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Background: PDE1 (phosphodiesterase type 1) hydrolyzes cyclic adenosine and guanosine monophosphate. ITI-214 is a highly selective PDE1 inhibitor that induces arterial vasodilation and positive inotropy in larger mammals. Here, we assessed pharmacokinetics, hemodynamics, and tolerability of single-dose ITI-214 in humans with stable heart failure with reduced ejection fraction., Methods: Patients with heart failure with reduced ejection fraction were randomized 3:1 to 10, 30, or 90 mg ITI-214 single oral dose or placebo (n=9/group). Vital signs and electrocardiography were monitored predose to 5 hours postdose and transthoracic echoDoppler cardiography predose and 2-hours postdose., Results: Patient age averaged 54 years; 42% female, and 60% Black. Mean systolic blood pressure decreased 3 to 8 mm Hg ( P <0.001) and heart rate increased 5 to 9 bpm ( P ≤0.001 for 10, 30 mg doses, RM-ANCOVA). After 4 hours, neither blood pressure or heart rate significantly differed among cohorts (supine or standing). ITI-214 increased mean left ventricular power index, a relatively load-insensitive inotropic index, by 0.143 Watts/mL 2 ·10 4 ( P =0.03, a +41% rise; 5-71 CI) and cardiac output by 0.83 L/min ( P =0.002, +31%, 13-49 CI) both at the 30 mg dose. Systemic vascular resistance declined with 30 mg (-564 dynes·s/cm- 5 , P <0.001) and 90 mg (-370, P =0.016). Diastolic changes were minimal, and no parameters were significantly altered with placebo. ITI-214 was well-tolerated. Five patients had mild-moderate hypotension or orthostatic hypotension recorded adverse events. There were no significant changes in arrhythmia outcome and no serious adverse events., Conclusions: Single-dose ITI-214 is well-tolerated and confers inodilator effects in humans with heart failure with reduced ejection fraction. Further investigations of its therapeutic utility are warranted. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03387215.

Phosphodiesterase (PDE) inhibitors, such as pentoxifylline (PTX), are used as pharmacological agents to enhance sperm motility in assisted reproductive technology (ART), mainly to aid the selection of viable sperm in asthenozoospermic ejaculates and testicular spermatozoa, prior to intracytoplasmic sperm injection (ICSI). However, PTX is reported to induce premature acrosome reaction (AR) and, exert toxic effects on oocyte function and early embryo development. Additionally, in vitro binding studies as well as computational binding free energy (ΔG bind ) suggest that PTX exhibits weak binding to sperm PDEs, indicating room for improvement. Aiming to reduce the adverse effects and to enhance the sperm motility, we designed and studied PTX analogues. Using structure-guided in silico approach and by considering the physico-chemical properties of the binding pocket of the PDEs, designed analogues of PTX. In silico assessments indicated that PTX analogues bind more tightly to PDEs and form stable complexes. Particularly, ex vivo evaluation of sperm treated with one of the PTX analogues (PTXm-1), showed comparable beneficial effect at much lower concentration-slower AR, higher DNA integrity and extended longevity of  spermatozoa and  superior embryo quality. PTXm-1 is proposed to be a better pharmacological agent for ART than PTX for sperm function enhancement.

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is a promising target for anticancer therapy due to its ability to counter the effects topoisomerase 1 (Top1) poison, such as topotecan, thus, decreasing their efficacy. Compounds containing adamantane and monoterpenoid residues connected via 1,2,4-triazole or 1,3,4-thiadiazole linkers were synthesized and tested against Tdp1. All the derivatives exhibited inhibition at low micromolar or nanomolar concentrations with the most potent inhibitors having IC 50 values in the 0.35-0.57 µM range. The cytotoxicity was determined in the HeLa, HCT-116 and SW837 cancer cell lines; moderate CC 50 (µM) values were seen from the mid-teens to no effect at 100 µM. Furthermore, citral derivative 20c , α-pinene-derived compounds 20f , 20g and 25c, and the citronellic acid derivative 25b were found to have a sensitizing effect in conjunction with topotecan in the HeLa cervical cancer and colon adenocarcinoma HCT-116 cell lines. The ligands are predicted to bind in the catalytic pocket of Tdp1 and have favorable physicochemical properties for further development as a potential adjunct therapy with Top1 poisons.

Introduction: The ATX-LPA axis is an attractive target for therapeutic intervention in a variety of diseases, such as tumor metastasis, fibrosis, pruritus, multiple sclerosis, inflammation, autoimmune conditions, metabolic syndrome, and so on. Accordingly, considerable efforts have been devoted to the development of new chemical entities capable of modulating the ATX-LPA axis., Areas Covered: This review aims to provide an overview of novel ATX inhibitors reported in patents from September 2016 to August 2020, discussing their structural characteristics and inhibitory potency in vitro and in vivo ., Expert Opinion: In the past four years, the classification of ATX inhibitors based on binding modes has brought great benefits to the discovery of more efficacious inhibitors. In addition to GLPG1690 currently in phase III clinical studies for IPF, BBT-877, and BLD-0409 as potent ATX inhibitors have been enrolled in phase I clinical evaluation; meanwhile, many effective molecules were also reported successively. However, most emerging ATX inhibitors in the last four years are closely analogs of previous entities, such as GLPG1690 and PF-8380, which translate into the urgently identification of ATX inhibitors with diverse structural features and promising properties in the near future.

Introduction: Cyclic nucleotides, cAMP, and cGMP, are important second messengers of intracellular signaling and play crucial roles in cardiovascular biology and diseases. Cyclic nucleotide phosphodiesterases (PDEs) control the duration, magnitude, and compartmentalization of cyclic nucleotide signaling by catalyzing the hydrolysis of cyclic nucleotides. Individual PDEs modulate distinct signaling pathways and biological functions in the cell, making it a potential therapeutic target for the treatment of different cardiovascular disorders. The clinical success of several PDE inhibitors has ignited continued interest in PDE inhibitors and in PDE-target therapeutic strategies., Areas Covered: This review concentrates on recent research advances of different PDE isoforms with regard to their expression patterns and biological functions in the heart. The limitations of current research and future directions are then discussed. The current and future development of PDE inhibitors is also covered., Expert Opinion: Despite the therapeutic success of several marketed PDE inhibitors, the use of PDE inhibitors can be limited by their side effects, lack of efficacy, and lack of isoform selectivity. Advances in our understanding of the mechanisms by which cellular functions are changed through PDEs may enable the development of new approaches to achieve effective and specific PDE inhibition for various cardiac therapies.

This study investigated the effects of the n -BuOH soluble fraction of Polygoni Cuspidati 80% ethanol extract (POCU1b) on high-fat diet (HFD)-induced obesity, non-alcoholic fatty liver (NAFL), and insulin resistance (IR) to find a safe and more effective agent. HPLC profiling of POCU1b identified seven marker compounds. POCU1b increased glycerol release, cyclic adenosine monophosphate (cAMP) level, and inhibited phosphodiesterase (PDE) activity. Seven weeks of POCU1b treatment decreased body weight gain, weight and adipocyte size in fat tissues, serum lipids, and triglyceride and lipid droplets in the livers of HFD-fed rats. POCU1b improved blood glucose, insulin sensitivity, and impaired insulin secretion in the pancreas. Further, POCU1b ameliorated adiponectin, leptin, IL-6 and TNF-α levels, increased AMPK and p-ACC expression, activated CPT-1 activity, and suppressed FAS mRNA, SOCS-3 protein expression, and NF-κB DNA-binding activity. When compared with the Xenical ® -treated group, a positive group, the action of POCU1b on body weight was more effective than that of Xenical. POCU1b did not show side effects, such as oily spotting and loss of appetite. These results suggest that POCU1b possesses therapeutic or preventive potential for obesity, NAFL and IR via inhibitions of pancreatic lipase and cAMP-dependent PDE activity, AMPK activation, and SOCS-3 suppression, without oily spotting and loss of appetite.

