Treatment with a GnRH receptor agonist, but not the GnRH receptor antagonist degarelix, induces atherosclerotic plaque instability in ApoE(-/-) mice

Assessing the effects of prostate cancer therapies on cardiovascular health

Contemporary advances in prostate cancer treatments have markedly improved patient outcomes, yet concerns persist regarding the increased cardiovascular toxicity of prostate cancer treatments, which is multifaceted. Local therapies entail non-negligible cardiovascular risks. The effects of androgen deprivation therapy, which is pivotal in disease management, on cardiovascular health remains contentious, with gonadotropin-releasing hormone agonists and antagonists showing varying cardiovascular outcomes. Despite the ongoing controversy over the cardiovascular risks of gonadotropin-releasing hormone antagonists versus agonists, current evidence does not support favouring one over the other based solely on cardiovascular risk. Combination therapy with androgen receptor pathway inhibitors and androgen deprivation therapy shows additive cardiovascular risks, but robust comparative data are lacking. Chemotherapies such as docetaxel and cabazitaxel, along with emerging targeted therapies and radiopharmaceuticals, are associated with varied cardiovascular risks, necessitating personalized patient assessment. Clinicians should adhere to cardio-oncology guidelines when prescribing therapeutic agents, especially for patients with pre-existing cardiovascular conditions. Optimal monitoring and management strategies are essential to mitigate cardiovascular morbidity and mortality.

A Model-Informed Drug Development Approach to Design a Phase 3 Trial of Teverelix Drug Product in Advanced Prostate Cancer Patients with Increased Cardiovascular Risk

Teverelix drug product (DP) is a parenteral gonadotropin-releasing hormone (GnRH) antagonist that has been successfully tested in phase 2 trials for hormone-sensitive advanced prostate cancer (APC) and benign prostatic hyperplasia (BPH). In previous APC trials, teverelix DP was administered as intramuscular (IM) and subcutaneous (SC) injections, using a loading dose and (in a single trial) a maintenance dose. Our objective was to derive an optimal dosing regimen for phase 3 clinical development, using a pharmacometrics modeling approach. Data from 9 phase 2 studies (229 patients) was utilized to develop a population pharmacokinetic (PK) model that described the concentration profile accommodating both IM and SC routes of administration. A 2-compartment model with sequential first-order absorption (slow and fast) and lag times best described the PK profiles of teverelix following SC and IM administration. An indirect response model with inhibition of production rate was fit to describe testosterone (T) concentrations based on physiological relevance. The final population PK-pharmacodynamic model was used to conduct simulations of various candidate dosing regimens to select the optimal dosing regimen to achieve clinical castration (T < 0.5 ng/mL by day 28) and to sustain clinical castration for 26 weeks. Model simulation showed that a loading dose of 360 mg SC and 180 mg IM with a maintenance dose of 360 mg SC 6-weekly (Q6W) starting at day 28 can achieve a ≥95% castration rate up to 52 weeks. This dose regimen was selected for phase 3 clinical development, which includes cardiovascular safety assessment in comparison to a GnRH agonist.

A practical guide for assessing and managing cardiovascular risk during androgen-deprivation therapy in patients with prostate cancer

Prostate cancer is the most common malignancy among men worldwide, and androgen-deprivation therapy (ADT) is a mainstay of treatment. There are observational data demonstrating an increased risk of cardiovascular events in patients who receive ADT, particularly those who have an elevated baseline cardiovascular risk. Because, for most patients with prostate cancer, death is predominantly from noncancer-related causes, cardiovascular disease and its risk factors should be optimized during cancer treatment. This review provides an overview of the landscape of ADT treatment and serves as a guide for appropriate cardiovascular screening and risk-mitigation strategies. The authors emphasize the importance of shared communication between the multidisciplinary cancer team and primary care to improve baseline cardiovascular screening and treatment of modifiable risk factors within this higher risk population.

Efficacy, tolerability, and safety of teverelix DP in patients with advanced prostate cancer: A multicenter, open-label, phase 2 trial

BACKGROUND

Teverelix drug product (DP) is a novel injectable gonadotropin-releasing hormone antagonist.

METHODS

An adaptive phase 2, open-label, multicenter trial was conducted in patients with advanced prostate cancer to evaluate the efficacy and safety of a combined subcutaneous (SC) and intramuscular (IM) loading dose regimen of teverelix DP of 120 mg SC + 120 mg IM (Group 1; N = 9) or 180 mg SC + 180 mg IM (Group 2; N = 41) administered at a single visit, followed by 6-weekly SC maintenance doses of 120 mg (Group 1) or 180 mg (Group 2), up to Day 168. The primary endpoint was the proportion of patients achieving castration levels with serum testosterone <0.5 ng/mL at Day 28 with a target castration rate of 90%. Injection sites were inspected by the investigator at every visit and reactions (ISRs) were proactively recorded.

RESULTS

The target castration rate was reached in Group 2 (97.5%) but not in Group 1 (62.5%). The castration rates were not maintained to Day 42 (Group 2: 82.5%; Group 1: 50.0%). Suppression of testosterone to castrate levels occurred rapidly (median time: 2 days for both groups). Suppression of testosterone, prostate-specific antigen, follicle-stimulating hormone, and luteinizing hormone was sustained throughout the treatment period, being more prominent with the higher dose. The adverse event (AE) profile was similar between groups. The most common AEs were injection-site induration (n = 40: 80.0%), injection-site erythema (n = 35: 70.0%), and hot flush (n = 21: 42.0%). Most ISRs were Grade 1.

CONCLUSION

Overall, the teverelix DP doses were generally well-tolerated but did not adequately maintain castration levels.

Follicle-Stimulating Hormone Exacerbates Cardiovascular Disease in the Presence of Low or Castrate Testosterone Levels

Low testosterone (T), common in aging men, associates with cardiovascular disease. We investigated whether follicle-stimulating hormone (FSH), which is affected by T, modulates the cardiovascular effects associated with low T or castration. FSHβ-/-:low-density lipoprotein receptor (LDLR)-/- mice, untreated or castrated (orchiectomy, gonadotropin-releasing hormone agonist or antagonist), demonstrated significantly less atherogenesis compared with similarly treated LDLR-/- mice, but not following FSH delivery. Smaller plaque burden in LDLR-/- mice receiving gonadotropin-releasing hormone antagonists vs agonists were nullified in FSHβ-/-:LDLR-/- mice. Atherosclerotic and necrotic plaque size and macrophage infiltration correlated with serum FSH/T. In patients with prostate cancer, FSH/T following androgen-deprivation therapy initiation predicted cardiovascular events. FSH facilitates cardiovascular disease when T is low or eliminated.

