidities, those pursuing intermittent androgen deprivation therapy, and those who desire rapid testosterone recovery during "off-treatment" periods. In the HERO trial, very few patients received concomitant enzalutamide (n=17, 2.7%) or docetaxel (n<10, 1.3%). Safety of relugolix has not been established in combination with many androgen-receptor-axis targeted therapies (e.g. abiraterone, apalutamide), cabazitaxel, or lutetium Lu 177 vipivotide tetraxetan, which precludes its use in combination with these agents. In addition, being an oral drug, relugolix may also be associated with challenges of affordability, adherence, and compliance in this predominantly elderly population.

A review of clinical evidence to assess differences in efficacy and safety of luteinizing hormone-releasing hormone (LHRH) agonist (goserelin) and LHRH antagonist (degarelix)

Luteinizing hormone-releasing hormone agonist (LHRH-A), goserelin, and antagonist, degarelix, are both indicated for the treatment of advanced prostate cancer (PCa); however, large comparative trials evaluating their efficacy and safety are lacking. In this review, we assessed the available evidence for both the drugs. Although degarelix achieves an early rapid decline in testosterone (T) and prostate-specific antigen (PSA) levels, median T and PSA levels, in addition to prostate volume and International Prostate Symptom Scores, become comparable with goserelin over the remaining treatment period. Degarelix causes no initial flare, therefore it is recommended in patients with spinal metastases or ureteric obstruction. Goserelin achieves lower PSA, improved time to progression, and better survival outcomes when administered adjunctively to radiotherapy compared with radiotherapy alone, with significant results even over long-term follow-up. The evidence supporting adjuvant degarelix use is limited. Goserelin has better injection site safety, single-step delivery, and an efficient administration schedule compared with degarelix, which has significantly higher injection site reactions and less efficient administration mechanism. There is conflicting evidence about the risk of cardiovascular disease (CVD), and caution is required when using LHRH-A in patients with preexisting CVD. There is considerable long-term evidence for goserelin in patients with advanced PCa, with degarelix being a more recent option. The available comparative evidence of goserelin versus degarelix has several inherent limitations related to study design, sample size, conduct, and statistical analyses, and hence warrants robust prospective trials and long-term follow-up.

Sequencing of Systemic Therapies in the Management of Advanced Prostate Cancer in India: a Delphi-Based Consensus

INTRODUCTION

With the availability of an increasing number of therapeutic options for advanced prostate cancer (APC), optimal sequencing and combination of therapies have emerged to be the areas of challenges. In the Indian context, there is a dearth of consensus recommendations to guide clinicians regarding optimal sequencing of therapy in APC management. A Delphi-based consensus regarding optimal therapy sequencing in APC management was developed by an expert panel of medical oncologists from across India.

METHODS

An expert scientific committee of 11 medical oncologists and an expert panel of 53 medical oncologists from India constituted the panel for the Delphi consensus. In the first phase, a questionnaire with 41 clinical statements was developed in several critical controversial areas in APC treatment. In the second phase, 29 clinical statements were reworked and sent to eight experts to obtain their opinions on best practices. The consensus ratings were based on a 9-point Likert scale. Based on the overall response, statements with a mean score of ≥ 7 with 1 outlier were considered as "consensus."

RESULTS

Degarelix was the preferred androgen deprivation therapy (ADT). While ADT plus docetaxel was the preferred option for metastatic castrate-sensitive/naïve prostate cancer patients with high-volume disease, ADT with abiraterone was the preferred choice for low-volume disease. Docetaxel was the preferred first-line treatment option in men who received ADT alone in the castrate-sensitive/naïve setting. For patients progressing on or after docetaxel for metastatic castrate-resistant prostate cancer (without prior abiraterone or enzalutamide), the experts reached a consensus on the use of enzalutamide as the preferred second-line treatment option. No consensus was reached for the third-line treatment options.

CONCLUSION

This article is intended to serve as a guide to help clinicians discuss with their patients as part of the shared and multidisciplinary decision-making for improved APC management in India.