Hybrid molecules created from different pharmacophores of natural and synthetic equivalents are successfully used in pharmaceutical practice. One promising target for anticancer therapy is tyrosyl-DNA phosphodiesterase 1 (Tdp1) because it can repair DNA lesions caused by DNA-topoisomerase 1 (Top1) inhibitors, resulting in drug resistance. In this study, new hybrid compounds were synthesized by combining the pharmacophoric moiety of a set of natural compounds with inhibitory properties against Tdp1, particularly, phenolic usnic acid and a set of different monoterpenoid fragments. These fragments were connected through a hydrazinothiazole linker. The inhibitory properties of the new compounds mainly depended on the structure of the terpenoid moieties. The two most potent compounds, 9a and 9b , were synthesized from citral and citronellal, which contain acyclic fragments with IC 50 values in the range of 10-16 nM. Some synthesized derivatives showed low cytotoxicity against HeLa cells and increased the effect of the Top1 inhibitor topotecan in vitro by three to seven times. These derivatives may be considered as potential agents for the development of anticancer therapies when combined with Top1 inhibitors.

Spiroconyone A (1), the first rearranged phytosterol featuring an unusual spiro [5,6] ring system, and nine known compounds (2-10) were isolated from the aerial parts of Conyza japonica. The structure of 1 was elucidated through spectroscopic methods, and its absolute configuration was determined by single-crystal X-ray diffraction analysis. Enzyme-based assay revealed that spiroconyone A showed weak TDP1 inhibition and compounds 7 and 10 showed TDP1 inhibition with IC50 values of 36 μM and 16 μM, respectively. MTT assay indicated that 7 and 10 showed a strong synergistic effect with the clinical TOP1 inhibitor topotecan in MCF-7 cells. Compound 5 displayed the most potent cytotoxicity against MCF-7 cells with a GI50 value of 3.3 μM. Furthermore, a hypothetical biosynthetic pathway for 1 was proposed. This work provides valuable information that the secondary metabolites from Conyza japonica could be developed as anticancer agents.

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent disease linked to insulin resistance, oxidative stress, and cytokine imbalance. Phosphodiesterase (PDE) inhibitors have shown remarkable antioxidant and anti-inflammatory potential in different disease sets including liver diseases. This study aimed to compare the ameliorative effect of different PDE inhibitors on a high-fat diet (HFD)-induced NAFLD. Male Wistar rats were fed a HFD for 16 weeks to induce NAFLD, and then, oral treatments of a vehicle or different PDE inhibitors (pentoxifylline (50 mg/kg), cilostazol (20 mg/kg), or sildenafil (5 mg/kg)) were started in the last four weeks and given on a daily basis. Rats' body composition and liver indices were recorded. Serum levels of liver enzymes, glucose, insulin, bilirubin, total cholesterol, triglycerides, and nitric oxide were measured. Liver tissues were used for histopathological examination and detecting oxidative stress and inflammatory markers. Results showed that different PDE inhibitors exhibited different efficacy against liver injury and metabolic disorders associated with HFD-induced NAFLD in rodents evident by different strength-ameliorated effects on the aforementioned parameters. Compared to cilostazol and sildenafil, insulin resistance, hepatic oxidative stress, and inflammatory markers were significantly reduced by pentoxifylline treatment. Furthermore, pentoxifylline nearly completely reversed hepatocyte steatosis and exhibited superior rectifying effect on the rats' liver status compared with other PDE inhibitors. This investigation highlighted the potential role of PDE inhibitors in NAFLD treatment. Pentoxifylline had the most remarkable ameliorative effects against NAFLD, while sildenafil was the least effective., (© 2019 Société Française de Pharmacologie et de Thérapeutique.)

Phosphodiesterase 10 (PDE10) inhibitors have received much attention as promising therapeutic agents for central nervous system (CNS) disorders such as schizophrenia and Huntington's disease. Recently, a hit compound 1 with a novel chromone scaffold has shown moderate inhibitory activity against PDE10A (IC 50 = 500 nM). Hit-to-lead optimization has resulted in compound 3e with an improved inhibitory activity (IC 50 = 6.5 nM), remarkable selectivity (>95-fold over other PDEs), and good metabolic stability (RLM t 1/2 = 105 min) by using an integrated strategy (molecular modeling, chemical synthesis, bioassay, and cocrystal structure). The cocrystal structural information provides insights into the binding pattern of 3e in the PDE10A catalytic domain to highlight the key role of the halogen and hydrogen bonds toward Tyr524 and Tyr693, respectively, thereby resulting in high selectivity against other PDEs. These new observations are of benefit for the rational design of the next generation PDE10 inhibitors for CNS disorders.

Introduction : Phosphodiesterase 10 (PDE10) is one of at least 11 different PDE families, which are the enzymes that degrade adenosine 3',5'-cyclic monophosphate (cAMP) and/or guanosine 3',5'-cyclic monophosphate (cGMP) by hydrolyzing the phosphodiester bonds. Inhibition of PDE10A represents a molecular target in the treatment of conditions that would benefit from the increase of the level of cAMP and/or cGMP such as neurological and psychiatric disorders, cancer, and diabetes. Areas covered : The present article reviews the patent literature on PDE10A inhibitors (PDE10AIs) from 2014 to present and PDE10AI chemotypes from different chemical classes: heteroaryl- and aryl-nitrogen-heterocyclic compounds, unsaturated nitrogen-heterocyclic compounds with specific substituents such as pyrazolopyrimidine, aryloxymethyl cyclopropane, pyridizinone, imidazopyridine, triazoles and imidazo[2,1-a]isoidole. The article presents the potency of PDE10AIs, their efficacy in animal models, and their clinical utility in the treatment of schizophrenia. Therapeutic patents for the treatment of cancers, precancerous conditions, and diabetes were also collected. Expert opinion : Several potent PDE10AIs have been described so far; however, clinical trials have shown that without preclinical optimization, the benefit of PDE10AIs in the treatment of schizophrenia is confounded by a high placebo effect. Understanding of the requirements for PDE10AIs constitutes a challenging but promising field of drug discovery and development.

Background: Tissue fibrosis is the final common phase of chronic allograft injury, the leading cause of late graft loss in kidney transplantation. Preclinical evidence points to the involvement of lysophosphatidic acid (LPA), a bioactive phospholipid, in the development of renal fibrosis., Objectives: We assessed whether treatment with an orally available inhibitor of autotaxin (ATXi), the main LPA-producing enzyme, could slow the progression of chronic allograft injury in a fully major histocompatibility complex-mismatched rat kidney transplant model and compared its effects with those of the angiotensin-converting enzyme inhibitor lisinopril., Methods: Kidney allograft recipients were given ciclosporin for the first 15 postoperative days to prevent early acute rejection. Thereafter, they received either no treatment or ATXi or lisinopril and were followed for 180 days after transplantation., Results: Renal LPA levels were increased in allograft rats, providing the rationale for using ATXi in this model. Chronic treatment with ATXi or lisinopril limited progressive proteinuria and ameliorated tubulointerstitial fibrosis compared with allograft rats, although the effects were more robust under ATX inhibition. The administration of ATXi, but not lisinopril, attenuated systemic hypertension, reduced intragraft T cell infiltration, and eventually improved renal graft survival., Conclusions: In summary, ATXi had protective effects on indices of chronic allograft injury and could be of therapeutic add-on value in the kidney transplant setting. Notably, an ATX inhibitor is currently being investigated in 2 large phase 3 studies in idiopathic pulmonary fibrosis, underscoring the clinical relevance of our findings., (© 2019 S. Karger AG, Basel.)

