Discovery and Optimization of Dihydroquinolin-2(1H)-ones as Novel Highly Selective and Orally Bioavailable Phosphodiesterase 5 Inhibitors for the Treatment of Pulmonary Arterial Hypertension

Phosphodiesterase 5 (PDE5) is a cGMP-specific hydrolytic enzyme and widely distributed in versatile tissues. PDE5 has been identified as a valid therapeutic target for treating erectile dysfunction and pulmonary arterial hypertension (PAH). Herein, a hit-to-lead structural optimizations were performed on the PDE1 inhibitor 10c, leading to compound 14b possessing great potency against PDE5A (IC50 = 3 nM) with high selectivity over PDE1, PDE2, PDE3, PDE4, PDE7, PDE8, PDE9, PDE10, and PDE11 by more than 1125-fold, and remarkable safety properties. Furthermore, oral administration of 14b (5.0 mg/kg) exerted much better pharmacodynamics effects on both mPAP (mean pulmonary artery pressure) and RVHI (index of right ventricle hypertrophy) than sildenafil citrate (10.0 mg/kg) in a monocrotaline-induced PAH rat model. Overall, these results proposed a novel highly selective PDE5 inhibitor 14b which could serve as a potential candidate for treatment of PAH.

Changes in Posterior Ocular Structures in Individuals Using Phosphodiesterase 5 Inhibitor

PURPOSE

To examine posterior ocular structures with optical coherence tomography (OCT) in individuals using a phosphodiesterase 5 inhibitor (PDI, tadalafil).

METHOD

This prospective study included 26 eyes of 26 patients who used 1 tablet of 5-mg tadalafil regularly every day for 1 month due to erectile dysfunction. The routine ophthalmological examinations of the participants were performed at the pre-tadalafil and post-tadalafil first-month visits. At both visits, OCT was used to measure the central retinal thickness (CRT), ganglion cell layer + inner plexiform layer (GCL + IPL) thicknesses, and peripapillary retinal nerve fiber layer (pRNFL; average and superior, temporal, inferior, and nasal quadrants) thicknesses. The disc area, rim area, average and vertical cup/disc ratio, and cup volume of the optic disc head were evaluated. Choroidal thickness was measured from five points: the subfoveal area and the nasal and temporal areas 500 and 1500 microns from the fovea. Choroidal vascular area values and choroidal vascular index (CVI) were calculated using a special binarization technique.

RESULTS

The mean age of the patients was 56 ± 8(range 34-72) years. No significant difference was detected in the CRT,GCL + IPL thicknesses,or pRNFL thicknesses in any of the quadrants before and after tadalafil use. The optic disc head measurements and choroidal thickness values measured from five points were similar between the two visits. The luminal choroidal area was 0.15 ± 0.04 mm2 before tadalafil use and 0.17 ± 0.05 mm2 after 1-month tadalafil use, with no statistically significant difference. The remaining choroidal vascular parameters, namely the stromal and total choroidal area and CVI values, were similar between the two visits.

CONCLUSION

This study showed no significant change in the posterior ocular structures in individuals using tadalafil regular daily use for 1 month due to erectile dysfunction.

Differences in ocular adverse events associated with phosphodiesterase-5 inhibitors: a real-world pharmacovigilance study

OBJECTIVE

Our study aims to characterize the ocular safety profiles of phosphodiesterase type 5 (PDE5) inhibitors and explore the differences among different PDE5 inhibitors.

METHODS

We analyzed reports on ocular adverse events associated with sildenafil, vardenafil and tadalafil submitted to the FDA Adverse Event Reporting System (FAERS) database from the first quarter of 2004 to the first quarter of 2023. Disproportionality analysis was conducted to evaluate reporting risk profiles.

RESULTS

Among 61,211 reports qualifying for analysis, 5,127 involved sildenafil, 832 vardenafil, and 3,733 tadalafil. All PDE5 inhibitors showed increased reporting odds ratios (ROR) for ocular adverse events, with vardenafil highest (ROR 4.47) followed by sildenafil and tadalafil. Key ocular adverse events included cyanopsia, optic ischemic neuropathy, visual field defects, unilateral blindness and blindness. Sildenafil showed the highest disproportionality for cyanopsia (ROR 1148.11) while vardenafil and tadalafil showed the highest disproportionality for optic ischemic neuropathy. Time-to-onset analysis also revealed significant differences, with sildenafil having a later median time-to-onset compared to vardenafil and tadalafil.

CONCLUSIONS

This comprehensive pharmacovigilance study reveals distinct patterns of ocular adverse events associated with PDE5 inhibitors. These findings contribute to a better understanding of the safety profiles of PDE5 inhibitors and may guide healthcare professionals in clinical decision-making.

Advances in understanding glaucoma pathogenesis: A multifaceted molecular approach for clinician scientists

Glaucoma, a leading cause of irreversible blindness worldwide, is a spectrum of neurodegenerative diseases characterized by the gradual deterioration of retinal ganglion cells (RGCs) and optic neuropathy. With complex etiology, glaucoma's major risk factors include elevated intraocular pressure (IOP), advanced age, ethnicity, systemic vascular factors, and genetic predisposition. By 2040, glaucoma is expected to affect over 110 million individuals aged 40 to 80, posing a significant economic burden. Glaucoma can be classified into open-angle, angle-closure, and developmental subtypes, with primary and secondary forms. The disease often progresses silently, gradually impairing the visual field (VF) until it reaches an advanced stage. Understanding the abnormal functional changes associated with glaucoma at the tissue, cellular, molecular, and genetic levels is crucial for comprehending its pathogenesis. This review examines the published data from the past two decades to shed light on the biological mechanisms underlying glaucoma development. The most evident factors in the development of glaucomatous optic neuropathy include elevated IOP, aging, genetic influences, followed by impaired ocular blood flow regulation. These factors are interconnected processes that lead to optic nerve damage, compromised circulation, and structural changes in glial and connective tissues. Contributing factors involve extracellular matrix remodeling, excitotoxicity, nitric oxide, oxidative stress, and neuroinflammation. Ultimately, all types of glaucoma result in RGC dysfunction and loss, causing irreversible visual impairment. While our understanding of glaucoma pathogenesis is evolving, further research is crucial for a comprehensive understanding of glaucoma pathogenesis and the development of effective treatments.

Central retinal vein and artery occlusion associated with sildenafil: a case report and review of the literature

BACKGROUND

Sildenafil is a selective phosphodiesterase type 5 inhibitor used for the treatment of erectile dysfunction and pulmonary hypertension. It is available over the counter in many countries. While there have been a few reports of retinal vascular occlusion following sildenafil consumption, most cases have other comorbidities as risk factors for the disease, and the exact causal role of this drug in these conditions remains unclear.

