The Serendipitous Story of Sildenafil: An Unexpected Oral Therapy for Erectile Dysfunction

Social Perceptions of Masculinity and Sexual Esteem Are Impacted by Viagra Use, Testosterone, and Sexual Performance

Sexual behaviors play a role in the social construction of masculinity. Moreover, this stereotype has been capitalized upon by pharmaceutical companies, as well as those that sell products not approved by the U.S. Food and Drug Administration, for purposes of marketing sexual medicines. Stereotypical notions of masculinity, however, also emphasize the importance of self-reliance, which may cause some to look unfavorably upon the use of sexual medicine. Consistent with this notion, a male target was viewed as more masculine when his female partner consistently reached orgasm, unless he had no history of erectile dysfunction (ED), but was taking Viagra anyway (Experiment 1; N = 522). In addition, when his partner consistently reached orgasm, ratings of his sexual esteem were also lower if he used Viagra than if he did not, but only if he had no history of ED. In Experiment 2 (N = 711), although there was no effect of a male target's use of testosterone, social perception of his masculinity and sexual esteem increased as his "natural" levels of testosterone increased. In addition, exploratory analysis revealed that if the male target had low (but not normal or high) "natural" levels of testosterone, ratings of his masculinity were higher if his female partner consistently had an orgasm, which suggests that female orgasm served to "rescue" masculinity. Because expectations about drugs drive their use, it is important to address preconceived notions about the use of sexual medicines for purposes of enhancing masculinity and sexual esteem, as the social perception of their use is much more complex.

Composition Characterization of Cinnamomum osmophloeum Kanehira Hydrosol and Its Enhanced Effects on Erectile Function

Cinnamomum osmophloeum Kanehira (CO) is an endemic species of Taiwan. This study elucidated the composition of CO hydrosol, revealing trans-cinnamaldehyde (65.03%), trans-cinnamyl acetate (7.57%), and coumarin (4.31%) as the main volatile compounds. Seven compounds were identified in the water fraction of hydrosol, including a novel compound, 2-(2-hydroxyphenyl)oxetan-3-ol. This marks the first investigation into high-polarity compounds in hydrosol, extending beyond the volatile components. Notably, two compounds, trans-phenyloxetan-3-ol and cis-phenyloxetan-3-ol, demonstrated significant inhibition activity against phosphodiesterase type five (PDE5), with IC50 values of 4.37 µM and 3.40 µM, respectively, indicating their potential as novel PDE5 inhibitors. Furthermore, CO hydrosol was evaluated against enzymes associated with erectile dysfunction, namely acetylcholinesterase (AChE), angiotensin-I converting enzyme (ACE), and arginase type 2 (ARG2). These findings underscore the potential of CO hydrosol to modulate erectile function through diverse physiological pathways, hinting at its prospects for future development in a beverage or additive with enhanced effects on erectile function.

An Alternative Approach to Synthesize Sildenafil via Improved Copper-Catalyzed Cyclization

A facile synthetic pathway for sildenafil has been developed. This approach is characterized by a ligand-free Ullmann-type copper-catalyzed coupling reaction to construct sildenafil and its derivative, pyrrazolo[4,3-d]pyrimidin-7-one ring, with yields of 79% and 82%, respectively, in a convergent fashion by connecting key building blocks halo-pyrazole moiety 16c with 2-ethoxybenzamidine and 2-ethoxy-5-[(4-methylpiperazin-1-yl)sulfonyl]benzamidine in a one-pot reaction. Thus, this approach circumvents the need to use nitric/sulfuric acid for nitration, a costly Pd-catalyst for reduction, and coupling agents encountered in the reported processes.

Outlier analysis for accelerating clinical discovery: An augmented intelligence framework and a systematic review

Clinical discoveries largely depend on dedicated clinicians and scientists to identify and pursue unique and unusual clinical encounters with patients and communicate these through case reports and case series. This process has remained essentially unchanged throughout the history of modern medicine. However, these traditional methods are inefficient, especially considering the modern-day availability of health-related data and the sophistication of computer processing. Outlier analysis has been used in various fields to uncover unique observations, including fraud detection in finance and quality control in manufacturing. We propose that clinical discovery can be formulated as an outlier problem within an augmented intelligence framework to be implemented on any health-related data. Such an augmented intelligence approach would accelerate the identification and pursuit of clinical discoveries, advancing our medical knowledge and uncovering new therapies and management approaches. We define clinical discoveries as contextual outliers measured through an information-based approach and with a novelty-based root cause. Our augmented intelligence framework has five steps: define a patient population with a desired clinical outcome, build a predictive model, identify outliers through appropriate measures, investigate outliers through domain content experts, and generate scientific hypotheses. Recognizing that the field of obstetrics can particularly benefit from this approach, as it is traditionally neglected in commercial research, we conducted a systematic review to explore how outlier analysis is implemented in obstetric research. We identified two obstetrics-related studies that assessed outliers at an aggregate level for purposes outside of clinical discovery. Our findings indicate that using outlier analysis in clinical research in obstetrics and clinical research, in general, requires further development.

A real-world pharmacovigilance study of FDA adverse event reporting system events for sildenafil

BACKGROUND

Sildenafil, a selective inhibitor of phosphodiesterase type 5 (PDE5), is widely used for the treatment of erectile dysfunction (ED). However, the safety profile of sildenafil, including adverse event (AEs), requires comprehensive evaluation.

METHODS

This retrospective pharmacovigilance study aimed to evaluate AEs linked to sildenafil by analyzing data sourced from the FDA Adverse Event Reporting System (FAERS) database. A case/non-case design was utilized, and various algorithms including the reporting odds ratio (ROR), the proportional reporting ratio (PRR), the Bayesian confidence propagation neural network (BCPNN), and the multiitem gamma Poisson shrinker (MGPS) were employed to measure the signals indicating the presence of sildenafil-related AEs.

RESULTS

Among 339,230 reports, 33,692 specifically mentioned sildenafil use. Most of AEs occurred in males over 60 years old. The United States accounted for the highest proportion of reported AEs. Severe outcomes, including death, disability, and life-threatening events, were reported. Significant system organ class (SOC) included "Reproductive system and breast disorders" (SOC: 10038604), "Neoplasms benign, malignant and unspecified" (SOC: 10038738), "Vascular disorders" (SOC: 10047065), and "Blood and lymphatic system disorders" (SOC: 10005329). Noteworthy preferred terms (PTs) associated with sildenafil included "Vision blurred," "Flushing," "sudden hearing loss," "Painful erection," and "Priapism." Unexpected AEs, such as "Malignant melanoma," "Pulmonary hypertension," "Malignant melanoma in situ," "Pulmonary arterial hypertension," "Metastatic malignant melanoma," "Malignant melanoma stage III," "Malignant melanoma stage II," "Acquired hemophilia," "Aortic dissection rupture," and "Intracranial artery dissection" were also identified.

CONCLUSIONS

These findings emphasize the importance of monitoring and understanding the potential risks associated with sildenafil. Further investigation is warranted to validate these associations and address previously unrecognized safety concerns.

Reimagining old drugs with new tricks: Mechanisms, strategies and notable success stories in drug repurposing for neurological diseases

Recent evolution in drug repurposing has brought new anticipation, especially in the conflict against neurodegenerative diseases (NDDs). The traditional approach to developing novel drugs for these complex disorders is laborious, time-consuming, and often abortive. However, drug reprofiling which is the implementation of illuminating novel therapeutic applications of existing approved drugs, has shown potential as a promising strategy to accelerate the hunt for therapeutics. The advancement of computational approaches and artificial intelligence has expedited drug repurposing. These progressive technologies have enabled scientists to analyse extensive datasets and predict potential drug-disease interactions. By prospecting into the existing pharmacological knowledge, scientists can recognise potential therapeutic candidates for reprofiling, saving precious time and resources. Preclinical models have also played a pivotal role in this field, confirming the effectiveness and mechanisms of action of repurposed drugs. Several studies have occurred in recent years, including the discovery of available drugs that demonstrate significant protective effects in NDDs, relieve debilitating symptoms, or slow down the progression of the disease. These findings highlight the potential of repurposed drugs to change the landscape of NDD treatment. Here, we present an overview of recent developments and major advances in drug repurposing intending to provide an in-depth analysis of traditional drug discovery and the strategies, approaches and technologies that have contributed to drug repositioning. In addition, this chapter attempts to highlight successful case studies of drug repositioning in various therapeutic areas related to NDDs and explore the clinical trials, challenges and limitations faced by researchers in the field. Finally, the importance of drug repositioning in drug discovery and development and its potential to address discontented medical needs is also highlighted.

