Ariflo (SB 207499), a second generation phosphodiesterase 4 inhibitor for the treatment of asthma and COPD: from concept to clinic

Phosphodiesterase-4 Inhibition in Parkinson's Disease: Molecular Insights and Therapeutic Potential

Clinicians and researchers are exploring safer and novel treatment strategies for treating the ever-prevalent Parkinson's disease (PD) across the globe. Several therapeutic strategies are used clinically for PD, including dopamine replacement therapy, DA agonists, MAO-B blockers, COMT blockers, and anticholinergics. Surgical interventions such as pallidotomy, particularly deep brain stimulation (DBS), are also employed. However, they only provide temporal and symptomatic relief. Cyclic adenosine monophosphate (cAMP) is one of the secondary messengers involved in dopaminergic neurotransmission. Phosphodiesterase (PDE) regulates cAMP and cGMP intracellular levels. PDE enzymes are subdivided into families and subtypes which are expressed throughout the human body. PDE4 isoenzyme- PDE4B subtype is overexpressed in the substantia nigra of the brain. Various studies have implicated multiple cAMP-mediated signaling cascades in PD, and PDE4 is a common link that can emerge as a neuroprotective and/or disease-modifying target. Furthermore, a mechanistic understanding of the PDE4 subtypes has provided perceptivity into the molecular mechanisms underlying the adverse effects of phosphodiesterase-4 inhibitors (PDE4Is). The repositioning and development of efficacious PDE4Is for PD have gained much attention. This review critically assesses the existing literature on PDE4 and its expression. Specifically, this review provides insights into the interrelated neurological cAMP-mediated signaling cascades involving PDE4s and the potential role of PDE4Is in PD. In addition, we discuss existing challenges and possible strategies for overcoming them.

Phosphodiesterase-4 enzyme as a therapeutic target in neurological disorders

Phosphodiesterases (PDE) are a diverse family of enzymes (11 isoforms so far identified) responsible for the degradation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) which are involved in several cellular and biochemical functions. Phosphodiesterase 4 (PDE4) is the major isoform within this group and is highly expressed in the mammalian brain. An inverse association between PDE4 and cAMP levels is the key mechanism in various pathophysiological conditions like airway inflammatory diseases-chronic obstruction pulmonary disease (COPD), asthma, psoriasis, rheumatoid arthritis, and neurological disorders etc. In 2011, roflumilast, a PDE4 inhibitor (PDE4I) was approved for the treatment of COPD. Subsequently, other PDE4 inhibitors (PDE4Is) like apremilast and crisaborole were approved by the Food and Drug Administration (FDA) for psoriasis, atopic dermatitis etc. Due to the adverse effects like unbearable nausea and vomiting, dose intolerance and diarrhoea, PDE4 inhibitors have very less clinical compliance. Efforts are being made to develop allosteric modulation with high specificity to PDE4 isoforms having better efficacy and lesser adverse effects. Interestingly, repositioning PDE4Is towards neurological disorders including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), multiple sclerosis (MS) and sleep disorders, is gaining attention. This review is an attempt to summarize the data on the effects of PDE4 overexpression in neurological disorders and the use of PDE4Is and newer allosteric modulators as therapeutic options. We have also compiled a list of on-going clinical trials on PDE4 inhibitors in neurological disorders.

Phosphodiesterase-4 inhibitors for chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with cough, sputum production or dyspnoea, and a reduction in lung function, quality of life, and life expectancy. Apart from smoking cessation, no other treatments that slow lung function decline are available. Roflumilast and cilomilast are oral phosphodiesterase-4 (PDE₄) inhibitors proposed to reduce the airway inflammation and bronchoconstriction seen in COPD. This Cochrane Review was first published in 2011, and was updated in 2017 and 2020.

OBJECTIVES

To evaluate the efficacy and safety of oral PDE₄ inhibitors for management of stable COPD.

SEARCH METHODS

We identified randomised controlled trials (RCTs) from the Cochrane Airways Trials Register (date of last search 9 March 2020). We found other trials at web-based clinical trials registers.

SELECTION CRITERIA

We included RCTs if they compared oral PDE₄ inhibitors with placebo in people with COPD. We allowed co-administration of standard COPD therapy.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Two independent review authors selected trials for inclusion, extracted data, and assessed risk of bias. We resolved discrepancies by involving a third review author. We assessed our confidence in the evidence by using GRADE recommendations. Primary outcomes were change in lung function (minimally important difference (MID) = 100 mL) and quality of life (scale 0 to 100; higher score indicates more limitations).

MAIN RESULTS

We found 42 RCTs that met the inclusion criteria and were included in the analyses for roflumilast (28 trials with 18,046 participants) or cilomilast (14 trials with 6457 participants) or tetomilast (1 trial with 84 participants), with a duration between six weeks and one year or longer. These trials included people across international study centres with moderate to very severe COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) grades II to IV), with mean age of 64 years. We judged risks of selection bias, performance bias, and attrition bias as low overall amongst the 39 published and unpublished trials. Lung function Treatment with a PDE₄ inhibitor was associated with a small, clinically insignificant improvement in forced expiratory volume in one second (FEV₁) over a mean of 40 weeks compared with placebo (mean difference (MD) 49.33 mL, 95% confidence interval (CI) 44.17 to 54.49; participants = 20,815; studies = 29; moderate-certainty evidence). Forced vital capacity (FVC) and peak expiratory flow (PEF) were also improved over 40 weeks (FVC: MD 86.98 mL, 95% CI 74.65 to 99.31; participants = 22,108; studies = 17; high-certainty evidence; PEF: MD 6.54 L/min, 95% CI 3.95 to 9.13; participants = 4245; studies = 6; low-certainty evidence). Quality of life Trials reported improvements in quality of life over a mean of 33 weeks (St George's Respiratory Questionnaire (SGRQ) MD -1.06 units, 95% CI -1.68 to -0.43; participants = 7645 ; moderate-certainty evidence). Incidence of exacerbations Treatment with a PDE₄ inhibitor was associated with a reduced likelihood of COPD exacerbation over a mean of 40 weeks (odds ratio (OR) 0.78, 95% CI 0.73 to 0.84; participants = 20,382; studies = 27; high-certainty evidence), that is, for every 100 people treated with PDE₄ inhibitors, five more remained exacerbation-free during the study period compared with those given placebo (number needed to treat for an additional beneficial outcome (NNTB) 20, 95% CI 16 to 27). No change in COPD-related symptoms nor in exercise tolerance was found. Adverse events More participants in the treatment groups experienced an adverse effect compared with control participants over a mean of 39 weeks (OR 1.30, 95% CI 1.22 to 1.38; participants = 21,310; studies = 30; low-certainty evidence). Participants experienced a range of gastrointestinal symptoms such as diarrhoea, nausea, vomiting, or dyspepsia. Diarrhoea was more commonly reported with PDE₄ inhibitor treatment (OR 3.20, 95% CI 2.74 to 3.50; participants = 20,623; studies = 29; high-certainty evidence), that is, for every 100 people treated with PDE₄ inhibitors, seven more suffered from diarrhoea during the study period compared with those given placebo (number needed to treat for an additional harmful outcome (NNTH) 15, 95% CI 13 to 17). The likelihood of psychiatric adverse events was higher with roflumilast 500 µg than with placebo (OR 2.13, 95% CI 1.79 to 2.54; participants = 11,168; studies = 15 (COPD pool data); moderate-certainty evidence). Roflumilast in particular was associated with weight loss during the trial period and with an increase in insomnia and depressive mood symptoms. Participants treated with PDE₄ inhibitors were more likely to withdraw from trial participation; on average, 14% in the treatment groups withdrew compared with 8% in the control groups. Mortality No effect on mortality was found (OR 0.98, 95% CI 0.77 to 1.24; participants = 19,786; studies = 27; moderate-certainty evidence), although mortality was a rare event during these trials.

AUTHORS' CONCLUSIONS

For this current update, five new studies from the 2020 search contributed to existing findings but made little impact on outcomes described in earlier versions of this review. PDE₄ inhibitors offered a small benefit over placebo in improving lung function and reducing the likelihood of exacerbations in people with COPD; however, they had little impact on quality of life or on symptoms. Gastrointestinal adverse effects and weight loss were common, and the likelihood of psychiatric symptoms was higher, with roflumilast 500 µg. The findings of this review provide cautious support for the use of PDE₄ inhibitors in COPD. In accordance with GOLD 2020 guidelines, they may have a place as add-on therapy for a subgroup of people with persistent symptoms or exacerbations despite optimal COPD management (e.g. people whose condition is not controlled by fixed-dose long-acting beta₂-agonist (LABA) and inhaled corticosteroid (ICS) combinations). More longer-term trials are needed to determine whether or not PDE₄ inhibitors modify FEV₁ decline, hospitalisation, or mortality in COPD.