Perspectives on the Cardiovascular and Metabolic Effects of Androgen Deprivation Therapy in Prostate Cancer

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is the leading cause of non-cancer mortality in men with prostate cancer. This review summarizes the existing and emerging literature examining the cardiometabolic effects of androgen deprivation therapy (ADT) in prostate cancer.

RECENT FINDINGS

The evidence behind the metabolic effects of ADT is derived from older studies and has not been validated in modern cohorts. Most of the newer studies focus on the risk of cardiovascular disease (CVD) with ADT. Recently published studies like the HERO and PRONOUNCE trials have once again sparked debate about the effects of different types and durations of ADT on cardiovascular outcomes. The link between ADT and CVD is inherently complex with a majority of the evidence collected from population-based or non-randomized trials without enriching for high-risk populations. Ongoing clinical trials may provide more informative data to guide the cardiovascular care of prostate cancer survivors.

Management of Advanced Prostate Cancer With Relugolix: Illustrative Case Scenarios From an Advanced Practice Provider Perspective

Prostate cancer is the second most common cause of cancer-related mortality among men in the United States, with an estimated 34,700 deaths annually. Androgen deprivation therapy (ADT) is the cornerstone of advanced prostate cancer therapy, and injectable luteinizing hormone-releasing hormone (LHRH) agonists have served as the most commonly used ADT for over 30 years. Relugolix, a first-in-class, once-daily, oral gonadotropin-releasing hormone (GnRH) antagonist, was developed to address some of the limitations of available ADT therapies. Herein, we present two hypothetical case reports via an advanced practice provider (APP) perspective that reflect prototypical examples of patients with advanced localized disease not suitable for surgery or newly diagnosed hormone-sensitive metastatic disease treated with relugolix. The cases presented are meant to be instructional and within the scope of the current approved prescribing information for all medications mentioned. Best practices from an APP perspective are shared.

Androgen receptor inhibition suppresses anti-tumor neutrophil response against bone metastatic prostate cancer via regulation of TβRI expression

Bone metastatic disease of prostate cancer (PCa) is incurable and progression in bone is largely dictated by tumor-stromal interactions in the bone microenvironment. We showed previously that bone neutrophils initially inhibit bone metastatic PCa growth yet metastatic PCa becomes resistant to neutrophil response. Further, neutrophils isolated from tumor-bone lost their ability to suppress tumor growth through unknown mechanisms. With this study, our goal was to define the impact of metastatic PCa on neutrophil function throughout tumor progression and to determine the potential of neutrophils as predictive biomarkers of metastatic disease. Using patient peripheral blood polymorphonuclear neutrophils (PMNs), we identified that PCa progression dictates PMN cell surface markers and gene expression, but not cytotoxicity against PCa. Importantly, we also identified a novel phenomenon in which second generation androgen deprivation therapy (ADT) suppresses PMN cytotoxicity via increased transforming growth factor beta receptor I (TβRI). High dose testosterone and genetic or pharmacologic TβRI inhibition rescued androgen receptor-mediated neutrophil suppression and restored neutrophil anti-tumor immune response. These studies highlight the ability to leverage standard-care ADT to generate neutrophil anti-tumor responses against bone metastatic PCa.

Cardiovascular Impact of Androgen Deprivation Therapy: from Basic Biology to Clinical Practice

PURPOSE OF THE REVIEW

There have been increasing reports of cardiovascular complications of androgen deprivation therapy (ADT) leading to worse outcomes among patients with prostate cancer. While this may result from the direct effects of androgen suppression in the cardiovascular systems, there are ADT-type-specific distinct cardiovascular complications suggestive of mechanisms beyond androgen-mediated. Thus, it is critical to understand the biological and clinical impact of ADT on the cardiovascular system.

RECENT FINDINGS

Gonadotropin-releasing hormone (GnRH) agonists cause increased cardiovascular events compared to GnRH antagonists. Androgen receptor antagonists are linked to an increased risk of long QT syndrome, torsades de pointes, and sudden cardiac death. Androgen synthesis inhibitors are associated with increased rates of hypertension, atrial tachyarrhythmia, and, in rare incidences, heart failure. ADT increases the risk of cardiovascular disease. The risk among ADT drugs differs and must be evaluated to develop a medically optimal plan for prostate cancer patients.

Review of Cardiovascular Risk of Androgen Deprivation Therapy and the Influence of Race in Men with Prostate Cancer

Androgen deprivation therapy is the cornerstone of prostate cancer therapy. Recent studies have revealed an association between androgen deprivation therapy and cardiovascular adverse effects such as myocardial infarction and stroke. This review summarizes the available research on the cardiovascular risk of men using androgen deprivation therapy. We also discuss racial disparities surrounding both prostate cancer and cardiovascular disease, emphasizing the importance of biological/molecular and socioeconomic factors in assessing baseline risk in patients beginning androgen ablation. Based on the literature, we provide recommendations for monitoring patients who are at high risk for a cardiovascular adverse event while being treated on androgen deprivation therapy. This review aims to present the current research on androgen deprivation therapy and cardiovascular toxicity with an emphasis on racial disparities and provides a framework for clinicians to decrease the cardiovascular morbidity in men that are being treated with hormone therapy.