CASE PRESENTATION

We present the case of a healthy 32-year-old Iranian man who developed combined central retinal vein occlusion and retinal artery occlusion following sildenafil exposure. The patient underwent a hypercoagulative state workup for possible underlying risk factors. Additionally, we conducted a literature search on PubMed using the keywords: retinal vein occlusion AND Sildenafil OR Viagra, retinal artery occlusion AND Sildenafil OR Viagra, retinal vascular occlusion AND Sildenafil OR Viagra. To obtain more objective results in the reviews, we employed an adverse drug reaction possibility algorithm. The patient was found to be otherwise healthy, and ancillary tests were unremarkable. A literature review identified seven reports of retinal vascular occlusion following sildenafil use. In most of these cases, the role of sildenafil was not clearly established. To the best of our knowledge, our case achieved the highest score based on the algorithm compared with previous reports.

CONCLUSION

Sildenafil may be associated with severe retinal vascular accidents in otherwise healthy young individuals.

Chronic sildenafil citrate use decreases retinal vascular endothelial growth factor expression in diabetic rats: a pilot study

BACKGROUND

Sildenafil citrate (SC) attenuates endothelial dysfunction. However, its effects on diabetic retinopathy (DR), which is mainly a microvascular disease, remain unclear. Vascular endothelial growth factor (VEGF) is known to be a critical mediator of DR. Therefore, we investigated the effects of SC on diabetic retina by measuring VEGF levels.

METHODS

In this study, twenty-eight rats were divided into the following groups: group I, the control group; group II, rats with streptozotocin-induced diabetes; group III, rats with streptozotocin-induced diabetes receiving daily oral sildenafil at 1 mg/kg; and group IV, rats with streptozotocin-induced diabetes receiving high-dose daily sildenafil at 2.5 mg/kg. After 3 months, VEGF was measured in the retina specimen in one eye and the vitreous body in the other eye by immunohistochemistry and enzyme-linked immunosorbent assay, respectively.

RESULTS

We found that VEGF expression in the retina was low in all rats from groups I and IV and in 30% of rats from group III; 80% of rats in group II demonstrated high VEGF expression in the retinae (P < 0.001). VEGF concentrations in the vitreous body samples were 32 ± 2, 61 ± 4, 44 ± 5, and 36 ± 3 pg/l in groups I-IV, respectively (P < 0.001).

CONCLUSION

VEGF decreased significantly in the eyes of diabetic rats after chronic oral sildenafil citrate treatment. SC may have a modifying/attenuating effect on DR. However, further studies are needed to evaluate its use as an adjunctive treatment.

Knowledge, attitude, and practice (KAP) regarding erectile dysfunction disease and its medications among community pharmacy technicians in Mogadishu Somalia

Background

Erectile Dysfunction (ED) is the most common sexual dysfunction worldwide. This study is the first reported from Somalia to the best of our knowledge.

Objective

The current study aimed to assess knowledge, attitude, and practice (KAP) regarding erectile dysfunction disease and its medications among community pharmacy technicians in Mogadishu, Somalia.

Method

The current is a cross-sectional descriptive study conducted among pharmacy technicians in Mogadishu to assess their KAP regarding erectile dysfunction disease and its medications. A convenient sampling technique was used. A structured questionnaire contained 45 questions, including; demographic characteristics (4 items), the knowledge of erectile dysfunction disease and its medications (18 items), attitudes (5 items), and practice (15 items) were assessed among technicians. A total of 200 respondents participated in the study.

Results

Knowledge. 79 and 72.5% of technicians comprehended the condition of ED and whom it affects; however, about half did not know the underlying risk factors and complications associated with PDE5 inhibitors. Attitude: 77–85% of technicians believe medication requires prescriptions, medications may have complications, and quality medications are essential. Practice: 64% of technicians give ED medication with prescriptions, and 85% do not consult a physician. 64.5% of technicians always provide the same type of medication, and 63% do not give the same dose to each client. About half of the technicians also vend herbal medicines to clients, such as honey, fish, and sea urchins.

Conclusion

The findings of this study suggest pharmacy technicians have some knowledge, although not sufficient for understanding the risks and complications of medications. Technicians did not engage in good standard practices despite this knowledge and attitudes. These findings highlight the need for regulations to support good practice among pharmacy technicians and the quality, safety, and efficacy of medicines in Mogadishu by establishing the National Medicine Regulatory Authority.

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ED is the most common sexual dysfunction worldwide, approximately 150 million men are affected and impaired their quality of life including a negative psychosocial impact, feelings of shame, embarrassment, and depression.

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Community pharmacy technicians have often been regarded as an underused clinical care resource.

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There can be no one cure-all solution in encouraging men to present early with ED and accept complete lifestyle changes and treatment packages unless continuous medical education and capacity-building programs are promoted throughout primary care and at the national setting level.

Case Report: Central retinal artery occlusion following sildenafil intake

Purpose: To report a case of central retinal artery occlusion associated with sildenafil intake and briefly discuss its causative pathogenesis. Methods: A 50-year-old man with no premorbidities presented with symptoms of sudden severe visual field constriction in the left eye (LE). Best-corrected visual acuity in the LE was 20/25. Fundus examination and fluorescein angiography of the LE were suggestive of central retinal artery occlusion (CRAO) with cilioretinal artery sparing. Further investigation revealed that 100 mg of sildenafil had been taken for the first time three hours before the onset of symptoms. Results: The patient was treated promptly with intravenous acetazolamide, sublingual isosorbide dinitrate and ocular massage, but without visual recovery. No other associated systemic or local risk factors were found, and the case was classified as a potential complication of sildenafil. Conclusion: Although no direct link could be established, the aim of this report is to highlight the incidence and to consider this issue when evaluating any case of central retinal artery occlusion.

Free energy perturbation (FEP)-guided scaffold hopping

Scaffold hopping refers to computer-aided screening for active compounds with different structures against the same receptor to enrich privileged scaffolds, which is a topic of high interest in organic and medicinal chemistry. However, most approaches cannot efficiently predict the potency level of candidates after scaffold hopping. Herein, we identified potent PDE5 inhibitors with a novel scaffold via a free energy perturbation (FEP)-guided scaffold-hopping strategy, and FEP shows great advantages to precisely predict the theoretical binding potencies ΔG FEP between ligands and their target, which were more consistent with the experimental binding potencies ΔG EXP (the mean absolute deviations| Δ G FEP - Δ G EXP |  < 2 kcal/mol) than those ΔG MM-PBSA or ΔG MM-GBSA predicted by the MM-PBSA or MM-GBSA method. Lead L12 had an IC50 of 8.7 nmol/L and exhibited a different binding pattern in its crystal structure with PDE5 from the famous starting drug tadalafil. Our work provides the first report via the FEP-guided scaffold hopping strategy for potent inhibitor discovery with a novel scaffold, implying that it will have a variety of future applications in rational molecular design and drug discovery.