Phosphodiesterase inhibitors say NO to Alzheimer's disease

Phosphodiesterases (PDEs) consisted of 11 subtypes (PDE1 to PDE11) and over 40 isoforms that regulate levels of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP), the second messengers in cell functions. PDE inhibitors (PDEIs) have been attractive therapeutic targets due to their involvement in diverse medical conditions, e.g. cardiovascular diseases, autoimmune diseases, Alzheimer's disease (AD), etc. Among them; AD with a complex pathology is a progressive neurodegenerative disorder which affect mostly senile people in the world and only symptomatic treatment particularly using cholinesterase inhibitors in clinic is available at the moment for AD. Consequently, novel treatment strategies towards AD are still searched extensively. Since PDEs are broadly expressed in the brain, PDEIs are considered to modulate neurodegenerative conditions through regulating cAMP and cGMP in the brain. In this sense, several synthetic or natural molecules inhibiting various PDE subtypes such as rolipram and roflumilast (PDE4 inhibitors), vinpocetine (PDE1 inhibitor), cilostazol and milrinone (PDE3 inhibitors), sildenafil and tadalafil (PDE5 inhibitors), etc have been reported showing encouraging results for the treatment of AD. In this review, PDE superfamily will be scrutinized from the view point of structural features, isoforms, functions and pharmacology particularly attributed to PDEs as target for AD therapy.

Targeting Metalloenzymes for Therapeutic Intervention

Metalloenzymes are central to a wide range of essential biological activities, including nucleic acid modification, protein degradation, and many others. The role of metalloenzymes in these processes also makes them central for the progression of many diseases and, as such, makes metalloenzymes attractive targets for therapeutic intervention. Increasing awareness of the role metalloenzymes play in disease and their importance as a class of targets has amplified interest in the development of new strategies to develop inhibitors and ultimately useful drugs. In this Review, we provide a broad overview of several drug discovery efforts focused on metalloenzymes and attempt to map out the current landscape of high-value metalloenzyme targets.

Incidence of Adverse Effects and Discontinuation Rate between Patients Receiving 250 Micrograms and 500 Micrograms of Roflumilast: A Comparative Study

BACKGROUND

Roflumilast is the only approved oral phosphodiesterase-4 inhibitor for the treatment of severe chronic obstructive pulmonary disease (COPD) in patients with chronic bronchitis and a history of frequent exacerbations. The purpose of this study was to examine the incidence of adverse effects associated with roflumilast treatment in a real-world setting. Further, we compared the incidence of adverse effects and the discontinuation rate among patients receiving different doses.

METHODS

We identified all outpatients diagnosed with COPD at Seoul St. Mary's Hospital between May 2011 and September 2016 and retrospectively reviewed their medical records. Roflumilast was prescribed to patients in doses of 500 μg and 250 μg.

RESULTS

A total of 269 COPD patients were prescribed roflumilast in our hospital during the study period. Among them, 178 patients were treated with 500 μg and 91 patients were treated with 250 μg. The incidence of adverse effects was 38.2% in the 500 μg group and 25.3% in the 250 μg group (p=0.034). The discontinuation rate of roflumilast was 41.6% (n=74) in the 500 μg group and 23.1% (n=21) in the 250 μg group (p=0.003). When adjusted by age, sex, smoking status, and lung function, 500 μg dose was significantly associated with the discontinuation of roflumilast (odds ratio, 2.87; p<0.001).

CONCLUSION

There was a lower incidence of adverse effects and discontinuation among patients treated with 250 μg compared with 500 μg dose. Further studies regarding the optimal dose of roflumilast are required.

Reductive ortho C–H cyanoalkylation of aryl(heteroaryl) sulfoxides: a general approach to α-aryl(heteroaryl) nitriles

A catalyst-free low-temperature cyanoalkylation has been developed as a general protocol for the synthesis of α-aryl(heteroaryl) nitriles.

Phosphodiesterase 4 inhibitors for chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with cough, sputum production or dyspnoea and a reduction in lung function, quality of life and life expectancy. Apart from smoking cessation, there are no other treatments that slow lung function decline. Roflumilast and cilomilast are oral phosphodiesterase 4 (PDE4) inhibitors proposed to reduce the airway inflammation and bronchoconstriction seen in COPD. This is an update of a Cochrane review first published in 2011 and updated in 2013.

OBJECTIVES

To evaluate the efficacy and safety of oral PDE4 inhibitors in the management of stable COPD.

SEARCH METHODS

We identified randomised controlled trials (RCTs) from the Cochrane Airways Trials Register (date of last search October 2016). We found other trials from web-based clinical trials registers.

SELECTION CRITERIA

We included RCTs if they compared oral PDE4 inhibitors with placebo in people with COPD. We allowed co-administration of standard COPD therapy.

DATA COLLECTION AND ANALYSIS

One review author extracted data and a second review author checked the data. We reported pooled data in Review Manager as mean differences (MD), standardised mean differences (SMD) or odds ratios (OR). We converted the odds ratios into absolute treatment effects in a 'Summary of findings' table.

MAIN RESULTS

Thirty-four separate RCTs studying roflumilast (20 trials with 17,627 participants) or cilomilast (14 trials with 6457 participants) met the inclusion criteria, with a duration of between six weeks and one year. These included people across international study centres with moderate to very severe COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) grades II-IV), with a mean age of 64 years.We considered that the methodological quality of the 34 published and unpublished trials was acceptable overall. Treatment with a PDE4 inhibitor was associated with a significant improvement in forced expiratory volume in one second (FEV1) over the trial period compared with placebo (MD 51.53 mL, 95% confidence interval (CI) 43.17 to 59.90, 27 trials with 20,585 participants, moderate-quality evidence due to moderate levels of heterogeneity and risk of reporting bias). There were small improvements in quality of life (St George's Respiratory Questionnaire (SGRQ), MD -1.06 units, 95% CI -1.68 to -0.43, 11 trials with 7645 participants, moderate-quality evidence due to moderate levels of heterogeneity and risk of reporting bias) and COPD-related symptoms, but no significant change in exercise tolerance. Treatment with a PDE4 inhibitor was associated with a reduced likelihood of COPD exacerbation (OR 0.78, 95% CI 0.73 to 0.83; 23 trials with 19,948 participants, high-quality evidence). For every 100 people treated with PDE4 inhibitors, five more remained exacerbation-free during the study period compared with placebo (number needed to treat for an additional beneficial outcome (NNTB) 20, 95% CI 16 to 26). More participants in the treatment groups experienced non-serious adverse events compared with controls, particularly a range of gastrointestinal symptoms such as diarrhoea, nausea, vomiting or dyspepsia. For every 100 people treated with PDE4 inhibitors, seven more suffered from diarrhoea during the study period compared with placebo (number needed to treat for an additional harmful outcome (NNTH) 15, 95% CI 13 to 17). Roflumilast in particular was associated with weight loss during the trial period and an increase in insomnia and depressive mood symptoms. There was no significant effect of treatment on non-fatal serious adverse events (OR 0.99, 95% CI 0.91 to 1.07) or mortality (OR 0.97, 95% CI 0.76 to 1.23), although mortality was a rare event during the trials. Participants treated with PDE4 inhibitors were more likely to withdraw from the trials because of adverse effects; on average 14% in the treatment groups withdrew compared with 8% in the control groups.

AUTHORS' CONCLUSIONS

In people with COPD, PDE4 inhibitors offered benefit over placebo in improving lung function and reducing the likelihood of exacerbations; however, they had little impact on quality of life or symptoms. Gastrointestinal adverse effects and weight loss were common, and safety data submitted to the US Food and Drug Administration (FDA) have raised concerns over psychiatric adverse events with roflumilast. The findings of this review give cautious support to the use of PDE4 inhibitors in COPD. They may be best used as add-on therapy in a subgroup of people with persistent symptoms or exacerbations despite optimal COPD management. This is in accordance with the GOLD 2017 guidelines. Longer-term trials are needed to determine whether or not PDE4 inhibitors modify FEV1 decline, hospitalisation or mortality in COPD.

The potential role of phosphodiesterase inhibitors in the management of asthma

Asthma is a chronic inflammatory condition characterised by reversible airflow obstruction and airway hyperreactivity. The course of the illness may be punctuated by exacerbations resulting in deterioration in quality of life and, in some cases, days lost from school or work. That asthma is common and increasingly prevalent magnifies the importance of any potential economic costs, and promoting asthma control represents an important public health agenda. While lifestyle changes represent a valuable contribution in some patients, the majority of asthmatic patients require therapeutic intervention. The recognition of the role of inflammation in the pathogenesis of asthma has led to an emphasis on regular anti-inflammatory therapy, of which inhaled corticosteroid treatment remains the most superior. In selected patients, further improvements in asthma control may be gained by the addition of regular inhaled long-acting beta(2)-adrenoceptor agonists or oral leukotriene receptor antagonists to inhaled corticosteroid therapy. However, a significant minority of patients with asthma remain poorly controlled despite appropriate treatment, suggesting that additional corticosteroid nonresponsive inflammatory pathways may be operative. Furthermore, some patients with asthma display an accelerated decline in lung function, suggesting that active airway re-modeling is occurring. Such observations have focused attention on the potential to develop new therapies which complement existing treatments by targeting additional inflammatory pathways. The central role of phosphodiesterase (PDE), and in particular the PDE4 enzyme, in the regulation of key inflammatory cells believed to be important in asthma - including eosinophils, lymphocytes, neutrophils and airway smooth muscle - suggests that drugs designed to target this enzyme will have the potential to deliver both bronchodilation and modulate the asthmatic inflammatory response. In vivo studies on individual inflammatory cells suggest that the effects are likely to be favorable in asthma, and animal study models have provided proof of concept; however, first-generation PDE inhibitors have been poorly tolerated due to adverse effects. The development of second-generation agents such as cilomilast and roflumilast heralds a further opportunity to test the potential of these agents, although to date only a limited amount of data from human studies has been published, making it difficult to draw firm conclusions.