Androgen-deprivation therapy with leuprolide increases abdominal adiposity without causing cardiac dysfunction in middle-aged male mice: effect of sildenafil

Androgen-deprivation therapy (ADT) is the primary systemic therapy for treating advanced or metastatic prostate cancer (PCa), which has improved survival outcomes in patients with PCa. However, ADT may develop metabolic and cardiovascular adverse events that impact the quality of life and lifespan in PCa survivors. The present study was designed to establish a murine model of ADT with a gonadotropin-releasing hormone (GnRH) agonist leuprolide and to investigate its effects on metabolism and cardiac function. We also examined the potential cardioprotective role of sildenafil (inhibitor of phosphodiesterase 5) under chronic ADT. Middle-aged male C57BL/6J mice received a 12-wk subcutaneous infusion via osmotic minipumps containing either saline or 18 mg/4 wk leuprolide with or without 1.3 mg/4 wk sildenafil cotreatment. Compared with saline controls, leuprolide treatment significantly reduced prostate weight and serum testosterone levels, confirming chemical castration in these mice. The ADT-induced chemical castration was not affected by sildenafil. Leuprolide significantly increased the weight of abdominal fat after 12-wk treatment without a change in total body weight, and sildenafil did not block the proadipogenic effect of leuprolide. No signs of left ventricular systolic and diastolic dysfunction were observed throughout the leuprolide treatment period. Interestingly, leuprolide treatment significantly elevated serum levels of cardiac troponin I (cTn-I), a biomarker of cardiac injury, and sildenafil did not abolish this effect. We conclude that long-term ADT with leuprolide increases abdominal adiposity and cardiac injury biomarker without cardiac contractile dysfunction. Sildenafil did not prevent ADT-associated adverse changes.

Adverse cardiovascular effect following gonadotropin-releasing hormone antagonist versus GnRH agonist for prostate cancer treatment: A systematic review and meta-analysis

Background

Androgen deprivation therapy is the mainstay of medical treatment for prostate cancer (Pca); however, it is associated with an increased risk of adverse cardiovascular (CV) events and death. To date, CV death has been the leading noncancer cause of death in Pca patients. Both GnRH antagonists (an emerging class of drugs) and GnRH agonists (most frequently prescribed) are efficacious against Pca. However, the adverse effects, especially the adverse CV effect between them remain unclear.

Methods

Through a literature search using MEDLINE, EMBASE and the Cochrane Library, all available studies comparing the safety of CV risk between GnRH antagonists and GnRH agonists in Pca patients were extracted. Comparisons of outcomes of interest between these two classes of drugs were calculated using the risk ratio (RR). Subgroup analyses were performed depending on the study design and preexisting CV disease at baseline.

Results

Nine randomized controlled clinical trials (RCTs) and five real-world observational studies comprising 62160 Pca patients were included in our meta-analysis. Patients receiving GnRH antagonists experienced fewer CV events (RR: 0.66, 95% CI:0.53-0.82, P<0.001), CV death (RR:0.4, 95% CI: 0.24-0.67, P<0.001) and myocardial infarctions (RR: 0.71, 95% CI: 0.52-0.96, P=0.03). No difference was found in the incidence of stroke and heart failure. Moreover, GnRH antagonists were associated with fewer CV events in patients with preexisting CV disease but not in those without preexisting CV disease in the RCT series.

Conclusion

GnRH antagonists appear to offer favorable safety in terms of adverse CV events and CV death compared with GnRH agonists among men diagnosed with Pca, especially those who had established CV disease at baseline.

Systematic review registration

https://inplasy.com/inplasy-2023-2-0009/, identifier INPLASY202320009.

Safety, Pharmacokinetic and Pharmacodynamic Evaluation of Teverelix for the Treatment of Hormone-Sensitive Advanced Prostate Cancer: Phase 2 Loading-Dose-Finding Studies

Background and objectives: Teverelix drug product (DP) is a gonadotropin-releasing hormone antagonist in development for the treatment of patients with prostate cancer in whom androgen deprivation therapy is indicated. The aim of this paper is to present the results of five Phase 2 studies that assessed the pharmacokinetics, pharmacodynamics, efficacy and safety of different loading dose regimens of teverelix DP. Methods: Five single-arm, uncontrolled clinical trials were conducted in patients with advanced prostate cancer. The five different loading dose regimens of teverelix DP tested were (a) a single 90 mg subcutaneous (SC) injection of teverelix DP given on 3 consecutive days (Days 0, 1 and 2); (b) a single 90 mg intramuscular (IM) injection of teverelix DP given 7 days apart (Days 0 and 7); (c) a single 120 mg SC injection of teverelix DP given on 2 consecutive days (Days 0 and 1); (d) 2 × 60 mg SC injections of teverelix DP given on 3 consecutive days (Days 0, 1 and 2), and (e) 2 × 90 mg SC injections of teverelix DP given on 3 consecutive days (Days 0, 1 and 2). The primary efficacy parameter was the duration of action of an initial loading dose regimen in terms of suppression of testosterone to below the castration level (0.5 ng/mL). Results: Eighty-two patients were treated with teverelix DP. Two regimens (90 mg and 180 mg SC on 3 consecutive days) had a mean duration of castration of 55.32 days and 68.95 days with >90% of patients having testosterone levels < 0.5 ng/mL at Day 28. The mean onset of castration for the SC regimens ranged from 1.10 to 1.77 days, while it was slower (2.4 days) with IM administration. The most common adverse event (AE) was injection site reaction. No AEs of severe intensity were reported. Conclusions: Teverelix DP is safe and well tolerated. Castrate levels of testosterone can be rapidly achieved following the subcutaneous injection of teverelix DP on 3 consecutive days. Streamlining of the administration of the loading dose and identifying a suitable maintenance dose will be investigated in future trials.

Androgen Deprivation Therapy and Risk of Cardiovascular Disease in Patients With Prostate Cancer Based on Existence of Cardiovascular Risk

BACKGROUND

Controversy exists regarding the risk of cardiovascular disease (CVD) associated with androgen deprivation therapy (ADT) in patients with prostate cancer. We sought to evaluate the association between gonadotropin-releasing hormone (GnRH) agonists versus GnRH antagonist and the risk of CVD in patients with prostate cancer with or without prior CVD.

PATIENTS AND METHODS

Using administrative databases from Quebec, Canada, we identified first-time GnRH agonists and antagonist (degarelix) users between January 2012 and June 2016. Follow-up ended at the earliest of the following: first CVD event (myocardial infarction [MI], stroke, ischemic heart disease [IHD], arrhythmia, and heart failure [HF]); switch of GnRH group; death; or December 31, 2016. Inverse probability of treatment weighting (IPTW) based on the propensity score was used to control for potential confounding. IPTW-Cox proportional hazards model accounting for competing risks was used to evaluate the association of interest.