Estrogenic endocrine disruptor exposure directly impacts erectile function

Erectile dysfunction (ED) is an extremely prevalent condition which significantly impacts quality of life. The rapid increase of ED in recent decades suggests the existence of unidentified environmental risk factors contributing to this condition. Endocrine Disrupting Chemicals (EDCs) are one likely candidate, given that development and function of the erectile tissues are hormonally dependent. We use the estrogenic-EDC diethylstilbestrol (DES) to model how widespread estrogenic-EDC exposure may impact erectile function in humans. Here we show that male mice chronically exposed to DES exhibit abnormal contractility of the erectile tissue, indicative of ED. The treatment did not affect systemic testosterone production yet significantly increased estrogen receptor α (Esr1) expression in the primary erectile tissue, suggesting EDCs directly impact erectile function. In response, we isolated the erectile tissue from mice and briefly incubated them with the estrogenic-EDCs DES or genistein (a phytoestrogen). These acute-direct exposures similarly caused a significant reduction in erectile tissue contractility, again indicative of ED. Overall, these findings demonstrate a direct link between estrogenic EDCs and erectile dysfunction and show that both chronic and acute estrogenic exposures are likely risk factors for this condition.

Major adverse cardiovascular events related to phosphodiesterase 5 inhibitors: analysis of real-life data from Eudra-Vigilance database

BACKGROUND

Phosphodiesterase 5 inhibitors (PDE5i) are the standard medical treatment for erectile dysfunction. Aim of our study was to evaluate the rate of major adverse cardiovascular events (MACE) reported during PDE5i treatment based on Eudra-Vigilance (EV) reports.

METHODS

EV database is the system for managing and analyzing data on suspected adverse reactions to medicines which have been authorized or being studied in clinical trials in the European Economic Area. MACE are defined as non-fatal stroke, non-fatal myocardial infarction, non-fatal congestive heart failure, revascularization after aorto-coronary graft bypass and cardiovascular death. We recorded the number of MACE for sildenafil, tadalafil, vardenafil, avanafil per category and severity until 1st July 2023. Pooled Relative Risk (PRR) was used to compare data between drugs.

RESULTS

Overall, 951 MACE events were reported. Most of them were observed in younger patients <65 years old (452/951 events, 48%). Overall, 377/8939 (4%) MACE events were observed for sildenafil, 221/5213 (4%) for tadalafil, 50/1029 (4%) for vardenafil and no events for avanafil. No significative differences were reported comparing sildenafil and tadalafil (PRR 0.71-0.99, IQR 0.61-1.35, P>0.05), neither sildenafil vs. vardenafil (PRR 0.68-0.79, IQR 0.43-1.55, P>0.05), neither tadalafil vs. vardenafil (PRR 0.77-0.95, IQR 0.64-1.30. P>0.05) even when compared for age. Comparison between different classes of age showed MACE were more frequent in patients younger than 65 years old taking sildenafil and tadalafil when compared to patients older than 85 years old (PRR 0.02-0.11. IQR 0.01-0.40. P<0.01) and when compared to patients in 65-85 class of age (PRR 0.02-0.12, IQR 0.01-0.95, P<0.01).

CONCLUSIONS

Real life data is consistent with MACE related to PDE5i. PDE5is are infrequently (<5%) associated with MACE. However, risk seems higher in younger patients, particularly for sildenafil (452/951 events, 48%). Clinicians should consider these data when prescribing PDE5i especially in young patients.

Novel strategies for drug repurposing

Synthetic biology, precision medicine, and nanobiotechnology are the three main emerging areas that drive translational innovation toward commercialization. There are several strategies used in precision medicine and drug repurposing is one of the key approaches as it addresses the challenges in drug discovery (high cost and time). Here, we provide a perspective on various new approaches to drug repurposing for cancer precision medicine. We report here our optimized wound healing methodology that can be used to validate drug sensitivity and drug repurposing. Using HeLa as our benchmark, we demonstrated that the assay can be applied to identify drugs that limit cell proliferation. From a future perspective, this assay can be expanded to ex vivo culturing of solid tumors in 2D culture and leukemia in 3D culture.

Phosphodiesterase Type 5 Inhibitors in Men With Erectile Dysfunction and the Risk of Alzheimer Disease: A Cohort Study

BACKGROUND AND OBJECTIVES

Repurposing phosphodiesterase type 5 inhibitors (PDE5Is) as drugs for Alzheimer disease (AD) risk reduction has shown promise based on animal studies. However, evidence in humans remains inconclusive. Therefore, we conducted a cohort study to evaluate the association between PDE5I initiation compared with nonuse and the risk of developing AD in men with erectile dysfunction (ED).

METHODS

Using electronic health records from IQVIA Medical Research Data UK (formerly known as the THIN database), we identified men aged ≥40 years with a new diagnosis of ED between 2000 and 2017. Individuals with a previous diagnosis of dementia, cognitive impairment, confusion, or prescription for dementia symptoms were excluded. The occurrence of incident AD was identified using diagnostic read codes. To minimize immortal-time bias, PDE5I initiation was treated as a time-varying exposure variable. Potential confounders were adjusted using inverse probability of treatment weighting based on propensity scores. Cox proportional hazard models were used to estimate the adjusted hazard ratio (HR) with 95% CIs. A secondary analysis explored the association between AD and the cumulative number of PDE5I prescriptions. Sensitivity analyses included lag (delay) periods of 1 and 3 years after cohort entry to address the prodromal stage of AD.

RESULTS

The study included 269,725 men, with 1,119 newly diagnosed with AD during a median follow-up of 5.1 (interquartile range 2.9-8.9) years. The adjusted HR in PDE5I initiators compared with nonuse was 0.82 (95% CI 0.72-0.93). The associated risk of AD decreased in individuals issued >20 prescriptions: HR 0.56 (95% CI 0.43-0.73) for 21-50 prescriptions and HR 0.65 (95% CI 0.49-0.87) for >50 prescriptions. Sensitivity analysis with a 1-year lag period supported the primary findings (HR 0.82, 95% CI 0.72-0.94), but the results differed with the inclusion of a 3-year lag period (HR 0.93, 95% CI 0.80-1.08).

DISCUSSION

PDE5I initiation in men with ED was associated with a lower risk of AD, particularly in those most frequently issued prescriptions. The differences between primary and sensitivity analyses highlight the need to explore the optimal lag period. To enhance the generalizability of our findings, a randomized controlled trial including both sexes and exploring various PDE5I doses would be beneficial to confirm the association between PDE5I and AD.

Princeton IV consensus guidelines: PDE5 inhibitors and cardiac health

BACKGROUND

In 1999, 1 year after the approval of the first oral phosphodiesterase type 5 (PDE5) inhibitor for the treatment of erectile dysfunction (ED), the first Princeton Consensus Conference was held to address the clinical management of men with ED who also had cardiovascular disease. These issues were readdressed in the second and third conferences. In the 13 years since the last Princeton Consensus Conference, the experience with PDE5 inhibitors is more robust, and recent new data have emerged regarding not only safety and drug-drug interactions, but also a potential cardioprotective effect of these drugs.

AIM

In March 2023, an interdisciplinary group of scientists and practitioners met for the fourth Princeton Consensus Guidelines at the Huntington Medical Research Institutes in Pasadena, California, to readdress the cardiovascular workup of men presenting with ED as well as the approach to treatment of ED in men with known cardiovascular disease.

METHOD

A series of lectures from experts in the field followed by Delphi-type discussions were developed to reach consensus.

OUTCOMES

Consensus was reached regarding a number of issues related to erectile dysfunction and the interaction with cardiovascular health and phosphodiesterase-5 inhibitors.

RESULTS

An algorithm based on recent recommendations of the American College of Cardiology and American Heart Association, including the use of computed tomography coronary artery calcium scoring, was integrated into the evaluation of men presenting with ED. Additionally, the issue of nitrate use was further considered in an algorithm regarding the treatment of ED patients with coronary artery disease. Other topics included the psychological effect of ED and the benefits of treating it; the mechanism of action of the PDE5 inhibitors; drug-drug interactions; optimizing use of a PDE5 inhibitors; rare adverse events; potential cardiovascular benefits observed in recent retrospective studies; adulteration of dietary supplements with PDE5 inhibitors; the pros and cons of over-the-counter PDE5 inhibitors; non-PDE5 inhibitor therapy for ED including restorative therapies such as stem cells, platelet-rich plasma, and shock therapy; other non-PDE5 inhibitor therapies, including injection therapy and penile prostheses; the issue of safety and effectiveness of PDE5 inhibitors in women; and recommendations for future studies in the field of sexual dysfunction and PDE5 inhibitor use were discussed.

