The Oxytocin Antagonist Cligosiban Prolongs Intravaginal Ejaculatory Latency and Improves Patient-Reported Outcomes in Men with Lifelong Premature Ejaculation: Results of a Randomized, Double-Blind, Placebo-Controlled Proof-of-Concept Trial (PEPIX)

Possible pathophysiologic roles of neurotransmitter systems in men with lifelong premature ejaculation: a scoping review

INTRODUCTION

Lifelong premature ejaculation (LPE) is a subtype of premature ejaculation. Genetic research on LPE has primarily focused on neurotransmitters such as serotonin, dopamine, and norepinephrine, whereas LPE treatment studies have focused on drugs such as selective serotonin reuptake inhibitors. However, findings from genetic association and pharmacotherapeutic studies have been inconsistent.

OBJECTIVES

To provide a quality overview of neurobiological targets that are potentially associated with LPE by investigating genetic association and pharmacotherapeutic studies.

METHODS

This scoping review was conducted per the PRISMA-ScR tool (Preferred Reporting Items for Systematic Reviews and Meta-analyses Extension for Scoping Reviews). Five databases were searched in March 2023 without timeline- or language-related restrictions.

RESULTS

After deduplication, 3949 records were obtained for review. Following screening and full-text review with citation tracking, 52 studies were included: 18 genetic and 34 pharmacotherapy studies. Serotonergic targets, such as the serotonin transporter and pre- and postsynaptic serotonergic receptors, were most often associated with LPE in genetic and pharmacotherapeutic studies. Mixed results were found among polymorphisms within genetic studies. This mechanism is in accordance with pharmacotherapeutic studies, as the highest efficacy was found for potent serotonergic antidepressants. Successful treatment was also observed with medication acting on phosphodiesterase-5 enzyme, such as tadalafil and vardenafil. Analyses of other genetic association studies did not yield any further evidence for associated targets.

CONCLUSIONS

This review is the first comprehensive scoping review on LPE. We found that serotonergic targets are most often associated with LPE, suggesting that the serotonergic pathway is a predisposing factor in LPE. Furthermore, there is some evidence for phosphodiesterase 5 inhibitors, which should be investigated. Other previously investigated neurobiological targets appear less likely to contribute to LPE. Future studies should focus on multiple targets, ideally in a genome-wide association study design.This review has been registered with the Open Science Framework (doi:10.17605/OSF.IO/JUQSD).

The oxytocin antagonist cligosiban reduces human prostate contractility: Implications for the treatment of benign prostatic hyperplasia

BACKGROUND AND PURPOSE

With increasing life expectancy, benign prostatic hyperplasia (BPH) consequently affects more ageing men, illustrating the urgent need for advancements in BPH therapy. One emerging possibility may be the use of oxytocin antagonists to relax smooth muscle cells in the prostate, similar to the currently used (although often associated with side effects) α1-adrenoceptor blockers.

EXPERIMENTAL APPROACH

For the first time we used live-imaging, combined with a novel image analysis method, to investigate the multidirectional contractions of the human prostate and determine their changes in response to oxytocin and the oxytocin antagonists atosiban and cligosiban. Human prostate samples were obtained and compared from patients undergoing prostatectomy due to prostate cancer as well as from patients with transurethral resection of prostate tissue due to severe BPH.

KEY RESULTS

The two cohorts of tissue samples showed spontaneous multidirectional contractions, which significantly increased after the addition of oxytocin. Different to atosiban, which showed ambiguous effects of short duration, only long-acting cligosiban reliably prevented, as well as counteracted, any contractile oxytocin effect. Furthermore, cligosiban visibly reduced not only oxytocin-induced contractions, but also showed intrinsic activity to relax prostatic tissue.

CONCLUSION AND IMPLICATIONS

Thus, the oxytocin antagonist cligosiban could be an interesting candidate in the search for novel BPH treatment options.

Current and emerging treatment options for premature ejaculation

Premature ejaculation (PE) is a prevalent male sexual dysfunction. Current standard treatment regimens include behavioural therapies, topical anaesthetics, dapoxetine and other selective serotonin reuptake inhibitors (SSRIs). Most of the pharmacotherapeutic options target neurotransmitters (such as serotonin and oxytocin) that have a role in the ejaculation mechanism. However, these treatments are mildly effective and only provide a temporary delay in the ejaculation latency time, and PE recurs when the treatment is stopped. Thus, a treatment for PE is urgently needed and research is ongoing to find the ideal PE therapy. The efficacy and safety of topical anaesthetics and SSRIs in delaying ejaculation have been confirmed in many well-designed controlled trials. Both preclinical and clinical studies on new-generation SSRIs are ongoing. Moreover, promising results came from clinical trials in which the efficacy of on-demand PE therapies targeting neurotransmitters other than serotonin, such as α1-adrenoceptor antagonists and oxytocin antagonists, was assessed. Surgical intervention and neuromodulation have been proposed as potential treatment options for PE; however, current PE guidelines do not recommend these treatments owing to safety concerns.