Effect of a Dose-Escalation Regimen for Improving Adherence to Roflumilast in Patients with Chronic Obstructive Pulmonary Disease

BACKGROUND

The adverse effects of the phosphodiesterase-4 inhibitor roflumilast, appear to be more frequent in clinical practice than what was observed in chronic obstructive pulmonary disease (COPD) clinical trials. Thus, we designed this study to determine whether adverse effects could be reduced by starting roflumilast at half the dose, and then increasing a few weeks later to 500 µg daily.

METHODS

We retrospectively investigated 85 patients with COPD who had taken either 500 µg roflumilast, or a starting dose of 250 µg and then increased to 500 µg. We analyzed all adverse events and assessed differences between patients who continued taking the drug after dose escalation and those who had stopped.

RESULTS

Adverse events were reported by 22 of the 85 patients (25.9%). The most common adverse event was diarrhea (10.6%). Of the 52 patients who had increased from a starting dose of 250 µg roflumilast to 500 µg, 43 (82.7%) successfully maintained the 500 µg roflumilast dose. No difference in factors likely to affect the risk of adverse effects, was detected between the dose-escalated and the discontinued groups. Of the 26 patients who started with the 500 µg roflumilast regimen, seven (26.9%) discontinued because of adverse effects. There was no statistically significant difference in discontinuation rate between the dose-escalated and the control groups (p=0.22).

CONCLUSION

Escalating the roflumilast dose may reduce treatment-related adverse effects and improve tolerance to the full dose. This study suggests that the dose-escalated regimen reduced the rate of discontinuation. However, longer-term and larger-scale studies are needed to support the full benefit of a dose escalation strategy.

Novel Roflumilast analogs as soft PDE4 inhibitors

PDE4 inhibitors are of high interest for treatment of a wide range of inflammatory or autoimmune diseases. Their potential however has not yet been realized due to target-associated side effects, resulting in a low therapeutic window. We herein report the design, synthesis and evaluation of novel PDE4 inhibitors containing a γ-lactone structure. Such molecules are designed to undergo metabolic inactivation when entering circulation, thereby limiting systemic exposure and reducing the risk for side effects. The resulting inhibitors were highly active on both PDE4B1 and PDE4D2 and underwent rapid degradation in human plasma by paraoxonase 1. In contrast, their metabolites displayed markedly reduced permeability and/or on-target activity.

Phosphodiesterase 4 inhibitor roflumilast improves the bronchodilative effect of sevoflurane in sensitized airways

BACKGROUND

Although phosphodiesterase 4 inhibitors and the volatile anesthetic sevoflurane are known to have independent bronchodilator properties, the combined administration of these two agents may have the potential to exert an additive or synergistic bronchodilator effect. The authors tested this hypothesis and investigated the common site of this combined relaxation effect in a model of airway hyperresponsiveness with ovalbumin-sensitized guinea pigs.

METHODS

Ovalbumin-sensitized animals (n = 138) were randomized into six groups: sensitized, sevoflurane, rolipram1.0, roflumilast1.0, sevoflurane/rolipram1.0, and sevoflurane/roflumilast1.0. Total lung resistance in vivo, airway smooth muscle tension in vitro, and intracellular cyclic adenosine monophosphate levels were measured to evaluate the relaxation effect.

RESULTS

Among the six sensitized groups, total lung resistance was higher in the order of sensitized > sevoflurane > rolipram 1.0 > roflumilast1.0 > sevoflurane/rolipram1.0 > sevoflurane/roflumilast1.0, with an increase in acetylcholine concentration. Compared with the other five groups, the muscle tensions in the sevoflurane/roflumilast1.0 group were significantly lower at carbacholine doses of 10, 10, and 10 M; the cyclic adenosine monophosphate concentrations (means ± SD) in the sevoflurane/rolipram1.0 (1.61 ± 0.34) and sevoflurane/roflumilast1.0 (1.50 ± 0.20) groups were higher than that in the sensitized (0.52 ± 0.15) and sevoflurane (1.12 ± 0.32) groups.

CONCLUSIONS

The combined use of phosphodiesterase 4 inhibitors with the volatile anesthetic sevoflurane had an additive bronchodilator effect in ovalbumin-sensitized guinea pigs. The concurrent increase in cyclic adenosine monophosphate levels in sensitized airway smooth muscle might be a mechanism of this combined relaxation effect.

Phosphodiesterase 4 inhibitors for chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with cough, sputum production or dyspnoea and a reduction in lung function, quality of life and life expectancy. Apart from smoking cessation, there are no other treatments that slow lung function decline. Roflumilast and cilomilast are oral phosphodiesterase 4 (PDE4) inhibitors proposed to reduce the airway inflammation and bronchoconstriction seen in COPD.

OBJECTIVES

To evaluate the efficacy and safety of oral PDE4 inhibitors in the management of stable COPD.

SEARCH METHODS

We identified randomised controlled trials (RCTs) from the Cochrane Airways Group Specialised Register of trials (date of last search June 2013). We found other trials from web-based clinical trial registers.

SELECTION CRITERIA

We included RCTs if they compared oral PDE4 inhibitors with placebo in people with COPD. We allowed co-administration of standard COPD therapy.

DATA COLLECTION AND ANALYSIS

One review author extracted data and a second review author checked the data, before entry into The Cochrane Collaboration software program (RevMan version 5.2). We reported pooled data as mean differences (MD), standardised mean differences (SMD) or odds ratios (OR).

MAIN RESULTS

Twenty-nine separate RCTs studying roflumilast (15 trials, 12,654 patients) or cilomilast (14 trials, 6457 patients) met the inclusion criteria, with a duration between six weeks and one year. These included people across international study centres with moderate to very severe COPD (GOLD grades II-IV), with a mean age of 64 years.Treatment with a PDE4 inhibitor was associated with a significant improvement in forced expiratory volume in one second (FEV1) over the trial period compared with placebo (MD 45.60 mL; 95% confidence interval (CI) 39.45 to 51.75, 22 trials with 15,670 participants, moderate quality evidence due to moderate levels of heterogeneity and risk of reporting bias). There were small improvements in quality of life (St George's Respiratory Questionnaire MD -1.04; 95% CI -1.66 to -0.41, 10 trials with 7618 participants, moderate quality evidence due to moderate levels of heterogeneity and risk of reporting bias) and COPD-related symptoms, but no change in exercise tolerance. Treatment with a PDE4 inhibitor was associated with a reduced likelihood of COPD exacerbation (OR 0.77; 95% CI 0.71 to 0.83, high quality evidence). For every 100 people treated with PDE4 inhibitors, six more remained exacerbation-free during the study period compared with placebo (number needed to treat for an additional beneficial effect (NNTB) 20; 95% CI 16 to 27). More participants in the treatment groups experienced non-serious adverse events compared with controls, particularly gastrointestinal symptoms and headache. Roflumilast in particular was associated with weight loss during the trial period and an increase in insomnia and depressive mood symptoms. Participants treated with PDE4 inhibitors were also more likely to withdraw from the trials because of adverse effects; on average 24% in the treatment groups withdrew compared with 19% in the control groups.

AUTHORS' CONCLUSIONS

In people with COPD, PDE4 inhibitors offered benefit over placebo in improving lung function and reducing the likelihood of exacerbations; however, they had little impact on quality of life or symptoms. Gastrointestinal adverse effects and weight loss were common, and safety data submitted to the US Food and Drug Administration (FDA) have raised concerns over psychiatric adverse events with roflumilast. The optimum place of PDE4 inhibitors in COPD management therefore remains to be defined. Longer-term trials are needed to determine whether or not PDE4 inhibitors modify FEV1 decline, hospitalisation or mortality in COPD.

Lack of Pharmacokinetic Interactions Between Cilomilast and Theophylline or Smoking in Healthy Volunteers

The pharmacokinetic profile of cilomilast (Ariflo), a selective phosphodiesterase 4 (PDE4) inhibitor, was investigated in three separate studies. Two of these studies explored the drug interaction potential of cilomilast with the nonselective PDE inhibitor, theophylline, and a third study compared the pharmacokinetic profile of cilomilast in smokers and nonsmokers. Repeated administration of cilomilast had no effect on the steady-state pharmacokinetics of theophylline in either a pilot dose-ranging or definitive therapeutic study. At therapeutic doses, the point estimate and 90% confidence interval for theophylline AUC(0-12) and C(max) were completely contained within the range (0.8, 1.25). Similarly, repeated administration of theophylline had little clinically relevant effect on the steady-state pharmacokinetics of cilomilast when compared to placebo, as only slight average increases in cilomilast AUC(0-12) and C(max) (6% and 3%, respectively) were observed. In addition, mean cilomilast exposure (AUC(0- infinity )) was found to be similar in both smokers and nonsmokers (8.47 +/- 2.20 microg*h/mL and 7.70 +/- 2.25 microg*h/mL, respectively). Throughout all three studies, cilomilast was well tolerated, and concomitant use of these selective and nonselective inhibitors, although unlikely in the clinic, is hypothetically feasible. Taken together, these studies clearly differentiate cilomilast from theophylline for drug-drug liability issues in a smoker and nonsmoker population, as well as highlight the potential to switch from one drug to another without undue clinical concern.