CLINICAL IMPLICATIONS

Algorithms and tables were developed to help guide the clinician in dealing with the interaction of ED and cardiovascular risk and disease.

STRENGTHS AND LIMITATIONS

Strengths include the expertise of the participants and consensus recommendations. Limitations included that participants were from the United States only for this particular meeting.

CONCLUSION

The issue of the intersection between cardiovascular health and sexual health remains an important topic with new studies suggesting the cardiovascular safety of PDE5 inhibitors.

Exploring NCATS in-house biomedical data for evidence-based drug repurposing

Drug repurposing is a strategy for identifying new uses of approved or investigational drugs that are outside the scope of the original medical indication. Even though many repurposed drugs have been found serendipitously in the past, the increasing availability of large volumes of biomedical data has enabled more systemic, data-driven approaches for drug candidate identification. At National Center of Advancing Translational Sciences (NCATS), we invent new methods to generate new data and information publicly available to spur innovation and scientific discovery. In this study, we aimed to explore and demonstrate biomedical data generated and collected via two NCATS research programs, the Toxicology in the 21st Century program (Tox21) and the Biomedical Data Translator (Translator) for the application of drug repurposing. These two programs provide complementary types of biomedical data from uncovering underlying biological mechanisms with bioassay screening data from Tox21 for chemical clustering, to enrich clustered chemicals with scientific evidence mined from the Translator towards drug repurposing. 129 chemical clusters have been generated and three of them have been further investigated for drug repurposing candidate identification, which is detailed as case studies.

Sildenafil Reverses the Neuropathological Alzheimer's Disease Phenotype in Cholinergic-Like Neurons Carrying the Presenilin 1 E280A Mutation

Background

Familial Alzheimer's disease (FAD) presenilin 1 E280A (PSEN 1 E280A) is characterized by functional impairment and the death of cholinergic neurons as a consequence of amyloid-β (Aβ) accumulation and abnormal phosphorylation of the tau protein. Currently, there are no available therapies that can cure FAD. Therefore, new therapies are urgently needed for treating this disease.

Objective

To assess the effect of sildenafil (SIL) on cholinergic-like neurons (ChLNs) harboring the PSEN 1 E280A mutation.

Methods

Wild-type (WT) and PSEN 1 E280A ChLNs were cultured in the presence of SIL (25μM) for 24 h. Afterward, proteinopathy, cell signaling, and apoptosis markers were evaluated via flow cytometry and fluorescence microscopy.

Results

We found that SIL was innocuous toward WT PSEN 1 ChLNs but reduced the accumulation of intracellular Aβ fragments by 87%, decreased the non-physiological phosphorylation of the protein tau at residue Ser202/Thr205 by 35%, reduced the phosphorylation of the proapoptotic transcription factor c-JUN at residue Ser63/Ser73 by 63%, decreased oxidized DJ-1 at Cys106-SO3 by 32%, and downregulated transcription factor TP53 (tumor protein p53), BH-3-only protein PUMA (p53 upregulated modulator of apoptosis), and cleaved caspase 3 (CC3) expression by 20%, 32%, and 22%, respectively, compared with untreated mutant ChLNs. Interestingly, SIL also ameliorated the dysregulation of acetylcholine-induced calcium ion (Ca2+) influx in PSEN 1 E280A ChLNs.

Conclusions

Although SIL showed no antioxidant capacity in the oxygen radical absorbance capacity and ferric ion reducing antioxidant power assays, it might function as an anti-amyloid and antiapoptotic agent and functional neuronal enhancer in PSEN 1 E280A ChLNs. Therefore, the SIL has therapeutic potential for treating FAD.

The dark side of drug repurposing. From clinical trial challenges to antimicrobial resistance: analysis based on three major fields

Drug repurposing is a strategic endeavor that entails the identification of novel therapeutic applications for pharmaceuticals that are already available in the market. Despite the advantageous nature of implementing this particular strategy owing to its cost-effectiveness and efficiency in reducing the time required for the drug discovery process, it is essential to bear in mind that there are various factors that must be meticulously considered and taken into account. Up to this point, there has been a noticeable absence of comprehensive analyses that shed light on the limitations of repurposing drugs. The primary aim of this review is to conduct a thorough illustration of the various challenges that arise when contemplating drug repurposing from a clinical perspective in three major fields-cardiovascular, cancer, and diabetes-and to further underscore the potential risks associated with the emergence of antimicrobial resistance (AMR) when employing repurposed antibiotics for the treatment of noninfectious and infectious diseases. The process of developing repurposed medications necessitates the application of creativity and innovation in designing the development program, as the body of evidence may differ for each specific case. In order to effectively repurpose drugs, it is crucial to consider the clinical implications and potential drawbacks that may arise during this process. By comprehensively analyzing these challenges, we can attain a deeper comprehension of the intricacies involved in drug repurposing, which will ultimately lead to the development of more efficacious and safe therapeutic approaches.

PDE5 inhibitors: breaking new grounds in the treatment of COVID-19

INTRODUCTION

Despite the ever-increasing occurrences of the coronavirus disease (COVID-19) cases around the world, very few medications have been validated in the clinical trials to combat COVID-19. Although several vaccines have been developed in the past quarter, the time elapsed between deployment and administration remains a major impediment.

CONTENT

Repurposing of pre-approved drugs, such as phosphodiesterase 5 (PDE5) inhibitors, could be a game-changer while lessening the burden on the current healthcare system. Repurposing and developing phosphodiesterase 5 (PDE5) inhibitors could extrapolate their utility to combat the SARS-CoV-2 infection, and potentially aid in the management of the symptoms associated with its newer variants such as BF.7, BQ.1, BQ.1.1, XBB.1.5, and XBB.1.16.

SUMMARY

Administration of PDE5 inhibitors via the oral and intravenous route demonstrates other potential off-label benefits, including anti-apoptotic, anti-inflammatory, antioxidant, and immunomodulatory effects, by intercepting several pathways. These effects can not only be of clinical importance in mild-to-moderate, but also moderate-to-severe SARS-CoV-2 infections. This article explores the various mechanisms by which PDE5 inhibitors alleviates the symptoms associated with COVID-19 as well as well as highlights recent studies and findings.

OUTLOOK

These benefits of PDE5 inhibitors make it a potential drug in the physicians' armamentarium in alleviating symptoms associated with SARS-CoV-2 infection. However, adequate clinical studies must be instituted to eliminate any untoward adverse events.

Pyrazole: an emerging privileged scaffold in drug discovery

Pyrazole or 1H-pyrazole, a five-membered 1,2-diazole, is found in several approved drugs and some bioactive natural products. A myriad number of derivatives of this small molecule have been reported in clinical and preclinical studies for the potential treatment of several diseases. The number of drugs containing a pyrazole nucleus has increased significantly in the last 10 years. Some of the best-selling drugs in this class are ibrutinib, ruxolitinib, axitinib, niraparib and baricitinib, and are used to treat different types of cancers; lenacapavir to treat HIV; riociguat to treat pulmonary hypertension; and sildenafil to treat erectile dysfunction. Several aniline-derived pyrazole compounds have been reported as potent antibacterial agents with selective activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. Here, we discuss the pyrazole-derived drugs reported up to September 2023.

Growing Utilization of Radical Chemistry in the Synthesis of Pharmaceuticals

Our current unhealthy lifestyle and the exponential surge in the population getting affected by a variety of diseases have made pharmaceuticals or drugs an imperative part of life, making the development of innovative strategies for drug discovery or the introduction of refined, cost-effective and modern technologies for the synthesis of clinically used drugs, a need of the hour. Ever since their discovery, free radicals and radical cations or anions as reactive intermediates have captivated the chemists, resulting in an exceptional utilization of these moieties throughout the field of chemical synthesis, owing to their unprecedented and widespread reactivity. Sticking with the idea of not judging the book by its cover, despite the conventional thought process of radicals being unstable and difficult to control entities, scientists and academicians around the globe have done an appreciable amount of work utilizing both persistent as well as transient radicals for a variety of organic transformations, exemplifying them with the synthesis of significant biologically active pharmaceutical ingredients. This review truly accounts for the organic radical transformations including radical addition, radical cascade cyclization, radical/radical cross-coupling, coupling with metal-complexes and radical cations coupling with nucleophiles, that offers fascinating and unconventional approaches towards the construction of intricate structural frameworks of marketed APIs with high atom- and step-economy; complementing the otherwise employed traditional methods. This tutorial review presents a comprehensive package of diverse methods utilized for radical generation, featuring their reactivity to form critical bonds in pharmaceutical total synthesis or in building key starting materials or intermediates of their synthetic journey, acknowledging their excellence, downsides and underlying mechanisms, which are otherwise poorly highlighted in the literature. Despite great achievements over the past few decades in this area, many challenges and obstacles are yet to be unraveled to shorten the distance between the academics and the industry, which are all discussed in summary and outlook.

