Candidate Molecule for Premature Ejaculation, DA-8031: In Vivo and In Vitro Characterization of DA-8031

The role of tyrosine hydroxylase within dapoxetine-assisted therapy against premature ejaculation

BACKGROUND

There are several investigations that have revealed that cerebral dopamine (DA) plays a pivotal role in the occurrence of premature ejaculation (PE). Although tyrosine hydroxylase (TH) is an essential enzyme for the synthesis of DA, only few investigations have described the role of TH in regulation mechanisms for ejaculation till now. To investigate whether there is a correlation between TH expression level in the brain and different ejaculation behavior in rats. Then explore whether the TH expression in the brain will change after acute dapoxetine treatment in rats with Rapid ejaculation.

METHODS AND RESULTS

Rats (male, S-D rats, 6-8 weeks) were separated into three groups based on their ejaculation frequency: Rapid, Normal, and Sluggish. Expression level of DA in the brain was determined by enzyme-linked immune sorbent assay (ELISA) kit, TH expression level in the brain was determined by immunohistochemistry and Western Blot (WB) techniques. Among the three groups, DA and TH expression level were the highest in the Rapid ejaculation group, while the lowest was the Sluggish ejaculation group. The results also showed that TH level was positively associated with ejaculation frequency (r = 0.8038, P < 0.001) and negatively associated with ejaculation latency (r=-0.6199, P = 0.018). Furthermore, acute dapoxetine therapy in rats with Rapid ejaculation downregulated TH level in the brain.

CONCLUSION

Changes in ejaculation behavior were significantly linked with TH level. Upregulated TH in selected brain regions related with ejaculation could cause rapid ejaculation. The effect of dapoxetine in prolonging ejaculation could be related to TH downregulation within the brain.

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.

Phase I and phase II clinical trials for the treatment of male sexual dysfunction-a systematic review of the literature

INTRODUCTION

The prevalence of sexual dysfunctions has increased over the last decades; despite a number of available treatments for erectile dysfunction (ED), premature ejaculation (PE), and Peyronie's disease (PD), still several unmet therapeutic needs deserve to be fulfilled. The aim of this review is to detail on phase I and II clinical trials investigating novel medical treatments for ED, PE, and PD.

AREAS COVERED

We conducted a systematic review of the literature including both published and ongoing phase I and II registered trials focused on medical treatment of ED, PE, and PD during the last 5 years. A total of 35 trials have been identified. Most studies (63%) investigated ED treatments and 26% were still ongoing. Stem cells (SCs) therapy was assessed in 28% of trials.

EXPERT OPINION

SCs therapy represent a promising treatment for ED although only few patients have been treated to date. Likewise, the oral selective oxytocin receptor antagonists for treating PE showed excellent safety profile and deserve further investigations in phase III trials. Preliminary results of novel topical treatments for PD with fibrinolytic and antiinflammatory drugs are encouraging, but urgently need to be confirmed in large placebo-controlled trials.

Premature ejaculation: challenging new and the old concepts

Premature ejaculation remains a difficult condition to manage for patients, their partners, and the clinician. Whilst prevalence rates are estimated to be 20-40%, determining a diagnosis of premature ejaculation is difficult, as the definition remains both subjective and ill-defined in the clinical context. As our understanding of the ejaculatory pathway has improved, new opportunities to treat the condition have evolved with mixed results. In this review, we explore some of these controversies surrounding the aetiology, diagnosis, and treatment of this condition and discuss potential novel therapeutic options.

Pharmacokinetics and tolerability of DA-8031, a novel selective serotonin reuptake inhibitor for premature ejaculation in healthy male subjects

Objective

DA-8031 is a selective serotonin reuptake inhibitor under development for the treatment of premature ejaculation. This is the first-in-human study aimed at evaluating the pharmacokinetics and tolerability of DA-8031 and its metabolites (M1, M2, M4, and M5) in the plasma and urine after administration of a single oral dose in healthy male subjects.

Methods

A dose block-randomized, double-blind, placebo-controlled, single ascending dose study was conducted. Subjects received either placebo or a single dose of DA-8031 at 5, 10, 20, 40, 60, 80, or 120 mg. DA-8031 and its four metabolites were analyzed in the plasma and urine for pharmacokinetic evaluation. The effect of genetic polymorphisms of cytochrome-P450 (CYP) enzymes on the pharmacokinetics of DA-8031 was evaluated.

Results

After a single dose, plasma DA-8031 reached the maximum concentration at a median of 2–3 h and was eliminated with terminal elimination half-life of 17.9–28.7 h. The mean renal clearance was 3.7–5.6 L/h. Dose-proportional pharmacokinetics was observed over the dose range of 20–80 mg. Among the metabolites, M4 had the greatest plasma concentration, followed by M5 and M1. Subjects with CYP2D6 intermediate metabolizer had significantly greater dose-normalized C_max and AUC_0–t of DA-8031 as well as smaller metabolic ratios than those subjects with CYP2D6 extensive metabolizer. The most common adverse events were nausea, dizziness, and headache, and no serious adverse events were reported.

