Synergistic effects of BAY 60-4552 and vardenafil on relaxation of corpus cavernosum tissue of patients with erectile dysfunction and clinical phosphodiesterase type 5 inhibitor failure

Etiology of Male Infertility: an Update

Spermatogenesis is a complex process of germ cell division and differentiation that involves extensive cross-talk between the developing germ cells and the somatic testicular cells. Defective endocrine signaling and/or intrinsic defects within the testes can adversely affect spermatogenic progression, leading to subfertility/infertility. In recent years, male infertility has been recognized as a global public health concern, and research over the last few decades has elucidated the complex etiology of male infertility. Congenital reproductive abnormalities, genetic mutations, and endocrine/metabolic dysfunction have been demonstrated to be involved in infertility/subfertility in males. Furthermore, acquired factors like exposure to environmental toxicants and lifestyle-related disorders such as illicit use of psychoactive drugs have been shown to adversely affect spermatogenesis. Despite the large body of available scientific literature on the etiology of male infertility, a substantial proportion of infertility cases are idiopathic in nature, with no known cause. The inability to treat such idiopathic cases stems from poor knowledge about the complex regulation of spermatogenesis. Emerging scientific evidence indicates that defective functioning of testicular Sertoli cells (Sc) may be an underlying cause of infertility/subfertility in males. Sc plays an indispensable role in regulating spermatogenesis, and impaired functional maturation of Sc has been shown to affect fertility in animal models as well as humans, suggesting abnormal Sc as a potential underlying cause of reproductive insufficiency/failure in such cases of unexplained infertility. This review summarizes the major causes of infertility/subfertility in males, with an emphasis on infertility due to dysregulated Sc function.

Tadalafil-Loaded Self-Nanoemulsifying Chewable Tablets for Improved Bioavailability: Design, In Vitro, and In Vivo Testing

This research aimed to develop innovative self-nanoemulsifying chewable tablets (SNECT) to increase oral bioavailability of tadalafil (TDL), a nearly insoluble phosphodiesterase-5 inhibitor. Cinnamon essential oil, PEG 40 hydrogenated castor oil (Cremophor® RH 40), and polyethylene glycol 400 served as the oil, surfactant, and cosurfactant in the nanoemulsifying system, respectively. Primary liquid self-nanoemulsifying delivery systems (L-SNEDDS) were designed using phase diagrams and tested for dispersibility, droplet size, self-emulsifying capability, and thermodynamic stability. Adsorption on a carrier mix of silicon dioxide and microcrystalline cellulose was exploited to solidify the optimum L-SNEDDS formulation as self-nanoemulsifying granules (SNEG). Lack of crystalline TDL within the granules was verified by DSC and XRPD. SNEG were able to create a nanoemulsion instantaneously (165 nm), a little larger than the original nanoemulsion (159 nm). SNECT were fabricated by compressing SNEG with appropriate excipients. The obtained SNECT retained their quick dispersibility dissolving 84% of TDL within 30 min compared to only 18% dissolution from tablets of unprocessed TDL. A pharmacokinetic study in Sprague−Dawley rats showed a significant increase in Cmax (2.3-fold) and AUC0−24 h (5.33-fold) of SNECT relative to the unprocessed TDL-tablet (p < 0.05). The stability of TDL-SNECT was checked against dilutions with simulated GI fluids. In addition, accelerated stability tests were performed for three months at 40 ± 2 °C and 75% relative humidity. Results revealed the absence of obvious changes in size, PDI, or other tablet parameters before and after testing. In conclusion, current findings illustrated effectiveness of SNECT to enhance TDL dissolution and bioavailability in addition to facilitating dose administration.

Nitric Oxide-cGMP Signaling in Hypertension: Current and Future Options for Pharmacotherapy

For the treatment of systemic hypertension, pharmacological intervention in nitric oxide-cyclic guanosine monophosphate signaling is a well-explored but unexploited option. In this review, we present the identified drug targets, including oxidases, mitochondria, soluble guanylyl cyclase, phosphodiesterase 1 and 5, and protein kinase G, important compounds that modulate them, and the current status of (pre)clinical development. The mode of action of these compounds is discussed, and based upon this, the clinical opportunities. We conclude that drugs that directly target the enzymes of the nitric oxide-cyclic guanosine monophosphate cascade are currently the most promising compounds, but that none of these compounds is under investigation as a treatment option for systemic hypertension.