Unilateral acute anterior uveitis with macular edema following the use of sildenafil citrate in a patient with HLA-B27 positivity

Purpose

To present a case of acute anterior uveitis with macular edema associated with sildenafil citrate use in an HLA-B27 positive patient.

Observations

A 54-year-old Caucasian male presented at an ophthalmology tertiary center with complaint of pinkish discoloration, irritation, and photophobia in the left eye (OS). He noted that these symptoms appeared one day after using sildenafil for the first time to treat his erectile dysfunction. The patient had no significant ocular history besides refractive surgery in both eyes (OU) and his medical history was insignificant. Best-corrected visual acuity (BCVA) was 20/20 in the right eye (OD) and 20/25 in OS. Slit-lamp-examination (SLE) demonstrated trace cells and 1+ flare in the anterior chamber (AC) in OS and was nonrevealing in AC in OD. Spectral domain optical coherence tomography (SD-OCT) showed parafoveal subretinal hyperreflective deposits in OU. The patient was diagnosed with acute anterior uveitis (AAU) in the left eye and was placed on topical prednisolone acetate.At 2-week follow-up, the patient reported that his eye symptoms had improved since starting topical steroids but worsened again two days after he had used sildenafil for a second time. In OS, best-corrected visual acuity (BCVA) worsened to 20/40, and SLE revealed 1+ cells and 1+ flare in AC. SD-OCT revealed cystoid macular edema only in OS. Fluorescein angiography showed mild staining around the optic disc and significant macular leakage in OS and minimal macular leakage in OD. Uveitis evaluations revealed that the patient was human leukocyte antigen-27 (HLA-B27) positive. The patient was asked to remain off sildenafil and continue topical prednisolone acetate. At 3-month follow-up, BCVA improved to 20/20 in OS with no evidence of active inflammation.

Conclusions and importance

Sildenafil citrate use might be associated with new onset of intraocular inflammation in predisposed patients. Further studies are necessary to establish this relationship.

Central Retinal Artery Occlusion Associated with Sildenafil Overdose

Background

To report a patient with central retinal artery occlusion (CRAO) associated with sildenafil overdose. Case Presentation. A forty-two-year-old male presented three hours after sudden painless visual loss in the right eye. BCVA was counting finger in two meters, and relative afferent pupillary defect was positive. Fundus examination revealed retinal whiteness except in a limited area of papillomacular bundle and cherry red spot. He consumed two 100 mg film-coated sildenafil tablet (Vizarsin, Krka, d.d., Novo mesto, Slovenia) twelve hours apart, and the last one was six hours before visual loss. He was diagnosed with CRAO with cilioretinal artery sparing. Although we did not find any emboli, anterior chamber paracentesis was done. Four weeks later, BCVA improved to 20/80, with resolving of retinal edema. Cardiovascular, carotid arteries, and neurologic evaluations were negative for any predisposing factor.

Conclusion

CRAO is a vision threatening condition that might be associated with the overdose of sildenafil.

Visual Side Effects Linked to Sildenafil Consumption: An Update

Phosphodiesterase type 5 (PDE5) inhibitors such as Viagra^® (sildenafil citrate) have demonstrated efficacy in the treatment of erectile dysfunction (ED) by inducing cyclic guanosine monophosphate (cGMP) elevation followed by vasodilation and increased blood flow. It also exerts minor inhibitory action against PDE6, which is present exclusively in rod and cone photoreceptors. The effects of sildenafil on the visual system have been investigated in a wide variety of clinical and preclinical studies due to the fact that a high dose of sildenafil may cause mild and transient visual symptoms in some patients. A literature review was performed using PubMed, Cochrane Library and Clinical Trials databases from 1990 up to 2020, focusing on the pathophysiology of visual disorders induced by sildenafil. The aim of this review was not only to gather and summarize the information available on sildenafil clinical trials (CTs), but also to spot subpopulations with increased risk of developing undesirable visual side effects. This PDE inhibitor has been associated with transient and reversible ocular side effects, including changes in color vision and light perception, blurred vision, photophobia, conjunctival hyperemia and keratitis, and alterations in the electroretinogram (ERG). Sildenafil may induce a reversible increase in intraocular pressure (IOP) and a few case reports suggest it is involved in the development of nonarteritic ischemic optic neuropathy (NAION). Reversible idiopathic serous macular detachment, central serous retinopathy and ERG disturbances have been related to the significant impact of sildenafil on retinal perfusion. So far, sildenafil does not seem to cause permanent toxic effects on chorioretinal tissue and photoreceptors as long as the therapeutic dose is not exceeded and is taken under a physician’s direction to treat a medical condition. However, the recreational use of sildenafil can lead to harmful side effects, including vision changes.

Effects of phosphodiesterase type 5 inhibitors on choroid and ocular vasculature: a literature review

To provide information on the effects of phosphodiesterase type 5 (PDE5) inhibitors on choroidal vessels and central serous chorioretinopathy (CSC) and possible implications for development of exudative age-related macular degeneration (AMD). Two independent investigators conducted a qualitative review of PubMed to identify studies on the choroidal effect of PDE5 inhibitors in June 2019. The search used key words that included PDE5 inhibitors, sildenafil, tadalafil, vardenafil, choroid, choroidal flow, choroidal vessels, choroidal thickness, CSC, AMD or a combination. Only studies which assessed choroidal findings were included. Many ocular diseases are related to changes in choroidal thickness and perfusion. Patients with AMD, who have decreased choroidal perfusion, may manifest more severely diminished choroidal ability to deliver oxygen and other metabolites to the retina, leading to growth of neovascular tissue. As a result of this engorgement of the choroidal vasculature, some patients may have leakage across the retinal pigment epithelium (RPE) and accumulation of subretinal fluid, resulting in CSC. Transient visual symptoms, i.e., changes in color perception and increased light sensitivity, are well-known adverse effects, but there have been rare reports of vision-threatening ocular complications in users of PDE5 inhibitors, such as nonarteritic anterior ischemic optic neuropathy and cilioretinal artery occlusion. The choroid is a vascular tissue analogous in many respects to the corpus cavernosum, and PDE5 inhibitors may increase the choroidal thickness and perfusion. While it is intuitively obvious that thickness of the choroid alone does not guarantee better choriocapillaris oxygenation, it is a reasonable step towards ameliorating ischemia. These drugs have numerous physiologic effects on the choroid related to blood flow, such as clinical consequences in CSC and AMD.