Conclusion

In conclusion, the systemic exposure of DA-8031 was increased proportionally to the dose within 20–80 mg. Genetic polymorphisms of CYP2D6 had an effect on the systemic exposure of DA-8031. DA-8031 was well tolerated after single doses of 80 mg or less.

Emerging and investigational drugs for premature ejaculation

Over the past 20−30 years, the premature ejaculation (PE) treatment paradigm, previously limited to behavioural psychotherapy, has expanded to include drug treatment. Pharmacotherapy for PE predominantly targets the multiple neurotransmitters and receptors involved in the control of ejaculation which include serotonin, dopamine, oxytocin, norepinephrine, gamma amino-butyric acid (GABA) and nitric oxide (NO). The objective of this article is to review emerging PE interventions contemporary data on the treatment of PE was reviewed and critiqued using the principles of evidence-based medicine. Multiple well-controlled evidence-based studies have demonstrated the efficacy and safety of selective serotonin reuptake inhibitors (SSRIs) in delaying ejaculation, confirming their role as first-line agents for the medical treatment of lifelong and acquired PE. Daily dosing of SSRIs is likely to be associated with superior fold increases in IELT compared to on-demand SSRIs. On-demand SSRIs are less effective but may fulfill the treatment goals of many patients. Integrated pharmacotherapy and CBT may achieve superior treatment outcomes in some patients. PDE-5 inhibitors alone or in combination with SSRIs should be limited to men with acquired PE secondary to co-morbid ED. New on-demand rapid acting SSRIs, oxytocin receptor antagonists, or single agents that target multiple receptors may form the foundation of more effective future on-demand medication. Current evidence confirms the efficacy and safety of dapoxetine, off-label SSRI drugs, tramadol and topical anaesthetics drugs. Treatment with α1-adrenoceptor antagonists cannot be recommended until the results of large well-designed RCTs are published in major international peer-reviewed medical journals. As our understanding of the neurochemical control of ejaculation improves, new therapeutic targets and candidate molecules will be identified which may increase our pharmacotherapeutic armamentarium.

Current and Emerging Treatments for Premature Ejaculation

INTRODUCTION

Over the past 20-30 years, the premature ejaculation (PE) treatment paradigm, previously limited to behavioral psychotherapy, has expanded to include drug treatment. Pharmacotherapy for PE predominantly targets the multiple neurotransmitters and receptors involved in the control of ejaculation, which include serotonin, dopamine, oxytocin, norepinephrine, gamma amino-butyric acid (GABA) and nitric oxide (NO).

AIM

The objective of this article is to review current and emerging PE interventions.

METHODS

Contemporary data on the treatment of PE were reviewed and critiqued using the principles of evidence-based medicine.

MAIN OUTCOME MEASURE

Integrated pharmacotherapy and cognitive behavioral therapy (CBT) may achieve superior treatment outcomes in some patients. Phosphodiesterase type 5 inhibitors alone or in combination with selective serotonin reuptake inhibitors (SSRIs) should be limited to men with acquired PE secondary to comorbid erectile dysfunction (ED). New on-demand rapid-acting SSRIs, oxytocin receptor antagonists, or single agents that target multiple receptors may form the foundation of more effective future on-demand medication.

RESULTS

Multiple well-controlled evidence-based studies have demonstrated the efficacy and safety of SSRIs in delaying ejaculation, confirming their role as first-line agents for the medical treatment of lifelong and acquired PE. Daily dosing of SSRIs is likely to be associated with superior fold increases in intravaginal ejaculation latency time compared with on-demand SSRIs. On-demand SSRIs are less effective but may fulfill the treatment goals of many patients.

CONCLUSIONS

Current evidence suggests that psychosexual CBT has a limited role in the contemporary management of PE and confirms the efficacy and safety of dapoxetine, off-label SSRI drugs, and topical anesthetics drugs. Treatment with tramadol, α1-adrenoceptor antagonists cannot be recommended until the results of large, well-designed randomized controlled trials are published in major international peer-reviewed medical journals. As our understanding of the neurochemical control of ejaculation improves, new therapeutic targets and candidate molecules will be identified, which may increase our pharmacotherepeutic armamentarium. McMahon CG. Current and emerging treatments for premature ejaculation. Sex Med Rev 2015;3:183-202.

An Update of the International Society of Sexual Medicine's Guidelines for the Diagnosis and Treatment of Premature Ejaculation (PE)

INTRODUCTION

In 2009, the International Society for Sexual Medicine (ISSM) convened a select panel of experts to develop an evidence-based set of guidelines for patients suffering from lifelong premature ejaculation (PE). That document reviewed definitions, etiology, impact on the patient and partner, assessment, and pharmacological, psychological, and combined treatments. It concluded by recognizing the continually evolving nature of clinical research and recommended a subsequent guideline review and revision every fourth year. Consistent with that recommendation, the ISSM organized a second multidisciplinary panel of experts in April 2013, which met for 2 days in Bangalore, India. This manuscript updates the previous guidelines and reports on the recommendations of the panel of experts.