Artificial Intelligence/Machine Learning-Driven Small Molecule Repurposing via Off-Target Prediction and Transcriptomics

The process of discovering small molecule drugs involves screening numerous compounds and optimizing the most promising ones, both in vitro and in vivo. However, approximately 90% of these optimized candidates fail during trials due to unexpected toxicity or insufficient efficacy. Current concepts with respect to drug-protein interactions suggest that each small molecule interacts with an average of 6-11 targets. This implies that approved drugs and even discontinued compounds could be repurposed by leveraging their interactions with unintended targets. Therefore, we developed a computational repurposing framework for small molecules, which combines artificial intelligence/machine learning (AI/ML)-based and chemical similarity-based target prediction methods with cross-species transcriptomics information. This repurposing methodology incorporates eight distinct target prediction methods, including three machine learning methods. By using multiple orthogonal methods for a "dataset" composed of 2766 FDA-approved drugs targeting multiple therapeutic target classes, we identified 27,371 off-target interactions involving 2013 protein targets (i.e., an average of around 10 interactions per drug). Relative to the drugs in the dataset, we identified 150,620 structurally similar compounds. The highest number of predicted interactions were for drugs targeting G protein-coupled receptors (GPCRs), enzymes, and kinases with 10,648, 4081, and 3678 interactions, respectively. Notably, 17,283 (63%) of the off-target interactions have been confirmed in vitro. Approximately 4000 interactions had an IC50 of <100 nM for 1105 FDA-approved drugs and 1661 interactions had an IC50 of <10 nM for 696 FDA-approved drugs. Together, the confirmation of numerous predicted interactions and the exploration of tissue-specific expression patterns in human and animal tissues offer insights into potential drug repurposing for new therapeutic applications.

A tunable family of CAAC-ruthenium olefin metathesis catalysts modularly derived from a large-scale produced ibuprofen intermediate

A series of tunable CAAC-based ruthenium benzylidene complexes with increased lipophilicity derived from a ketone being a large-scale produced key substrate for a popular nonsteroidal anti-inflammatory drug-ibuprofen was obtained and tested in various olefin metathesis transformations. As a group, these catalysts exhibited higher activity than their known analogues containing a smaller and less lipophilic phenyl substituent on the α-carbon atom, but in individual reactions, the size of the N-aryl moiety was revealed as a decisive factor. For example, in the cross-metathesis of methyl oleate with ethylene (ethenolysis)-a reaction with growing industrial potential-the best results were obtained when the N-aryl contained an isopropyl or tert-butyl substituent in the ortho position. At the same time, in the RCM, CM, and self-CM transformations involving larger olefinic substrates, the catalysts with smaller aryl-bearing CAAC ligands, where methyl and ethyl groups occupy ortho, ortho' positions performed better. This offers a great deal of tunability and allows for selection of the best catalyst for a given reaction while keeping the general structure (and manufacturing method) of the ibuprofen-intermediate derived CAAC ligand the same.

Ameliorative effect of hesperidin against high dose sildenafil-induced liver and testicular oxidative stress and altered gene expression in male rats

BACKGROUND

The clinical use of sildenafil citrate (Viagra), a drug used to treat erectile dysfunction, is limited because of its many side effects on tissues. In this context, we aimed to investigate the protective effects of hesperidin, a citrus flavonoid, on hepatic and testicular damage induced by a high dose of sildenafil citrate in male rats. Rats were randomly divided into four groups. The first group was used as the control group. The second group was orally administered sildenafil citrate at a high dose of 75 mg/kg thrice a week. In the third group, hesperidin was administered orally at a dose of 50 mg/kg/day. The fourth group was administered 75 mg/kg sildenafil citrate three times a week with 50 mg/kg hesperidin daily. The experiment lasted for 28 days.

RESULTS

In the sildenafil-treated groups, blood indices were altered, liver function tests were deranged, and serum testosterone levels were reduced. In the liver and testicular tissue, sildenafil citrate treatment resulted in significant reductions in catalase and total antioxidant capacity; as well as increased malondialdehyde, reactive oxygen species, and nitrous oxide levels. In addition, sildenafil citrate treatment caused abnormal histopathological patterns in both the liver and the testes. Liver vascular endothelial growth factor and testicular steroidogenic acute regulatory protein gene expression were upregulated.

CONCLUSIONS

Hesperidin attenuated the harmful effects of intensive sildenafil citrate treatment on liver and testicular functions, alleviated oxidative stress and normalized blood indices. Therefore, hesperidin could be protective against sildenafil citrate-induced oxidative damage that may develop over the long term.

PDE5 inhibitors: breaking new grounds in the treatment of COVID-19

INTRODUCTION

Despite the ever-increasing occurrences of the coronavirus disease (COVID-19) cases around the world, very few medications have been validated in the clinical trials to combat COVID-19. Although several vaccines have been developed in the past quarter, the time elapsed between deployment and administration remains a major impediment.

CONTENT

Repurposing of pre-approved drugs, such as phosphodiesterase 5 (PDE5) inhibitors, could be a game-changer while lessening the burden on the current healthcare system. Repurposing and developing phosphodiesterase 5 (PDE5) inhibitors could extrapolate their utility to combat the SARS-CoV-2 infection, and potentially aid in the management of the symptoms associated with its newer variants such as BF.7, BQ.1, BQ.1.1, XBB.1.5, and XBB.1.16.

SUMMARY

Administration of PDE5 inhibitors via the oral and intravenous route demonstrates other potential off-label benefits, including anti-apoptotic, anti-inflammatory, antioxidant, and immunomodulatory effects, by intercepting several pathways. These effects can not only be of clinical importance in mild-to-moderate, but also moderate-to-severe SARS-CoV-2 infections. This article explores the various mechanisms by which PDE5 inhibitors alleviates the symptoms associated with COVID-19 as well as well as highlights recent studies and findings.

OUTLOOK

These benefits of PDE5 inhibitors make it a potential drug in the physicians' armamentarium in alleviating symptoms associated with SARS-CoV-2 infection. However, adequate clinical studies must be instituted to eliminate any untoward adverse events.

Exploring the application of sildenafil for high-fat diet-induced erectile dysfunction based on interleukin-18-mediated NLRP3/Caspase-1 signaling pathway

Background

Inflammation is a key risk factor for heart disease and has also been linked to erectile dysfunction (ED). Sildenafil is a phosphodiesterase type 5 inhibitor with a strong antioxidant effect. Interleukin (IL)-18 is a proinflammatory factor. Excessive production and release of IL-18 disrupt the balance between IL-18 and IL-18 binding proteins in certain inflammatory diseases, leading to the occurrence of pathological inflammation.

Aim

We evaluated the effects of sildenafil on erectile function in a rat model of high-fat diet-induced ED.

Methods

Male Sprague Dawley rats (6 weeks old) were divided into 5 groups: control, ED, sildenafil, IL-18, and IL-18 + sildenafil. Subsequently, intracavernous pressure and mean arterial pressure were used to assess the erectile function of these rats. The expression of endothelial nitric oxide synthase, pyroptosis factors, and the ratio of smooth muscle cells and collagen fibers were evaluated in the serum and corpora tissue.

Outcomes

Exploring the role and mechanism of sildenafil in ED through NLRP3-mediated pyroptosis pathway.

Results

In comparison to the ED and IL-18 groups, there were statistically significant increases in the ratio of intracavernous pressure to mean arterial pressure, endothelial nitric oxide synthase expression, and the ratio of smooth muscle cells to collagen fibers following sildenafil intervention (P < .05). The sildenafil group and IL-18 + sildenafil group also showed statistically significant decreases the expression of NLRP3, caspase-1, and gasdermin D (P < .05).

