The short-term bronchodilator effects of the dual phosphodiesterase 3 and 4 inhibitor RPL554 in COPD

Perspectives on Ensifentrine and Its Therapeutic Potential in the Treatment of COPD: Evidence to Date

Ensifentrine is a novel inhalational phosphodiesterase (PDE)3 and PDE4 inhibitor which improves bronchodilation and decreases inflammatory markers by acting locally on the bronchial tissue, with minimal systemic effects. Both preclinical and clinical trials have demonstrated benefits of this therapy, including improvement in lung function and reduction in exacerbations. This therapy is currently under review by the US Food and Drug Administration with a decision expected in 2024.

Therapeutic Targets and Precision Medicine in COPD: Inflammation, Ion Channels, Both, or Neither?

The development of a wider range of therapeutic options is a key objective in drug discovery for chronic obstructive pulmonary disease (COPD). Fundamental advances in lung biology have the potential to greatly expand the number of therapeutic targets in COPD. The recently reported successful Phase 3 clinical trial of the first biologic agent for COPD, the monoclonal antibody dupilumab, adds additional support to the importance of targeting inflammatory pathways in COPD. However, numerous other cellular mechanisms are important targets in COPD therapeutics, including airway remodeling, the CFTR ion channel, and mucociliary function. Some of these emerging targets can be exploited by the expanded use of existing COPD drugs, such as roflumilast, while targeting others will require the development of novel molecular entities. The identification of additional therapeutic targets and agents has the potential to greatly expand the value of using clinical and biomarker data to classify COPD into specific subsets, each of which can be predictive of an enhanced response to specific subset(s) of targeted therapies. The author reviews established and emerging drug targets in COPD and uses this as a framework to define a novel classification of COPD based on therapeutic targets. This novel classification has the potential to enhance precision medicine in COPD patient care and to accelerate clinical trials and pre-clinical drug discovery efforts.

What role will ensifentrine play in the future treatment of chronic obstructive pulmonary disease patients? Implications from recent clinical trials

Data from the phase III ENHANCE clinical trials provide compelling evidence that ensifentrine, an inhaled 'bifunctional' dual phosphodiesterase 3/4 inhibitor, can provide additional benefit to existing treatments in patients with chronic obstructive pulmonary disease and represents a 'first-in-class' drug having bifunctional bronchodilator and anti-inflammatory activity in a single molecule. Ensifentrine, generally well tolerated, can provide additional bronchodilation when added to muscarinic receptor antagonists or β2-agonists and reduce the exacerbation risk. This information allows us to consider better the possible inclusion of ensifentrine in the future treatment of chronic obstructive pulmonary disease. However, there is less information on whether it provides additional benefit when added to inhaled corticosteroid or 'triple therapy' and, therefore, when this drug is best utilized in clinical practice.

Ensifentrine as a Novel, Inhaled Treatment for Patients with COPD

Ensifentrine is a novel, potent, and selective dual inhibitor of phosphodiesterase (PDE)3 and PDE4 designed for delivery by inhalation that combines effects on airway inflammation, bronchodilation and ciliary function in bronchial epithelia. In Phase 2 studies in subjects with COPD, ensifentrine demonstrated clinically meaningful bronchodilation and improvements in symptoms and health-related quality of life when administered alone or in combination with current standard of care therapies. Ensifentrine is currently in late-stage clinical development for the maintenance treatment of patients with COPD. This review summarizes non-clinical data as well as Phase 1 and Phase 2 efficacy and safety results of nebulized ensifentrine relevant to the maintenance treatment of patients with COPD.

PDE4 Inhibitors: Profiling Hits through the Multitude of Structural Classes

Cyclic nucleotide phosphodiesterases 4 (PDE4) are a family of enzymes which specifically promote the hydrolysis and degradation of cAMP. The inhibition of PDE4 enzymes has been widely investigated as a possible alternative strategy for the treatment of a variety of respiratory diseases, including chronic obstructive pulmonary disease and asthma, as well as psoriasis and other autoimmune disorders. In this context, the identification of new molecules as PDE4 inhibitors continues to be an active field of investigation within drug discovery. This review summarizes the medicinal chemistry journey in the design and development of effective PDE4 inhibitors, analyzed through chemical classes and taking into consideration structural aspects and binding properties, as well as inhibitory efficacy, PDE4 selectivity and the potential as therapeutic agents.

Experimental drugs in clinical trials for COPD: Artificial Intelligence via Machine Learning approach to predict the successful advance from early-stage development to approval

INTRODUCTION

Therapeutic advances in drug therapy of chronic obstructive pulmonary disease (COPD) really effective in suppressing the pathological processes underlying the disease deterioration are still needed. Artificial Intelligence (AI) via Machine Learning (ML) may represent an effective tool to predict clinical development of investigational agents.

AREAL COVERED

Experimental drugs in Phase I and II development for COPD from early 2014 to late 2022 were identified in the ClinicalTrials.gov database. Different ML models, trained from prior knowledge on clinical trial success, were used to predict the probability that experimental drugs will successfully advance toward approval in COPD, according to Bayesian inference as follows: ≤25% low probability, >25% and ≤ 50% moderate probability, >50% and ≤ 75% high probability, and > 75% very high probability.

EXPERT OPINION

The Artificial Neural Network and Random Forest ML models indicated that, among the current experimental drugs in clinical trials for COPD, only the bifunctional muscarinic antagonist - β₂-adrenoceptor agonists (MABA) navafenterol and batefenterol, the inhaled corticosteroid (ICS)/MABA fluticasone furoate/batefenterol, and the bifunctional phosphodiesterase (PDE) 3/4 inhibitor ensifentrine resulted to have a moderate to very high probability of being approved in the next future, however not before 2025.