AIM

The aim of this study was to develop clearly worded, practical, evidenced-based recommendations for the diagnosis and treatment of PE for family practice clinicians as well as sexual medicine experts.

METHOD

A comprehensive literature review was performed.

RESULTS

This article contains the report of the second ISSM PE Guidelines Committee. It offers a new unified definition of PE and updates the previous treatment recommendations. Brief assessment procedures are delineated, and validated diagnostic and treatment questionnaires are reviewed. Finally, the best practices treatment recommendations are presented to guide clinicians, both familiar and unfamiliar with PE, in facilitating treatment of their patients.

CONCLUSION

Development of guidelines is an evolutionary process that continually reviews data and incorporates the best new research. We expect that ongoing research will lead to a more complete understanding of the pathophysiology as well as new efficacious and safe treatments for this sexual dysfunction. We again recommend that these guidelines be reevaluated and updated by the ISSM in 4 years. Althof SE, McMahon CG, Waldinger MD, Serefoglu EC, Shindel AW, Adaikan PG, Becher E, Dean J, Giuliano F, Hellstrom WJG, Giraldi A, Glina S, Incrocci L, Jannini E, McCabe M, Parish S, Rowland D, Segraves RT, Sharlip I, and Torres LO. An update of the International Society of Sexual Medicine's guidelines for the diagnosis and treatment of premature ejaculation (PE). Sex Med 2014;2:60-90.

An update of the International Society of Sexual Medicine's guidelines for the diagnosis and treatment of premature ejaculation (PE)

INTRODUCTION

In 2009, the International Society for Sexual Medicine (ISSM) convened a select panel of experts to develop an evidence-based set of guidelines for patients suffering from lifelong premature ejaculation (PE). That document reviewed definitions, etiology, impact on the patient and partner, assessment, and pharmacological, psychological, and combined treatments. It concluded by recognizing the continually evolving nature of clinical research and recommended a subsequent guideline review and revision every fourth year. Consistent with that recommendation, the ISSM organized a second multidisciplinary panel of experts in April 2013, which met for 2 days in Bangalore, India. This manuscript updates the previous guidelines and reports on the recommendations of the panel of experts.

AIM

The aim of this study was to develop clearly worded, practical, evidenced-based recommendations for the diagnosis and treatment of PE for family practice clinicians as well as sexual medicine experts.

METHOD

A comprehensive literature review was performed.

RESULTS

This article contains the report of the second ISSM PE Guidelines Committee. It offers a new unified definition of PE and updates the previous treatment recommendations. Brief assessment procedures are delineated, and validated diagnostic and treatment questionnaires are reviewed. Finally, the best practices treatment recommendations are presented to guide clinicians, both familiar and unfamiliar with PE, in facilitating treatment of their patients.

CONCLUSION

Development of guidelines is an evolutionary process that continually reviews data and incorporates the best new research. We expect that ongoing research will lead to a more complete understanding of the pathophysiology as well as new efficacious and safe treatments for this sexual dysfunction. We again recommend that these guidelines be reevaluated and updated by the ISSM in 4 years.

Mondia whitei (Periplocaceae) prevents and Guibourtia tessmannii (Caesalpiniaceae) facilitates fictive ejaculation in spinal male rats

Background

Mondia whitei and Guibourtia tessmannii are used in Cameroon traditional medicine as aphrodisiacs. The present study was undertaken to evaluate the pro-ejaculatory effects of the aqueous and organic solvent extracts of these plants in spinal male rats.

Methods

In spinal cord transected and urethane-anesthetized rats, two electrodes where inserted into the bulbospongiosus muscles and the ejaculatory motor pattern was recorded on a polygraph after urethral and penile stimulations, intravenous injection of saline (0.1 ml/100 g), dopamine (0.1 μM/kg), aqueous and organic solvent plant extracts (20 mg/kg).

Results

In all spinal rats, urethral and penile stimulations always induced the ejaculatory motor pattern. Aqueous or hexane extract of Mondia whitei (20 mg/kg) prevented the expression of the ejaculatory motor pattern. The pro-ejaculatory effects of dopamine (0.1 μM/kg) were not abolished in spinal rats pre-treated with Mondia whitei extracts. Aqueous and methanolic stem bark extracts of Guibourtia tessmannii (20 mg/kg) induced fictive ejaculation characterized by rhythmic contractions of the bulbospongiosus muscles followed sometimes with expulsion of seminal plugs. In rats pre-treated with haloperidol (0.26 μM/kg), no ejaculatory motor pattern was recorded after intravenous injection of Guibourtia tessmannii extracts (20 mg/kg).

Conclusion

These results show that Mondia whitei possesses preventive effects on the expression of fictive ejaculation in spinal male rats, which is not mediated through dopaminergic pathway; on the contrary, the pro-ejaculatory activities of Guibourtia tessmannii require the integrity of dopaminergic system to exert its effects. The present findings further justify the ethno-medicinal claims of Mondia whitei and Guibourtia tessmannii.