Therapeutic potential of ASP3258, a selective phosphodiesterase 4 inhibitor, on chronic eosinophilic airway inflammation

We investigated and compared the pharmacological effects of a PDE4 inhibitor ASP3258 (3-[4-(3-chlorophenyl)-1-ethyl-7-methyl-2-oxo-1,2-dihydro-1,8-naphthyridin-3-yl] propanoic acid), with those of roflumilast, the most clinically advanced PDE4 inhibitor known. ASP3258 inhibited human PDE4A, 4B, 4C, and 4D with respective IC(50) values of 0.036, 0.050, 0.45, and 0.035 nmol/l, all approximately 3-6 times more potent than roflumilast. ASP3258 inhibited LPS-induced TNF-α production and PHA-induced IL-5 production in human whole blood cells with respective IC(50) values of 110 and 100 nmol/l, both approximately 10 times less potent than roflumilast. Repeatedly administered ASP3258 and roflumilast both suppressed chronic airway eosinophilia induced by repeated exposure to ovalbumin in Brown Norway rats with respective ED(50) values of 0.092 and 0.17 mg/kg. We also evaluated the toxicological profiles of ASP3258. Although PDE4 inhibitors induce emesis by mimicking the pharmacological action of an α(2)-adrenoceptor antagonist, repeated administration of ASP3258 (3 mg/kg) had no such inhibitory effect on rats anesthetized with α(2) - adrenoceptor agonist. PDE4 inhibitors are also known to induce vascular injury in rats. Although repeatedly administered ASP3258 (3 and 10 mg/kg) significantly increased plasma fibrinogen, a biomarker for toxicity, 1 mg/kg of ASP3258 did not. These results suggest that ASP3258 is an attractive PDE4 inhibitor for treating chronic eosinophilic airway inflammation due to asthma.

Emerging drugs for asthma

INTRODUCTION

Current drug treatments for asthma relieve bronchospasm and airway inflammation but do not offer a cure, and symptoms return when treatment is stopped. Asthma management guidelines emphasize the importance of effective asthma treatment to achieve and maintain asthma control. However, despite widely available and effective treatments, achieving asthma control is still an unmet need for many patients.

AREAS COVERED

Remarkable efforts have been made to identify the characteristic features of difficult-to-control (usually severe) asthma that are different from those described for mild-to-moderate asthma, setting the stage for the development of new and even individualized therapies. The most fascinating options of the new asthma treatments are biologic therapies, in particular monoclonal antibodies. In addition, some novel once-daily combinations of long-acting β(2)-agonist and inhaled corticosteroids are under development.

EXPERT OPINION

Asthma is a complex syndrome made up of a number of disease variants or asthma phenotypes, with different underlying pathophysiology. As different drugs target different pathways, it is necessary to determine the individual profile of pathophysiological abnormalities for each patient. Several cytokines have been implicated in the inflammatory cascades leading to the different asthma phenotypes, and the most relevant ones are discussed. The challenge in treating asthma resides precisely in its heterogeneity.

The effects of cigarette smoke on airway inflammation in asthma and COPD: therapeutic implications

Asthma and COPD are two chronic inflammatory disorders of the airway characterized by airflow limitation. While many similarities exist between these two diseases, they are pathologically distinct due to the involvement of different inflammatory cells; predominantly neutrophils, CD8 lymphocytes in COPD and eosinophils and CD4 lymphocytes in asthma. Cigarette smoking is associated with accelerated decline of lung function, increased mortality, and worsening of symptoms in both asthma and COPD. Furthermore, exposure to cigarette smoke can alter the inflammatory mechanisms in asthma to become similar to that seen in COPD with increasing CD8 cells and neutrophils and may therefore alter the response to therapy. Cigarette smoke exposure has been associated with a poor response to inhaled corticosteroids which are recommended as first line anti-inflammatory medications in asthma and as an add-on therapy in patients with severe COPD with history of exacerbations. While the main proposed mechanism for this altered response is the reduction of the histone deacetylase 2 (HDAC2) enzyme system, other possible mechanisms include the overexpression of GR-β, activation of p38 MAPK pathway and increased production of inflammatory cytokines such as IL-2, 4, 8, TNF-α and NF-Kß. Few clinical trials suggest that leukotriene modifiers may be an alternative to corticosteroids in smokers with asthma but there are currently no drugs which effectively reduce the progression of inflammation in smokers with COPD. However, several HDAC2 enhancers including low dose theophylline and other potential anti-inflammatory therapies including PDE4 inhibitors and p38 MAPK inhibitors are being evaluated.

PDE4: a novel target in the treatment of chronic obstructive pulmonary disease

Phosphodiesterases (PDEs) are important modulators of inflammation and wound healing. In this capacity, specific targeting of PDEs for the treatment of many diseases, including chronic obstructive pulmonary disease (COPD), has been investigated. Currently, treatment of COPD is suboptimal. PDE4 modulates the inflammatory response of the lung, and inhibition of PDE4 may be a novel, COPD-specific approach toward more effective treatment strategies. This review describes the state of PDE4-inhibitor therapy for use in COPD treatment.

Anti-asthmatic effect of ASP3258, a novel phosphodiesterase 4 inhibitor

ASP3258 is a potent and selective PDE4 inhibitor and exerts a wide-range of anti-inflammatory effects with low emetic potential, a major adverse effect of PDE4 inhibitors. Here, we investigated the anti-asthmatic potency of ASP3258 as compared with those of two representative PDE4 inhibitors: roflumilast and cilomilast. Orally administered ASP3258, roflumilast, and cilomilast all inhibited ovalbumin (OVA)-induced eosinophil infiltration into the airway of sensitized Brown Norway rats with ED(50) values of 0.81, 0.46, and 4.4 mg/kg, respectively. Histological examination also revealed a decreasing trend in inflammatory cell infiltration into the lung following ASP3258 administration. In vitro investigation of bronchodilatory activities showed that these compounds (10(-8)-10(-6) M) concentration-dependently inhibited OVA-induced contraction of trachea isolated from sensitized guinea pigs but had no effect on spasmogen-precontracted tracheal tension prepared from non-sensitized guinea pigs up to 10(-6) M. In vivo experiments using sensitized guinea pigs showed that these orally administered compounds inhibited OVA-induced increases in airway resistance with ED(50) values of 2.2, 0.35, and 12 mg/kg, respectively. Further, orally administered ASP3258 (0.1 and 1 mg/kg), roflumilast (0.1 and 1 mg/kg), and cilomilast (10 mg/kg) significantly suppressed airway hyperresponsiveness caused by OVA exposure. ASP3258's potent inhibition of antigen-induced bronchoconstriction and airway hyperresponsiveness, two characteristic symptoms of bronchial asthma, suggests that this compound will be useful in treating asthma.

Phosphodiesterase 4 inhibitors for chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) affects symptoms, lung function, quality of life and life expectancy. Apart from smoking cessation, there are no other treatments that slow lung function decline. Roflumilast and cilomilast are oral phosphodiesterase 4 (PDE(4)) inhibitors proposed to reduce the airway inflammation and bronchoconstriction seen in COPD.

OBJECTIVES

To evaluate the efficacy and safety of PDE(4) inhibitors in the management of people with stable COPD. Outcomes included lung function, quality of life, symptoms, exacerbations and adverse effects.

SEARCH STRATEGY

We identified randomised controlled trials (RCTs) from the Cochrane Airways Group Specialised Register of trials (date of last search 6 August 2010). We found other trials from web-based clinical trial registers.

SELECTION CRITERIA

We included RCTs if they compared oral PDE(4) inhibitors with placebo in people with COPD. We allowed co-administration of standard COPD therapy.

DATA COLLECTION AND ANALYSIS

One review author extracted data and a second review author checked the data, before entry into The Cochrane Collaboration software programme (RevMan version 5.1). We reported pooled data as mean differences (MD), standardised mean differences (SMD), or odds ratios (OR).

MAIN RESULTS

Twenty-three separate RCTs studying roflumilast (nine trials, 9211 patients) or cilomilast (fourteen trials, 6457 patients) met the inclusion criteria. None of the trials exceeded a year in duration.Treatment with a PDE(4) inhibitor was associated with a significant improvement in FEV(1)over the trial period compared with placebo (MD 45.59 mL; 95% confidence interval (CI) 39.15 to 52.03), regardless of COPD severity or concomitant COPD treatment. There were some small improvements in quality of life (St George's Respiratory Questionnaire MD -1.04; 95% CI -1.66 to -0.41) and COPD-related symptoms, but no change in exercise tolerance. Treatment with a PDE(4) inhibitor was associated with a reduced likelihood of COPD exacerbation (OR 0.78; 95% CI 0.72 to 0.85). More participants in the treatment groups experienced non-serious adverse events compared with controls, particularly gastrointestinal symptoms and headache. Roflumilast was associated with weight loss during the trial period.

AUTHORS' CONCLUSIONS

In people with COPD, PDE(4) inhibitors offered benefit over placebo in improving lung function and reducing likelihood of exacerbations, however, they had little impact on quality of life or symptoms. Gastrointestinal adverse effects and weight loss were common. The optimum place of PDE(4) inhibitors in COPD management remains to be defined. Longer-term trials are needed to determine whether or not PDE(4) inhibitors modify FEV(1) decline, healthcare utilisation or mortality in COPD.