RESULTS

Among 10,785 patients identified, 10,201 and 584 were on GnRH agonists and antagonist, respectively. Median age was 75 years (interquartile range, 69-81 years) for both groups. A total of 4,152 (40.7%) men in the GnRH agonists group and 281 (48.1%) men in the GnRH antagonist group had CVD in the 3-year period prior to ADT initiation. Risk of HF was decreased in the antagonist group compared with the GnRH agonist group among patients with prior CVD (hazard ratio [HR], 0.46; 95% CI, 0.26-0.79). Risk of IHD was decreased in the antagonist group in patients without prior CVD (HR, 0.26; 95% CI, 0.11-0.65). Use of antagonist was associated with an increased risk of arrhythmia among patients with no prior CVD (HR, 2.34; 95% CI, 1.63-3.36).

CONCLUSIONS

Compared with GnRH agonists, the GnRH antagonist was found to be associated with a decreased risk of HF, specifically among patients with prior CVD. Among those with no prior CVD, the GnRH antagonist was associated with a decreased risk of IHD but an increased risk of arrhythmia.

How to Improve the Quality of Life of Patients with Prostate Cancer Treated with Hormone Therapy?

Prostate cancer (PC) is a hormone-sensitive tumor. Androgen deprivation therapy (ADT) is the cornerstone of systemic therapy for patients with intermediate or high-risk localized, recurrent, and metastatic prostate cancer. Although generally well tolerated, ADT can lead to short- and long-term adverse events that can worsen the quality of life of patients with PC. In the last decade, the introduction of novel generation androgen receptor pathway inhibitors (ARPI) has resulted in an improvement in the prognosis of patients with metastatic PC when used in combination with ADT. The use of ARPI in increasingly early stages of the disease determines a longer exposure of patients to these treatments. Although ARPIs are normally well-tolerated drugs, they generally cause an increase in toxicity compared to ADT alone, being able to worsen some adverse events already induced by ADT or leading to the development of specific side effects. Although there are no specific treatments for all the adverse events induced by hormonal therapies, it is essential to know the possible toxicities induced by the different treatments and to start procedures to prevent and/or recognize and consequently treat them early in order to not compromise the quality of life of the patients with PC. The aim of this review is to describe the adverse events induced by hormonal therapies. We will first describe the side effects induced by both ADT and ARPI and then the specific adverse events of the different ARPIs. Furthermore, we will try to highlight the possible therapeutic options to prevent or mitigate the toxicity induced by hormone therapies in order to improve the quality of life of the patients with PC.

Assessment and Mitigation of Cardiovascular Risk for Prostate Cancer Patients: A Review of the Evidence

Background

Cardiovascular disease (CVD) is a common comorbidity in patients with prostate cancer. In this review, we summarize the published literature on the association of cardiovascular risk with androgen deprivation therapy (ADT) treatment and explore the potential differences between the gonadotropin-releasing hormone (GnRH) agonists and antagonists and the molecular mechanisms that may be involved. We also provide a practical outlook on the identification of underlying CV risk and explore the different stratification tools available.

Results

While not definitive, the current evidence suggests that GnRH antagonists may be associated with lower rates of certain CV events vs agonists, particularly in patients with preexisting CVD. Risk reduction strategies such as lifestyle advice, consideration of ADT modality, and comedications may help to reduce CV risk factors and improve outcomes in prostate cancer patients receiving ADT.

Conclusions

Given all the data that is currently available, identification of baseline CV risk factors may be key to risk mitigation in patients with prostate cancer receiving ADT.

Endothelial dysfunction after androgen deprivation therapy and the possible underlying mechanisms

INTRODUCTION

Androgen deprivation therapy (ADT) is a key treatment modality in the management of prostate cancer (PCa), especially for patients with metastatic disease. Increasing evidences suggest that patients who received ADT have increased incidence of diabetes, myocardial infarction, stroke, and even mortality. It is important to understand the pathophysiological mechanisms on how ADT increases cardiovascular risk and induces cardiovascular events, which would provide important information for potential implementation of preventive measures.

METHODS

Twenty-six 12-week-old male SD rats were divided into four groups for different types of ADTs including: the bilateral orchidectomy group (Orx), LHRH agonist group (leuprolide), LHRH antagonist group (degarelix), and control group. After treated with drug or adjuvant injection every 3 weeks for 24 weeks, all rats were sacrificed and total blood were collected. Aorta, renal arteries, and kidney were preserved for functional assay, immunohistochemistry, western blot, and quantitative reverse-transcription polymerase chain reaction.

RESULTS

In vascular reactivity assays, aorta, intrarenal, and coronary arteries of all three ADT groups showed endothelial dysfunction. AT1R and related molecules at protein and messenger RNA (mRNA) level were tested, and AT1R pathway was shown to be activated and played a role in endothelial dysfunction. Both ACE and AT1R mRNA levels were doubled in the aorta in the leuprolide group while Orx and degarelix groups showed upregulation of AT1R in the kidney tissues. By immunohistochemistry, our result showed higher expression of AT1R in the intrarenal arteries of leuprolide and degarelix groups. The role of reactive oxygen species in endothelial dysfunction was confirmed by DHE fluorescence, nitrotyrosine overexpression, and upregulation of NOX2 in the different ADT treatment groups.

CONCLUSION

ADT causes endothelial dysfunction in male rats. GnRH receptor agonist compared to GnRH receptor antagonist, showed more impairment of endothelial function in the aorta and intrarenal arteries. Such change might be associated with upregulation and activation of AngII-AT1R-NOX2 induced oxidative stress in the vasculature. These results help to explain the different cardiovascular risks and outcomes related to different modalities of ADT treatment.

Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Prostate Cancer: The Primary Results of the PRONOUNCE Randomized Trial

BACKGROUND

The relative cardiovascular safety of gonadotropin-releasing hormone (GnRH) antagonists compared with GnRH agonists in men with prostate cancer and known atherosclerotic cardiovascular disease remains controversial.

METHODS

In this international, multicenter, prospective, randomized, open-label trial, men with prostate cancer and concomitant atherosclerotic cardiovascular disease were randomly assigned 1:1 to receive the GnRH antagonist degarelix or the GnRH agonist leuprolide for 12 months. The primary outcome was the time to first adjudicated major adverse cardiovascular event (composite of death, myocardial infarction, or stroke) through 12 months.