Clinical Implications

Sildenafil can improve erectile dysfunction by inhibiting inflammation.

Strengths and Limitations

Strengths are that the relationship between pyroptosis and ED has been verified through in vitro and in vivo experiments. The limitation is that the conclusions drawn from animal and cells experiments need to be confirmed in clinical research.

Conclusion

Sildenafil may reduce the effect of IL-18-induced inflammation in high-fat diet-induced ED rats through NLRP3/caspase-1 pyroptosis pathway.

Cardiac Effects of Phosphodiesterase-5 Inhibitors: Efficacy and Safety

The coexistence of cardiovascular disease and erectile dysfunction is widespread, possibly owing to underlying endothelial dysfunction in both diseases. Millions of patients with cardiovascular disease are prescribed phosphodiesterase-5 (PDE5) inhibitors for the management of erectile dysfunction. Although the role of PDE5 inhibitors in erectile dysfunction therapy is well established, their effects on the cardiovascular system are unclear. Preclinical studies investigating the effect of PDE5 inhibitors on ischemia-reperfusion injury, pressure overload-induced hypertrophy, and chemotoxicity suggested a possible clinical role for each of these medications; however, attempts to translate these findings to the bedside have resulted in mixed outcomes. In this review, we explore the biologic preclinical effects of PDE5 inhibitors in mediating cardioprotection. We then examine clinical trials investigating PDE5 inhibition in patients with heart failure, coronary artery disease, and ventricular arrhythmias and discuss why the studies likely have yet to show positive results and efficacy with PDE5 inhibition despite no safety concerns.

Exploring NCATS In-House Biomedical Data for Evidence-based Drug Repurposing

Drug repurposing is a strategy for identifying new uses of approved or investigational drugs that are outside the scope of the original medical indication. Even though many repurposed drugs have been found serendipitously in the past, the increasing availability of large volumes of biomedical data has enabled more systemic, data-driven approaches for drug candidate identification. At National Center of Advancing Translational Sciences (NCATS), we invent new methods to generate new data and information publicly available to spur innovation and scientific discovery. In this study, we aimed to explore and demonstrate biomedical data generated and collected via two NCATS research programs, the Toxicology in the 21st Century program (Tox21) and the Biomedical Data Translator (Translator) for the application of drug repurposing. These two programs provide complementary types of biomedical data from uncovering underlying biological mechanisms with bioassay screening data from Tox21 for chemical clustering, to enrich clustered chemicals with scientific evidence mined from the Translator towards drug repurposing. 129 chemical clusters have been generated and three of them have been further investigated for drug repurposing candidate identification, which is detailed as case studies.

Innovation in the 21st century: following the footsteps of Katalin Karikó

Innovation is a critical component of human society, setting us apart from other animals. We possess a unique capacity to design and produce new things through cultivating a culture that values and encourages innovation. One remarkable instance of innovation in the field of biology and medicine is the mRNA vaccine platform developed by Katalin Karikó and her colleagues. In this article, we delve into the evolution of mRNA-based therapy, beginning with animal models and concluding with the first clinical trials. The history of mRNA research began with the identification of its role in protein synthesis, leading to the development of mRNA vaccine technology. Karikó's pivotal innovation was discovering the need to integrate modified nucleosides into the mRNA, decreasing its recognition by the immune system. Her story offers valuable lessons, including the importance of market demand as a booster effect, the role of emerging technologies, the significance of universities and academic institutions in fostering innovation, the role of perseverance and faith, and the role of chance.

Sildenafil affects the human Kir2.1 and Kir2.2 channels at clinically relevant concentrations: Inhibition potentiated by low Ba2

Sildenafil (Viagra), the first approved and widely used oral drug for the treatment of erectile dysfunction, was occasionally associated with life-threatening ventricular arrhythmias in patients. Since inward rectifier potassium current (I _K1) may considerably contribute to this arrhythmogenesis, we investigated the effect of sildenafil on the human Kir2.1 and Kir2.2, the prevailing subunits forming the ventricular I _K1 channels. Experiments were performed by the whole-cell patch clamp technique at 37°C using Chinese hamster ovary cells transiently expressing the human Kir2.1 and Kir2.2 channels. Changes of both the inward and outward current components (at -110 and -50 mV, respectively) were tested to be able to consider the physiological relevance of the sildenafil effect (changes at -110 and -50 mV did not significantly differ, results at -50 mV are listed below). A significant Kir2.1 inhibition was observed at all applied sildenafil concentrations (16.1% ± 3.7%, 20.0% ± 2.6%, and 15.0% ± 3.0% at 0.1, 1, and 10 μM, respectively). The inhibitory effect of 0.1 μM sildenafil was potentiated by the presence of a low concentration of Ba²⁺ (0.1 μM) which induced only a slight Kir2.1 inhibition by 5.95% ± 0.75% alone (the combined effect was 35.5% ± 3.4%). The subtherapeutic and therapeutic sildenafil concentrations (0.1 and 1 μM) caused a dual effect on Kir2.2 channels whereas a significant Kir2.2 activation was observed at the supratherapeutic sildenafil concentration (10 μM: 34.1% ± 5.6%). All effects were fully reversible. This is the first study demonstrating that sildenafil at clinically relevant concentrations inhibits both the inward and outward current components of the main human ventricular I _K1 subunit Kir2.1. This inhibitory effect was significantly potentiated by a low concentration of environmental contaminant Ba²⁺ in agreement with recently reported data on rat ventricular I _K1 which additionally showed a significant repolarization delay. Considering the similar subunit composition of the human and rat ventricular I _K1 channels, the observed effects might contribute to sildenafil-associated arrhythmogenesis in clinical practice.

Novel 9-Benzylaminoacridine Derivatives as Dual Inhibitors of Phosphodiesterase 5 and Topoisomerase II for the Treatment of Colon Cancer

It has been shown that phosphodiesterase 5 (PDE5) inhibitors have anticancer effects in a variety of malignancies in both in vivo and in vitro experiments. The role of cGMP elevation in colorectal carcinoma (CRC) has been extensively studied. Additionally, DNA topoisomerase II (Topo II) inhibition is a well-established mechanism of action that mediates the effects of several approved anticancer drugs such as doxorubicin and mitoxantrone. Herein, we present 9-benzylaminoacridine derivatives as dual inhibitors of the PDE5 and Topo II enzymes. We synthesized 31 derivatives and evaluated them against PDE5, whereby 22 compounds showed micromolar or sub-micromolar inhibition. The anticancer activity of the compounds was evaluated with the NCI 60-cell line testing. Moreover, the effects of the compounds on HCT-116 colorectal carcinoma (CRC) were extensively studied, and potent compounds against HCT-116 cells were studied for their effects on Topo II, cell cycle progression, and apoptosis. In addition to exhibiting significant growth inhibition against HCT116 cells, compounds 11, 12, and 28 also exhibited the most superior Topo II inhibitory activity and low micromolar PDE5 inhibition and affected cell cycle progression. Knowing that compounds that combat cancer through multiple mechanisms are among the best candidates for effective therapy, we believe that the current class of compounds merits further optimization and investigation to unleash their full therapeutic potential.

Management of male erectile dysfunction: From the past to the future

Erectile dysfunction is a common disease of the male reproductive system, which seriously affects the life quality of patients and their partners. At present, erectile dysfunction is considered as a social-psychological-physiological disease with complex etiology and various treatment methods. Oral PDE5I is the first-line treatment for erectile dysfunction with the advantages of high safety, good effect and non-invasiveness. But intracavernosal injection, hormonal replacement therapy, vacuum erection device, penile prosthesis implantation can also be alternative treatments for patients have organic erectile dysfunction or tolerance to PDE5I. With the rapid development of technologies, some new methods, such as low-intensity extracorporeal shock wave and stem cell injection therapy can even repair the organic damage of the corpora cavernosa. These are important directions for the treatment of male erectile dysfunction in the future. In this mini-review, we will introduce these therapies in detail.

Computational Drug Repurposing Approach to Identify Novel Inhibitors of ILK Protein for Treatment of Esophageal Squamous Cell Carcinoma

Purpose

Esophageal squamous cell cancer (ESCC) is a deadly malignant tumor characterized by an overall 5-year survival rate below 20%, with China accounting for approximately 50% of all cases worldwide. Our previous studies have demonstrated that high integrin-linked kinase (ILK) expression plays a key role in development and progression of ESCC both in vitro and in vivo. Here, we employed the drug repurposing approach to identify a novel FDA-approved anticancer inhibitor against ILK-induced tumorigenesis and progression.