Novel Emerging Therapies for Erectile Dysfunction

Currently, several treatments exist for the improvement of erectile dysfunction (ED). These include medical therapies such as phosphodiesterase type 5 inhibitors (PDE5-Is), invasive methods such as intracavernosal injection therapy of vaso-active substances, vacuum erection devices, and penile prosthesis implants. However, the percentage of patients that are unresponsive to available treatments and who drop out from treatments remains high. Current evidence reveals that the pathogenesis of ED is related to multiple factors including underlying comorbidities, previous surgery, and psychological factors. Diverse approaches using novel molecular pathways or new technologies have been tested as potential therapeutic options for difficultto-treat ED populations. Melanocortin receptor agonist, a centrally acting agent, showed promising results by initiating erection without sexual stimulation in non-responders to PDE5-Is. Recent clinical and pre-clinical studies using human tissues suggested that new peripherally acting agents including the Max-K channel activator, guanylate cyclase activator, and nitric oxide donor could be potential therapies either as a monotherapy or in combination with PDE5-Is in ED patients. According to several clinical trials, regeneration therapy using stem cells showed favorable data in men with diabetic or post-prostatectomy ED. Low-intensity shock wave therapy also demonstrated promising results in patients with vasculogenic ED. There are growing evidences which suggest the efficacy of these emerging therapies, though most of the therapies still need to be validated by well-designed clinical trials. It is expected that, should their long-term safety and efficacy be proven, the emerging treatments can meet the needs of patients hitherto unresponsive to or unsatisfied by current therapies for ED.

Therapeutic Strategies for Erectile Dysfunction With Emphasis on Recent Approaches in Nanomedicine

This review addressed erectile dysfunction, regarding pathophysiology and therapeutic strategies. The line of treatment includes phosphodiesterase type-5 inhibitors and other types of therapy like topical and stem-cell transplant. Scientific literature was assessed to investigate the impact of nanotechnology on erectile dysfunction therapy. Various nanotechnology approaches were applied, like vesicular systems, lipid-based carriers, nanocrystals, dendrimers, liquid crystalline systems and nanoemulsions. Smart nano-systems can alter the landscape of the modern pharmaceutical industry by re- investigation of pharmaceutically suboptimal but biologically active entities for treatment of erectile dysfunction which were previously considered undeveloped.

Emerging Treatments for Erectile Dysfunction: a Review of Novel, Non-surgical Options

PURPOSE OF REVIEW

To review novel, non-surgical therapies for erectile dysfunction (ED).

RECENT FINDINGS

Recently, a landmark study identified the SIM1 locus, involved in the leptin-melanocortin pathway, as an independent risk factor for ED and a potential target for novel therapies. The recent literature otherwise has focused on low-intensity shock wave therapy (LiSWT), with several randomized trials and meta-analyses suggesting therapeutic efficacy. There are few novel oral agents for ED. There is growing evidence suggesting efficacy of intracavernosal stem cells therapy and low-intensity shock wave therapy (LiSWT), although these therapies are still investigational. A better understanding of the pathophysiologic spectrum of ED will offer new opportunities for novel, non-surgical therapies for ED.

Drugs in preclinical to phase II clinical development for the treatment of erectile dysfunction

INTRODUCTION

Erectile function is an important aspect in the quality of life of many men. For men with erectile dysfunction (ED), a spectrum of treatment options exists. Novel therapies for ED are currently being developed in order to delay surgical placement of a penile prosthesis - the final step in the management of treatment-refractory ED. Areas covered: This review examines innovative treatments such as alternative vasoactive agents, trophic factors and bio-compounds as well as gene and stem cell therapy. All therapies are currently in some phase of development for the management of ED. Using the MedLine and FDA Clinical Trials Registry, recent developments in treatment of ED were queried. Expert opinion: Recent studies have demonstrated the potential for multiple, novel therapies in the treatment of ED. Much of the work requires further experimentation in large-scale, blinded, placebo-controlled studies. This will require a concerted effort to bring these products to market.