Background: Current treatments for psychotic symptoms associated with schizophrenia often provide inadequate efficacy with unacceptable adverse effects. Improved therapeutics have long been a goal of research. Preclinical testing suggests that phosphodiesterase 10A (PDE10A) inhibitors may provide a novel approach to treating psychosis associated with schizophrenia., Methods: The efficacy and safety of a highly selective PDE10A inhibitor, PF-02545920, was evaluated in a phase 2 multicenter, randomized, double-blind, placebo-controlled, parallel-group study. Eligible patients (18-65 years) with an acute exacerbation of schizophrenia were randomized 2:2:1:2 to PF-02545920 (5 or 15 mg every 12 hours [Q12H] titrated), risperidone (3 mg Q12H), or placebo for 28 days (n = 74:74:37:74). The primary objectives were to evaluate the efficacy of PF-02545920 using the Positive and Negative Syndrome Scale (PANNS) and safety/tolerability., Results: At day 28, PF-02545920 (either dose) was not significantly different from placebo for mean change from baseline in the PANNS total score (primary end point) or most other end points. Pharmacokinetics exposures seemed adequate for binding/inhibiting PDE10A enzyme. Risperidone was statistically different from placebo for the PANNS total score, demonstrating study sensitivity. Incidence rates for adverse events were similar among the groups. Both doses of PF-02545920 were generally well tolerated. Dystonia occurred in 1, 6, 0, and 3 patients in the PF-02545920 5 mg Q12H, PF-02545920 15 mg Q12H, risperidone, and placebo groups, respectively., Conclusions: Neither dose of PF-02545920 was superior to placebo for the primary and most secondary end points. This indicates that PDE10A inhibition does not produce an antipsychotic effect in patients with acute exacerbation of schizophrenia.

Phosphodiesterase (PDE) inhibition has been broadly investigated as a target for a wide variety of indications including central nervous system (CNS) disorders. Cyclic nucleotide (cNT) changes within associated tissues may serve as a biomarker of PDE inhibition. We recently developed robust sample harvesting and bioanalytical methods to quantify cNT levels in rodent brain and cerebrospinal fluid (CSF). Herein, we report on the application of those methods to study rodent species-specific and rodent brain region-specific cNT changes following individual or concomitant PDE inhibitor administration. Male Sprague Dawley (Crl:CD ® [SD]) rats were dosed subcutaneously (sc) with a PDE1B inhibitor (DNS-0056), a PDE2A inhibitor (PF-05180999), a PDE9A inhibitor (PF-4447943), and a PDE10A inhibitor (MP10), each at a single dose of 10 or 30 mg/kg, or concomitantly with all 4 inhibitors at 10 mg/kg each. Male Carworth Farms (Crl:CF1 ® [CF-1]) mice were dosed intraperitoneally (ip) with the four individual inhibitors at a single dose of 10 mg/kg or concomitantly with all 4 inhibitors at 10 mg/kg each. The doses studied are generally adequate for affecting measurable cNT levels in the tissues of interest and were thereby chosen for this investigation. Measured 3',5'-cyclic adenosine monophosphate (cAMP) changes were generally statistically insignificant in the brain, striatum and CSF after administration of the aforementioned PDE inhibitors. However, the levels of 3',5'-cyclic guanosine monophosphate (cGMP) increased in both rat and mouse striatum (2.2-, 2.1- and 1.7-fold and 6.4-, 2.8- and 1.7-fold, respectively) after PDE2A, 9A, and 10A inhibitor dosing. In all cases, the cNT changes followed the same trend in the brain, striatum and CSF after PDE inhibitor dosing and dose response was observed in rats. Concomitant treatment with PDE1B, PDE2A, PDE9A and PDE10A inhibitors resulted in a 4.4- and 36.7-fold increase of cGMP in rat and mouse striatum. The drug exposures after concomitant treatment were also higher than in the individual inhibitor-treated animals. cGMP enhancement observed could be due to synergistic effects, though an additive effect of the combined inhibitor concentrations may also contribute., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Autotaxin-lysophosphatidic acid (ATX-LPA) axis is closely associated with several inflammation-related diseases. In the colonic mucosa of patients with chronic ulcerative colitis (UC), the expression of ATX and the percentage of Th17 cells are found to increase. However, it is unclear whether ATX-LPA axis affects the differentiation of Th17 cells in chronic UC. To investigate whether ATX-LPA axis contributes to Th17 cell differentiation, a mouse model of chronic UC was established by drinking water with DSS at intervals. ATX inhibitor was used as an intervention. The disease active index (DAI), colonic weight to length ratio, colon length, colon histopathology, and MAdCAM-1 were observed. Additionally, the expression of ATX, LPA receptor, CD34, IL-17A, IL-21, IL-6, ROR-γt, STAT3 in colonic tissue, and the percentage of Th17 cells in spleens and mesenteric lymph nodes (MLNs) were measured using different methods. ATX blockade was able to relieve symptoms and inflammatory response of DSS-induced chronic colitis. The DAI and colonic weight to length ratio were apparently decreased, while the colon length was increased. The pathological damage and colitis severity were lighter in the inhibitor group than that in the DSS group. Inhibiting ATX reduced the expression of ATX, LPA receptor, and CD34 and also decreased the percentages of Th17 cells in spleens and MLNs and the expressions of IL-17A and IL-21, as well as the factors in Th17 cell signaling pathway including IL-6, ROR-γt, and STAT3 in colonic tissue. ATX-LPA axis blockade could alleviate inflammation by suppressing Th17 cell differentiation in chronic UC.

Background and Objectives: GLPG1690 is an autotaxin inhibitor in development for the treatment of idiopathic pulmonary fibrosis. Several publications suggested a role of autotaxin in the control of disease-affected lung function and of lysophosphatidic acid in lung remodeling processes. The aim of the current article was to describe the exposure-response relationship of GLPG1690 and further develop a rational basis to support dose selection for clinical trials in patients with idiopathic pulmonary fibrosis., Methods: Two trials were conducted in healthy volunteers: in the first trial, GLPG1690 was administered as single doses from 20 mg up to 1500 mg, and subsequently in multiple daily doses of 300-1000 mg. In a second trial, the interaction of rifampin with 600 mg of GLPG1690 was evaluated. A third trial was conducted in patients with idiopathic pulmonary fibrosis administered 600 mg of GLPG1690 once daily for 12 weeks. The exposure-response (lysophosphatidic acid C18:2 reduction) relationship of GLPG1690 was first described using non-linear mixed-effects modeling and the model was subsequently deployed to simulate a lysophosphatidic acid C18:2 reduction as a biomarker of autotaxin inhibition in the dose range from 50 to 1000 mg once or twice daily., Results: The population pharmacokinetics and lysophosphatidic acid C18:2 response of GLPG1690 were adequately described by a combined population pharmacokinetic and pharmacokinetic/pharmacodynamic model. Dose, formulation, rifampin co-administration, health status (healthy volunteer vs. patient with idiopathic pulmonary fibrosis), and baseline lysophosphatidic acid C18:2 were identified as covariates in the model. The effect of dose on systemic clearance indicated that GLPG1690 followed a more than dose-proportional increase in exposure over the simulated dose range of 50-1000 mg once daily. Model-based simulations showed reductions in lysophosphatidic acid C18:2 of at least 80% with doses greater or equal to 200 mg once daily., Conclusion: Based on these results, 200 and 600 mg once-daily doses were selected for future clinical trials in patients with idiopathic pulmonary fibrosis.

Autotaxin (ATX) is a potential drug target that is associated with inflammatory diseases and various cancers. In our previous studies, we have designed several inhibitors targeting ATX using computational and experimental approaches. Here, we have analyzed topological water networks (TWNs) in the binding pocket of ATX. TWN analysis revealed a pharmacophoric site inside the pocket. We designed and synthesized compounds considering the identified pharmacophoric site. Furthermore, we performed biological experiments to determine their ATX inhibitory activities. High potency of the designed compounds supports the predictions of the TWN analysis.