Risk of nonarteritic ischaemic optic neuropathy with phosphodiesterase type 5 inhibitors: a systematic review and meta-analysis

The development of nonarteritic anterior ischaemic optic neuropathy has been described to phosphodiesterase type 5 inhibitors. The aim of this systematic review and meta-analysis was to assess the risk of nonarteritic anterior ischaemic optic neuropathy associated with phosphodiesterase type 5 inhibitors exposure. A literature search was performed at MEDLINE, EMBASE, Toxline and VigiBase. Randomized controlled trials, observational studies, case reports and spontaneous reports describing nonarteritic anterior ischaemic optic neuropathy associated with phosphodiesterase type 5 inhibitors exposure were included. The risk of bias was assessed according to Centre for Reviews and Dissemination's (CRD) guidance. Data were analysed using descriptive statistics and meta-analysis. Four observational studies, 50 case reports and 608 spontaneous reports were identified. All observational studies evaluated males treated for erectile dysfunction. Treatment with phosphodiesterase type 5 inhibitors is not associated with an increased risk of definitive nonarteritic anterior ischaemic optic neuropathy [odds ratio (OR) 1.16; 95% CI 0.89, 1.52, p = 0.046; I²  = 62.6%]. The methodological quality was assessed as good for three studies. Among case reports, 12 (23%) patients did not have risk factors to develop nonarteritic anterior ischaemic optic neuropathy. Thirty-nine (78%) patients were treated for erectile dysfunction. A regular administration of phosphodiesterase type 5 inhibitors was observed in 24 (48%) case reports. All case reports were assessed as higher risk of bias. According to the available evidence, the treatment with phosphodiesterase type 5 inhibitors was not found to be associated with nonarteritic anterior ischaemic optic neuropathy. Further research is needed to study such association, including possible confounding factors.

Erectile dysfunction drugs altered the activities of antioxidant enzymes, oxidative stress and the protein expressions of some cytochrome P450 isozymes involved in the steroidogenesis of steroid hormones

OBJECTIVES

Infertility is a global health problem with about 15 percent of couples involved. About half of the cases of infertility are related to male-related factors. A major cause of infertility in men is oxidative stress, which refers to an imbalance between levels of reactive oxygen species (ROS) and antioxidants. Erectile dysfunction drugs (EDD), known as phosphodiesterase inhibitors (PDEIs), have been used for the treatment of ED. It has been shown that oxidative stress plays an important role in the progression of erectile dysfunction. Oxidative stress can be alleviated or decreased by non-antioxidants and antioxidant enzymes. The present study was undertaken to determine if these compounds could have a role in the incidence of infertility, especially after long-term use. Therefore, the present study aims to investigate the effect of EDD on the activities of antioxidant enzymes, free radical levels as well as the protein expression of different cytochrome P450 isozymes involved in the steroidogenesis of different hormones. In addition, the activity of both 17β-hydroxysteroid dehydrogenase and 17-ketosteroid reductase were assayed. The architectures of both livers and testes cells were investigated under the influence of EDD.

METHODS

A daily dose of Sildenafil (1.48 mg/kg), Tadalafil (0.285 mg/kg) and Vardenafil (0.285 mg/kg) were administered orally to male rabbits for 12 week. Western immunoblotting, ELISA, spectrophotometric and histopathological techniques were used in this study.

RESULTS

The present study showed that Sildenafil, Vardenafil, and Tadalafil treatments significantly decreased the levels of glutathione and free radicals in both livers and testes of rabbits. Also, Vardenafil and Sildenafil induced the activity of superoxide dismutase and catalase whereas, glutathione S-transferase, glutathione reductase, and glutathione peroxidase activities inhibited in livers of rabbits. The protein expression of cytochrome P450 isozymes (CYP 11A1, 21A2, and 19C) which are involved in the steroidogenesis was markedly changed in both livers and testes of rabbits after their treatments for 12 weeks. After the treatment of rabbits with these medication, the protein expression of CYP11A1 was slightly down-regulated in both livers and testes except Sildenafil up-regulated such protein expression. In addition, the protein expressions of CYP11A1 and CYP 19C in both livers and testes were down-regulated after treatment of rabbits with Sildenafil, Vardenafil, and Tadalafil for 12 weeks. Also, these drugs inhibited the activity of both 17β-hydroxysteroid dehydrogenase and 17-ketosteroid reductase in testes of rabbits. Moreover, Sildenafil, Vardenafil, and Tadalafil-treated rabbits showed a decrease in spermatocytes and the number of sperms in the testes.

CONCLUSIONS

It is concluded that ED drugs induced the activities of both SOD and catalase which consequently decreased MDA level. Decrement in MDA levels and oxidative stress could therefore sustain the erection for a long period of time. On the other hand, it is not advised to use these drugs for a long-term since the protein expressions of CYP isozymes involved in steroidogenesis as well as the numbers of spermatocytes in testes were decreased.

Phosphodiesterase-2 Inhibitor Bay 60-7550 Ameliorates Aβ-Induced Cognitive and Memory Impairment via Regulation of the HPA Axis

The dysfunction of the hypothalamus-pituitary-adrenal (HPA) axis is often seen in Alzheimer's disease (AD) patients with cognitive deficits. Selective inhibition of phosphodiesterase (PDE) 4 and 5 has already proven to be effective in reducing beta-amyloid 1-42 (Aβ1-42)-mediated pathology by regulating corticotropin-releasing factor (CRF) and glucocorticoid receptor (GR) expression, suggesting that PDE-dependent signaling is involved in Aβ1-42-induced HPA axis dysfunction. However, nausea and vomiting are the side effects of some PDE4 inhibitors, which turn our attention to other PDEs. PDE2 are highly expressed in the hippocampus and cortex, which associate with learning and memory, but not in the area postrema that would cause vomiting. The present study suggested that microinjection of Aβ1-42 to the intracerebroventricle induced learning and memory impairments and dysregulation of the HPA axis by increased expression of CRF and GR. However, the PDE2 inhibitor Bay 60-7550 significantly ameliorated the learning and memory impairment in the Morris water maze (MWM) and step-down passive avoidance tests. The Aβ1-42-induced increased CRF and GR levels were also reversed by the treatment with Bay 60-7550. These Bay 60-7550's effects were prevented by pretreatment with the PKG inhibitor KT5823. Moreover, the Bay 60-7550-induced downstream phosphorylation of cyclic AMP response element binding (pCREB) and brain-derived neurotrophic factor (BDNF) expression was also prevented (or partially prevented) by KT5823 or the PKA inhibitor H89. These results may lead to the discovery of novel strategies for the treatment of age-related cognitive disorders, such as AD, which affects approximately 44 million people worldwide.