An up-to-date overview of the pharmacotherapeutic options for premature ejaculation

INTRODUCTION

Premature ejaculation (PE) is a sexual dysfunction of unknown etiology affecting a substantial number of males and deteriorating sexual health and quality of life of the patient and his partner. Treatment still remains challenging; however, pharmacotherapy is considered the mainstay of therapy with behavioral and psychosexual interventions being particularly important as adjudicate procedures, within the context of a holistic approach.

AREAS COVERED

The authors review the literature on the available medications for PE, both officially registered and non-registered. Currently, only dapoxetine and an anesthetic spray containing lidocaine and prilocaine (Fortacin™) are officially approved, with the rest being used off-label. Herein, updated data regarding the efficacy and safety of the pharmaceutical agents are presented.

EXPERT OPINION

On-demand dapoxetine is reportedly efficacious and safe in treating lifelong PE and is the first medication to be approved for this purpose. Fortacin has also shown considerable efficacy and may be reliably used on-demand. Phosphodiesterase type 5 inhibitors (PDE5Is) have been found to be effective in the treatment of PE and are therefore recommended either as monotherapy or combined with other therapies (i.e. dapoxetine). Adverse events of any therapy should be taken under consideration. Physicians should encourage patients to discuss their needs and expectations and grade any improvement of their condition with treatment.

Influence of modafinil on early ejaculation - Results from a double-blind randomized clinical trial

BACKGROUND

For men, early ejaculation is a serious health concern. Here, we tested the influence of modafinil (Profinil®) on early ejaculation. To this end, we performed a double-blind randomized clinical trial among men with early ejaculation.

METHODS

A total of 46 men with early ejaculation (mean age: 37.35 years) and in stable marital relationships with regular weekly penile-vaginal intercourse were randomly assigned either to the modafinil (100 mg) or to the placebo condition. Compounds were taken about 4-6h before intended penile-vaginal intercourse. At baseline and four weeks later at the end of the study, participants completed a series of self-rating questionnaires covering early ejaculation. Female partners also rated their male partners' early ejaculation profile.

RESULTS

Dimensions of early ejaculation improved over time, but only so in the modafinil condition, while no improvements were observed in the placebo condition.

CONCLUSIONS

Among male adults in stable marital relationships with regular weekly penile-vaginal intercourse modafinil improved dimensions of early ejaculation, always compared to placebo. Given the strong effect of modafinil on cognitive-executive processes, it is conceivable, that modafinil acted both via physiological and cognitive-executive pathways.

Oxytocin, Erectile Function and Sexual Behavior: Last Discoveries and Possible Advances

A continuously increasing amount of research shows that oxytocin is involved in numerous central functions. Among the functions in which oxytocin is thought to be involved are those that play a role in social and sexual behaviors, and the involvement of central oxytocin in erectile function and sexual behavior was indeed one of the first to be discovered in laboratory animals in the 1980s. The first part of this review summarizes the results of studies done in laboratory animals that support a facilitatory role of oxytocin in male and female sexual behavior and reveal mechanisms through which this ancient neuropeptide participates in concert with other neurotransmitters and neuropeptides in this complex function, which is fundamental for the species reproduction. The second part summarizes the results of studies done mainly with intranasal oxytocin in men and women with the aim to translate the results found in laboratory animals to humans. Unexpectedly, the results of these studies do not appear to confirm the facilitatory role of oxytocin found in male and female sexual behavior in animals, both in men and women. Possible explanations for the failure of oxytocin to improve sexual behavior in men and women and strategies to attempt to overcome this impasse are considered.

Physiological and pharmacological impact of oxytocin on epididymal propulsion during the ejaculatory process in rodents and men

During the emission phase of ejaculation, the sperm is driven from the cauda epididymidis, where it is stored, through the vas deferens by strong contractions. These contractions are thought of as being mainly induced by the sympathetic nervous system and the neurotransmitter noradrenaline. In the present study, we investigated the effect of oxytocin (suggested to exert effects during ejaculation as well) on defined segments of the rat and human epididymis using live imaging. Our results indicate that it is the very last part of the epididymis, segment 19 (S19) in rat and likewise segment 9 in human, which responds in a uniquely strong and rapid manner to oxytocin (similar to noradrenaline). Because of the complex nature of this contractile response, we developed an imaging analysis method, which allowed us to quantify multidirectional contractions and to display them using heat maps. The reaction of S19 to oxytocin was concentration-dependent and could be inhibited by pretreatment with oxytocin antagonists (atosiban and cligosiban), but not with an arginine vasopressin 1_A antagonist (SR49059). In both rat and human tissue, pretreatment with the alpha-1 adrenoreceptor antagonist tamsulosin inhibited the response to noradrenaline, whereas the effect of oxytocin was unimpaired. Our data (from men and rodents) strongly suggest that the hormone oxytocin is involved in the ejaculatory process. Thus, oxytocin-based medications might be a promising non-adrenergic treatment option for ejaculatory disorders. Additionally, we propose that S19 could be an advantageous model (detecting very low concentrations of oxytocin) to test the bioactivity of new oxytocin agonists and oxytocin antagonists.

