Avanafil, a Highly Selective Phosphodiesterase Type 5 Inhibitor for Erectile Dysfunction, Shows Good Safety Profiles for Retinal Function and Hemodynamics in Anesthetized Dogs

NCX 1741, a Novel Nitric Oxide-Donating Phosphodiesterase-5 Inhibitor, Exerts Rapid and Long-Lasting Intraocular Pressure-Lowering in Cynomolgus Monkeys

Purpose: We studied the IOP-lowering effects of NCX 1741, a novel nitric oxide (NO)-donating derivative of the phosphodiesterase type-5 inhibitor, avanafil, in Cynomolgus monkey with laser-induced ocular hypertension (OHT-monkeys). NCX 1193 (NO-donating moiety), NCX 1744 (NCX 1741 without ester nitrate moiety), and travoprost (PGF2α analogue) were used for comparison. Ocular exposure after NCX 1741 dosing also was addressed. Methods: Vehicle (phosphate buffer pH 6.0, Kolliphor^® 5%, DMSO 0.3%, benzalkonium chloride 0.02%), NCX 1741, NCX 1193, NCX 1744, or travoprost were instilled (30 μL; single dose) masked and conscious IOPs were measured by pneumatonometry. LC-MS/MS-based methods were employed to monitor ocular exposure of NCX 1741 and main metabolites after ocular dosing in New Zealand White rabbits. Results: NCX 1741 (2.2%, 0.8 μmol/eye) lowered IOP with an E_max (ΔΔIOP, IOP change vs. pre-dose and vehicle) between 5 and 8 h post-dosing (ΔΔIOP_5h, -5.3 ± 2.0 mmHg and ΔΔIOP_8h, -6.0 ± 2.1 mmHg). Conversely, equimolar (0.47%, 0.8 μmol/eye) NCX 1193 IOP-lowering effects were maximal 3 h post-dosing (ΔΔIOP_3h, -4.7 ± 1.6 mmHg) and declined thereafter (ΔΔIOP_5h, -1.6 ± 1.1 mmHg). In a follow-up study, NCX 1741 (1.5%, 0.5 μmol/eye) was more effective than NCX 1744 despite a similar duration. Further, NCX 1741 was as effective as travoprost (0.1%, 0.06 μmol/eye) at 5 and 8 h post-dosing (travoprost, ΔΔIOP_5h, -3.4 ± 2.2 mmHg and ΔΔIOP_8h, -4.9 ± 1.3 mmHg) but had shorter duration (NCX 1741, ΔΔIOP_24h, -1.5 ± 1.1 mmHg; travoprost, ΔΔIOP_24h, -7.1 ± 2.8 mmHg). NCX 1741 resulted in significant aqueous humor exposure, as determined by the levels of the main metabolite, avanafil. Conclusions: NCX 1741 rapidly and effectively lowers IOP in OHT-monkeys for several hours post-dosing. How these effects translate in humans is still to be defined.

Pathophysiology of visual disorders induced by phosphodiesterase inhibitors in the treatment of erectile dysfunction

Aim

The aim of this review was to summarize the ocular action of the most common phosphodiesterase (PDE) inhibitors used for the treatment of erectile dysfunction and the subsequent visual disorders.

Method

This is a literature review of several important articles focusing on the pathophysiology of visual disorders induced by PDE inhibitors.

Results

PDE inhibitors have been associated with ocular side effects, including changes in color vision and light perception, blurred vision, transient alterations in electroretinogram (ERG), conjunctival hyperemia, ocular pain, and photophobia. Sildenafil and tadalafil may induce reversible increase in intraocular pressure and be involved in the development of non-arteritic ischemic optic neuropathy. Reversible idiopathic serous macular detachment, central serous chorioretinopathy, and ERG disturbances have been related to the significant impact of sildenafil and tadalafil on retinal perfusion.

Discussion

So far, PDE inhibitors do not seem to cause permanent toxic effects on chorioretinal tissue and photoreceptors. However, physicians should write down any visual symptom observed during PDE treatment and refer the patients to ophthalmologists.

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.