Serotonin (5-hydroxy-tryptamine, 5-HT) exerted concentration-dependent positive inotropic effects or positive chronotropic effects in transgenic (TG) mice which overexpress the human 5-HT 4a receptor in the heart but not in littermate wild-type (WT) mice. These positive inotropic effects and positive chronotropic effects are thought to be mediated by cyclic adenosine 3',5'-monophosphate (cAMP) in TG cardiomyocytes. To determine whether these effects are antagonized by endogenous phosphodiesterases (PDEs), the inotropic and chronotropic effects of 5-HT were tested in the additional presence of the PDE inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride (EHNA) (1 μM, a PDE2 inhibitor) or cilostamide (1 μM, a PDE3 inhibitor), rolipram (0.1 μM and 1 μM, a PDE4 inhibitor), and their combinations. For comparison, 3-isobutyl-1-methylxanthine (IBMX), an unspecific PDE inhibitor, was investigated. The use of 10 μM IBMX, the combination of rolipram (1 μM) and EHNA (1 μM), and the combination of rolipram (0.1 μM) and cilostamide (1 μM) each increased the potency of 5-HT to elevate the force of contraction in TG mice, but not the potency of 5-HT to increase the beating rate in TG mice. This indicates that PDE4 and PDE2 regulate the inotropic but not the chronotropic effects of 5-HT in TG mice. In contrast, cilostamide (1 μM) alone, EHNA (1 μM) alone, or in combination decreased the potency of 5-HT to increase force of contraction in TG mice. In summary, our present data suggest that the positive chronotropic effect of 5-HT in TG mice does not involve PDE activities, whereas the positive inotropic effect of 5-HT and the basal force in TG mice are diminished by endogenous activity of PDE4. Phosphorylation of PDE4, when PDE2 or PDE3 is inhibited, might enhance the activity of PDE4.

Introduction: Severe, inadequately-controlled asthma remains a clinical challenge. For this reason, clinical trials and preclinical experimental studies on novel agents as an add-on therapies continue emerge. Phosphodiesterases (PDEs) are enzymes that regulate the function of immune cells by hydrolyzing cyclic guanosine monophosphate/cGMP and cyclic adenosine monophosphate/cAMP. PDEs are divided into subfamilies [PDE3, PDE4, PDE5 and PDE7] which are mainly found in the respiratory tract. Inhibitors of PDEs have already been approved for COPD and pulmonary hypertension., Areas Covered: The role of PDE inhibitors in asthma treatment and the possible mechanism of action via their anti-inflammatory and/or bronchodilating effect are discussed., Expert Opinion: Novel PDE inhibitors exhibiting fewer adverse events may have a role as add-on therapies in asthma treatment in the future. More clinical trials are necessary to prove their efficacy and evaluate their safety profile before approval by regulatory bodies is granted.

Elevated intraocular pressure (IOP) is the major cause of glaucoma, which is the second leading cause of blindness. However, current glaucoma treatments cannot completely regulate IOP and progression of glaucoma. Our group recently found that autotaxin (ATX) activity in human aqueous humor (AH) was positively correlated with increased IOP in various subtypes of glaucoma. To develop new IOP-lowering treatments, we generated a novel ATX inhibitor as an ophthalmic drug by high-throughput screening, followed by inhibitor optimization. Administration of the optimized ATX inhibitor (Aiprenon) reduced IOP in laser-treated mice exhibiting elevated IOP and higher level of ATX activity in AH and normal mice in vivo. The stimulation of ATX induced outflow resistance in the trabecular pathway; however, administration of Aiprenon recovered the outflow resistance in vitro. The in vitro experiments implied that the IOP-lowering effect of Aiprenon could be correlated with the altered cellular behavior of trabecular meshwork (TM) and Schlemm's canal endothelial (SC) cells. Overall, our findings showed that ATX had major impact in regulating IOP as a target molecule, and potent ATX inhibitors such as Aiprenon could be a promising therapeutic approach for lowering IOP.

Usnic acid, a lichen secondary metabolite produced by a whole number of lichens, has attracted the interest of researchers owing to its broad range of biological activity, including antiviral, antibiotic, anticancer properties, and it possessing a certain toxicity. The synthesis of new usnic acid derivatives and the investigation of their biological activity may lead to the discovery of compounds with better pharmacological and toxicity profiles. In this context, a series of new usnic acid derivatives comprising a terpenoid moiety were synthesized, and their ability to inhibit the catalytic activity of the human DNA repair enzyme tyrosyl-DNA phosphodiesterase 1 was investigated. The most potent compounds (15A, 15B, 15G: , and 16A, 16B, 16G: ) had IC 50 values in the range of 0.33 - 2.7 µM. The inhibitory properties were mainly dependent on the flexibility and length of the terpenoid moiety, but not strongly dependent on the configuration of the asymmetric centers. The synthesized derivatives showed low cytotoxicity against human cell lines in an MTT assay. They could be used as a basis for the development of more effective anticancer therapies when combined with topoisomerase 1 inhibitors., Competing Interests: The authors declare no conflict of interest., (Georg Thieme Verlag KG Stuttgart · New York.)

Background and Objective: The DNA repair enzyme tyrosyl-DNA-phosphodiesterase 1 (TDP1) is a current inhibition target to improve the efficacy of cancer chemotherapy. Previous studies showed that compounds combining adamantane and monoterpenoid fragments are active against TDP1 enzyme. This investigation is focused on the synthesis of monoterpenoid derived esters of 1-adamantane carboxylic acid as TDP1 inhibitors., Methods: New esters were synthesized by the interaction between 1-adamantane carboxylic acid chloride and monoterpenoid alcohols. The esters were tested against TDP1 and its binding to the enzyme was modeling., Results: 13 Novel ester-based TDP1 inhibitors were synthesized with yields of 21-94%; of these, nine esters had not been previously described. A number of the esters were found to inhibit TDP1, with IC50 values ranging from 0.86-4.08 µM. Molecular modelling against the TDP1 crystal structure showed a good fit of the active esters in the catalytic pocket, explaining their potency. A non-toxic dose of ester, containing a 3,7- dimethyloctanol fragment, was found to enhance the cytotoxic effect of topotecan, a clinically used anti-cancer drug, against the human lung adenocarcinoma cell line A549., Conclusion: The esters synthesized were found to be active against TDP1 in the lower micromolar concentration range, with these findings being corroborated by molecular modeling. Simultaneous action of the ester synthesized from 3,7-dimethyloctanol-1 and topotecan revealed a synergistic effect., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Toluene diisocyanate (TDI) is a reactive chemical used in manufacturing plastics. TDI exposure adversely affects workers' health, causing occupational asthma, but individuals differ in susceptibility. We recently suggested a role for signalling mediated by the enzyme autotaxin (ATX) and its product, lysophosphatidic acid (LPA), in TDI toxicity. Here we genotyped 118 TDI-exposed workers for six single-nucleotide polymorphisms (SNPs) in genes encoding proteins implicated in ATX-LPA signalling: purinergic receptor P2X7 (P2RX7), CC motif chemokine ligand 2 (CCL2), interleukin 1β (IL1B), and caveolin 1 (CAV1). Two P2RX7 SNPs (rs208294 and rs2230911) significantly modified the associations between a biomarker of TDI exposure (urinary 2,4-toluene diamine) and plasma LPA; two IL1B SNPs (rs16944 and rs1143634) did not. CAV1 rs3807989 modified the associations, but the effect was not statistically significant (p = 0.05-0.09). In vitro, TDI-exposed bronchial epithelial cells (16HBE14o-) rapidly released ATX and IL-1β. P2X7 inhibitors attenuated both responses, but confocal microscopy showed non-overlapping localizations of ATX and IL-1β, and down-regulation of CAV1 inhibited the ATX response but not the IL-1β response. This study indicates that P2X7 is pivotal for TDI-induced ATX-LPA signalling, which was modified by genetic variation in P2RX7. Furthermore, our data suggest that the TDI-induced ATX and IL-1β responses occur independently., (Copyright © 2018 Elsevier Inc. All rights reserved.)

