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Abstract Background To investigate if acute pulmonary vasodilation by sildenafil improves right ventricular function in patients with acute intermediate-high risk pulmonary embolism (PE). Methods Single center, explorative trial. Patients with PE were randomized to a single oral dose of sildenafil 50 mg (n = 10) or placebo (n = 10) as add-on to conventional therapy. The time from hospital admission to study inclusion was 2.3 ± 0.7 days. Right ventricular function was evaluated immediately before and shortly after (0.5–1.5 h) randomization by right heart catheterization (RHC), trans-thoracic echocardiography (TTE), and cardiac magnetic resonance (CMR). The primary efficacy endpoint was cardiac index measured by CMR. Results Patients had acute intermediate-high risk PE verified by computed tomography pulmonary angiography, systolic blood pressure of 135 ± 18 (mean ± SD) mmHg, increased right ventricular/left ventricular ratio 1.1 ± 0.09 and increased troponin T 167 ± 144 ng/L. Sildenafil treatment did not improve cardiac index compared to baseline (0.02 ± 0.36 l/min/m2, p = 0.89) and neither did placebo (0.00 ± 0.34 l/min/m2, p = 0.97). Sildenafil lowered mean arterial blood pressure (− 19 ± 10 mmHg, p

Abstract In various reactive oxygen species (ROS)‐based antitumor approaches (e.g., photodynamic therapy), increasing attentions are made to improve ROS level, but the short lifetime that is another decisive hurdle of ROS‐based antitumor outcomes is not even explored yet. To address it, a photocleaved O2‐released nanoplatform is constructed to release and switch ROS into reactive nitrogen species (RNS) for repressing hypoxic breast tumor. Systematic explorations validate that the nanoplatforms can attain continuous photocontrolled O2 release, alleviate hypoxia, and elevate ROS level. More significantly, the entrapped PDE5 inhibitor (PDE5‐i) in this nanoplatform can be enzymatically decomposed into nitric oxide that further combines with ROS to generate RNS, enabling the persistent antitumor effect since RNS features longer lifetime than ROS. Intriguingly, ROS conversion into RNS can help ROS to evade the hypoxia‐induced resistance to ROS‐based antitumor. Eventually, RNS production unlocks robust antitumor performances along with ROS elevation and hypoxia mitigation. Moreover, this extraordinary conversion from ROS into RNS also can act as a general method to solve the short lifetime of ROS.

In various reactive oxygen species (ROS)‐based antitumor approaches (e.g., photodynamic therapy), increasing attentions are made to improve ROS level, but the short lifetime that is another decisive hurdle of ROS‐based antitumor outcomes is not even explored yet. To address it, a photocleaved O2‐released nanoplatform is constructed to release and switch ROS into reactive nitrogen species (RNS) for repressing hypoxic breast tumor. Systematic explorations validate that the nanoplatforms can attain continuous photocontrolled O2 release, alleviate hypoxia, and elevate ROS level. More significantly, the entrapped PDE5 inhibitor (PDE5‐i) in this nanoplatform can be enzymatically decomposed into nitric oxide that further combines with ROS to generate RNS, enabling the persistent antitumor effect since RNS features longer lifetime than ROS. Intriguingly, ROS conversion into RNS can help ROS to evade the hypoxia‐induced resistance to ROS‐based antitumor. Eventually, RNS production unlocks robust antitumor performances along with ROS elevation and hypoxia mitigation. Moreover, this extraordinary conversion from ROS into RNS also can act as a general method to solve the short lifetime of ROS. [ABSTRACT FROM AUTHOR]