Avanafil for erectile dysfunction in elderly and younger adults: differential pharmacology and clinical utility

The treatment modalities of erectile dysfunction range from oral pharmacotherapy to intracavernosal injections, intraurethral pellets, vacuum erectile devices, and the surgical option of penile prosthesis insertion. Oral phosphodiesterase 5 inhibitors still remain the preferred treatment for patients since they are the least invasive, not to mention that they can be prescribed by non-urologists. Due to these factors, there has been development of newer drugs with fewer side effects. This is a review of the second generation phosphodiesterase 5 inhibitor, avanafil, looking into its pharmacology as well as its clinical utility. Avanafil’s faster onset and shorter duration of action has made it preferred as compared to other PDE5 inhibitors for patients with multiple comorbidities.

The effectiveness and safety of avanafil for erectile dysfunction: a systematic review and meta-analysis

OBJECTIVE

To compare the efficacy and safety between different dosages of avanafil for the treatment of erectile dysfunction (ED).

METHODS

PubMed, Cochrane Library, and Embase were searched to identify randomized controlled trials which compared avanafil with placebo, or compared different dosages of avanafil for ED. International Index of Erectile Function-Erectile Function domain score (IIEF-EF), Sexual Encounter Profile Question (SEP) questions 2 and 3, and adverse events were considered as the study outcomes. Both pairwise meta-analysis and network meta-analysis were carried out.

RESULTS

Five studies including 2225 patients were assessed. The pairwise meta-analysis suggested that avanafil was more effective than placebo in improving IIEF-EF (mean difference [MD]: 4.47; 95% confidence interval [CI]: 3.51 to 5.43), SEP-2 (MD: 17.41; 95% CI: 14.03 to 20.79), and SEP-3 (MD: 20.01; 95% CI: 22.98 to 37.22), with an evident dose-response relationship. The effectiveness was significantly different between the 50 mg and 100 mg groups, or between the 50 mg and 200 mg groups, for all outcomes. Overall, avanafil was associated with a significantly higher incidence of any adverse event (risk ratio [RR]: 2.56; 95% CI: 1.66 to 3.94), serious adverse event (RR: 2.78; 95% CI: 1.34 to 5.76), flushing (RR: 6.06; 95% CI: 3.37 to 10.88) and headache (RR: 7.54; 95% CI: 3.52 to 16.12) when compared with placebo. No significant difference in safety was found among various dosage groups.

CONCLUSIONS

Avanafil, from 50 to 200 mg, is effective and well tolerated for the treatment of ED, and an increase in dosage is associated with a significant rise in effectiveness but not with significantly more adverse events.

The selectivity and potency of the new PDE5 inhibitor TPN729MA

INTRODUCTION

TPN729MA is a newly developed phosphodiesterase type 5 inhibitor (PDE5i) for the treatment of erectile dysfunction, which offers potential for greater selectivity and longer duration of action than PDE5i in current clinical use.

AIM

We investigated the in vitro inhibitory potency and selectivity of TPN729MA on PDE isozymes, and its efficacy in animal models.

METHODS

The inhibition of 11 human recombinant PDEs by TPN729MA, sildenafil, and tadalafil were determined using radioimmunoassay. The effect of TPN729MA and sildenafil on intracavernous pressure (ICP), blood pressure (BP), and ICP/BP ratio were determined in a rat model of erection induced by electric stimulation and in a dog model of erection induced by sodium nitroprusside injection.

MAIN OUTCOME MEASURES

The main outcome measures were IC50 of TPN729MA, sildenafil, and tadalafil for PDE1-PDE11; maximum ICP; BP and ICP/BP ratio.

RESULTS

The IC50 of TPN729MA, sildenafil, and tadalafil for PDE5 was 2.28, 5.22, and 2.35 nM, respectively. TPN729MA showed 248, 366, 20, and 2671-fold selectivity against PDE1, PDE4, PDE6, and PDE11, respectively. TPN729MA showed excellent selectivity against PDE2, 3, 7, 8, 9, and 10 (>10,000-fold). In the rat model of erection, TPN729MA (5.0 and 2.5 mg/kg), but not sildenafil, significantly increased the maximum ICP compared with vehicle. Significantly increased ICP/BP was observed in the TPN729MA (5.0 mg/kg) group at all time points, in the TPN729MA (2.5 mg/kg) group at 75, 90, 105, and 120 minutes time points, and in sildenafil group at 75 and 90 minutes time points compared with vehicle. In the dog model of erection, TPN729MA and sildenafil significantly increased ICP and ICP/BP but showed no significant effect on BP compared with vehicle.

CONCLUSIONS

TPN729MA is a potent PDE5i with a balanced selectivity profile. TPN729MA shows excellent in vitro and in vivo potency, and a longer effect on erectile function than sildenafil in animal model.