TAK-063 is currently being developed to treat schizophrenia. In this study, we investigated the absorption, distribution, metabolism and excretion (ADME) properties of TAK-063 using several paradigms. Following oral administration of TAK-063 at 0.3 mg/kg, bioavailability of TAK-063 was 27.4% in rats and 49.5% in dogs with elimination half-lives of 3.1 hr in rats and 3.7 hr in dogs. TAK-063 is a highly permeable compound without P-glycoprotein (P-gp) or breast cancer resistance protein substrate liability and can be readily absorbed into systemic circulation via the intestine. TAK-063 can also cross the blood-brain barrier. TAK-063 was metabolized mainly by CYP2C8 and CYP3A4/5, while incubation with human liver microsomes produced the major human metabolite, M-I as well as several unknown minor metabolites. Metabolism of TAK-063 to M-I occurs through hydroxylation of the mono-substituted pyrazole moiety. In vitro, TAK-063 was observed to inhibit CYP2C8, CYP2C19 and P-gp with IC 50 values of 8.4, 12 and 7.13 μM, respectively. TAK-063 was primarily excreted in the faeces in rats and dogs with M-I as a predominant component. The pre-clinical data from these ADME studies demonstrate a favourable pharmacokinetic profile for TAK-063 with good brain distribution supporting the feasibility of targeting central nervous system regions involved in schizophrenia pathophysiology. TAK-063 has recently been investigated in a phase 2 clinical trial (NCT02477020)., (© 2018 The Authors. Basic & Clinical Pharmacology & Toxicology published by John Wiley & Sons Ltd on behalf of Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).)

Autotaxin is a dual-function ecto-enzyme, encoded by the gene ENPP2, which is the primary source of the bioactive signaling lipid, lysophosphatidic acid. Aberrations in autotaxin/lysophosphatidic acid signaling have been associated with a number of neurological, psychiatric, neoplastic, and neurodevelopmental conditions, such as pain, pruritus, glioblastoma multiforme, multiple sclerosis, Alzheimer's disease, hydrocephalus, and schizophrenia. This Viewpoint offers a brief overview of the likely indications for therapeutic targeting of autotaxin, in disorders affecting the nervous system.

Hormones regulate hepatic gene expressions to maintain metabolic homeostasis. Ectonucleotide pyrophosphatase/phosphodiesterase 1 has been thought to interfere with insulin signaling. To determine its potential role in the regulation of metabolism, we analyzed its gene (Enpp1) expression in the liver of rats experiencing fasting and refeeding cycles, and in primary rat hepatocytes and human hepatoma HepG2 cells treated with insulin and dexamethasone using northern blot and real-time PCR techniques. Hepatic Enpp1 expression was induced by fasting and reduced by refeeding in the rat liver. In primary rat hepatocytes and HepG2 hepatoma cells, insulin reduced Enpp1 mRNA abundance, whereas dexamethasone induced it. Dexamethasone disrupted the insulin-reduced Enpp1 expression in primary hepatocytes. This is in contrast to the responses of the expression of the cytosolic form of phosphoenolpyruvate carboxykinase gene to the same hormones, where insulin reduced it significantly in the process. In addition, the dexamethasone-induced Enpp1 gene expression was attenuated in the presence of 8-Br-cAMP. In conclusion, we demonstrated for the first time that hepatic Enpp1 is regulated in the cycle of fasting and refeeding, a process that might be attributed to insulin-reduced Enpp1 expression. This insulin-reduced Enpp1 expression might play a role in the development of complications in diabetic patients.

The essential biological function of phosphodiesterase (PDE) type enzymes is to regulate the cytoplasmic levels of intracellular second messengers, 3',5'-cyclic guanosine monophosphate (cGMP) and/or 3',5'-cyclic adenosine monophosphate (cAMP). PDE targets have 11 isoenzymes. Of these enzymes, PDE5 has attracted a special attention over the years after its recognition as being the target enzyme in treating erectile dysfunction. Due to the amino acid sequence and the secondary structural similarity of PDE6 and PDE11 with the catalytic domain of PDE5, first-generation PDE5 inhibitors (i.e. sildenafil and vardenafil) are also competitive inhibitors of PDE6 and PDE11. Since the major challenge of designing novel PDE5 inhibitors is to decrease their cross-reactivity with PDE6 and PDE11, in this study, we attempt to identify potent tadalafil-like PDE5 inhibitors that have PDE5/PDE6 and PDE5/PDE11 selectivity. For this aim, the similarity-based virtual screening protocol is applied for the "clean drug-like subset of ZINC database" that contains more than 20 million small compounds. Moreover, molecular dynamics (MD) simulations of selected hits complexed with PDE5 and off-targets were performed in order to get insights for structural and dynamical behaviors of the selected molecules as selective PDE5 inhibitors. Since tadalafil blocks hERG1 K channels in concentration dependent manner, the cardiotoxicity prediction of the hit molecules was also tested. Results of this study can be useful for designing of novel, safe and selective PDE5 inhibitors.

Introduction: Autotaxin (ATX) is a secreted enzyme that hydrolyzes lysophosphatidylcholine to lysophosphatidic acid (LPA) and choline. The ATX/LPA axis has received increasing interest in recent years because both the enzyme ATX and the bioactive lipid LPA are involved in various pathological conditions such as tumor progression and metastasis, fibrotic diseases, autoimmune diseases, arthritis, chronic hepatitis, obesity and impaired glucose homeostasis. Thus, a great effort has been devotd in developing synthetic ATX inhibitors as new agents to treat various diseases including cancer and fibrotic diseases. Areas covered: This review article summarizes the autotaxin inhibitors presented in patent literature from October 2012 to August 2016 and their biological evaluation, discussing their activities in vitro and in vivo. Expert opinion: During the recent years, there has been an intensive effort on the discovery of potent and selective ATX inhibitors. Although various synthetic inhibitors have been developed, only limited studies for their in vivo activity have been reported so far. A decade after the first claim of synthetic ATX inhibitors in 2006, one inhibitor has been in clinical trials for idiopapthic pulmonary fibrosis. The use of ATX inhibitors seems an attractive strategy to produce novel medicinal agents, for example anticancer agents.

Objective: Autotaxin is a secreted lysophospholipase that mediates the conversion of lysophosphatidyl choline (LPC) to lysophosphatidic acid (LPA), a bioactive lipid mediator. Autotaxin levels in plasma and synovial fluid correlate with disease severity in patients with knee osteoarthritis (OA). The goal of this study was to develop and characterize a novel small molecule inhibitor of autotaxin to inhibit LPA production in vivo and determine its efficacy in animal models of musculoskeletal pain., Design: Compound libraries were screened using an LPC coupled enzyme assay that measures the amount of choline released from LPC by the action of autotaxin. Hits from this assay were tested in a plasma assay to assess inhibition of endogenous plasma autotaxin and subsequently tested for their ability to lower plasma LPA levels upon oral dosing of rats. The best compounds were then tested in animal models of musculoskeletal pain., Results: Compound screening led to the identification of compounds with nanomolar potency for inhibition of autotaxin activity. Studies in rats demonstrated a good correlation between compound exposure levels and a decrease in LPA levels in plasma. The leading molecule (compound-1) resulted in a dose dependent decrease in joint pain in the mono-sodium iodoacetate (MIA) and meniscal tear models and a decrease in bone fracture pain in the osteotomy model in rats., Conclusion: We have identified and characterized a novel small molecule inhibitor of autotaxin and demonstrated its efficacy in animal models of musculoskeletal pain. The inhibitor has the potential to serve as an analgesic for human OA and bone fracture., (Copyright © 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Autotaxin is a circulating enzyme with a major role in the production of lysophosphatic acid (LPA) species in blood. A role for the autotaxin/LPA axis has been suggested in many disease areas including pulmonary fibrosis. Structural modifications of the known autotaxin inhibitor lead compound 1, to attenuate hERG inhibition, remove CYP3A4 time-dependent inhibition, and improve pharmacokinetic properties, led to the identification of clinical candidate GLPG1690 (11). Compound 11 was able to cause a sustained reduction of LPA levels in plasma in vivo and was shown to be efficacious in a bleomycin-induced pulmonary fibrosis model in mice and in reducing extracellular matrix deposition in the lung while also reducing LPA 18:2 content in bronchoalveolar lavage fluid. Compound 11 is currently being evaluated in an exploratory phase 2a study in idiopathic pulmonary fibrosis patients.