Relugolix: A new kid on the block among gonadotrophin-releasing hormone antagonists

Androgen-deprivation therapy (ADT) is the cornerstone of metastatic prostate cancer treatment. ADT can be achieved through surgical castration, or it may be induced either by gonadotrophin-releasing hormone (GnRH) agonists or GnRH antagonists. GnRH antagonists provide a more rapid castration alongside with a safer profile regarding adverse events. Degarelix is the sole GnRH antagonist used in clinical practice. Injection site reactions are the commonest adverse events related to the use of degarelix. Relugolix, a novel molecule, represents the first orally administered United States Food and Drug Administration approved GnRH antagonist, with clinical efficacy equal to that of the established ADT regimens. The main advantages of relugolix are the avoidance of the injection site reactions of GnRH antagonists such as degarelix alongside its patient-friendly oral administration. The aim of the present review article is to present novel data regarding the role of relugolix as ADT for the treatment of prostate cancer.

Abbreviations: ADT: androgen-deprivation therapy; FDA: United States Food and Drug Administration

Bilateral Orchidectomy Revisited in Management of Metastatic Hormone-Sensitive Prostate Cancer

INTRODUCTION

Androgen deprivation therapy (ADT) is a well-established treatment for metastatic hormone-sensitive prostate cancer (mHSPC). It includes either bilateral orchiectomy or medical castration in form of luteinizing hormone-releasing hormone (LHRH) agonist or antagonist. We conducted this study to compare surgical and medical castration in terms of time to progression (TTP) to castration resistant prostate cancer.

METHODS

Patients with mHSPC underwent either bilateral orchidectomy or medical castration by either LHRH agonist or by antagonist from November 2016 to May 2018 in our institution. Initial PSA and baseline imaging either magnetic resonance imaging (MRI) or positron emission tomography-computed tomography (PET CT) finding were recorded. Serum PSA, testosterone, and FSH were repeated every 3 months till 1 year. All enrolled patients were followed up with a bone scan/MRI/ PET CT at 6 months and 12 months. End point of study was progression of disease and death of patient.

RESULTS

Mean nadir PSA (ng/ml) after treatment was 4.7 and 9.8 in surgical and medical group respectively, whereas mean time to the nadir PSA was 8.7 and 8.8 respectively with no statistically significant difference. Mean TTP was 13.9 months in bilateral orchidectomy group and 13.8 months in medical castration group (chi-square 0.003, p value 0.958).

CONCLUSION

There was no significant difference in time to progression between bilateral orchidectomy and medical castration. Considering nadir PSA level, better quality of life, patient compliance, reduced hospital visit, and decrease in cost of treatment, bilateral orchidectomy may be a better treatment option especially in developing countries.

Degarelix for treating advanced hormone-sensitive prostate cancer

BACKGROUND

Degarelix is a gonadotropin-releasing hormone antagonist that leads to medical castration used to treat men with advanced or metastatic prostate cancer, or both. It is unclear how its effects compare to standard androgen suppression therapy.

OBJECTIVES

To assess the effects of degree compared with standard androgen suppression therapy for men with advanced hormone-sensitive prostate cancer.

SEARCH METHODS

We searched multiple databases (CENTRAL, MEDLINE, Embase, Scopus, Web of Science, LILACS until September 2020), trial registries (until October 2020), and conference proceedings (until December 2020). We identified other potentially eligible trials by reference checking, citation searching, and contacting study authors.

SELECTION CRITERIA

We included randomized controlled trials comparing degarelix with standard androgen suppression therapy for men with advanced prostate cancer.

DATA COLLECTION AND ANALYSIS

Three review authors independently classified studies and abstracted data from the included studies. The primary outcomes were overall survival and serious adverse events. Secondary outcomes were quality of life, cancer-specific survival, clinical progression, other adverse events, and biochemical progression. We used a random-effects model for meta-analyses and assessed the certainty of evidence for the main outcomes according to GRADE.