Oxytocin receptor is a promising therapeutic target of malignant mesothelioma

Malignant mesothelioma (MM) is one of the most aggressive tumors. We conducted bioinformatics analysis using Cancer Cell Line Encyclopedia (CCLE) datasets to identify new molecular markers in MM. Overexpression of oxytocin receptor (OXTR), which is a G‐protein–coupled receptor for the hormone and neurotransmitter oxytocin, mRNA was distinctively identified in MM cell lines. Therefore, we assessed the role of OXTR and its clinical relevance in MM. Kaplan‐Meier and Cox regression analyses were applied to assess the association between overall survival and OXTR mRNA expression using The Cancer Genome Atlas (TCGA) datasets. The function of OXTR and the efficacy of its antagonists were investigated in vitro and in vivo using MM cell lines. Consistent with the findings from CCLE datasets analysis, OXTR mRNA expression was highly increased in MM tissues compared with other cancer types in the TCGA datasets, and MM cases with high OXTR expression showed poor overall survival. Moreover, OXTR knockdown dramatically decreased MM cell proliferation in cells with high OXTR expression via tumor cell cycle disturbance, whereas oxytocin treatment significantly increased MM cell growth. OXTR antagonists, which have high selectivity for OXTR, inhibited the growth of MM cell lines with high OXTR expression, and oral administration of the OXTR antagonist, cligosiban, significantly suppressed MM tumor progression in a xenograft model. Our findings suggest that OXTR plays a crucial role in MM cell proliferation and is a promising therapeutic target that may broaden potential therapeutic options and could be a prognostic biomarker of MM.

Oxytocin receptor antagonists as a novel pharmacological agent for reducing smooth muscle tone in the human prostate

Pharmacotherapies for the treatment of Benign Prostatic Hyperplasia (BPH) are targeted at reducing cellular proliferation (static component) or reducing smooth muscle tone (dynamic component), but response is unpredictable and many patients fail to respond. An impediment to identifying novel pharmacotherapies is the incomplete understanding of paracrine signalling. Oxytocin has been highlighted as a potential paracrine mediator of BPH. To better understand oxytocin signalling, we investigated the effects of exogenous oxytocin on both stromal cell proliferation, and inherent spontaneous prostate contractions using primary models derived from human prostate tissue. We show that the Oxytocin Receptor (OXTR) is widely expressed in the human prostate, and co-localises to contractile cells within the prostate stroma. Exogenous oxytocin did not modulate prostatic fibroblast proliferation, but did significantly (p < 0.05) upregulate the frequency of spontaneous contractions in prostate tissue, indicating a role in generating smooth muscle tone. Application of atosiban, an OXTR antagonist, significantly (p < 0.05) reduced spontaneous contractions. Individual tissue responsiveness to both exogenous oxytocin (R² = 0.697, p < 0.01) and atosiban (R² = 0.472, p < 0.05) was greater in tissue collected from older men. Overall, our data suggest that oxytocin is a key regulator of inherent spontaneous prostate contractions, and targeting of the OXTR and associated downstream signalling is an attractive prospect in the development of novel BPH pharmacotherapies.

Pharmacological management of male sexual dysfunction

Male sexual disorders, which are the target of clinical treatment, can be largely divided into erectile dysfunction (ED), ejaculation disorder, infertility, sexual desire disorder, hypogonadism, and other diseases related to penile structure changes, such as Peyronieʼs disease. Current approaches to ED treatment for most men are based on pharmacotherapy. Pharmacotherapy has evolved since the introduction of papaverine and phenoxybenzamine in the early 1980s. Sildenafil, a phosphodiesterase type 5 inhibitor (PDE5I), was the first approved drug for ED. Currently, PDE5Is are the most widely prescribed drugs and have an overall efficacy of 60% to 80% in all categories of ED. Most drugs used in ED are peripheral agents that act on the penis. If a combined treatment with a central nervous system agent and peripheral agents is possible, it may be an effective treatment strategy with higher efficacy. Premature ejaculation (PE) is the most frequent ejaculatory disorder. The absence of a consensus on the definition of PE has served as an obstacle in the investigation of its prevalence and the effectiveness of treatment strategies. Although the etiology of PE is unknown, some biological and psychological hypotheses, including anxiety, penile hypersensitivity, and 5-hydroxytryptamine receptor dysfunction have been suggested. Dapoxetine hydrochloride, a short-acting selective serotonin reuptake inhibitor, was approved for on-demand treatment of PE. Off-label use of antidepressants, topical anesthetic agents, tramadol, and PDE5Is is now available as a pharmacological option. The aim of this review is to describe recent advancements in the pharmacological treatment of male sexual disorders, especially focused on ED and PE.