Pseudoxanthoma elasticum is a prototype of heritable ectopic mineralization disorders, with phenotypic overlap with generalized arterial calcification of infancy and arterial calcification due to CD73 deficiency. Recent observations have suggested that the reduced inorganic pyrophosphate/phosphate ratio is the cause of soft connective tissue mineralization in these disorders. PXE International, a patient advocacy organization, supports research in part by sponsoring biennial research symposia on these disorders; the latest meeting was held in September 2016 at Thomas Jefferson University, Philadelphia. This report summarizes the progress in pseudoxanthoma elasticum and other ectopic mineralization disorders, as presented in the symposium, with focus on translational aspects of precision medicine toward improved diagnostics and treatment development for these currently intractable disorders., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Autotaxin (ATX) is a secreted lysophospholipase D that catalyzes the production of lysophosphatidic acid (LPA), a pleiotropic growth-factor-like lysophospholipid. Increased ATX expression has been detected in various chronic inflammatory disorders and different types of cancer; however, little is known about its role and mode of action in liver fibrosis and cancer. Here, increased ATX expression was detected in chronic liver disease (CLD) patients of different etiologies, associated with shorter overall survival. In mice, different hepatotoxic stimuli linked with the development of different forms of CLDs were shown to stimulate hepatocyte ATX expression, leading to increased LPA levels, activation of hepatic stellate cells (HSCs), and amplification of profibrotic signals. Hepatocyte-specific, conditional genetic deletion and/or transgenic overexpression of ATX established a liver profibrotic role for ATX/LPA, whereas pharmacological ATX inhibition studies suggested ATX as a possible therapeutic target in CLDs. In addition, hepatocyte ATX ablation and the consequent deregulation of lipid homeostasis was also shown to attenuate hepatocellular carcinoma (HCC) development, thus implicating ATX/LPA in the causative link of cirrhosis and HCC., Conclusion: ATX is a novel player in the pathogenesis of liver fibrosis and cancer and a promising therapeutic target. (Hepatology 2017;65:1369-1383)., (© 2016 by the American Association for the Study of Liver Diseases.)

Autotaxin produces the bioactive lipid lysophosphatidic acid (LPA) and is a drug target of considerable interest for numerous pathologies. We report the expedient, structure-guided evolution of weak physiological allosteric inhibitors (bile salts) into potent competitive Autotaxin inhibitors that do not interact with the catalytic site. Functional data confirms that our lead compound attenuates LPA mediated signaling in cells and reduces LPA synthesis in vivo, providing a promising natural product derived scaffold for drug discovery.

In the search for potential psychotropic agents, a new series of 3,7-dimethyl- and 1,3-dimethyl-8-alkoxypurine-2,6-dione derivatives of arylpiperazines, perhydroisoquinolines, or tetrahydroisoquinolines with flexible alkylene spacers (5-16 and 21-32) were synthesized and evaluated for 5-HT 1A /5-HT 7 receptor affinities as well as PDE4B1 and PDE10A inhibitory properties. The 1-(4-(4-(2-hydroxyphenyl)piperazin-1-yl)butyl)-3,7-dimethyl-8-propoxypurine-2,6-dione (16) and 7-(2-hydroxyphenyl)piperazinylalkyl-1,3-dimethyl-8-ethoxypurine-2,6-diones (31 and 32) as potent dual 5-HT 1A /5-HT 7 receptor ligands with antagonistic activity produced an antidepressant-like effect in the forced swim test in mice. This effect was similar to that produced by citalopram. All the tested compounds were stronger phosphodiesterase isoenzyme inhibitors than theophylline and theobromine. The most potent compounds, 15 and 16, were characterized by 51 and 52% inhibition, respectively, of PDE4B1 activity at a concentration of 10 -5  M. Concerning the above findings, it may be assumed that the inhibition of PDE4B1 may impact on the signal strength and specificity resulting from antagonism toward the 5-HT 1 and 5-HT 7 receptors, especially in the case of compounds 15 and 16. This dual receptor and enzyme binding mode was analyzed and explained via molecular modeling studies., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objective: We previously implicated the lipid mediator lysophosphatidic acid (LPA) as having a role in dermal fibrosis in systemic sclerosis (SSc). The aim of this study was to identify the role of the LPA-producing enzyme autotaxin (ATX), and to connect the ATX/LPA and interleukin-6 (IL-6) pathways in SSc., Methods: We evaluated the effect of a novel ATX inhibitor, PAT-048, on fibrosis and IL-6 expression in the mouse model of bleomycin-induced dermal fibrosis. We used dermal fibroblasts from SSc patients and control subjects to evaluate LPA-induced expression of IL-6, and IL-6-induced expression of ATX. We next evaluated whether LPA-induced ATX expression is dependent on IL-6, and whether baseline IL-6 expression in fibroblasts from SSc patients is dependent on ATX. Finally, we compared ATX and IL-6 expression in the skin of patients with SSc and healthy control subjects., Results: PAT-048 markedly attenuated bleomycin-induced dermal fibrosis when treatment was initiated before or after the development of fibrosis. LPA stimulated expression of IL-6 in human dermal fibroblasts, and IL-6 stimulated fibroblast expression of ATX, connecting the ATX/LPA and IL-6 pathways in an amplification loop. IL-6 knockdown abrogated LPA-induced ATX expression in fibroblasts, and ATX inhibition attenuated IL-6 expression in fibroblasts and the skin of bleomycin-challenged mice. Expression of both ATX and IL-6 was increased in SSc skin, and LPA-induced IL-6 levels and IL-6-induced ATX levels were increased in fibroblasts from SSc patients compared with controls., Conclusion: ATX is required for the development and maintenance of dermal fibrosis in a mouse model of bleomycin-induced SSc and enables 2 major mediators of SSc fibrogenesis, LPA and IL-6, to amplify the production of each other. Our results suggest that concurrent inhibition of these 2 pathways may be an effective therapeutic strategy for dermal fibrosis in SSc., Competing Interests: Drs. Bain and Goulet receive income from and own equity in PharmAkea Inc. Dr. Tager is a member of the scientific advisory board of PharmAkea Inc., (© 2016, American College of Rheumatology.)

Tyrosyl-DNA phosphodiesterase 1 (TDP1) is a repair enzyme for stalled DNA-topoisomerase 1 (Top1) cleavage complexes and other 3'-end DNA lesions. TDP1 is a perspective target for anticancer therapy based on Top1-poison-mediated DNA damage. Several novel usnic acid derivatives with an enamine moiety have been synthesized and tested as inhibitors of TDP1. The enamines of usnic acid showed IC 50 values in the range of 0.16 to 2.0 μM. These compounds revealed moderate cytotoxicity against human tumor MCF-7 cells. These new compounds enhanced the cytotoxicity of the established Top1 poison camptothecin by an order of magnitude.