Background: To investigate if acute pulmonary vasodilation by sildenafil improves right ventricular function in patients with acute intermediate-high risk pulmonary embolism (PE).Methods: Single center, explorative trial. Patients with PE were randomized to a single oral dose of sildenafil 50 mg (n = 10) or placebo (n = 10) as add-on to conventional therapy. The time from hospital admission to study inclusion was 2.3 ± 0.7 days. Right ventricular function was evaluated immediately before and shortly after (0.5-1.5 h) randomization by right heart catheterization (RHC), trans-thoracic echocardiography (TTE), and cardiac magnetic resonance (CMR). The primary efficacy endpoint was cardiac index measured by CMR.Results: Patients had acute intermediate-high risk PE verified by computed tomography pulmonary angiography, systolic blood pressure of 135 ± 18 (mean ± SD) mmHg, increased right ventricular/left ventricular ratio 1.1 ± 0.09 and increased troponin T 167 ± 144 ng/L. Sildenafil treatment did not improve cardiac index compared to baseline (0.02 ± 0.36 l/min/m2, p = 0.89) and neither did placebo (0.00 ± 0.34 l/min/m2, p = 0.97). Sildenafil lowered mean arterial blood pressure (- 19 ± 10 mmHg, p < 0.001) which was not observed in the placebo group (0 ± 9 mmHg, p = 0.97).Conclusion: A single oral dose of sildenafil 50 mg did not improve cardiac index but lowered systemic blood pressure in patients with acute intermediate-high risk PE. The time from PE to intervention, a small patient sample size and low pulmonary vascular resistance are limitations of this study that should be considered when interpreting the results.Trial Registration: The trial was retrospectively registered at www.clinicaltrials.gov (NCT04283240) February 2nd 2020, https://clinicaltrials.gov/ct2/show/NCT04283240?term=NCT04283240&draw=2&rank=1 . [ABSTRACT FROM AUTHOR]

Purpose: To histopathologically and biochemically evaluate the hypothesis that tadalafil increases the uptake of a second medication into the prostate tissue by increasing the blood supply in the prostate. Methods: Forty 12-week-old Sprague Dawley male rats were equally divided into 5 groups and were administered drugs orally as follows: Group 1 - no drugs, Group 2 - 10 days of finasteride, Group 3 - 10 days of finasteride + tadalafil, Group 4 - 30 days of finasteride, and Group 5 - 30 days of finasteride + tadalafil. At the end of 10 days of drug administration in Group1, 2, and 3, and at the end of 30 days of drug administration in Group 4 and 5, blood samples were collected from rats and analyzed for serum androgen levels. In addition, prostate tissues were removed for histological examination. Results: The mean DHT level as well as the minimum and maximum epithelial thicknesses in Group 3 were lower than those in Group 2. However, there was no statistical significant difference (P = 0.989, P = 0.176, and P = 0.070, respectively). The mean DHT level as well as the minimum and maximum epithelial thicknesses in Group 5 were lower than those in Group 4. However, there was no statistical significant difference (P = 0.984, P = 0.147, and P = 0.478, respectively). The mean minimum and maximum epithelial thicknesses in Group 3 and Group 4 were not statistically different (P = 0.488 and P = 0.996, respectively). Conclusion: The similarity of the mean minimum and maximum epithelial thickness in Group 3 and Group 4 may be indicate that the combination therapy provides an early histological effect. However, the fact that there was no statistical significant difference between Group 2 and Group 3, and between Group 4 and Group 5, in terms of the mean DHT level and minimum-maximum epithelial thicknesses suggests that longer term studies with more rats are necessary to test the validity of our hypothesis. [ABSTRACT FROM AUTHOR]

Aging is associated with slower skeletal muscle O2 uptake (VO2) kinetics; however, the mechanisms underlying this effect of age are unclear. Also, the effects of exercise training in elderly on the initial vascular and metabolic response to exercise remain to be elucidated. We measured leg hemodynamics and oxidative metabolism in the transition from rest to steady-state exercise engaging the knee-extensor muscles in young (n = 15, 25 ± 1 yr) and older (n = 15, 72 ± 1 yr) subjects before and after a period of aerobic high-intensity exercise training. To enhance cGMP signaling, pharmacological inhibition of phosphodiesterase 5 (PDE5) was performed. Before training, the older group had a slower (P <0.05) increase in femoral arterial blood flow and leg vascular conductance in the transition from rest to steady-state exercise at low- and moderate-intensity compared with the young group. The rate of increase in leg VO2 was, however, similar in the two groups as a result of higher (P < 0.05) arteriovenous O2 difference in the older group. Potentiation of cGMP signaling did not affect the rate of increase in blood flow or VO2 in either group. Exercise training augmented (P < 0.05) the increase in leg vascular conductance and blood flow during the onset of moderate- intensity exercise in both groups without altering VO2. These findings suggest that an age-related reduction in the initial vascular response to low- and moderate-intensity knee-extensor exercise is not limiting for VO2 in older individuals. A lower blood flow response in aging does not appear to be a result of reduced cGMP signaling. [ABSTRACT FROM AUTHOR]