A Multi-Biochemical and In Silico Study on Anti-Enzymatic Actions of Pyroglutamic Acid against PDE-5, ACE, and Urease Using Various Analytical Techniques: Unexplored Pharmacological Properties and Cytotoxicity Evaluation

In the current study, pyroglutamic acid (pGlu), a natural amino acid derivative, has efficiently inhibited the catalytic activities of three important enzymes, namely: Human recombinant phosphodiesterase-5A1 (PDE5A1), human angiotensin-converting enzyme (ACE), and urease. These enzymes were reported to be associated with several important clinical conditions in humans. Radioactivity-based assay, spectrophotometric-based assay, and an Electrospray Ionization-Mass Spectrometry-based method were employed to ascertain the inhibitory actions of pGlu against PDE5A1, ACE, and urease, respectively. The results unveiled that pGlu potently suppressed the activity of PDE5A1 (half-maximal inhibitory concentration; IC₅₀ = 5.23 µM) compared with that of standard drug sildenafil citrate (IC₅₀ = 7.14 µM). Moreover, pGlu at a concentration of 20 µg/mL was found to efficiently inhibit human ACE with 98.2% inhibition compared with that of standard captopril (99.6%; 20 µg/mL). The urease-catalyzed reaction was also remarkably inactivated by pGlu and standard acetohydroxamic acid with IC₅₀ values of 1.8 and 3.9 µM, respectively. Remarkably, the outcome of in vitro cytotoxicity assay did not reveal any significant cytotoxic properties of pGlu against human cervical carcinoma cells and normal human fetal lung fibroblast cells. In addition to in vitro assays, molecular docking analyses were performed to corroborate the outcomes of in vitro results with predicted structure-activity relationships. In conclusion, pGlu could be presented as a natural and multifunctional agent with promising applications in the treatment of some ailments connected with the above-mentioned anti-enzymatic properties.

[Acute monocular loss of vision : Differential diagnostic considerations apart from the internistic etiological clarification]

We report the case of acute painless monocular loss of vision in a 53-year-old man. An interdisciplinary etiological evaluation remained without pathological findings with respect to arterial branch occlusion. A reevaluation of the patient history led to a possible association with the administration of phosphodiesterase type 5 inhibitor (PDE5 inhibitor). A critical review of the literature on PDE5 inhibitor administration with ocular participation was performed.

Ocular Side Effects of Systemic Drugs Used in Dermatology

Some systemically used drugs in managing dermatologic disorders have associated severe side effects, of which eye involvement is very significant. There are various mechanisms for these drugs to cause damage to the eye. The damage to the eye can be acute as in Stevens–Johnson syndrome or chronic as with chloroquine and hydroxychloroquine toxicity. Knowledge about these drugs and information about the mechanisms and types of damage to the eye are essential. It is also important to understand the monitoring mechanisms to diagnose early and limit the damage. Newer investigative tools, especially the imaging techniques help us to diagnose the adverse effects at an early stage. All these issues are discussed in brief here.

The nitric oxide-guanylate cyclase pathway and glaucoma

Glaucoma is a prevalent optic neuropathy characterized by the progressive dysfunction and loss of retinal ganglion cells (RGCs) and their optic nerve axons, which leads to irreversible visual field loss. Multiple risk factors for the disease have been identified, but elevated intraocular pressure (IOP) remains the primary risk factor amenable to treatment. Reducing IOP however does not always prevent glaucomatous neurodegeneration, and many patients progress with the disease despite having IOP in the normal range. There is increasing evidence that nitric oxide (NO) is a direct regulator of IOP and that dysfunction of the NO-Guanylate Cyclase (GC) pathway is associated with glaucoma incidence. NO has shown promise as a novel therapeutic with targeted effects that: 1) lower IOP; 2) increase ocular blood flow; and 3) confer neuroprotection. The various effects of NO in the eye appear to be mediated through the activation of the GC- guanosine 3:5'-cyclic monophosphate (cGMP) pathway and its effect on downstream targets, such as protein kinases and Ca²⁺ channels. Although NO-donor compounds are promising as therapeutics for IOP regulation, they may not be ideal to harness the neuroprotective potential of NO signaling. Here we review evidence that supports direct targeting of GC as a novel pleiotrophic treatment for the disease, without the need for direct NO application. The identification and targeting of other factors that contribute to glaucoma would be beneficial to patients, particularly those that do not respond well to IOP-dependent interventions.

ACUTE SEROUS RETINAL DETACHMENT IN IDIOPATHIC PULMONARY ARTERIAL HYPERTENSION

PURPOSE

To report the case of a 44-year-old woman with acute transient visual loss likely because of idiopathic pulmonary arterial hypertension.

METHODS

Case report imaged with fundus photographs, spectral-domain optical coherence tomography, fundus autofluorescence, and fluorescein and indocyanine green angiographies.

RESULTS

The patient complained of unilateral vision loss with metamorphopsia. Fundus examination of the right eye showed serous macular detachment and retinal folds. Fluorescein angiography and indocyanine green angiography showed delayed choroidal filling with multiple choroidal perfusion defects and dye leakage from areas of multiple pigment epithelial detachments. Spectral-domain optical coherence tomography showed a thick choroid. Medical history included idiopathic pulmonary arterial hypertension treated with tadalafil. Ocular signs regressed spontaneously within 1 week.

CONCLUSION

Transient severe choroidal filling defects with subretinal exudation may be observed in idiopathic pulmonary arterial hypertension. The present case raised the questions of the triggering factor of the acute decompensation of the blood-retinal barrier and the cause of its spontaneous regression.