Methods

We screened the ZINC15 database and predicted the molecular docking ability among FDA-approved and publicly available drugs to ILK and then performed computational docking and visual inspection analyses of the top 10 ranked drugs. Two computer-based virtual screened drugs were evaluated in vitro for their ability to directly bind purified ILK by surface plasmon resonance. Cytotoxicity of the two candidate drugs was validated in vitro using CCK-8 and LDH assays.

Results

We initially selected the top 10 compounds, based on their minimum binding energy to the ILK crystal, after molecular docking and subjected them to further screening. Taking the binding energy of -10 kcal/mol as the threshold, we selected two drugs, namely, nilotinib and teniposide, for the wet-lab experiment. Surface plasmon resonance (SPR) revealed that nilotinib and teniposide had equilibrium dissociation constant (KD) values of 6.410E - 6 and 1.793E - 6, respectively, which were lower than 2.643E - 6 observed in ILK-IN-3 used as the positive control. The IC50 values for nilotinib and teniposide in ESCC cell lines were 40 μM and 200-400 nM, respectively. Results of the CCK-8 assay demonstrated that both nilotinib and teniposide significantly inhibited proliferation of cells (P < 0.01). LDH results revealed that both drugs significantly suppressed the rate of cell death (P < 0.01).

Conclusion

The drug repositioning procedure can effectively identify new therapeutic tools for ESCC. Our findings suggest that nilotinib and teniposide are efficacious inhibitors of ILK and thus have potential to target ILK-mediated signaling pathways for management of ESCC.

The NO/cGMP/PKG pathway in platelets: The therapeutic potential of PDE5 inhibitors in platelet disorders

Platelets are the "guardians" of the blood circulatory system. At sites of vessel injury, they ensure hemostasis and promote immunity and vessel repair. However, their uncontrolled activation is one of the main drivers of thrombosis. To keep circulating platelets in a quiescent state, the endothelium releases platelet antagonists including nitric oxide (NO) that acts by stimulating the intracellular receptor guanylyl cyclase (GC). The latter produces the second messenger cyclic guanosine-3',5'-monophosphate (cGMP) that inhibits platelet activation by stimulating protein kinase G, which phosphorylates hundreds of intracellular targets. Intracellular cGMP pools are tightly regulated by a fine balance between GC and phosphodiesterases (PDEs) that are responsible for the hydrolysis of cyclic nucleotides. Phosphodiesterase type 5 (PDE5) is a cGMP-specific PDE, broadly expressed in most tissues in humans and rodents. In clinical practice, PDE5 inhibitors (PDE5i) are used as first-line therapy for erectile dysfunction, pulmonary artery hypertension, and lower urinary tract symptoms. However, several studies have shown that PDE5i may ameliorate the outcome of various other conditions, like heart failure and stroke. Interestingly, NO donors and cGMP analogs increase the capacity of anti-platelet drugs targeting the purinergic receptor type Y, subtype 12 (P2Y12) receptor to block platelet aggregation, and preclinical studies have shown that PDE5i inhibits platelet functions. This review summarizes the molecular mechanisms underlying the effect of PDE5i on platelet activation and aggregation focusing on the therapeutic potential of PDE5i in platelet disorders, and the outcomes of a combined therapy with PDE5i and NO donors to inhibit platelet activation.

Self-Supported Polymeric Ruthenium Complexes as Olefin Metathesis Catalysts in Synthesis of Heterocyclic Compounds

New ruthenium olefin metathesis catalysts containing N-heterocyclic carbene (NHC) connected by a linker tether to a benzylidene ligand were studied. Such obtained self-chelated Hoveyda–Grubbs type complexes existed in the form of an organometallic polymer but could still catalyze olefin metathesis after being dissolved in an organic solvent. Although these polymeric catalysts exhibited a slightly lower activity compared to structurally related nonpolymeric catalysts, they were successfully used in a number of ring-closing metathesis reactions leading to a variety of heterocyclic compounds, including biologically and pharmacologically related analogues of cathepsin K inhibitor and sildenafil (Viagra™). In the last case, a good solubility of a polymeric catalyst in toluene allowed the separation of the product from the catalyst via simple filtration.

Advanced formulations and nanotechnology-based approaches for pulmonary delivery of sildenafil: A scoping review

Oral sildenafil (SDF) is used to treat pulmonary arterial hypertension (PAH), and its bioavailability is approximately 40%. Several formulations of nano and microparticles (for pulmonary delivery) are being developed because it is possible to improve characteristics such as release time, bioavailability, dose, frequency, and even directly target the drug to the lungs. This review summarizes the latest SDF drug delivery systems for PAH and explains challenges related to the development, the preclinical, and the clinical studies. A scoping review was conducted by searching electronic databases including PubMed, Scopus, and Web of Science to identify studies published between 2001 and 2021. From 300 articles found, 31 met the inclusion criteria. This review identified colloidal formulations such as polymeric, lipid, and metal-organic framework nanoparticles. Strategies were determined to reach the deep airways such as polymeric microparticles, large porous microparticles, nanocomposites, and nano in microparticles. Finally, aspects related to toxicological, pharmacokinetics, and gaps in information for potential use in humans were discussed. SDF formulations are significant candidates for the treatment of PAH by inhalation. In summation, future preclinical studies are still required in large animals, as there is no particular formulation yet submitted to clinical studies.

A Causal Framework for Making Individualized Treatment Decisions in Oncology

Simple Summary

Physicians routinely make individualized treatment decisions by accounting for the joint effects of patient prognostic covariates and treatments on clinical outcomes. Ideally, this is performed using historical randomized clinical trial (RCT) data. Randomization ensures that unbiased estimates of causal treatment effect parameters can be obtained from the historical RCT data and used to predict each new patient’s outcome based on the joint effect of their baseline covariates and each treatment being considered. However, this process becomes problematic if a patient seen in the clinic is very different from the patients who were enrolled in the RCT. That is, if a new patient does not satisfy the entry criteria of the RCT, then the patient does not belong to the population represented by the patients who were studied in the RCT. In such settings, it still may be possible to utilize the RCT data to help choose a new patient’s treatment. This may be achieved by combining the RCT data with data from other clinical trials, or possibly preclinical experiments, and using the combined dataset to predict the patient’s expected outcome for each treatment being considered. In such settings, combining data from multiple sources in a way that is statistically reliable is not entirely straightforward, and correctly identifying and estimating the effects of treatments and patient covariates on clinical outcomes can be complex. Causal diagrams provide a rational basis to guide this process. The first step is to construct a causal diagram that reflects the plausible relationships between treatment variables, patient covariates, and clinical outcomes. If the diagram is correct, it can be used to determine what additional data may be needed, how to combine data from multiple sources, how to formulate a statistical model for clinical outcomes as a function of treatment and covariates, and how to compute an unbiased treatment effect estimate for each new patient. We use adjuvant therapy of renal cell carcinoma to illustrate how causal diagrams may be used to guide these steps.

Abstract

We discuss how causal diagrams can be used by clinicians to make better individualized treatment decisions. Causal diagrams can distinguish between settings where clinical decisions can rely on a conventional additive regression model fit to data from a historical randomized clinical trial (RCT) to estimate treatment effects and settings where a different approach is needed. This may be because a new patient does not meet the RCT’s entry criteria, or a treatment’s effect is modified by biomarkers or other variables that act as mediators between treatment and outcome. In some settings, the problem can be addressed simply by including treatment–covariate interaction terms in the statistical regression model used to analyze the RCT dataset. However, if the RCT entry criteria exclude a new patient seen in the clinic, it may be necessary to combine the RCT data with external data from other RCTs, single-arm trials, or preclinical experiments evaluating biological treatment effects. For example, external data may show that treatment effects differ between histological subgroups not recorded in an RCT. A causal diagram may be used to decide whether external observational or experimental data should be obtained and combined with RCT data to compute statistical estimates for making individualized treatment decisions. We use adjuvant treatment of renal cell carcinoma as our motivating example to illustrate how to construct causal diagrams and apply them to guide clinical decisions.