Advances in the treatment of erectile dysfunction: what's new and upcoming?

Erectile dysfunction adversely affects up to 20% of all men and is the most commonly treated sexual disorder. The public health implications of this condition are significant and represent a challenge for our healthcare system. The physiological pathways responsible for erections have been extensively studied, and much advancement has been made since the introduction of phosphodiesterase 5 inhibitors. Newer agents, such as dopaminergic and melanocortin receptor agonists, which target central erectogenic pathways, are under investigation. Newer formulations and delivery methods of existing medications such as alprostadil will also be introduced in the near future. Furthermore, low-intensity shockwave lithotripsy and stem cell regenerative techniques are innovative approaches to the treatment of erectile dysfunction.

Erectile dysfunction

Erectile dysfunction is a multidimensional but common male sexual dysfunction that involves an alteration in any of the components of the erectile response, including organic, relational and psychological. Roles for nonendocrine (neurogenic, vasculogenic and iatrogenic) and endocrine pathways have been proposed. Owing to its strong association with metabolic syndrome and cardiovascular disease, cardiac assessment may be warranted in men with symptoms of erectile dysfunction. Minimally invasive interventions to relieve the symptoms of erectile dysfunction include lifestyle modifications, oral drugs, injected vasodilator agents and vacuum erection devices. Surgical therapies are reserved for the subset of patients who have contraindications to these nonsurgical interventions, those who experience adverse effects from (or are refractory to) medical therapy and those who also have penile fibrosis or penile vascular insufficiency. Erectile dysfunction can have deleterious effects on a man's quality of life; most patients have symptoms of depression and anxiety related to sexual performance. These symptoms, in turn, affect his partner's sexual experience and the couple's quality of life. This Primer highlights numerous aspects of erectile dysfunction, summarizes new treatment targets and ongoing preclinical studies that evaluate new pharmacotherapies, and covers the topic of regenerative medicine, which represents the future of sexual medicine.

Effects of PDE5 Inhibitors and sGC Stimulators in a Rat Model of Artificial Ureteral Calculosis

Urinary colics from calculosis are frequent and intense forms of pain whose current pharmacological treatment remains unsatisfactory. New and more effective drugs are needed to control symptoms and improve stone expulsion. Recent evidence suggested that the Nitric Oxide (NO) / cyclic guanosine monophosphate (cGMP) / phosphodiesterase type 5 (PDE5) system may contribute to ureteral motility influencing stone expulsion. We investigated if PDE5 inhibitors and sGC stimulators influence ureteral contractility, pain behaviour and stone expulsion in a rat model of ureteral calculosis. We investigated: a)the sex-specific PDE5 distribution in the rat ureter; b)the functional in vitro effects of vardenafil and sildenafil (PDE5 inhibitors) and BAY41-2272 (sGC stimulator) on induced ureteral contractility in rats and c)the in vivo effectiveness of vardenafil and BAY41-2272, alone and combined with ketoprofen, vs hyoscine-N-butylbromide alone or combined with ketoprofen, on behavioural pain indicators and stone expulsion in rats with artificial calculosis in one ureter. PDE5 was abundantly expressed in male and female rats’ ureter. In vitro, both vardenafil and BAY41-2272 significantly relaxed pre-contracted ureteral strips. In vivo, all compounds significantly reduced number and global duration of “ureteral crises” and post-stone lumbar muscle hyperalgesia in calculosis rats. The highest level of reduction of the pain behaviour was observed with BAY41-2272 among all spasmolytics administered alone, and with the combination of ketoprofen with BAY41-2272. The percentage of stone expulsion was maximal in the ketoprofen+BAY41-2272 group. The NO/cGMP/PDE5 pathway is involved in the regulation of ureteral contractility and pain behaviour in urinary calculosis. PDE5 inhibitors and sGC stimulators could become a potent new option for treatment of urinary colic pain.