We have identified chemical probes that act as dual phosphodiesterase 5 (PDE5) and histone deacetylase 6 (HDAC6)-selective inhibitors (>1 log unit difference versus class I HDACs) to decipher the contribution of HDAC isoforms to the positive impact of dual-acting PDE5 and HDAC inhibitors on mouse models of Alzheimer's disease (AD) and fine-tune this systems therapeutics approach. Structure- and knowledge-based approaches led to the design of first-in-class molecules with the desired target compound profile: dual PDE5 and HDAC6-selective inhibitors. Compound 44b , which fulfilled the biochemical, functional and ADME-Tox profiling requirements and exhibited adequate pharmacokinetic properties, was selected as pharmacological tool compound and tested in a mouse model of AD (Tg2576) in vivo . [ABSTRACT FROM AUTHOR]

T helper 1 (Th1) type cytokines and chemokines are bioactive mediators in inflammation underling several diseases and co-morbid conditions, such as cardiovascular and metabolic disorders. Th1 chemokine CXCL10 participates in heart damage initiation/progression; cardioprotection has been recently associated with sildenafil, a type 5 phosphodiesterase inhibitor. We aimed to evaluate the effect of sildenafil on CXCL10 in inflammatory conditions associated with diabetic cardiomyopathy. We analyzed: CXCL10 gene and protein in human cardiac, endothelial, and immune cells challenged by pro-inflammatory stimuli with and without sildenafil; serum CXCL10 in diabetic subjects at cardiomyopathy onset, before and after 3 months of treatment with sildenafil vs. placebo. Sildenafil significantly decreased CXCL10 protein secretion (IC = 2.6 × 10) and gene expression in human cardiomyocytes and significantly decreased circulating CXCL10 in subjects with chemokine basal level ≥ 930 pg/ml, the cut-off value as assessed by ROC analysis. In conclusion, sildenafil could be a pharmacologic tool to control CXCL10-associated inflammation in diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

Background Fibrotic diseases encompass numerous systemic and organ-specific disorders characterized by the development and persistence of myofibroblasts. TGFβ1 is considered the key inducer of fibrosis and drives myofibroblast differentiation in cells of diverse histological origin by a pro-oxidant shift in redox homeostasis associated with decreased nitric oxide (NO)/cGMP signaling. Thus, enhancement of NO/cGMP represents a potential therapeutic strategy to target myofibroblast activation and therefore fibrosis. Methods Myofibroblast differentiation was induced by TGFβ1 in human primary prostatic (PrSCs) and normal dermal stromal cells (NDSCs) and monitored by α smooth muscle cell actin (SMA) and IGF binding protein 3 (IGFBP3) mRNA and protein levels. The potential of enhanced cGMP production by the sGC stimulator BAY 41-2272 or the sGC activator BAY 60-2770 to inhibit and revert myofibroblast differentiation in vitro was analyzed. Moreover, potential synergisms of BAY 41-2272 or BAY 60-2770 and inhibition of cGMP degradation by the PDE5 inhibitor vardenafil were investigated. Results BAY 41-2272 and BAY 60-2770 at doses of 30 µM significantly inhibited induction of SMA and IGFBP3 levels in PrSCs and reduced myofibroblast marker levels in TGFβ1-predifferentiated cells. At lower concentrations (3 and 10 µM) only BAY 41-2272 but not BAY 60-2770 significantly inhibited and reverted myofibroblast differentiation. In NDSCs both substances significantly inhibited differentiation at all concentrations tested. Attenuation of SMA expression was more pronounced in NDSCs whereas reduction of IGFBP3 levels by BAY 41-2272 appeared more efficient in PrSCs. Moreover, administration of BAY 41-2272 or BAY 60-2770 enhanced the efficiency of the PDE5 inhibitor vardenafil to inhibit and revert myofibroblast differentiation in vitro. Conclusions Increase of cGMP by sGC stimulation/activation significantly inhibited and reverted myofibroblast differentiation. This effect was even more pronounced when a combination treatment with a PDE5 inhibitor was applied. Thus, enhancement of NO/cGMP-signaling by sGC stimulation/activation is a promising strategy for the treatment of fibrotic diseases. Whereas, in NDSCs BAY 60-2770 and BAY 41-2272 exerted similar effects on myofibroblast differentiation, higher potency of BAY 41-2272 was observed in PrSCs, indicating phenotypical differences between fibroblasts form different organs that should be taken into account in the search for antifibrotic therapies. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO)-induced coronary vasodilation is mediated through production of cyclic guanosine monophosphate (cGMP) and through inhibition of the endothelin-1 (ET) system. We previously demonstrated that phosphodiesterase-5 (PDE5)-mediated cGMP breakdown and ET each exert a vasoconstrictor influence on coronary resistance vessels. However, little is known about the integrated control of coronary resistance vessel tone by these two vasoconstrictor mechanisms. In the present study, we investigated the contribution of PDE5 and ET to the regulation of coronary resistance vessel tone in swine both in vivo, at rest and during graded treadmill exercise, and in vitro. ETA/ETB receptor blockade with tezosentan (3 mg/kg iv) and PDE5 inhibition with EMD360527 (300 μg·min-1·kg-1 iv) each produced coronary vasodilation at rest and during exercise as well as in preconstricted isolated coronary small arteries. In contrast, tezosentan failed to produce further coronary vasodilation in the presence of EMD360527, both in vivo and in vitro. Importantly, EMD360527 (3 μM) and cGMP analog 8-Br-cGMP (100 μM) had no significant effects on ET-induced contractions of isolated porcine coronary small arteries, suggesting unperturbed ET receptor responsiveness. In contrast, PDE5 inhibition and cGMP blunted the contractions produced by the ET precursor Big ET, but only in vessels with intact endothelium, suggesting that PDE5 inhibition limited ET production in the endothelium of small coronary arteries. In conclusion, PDE5 activity exerts a vasoconstrictor influence on coronary resistance vessels that is mediated, in part, via an increase in endothelial ET production. [ABSTRACT FROM AUTHOR]