ASP3258, an orally active potent phosphodiesterase 4 inhibitor with low emetic activity

We investigated the pharmacology of a novel phosphodiesterase (PDE) 4 inhibitor, ASP3258 (3-[4-(3-chlorophenyl)-1-ethyl-7-methyl-2-oxo-1,2-dihydro-1,8-naphthyridin-3-yl] propanoic acid), comparing its potency with that of the most advanced PDE4 inhibitors, roflumilast and cilomilast. PDE4 inhibition by ASP3258 (IC(50)=0.28nM) was as potent as that achieved with roflumilast. ASP3258 inhibited lipopolysaccharide-induced tumor necrosis factor (TNF)-α production in rat whole blood cells (IC(50)=8.8 nM) and rat alveolar macrophages (IC(50)=2.6 nM). Orally administered ASP3258, roflumilast, and cilomilast dose-dependently inhibited production of interleukin-4, TNF-α, and cysteinyl leukotrienes, as well as leukocyte infiltration in bronchoalveolar lavage fluid from the airways of ovalbumin-sensitized Brown Norway rats, and these compounds showed almost complete inhibition at doses of 3, 3, and 30 mg/kg, respectively. PDE4 inhibitors induce emesis by mimicking the pharmacological action of α(2)-adrenoceptor antagonist. However, orally administered roflumilast (3mg/kg) and cilomilast (10mg/kg), but not ASP3258 (3mg/kg), inhibited α(2)-adrenoceptor agonist-induced anesthesia in rats and induced emesis in ferrets. Although ASP3258 (3mg/kg) inhibited airway inflammation completely, it had no emetic activity. As such, this compound may be useful in treating airway inflammatory diseases such as asthma and COPD.

GSK256066, an exceptionally high-affinity and selective inhibitor of phosphodiesterase 4 suitable for administration by inhalation: in vitro, kinetic, and in vivo characterization

Oral phosphodiesterase (PDE) 4 inhibitors such as roflumilast have established the potential of PDE4 inhibition for the treatment of respiratory diseases. However, PDE4 inhibitor efficacy is limited by mechanism-related side effects such as emesis and nausea. Delivering the inhibitor by the inhaled route may improve therapeutic index, and we describe 6-({3-[(dimethylamino)carbonyl]phenyl}sulfonyl)-8-methyl-4-{[3-methyloxy) phenyl]amino}-3-quinolinecarboxamide (GSK256066), an exceptionally high-affinity inhibitor of PDE4 designed for inhaled administration. GSK256066 is a slow and tight binding inhibitor of PDE4B (apparent IC(50) 3.2 pM; steady-state IC(50) <0.5 pM), which is more potent than any previously documented compound, for example, roflumilast (IC(50) 390 pM), tofimilast (IC(50) 1.6 nM), and cilomilast (IC(50) 74 nM). Consistent with this, GSK256066 inhibited tumor necrosis factor α production by lipopolysaccharide (LPS)-stimulated human peripheral blood monocytes with 0.01 nM IC(50) (compared with IC(50) values of 5, 22, and 389 nM for roflumilast, tofimilast, and cilomilast, respectively) and by LPS-stimulated whole blood with 126 pM IC(50). GSK256066 was highly selective for PDE4 (>380,000-fold versus PDE1, PDE2, PDE3, PDE5, and PDE6 and >2500-fold against PDE7), inhibited PDE4 isoforms A-D with equal affinity, and had a substantial high-affinity rolipram binding site ratio (>17). When administered intratracheally to rats, GSK256066 inhibited LPS-induced pulmonary neutrophilia with ED(50) values of 1.1 μg/kg (aqueous suspension) and 2.9 μg/kg (dry powder formulation) and was more potent than an aqueous suspension of the corticosteroid fluticasone propionate (ED(50) 9.3 μg/kg). Thus, GSK256066 has been demonstrated to have exceptional potency in vitro and in vivo and is being clinically investigated as a treatment for chronic obstructive pulmonary disease.

Roflumilast: first phosphodiesterase 4 inhibitor approved for treatment of COPD

In April 2010, the European Medicines Agency Committee for Medicinal Products for Human Use recommended approval of roflumilast, a selective phosphodiesterase 4 inhibitor, for the “maintenance treatment of severe chronic obstructive pulmonary disease (COPD, FEV₁ postbronchodilator less than 50% predicted) associated with chronic bronchitis in adult patients with a history of frequent exacerbations as add-on to bronchodilator treatment”. This decision was based, in part, on the results of several large, international, multicenter, randomized, placebo-controlled trials of either six or 12 months’ duration that had been undertaken in COPD patients. Roflumilast 500 μg daily improved lung function and reduced exacerbations in patients with more severe COPD, especially those with chronic bronchitis, frequent exacerbations, or who required frequent rescue inhaler therapy in the placebo-controlled trials. It also improved lung function and reduced exacerbations in patients with moderately severe COPD treated with salmeterol or tiotropium. Advantages of roflumilast over inhaler therapy are that it is an oral tablet and only needs to be taken once daily. While taking roflumilast, the most common adverse effects patients experienced were gastrointestinal upset and headache. Weight loss, averaging 2.2 kg, occurred in patients treated with roflumilast. Patients taking roflumilast were more likely to drop out of the trials than patients in the control groups. Patients who discontinued therapy usually did so during the first few weeks and were more likely to have experienced gastrointestinal side effects. Roflumilast is the first selective phosphodiesterase 4 inhibitor and will offer physicians another treatment option for patients with more severe COPD.

Effects of asthma treatment: the present and future

The increasing burden of asthma in both primary and secondary care has led to extensive research into its genetics, pathophysiology and treatment over the past few decades. Inhaled corticosteroids remain an integral component in all but the mildest disease, although despite a low-to-moderate dose, many individuals remain symptomatic. In patients with persistent symptoms despite inhaled corticosteroids, a variety of different nonsteroidal second-line therapies are available as add-on therapy. In this review, existing and potential future pharmacological strategies involved in the management of asthma will be highlighted.

Aspirin attenuates the anti-inflammatory effects of theophylline via inhibition of cAMP production in mice with non-eosinophilic asthma

Theophylline is commonly used to treat severe asthma and chronic obstructive pulmonary disease (COPD) characterized by non-eosinophilic inflammation. Acetyl salicylic acid (ASA) is one of the most widely used medications worldwide, but up to 20% of patients with asthma experience aggravated respiratory symptoms after taking ASA. Here we evaluated the adverse effect of ASA on the therapeutic effect of theophylline in mice with non-eosinophilic asthma. A non-eosinophilic asthma mouse model was induced by airway sensitization with lipopolysaccharide-containing allergen and then challenged with allergen alone. Therapeutic intervention was performed during allergen challenge. Theophylline inhibited lung inflammation partly induced by Th1 immune response. ASA attenuated the beneficial effects of theophylline. However, co-administration of the ASA metabolite salicylic acid (SA) showed no attenuating effect on theophylline treatment. The therapeutic effect of theophylline was associated with increase in cAMP levels, which was blocked by co-treatment of theophylline and ASA. ASA co-treatment also attenuated the anti-inflammatory effects of a specific phosphodiesterase 4 inhibitor. These results demonstrate that ASA reverses anti-inflammatory effects of theophylline, and that ASA exerts its adverse effects through the inhibition of cAMP production. Our data suggest that ASA reverses lung inflammation in patients taking theophylline, although clinical evidence will be needed.

Solving the confusion of gnaphaliin structure: gnaphaliin A and gnaphaliin B identified as active principles of Gnaphalium liebmannii with tracheal smooth muscle relaxant properties

Inflorescences of Gnaphalium liebmannii, commonly known as "Gordolobo", is the most important remedy in Mexican traditional medicine to treat respiratory diseases, including asthma. By a bioguided fractionation of the n-hexane extract of this plant, following the relaxant effect on guinea pig tracheal smooth muscle, the flavones 5,7-dihydroxy-3,8-dimethoxyflavone (1) and 3,5-dihydroxy-7,8-dimethoxyflavone (2) were identified as the active relaxant compounds. Compounds 1 and 2 showed more potent relaxant properties than aminophylline in this model. Both 1 and 2 have been described as gnaphaliin in the past; here EIMS data, NMR experiments for both compounds, and X-ray diffraction analysis for 1 provided structural information to suggest that 1 and 2 should be named gnaphaliins A and B, respectively.