MAIN RESULTS

We included 11 studies with a follow-up of between three and 14 months. We also identified five ongoing trials. Primary outcomes Data to evaluate overall survival were not available.  Degarelix may result in little to no difference in serious adverse events compared to standard androgen suppression therapy (risk ratio (RR) 0.80, 95% confidence interval (CI) 0.62 to 1.05; low-certainty evidence; 2750 participants). Based on 114 serious adverse events in the standard androgen suppression group, this corresponds to 23 fewer serious adverse events per 1000 participants (43 fewer to 6 more). We downgraded the certainty of evidence for study limitations and imprecision. Secondary outcomes Degarelix likely results in little to no difference in quality of life assessed with a variety of validated questionnaires (standardized mean difference 0.06 higher, 95% CI 0.05 lower to 0.18 higher; moderate-certainty evidence; 2887 participants), with higher scores reflecting better quality of life. We downgraded the certainty of evidence for study limitations. Data to evaluate cancer-specific survival were not available. The effects of degarelix on cardiovascular events are very uncertain (RR 0.15, 95% CI 0.04 to 0.61; very low-certainty evidence; 80 participants). We downgraded the certainty of evidence for study limitations, imprecision, and indirectness as this trial was conducted in a unique group of high-risk participants with pre-existing cardiovascular morbidities. Degarelix likely results in an increase in injection site pain (RR 15.68, 95% CI 7.41 to 33.17; moderate-certainty evidence; 2670 participants). Based on 30 participants per 1000 with injection site pain with standard androgen suppression therapy, this corresponds to 440 more injection site pains per 1000 participants (192 more to 965 more). We downgraded the certainty of evidence for study limitations. We did not identify any relevant subgroup differences for different degarelix maintenance doses.

AUTHORS' CONCLUSIONS

We did not find trial evidence for overall survival or cancer-specific survival comparing degarelix to standard androgen suppression, but serious adverse events and quality of life may be similar between groups. The effects of degarelix on cardiovascular events are very uncertain as the only eligible study had limitations, was small with few events, and was conducted in a high-risk population. Degarelix likely results in an increase in injection site pain compared to standard androgen suppression therapy. Maximum follow-up of included studies was 14 months, which is short. There is a need for methodologically better designed and executed studies with long-term follow-up evaluating men with metastatic prostate cancer.

Current and emerging gonadotropin-releasing hormone (GnRH) antagonists for the treatment of prostate cancer

Introduction:Androgen deprivation therapy (ADT) is currently the backbone treatment of metastatic prostate cancer and is also used in combination with external beam radiotherapy (EBRT). Castration may be achieved either by bilateral orchiectomy or by administration of LHRH agonists or GnRH antagonists.Areas covered: In this article, the authors assess the current and emerging role of GnRH antagonists for the treatment of prostate cancer focusing on oncological results and safety (i.e. cardiovascular risk). In addition, updated data regarding the first orally administered GnRH antagonist, relugolix, is presented.Expert opinion: Studies demonstrate that GnRH antagonists are at least equal with LHRH agonists in terms of testosterone suppression and PSA progression free survival with a major advantage being rapid testosterone suppression. Thus, the optimal group of patients included symptomatic metastatic prostate cancer patients especially if cardiovascular comorbidities or LUTS are also present. Emerging data regarding benefit of the use of GnRH antagonists in patients with concomitant cardiovascular disease are of great interest. Relugolix has emerged as the first orally administered GnRH antagonist able to achieve and maintain testosterone castration levels and it is associated with a profound reduction of major cardiovascular events.

Progress in Clinical Research on Gonadotropin-Releasing Hormone Receptor Antagonists for the Treatment of Prostate Cancer

Gonadotropin-releasing hormone (GnRH) receptor agonists are still the most commonly used androgen deprivation treatment (ADT) drugs for prostate cancer in clinical practice. Currently, the GnRH receptor antagonists used for endocrine therapy for prostate cancer primarily include degarelix and relugolix (TAK-385). The former is administered by subcutaneous injection, while the latter is an oral drug. Compared to GnRH agonists, GnRH antagonists reduce serum testosterone levels more rapidly without an initial testosterone surge or subsequent microsurges. This review focuses on the mechanism of action of GnRH antagonists and agonists, the developmental history of GnRH antagonists, and emerging data from clinical studies of the two antagonists used as endocrine therapy for prostate cancer.

Androgen deprivation therapy and side effects: are GnRH antagonists safer?