Abstract: Sildenafil citrate increases ocular blood flow and accelerates the rate of anterior chamber refilling after paracentesis. The latter effect could have resulted from a reduction in outflow facility or from an increase in aqueous humor (AH) production. In this study, we used scanning ocular fluorophotometry to examine the effects of sildenafil on AH turnover, and thus, AH production in eyes of live normal rabbits. For this, the rate of aqueous humor flow (AHF) was quantified with a commercially available fluorophotometer that measured the rate of fluorescein clearance from the anterior segment, which predominantly occurs via the trabecular meshwork. After ≈2 h of control scans to determine the baseline rate of AHF, the rabbits were fed 33 mg of sildenafil and allowed ≈45 min for the drug to enter the systemic circulation. Thereafter, fluorescence scans were retaken for an additional 90–120 min. Sildenafil ingestion increased AHF by about 36%, from 2.31 μL/min to 3.14 μL/min (P < 0.001, as two-tailed paired data, n = 20 eyes). This observation indicates that sildenafil citrate, which is a phosphodiesterase type-5 inhibitor currently marketed as a vasodilator (e.g., Viagra, Revatio), stimulates AHF in rabbits. Our results seem consistent with reports indicating that the drug dilates intraocular arteries and augments intraocular vascular flow. These physiological responses to the agent apparently led to increased fluid entry into the anterior chamber. As such, the drug might have utility in patients with ocular hypotony resulting from insufficient AH formation. [Copyright &y& Elsevier]

Background: Sildenafil treatment ameliorates progressive renal injury resulting from extensive renal ablation; however, modifications induced by sildenafil in the glomerular hemodynamic pathophysiology of the remnant kidney have not been investigated. Aim: To determine the effects of sildenafil in the glomerular microcirculation and their relation to histological damage in the renal ablation model. Methods: Micropuncture studies were performed 60 days after 5/6 nephrectomy in rats that received no treatment, sildenafil (5 mg/kg/day) and reserpine, hydralazine and hydrochlorothiazide to maintain the blood pressure within normal levels. Sham-operated rats untreated and treated with sildenafil served as controls. Results: As expected, renal ablation induced systemic and glomerular hypertension, hyperfiltration, proteinuria, glomerulosclerosis and tubulointerstitial inflammatory damage in the remnant kidney. Sildenafil treatment prevented single-nephron hyperfiltration and hypertension, suppressed renal arteriolar remodeling, ameliorated systemic hypertension and proteinuria, increased urinary excretion of cGMP and NO2-/NO3-, decreased oxidative stress and improved histological damage in the remnant kidney. Normalization blood pressure with reserpine, hydralazine and hydrochlorothiazide did not modify glomerular hemodynamics, proteinuria or histological changes induced by renal ablation. Conclusions: Beneficial effects of sildenafil in the remnant kidney are associated with a reduction in the arteriolar remodeling, renal inflammatory changes and prevention of changes in the glomerular microcirculation. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Aims Exercise oscillatory breathing (EOB) is a ventilatory abnormality that occurs in ∼20% of heart failure (HF) patients and carries a very unfavourable prognosis. Pulmonary vasoconstriction has been suggested to be involved in this disorder. We hypothesized that modulation of pulmonary vascular hypertone by oversignalling of the nitric oxide pathway with phosphodiesterase 5 (PDE5) inhibition might be beneficial. Accordingly, we performed a 1-year pilot trial with sildenafil in patients with HF and EOB. Methods and results Among 122 HF cases, 32 presented with EOB during cardiopulmonary exercise testing (CPX) and were randomized to receive placebo (n = 16) or sildenafil (n = 16) at the dose of 50 mg three times a day, in addition to their current antifailure treatment. CPX-derived variables and pulmonary haemodynamics were assessed at 6 and 12 months. Sildenafil reversed EOB in 87% of patients at 6 months and 93% at 1 year, respectively (P < 0.01). This effect was accompanied by an improvement in functional performance (peak VO2; from 9.6 to 12.4 and 13.2 mL/min/kg; P < 0.01) and exercise ventilation efficiency (ventilation to CO2 production slope; from 41.1 to 32.7 and 31.5; P < 0.01). Chronic treatment with PDE5 inhibition significantly decreased pulmonary capillary wedge pressure (from 21 to 14 and 14 mmHg), mean pulmonary artery pressure (PAP; from 34.8 to 23 and 24 mmHg), and pulmonary vascular resistance (PVR; from 360 to 270 and 266 dyne/s/cm5) compared with placebo (P < 0.01 for each comparison). On exploratory analysis, there was a correlation between PAP and PVR and the decrease in EOB in the treatment group. Placebo did not alter any of the aforementioned variables. Conclusions PDE5 inhibition in HF patients with EOB offers the dual advantage of improving functional capacity and modulating the EOB pattern. PAP and PVR reduction seem to underlie the correction of the breathing disorder. Whether reversal of this unfavourable prognostic signal can affect survival remains unconfirmed at the moment. [ABSTRACT FROM AUTHOR]