Emerging drugs for the treatment of erectile dysfunction

INTRODUCTION

Erectile dysfunction adversely affects the lives of millions of men, and is the most commonly treated sexual disorder today. The erectile process has been extensively investigated, with major advances made in elucidating many of the complex molecular pathways involved. These advances have allowed researchers to design and study drug formulations that target various aspects of this complex process. The initial culmination of this research was the introduction of phosphodiesterase 5-inhibitors. While effective in many patients, they are not satisfactory for all afflicted men. As a result, researchers are developing novel drugs that target different molecular pathways.

AREAS COVERED

The paper will review these pathways, and the potential agents that target them. More specifically, first dopaminergic and melanocortin receptor agonists that act centrally will be covered. Then, the paper will examine the "second-generation" phosphodiesterase 5-inhibitors, soluble guanylate cyclases, rho-kinase inhibitors, and maxi-k channel activators that act peripherally.

EXPERT OPINION

Most of these novel drugs have yet to reach Phase III studies. However, it is likely that in years to come, patients will be selectively treated with these novel agents as a monotherapy or in combination with others acting in a synergistic manner.

Nebivolol potentiates the efficacy of PDE5 inhibitors to relax corpus cavernosum and penile arteries from diabetic patients by enhancing the NO/cGMP pathway

INTRODUCTION

The efficacy of oral pharmacotherapy for erectile dysfunction (ED) (i.e., type 5 phosphodiesterase[PDE5] inhibitors) is significantly reduced in diabetic patients. Nebivolol is a selective β1-blocker used for treatinghy pertension that has been shown to increase the efficacy of sildenafil to reverse ED in diabetic rats.

AIM

To evaluate the effects of nebivolol on the efficacy of the PDE5 inhibitors, sildenafil, tadalafil, and vardenafil to relax human corpus cavernosum (HCC) and vasodilate human penile resistance arteries (HPRA) from diabetic patients with ED (DMED). The influence of nebivolol on the capacity of these three PDE5 inhibitors to stimulate cyclic guanosine monophosphate (cGMP) production in HCC was also evaluated.

METHODS

HCC and HPRA were obtained from organ donors without ED (NEND; n = 18) or patients with diabetes undergoing penile prosthesis implantation (DMED; n = 19). Relaxations of HCC strips and HPRA to sildenafil,tadalafil, and vardenafil were evaluated in organ chambers and wire myographs. cGMP content in HCC was determined by ether extraction and quantification by ELISA.

MAIN OUTCOME MEASURES

Effects of nebivolol on PDE5 inhibitor-induced relaxation of HCC, vasodilation ofHPRA and cGMP accumulation in HCC.

RESULTS

Treatment with nebivolol (1 μM) significantly potentiated sildenafil-, tadalafil- and vardenafil-induced relaxations of HCC and vasodilations of HPRA from both NEND and DMED. Enhancement of relaxant capacity by nebivolol resulted in reversion of the impairment of PDE5 inhibition-induced responses in DMED and it was accompanied by enhancing the ability of PDE5 inhibitors to increase cGMP in HCC restoring reduced cGMP levelsin HCC from DMED.

CONCLUSIONS

Nebivolol potentiated the capacity of PDE5 inhibitors to relax vascular structures of erectile tissue from diabetic patients by enhancing the nitric oxide (NO)/cGMP pathway in these tissues. These effects suggest a potential therapeutic utility of nebivolol as an adjunct to PDE5 inhibitors for the treatment of ED associated with diabetes.

Reduction of obstruction related bladder overactivity by the guanylyl cyclase modulators BAY 41-2272 and BAY 60-2770 alone or in combination with a phosphodiesterase type 5 inhibitor

AIMS

To assess the urodynamic effects of soluble guanylyl cyclase (sGC) stimulator, BAY 41-2272, and activator, BAY 60-2770, (which both are able to induce cGMP synthesis even in the absence of nitric oxide (NO)) alone or in combination with a phosphodiesterase type 5 (PDE5) inhibitor, vardenafil, in a model of partial urethral obstruction (PUO) induced bladder overactivity (BO).