RESULTS

Because of slower-than-projected enrollment and fewer-than-projected primary outcome events, enrollment was stopped before the 900 planned participants were accrued. From May 3, 2016, to April 16, 2020, a total of 545 patients from 113 sites across 12 countries were randomly selected. Baseline characteristics were balanced between study groups. The median age was 73 years, 49.8% had localized prostate cancer; 26.3% had locally advanced disease, and 20.4% had metastatic disease. A major adverse cardiovascular event occurred in 15 (5.5%) patients assigned to degarelix and 11 (4.1%) patients assigned to leuprolide (hazard ratio, 1.28 [95% CI, 0.59-2.79]; P=0.53).

CONCLUSIONS

PRONOUNCE (A Trial Comparing Cardiovascular Safety of Degarelix Versus Leuprolide in Patients With Advanced Prostate Cancer and Cardiovascular Disease) is the first, international, randomized clinical trial to prospectively compare the cardiovascular safety of a GnRH antagonist and a GnRH agonist in patients with prostate cancer. The study was terminated prematurely because of the smaller than planned number of participants and events, and no difference in major adverse cardiovascular events at 1 year between patients assigned to degarelix or leuprolide was observed. The relative cardiovascular safety of GnRH antagonists and agonists remains unresolved. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02663908.

Gonadotropin-releasing hormone antagonist associated with lower cardiovascular risk compared with gonadotropin-releasing hormone agonist in prostate cancer: A nationwide cohort and in vitro study

BACKGROUND

We aimed to determine whether cardiovascular (CV) risk in patients with prostate cancer (PCa) differs between those who receive gonadotropin-releasing hormone (GnRH) agonist (GnRHa) therapy and those who receive GnRH antagonist therapy.

METHODS

Using the Taiwan National Health Insurance Research Database, we analyzed data by comparing 666 participants receiving GnRH antagonists and 1332 propensity score-matched participants treated with GnRHa in a 1:2 fashion during the period from May 1, 2015, to September 30, 2018. Cox proportional-hazards models were used to estimate the treatment effect on CV outcomes. Furthermore, we conducted an in vitro study to investigate the effect of a GnRHa (leuprolide) or a GnRH antagonist (degarelix) on matrix metalloproteinase-9 (MMP-9) expression and invasion ability in THP-1 differentiated macrophages.

RESULTS

GnRH antagonist therapy was associated with a lower risk of composite CV events of myocardial infarction, ischemic stroke, or CV death (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.25-0.90) than GnRHa therapy, with a mean follow-up period of 1.21 years. Significantly lower risks of CV death (HR, 0.21; 95% CI, 0.06-0.70) and all-cause mortality (HR, 0.77; 95% CI, 0.61-0.97) were observed in the GnRH antagonist group. In the in vitro study, leuprolide, but not degarelix, significantly increased the expression of MMP-9 activity and the invasive ability of THP-1 differentiated macrophages through gelatin zymography and the matrix invasion assay, respectively.

CONCLUSION

GnRH antagonists were associated with reduced risk CV events compared with the GnRHa among patients with PCa, which may be through effects on macrophages.

Hormonal manipulation in androgen signaling: a narrative review on using novel androgen therapy agents to optimize clinical outcomes and minimize side effects for prostate cancer patients

Prostate cancer is a significant public health burden and one of the most common cancers globally and in the United States. The current cornerstone of prostate cancer systemic treatment involves the suppression of androgen receptor (AR) signaling, either by reducing the body's testosterone production or inhibiting its binding to AR and its subsequent gene regulatory network driving carcinogenesis. This signaling pathway plays a central role in both hormone sensitive and castration resistant prostate cancer (CRPC), as evidenced by survival benefit when AR-targeted therapies are applied in the setting of CRPC. With the development of increasingly potent central and peripherally acting androgen targeting agents physicians treating prostate cancer can expect to treat their patients for a longer duration with a larger selection of effective agents. In this setting clinicians are now faced with questions of how to best tailor treatments for the prostate cancer patient to not only maximize overall survival but also optimize the quality of life and mitigate toxicity. In this manuscript we discuss the newer hormone therapy agents for prostate cancer and highlight what they indicate about optimizing medical castration, and the potential value of peripheral blockade.

A network pharmacology analysis on drug-like compounds from Ganoderma lucidum for alleviation of atherosclerosis

Ganoderma lucidum (GL) is known as a potent alleviator against chronic inflammatory disease like atherosclerosis (AS), but its mechanisms against AS have not been unveiled. This research aimed to identify the key compounds(s) and mechanism(s) of GL against AS through network pharmacology. The compounds from GL were identified by gas chromatography-mass spectrum (GC-MS), and SwissADME screened their physicochemical properties. Then, the target(s) associated with the screened compound(s) or AS related targets were identified by public databases, and we selected the overlapping targets using a Venn diagram. The networks between overlapping targets and compounds were visualized, constructed, and analyzed by RStudio. Finally, we performed a molecular docking test (MDT) to explore key target(s), compound(s), on AutoDockVina. A total of 35 compounds in GL were detected via GC-MS, and 34 compounds (accepted by Lipinski's rule) were selected as drug-like compounds (DLCs). A total of 34 compounds were connected to the number of 785 targets, and DisGeNET and Online Mendelian Inheritance in Man (OMIM) identified 2,606 AS-related targets. The final 98 overlapping targets were extracted between the compounds-targets and AS-related targets. On Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, the number of 27 signaling pathways were sorted out, and a hub signaling pathway (MAPK signaling pathway), a core gene (PRKCA), and a key compound (Benzamide, 4-acetyl-N-[2,6-dimethylphenyl]) were selected among the 27 signaling pathways via MDT. Overall, we found that the identified 3 DLCs from GL have potent anti-inflammatory efficacy, improving AS by inactivating the MAPK signaling pathway. PRACTICAL APPLICATIONS: Ganoderma lucidum (GL) has been used as a medicinal or edible mushroom for chronic inflammatory patients: diabetes mellitus and dyslipidemia, especially atherosclerosis (AS). Until now, the majority of mushroom research has been implemented regarding β-glucan derivatives with very hydrophilic physicochemical properties. It implies that β-glucan or its derivatives have poor bioavailability. Hence, we have involved GC-MS in identifying lipophilic compounds from GL, which filtered them in silico to sort drug-like compounds (DLCs). Then, we retrieved targets associated with the DLCs, and identified a key signaling pathway, key targets, and key compounds against AS. In this paper, we utilized bioinformatics and network pharmacology theory to understand the uncovered pharmacological mechanism of GL on AS. To sum things up, our analysis elucidates the relationships between signaling pathways, targets, and compounds in GL. Ultimately, this work provides biochemical evidence to identify the therapeutic effect of GL on AS, and a scientific basis for deciphering the key mechanism on DLCs of GL against AS.