Are phosphodiesterase type 5 inhibitors associated with increased risk of melanoma?: A systematic review and meta-analysis

Phosphodiesterase type 5 (PDE5) inhibitors are recommended for patients with erectile dysfunction by American Urological Association and European Association Urology guidelines. However, recent researches have shown that PDE5 inhibitors may lead to increased melanoma risk. Thus, we aimed to explore whether PDE5 inhibitors are associated with increased melanoma risk based on published literatures.We conducted a systematic online search on PubMed, EMBASE, Cochrane Library, Chinese Biochemical Literature, China National Knowledge Infrastructure, and Chinese Science and Technology Periodical databases to identify the related studies. Odds ratios (ORs), risk ratios, and hazard ratios with 95% confidence intervals (CIs) were extracted and calculated to assess the strength of associations between PDE5 inhibitors and melanoma risk. We also extracted the basal cell carcinoma (BCC) to validate the association in this study.We included 5 studies containing 100,932 participants in our systematic review and meta-analysis. The calculated results suggested positive results of PDE5 inhibitors on melanoma risk (OR: 1.13; 95%CI: 1.04-1.23). For localized and nonlocalized melanoma, the results were different (OR: 1.22; 95%CI: 1.04-1.43 for localized melanoma) (OR: 0.62; 95%CI: 0.39-0.98 for nonlocalized melanoma). It also showed that PDE5 inhibitors were associated with increased BCC risk (OR: 1.18; 95%CI: 1.11-1.27).The association between PDE5 inhibitors and melanoma might not be causal due to potential bias (patient selection, and so on) and limitations.

Use of phosphodiesterase inhibitors and prevalence of self-reported glaucoma in the United States

Objective

While decreased ocular blood flow is thought to be a possible contributor to glaucoma pathogenesis, it is unclear what role systemic phosphodiesterase inhibitors (PDEi) play. We performed a cross-sectional study of a nationally representative sample of the U.S. population to investigate the relationship between the most commonly used PDEi, sildenafil and theophylline, and self-reported glaucoma.

Methods

We used the National Health and Nutrition Examination Survey 2005–2008 cycles for this observational study. 7,042 participants, aged 40 years and over, responded to a survey item on glaucoma status and were included in the analysis. Multivariable logistic regression models were constructed to evaluate the association between at least 1 year of self-reported PDEi use and prevalent glaucoma. Regressions were adjusted for potential confounding variables, including demographics, socioeconomic status, and general health conditions, and accounted for the complex design of the survey. Sample weights were constructed and used to ensure the generalizability of results.

Results

482 respondents self-reported a diagnosis of glaucoma, of which 11 used sildenafil and 20 used theophylline for at least 1 year. Covariates significantly associated with higher odds of glaucoma prevalence in univariable analyses included older age, black race, former smoking status, diabetes, hyperlipidemia, myocardial infarction, and stroke. Conversely, higher education and income were significantly associated with lower odds of glaucoma prevalence. In regression analyses adjusted for demographic and socioeconomic variables, sildenafil (OR = 4.90, CI: 1.24–19.27, p = 0.025) and theophylline (OR = 3.15, CI: 1.46–6.80, p = 0.005) were significantly associated with higher odds of self-reported glaucoma. These associations held after further adjustment with general health behaviors and conditions for both sildenafil and theophylline.

Conclusions

Use of sildenafil and theophylline for one or more years was associated with greater prevalence of self-reported glaucoma, a finding which requires further prospective study to assess causality and possible mechanisms of action.

Sildenafil in Infants and Children

Pulmonary arterial hypertension (PAH) management has been transformed in recent times with the advent of cheap and effective diagnostic tools and therapy. Sildenafil, a phosphodiesterase-V inhibitor, has been at the centre of this treatment, and its success in treating PAH has led to its widespread uptake in adult and paediatric pulmonary hypertension (PH), as a first line treatment choice. This might apply to persistent pulmonary hypertension of the newborn (PPHN) or bronchopulmonary dysplasia, as well as to more complex diseases, such as idiopathic pulmonary hypertension. Although recent data regarding long-term mortality and the repeal of Food and Drug Administration (FDA) approval has complicated the issue, Sildenafil continues to be the major treatment option for paediatric PH for patients in a variety of contexts, and this does not seem likely to change in the foreseeable future. In this review, we provide a summary of pulmonary hypertension in infants and children and the use of Sildenafil for such diseases.

Sildenafil and retinopathy of prematurity risk in very low birth weight infants

OBJECTIVE

To examine the effect of sildenafil therapy on development of severe retinopathy of prematurity (ROP) requiring surgical intervention in premature infants.

STUDY DESIGN

We identified premature infants who were discharged from Pediatrix Medical Group neonatal intensive care units from 2003 to 2012 and who received an ophthalmologic exam. We matched each infant exposed to sildenafil before first eye exam to three nonexposed infants using propensity scoring to control for differences in baseline infant characteristics. We evaluated the association between sildenafil exposure and development of severe ROP using conditional logistic regression.

RESULT

Of the 57 815 infants meeting inclusion criteria, 88 were exposed to sildenafil. We matched 81/88 (92%) sildenafil-exposed with 243 nonexposed infants. There was no difference in the proportion of infants who developed severe ROP in the sildenafil-exposed vs nonexposed groups (17/81 (21%) vs 38/243 (16%), P=0.27). On adjusted analysis, there was no difference in severe ROP in the sildenafil-exposed vs nonexposed infants (odds ratio=1.46, 95% confidence interval=0.76 to 2.82, P=0.26).

CONCLUSION

We did not observe an association between risk of severe ROP and sildenafil exposure before first eye exam in this cohort of premature infants.

Poppers Maculopathy: Complete Restitution of Macular Changes in OCT after Drug Abstinence

BACKGROUND

"Poppers" is a slang term for a group of alkyl nitrites that are used as recreational drugs. Their inhalative intoxication leads to muscle relaxation, analgesia, and euphoria. Maculopathy is a rare but serious side-effect.

PATIENTS/METHODS

Clinical, imaging, and electrophysiological findings of seven patients with maculopathy after consumption of poppers were presented.

RESULTS

All seven patients were male with a median age of 35 years (range 28-45 years), the median duration of periodical poppers use until the onset of symptoms was 9.8 years (one day to 25 years). Five of seven patients were HIV-positive, one patient was negative, and the HIV-status of one patient was unknown. Median average of visual acuity at presentation was 20/30 in each eye. In all patients, optical coherence tomography (OCT) showed pathognomonic alterations of the outer foveal retina. One patient showed an almost complete restitution of the maculopathy six months after cessation of drug use and following the oral intake of Lutein. Imaging alterations returned to normal and visual acuity recovered from 20/50 and 20/30 (right and left eye, respectively) to 20/20 on both eyes. Follow up of two other cases showed no relevant functional decline or improvement.