Structure-Based Design of Xanthine-Benzimidazole Derivatives as Novel and Potent Tryptophan Hydroxylase Inhibitors

Tryptophan hydroxylases catalyze the first and rate-limiting step in the synthesis of serotonin. Serotonin is a key neurotransmitter in the central nervous system and, in the periphery, functions as a local hormone with multiple physiological functions. Studies in genetically altered mouse models have shown that dysregulation of peripheral serotonin levels leads to metabolic, inflammatory, and fibrotic diseases. Overproduction of serotonin by tumor cells causes severe symptoms typical for the carcinoid syndrome, and tryptophan hydroxylase inhibitors are already in clinical use for patients suffering from this disease. Here, we describe a novel class of potent tryptophan hydroxylase inhibitors, characterized by spanning all active binding sites important for catalysis, specifically those of the cosubstrate pterin, the substrate tryptophan as well as directly chelating the catalytic iron ion. The inhibitors were designed to efficiently reduce serotonin in the periphery while not passing the blood-brain barrier, thus preserving serotonin levels in the brain.

The Interplay between cGMP and Calcium Signaling in Alzheimer’s Disease

Cyclic guanosine monophosphate (cGMP) is a ubiquitous second messenger and a key molecule in many important signaling cascades in the body and brain, including phototransduction, olfaction, vasodilation, and functional hyperemia. Additionally, cGMP is involved in long-term potentiation (LTP), a cellular correlate of learning and memory, and recent studies have identified the cGMP-increasing drug Sildenafil as a potential risk modifier in Alzheimer’s disease (AD). AD development is accompanied by a net increase in the expression of nitric oxide (NO) synthases but a decreased activity of soluble guanylate cyclases, so the exact sign and extent of AD-mediated imbalance remain unclear. Moreover, human patients and mouse models of the disease present with entangled deregulation of both cGMP and Ca²⁺ signaling, e.g., causing changes in cGMP-mediated Ca²⁺ release from the intracellular stores as well as Ca²⁺-mediated cGMP production. Still, the mechanisms governing such interplay are poorly understood. Here, we review the recent data on mechanisms underlying the brain cGMP signaling and its interconnection with Ca²⁺ signaling. We also discuss the recent evidence stressing the importance of such interplay for normal brain function as well as in Alzheimer’s disease.

Assessment of a New Formulation of Sildenafil on Common Practice: An Observational Study

Erectile dysfunction (ED) has a significant impact on the quality of life of patients. Xybilun® (IBSA Pharma SAS, France) is a new formulation of sildenafil in an orodispersible film (ODF). This study aims to assess the response rate (RR), satisfaction with, and safety of sildenafil-ODF in daily practice in France. Patients aged ≥18 years with ED were included in four groups: Group 1 mild, Group 2 moderate, Group 3 severe ED, according to the International Index for Erectile Function (IIEF)-6 subscore, never treated with phosphodiesterase inhibitors (PDE)5-I; Group 4, patients previously treated with another PDE5-I. Patients were evaluated at baseline (V1), one (V2), and three (V3) months. The RR and satisfaction were assessed using the IIEF-6 subscore questionnaire, a 5-point Likert scale, and a Global Assessment Question (GAQ). The primary endpoint for Groups 1 to 3 was the RR according to Rosen criteria at V3 compared to V1. For Group 4, the primary endpoint was the RR, defined as the satisfaction compared with previous treatment. Secondary endpoints were the RR at V2 compared to V1, the evolution of IIEF-6 and IIEF-15 scores, dose adjustment, satisfaction, convenience, and safety. One hundred and five patients were enrolled, 83 analysed. The RR at V3 was 100% (Group 1); 75% (Group 2); 65.2% (Group 3); and 84.2% (Group 4). The overall RR was 78.3%. Secondary parameters confirmed the satisfaction with sildenafil-ODF, with 81.6% of patients very satisfied at V3. No Serious Adverse Events (SAEs) were observed. In conclusion, sildenafil-ODF seems beneficial for patients irrespective of the severity of the ED. This study confirms in the context of daily clinical practice the satisfaction of patients with sildenafil-ODF. Data suggest that the availability of the intermediate dose of 75 mg could add greater flexibility to the therapy.

Long-term follow-up of retinal morphology and physiology after 2000 mg sildenafil overdose as a means of attempted suicide: a case report

Background

Few case reports have described sildenafil overdose, particularly ingestion of > 1000 mg, and overdose-induced changes in visual function remain unclear. We report retinal morphology, retinal sensitivity, and findings of electrophysiological evaluation over long-term follow-up in a case of sildenafil overdose (2000 mg).

Case presentation

Our patient developed visual abnormalities in the paracentral visual field accompanied by photophobia, decreased contrast sensitivity, and difficulty distinguishing colors in both eyes, 8 hours after the sildenafil overdose. These symptoms did not improve throughout the course, and although abnormalities of retinal morphology and sensitivity, as well as the electroretinogram findings showed slight improvement, the patient did not recover completely at 6-month follow-up.

Conclusions

We observed that high-dose sildenafil ingestion leads to retinal toxicity; the ocular abnormalities may persist for at least 6 months. Optical coherence tomography, Humphrey perimetry, microperimetry, and multifocal electroretinography are useful to quantitatively monitor temporal changes.

Construction of miRNA-regulated drug-pathway network to screen drug repurposing candidates for multiple sclerosis

ABSTRACT

Given the high disability rate of multiple sclerosis (MS), there is a need for safer and more effective therapeutic agents. Existing literature highlights the prominent roles of miRNA in MS pathophysiology. Nevertheless, there are few studies that have explored the usefulness of existing drugs in treating MS through potential miRNA-modulating abilities.The current investigation identifies genes that may exacerbate the risk of MS due to their respective miRNA associations. These findings were then used to determine potential drug candidates through the construction of miRNA-regulated drug-pathway network through genes. We uncovered a total of 48 MS risk pathways, 133 MS risk miRNAs, and 186 drugs that can affect these pathways. Potential MS risk miRNAs that are also regulated by therapeutic candidates were hsa05215 and hsa05152. We analyzed the properties of the miRNA-regulated drug-pathway network through genes and uncovered a number of novel MS agents by assessing their respective Z-values.A total of 20 likely drug candidates were identified, including human immunoglobulin, aspirin, alemtuzumab, minocycline, abciximab, alefacept, palivizumab, bevacizumab, efalizumab, tositumomab, minocycline, etanercept, catumaxomab, and sarilumab. Each of these agents were then explored with regards to their likely mechanism of action in treating MS.The current investigation provides a fresh perspective on MS biological mechanisms as well as likely treatment strategies.

Pyridylidene Amide Ru Complex for Selective Oxidation in Organic Synthesis

The ruthenium(II) bis(PYA) complex 1 (PYA = p-pyridylidene amide) is a powerful catalyst for the oxidation of sulfides to sulfones, of alkenes to carbonyl compounds, and of terminal alkynes to carboxylic acids by using NaIO₄ as the terminal oxidant. The catalytic system shows a broad functional group tolerance and rate differences between alkyne and sulfide oxidation that are sufficiently large to effectively achieve selective sulfide oxidation with exquisite selectivity.

Treatment of Poor Sperm Quality and Erectile Dysfunction With Oral Pentoxifylline: A Systematic Review

Background: Pentoxifylline (PTX) is a member of methylxanthine chemicals and a type of non-selective phosphodiesterase-5 inhibitors, which has been used in male infertility treatment to improve sperm quality and erectile dysfunction (ED) treatment. Mutually tight associations existed between ED and male infertility. Using PTX might kill two birds with one stone by improving sperm quality and erectile function in infertile men with ED. Methods: PubMed, Cochrane Library, EMBASE, and Web of Science were searched by October 2021. Based on available evidence from observational studies and randomized-controlled trials (RCTs), we conducted a systematic review to summarize the efficacy and safety of PTX in treating ED and male infertility. The protocol of the article was registered and updated in PROSPERO (CRD42021291396). Results: From 202 records, eight studies (7 RCTs) evaluating the role of PTX in ED and three studies (2 RCTs) assessing the efficacy of PTX in male infertility were included in the systematic review. Three studies (100.00%) and two studies (100.00%) reported the beneficial role of PTX in improving sperm progressive motility and normal sperm morphology rate, respectively. In contrast, only one study (33.33%) indicated the favorable role of PTX in enhancing sperm concentration. As for ED, three (60.00%) studies supported the treatment role of PTX alone in ED, and two studies (66.67%) favored the combination use of PTX and selective PDE5Is compared with selective PDE5Is alone. Safety analysis showed that PTX was a well-tolerated drug in ED and male infertility treatment. Conclusion: Given the association between ED and male infertility and satisfying findings from available evidence, PTX administration for the simultaneous treatment of poor sperm quality and mild ED in infertile men will highly enhance the treatment compliance. However, the finding should be treated carefully until validated by further studies.