Cardiovascular Toxicity of Androgen Deprivation Therapy

PURPOSE OF REVIEW

Androgen deprivation therapy (ADT) is the standard of care for the treatment of advanced prostate cancer (PC). ADT, particularly with GnRH agonists, leads to increased risk of cardiovascular disease, including myocardial infarction, hypertension, and stroke. This review discusses the options of ADT, the mechanism of ADT-associated cardiovascular side effects, and potential benefit by using GnRH antagonists.

RECENT FINDINGS

GnRH antagonists have relatively less cardiovascular adverse effects compared to GnRH agonists. We highlight on a recently published phase III clinical trial on the oral GnRH antagonist, relugolix, and its comparative benefit to traditional GnRH agonist regarding development of cardiovascular disease. Recent data reinforces that GnRH antagonists have a more favorable cardiovascular outcomes compared to GnRH agonists yet maintain a similar efficacy profile. From the data we reviewed, GnRH antagonists may be the preferred method of ADT for PC, but further data with primary cardiovascular outcomes are warranted.

Canadian Urological Association guideline on androgen deprivation therapy: Adverse events and management strategies

NA

Comparing the risk of cardiovascular disease following GnRH agonist and GnRH antagonist therapy for patient with prostate cancer: a systematic review and meta-analysis

INTRODUCTION

The aim of this review is to compare the risk of cardiovascular disease (CVD) following gonadotropin-releasing hormone (GnRH) agonist and GnRH antagonist therapy for patient with prostate cancer (PCa).

EVIDENCE ACQUISITION

We searched PubMed, Web of science, Opengery, Cochrane library databases and international congress reports for studies published before December 2019. This meta-analysis was conducted using Stata v. 12.0. Relative ratios (RRs) and their credible intervals (CI) were applied for the cardiovascular safety evaluation of androgen-deprivation therapy (ADT) medical interventions, including GnRH agonist and GnRH antagonist therapy. In addition, fixed-effect or random-effect models were applied in the statistical analyses according to the heterogeneity.

EVIDENCE SYNTHESIS

Six articles including 32,997 participants were analyzed with a random effects model. The results of meta-analysis showed that compared with GnRH agonist, the incidents of CVD was equal to GnRH antagonist therapy for patient with PCa (RR=0.98, 95% CI: 0.94-1.02). When considering, under sub-group analysis with randomized controlled trials (RCTs) or controlled clinical trials (CCTs), no statistical differences in risk of CVD were found in two sub-group analyses. No evidence of publication bias was found in our meta-analysis by a funnel plot (Pr> | z |=0.26).

CONCLUSIONS

This meta-analysis indicates that compared treatment with GnRH antagonist, risks of CVD in PCa patients was the same as GnRH agonist. Further RCTs are strongly required to provide more definitive evidence.

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.

Protective effect of pharmacological castration on metabolic perturbations and cardiovascular disease in the hyperglycemic male ApoE-/-:Ins2+/Akita mouse model

BACKGROUND

Unlike in other mouse models of atherogenesis, it has recently been suggested that orchiectomy plays a role in accelerating atherosclerosis and inhibiting the progression of cardiovascular disease in the ApoE^-/-:Ins2^+/Akita mouse model of hyperglycemia. Androgen-deprivation therapy (ADT) is a common treatment for prostate cancer, a population with high prevalence of cardiovascular disease and its risk factors. Our objectives were to test and further characterize the effects of pharmacological castration which is currently the acceptable modality to deliver ADT in the clinic.

METHODS

Male ApoE^-/-:Ins2^+/Akita mice received one of three modes of ADT (gonadotropin-releasing hormone (GnRH)-antagonist (degarelix), GnRH-agonist (leuprolide), or bilateral orchiectomy) and were compared to corresponding untreated control mice (n = 9-13/group). Mice were followed for 5 months. Body weight, fasting blood glucose, glucose tolerance, serum C-peptide, leptin, and testosterone levels along with atherosclerotic aortic plaque size and characteristics were determined. In a separate experiment, the survival of mice, untreated and on ADT, was determined.

RESULTS

Castration was achieved for all three modes of ADT. However, degarelix-treated mice gained significantly less weight, had lower serum leptin levels and systolic blood pressure compared to orchiectomy and leuprolide-treated mice. ADT improved dysglycemia and atherosclerotic burden. GnRH-antagonist significantly improved survival compared to GnRH-agonist but not compared to orchiectomy.

CONCLUSIONS

Further characterization of the ApoE^-/-:Ins2^+/Akita mouse model confirms that pharmacological ADT ameliorated metabolic syndrome and cardiovascular complications. Improved dysglycemia and atherosclerosis associated with increased survival which was longest after degarelix followed by orchiectomy.

Cardiovascular risks and toxicity - The Achilles heel of androgen deprivation therapy in prostate cancer patients

Androgen deprivation therapy (ADT) is the primary systemic therapy for treating locally advanced or metastatic prostate cancer (PCa). Despite its positive effect on PCa patient survival, ADT causes various adverse effects, including increased cardiovascular risk factors and cardiotoxicity. Lifespans extension, early use of ADT, and second-line treatment with next-generation androgen receptor pathway inhibitors would further extend the duration of ADT and possibly increase the risk of ADT-induced cardiotoxicity. Meanwhile, information on the molecular mechanisms underlying ADT-induced cardiotoxicity and measures to prevent it is limited, mainly due to the lack of specifically designed preclinical studies and clinical trials. This review article compiles up-to-date evidence obtained from observational studies and clinical trials, in order to gain new insights for deciphering the association between ADT use and cardiotoxicity. In addition, potential cardioprotective strategies involving GnRH receptors and second messenger cGMP are discussed.

Cardiac biomarkers in patients with prostate cancer and cardiovascular disease receiving gonadotrophin releasing hormone agonist vs antagonist

BACKGROUND

Gonadotrophin releasing hormone (GnRH) agonists and antagonists reduce testosterone levels for the treatment of advanced and metastatic prostate cancer. Androgen deprivation therapy (ADT) is associated with increased risk of cardiovascular (CV) events and CV disease (CVD), especially in patients with preexisting CVD treated with GnRH agonists. Here, we investigated the potential relationship between serum levels of the cardiac biomarkers N-terminal pro-B-type natriuretic peptide (NTproBNP), D-dimer, C-reactive protein (CRP), and high-sensitivity troponin (hsTn) and the risk of new CV events in prostate cancer patients with a history of CVD receiving a GnRH agonist or antagonist.