DISCUSSION

Toxic maculopathy due to the consumption of poppers is an important differential diagnosis in acute visual loss without clinico-morphological correlate. Optical coherence tomography is the only reliable diagnostic tool in these cases. Complete recovery of visual function and macular morphology is rare, even after cessation of drug abuse. Oral lutein therapy may have a beneficial effect.

Optic neuropathy associated with the use of over-the-counter sexual enhancement supplements

This case report details an association of the use of over-the-counter sexual enhancement supplements with atypical optic neuropathy. A 42-year-old man presented with right-sided headache and vision loss of the right eye, which deteriorated to a single quadrant of hand motion over 11 days. Serial orbital magnetic resonance imaging scans demonstrated progressive orbital optic nerve enhancement extending into the optic canal despite high-dose steroid treatment. The patient eventually admitted to using several over-the-counter sexual enhancement supplements prior to the onset of symptoms and throughout the course of his steroid treatment, which he subsequently discontinued. His vision improved to 20/200 with an expanded visual field. Anterior ischemic optic neuropathy has been reported in association with phosphodiesterase (PDE)-5 inhibitor use, but visual loss in association with unregulated sexual enhancement supplements has not been studied. While one case cannot establish association, our case is suggestive of potential dangers of over-the-counter sexual enhancement supplements, which may contain PDE-5 inhibitors, “male hormones,” and “substances that enhance blood production.” The case also underscores the importance of obtaining a careful history of supplements in patients with optic neuropathies.

Cyclic nucleotide phosphodiesterases: important signaling modulators and therapeutic targets

By catalyzing hydrolysis of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), cyclic nucleotide phosphodiesterases are critical regulators of their intracellular concentrations and their biological effects. As these intracellular second messengers control many cellular homeostatic processes, dysregulation of their signals and signaling pathways initiate or modulate pathophysiological pathways related to various disease states, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication, chronic obstructive pulmonary disease, and psoriasis. Alterations in expression of PDEs and PDE-gene mutations (especially mutations in PDE6, PDE8B, PDE11A, and PDE4) have been implicated in various diseases and cancer pathologies. PDEs also play important role in formation and function of multimolecular signaling/regulatory complexes, called signalosomes. At specific intracellular locations, individual PDEs, together with pathway-specific signaling molecules, regulators, and effectors, are incorporated into specific signalosomes, where they facilitate and regulate compartmentalization of cyclic nucleotide signaling pathways and specific cellular functions. Currently, only a limited number of PDE inhibitors (PDE3, PDE4, PDE5 inhibitors) are used in clinical practice. Future paths to novel drug discovery include the crystal structure-based design approach, which has resulted in generation of more effective family-selective inhibitors, as well as burgeoning development of strategies to alter compartmentalized cyclic nucleotide signaling pathways by selectively targeting individual PDEs and their signalosome partners.

Inhibition of phosphodiesterase 2 reverses impaired cognition and neuronal remodeling caused by chronic stress

Chronic stress and neuronal vulnerability have recently been recognized as factors contributing to cognitive disorders. One way to modify neuronal vulnerability is through mediation of phosphodiesterase 2 (PDE2), an enzyme that exerts its action on cognitive processes via the control of intracellular second messengers, cGMP and, to a lesser extent, cAMP. This study explored the effects of a PDE2 inhibitor, Bay 60-7550, on stress-induced learning and memory dysfunction in terms of its ramification on behavioral, morphologic, and molecular changes. Bay 60-7550 reversed stress-induced cognitive impairment in the Morris water maze, novel object recognition, and location tasks (object recognition test and/or object location test), effects prevented by treatment with 7-NI, a selective inhibitor of neuronal nitric oxide synthase; MK801, a glutamate receptor (NMDAR) inhibitor; myr-AIP, a CaMKII inhibitor; and KT5823, a protein kinase G inhibitor. Bay 60-7550 also ameliorated stress-induced structural remodeling in the CA1 of the hippocampus, leading to increases in dendritic branching, length, and spine density. However, the neuroplasticity initiated by Bay 60-7550 was not seen in the presence of 7-NI, MK801, myr-AIP, or KT5823. PDE2 inhibition reduced stress-induced extracellular-regulated protein kinase activation and attenuated stress-induced decreases in transcription factors (e.g., Elk-1, TORC1, and CREB phosphorylation) and plasticity-related proteins (e.g., Egr-1 and brain-derived neurotrophic factor). Pretreatment with inhibitors of NMDA, CaMKII, neuronal nitric oxide synthase, and protein kinase G (or protein kinase A) blocked the effects of Bay 60-7550 on cGMP or cAMP signaling. These findings indicate that the effect of PDE2 inhibition on stress-induced memory impairment is potentially mediated via modulation of neuroplasticity-related NMDAR-CaMKII-cGMP/cAMP signaling.

Acute onset of bilateral visual loss during sildenafil therapy in a young infant with congenital heart disease

We report a case of posterior non-arteritic ischaemic optic neuropathy (NAION) causing bilateral visual loss in a 7-month-old female infant, after a therapeutic course with sildenafil, a phosphodiesterase type 5 inhibitors (PDE5i). The patient was affected by a complex cyanotic congenital heart defect and had undergone cavopulmonary anastomosis (Glenn operation) 3 months ago. After 2 months of recurring chylothorax, a course of oral sildenafil was administered, with the hypothesis that pulmonary vascular resistances were increased. Approximately 4 weeks later the acute onset of visual worsening and poor pupillary light reflex prompted the diagnosis of posterior NAION. Despite a rapid cessation of PDE5i and systemic treatment with corticosteroids, no visual recovery was noticed at 2-year follow-up. NAION has been associated with PDE5i therapy in adults, but to the best of our knowledge it is almost unheard of in children. We suggest close monitoring of visual function in children undergoing treatment with sildenafil.

Sildenafil use and increased risk of incident melanoma in US men: a prospective cohort study

IMPORTANCE

The RAS/RAF/mitogen-activated protein kinase and extracellular signal-regulated kinase (ERK) kinase/ERK cascade plays a crucial role in melanoma cell proliferation and survival. Sildenafil citrate (Viagra) is a phosphodiesterase (PDE) 5A inhibitor commonly used for erectile dysfunction. Recent studies have shown that BRAF activation down-regulates PDE5A levels, and low PDE5A expression by BRAF activation or sildenafil use increases the invasiveness of melanoma cells, which raises the possible adverse effect of sildenafil use on melanoma risk.

OBJECTIVE

To evaluate the association between sildenafil use and risk of incident melanoma among men in the United States.

DESIGN, SETTING, AND PARTICIPANTS

Our study is a prospective cohort study. In 2000, participants in the Health Professionals' Follow-up Study were questioned regarding sildenafil use for erectile dysfunction. Participants who reported cancers at baseline were excluded. A total of 25,848 men remained in the analysis.