Beneficial Extracardiac Effects of Cardiovascular Medications

Cardiovascular diseases are the most common cause of death worldwide, with cardiovascular medications being amongst the most common medications prescribed. These medications have diverse effects on the heart, vascular system, as well as other tissues and organ systems. The extra cardiovascular effects have been found to be of use in the treatment of non-cardiovascular diseases and pathologies. Minoxidil is used to manage systemic hypertension with its well-known side effect of hirsutism used to treat alopecia and baldness. Sildenafil was originally investigated as a treatment option for systemic hypertension; however, its side effect of penile erection led to it being widely used for erectile dysfunction. Alpha-1 blockers such as terazosin are indicated to treat systemic hypertension but are more commonly used for benign prostatic hyperplasia and post-traumatic stress disorder. Beta blockers are the mainstay treatment for congestive heart failure and systemic hypertension but have been found useful to help in patients with intention tremors as well as prophylaxis of migraines. Similarly, calcium channel blockers are indicated in medical expulsion therapy for ureteric calculi in addition to their cardiovascular indications. Thiazides are commonly used for treating systemic hypertension and as diuretics. Thiazides can cause hypocalciuria and hypercalcemia. This side effect has led to thiazides being used to treat idiopathic hypercalciuria and associated nephrolithiasis. Spironolactone is commonly utilized in treating heart failure and as a diuretic for edema. It's well described anti-androgen side effects have been used for acne vulgaris and hirsutism in polycystic ovarian syndrome. This review article discusses how the various extracardiovascular effects of commonly used cardiovascular medications are put to use in managing non-cardiovascular conditions.

Interactions between erectile dysfunction, cardiovascular disease and cardiovascular drugs

Sexual health has a fundamental role in overall health and well-being, and a healthy and dynamic sex life can make an important contribution to a good quality of life. Sexual dysfunction, and especially erectile dysfunction (ED) in men, is highly prevalent in patients with cardiovascular disease (CVD). CVD and ED have shared risk factors and pathophysiological links, such as endothelial dysfunction, inflammation and low plasma testosterone levels. ED has been shown to be an independent and early harbinger of future CVD events, providing an important window to initiate preventive measures. Therefore, screening and diagnosing ED is essential for the primary and secondary prevention of CVD because the assessment of ED offers an easy and low-cost prognostic tool that is an alternative to other investigational cardiovascular biomarkers. Moreover, ED is a major contributing factor to the discontinuation of, or poor adherence to, cardiovascular therapy. Cardiovascular drugs have divergent effects on erectile function, with diuretics and β-blockers having the worst profiles, and renin-angiotensin-aldosterone system inhibitors and nebivolol having the best profiles. Pharmacological treatment of ED has an equivocal effect on the risk of CVD, suggesting a complex interaction between ED and drugs for CVD. In this Review, we discuss how sexual function could be incorporated into the patient history taken by physicians treating individuals with CVD, not merely as part of the diagnostic work-up but as a means to pursue tangible and essential benefits in quality of life and cardiovascular outcomes.

Recreational Use of Oral PDE5 Inhibitors: The Other Side of Midnight

BACKGROUND

Nowadays, Oral phosphodiesterase type 5 inhibitors (PDE5Is) are widely used for the treatment of erectile dysfunction (ED). However, these drugs have become abused among some men for recreational use to enhance their sexual performance.

OBJECTIVE

To shed a light on the recreational use of oral PDE5Is.

METHODS

A literature review was performed in the PubMed, Medline Medical Subject Heading, Science Direct, Scopus, Cochrane Library, EMBASE, CINAHL, Academic Search Complete, Google scholar, Egyptian Knowledge Bank (EKB) databases, Medline, Embase, and Chem ID using the keywords; sexual health, erectile dysfunction, recreational use/abuse, phosphodiesterase type 5 inhibitors, sildenafil, tadalafil, vardenafil, avanafil, and adverse effects.

RESULTS

Overall, 52 studies were retained for review out of 166 papers. Twenty-two studies that assessed the prevalence of the problem were investigated including 25,279 men from different countries. Most of these studies were cross-sectional studies that depend on multiple questionnaires representing the extent as well as the attitude of the recreational use of PDE5Is.

CONCLUSION

Oral PDE5Is have become used among some men for recreational use to enhance their sexual performance. To counteract the possible side effects of such abuse, the media, as well as health authorities, should be aware of the potential adverse effects of such abuse and strengthen the regulatory activity to protect the customers from such risks. Mostafa T, Alghobary MF. Recreational Use of Oral PDE5 Inhibitors: The Other Side of Midnight. Sex Med Rev 2021;XX:XXX-XXX.

Olefin Metathesis in Continuous Flow Reactor Employing Polar Ruthenium Catalyst and Soluble Metal Scavenger for Instant Purification of Products of Pharmaceutical Interest

In recent years, the development of continuous-flow reactors has attracted growing attention from the synthetic community. Moreover, findings in the precise control of the reaction parameters and improved mass/heat transfer have made the flow setup an attractive alternative to batch reactors, both in academia and industry, enabling safe and easy scaling-up of synthetic processes. Even though a majority of the pharmaceutical industry currently rely on batch reactors or semibatch reactors, many are integrating flow technology because of easier maintenance and lower risks. Herein, we demonstrate an operationally simple flow setup for homogeneous ring-closing metathesis, which is applicable to the synthesis of active pharmaceutical ingredients precursors or analogues with high efficiency, low residence time, and in a green solvent. Furthermore, through the addition of a soluble metal scavenger in the subsequent step within the flow system, the level of ruthenium contamination in the final product can be greatly reduced (to less than 5 ppm). To ensure that this method is applicable for industrial usage, an upscale process including a 24 h continuous-flow reaction for more than 60 g of a Sildenafil analogue was achieved in a continuous-flow fashion by adjusting the tubing size and flow rate accordingly.

Sildenafil: From angina to SARS-CoV-2

Sildenafil was first examined as an alternative to nitrates for the management of angina pectoris and hypertension and eventually developed into an oral therapeutic agent used for the treatment of erectile dysfunction. There are appropriate indicators that PDE5 inhibitors may also modify the detrimental consequences of the immune system over-stimulation, supplying a new chance for their use in SARS-CoV2 patients. The use of sildenafil for the management of SARS-CoV2 has been suggested based on its several mechanisms of action and therapeutic effects and on the clinical features of SARS-CoV2 which similar to those of other pathologies treated with the PDE5 inhibitors. Here we review fundamental highlights in the enhancement of sildenafil for numerous scientific disorders and consider practicable new uses for this versatile drug.

The Sexual Long COVID (SLC): Erectile Dysfunction as a Biomarker of Systemic Complications for COVID-19 Long Haulers

Introduction

Long term complications of COVID-19, the disease caused by the SARS-CoV-2, involve many organ systems, dramatically worsening the quality of life, and finally contributing to impaired physical functioning. Despite the presence of well-identified pathogenetic mechanisms, the effect of “Long COVID” on sexual health has been only marginally addressed.

Objectives

To provide coverage of the current literature on long COVID, its epidemiology, pathophysiology, and relevance for erectile function. Methods. Comprehensive review of literature pertaining to the epidemiology and pathophysiology of long COVID, and its relevance for erectile function.

Results

Symptoms of long COVID are highly prevalent and involve almost all systems of the human body, with a plethora of clinical manifestations which range from minor nuisances to life-threatening conditions. “Brain fog” and fatigue are the most common complaints, although other neuropsychiatric complications, including sensory dysfunctions, anxiety, depression, and cerebrovascular events have also been reported. The respiratory and cardiovascular systems are also affected, with dyspnea, pulmonary fibrosis, endothelial dysfunction, and myocarditis occurring in some COVID long haulers. A subset of patients might develop endocrine manifestations, including onset of diabetes, thyroid dysfunction, and hypogonadism. Overall, long COVID features many complications which can impair erectile function by multiple pathogenetic mechanisms, and which could require tailored treatment: (i) careful investigation and management from the sexual medicine expert are therefore much needed, (ii) and future research on this topic is warranted.

Conclusion

in COVID-19 long haulers, several complications can adversely affect erectile function which, upon future tailored studies, could be used as biomarker for the severity of the long COVID disease and for its follow-up.

Sansone A, Mollaioli D, Limoncin E et al. The Sexual Long COVID (SLC): Erectile Dysfunction as a Biomarker of Systemic Complications for COVID-19 Long Haulers. Sex Med Rev 2022;10:271–285.