The efficacy and safety of cilomilast in COPD

The aim of this review is to present the clinical data on the efficacy and safety of cilomilast in patients with chronic obstructive pulmonary disease (COPD). Over 6000 COPD patients received cilomilast during an extensive clinical development programme performed by GlaxoSmithKline (GSK).Five phase III randomized, double-blind, placebo-controlled, parallel-group pivotal studies were conducted in poorly reversible patients (<15% or <200 mL improvement over baseline in forced expiratory volume in 1 second (FEV(1)) after salbutamol). Patients were randomized to receive oral cilomilast 15 mg (n = 2088) or placebo (n = 1408) twice daily for 24 weeks. The co-primary efficacy variables were changes from baseline in trough (predose) FEV(1) and in total score of the St George's Respiratory Questionnaire (SGRQ).Additional studies were performed to investigate the anti-inflammatory actions of cilomilast by measuring inflammatory cells and mediators in biopsies and induced sputum; to assess the long-term effects of cilomilast; to assess the cardiac safety of cilomilast; and to assess the efficacy of cilomilast on hyperinflation. Results from one of the phase III and from one supportive study have been previously published.In the phase III pivotal studies, when averaged over 24 weeks, the mean change from baseline in FEV(1) in the cilomilast group showed improvement compared with placebo in all studies (range 24-44 mL treatment difference). When averaged over 24 weeks, there was a similar improvement in the mean total SGRQ score in both treatment groups with a decrease ranging from -1.8 to -4.2 units in the cilomilast group and 0.4 to -4.9 units in the placebo group. Only one study, however, showed both a statistically and clinically meaningful difference between the two treatment groups (treatment difference -4.1 units; p < 0.001). Although cilomilast was shown to reduce COPD exacerbations in some of these studies, there was no effect on the incidence of COPD exacerbations in a study specifically powered to detect a difference compared with placebo.No significant change was found in the primary endpoints of the anti-inflammatory studies, although some anti-inflammatory activity was detected, including a reduction in tissue CD8+ T lymphocytes and CD68+ macrophages in airway biopsies. In addition, studies did not demonstrate a consistent significant effect of cilomilast on hyperinflation.In all studies, adverse events associated with the gastrointestinal body system were reported more frequently in the cilomilast group than the placebo group and predominantly occurred within the first 2 weeks of initiating cilomilast therapy.During the cilomilast development programme a number of different endpoints were investigated to characterize the efficacy and safety of this second-generation phosphodiesterase 4 inhibitor. Safety assessments throughout the late-phase programme did not reveal any evidence of serious safety concerns with the use of cilomilast. Previous studies in phase II and early phase III had shown improvements in efficacy endpoints and some evidence of an anti-inflammatory mechanism of action. However, subsequent phase III studies failed to definitively confirm the earlier programme results, which led to termination of the development of cilomilast.

Phosphodiesterase 4 inhibitors in chronic obstructive pulmonary disease: a new approach to oral treatment

Chronic obstructive pulmonary disease represents a major global health care burden for both primary and secondary care providers and is the most common respiratory condition necessitating hospital admission. Short-acting bronchodilators play a vital role in immediate relief of symptoms, while inhaled long-acting bronchodilators and inhaled corticosteroids are advocated for regular use in individuals with persistent symptoms and exacerbations. Theophylline is a nonspecific phosphodiesterase inhibitor and is usually reserved for patients with ongoing symptoms despite optimum inhaled bronchodilator treatment or when difficulty is encountered with inhaler devices. However, it is often not widely used mainly due to frequency of dose-related adverse effects, numerous drug interactions and narrow therapeutic index. This in turn has lead to the development of more selective phosphodiesterase inhibitors in an attempt to create a drug which patients can use with beneficial effects but without the problems associated with theophylline. Current data do indicate that phosphodiesterase 4 inhibitors confer some benefits in chronic obstructive pulmonary disease when compared to placebo in terms of lung function, quality of life and exacerbations. They are also generally well tolerated. Further studies are required to determine fully their long-term beneficial and adverse effect profiles and ultimately where they might comfortably sit in management algorithms.

Human PDE4A8, a novel brain-expressed PDE4 cAMP-specific phosphodiesterase that has undergone rapid evolutionary change

We have isolated cDNAs encoding PDE4A8 (phosphodiesterase 4 isoform A8), a new human cAMP-specific PDE4 isoform encoded by the PDE4A gene. PDE4A8 has a novel N-terminal region of 85 amino acids that differs from those of the related 'long' PDE4A4, PDE4A10 and PDE4A11 isoforms. The human PDE4A8 N-terminal region has diverged substantially from the corresponding isoforms in the rat and other mammals, consistent with rapid evolutionary change in this region of the protein. When expressed in COS-7 cells, PDE4A8 localized predominantly in the cytosol, but approx. 20% of the enzyme was associated with membrane fractions. Cytosolic PDE4A8 was exquisitely sensitive to inhibition by the prototypical PDE4 inhibitor rolipram (IC(50) of 11+/-1 nM compared with 1600 nM for PDE4A4), but was less sensitive to inhibition by cilomilast (IC(50) of 101+/-7 nM compared with 61 nM for PDE4A4). PDE4A8 mRNA was found to be expressed predominantly in skeletal muscle and brain, a pattern that differs from the tissue expression of other human PDE4 isoforms and also from that of rat PDE4A8. Immunohistochemical analysis showed that PDE4A8 could be detected in discrete regions of human brain, including the cerebellum, spinal cord and cerebral cortex. The unique tissue distribution of PDE4A8, combined with the evolutionary divergence of its N-terminus, suggest that this isoform may have a specific function in regulating cAMP levels in human skeletal muscle and brain.

Type 4 phosphodiesterase inhibitor suppresses experimental bladder inflammation

OBJECTIVE

To evaluate the effects of orally administered YM976, a specific inhibitor of type 4 phosphodiesterase (PDE4), on bladder activity in a rat model with hydrochloric acid (HCl)-induced cystitis (IC), hypothesizing that a PDE4 inhibitor might suppress bladder overactivity and bladder pain responses in bladder-hypersensitive disorders such as IC.

MATERIALS AND METHODS

Wistar rats with HCl-induced IC were treated with YM976 or vehicle and their voiding observed and assessed by cystometry. The severity of bladder inflammation (BI) was quantified using the BI index (BII), which comprises three factors (oedema, leukocyte infiltration and haemorrhage). Nociceptive neural activity was also examined using an immunohistochemical study of spinal c-fos expression.

RESULTS

YM976 significantly reduced the number of voids, and the volume per void was significantly higher than in control (vehicle) group. Cystometry showed a significant increase in bladder capacity, voided volume and voiding efficiency, and a decrease in the amplitude of voiding pressure in rats treated with YM976. All BII scores were significantly lower in the YM976 than in the control group. c-fos expression in the spine was less in the YM976 than in the control group.

CONCLUSIONS

Oral administration of YM976 significantly improved the voiding behaviour and histological damage in rats with IC induced by HCl. These results indicate that PDE4 inhibitor might be effective in relieving bladder symptoms with IC.

ABCD of the phosphodiesterase family: interaction and differential activity in COPD

Phosphodiesterases (PDEs) are important enzymes that hydrolyze the cyclic nucleotides adenosine 3'5'-cyclic monophosphate (cAMP) and guanosine 3'5'-cyclic monophosphate (cGMP) to their inactive 5' monophosphates. They are highly conserved across species and as well as their role in signal termination, they also have a vital role in intra-cellular localization of cyclic nucleotide signaling and integration of the cyclic nucleotide pathways with other signaling pathways. Because of their pivotal role in intracellular signaling, they are now of considerable interest as therapeutic targets in a wide variety diseases, including COPD where PDE inhibitors may have bronchodilator, anti-inflammatory and pulmonary vasodilator actions. This review examines the diversity and cellular localization of the isoforms of PDE, the known and speculative relevance of this to the treatment of COPD, and the range of PDE inhibitors in development together with a discussion of their possible role in treating COPD.

An update and appraisal of the cilomilast Phase III clinical development programme for chronic obstructive pulmonary disease

Cilomilast (Ariflo, SB 207499) is an orally active, second-generation phosphodiesterase (PDE) 4 inhibitor that is being developed by GlaxoSmithkline for the treatment of chronic obstructive pulmonary disease (COPD). The results of Phase I and Phase II studies have demonstrated that cilomilast significantly improves lung function and quality of life to a clinically meaningful extent, which has led to a comprehensive Phase III programme of research evaluating efficacy, safety and mechanism of action. However, the results of those Phase III studies are unremarkable and disappointing, raising doubt over the future of cilomilast as a novel therapy for COPD. This review summarizes data obtained from the Phase III clinical development programme, highlights some of the potential concerns both specific to cilomilast and to PDE4 inhibitors in general and assesses the likelihood that cilomilast will reach the market.

Novel molecular therapy

Anti-inflammatory treatment, mainly with inhaled corticosteroids, is the cornerstone of asthma therapy. There are a number of new more specific therapies based on a molecular approach. Despite some promising results from some novel molecular therapies there are also some studies which have shown no effect of these treatments.

Cilomilast: orally active selective phosphodiesterase-4 inhibitor for treatment of chronic obstructive pulmonary disease

OBJECTIVE

To review available literature evaluating the pharmacology, pharmacokinetics, clinical efficacy, and adverse effects of cilomilast, a selective phosphodiesterase-4 (PDE4) inhibitor.

DATA SOURCES

Literature was accessed through MEDLINE (1966-May 2006), Current Contents Clinical Medicine (1998-May 2006), and The Cochrane Library Database (1st quarter 2006) using the terms cilomilast, Ariflo, and SB 207 499. Reference lists from retrieved articles and information from the manufacturer were manually reviewed.

STUDY SELECTION AND DATA EXTRACTION

All clinical trials evaluating cilomilast and published in English were included in this review. In addition, articles evaluating the pharmacology, pharmacokinetics, and safety of cilomilast in humans were reviewed.

DATA SYNTHESIS

Cilomilast is a second-generation PDE4 inhibitor with antiinflammatory effects that target bronchoconstriction, mucus hypersecretion, and airway remodeling associated with chronic obstructive pulmonary disease (COPD). Selective PDE4 inhibition is proposed to maximize the antiinflammatory effects of PDE inhibition while minimizing the adverse effects of nonselective agents. To date, 4 clinical trials have evaluated the efficacy of cilomilast and demonstrated improvement in lung function (forced expiratory volume in 1 second) and quality of life and reduction in the occurrence of COPD exacerbations compared with placebo. Cilomilast is generally well tolerated, with adverse effects being overall mild and self-limiting.