METHODS

Post-hoc analyses were performed of a phase II randomized study that prospectively assessed CV events in patients with prostate cancer and preexisting CVD, receiving GnRH agonist or antagonist. Cox proportional hazards models were used to determine whether the selected biomarkers had any predictive effect on CV events at baseline and across a 12-month treatment period.

RESULTS

Baseline and disease characteristics of the 80 patients who took part in the study were well balanced between treatment arms. Ischemic heart disease (66%) and myocardial infarction (37%) were the most common prior CVD and the majority (92%) of patients received CV medication. We found that high levels of NTproBNP (p = 0.008), and hsTn (p = 0.004) at baseline were associated with the development of new CV events in the GnRH agonist group but not in the antagonist. In addition, a nonsignificant trend was observed between higher levels of NTproBNP over time and the development of new CV events in the GnRH agonist group.

CONCLUSIONS

The use of cardiac biomarkers may be worthy of further study as tools in the prediction of CV risk in prostate cancer patients receiving ADT. Analysis was limited by the small sample size; larger studies are required to validate biomarker use to predict CV events among patients receiving ADT.

Optimizing screening and management of cardiovascular health in prostate cancer: A review

In clinical practice, cancer management does not consistently encompass screening and identification of cardiovascular (CV) risk. The use of androgen deprivation therapy (ADT) in prostate cancer has been associated with increased CV risk and development of metabolic syndrome, necessitating identification of patients at risk in this population (e.g., those with pre-existing CV disease). A multidisciplinary team of Canadian physicians was assembled to develop a series of recommendations intended to identify patients who may benefit from optimal management of their CV disease and/or modification of cardiac risk factors. A key goal was the development of a simple screening tool for identification of patients with pre-existing CV disease. This simple and inclusive set of recommendations are intended for use within urology clinics to facilitate holistic approaches and simplify the management of patients.

Effects of castration on atherosclerosis in Yucatan minipigs with genetic hypercholesterolemia

Background

Low plasma testosterone, either spontaneous or as a result of androgen deprivation therapy for prostate cancer, is associated with an increased risk of cardiovascular events. The underlying mechanism in humans is not understood. Experimental studies in mice have shown that castration facilitates atherogenesis and may increase signs of plaque vulnerability. Pigs used for translational atherosclerosis research have frequently been castrated for practical or commercial reasons, but the effect of castration on atherosclerosis has never been systematically evaluated in pigs.

Objective

To study the effect of castration on atherosclerotic plaque burden and type in genetically modified minipigs with hypercholesterolemia.

Methods

Newborn male Yucatan minipigs with transgenic overexpression of a human gain-of-function mutant of proprotein convertase subtilisin/kexin type 9 were randomized to undergo orchiectomy (n = 8) or serve as controls (n = 6). Minipigs were started on high-fat diet at 3 months of age and the amount and composition of atherosclerotic lesions were analyzed at 12 months of age. Plasma lipid profiles and behavioral parameters were also assessed.

Results

Plasma lipids were slightly affected to a more atherogenic profile by orchiectomy, but atherosclerotic lesion size was unaltered in the LAD, thoracic aorta, abdominal aorta, and iliac arteries. The distribution of lesion types (xanthomas, pathological intimal thickening and fibroatheromas) were also not statistically different between groups in any of the examined vascular territories. The abdominal aorta developed the most advanced stages of disease with reproducible fibroatheroma formation, and here it was found that the area of necrotic core was significantly increased in orchiectomized pigs compared with controls. Orchiectomy also reduced aggressive behavior.

Conclusions

Castration does not alter the burden of atherosclerosis in hypercholesterolemic Yucatan minipigs, but may increase necrotic core area in fibroatheromas.

Oral Relugolix for Androgen-Deprivation Therapy in Advanced Prostate Cancer

BACKGROUND

Injectable luteinizing hormone-releasing hormone agonists (e.g., leuprolide) are the standard agents for achieving androgen deprivation for prostate cancer despite the initial testosterone surge and delay in therapeutic effect. The efficacy and safety of relugolix, an oral gonadotropin-releasing hormone antagonist, as compared with those of leuprolide are not known.

METHODS

In this phase 3 trial, we randomly assigned patients with advanced prostate cancer, in a 2:1 ratio, to receive relugolix (120 mg orally once daily) or leuprolide (injections every 3 months) for 48 weeks. The primary end point was sustained testosterone suppression to castrate levels (<50 ng per deciliter) through 48 weeks. Secondary end points included noninferiority with respect to the primary end point, castrate levels of testosterone on day 4, and profound castrate levels (<20 ng per deciliter) on day 15. Testosterone recovery was evaluated in a subgroup of patients.

RESULTS

A total of 622 patients received relugolix and 308 received leuprolide. Of men who received relugolix, 96.7% (95% confidence interval [CI], 94.9 to 97.9) maintained castration through 48 weeks, as compared with 88.8% (95% CI, 84.6 to 91.8) of men receiving leuprolide. The difference of 7.9 percentage points (95% CI, 4.1 to 11.8) showed noninferiority and superiority of relugolix (P<0.001 for superiority). All other key secondary end points showed superiority of relugolix over leuprolide (P<0.001). The percentage of patients with castrate levels of testosterone on day 4 was 56.0% with relugolix and 0% with leuprolide. In the subgroup of 184 patients followed for testosterone recovery, the mean testosterone levels 90 days after treatment discontinuation were 288.4 ng per deciliter in the relugolix group and 58.6 ng per deciliter in the leuprolide group. Among all the patients, the incidence of major adverse cardiovascular events was 2.9% in the relugolix group and 6.2% in the leuprolide group (hazard ratio, 0.46; 95% CI, 0.24 to 0.88).

CONCLUSIONS

In this trial involving men with advanced prostate cancer, relugolix achieved rapid, sustained suppression of testosterone levels that was superior to that with leuprolide, with a 54% lower risk of major adverse cardiovascular events. (Funded by Myovant Sciences; HERO ClinicalTrials.gov number, NCT03085095.).