Phosphodiesterase 10A (PDE10A) is selectively expressed in the striatal regions in the brain and may play a role in modulating dopaminergic and glutamatergic second messenger pathways. PDE10A inhibitors are expected to be useful in treating neuropsychiatric disorders such as schizophrenia and Huntington's disease. In this study, the brain kinetics of [(11)C]T-773 in the human brain and test-retest reproducibility of the outcome measures were evaluated. Subsequently, the occupancy of a novel PDE10A inhibitor, TAK-063, was measured using [(11)C]T-773. Dynamic PET measurements were conducted three times for 12 healthy male subjects after intravenous bolus injection of [(11)C]T-773: two baseline PETs and one postdose PET (3hours) after oral administration of TAK-063 for four subjects, and one baseline PET and two postdose PET (3hours and 23hours) for eight subjects. Kinetic model analysis was performed with arterial input functions. PDE10A occupancy was calculated as the percent change of the binding specific to PDE10A (Vs) total distribution volume (VT), which was calculated as the VT of the putamen minus the VT of the cerebellum. Regional brain uptake was highest in the putamen. Time-activity curves of the brain regions were described with two tissue-compartment (2TC) models. The mean VT was 5.5±0.7 in the putamen and 2.3±0.5 in the cerebellum in the baseline PET. Absolute VT variability between the two baseline scans was less than 7%. Reproducibility of VT was excellent. PDE10A occupancy in the putamen ranged from 2.8% to 72.1% at 3hours after a single administration of 3 to 1000mg of TAK-063, and increased in a dose- and plasma concentration-dependent manner. At 23hours postdose, PDE10A occupancy in the putamen was 0 to 42.8% following administration of 3 to 100mg of TAK-063. In conclusion, [(11)C]T-773 showed good characteristics as a PET radioligand for PDE10A in the human brain., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Inhibitors of phosphodiesterase 10A (PDE10A) represent a novel class of potential antipsychotic compounds. These principles increase the level of cAMP and cGMP in the medium spiny neurons of the striatum and resemble the neurochemical consequences of dopamine D2 receptor inhibition and dopamine D1 receptor stimulation. Cognitive dysfunctions, including an impaired ability to shift perceptual attentional set, are core features of schizophrenia. In the present study, we investigated the involvement of D1 receptors in the procognitive action of the PDE10A inhibitor using the attentional set-shifting task in rats. The performance of the rats in the extradimensional shift stage of the attentional set-shifting task was taken as an index of cognitive flexibility. We first assessed the effects of the D1 agonist in otherwise untreated animals and in animals pretreated with the D1 receptor antagonist. We then investigated the procognitive effects of the PDE10A inhibitor, MP-10, in otherwise untreated animals and in animals pretreated with the D1 receptor antagonist. The dopamine D1 receptor antagonist SCH-23390 produced cognitive impairment at the dose of 0.0125 mg/kg, but not at 0.0063 mg/kg. The D1 receptor agonist, SKF-81,297, produced a procognitive effect that was abolished by 0.0063 mg/kg of SCH-23390. The compound MP-10 produced a procognitive effect at the dose of 0.3 mg/kg, but not at 0.1 mg/kg. Rat pretreatment with 0.0063 mg/kg of SCH-23390 did not block the procognitive effect of 0.3 mg/kg of MP-10. The present study demonstrates that the blockade of dopamine D1 receptors is unlikely to affect the procognitive effects of PDE10A inhibition.

We report the design and synthesis of novel 5,6-diarylated pyridin-2(1H)-one derivatives as pharmacophoric PDE10A inhibitors. This highly potent molecular scaffold was developed from an inactive diarylpyridine-2-amine derivative 3b by extensive and systematic analogue synthesis and SAR analysis. Further optimization of the scaffold resulted in identification of pyridin-2(1H)-one 18b as a lead compound with good potency (IC50 = 1.6 nM) and selectivity (>6000-fold) over other related PDEs but with a poor pharmacokinetic profile. Careful metabolite profiling of 18b revealed that poor systemic exposure in rats (Cmax = 44 ng/mL; AUC0-t = 359 ng · h/mL) at 10 mg/kg was due to the formation of O-glucuronide conjugate by phase 2 metabolism. The structure of the glucuronide metabolite was confirmed by retention time and LC-MS/MS fragmentation matching with the synthetic glucuronide 26. The problem of low exposure of 18b was effectively addressed by its conversion to an acetate prodrug 25b, which upon oral dosing resulted in an improved pharmacokinetic profile (Cmax = 359 ng.h/mL; AUC0-t = 2436 ng.h/mL) and a desirable brain to plasma ratio of 1.2. The prodrug 25b showed good efficacy in selected rodent models of psychosis.

In this study, we report the pharmacological effects of a novel PDE10A inhibitor, SEP-39. SEP-39 is a potent (1.0nM) inhibitor of human PDE10A in vitro, with good selectivity (>16000-fold) against other PDEs. In an in vivo occupancy study, the RO50 value was determined to be 0.7mg/kg (p.o.), corresponding to plasma and brain exposures of 28ng/mL and 43ng/g, respectively. Using microdialysis, we show that 3mg/kg (p.o.) SEP-39 significantly increased rat striatal cGMP concentrations. Furthermore, SEP-39 inhibits PCP-induced hyperlocomotion at doses of 1 and 3mg/kg (p.o.) corresponding to 59-86% occupancy. At similar doses in a catalepsy study, the time on the bar was increased but the maximal effect was less than that seen with haloperidol. In an EEG study, 3 and 10mg/kg (p.o.) SEP-39 suppressed REM intensity and increased the latency to REM sleep. We also demonstrate the procognitive effects of SEP-39 in the rat novel object recognition assay. These effects appear to require less PDE10A inhibition than the reversal of PCP-induced hyperlocomotion or EEG effects, as improvements in recognition index were seen at doses of 0.3mg/kg and above. Our data demonstrate that SEP-39 is a potent, orally active PDE10A inhibitor with therapeutic potential in a number of psychiatric indications., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Mass-directed isolation of the CH2Cl2/MeOH extract from the bark of an Australian plant, Macropteranthes leichhardtii, resulted in the purification of a new phenylpropanoid glucoside, macropteranthol (1), together with four known analogues (2-5). The structure of compound 1 was elucidated by NMR and MS data analyses and quantum chemical calculations. Compounds 3 and 5 showed inhibitory activity against tyrosyl-DNA phosphodiesterase I with IC50 values of ∼1.0 μM.

Objective: The treatment of lupus nephritis is still an unmet medical need requiring new therapeutic approaches. Our group found recently that irinotecan, an inhibitor of topoisomerase I (topo I), reversed proteinuria and prolonged survival in mice with advanced lupus nephritis. While irinotecan is known to stabilize the complex of topo I and DNA, the enzyme tyrosyl-DNA phosphodiesterase 1 (TDP-1) functions in an opposing manner by releasing topo I from DNA. Therefore, we undertook this study to test whether the TDP-1 inhibitor furamidine has an additional effect on lupus nephritis when used in combination with irinotecan., Methods: NZB/NZW mice were treated with low-dose irinotecan and furamidine either alone or in combination beginning at age 26 weeks. DNA relaxation was visualized using gel electrophoresis. Binding of anti-double-stranded DNA (anti-dsDNA) antibodies to DNA modified by topo I, TDP-1, and the topo I inhibitor camptothecin was determined by enzyme-linked immunosorbent assay., Results: Compared to treatment with either agent alone, simultaneous treatment with low-dose irinotecan and furamidine significantly improved survival of NZB/NZW mice. Similar to what has been previously shown for irinotecan alone, the combination treatment did not change the levels of anti-dsDNA antibodies. In vitro, recombinant TDP-1 increased topo I-mediated DNA relaxation, resulting in enhanced binding of anti-dsDNA antibodies. In combination with topo I and camptothecin, TDP-1 reversed the inhibitory effects of camptothecin on DNA relaxation and anti-dsDNA binding., Conclusion: Affecting DNA relaxation by the enzymes topo I and TDP-1 and their inhibitors may be a promising approach for the development of new targeted therapies for systemic lupus erythematosus., (© 2015, American College of Rheumatology.)