CONCLUSIONS

COPD is a progressive disease, and available treatment options provide limited efficacy. Given its unique mechanism of action and improved adverse effect profile compared with previous agents, cilomilast may have a promising role for the management of COPD.

Peripheral phosphodiesterase 4 inhibition produced by 4-[2-(3,4-Bis-difluoromethoxyphenyl)-2-[4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)-phenyl]-ethyl]-3-methylpyridine-1-oxide (L-826,141) prevents experimental autoimmune encephalomyelitis

Administration of phosphodiesterase 4 (PDE4) inhibitors suppresses the pathogenesis associated with experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). In the present study, we compared the effects of rolipram and 4-[2-(3,4-bis-difluoromethoxyphenyl)-2-[4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)-phenyl]-ethyl]-3-methylpyridine-1-oxide (L-826,141), a novel nonbrain penetrant PDE4 inhibitor, on the onset and severity of clinical signs in a chronic, nonrelapsing/remitting model of EAE. Both rolipram (10 mg/kg p.o.) and L-826,141 (3 mg/kg p.o.) reduced the severity of EAE relative to controls, whereas L-826,141 (3 mg/kg p.o.) also delayed disease onset. To assess whether L-826,141 prevented EAE progression after the first signs of clinical onset, rolipram (10 mg/kg p.o.) or L-826,141 (3 or 30 mg/kg p.o.) were administered 24 h after the first signs of EAE were observed. Only L-826,141 at a dose of 30 mg/kg p.o. significantly decreased the clinical severity of EAE compared with vehicle controls. Immunohistochemical detection of the neuronal activity marker Fos confirmed that L-826,141 did not reach concentrations in the central nervous system sufficient to activate central neurons. Lipopolysaccharide-induced tumor necrosis factor-alpha in whole blood and plasma concentrations of L-826,141 revealed that only the 30-mg/kg dose resulted in levels sufficient to produce a near complete inhibition of PDE4 activity in immune cells. Taken together, these results demonstrate that peripheral PDE4 inhibition, produced by L-826,141, prevents the progression of EAE after the first onset of clinical signs, and suggest that similar compounds may have clinical efficacy in the treatment of MS.

Preferential inhibition of human phosphodiesterase 4 by ibudilast

Ibudilast ophthalmic solution exhibited an improved clinical efficacy over cromoglycate in the treatment of allergic conjunctivitis. To further characterize its principal mode of action, the phosphodiesterase (PDE) inhibitory profile of ibudilast has been examined using human recombinant enzymes. Ibudilast, but not the other commonly used anti-allergic ophthalmic solutions including cromoglycate, ketotifen, tranilast and levocabastine, potently inhibits purified human PDE4A, 4B, 4C and 4D with IC50 values at 54, 65, 239 and 166 nM, respectively. Ibudilast effectively blocks lipopolysaccharide (LPS)-induced tumor necrosis factor (TNFalpha, IC50 = 6.2 microM) and N-formyl-Met-Leu-Phe (fMLP)-induced leukotriene (LT) B4 biosynthesis (IC50 = 2.5 microM) in human whole blood, which are 3 and 6-fold more potent than cilomilast, respectively. The attenuated inflammatory and allergic responses from the potent and preferential PDE4 inhibition of ibudilast may have contributed significantly to its beneficial pharmacological responses and distinguishes ibudilast from the other ophthalmic solutions in the treatment of ocular allergy.

Mesenteritis precedes vasculitis in the rat mesentery after subacute administration of a phosphodiesterase type 4 inhibitor

Inhibitors of phosphodiesterase type 4 (PDE4) are currently exploited as potent drugs for pulmonary diseases. Some PDE4 inhibitors induce necrotizing panarteritis in the mesentery of rats, comparable to spontaneous polyarteritis nodosa in rats and vascular alterations that are induced by various vasoactive compounds, such as fenoldopam and inhibitors of PDE3. The mechanism of toxicity is unknown. In order to investigate the development of arteritis in the splanchnic vasculature of rats, a time-course study was performed with high doses of a compound (BYK169171), specifically inhibiting PDE4. Rats were treated orally for 1-28 days, and alterations in the mesentery were evaluated by histology, morphometry, and immunohistology. As early as 3 days after the onset of treatment, a mesenteritis was found, characterized by macrophage infiltration, fibroblast proliferation, neovascularization, and loss of adipocytes. Incidence and severity of the mesenteritis were low during the first 2 weeks of treatment, but increased with duration of treatment, finally affecting 2/3 of all animals. A segmental necrotizing panarteritis was detected in some rats treated for 21 or 28 days, but always followed a mesenteritis, whereas many animals with mesenteric inflammation did not have vascular lesions. We postulate that PDE4 inhibitors do not cause a primary vasculitis/arteritis in rats, but induce a non-purulent inflammation as the predominant initial toxic effect in the mesentery. This renders their toxic effect distinct from that of PDE3 inhibitors.

Effects of cilomilast, a selective phosphodiesterase 4 inhibitor, on esophageal motility and ph, and orocecal and colonic transit: Two single-center, randomized, double-blind, placebo-controlled, two-part crossover studies in healthy volunteers

BACKGROUND

Phase IIb studies have reported that cilomilast, a selective phosphodiesterase 4 inhibitor being developed for the treatment of chronic obstructive pulmonary disease, is associated with gastrointestinal (GI) adverse effects (AEs) in a small proportion (approximately 5%) of individuals.

OBJECTIVES

The aims of these 2 studies were to investigate the effects of cilomilast 15 mg BID on: (1) lower esophageal sphincter pressure (LESP) and esophageal body motility and pH (study 1); and (2) orocecal and whole-gut transit times (OCTT and WGTT, respectively) (study 2) in healthy volunteers.

METHODS

These 2 randomized, double-blind, placebo-controlled, 2-part crossover studies were conducted at the Neurogastroenterology Unit, Wythenshawe Hospital, Manchester, United Kingdom (study 1) and GlaxoSmithKline, Harlow, United Kingdom (study 2). In study 1, subjects were randomly assigned to receive either cilomilast (15 mg BID) or matched placebo (control) for 7 days (13 doses; subjects were not given the evening dose on day 7), and in study 2, cilomilast (15 mg BID) or matched placebo (control) for 9 days (18 doses) in each of 2 treatment periods. After study drug administration, combined esophageal motility and pH were recorded for 2 hours before and 4 hours after the administration of a standardized meal (2400 kJ [573 kcal]). Sequences of 6 consecutive 5-mL water swallows (separated by 20 seconds) were carried out 60 and 90 minutes (fasting) and 150, 180, 210, 240, 300, and 360 minutes (fed) after study drug administration. OCTT was determined from the increase in breath hydrogen after the meal. WGTT was determined from the time taken to excrete at least 16 of 20 ingested radiopaque markers, ingested as 2 capsules, each containing 10 radiopaque markers, with 240 mL of water. AEs were elicited at specified times throughout each session using nonleading questions, spontaneously reported AEs, and diary cards.

RESULTS

Study 1 enrolled 20 subjects (11 men, 9 women; age range, 20-52 years). Study 2 enrolled 16 subjects (10 men, 6 women; age range, 19-48 years). No clinically significant differences in the amplitude (mean difference in postprandial-preprandial AUC0-t/t, 6.09 mm Hg; 95% CI, -10.66 to 22.84), duration (difference, -0.08 second; 95% CI, -0.54 to 0.37), or velocity of propagation (difference, 0.90 cm/s; 95% CI, -0.66 to 2.46) of esophageal contractions, LESP (difference, -0.39 mm Hg; 95% CI, -5.23 to 4.45), or preprandial or postprandial percentage time pH<4 (median differences: preprandial, 0.47% [95% CI, -0.45 to 1.27]; postprandial, -0.005% [95% CI, -1.30 to 6.27]) were found with cilomilast compared with placebo. No significant differences in OCTT (difference, -0.37 hour; 95% CI, -1.59 to 0.84) or WGTT (difference, -2.96 hours; 95% CI, -20.76 to 14.84) were found with cilomilast compared with controls. In both studies, the most frequently reported AEs with cilomilast use were nausea (8/18 in study 1 and 3/16 in study 2) and headache (8/18 in study 1 and 6/16 in study 2); however, these were generally of mild to moderate intensity. Overall, GI AEs did not correlate with changes in GI motility.

CONCLUSION

The results of these 2 studies suggest that cilomilast was not associated with significant changes in esophageal motility and pH or GI transit in these healthy volunteers.

Intracellular targeting of phosphodiesterase-4 underpins compartmentalized cAMP signaling

The phosphodiesterase-4 (PDE4) enzyme belongs to a family of cAMP-dependent phosphodiesterases that provide the major means of hydrolyzing and, thereby, inactivating the key intracellular second messenger, cAMP. As such, PDE4s are central to the regulation of many diverse signaling processes that allow cells to respond to external stimuli. Four genes (4A, 4B, 4C, and 4D) encode around 20 distinct isoform members of the PDE4 family. Each isoform is characterized by a unique N-terminal region. PDE4s are multidomain metallohydrolases with each domain serving particular roles allowing them to be targeted to varying regions and organelles of intracellular space and regulated in distinct fashions by phosphorylation and protein-protein interaction. Although identical in catalytic function, each isoform locates to distinct regions within the cell so as to create and manage spatially distinct pools of cAMP. The multiplicity of partners associating with members of the four gene PDE4 family places these enzymes in key regulatory positions, permitting them to channel complex biological signals via fundamental signaling cohorts such as G-protein-coupled receptors (GPCRs), arrestins, A-kinase-anchoring proteins (AKAPs), and tyrosyl family kinases. The cAMP cascade has long been linked to cellular growth and embryogenesis and with this comes the implication that PDE4 may play considerable roles in the regulation of progeny development in maturing cells and tissues.