(-)-Epicatechin metabolites promote vascular health through epigenetic reprogramming of endothelial-immune cell signaling and reversing systemic low-grade inflammation

Ingestion of (-)-epicatechin flavanols reverses endothelial dysfunction by increasing flow mediated dilation and by reducing vascular inflammation and oxidative stress, monocyte-endothelial cell adhesion and transendothelial monocyte migration in vitro and in vivo. This involves multiple changes in gene expression and epigenetic DNA methylation by poorly understood mechanisms. By in silico docking and molecular modeling we demonstrate favorable binding of different glucuronidated, sulfated or methylated (-)-epicatechin metabolites to different DNA methyltransferases (DNMT1/DNMT3A). In favor of this model, genome-wide DNA methylation profiling of endothelial cells treated with TNF and different (-)-epicatechin metabolites revealed specific DNA methylation changes in gene networks controlling cell adhesion-extravasation endothelial hyperpermeability as well as gamma-aminobutyric acid, renin-angiotensin and nitric oxide hypertension pathways. Remarkably, blood epigenetic profiles of an 8 weeks intervention with monomeric and oligomeric flavanols (MOF) including (-)-epicatechin in male smokers revealed individual epigenetic gene changes targeting similar pathways as the in vitro exposure experiments in endothelial cells. Furthermore, epigenetic changes following MOF diet intervention oppose atherosclerosis associated epigenetic changes. In line with biological data, the individual epigenetic response to a MOF diet is associated with different vascular health parameters (glutathione peroxidase 1 and endothelin-1 expression, acetylcholine-mediated microvascular response), in part involving systemic shifts in blood immune cell types which reduce the neutrophil-lymphocyte ratio (NLR). Altogether, our study suggests that different (-)-epicatechin metabolites promote vascular health in part via epigenetic reprogramming of endothelial-immune cell signaling and reversing systemic low-grade inflammation.

Current and future strategies for the nutritional management of cardiometabolic complications of androgen deprivation therapy for prostate cancer

Androgen deprivation therapy (ADT) is used widely as part of a combined modality for the treatment of prostate cancer. However, ADT has also been associated with the development of cardiometabolic complications that can increase mortality from cardiovascular events. There is emerging evidence to suggest that ADT-related cardiometabolic risk can be mitigated by diet and lifestyle modification. While the clinical focus for a nutritional approach for achieving this effect is unclear, it may depend upon the timely assessment and targeting of dietary changes to the specific risk phenotype of the patient. The present review aims to address the metabolic origins of ADT-related cardiometabolic risk, existing evidence for the effects of dietary intervention in modifying this risk, and the priorities for future dietary strategies.

Degarelix versus luteinizing hormone-releasing hormone agonists for the treatment of prostate cancer

INTRODUCTION

Androgen deprivation therapy (ADT) is the mainstay for advanced, hormone-sensitive prostate cancer, and options include surgical castration, luteinizing hormone-releasing hormone (LHRH) agonist, and more recently, gonadotropin releasing hormone (GnRH) antagonist therapy. Our understanding of the mechanisms and adverse effects of ADT has increased substantially, including the class-specific adverse effects of ADT. Areas covered: This review will summarize the pharmacodynamic and pharmacokinetic properties of the GnRH antagonist degarelix and its role in the management of advanced prostate cancer, the clinical evidence supporting its regulatory approval, as well as potential benefits and disadvantages over traditional LHRH agonist therapy. Expert opinion: Degarelix represents a newer class of ADT that results in a rapid and reliable decline in serum testosterone, a quality that makes it particularly advantageous in men presenting with symptomatic, hormone-sensitive prostate cancer. Due to differences in mechanism of action, there is observational data suggesting a potential cardiovascular and even oncologic benefit over traditional LHRH agonist therapy. Further research is ongoing to more clearly define this potential benefit.

[Cardiovascular risk of androgen deprivation therapy for treatment of hormone-dependent prostate cancer : Differences between GnRH antagonists and GnRH agonists]

BACKGROUND

Several studies have indicated that reduction of testosterone levels in patients with prostate cancer undergoing androgen deprivation therapy (ADT) with gonadotropin-releasing hormone (GnRH) agonists can be associated with an increased risk of cardiovascular events. The GnRH antagonists have a different mode of action compared with GnRH agonists and may be preferred in ADT for patients with cardiovascular disease.

OBJECTIVE

This review article discusses potential mechanisms underlying the development of cardiovascular events associated with ADT when using GnRH agonists and explains the differences in mode of action between GnRH agonists and GnRH antagonists. Additionally, relevant studies are presented and practical recommendations for the clinical practice are provided.

MATERIAL AND METHODS

A literature search was performed. Full publications and abstracts published in the last 10 years up to September 2015 were considered to be eligible.

RESULTS

The GnRH antagonists were associated with a decreased risk of cardiovascular events compared with GnRH agonists in prostate cancer patients undergoing ADT and particularly in patients with cardiovascular risk factors or a history of cardiovascular disease. This decrease may be due to the different mode of action of GnRH antagonists compared with GnRH agonists.

CONCLUSION

Prostate cancer patients with either cardiovascular disease or an increased risk of experiencing a cardiovascular event undergoing ADT should be preferentially treated with GnRH antagonists.

Binding site of activators of the cystic fibrosis transmembrane conductance regulator in the nucleotide binding domains

The use of substances that could activate the defective chloride channels of the mutant cystic fibrosis transmembrane conductance regulator (CFTR) has been suggested as possible therapy for cystic fibrosis. Using epithelia formed by cells stably transfected with wildtype or mutant (G551D, G1349D) CFTR, we estimated the apparent dissociation constant, K(D), of a series of CFTR activators by measuring the increase in the apical membrane current. Modification of apparent K(D) of CFTR activators by mutations of the nucleotide-binding domains (NBDs) suggests that the binding site might be in these regions. The human NBD structure was predicted by homology with murine NBD1. An NBD1-NBD2 complex was constructed by overlying monomers to a bacterial ABC transporter NBD dimer in the "head-to-tail" conformation. Binding sites for CFTR activators were predicted by molecular docking. Comparison of theoretical binding free energy estimated in the model to free energy estimated from the apparent dissociation constants, K(D), resulted in a remarkably good correlation coefficient for one of the putative binding sites, located in the interface between NBD1 and NBD2.