Androgen deprivation therapy (ADT) with gonadotropin-releasing hormone (GnRH) agonists and antagonists is the mainstay of advanced prostate cancer treatment. Both drug classes decrease levels of luteinizing hormone and follicle-stimulating hormones (FSH), thereby lowering testosterone to castrate levels. This is associated with adverse events (AEs), including cardiovascular (CV) disorders, bone fractures, metabolic dysfunction, and impaired cognitive function. This literature review discusses these AEs, with a focus on CV and bone-related events. A hypothesis-generating meta-analysis of six clinical trials showed a potentially increased risk for CV disorders with GnRH agonists versus the GnRH antagonist degarelix. While no study has directly compared GnRH agonists versus antagonists with a primary CV outcome, one hypothesis for this observation is that GnRH agonists lead to initial surges in FSH that may negatively impact CV health, whereas antagonists do not. GnRH agonists are associated with metabolic and cognitive AEs and while data are lacking for GnRH antagonists, no differences in risk are predicted. Other common AEs with ADT include injection site reactions, which are much more common with degarelix than with GnRH agonists, which may reflect differing administration and injection techniques. Future studies are needed to further evaluate and compare the safety profiles of GnRH agonists and antagonists, especially in patients with pre-existing CV disease and other co-morbidities. Physicians should carefully evaluate benefits and risks when prescribing ADT and ensure that side effects are well managed.

Considerations for the use of gonadotropin-releasing hormone agonists and antagonists in patients with prostate cancer

Prostate cancer is the second most common cause of cancer-related deaths in men, representing a major source of morbidity and mortality. Androgen deprivation therapy is the primary treatment for patients with advanced prostate cancer at disease presentation, which can be achieved either with surgical or chemical castration. The development of gonadotropin-releasing hormone agonists revolutionized the treatment of advanced prostate cancer, replacing the need for surgical castration. Agonists downregulate gonadotropin-releasing hormone agonist receptors in the pituitary gland, and thus decrease the release of luteinizing hormone and testosterone. Although agonists are a common therapeutic option to date, their use is associated with testosterone surges, metabolic dysfunction and an increase in the risk of cardiovascular disease; they might contribute to tumor flares and potentially an increase in non-cancer mortality. More recently, gonadotropin-releasing hormone antagonists have entered the prostate cancer treatment landscape. Unlike agonists, antagonists directly inhibit the androgen receptor in the pituitary gland, and thus do not cause initial testosterone surges. In this article, we provide a concise review of the mechanism of actions, safety and efficacy of the approved agonists and antagonists for prostate cancer treatment.

Efficacy and safety of degarelix in patients with prostate cancer: Results from a phase III study in China

Objective

To establish non-inferiority of gonadotropin-releasing hormone degarelix compared with goserelin in suppressing and maintaining castrate testosterone levels from Day 28 to Day 364 in Chinese patients with prostate cancer.

Methods

This is an open-label, multi-centre study in which men aged ≥18 years were randomised in a 1:1 ratio to once-a-month subcutaneous injection of either degarelix (240/80 mg) or goserelin (3.6 mg) for 12 months. The primary endpoint was difference in 1-year cumulative probability of suppressing testosterone to ≤0.5 ng/mL. Non-inferiority was to be established if the lower 95% confidence interval (CI) limit for difference in cumulative probability between the treatment arms was greater than −10%. Secondary endpoints included cumulative probability of prostate-specific-antigen-progression-free-survival (PSA-PFS). Safety was also assessed.

Results

Baseline demographics and disease characteristics were similar between degarelix (n=142) and goserelin (n=141) treatment arms. The difference in cumulative probability of maintaining castrate levels from Day 28–364 was 3.6% (95% CI:−1.5%, 8.7%), demonstrating non-inferiority of degarelix. The cumulative probability of PSA-PFS at Day 364 was higher for degarelix (82.3%, 95% CI: 74.7%, 87.7%) versus goserelin (71.7%, 95% CI: 63.2%, 78.5%, p=0.038). Adverse events (AEs) were similar between treatment arms, except for more injection site reactions with degarelix versus goserelin. Four (2.8%) and nine (6.4%) patients discontinued due to AEs in degarelix and goserelin groups, respectively.