Fifteen cinnoline analogues and six benzimidazole phosphodiesterase 10A (PDE10A) inhibitors were synthesized as potential PET radiopharmaceuticals and their in vitro activity as PDE10A inhibitors was determined. Nine out of twenty-one compounds were potent inhibitors of PDE10A with IC50 values ranging from 1.5 to 18.6nM. Notably, the IC50 values of compounds 26a, 26b, and 33c were 1.52±0.18, 2.86±0.10, and 3.73±0.60nM, respectively; these three compounds also showed high in vitro selectivity (>1000-fold) for PDE10A over PDE 3A/3B, PDE4A/4B. The high potency and selectivity of these three compounds suggests that they could be radiolabeled with PET radionuclides for further evaluation of their in vivo pharmacological behavior and ability to quantify PDE10A in the brain., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: Despite the application of proven adult heart failure therapies to children with idiopathic dilated cardiomyopathy (IDC), prognosis remains poor. Clinical experience with phosphodiesterase 3 inhibitors (PDE3i) in pediatric patients with IDC, however, demonstrates improved heart failure symptoms without the increased incidence of sudden death seen in adults treated with PDE3i. We sought to determine age-related differences in PDE activity and associated intracellular signaling responsible for the efficacy and relative safety of chronic PDE3i in pediatric heart failure., Methods and Results: cAMP levels, PDE activity, and phospholamban phosphorylation (pPLB) were determined in explanted human left ventricular myocardium (pediatric n=41; adult n=88). Adults and children with IDC (not treated with PDE3i) had lower cAMP and pPLB compared with nonfailing controls. In contrast to their adult counterparts, pediatric IDC patients chronically treated with PDE3i had elevated cAMP (P=0.0403) and pPLB (P=0.0119). In addition, total PDE- and PDE3-specific activities were not altered in pediatric IDC patients on PDE3i, whereas adult IDC patients on PDE3i demonstrated higher total PDE-specific (74.6±13.8 pmol/mg per minute) and PDE3-specific (48.2±15.9 pmol/mg per minute) activities in comparison with those of nonfailing controls (59.5±14.4 and 35.5±12.8 pmol/mg per minute, respectively)., Conclusions: Elevated cAMP and higher pPLB may contribute to sustained hemodynamic benefits in pediatric IDC patients treated with PDE3i. In contrast, higher total PDE and PDE3 activities in adult IDC patients treated with PDE3i may perpetuate lower myocardial cAMP and pPLB levels, limiting the potential benefits of PDE3i therapy., (© 2014 American Heart Association, Inc.)

(±)-Torreyunlignans A-D (1a/1b-4a/4b), four pairs of new 8-9' linked neolignan enantiomers featuring a rare (E)-2-styryl-1,3-dioxane moiety, were isolated from the trunk of Torreya yunnanensis. The structures were determined by combined spectroscopic and chemical methods, and the absolute configurations were elucidated by ECD calculations. The compounds were screened by using tritium-labeled adenosine 3',5'-cyclic monophosphate ([(3)H]-cGMP) as a substrate for inhibitory affinities against phosphodiesterase-9A (PDE9A), which is a potential target for the treatment of diabetes and Alzheimer's disease. All of the enantiomers exhibited inhibition against PDE9A with IC50 values ranging from 5.6 to 15.0 μM. This is the first report of PDE9A inhibitors from nature.

Nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) belongs to the family of ecto-nucleotidases, which control extracellular nucleotide, nucleoside, and (di)phosphate levels. To study the (patho)physiological roles of NPP1 potent and selective inhibitors with drug-like properties are required. Therefore, a compound library was screened for NPP1 inhibitors using a colorimetric assay with p-nitrophenyl 5'-thymidine monophosphate (p-Nph-5'-TMP) as an artificial substrate. This led to the discovery of 2-(3H-imidazo[4,5-b]pyridin-2-ylthio)-N-(3,4-dimethoxyphenyl)acetamide (5a) as a hit compound with a Ki value of 217 nM. Subsequent structure-activity relationship studies led to the development of purine and imidazo[4,5-b]pyridine analogues with high inhibitory potency (Ki values of 5.00 nM and 29.6 nM, respectively) when assayed with p-Nph-5'-TMP as a substrate. Surprisingly, the compounds were significantly less potent when tested versus ATP as a substrate, with Ki values in the low micromolar range. A prototypic inhibitor was investigated for its mechanism of inhibition and found to be competitive versus both substrates.

TDP1 and TDP2 were discovered and named based on the fact they process 3'- and 5'-DNA ends by excising irreversible protein tyrosyl-DNA complexes involving topoisomerases I and II, respectively. Yet, both enzymes have an extended spectrum of activities. TDP1 not only excises trapped topoisomerases I (Top1 in the nucleus and Top1mt in mitochondria), but also repairs oxidative damage-induced 3'-phosphoglycolates and alkylation damage-induced DNA breaks, and excises chain terminating anticancer and antiviral nucleosides in the nucleus and mitochondria. The repair function of TDP2 is devoted to the excision of topoisomerase II- and potentially topoisomerases III-DNA adducts. TDP2 is also essential for the life cycle of picornaviruses (important human and bovine pathogens) as it unlinks VPg proteins from the 5'-end of the viral RNA genome. Moreover, TDP2 has been involved in signal transduction (under the former names of TTRAP or EAPII). The DNA repair partners of TDP1 include PARP1, XRCC1, ligase III and PNKP from the base excision repair (BER) pathway. By contrast, TDP2 repair functions are coordinated with Ku and ligase IV in the non-homologous end joining pathway (NHEJ). This article summarizes and compares the biochemistry, functions, and post-translational regulation of TDP1 and TDP2, as well as the relevance of TDP1 and TDP2 as determinants of response to anticancer agents. We discuss the rationale for developing TDP inhibitors for combinations with topoisomerase inhibitors (topotecan, irinotecan, doxorubicin, etoposide, mitoxantrone) and DNA damaging agents (temozolomide, bleomycin, cytarabine, and ionizing radiation), and as novel antiviral agents., (Published by Elsevier B.V.)

Autotaxin is a secreted enzyme that produces most extracellular lysophosphatidate, which stimulates 6 G-protein-coupled receptors. Lysophosphatidate promotes cancer cell survival, growth, migration, invasion, metastasis, and resistance to chemotherapy and radiotherapy. The present work investigated whether inhibiting autotaxin could decrease breast tumor growth and metastasis. We used a new autotaxin inhibitor (ONO-8430506; IC90=100 nM), which decreased plasma autotaxin activity by >60% and concentrations of unsaturated lysophosphatidates by >75% for 24 h compared with vehicle-treated mice. The effects of ONO-8430506 on tumor growth were determined in a syngeneic orthotopic mouse model of breast cancer following injection of 20,000 BALB/c mouse 4T1 or 4T1-12B cancer cells. We show for the first time that inhibiting autotaxin decreases initial tumor growth and subsequent lung metastatic nodules both by 60% compared with vehicle-treated mice. Significantly, 4T1 cells express negligible autotaxin compared with the mammary fat pad. Autotaxin activity in the fat pad of nontreated mice was increased 2-fold by tumor growth. Our results emphasize the importance of tumor interaction with its environment and the role of autotaxin in promoting breast cancer growth and metastasis. We also established that autotaxin inhibition could provide a novel therapeutic approach to blocking the adverse effects of lysophosphatidate in cancer., (© FASEB.)

Tyrosyl-DNA phosphodiesterase I (TDP1) repairs stalled topoisomerase I (Top1)-DNA covalent complexes and has been proposed to be a promising and attractive target for cancer treatment. Inhibitors of TDP1 could conceivably act synergistically with Top1 inhibitors and thereby potentiate the effects of Top1 poisons. This study describes the successful design and synthesis of 2-position-modified indenoisoquinolines as dual Top1-TDP1 inhibitors using a structure-based drug design approach. Enzyme inhibition studies indicate that indenoisoquinolines modified at the 2-position with three-carbon side chains ending with amino substituents show both promising Top1 and TDP1 inhibitory activity. Molecular modeling of selected target compounds bound to Top1 and TDP1 was used to rationalize the enzyme inhibition results and structure-activity relationship analysis.

We report the discovery of a series of imidazo[1,2-a]pyrazine derivatives as novel inhibitors of phosphodiesterase 10A (PDE10A). In a high-throughput screening campaign we identified the imidazopyrazine derivative 1, a PDE10A inhibitor with limited selectivity versus the other phosphodiesterases (PDEs). Subsequent investigation of 1 and replacement of the trimethoxyphenyl group by a (methoxyethyl)pyrazole moiety maintained PDE10A inhibition but enhanced selectivity against the other PDEs. Systematic examination and analysis of structure-activity and structure-property relationships resulted in the discovery of 2, an in vitro potent and selective inhibitor of PDE10A with high striatal occupancy of PDE10A, promising in vivo efficacy in different rodent behavioral models of schizophrenia, and a good pharmacokinetic profile in rats.