Clinical Pharmacology of Cilomilast

Chronic obstructive pulmonary disease (COPD) is a multicomponent, chronic inflammatory disease of the lungs with systemic complications. The majority of the inflammation occurs in the peripheral airways and lung parenchyma. It is a progressive disease, leading to disability and eventual death, despite conventional therapy. Inflammatory activity can be reduced by increasing intracellular cyclic adenosine-3',5'-monophosphate (cAMP) through inhibition of phosphodiesterase (PDE) IV, the principal PDE isoenzyme within pro-inflammatory cells, including eosinophils, mast cells, macrophages, lymphocytes, neutrophils and epithelial cells. PDE IV inhibition also has other effects, including relaxation of airway smooth muscle, suppression of smooth muscle mitogenesis and modulation of excitatory activity in pulmonary nerves. Cilomilast is a systemically available, second-generation, selective PDE IV inhibitor. It retains the therapeutic activity of the first-generation PDE IV inhibitors but lacks their profound emetic effect. Cilomilast is the first drug to demonstrate a reduction of tissue cells considered central to the ongoing inflammatory process (macrophages and CD8+ lymphocytes) in patients with stable COPD. Cilomilast is completely absorbed following oral administration and has negligible first-pass metabolism. It exhibits linear pharmacokinetics, with low between-subject variability. Cilomilast is highly protein bound (99.4%), but this binding is concentration-independent at clinically relevant doses, and it has a small volume of distribution at steady state (17L). Plasma clearance (approximately 2 L/h) is almost entirely metabolic, through multiple parallel pathways. Its terminal elimination half-life is approximately 6.5 hours and steady state is rapidly achieved with twice-daily administration. The most abundant metabolite, formed by the action of cytochrome P450 2C8, has <10% of the activity of the parent molecule. Cilomilast pharmacokinetics in COPD patients were consistent with those in healthy subjects. Smoking, age and ethnicity had no clinically relevant effects. Total plasma cilomilast pharmacokinetic parameters did not change significantly with renal or hepatic impairment, but concentrations of unbound cilomilast increased with declining renal or hepatic function. Cilomilast had no clinically relevant interactions with a range of drugs likely to be coadministered to patients with COPD, with the exception of erythromycin where concurrent administration with cilomilast was associated with an increased incidence of gastrointestinal adverse events, a pharmacodynamic interaction predicted by their secondary pharmacology. Nausea was the principal adverse reaction seen in healthy subjects taking cilomilast, but this was reduced by administration with food or by use of simple dose-escalation regimens. Cilomilast has not shown a propensity for any of the serious cardiac or neurological adverse effects associated with theophylline. Cilomilast exhibits favourable and predictable pharmacokinetics, has few clinically relevant drug-drug interactions and has demonstrated effects on measures of inflammation of potential benefit in the treatment of COPD. It is generally well tolerated and has not generated safety concerns in any clinical study.

Cilomilast for COPD

BACKGROUND

COPD is a relentless, progressive disease. This study evaluated the efficacy of cilomilast, a selective phosphodiesterase (PDE) 4 inhibitor, in the treatment of COPD.

METHODS

This was a randomized, double-blind, placebo-controlled, parallel-group, multicenter study in subjects with COPD. After a 4-week, single-blind, placebo run-in period, eligible subjects were randomized in a 2:1 ratio to receive oral cilomilast, 15 mg bid, or placebo for 24 weeks. Subjects between 40 and 80 years of age who had received a diagnosis of COPD were eligible for the study. The primary efficacy variables were changes from baseline in trough (ie, predose) FEV1 and in total score of the St. George's Respiratory Questionnaire (SGRQ). A key secondary end point was the incidence rate of COPD exacerbations.

RESULTS

The average change from baseline in FEV1 over 24 weeks in the cilomilast group was an increase of 10 mL compared with a decrease of 30 mL in the placebo group (difference, 40 mL; p = 0.002). When averaged over 24 weeks, there was a clinically significant reduction in the mean total SGRQ score in subjects receiving cilomilast therapy, with a difference of 4.1 U compared with subjects who received placebo (p = 0.001). A greater percentage of subjects in the cilomilast group were exacerbation-free at 24 weeks (74%; p = 0.008) compared with placebo (62%). Adverse events were generally mild or moderate and were not unexpected for this class of medications. GI adverse events that interfered with daily activities (cilomilast, 17%; placebo, 8%) predominantly occurred within the first 3 weeks of initiating cilomilast therapy.

CONCLUSION

Cilomilast is an orally active, potent, and selective inhibitor of PDE-4. Cilomilast maintained pulmonary function and improved health status, and reduced the rate of COPD exacerbations during 24 weeks of treatment. This study supports the use of cilomilast, a novel, selective PDE-4 inhibitor, in subjects with COPD.

Elastolytic activity and alveolar epithelial type-1 cell damage after chronic LPS inhalation: effects of dexamethasone and rolipram

This study investigated whether a correlation between leukocyte-derived elastolytic activity, alveolar epithelial type-1 cell damage, and leukocyte infiltration of the airways existed in guinea-pigs chronically exposed to inhaled lipopolysaccharide (LPS). The airway pathology of this model, notably the neutrophilia, resembles chronic obstructive pulmonary disease (COPD). The effect of the corticosteroid, dexamethasone, or the phosphodiesterase-4 (PDE4)-inhibitor, rolipram, on these features was studied. Conscious guinea-pigs were exposed for 1 h to single or repeated (nine) doses of LPS (30 microg ml(-1)). Dexamethasone (20 mg kg(-1), ip) or rolipram (1 mg kg(-1), ip) was administered 24 and 0.5 h before the first exposure and daily thereafter. Bronchoalveolar lavage fluid (BALF) was removed and elastolytic activity determined as the elastase-like release of Congo Red from impregnated elastin. The presence of the specific epithelial cell type-1 protein (40-42 kDa) RT1(40) in BALF was identified by Western blotting using a rat monoclonal antibody and semi-quantified by dot-blot analysis. The antibody was found to identify guinea-pig RT1(40). BALF inflammatory cells, particularly neutrophils and macrophages, and elastolytic activity were increased in chronic LPS-exposed guinea-pigs, the latter by 90%. Chronic LPS exposure also increased (10.5-fold) RT1(40) levels, indicating significant alveolar epithelial type-1 cell damage. Dexamethasone or rolipram treatment reduced the influx of inflammatory cells, the elastolytic activity (by 40% and 38%, respectively), and RT1(40) levels (by 50% and 57%, respectively). In conclusion, chronic LPS-exposed guinea-pigs, like COPD, exhibit elastolytic lung damage. This was prevented by a PDE4 inhibitor and supports their development for suppressing this leukocyte-mediated pathology.

Airway function and reactivity, leukocyte influx and nitric oxide after inoculation with parainfluenza-3 virus: effects of dexamethasone or rolipram

Guinea-pigs were inoculated with parainfluenza type 3 (PI3) virus (5.2 x 10(7)) or medium (125 microl each nostril). The PDE4-inhibitor, rolipram (1 mg kg(-1)), the corticosteroid, dexamethasone (20 mg kg(-1)), or vehicle were administered (i.p.) 24 h and 0.5 h before inoculation and for 4 days thereafter. Respiratory function, recorded in conscious guinea-pigs as specific airways conductance (sGaw) by whole-body plethysmography, was unaffected over 4 days by inoculation with medium or PI3. Inhaled histamine (nose-only, 1 mM, 20 s) 24 h before inoculation produced no response but 4 days after PI3 inoculation, a significant (P<0.001) bronchoconstriction occurred, indicating airway hyperreactivity (AHR). Dexamethasone or rolipram treatment inhibited the AHR. Four days after PI3- or medium-inoculation, animals underwent bronchoalveolar lavage (BAL) for total and differential (macrophages, eosinophils and neutrophils) cell counts and determination of nitric oxide (NO) as nitrite and nitrate. Compared with medium-inoculated animals, BAL fluid removed 4 days after PI3 inoculation had significantly increased macrophages, eosinophils and neutrophils. Dexamethasone or rolipram significantly (P<0.05) reduced the PI3-induced airways influx of macrophages (by 40% and 47%), eosinophils (79% and 84%) and neutrophils (58% and 61%). PI3-inoculation significantly (P<0.05) increased BALF combined NO metabolites (84.8+/-2.2 microM 100 microl(-1)), compared with medium-inoculated (56.0+/-5.8) or naive animals (45.7+/-2.0). Treating the PI3-infected guinea-pigs with dexamethasone or rolipram significantly (P<0.001) reduced the raised NO metabolites by 34% and 37%, respectively. These results support a role for steroids and PDE4-inhibitors in the management of inflammation and airways hyperreactivity arising from viral infection of the airways.