MAIN OUTCOMES AND MEASURES

The incidence of skin cancers, including melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC), was obtained in the self-reported questionnaires biennially. The diagnosis of melanoma and SCC was pathologically confirmed.

RESULTS

We identified 142 melanoma, 580 SCC, and 3030 BCC cases during follow-up (2000-2010). Recent sildenafil use at baseline was significantly associated with an increased risk of subsequent melanoma with a multivariate-adjusted hazard ratio (HR) of 1.84 (95% CI, 1.04-3.22). In contrast, we did not observe an increase in risk of SCC (HR, 0.84; 95% CI, 0.59-1.20) or BCC (1.08; 0.93-1.25) associated with sildenafil use. Moreover, erectile function itself was not associated with an altered risk of melanoma. Ever use of sildenafil was also associated with a higher risk of melanoma (HR, 1.92; 95% CI, 1.14-3.22). A secondary analysis excluding those reporting major chronic diseases at baseline did not appreciably change the findings; the HR of melanoma was 2.24 (95% CI, 1.05-4.78) for sildenafil use at baseline and 2.77 (1.32-5.85) for ever use.

CONCLUSIONS AND RELEVANCE

Sildenafil use may be associated with an increased risk of developing melanoma. Although this study is insufficient to alter clinical recommendations, we support a need for continued investigation of this association.

Advances in targeting cyclic nucleotide phosphodiesterases

Cyclic nucleotide phosphodiesterases (PDEs) catalyse the hydrolysis of cyclic AMP and cyclic GMP, thereby regulating the intracellular concentrations of these cyclic nucleotides, their signalling pathways and, consequently, myriad biological responses in health and disease. Currently, a small number of PDE inhibitors are used clinically for treating the pathophysiological dysregulation of cyclic nucleotide signalling in several disorders, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication and chronic obstructive pulmonary disease. However, pharmaceutical interest in PDEs has been reignited by the increasing understanding of the roles of individual PDEs in regulating the subcellular compartmentalization of specific cyclic nucleotide signalling pathways, by the structure-based design of novel specific inhibitors and by the development of more sophisticated strategies to target individual PDE variants.

Discovery of 3-(4-hydroxybenzyl)-1-(thiophen-2-yl)chromeno[2,3-c]pyrrol-9(2H)-one as a phosphodiesterase-5 inhibitor and its complex crystal structure

Phosphodiesterase-5 (PDE5) inhibitors have been approved for the treatment of erectile dysfunction and pulmonary hypertension, but enthusiasm on discovery of PDE5 inhibitors continues for their potential new applications. Reported here is discovery of a series of new PDE5 inhibitors by structure-based design, molecular docking, chemical synthesis, and enzymatic characterization. The best compound, 3-(4-hydroxybenzyl)-1-(thiophen-2-yl)chromeno[2,3-c]pyrrol-9(2H)-one (57), has an IC₅₀ of 17 nM against the PDE5 catalytic domain and good selectivity over other PDE families. The crystal structure of the PDE5 catalytic domain in complex with 57 was determined at 2Å resolution and showed that 57 occupies the same pocket as other PDE5 inhibitors, but has a different binding pattern in detail. On the basis of the binding pattern of 57, a novel scaffold can be proposed as a candidate of PDE inhibitors.

Toxic optic neuropathies

PURPOSE OF REVIEW

Many causes of toxic optic neuropathy have been described to date and novel causes of toxicity are continuously being added to the current literature. The pathophysiological basis for the toxicity or a direct causal relationship is yet to be determined for many of these agents. This review highlights the reports made over the last year about the commonly reported agents, with emphasis on the mechanisms of toxicity.

RECENT FINDINGS

Mitochondria of retinal ganglion cells and papillomacular bundle in particular could be the common target of many causes of toxic optic neuropathy, if not all. Agents or their metabolites responsible for the toxicity seem to interfere with the oxidative phosphorylation in mitochondria, causing a buildup of reactive oxidation species, energy depletion, oxidative stress, and activation of apoptosis.

SUMMARY

Further data are still necessary to understand how some of the usual suspects cause damage to the optic nerve or whether they indeed cause damage or not. A basic algorithm, as proposed, could be a useful addition to discriminate the novel causes of toxic optic neuropathy.

VIDEO ABSTRACT

See the Supplemental Digital Content 1 (http://links.lww.com/COOP/A11).

Pharmacologic therapy for erectile dysfunction and its interaction with the cardiovascular system

Phosphodiesterase (PDE) enzymes are widely distributed throughout the body, having numerous effects and functions. The PDE type 5 (PDE5) inhibitors are widely used to treat erectile dysfunction (ED). Recent, intense preclinical and clinical research with PDE5 inhibitors has shed light on new mechanisms and has revealed a number of pleiotropic effects on the cardiovascular (CV) system. To date, PDE5 inhibition has been shown to be effective for the treatment of idiopathic pulmonary arterial hypertension, and both sildenafil and tadalafil are approved for this indication. However, current or future PDE5 inhibitors have the potential of becoming clinically useful in a variety of CV conditions such as heart failure, coronary artery disease, and hypertension. The present review discusses recent findings regarding pharmacologic treatment of ED and its interaction with the CV system and highlights current and future clinical applications beyond ED.

Update on current and future novel therapies for dry age-related macular degeneration

Age-related macular degeneration (ARMD) is the leading cause of irreversible blindness in developed countries. There are currently no cures, but there are promising potential therapies that target the underlying disease mechanisms of dry ARMD. Stem cells, ciliary neurotrophic factor, rheopheresis, ozonated autohemotherapy and prostaglandins show promise in stabilizing or improving visual acuity. Age-Related Eye Disease Study vitamins may reduce progression to severe ARMD. Adjuvant therapy like low vision rehabilitation and implantable miniature telescopes may help patients adjust to the sequelae of their disease, and herbal supplementation with saffron, zinc monocysteine and phototrop may be helpful. Therapies that are currently in clinical trials include brimonidine, doxycycline, anti-amyloid antibodies (GSK933776 and RN6G), RPE65 inhibitor (ACU-4429), complement inhibitors (ARC1905, FCFD4514S), hydroxychloroquine, intravitreal fluocinolone acetate and vasodilators like sildenafil, moxaverine and MC-1101. Therapies that have not been shown to be effective include POT-4, eculizumab, tandospirone, anecortave acetate, the antioxidant OT-551, sirolimus and vitamin E.

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.