Abstract: Anecdotal reports have suggested that the vasodilator, sildenafil citrate, which evokes its effect via a select inhibition of PDE5, has the potential to increase intraocular pressure (IOP) in some individuals. An ocular hypertensive effect by sildenafil was also recently described in a sheep animal model. In contrast, clinical studies have not found a direct association between sildenafil ingestion (commonly consumed as Viagra) and changes in IOP. However, some such studies also reported no effects of sildenafil on systemic blood pressure (BP) at the time of the IOP determination. Given this surprising result, our purpose was to repeat a study in human volunteers in the city of Corrientes, Argentina to corroborate the effects of sildenafil on human IOP and systemic BP. For the present study, 9 healthy volunteers (male and female, 18–74 years old) were selected as subjects after ophthalmic and cardiovascular evaluation indicated that they exhibited normal parameters for their age. In a masked, placebo-controlled study, the subjects ingested 100 mg sildenafil citrate (provided as Vorst from Laboratorios Bernabo, Argentina) in one session, and a placebo on a second separate occasion. IOP was measured with a Goldman applanation tonometer by an ophthalmologist, and BP by a second physician, neither of whom witnessed the tablet ingestion by the volunteers, nor provided with information on the nature of the test compounds. A third individual administered the tablets. The average baseline IOP of this group of 9 was 13.1 ± 0.6 mm Hg. Subsequent to sildenafil ingestion, IOP increased by 26% to 16.5 ± 0.8 mm Hg 60 min later (P < 0.005, as paired data), and returned to control values within 2 h. Both systolic and diastolic BP were significantly reduced by sildenafil ingestion. At the point of maximal systemic hypotension (90 min), the systolic and diastolic pressures declined by 15% and 13%, respectively. No significant changes in IOP or BP were recorded after ingestion of the placebo. Our results suggest that sildenafil can elicit a transient IOP increase that may be of importance to patients chronically treated with PDE5 inhibitors for various vascular diseases (e.g., pulmonary hypertension). We discuss possible mechanisms by which PDE5 inhibition might lead to a rise in IOP. [Copyright &y& Elsevier]

The article presents a study which investigated the effects of phosphodiesterase type 5 (PDE5) inhibition and its possible benefits in treating heart failure. Using a prospective, randomized, placebo-controlled cohort study, the authors tested the effects of sildenafil, a PDE5 inhibitor, on left ventricular ejection fraction, diastolic function, cardiac geometry, and clinical status. Their results showed improved functional capacity and clinical status with use of PDE5 inhibition.