Conclusion

Degarelix was non-inferior to goserelin in achieving and maintaining testosterone suppression at castrate levels during 1-year treatment. PSA-PFS was significantly higher with degarelix, suggesting improved disease control. Both treatments were well tolerated.

Usefulness of combined androgen blockade therapy with gonadotropin-releasing hormone antagonist for bone metastatic prostate cancer with pretreatment prostate-specific antigen level ≥ 50 ng/mL

BACKGROUND

This study was performed to examine the usefulness of combined androgen blockade (CAB) therapy with a gonadotropin-releasing hormone (GnRH) antagonist (CAB-antagonist therapy), instead of CAB therapy with GnRH agonist (CAB-agonist therapy) against very high-risk prostate cancer (Pca).

METHODS

We retrospectively studied 84 Pca patients with pretreatment prostate-specific antigen (PSA) level ≥ 50 ng/mL, who were pathologically diagnosed between January 2007 and December 2016. GnRH antagonist was administered to 34 patients and GnRH agonist was administered to 50 patients. All patients received concurrent antiandrogen treatment. The primary end point was PSA progression-free survival (PSA-PFS).

RESULTS

PSA-PFS was significantly longer for the CAB-antagonist group compared to the CAB-agonist group (log-rank test, P <  0.01) in Pca patients with more than six bone metastases (the extent of disease [EOD] grade 2-4). On multivariate analysis, CAB-antagonist therapy was shown to be a possible prognostic factor for PSA-PFS (adjusted hazard ratio: 0.41, 95% confidence interval: 0.16-0.90, P = 0.03).

CONCLUSIONS

CAB-antagonist therapy may be a useful option in bone metastatic Pca patients with EOD grade 2-4.

Pharmacotherapeutic Targeting of G Protein-Coupled Receptors in Oncology: Examples of Approved Therapies and Emerging Concepts

G protein-coupled receptors (GPCRs) are involved in numerous physio-pathological processes, including the stimulation of cancer progression. In this regard, it should be mentioned that although GPCRs may represent major pharmaceutical targets, only a few drugs acting as GPCR inhibitors are currently used in anti-tumor therapies. For instance, certain pro-malignancy effects mediated by GPCRs are actually counteracted by the use of small molecules and peptides that function as receptor antagonists or inverse agonists. Recently, humanized monoclonal antibodies targeting GPCRs have also been developed. Here, we review the current GPCR-targeted therapies for cancer treatment, summarizing the clinical studies that led to their official approval. We provide a broad overview of the mechanisms of action of the available anti-cancer drugs targeting gonadotropin-releasing hormone, somatostatin, chemokine, and Smoothened receptors. In addition, we discuss the anti-tumor potential of novel non-approved molecules and antibodies able to target some of the aforementioned GPCRs in different experimental models and clinical trials. Likewise, we focus on the repurposing in cancer patients of non-oncological GPCR-based drugs, elucidating the rationale behind this approach and providing clinical evidence on their safety and efficacy.

The role of androgen deprivation therapy plus radiation therapy in patients with non-metastatic prostate cancer

INTRODUCTION

Androgen deprivation therapy (ADT) has a long and illustrious history in the treatment for prostate cancer and continues to be a mainstay treatment for locally advanced and high-risk patients. Because the survival for even high-risk prostate patients is lengthy, details of treatment such as duration and timing must be considered carefully and weighed against the various side effects.

AREAS COVERED

In the following article, we discuss the evolution of ADT from its initial applications in metastatic prostate cancer to its more recent incorporation into front line treatment in conjunction with radiation therapy (RT) for intermediate and high risk disease. We emphasize the results of phase III trials, which have defined the role of ADT in combination with RT in this patient population. We emphasize not only the potential benefits of ADT with RT, but also the potential risks, and underscore the need to consider both in order to maximize the therapeutic ration for each patient. Studies were identified via a search of PubMed as well as the bibliographies of articles discussed herein. Expert commentary: Even with advanced radiation techniques and dose escalation, adjuvant ADT continues to confer an overall survival benefit in intermediate and high-risk patients, although some evidence suggest that duration of treatment may be shortened, particularly for the high-risk group. The coming years will shed further information on this complicated topic with maturing of results from several ongoing trials.