METHODS

Fifty-six male Sprague-Dawley rats were used, 31 of them underwent PUO. Fourteen rats were used for Western blots to assess PDE5 and sGC expression. For drug evaluation cystometry without anesthesia was performed three days following bladder catheterization.

RESULTS

Obstructed rats showed higher micturition frequency and bladder pressures than non-obstructed animals (Intermicturition Interval, IMI, 2.28 ± 0.55 vs. 3.60 ± 0.60 min (± standard deviation, SD); maximum micturition pressure, MMP, 70.1 ± 8.0 vs. 48.8 ± 7.2 cmH2O; both P < 0.05). In obstructed rats vardenafil, BAY 41-2272, and BAY 60-2770 increased IMI (2.77 ± 1.12, 2.62 ± 0.52, and 3.22 ± 1.04 min; all P < 0.05) and decreased MMP (54.4 ± 2.8, 61.5 ± 11.3, and 51.2 ± 6.3 cmH2O; all P < 0.05). When vardenafil was given following BAY 41-2272 or BAY 60-2770 no further urodynamic effects were observed. PDE5 as well as sGC protein expression was reduced in obstructed bladder tissue.

CONCLUSIONS

Targeting sGC via stimulators or activators, which increase the levels of cGMP independent of endogenous NO, is as effective as vardenafil to reduce urodynamic signs of BO. Targeting the NO/cGMP pathway via compounds acting on sGC might become a new approach to treat BO.

Treatment of erectile dysfunction: new targets and strategies from recent research

In recent years, research on penile erection has increasingly been centered on the molecular mechanisms involved. Major progress has been made in the field and at present a whole number of neurotransmitters, chemical effectors, growth factors, second-messenger molecules, ions, intercellular proteins, and hormones have been characterized as components of the complex process of erection. This knowledge has led to the discovery of several new therapeutic targets and multiple medical approaches for the treatment of erectile dysfunction (ED). This review focuses on the progress made in this field within the last few years.

Stem-cell therapy for erectile dysfunction

INTRODUCTION

Erectile dysfunction (ED) is the most common sexual disorder that men report to healthcare providers, and is the male sexual dysfunction that has been most investigated. Current treatments for ED focus on relieving the symptoms of ED and therefore tend to provide a temporary solution rather than a cure or reversing the cause. Recently, therapies based on stem cells (SCs) have had an increasing attention for their potential to restore erectile function. Preclinical studies showed that these cells might reverse the pathophysiological changes leading to ED, rather than treating the symptoms of ED. This review is intended to provide an overview of contemporary reports on the use of SCs to treat ED.

METHODS

We made an extensive search for reports on SC-based therapy for the management of ED, published in English between 1966 and 2013, using the search engines SciVerse-sciencedirect, SciVerse-scopus, Google Scholar and Pubmed, with the search terms 'erectile dysfunction', 'stem cells', 'multipotent stromal cells', 'adipose (tissue) derived stem cells', 'bone-marrow derived stem cells', 'animal model', 'diabetes', 'ageing', 'Peyronie's Disease' and 'cavernous nerve injury'.

RESULTS

Fifty-four papers were identified and contributed, either as an original research report or review thereof, to this review. Several preclinical studies addressed SC-based therapies for the recovery of erectile function caused by a variety of both chronic and acute conditions. Overall, these studies showed beneficial effects of SC therapy, while evidence on the mechanisms of action of SC therapy varied between studies. One clinical trial investigated the short-term effects of SC therapy in diabetic patients with ED. Two more clinical trials are currently recruiting patients.

CONCLUSIONS

The rapidly expanding and highly promising body of preclinical work on SC-based medicine providing a potential cure for ED, rather than merely symptom relief, is indicative of the increasing interest in regenerative options for sexual medicine over the past decade. Clinical trials are currently recruiting patients to test the preclinical results in men with ED.