Abstract: The synthesis of novel tadalafil analogues in which the benzodioxole moiety is replaced by 2-bromophenyl; the chiral carbons swing from R,R to R,S, S,R and S,S; the piperazinedione ring is maintained or reduced to the 5-membered imidazolidinedione or thioxoimidazolinone is described. The prepared analogues were evaluated for their capacity to inhibit the cyclic guanosine monophosphate (cGMP) selective phosphodiesterase 5 (PDE5) isozyme and the growth of human HT-29 colon adenocarcinoma cells. The R absolute configuration of C-5 in the β-carboline-hydantoin and C-6 in the β-carboline-piperazinedione derivatives was found to be essential for the PDE5 inhibition. In addition, tadalafil analogues that were synthesized from l-tryptophan were more active than those derived from d-tryptophan, which is of economic value and expands the horizon for the discovery of new carbolines as PDE5 inhibitors. While some analogues displayed potent tumor cell growth inhibitory activity, there was no apparent correlation with their PDE5 inhibitory activity, which leads us to conclude that other PDE isozymes or PDE5 splice variants may be involved. [Copyright &y& Elsevier]

Abstract: Several different heterocyclic systems were compared as PDE5 inhibitor scaffolds. In addition to the known 3H-imidazo[5,1-f][1,2,4]triazin-4-ones and pyrazolopyrimidinones, isomeric imidazo[1,5-a][1,3,5]triazin-4(3H)-ones were also shown to be potent and selective PDE inhibitor scaffolds with in vivo activity. SAR trends were elucidated for sulfonamide derivatives with generality across different scaffolds. [Copyright &y& Elsevier]

Three new compounds including two depsidones (simplicildones J and K) and one dihydroxanthenone (globosuxanthone E) together with nine known compounds were obtained from the crude extracts of two endophytic fungi Simplicillium lanosoniveum (J.F.H. Beyma) Zare & W. Gams PSU-H168 and PSU-H261 which were isolated from the leaves of Hevea brasiliensis. The structures were elucidated by spectroscopic evidence. The absolute configuration of globosuxanthone E was established by means of experimental and calculated TDDFT ECD data. Simplicildone K exhibited antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus with equal MIC values of 128 μg/mL. Simplicildone K and globosuxanthone E displayed antifungal activity against Cryptococcus neoformans ATCC90113 with the same MIC values of 32 μg/mL. In addition, known botryohordine C and simplicildone A showed phosphodiesterase 5 inhibitory activity with the IC 50 values of 5.69 and 9.96 μM, respectively, and were noncytotoxic toward noncancerous Vero cells. Unlabelled Image [ABSTRACT FROM AUTHOR]

In order to determine the contributions of histone deacetylase (HDAC) isoforms to the beneficial effects of dual phosphodiesterase 5 (PDE5) and pan-HDAC inhibitors on in vivo models of Alzheimer's disease (AD), we have designed, synthesized, and tested novel chemical probes with the desired target compound profile of PDE5 and class I HDAC selective inhibitors. Compared to previous hydroxamate-based series, these molecules exhibit longer residence times on HDACs. In this scenario, shorter or longer preincubation times may have a significant impact on the IC 50 values of these compounds and therefore on their corresponding selectivity profiles on the different HDAC isoforms. On the other hand, different chemical series have been explored and, as expected, some pairwise comparisons show a clear impact of the scaffold on biological responses (e.g., 35a vs 40a). The lead identification process led to compound 29a, which shows an adequate ADME-Tox profile and in vivo target engagement (histone acetylation and cAMP/cGMP response element-binding (CREB) phosphorylation) in the central nervous system (CNS), suggesting that this compound represents an optimized chemical probe; thus, 29a has been assayed in a mouse model of AD (Tg2576).

Through drug discovery strategies of repurposing and redeveloping existing drugs, a series of novel tadalafil derivatives were rationally designed, synthesized, and evaluated to seek dual-target AChE/PDE5 inhibitors as good candidate drugs for Alzheimer's disease (AD). Among these derivatives, 1p and 1w exhibited excellent selective dual-target AChE/PDE5 inhibitory activities and improved blood-brain barrier (BBB) penetrability. Importantly, 1w·Cit (citrate of 1w) could reverse the cognitive dysfunction of scopolamine-induced AD mice and exhibited an excellent effect on enhancing cAMP response element-binding protein (CREB) phosphorylation in vivo, a crucial factor in memory formation and synaptic plasticity. Moreover, the molecular docking simulations of 1w with hAChE and hPDE5A confirmed that our design strategy was rational. In summary, our research provides a potential selective dual-target AChE/PDE5 inhibitor as a good candidate drug for the treatment of AD, and it could also be regarded as a small molecule probe to validate the novel AD therapeutic approach in vivo.