Contribution of adaptive immunity to human COPD and experimental models of emphysema

The pathophysiology of chronic obstructive pulmonary disease (COPD) and the undisputed role of innate immune cells in this condition have dominated the field in the basic research arena for many years. Recently, however, compelling data suggesting that adaptive immune cells may also contribute to the progressive nature of lung destruction associated with COPD in smokers have gained considerable attention. The histopathological changes in the lungs of smokers can be limited to the large or small airways, but alveolar loss leading to emphysema, which occurs in some individuals, remains its most significant and irreversible outcome. Critically, however, the question of why emphysema progresses in a subset of former smokers remained a mystery for many years. The recognition of activated and organized tertiary T- and B-lymphoid aggregates in emphysematous lungs provided the first clue that adaptive immune cells may play a crucial role in COPD pathophysiology. Based on these findings from human translational studies, experimental animal models of emphysema were used to determine the mechanisms through which smoke exposure initiates and orchestrates adaptive autoreactive inflammation in the lungs. These models have revealed that T helper (Th)1 and Th17 subsets promote a positive feedback loop that activates innate immune cells, confirming their role in emphysema pathogenesis. Results from genetic studies and immune-based discoveries have further provided strong evidence for autoimmunity induction in smokers with emphysema. These new findings offer a novel opportunity to explore the mechanisms underlying the inflammatory landscape in the COPD lung and offer insights for development of precision-based treatment to halt lung destruction.

Conventional, Complementary and Alternative Medicines: Mechanistic Insights into Therapeutic Landscape of Chronic Obstructive Pulmonary Disease

COPD (chronic obstructive pulmonary disease) is a major public health concern associated with significant morbidity and mortality worldwide. Current therapeutic guidelines for this disease recommend starting with an inhaled bronchodilator, stepping up to combination therapy as necessary, and/or adding inhaled corticosteroids as symptoms and airflow obstruction progress. However, no drug therapy exists to stop disease progression. The mechanistic definition underlying COPD pathogenesis remains poorly understood, it is generally accepted that oxidative stress and the altered immune response of low-grade airway inflammation are major factors contributing to COPD development. There are several potential therapeutic targets that are currently under investigation, including immune regulatory pathways in inflammation and lung-associated steroid resistance induced by oxidative stress signaling cascades. Patients with COPD have increased levels of inflammatory mediators, including lipid and peptide mediators, as well as a network of cytokines and chemokines that maintain inflammatory immune response and recruit circulating cells into the lungs. Many of these pro-inflammatory mediators are regulated by nuclear factor-kappaB (NF-κB) and mitogen-activated protein kinases (MAPKs), such as p38 MAPK. Increased oxidative stress is a key driving mechanism in perpetuating inflammation and lung injury. Furthermore, many proteases that degrade elastin fibres are secreted by airway resident infiltrating immune cells in COPD patients. In this perspective, we discuss novel aspects of signaling pathway activation in the context of inflammation and oxidative stress, and the broad view of potential effective pharmacotherapies that target the underlying mechanistic disease process in COPD.

Pathophysiology, Therapeutic Targets, and Future Therapeutic Alternatives in COPD: Focus on the Importance of the Cholinergic System

Chronic obstructive pulmonary disease (COPD) is a progressive disease characterized by airway limitation and changes in airway structure. It has a high global burden of mortality and morbidity. The etiology of COPD is complex, but exposure to tobacco smoke and other inhaled lung oxidants are major risk factors. Both pharmacological and non-pharmacological approaches are used to manage COPD, but there remains an urgent unmet need for drugs that can modify the course of the disease. This review focuses on the role of acetylcholine and other components of the pulmonary cholinergic system in the pathogenesis of COPD, and the inhaled pharmacological agents that target it. In addition to its role as a neurotransmitter, acetylcholine regulates diverse aspects of COPD pathogenesis including bronchoconstriction, airway remodeling, mucus secretion and inflammation. Inhaled antimuscarinic drugs are a key component of therapy for COPD, as monotherapy or in combination with inhaled β2 agonists or corticosteroids. We review the evidence supporting the use of current anticholinergic agents in COPD and preview novel drugs targeting the cholinergic system and agents from other classes in clinical development, such as phosphodiesterase-4 inhibitors and monoclonal antibodies targeting inflammatory mediators.

An Overview of PDE4 Inhibitors in Clinical Trials: 2010 to Early 2022

Since the early 1980s, phosphodiesterase 4 (PDE4) has been an attractive target for the treatment of inflammation-based diseases. Several scientific advancements, by both academia and pharmaceutical companies, have enabled the identification of many synthetic ligands for this target, along with the acquisition of precise information on biological requirements and linked therapeutic opportunities. The transition from pre-clinical to clinical phase was not easy for the majority of these compounds, mainly due to their significant side effects, and it took almost thirty years for a PDE4 inhibitor to become a drug i.e., Roflumilast, used in the clinics for the treatment of chronic obstructive pulmonary disease. Since then, three additional compounds have reached the market a few years later: Crisaborole for atopic dermatitis, Apremilast for psoriatic arthritis and Ibudilast for Krabbe disease. The aim of this review is to provide an overview of the compounds that have reached clinical trials in the last ten years, with a focus on those most recently developed for respiratory, skin and neurological disorders.

Pathological Mechanism and Targeted Drugs of COPD

Chronic obstructive pulmonary disease (COPD) includes chronic bronchitis, emphysema, and small airway obstruction. Incompletely reversible airflow limitation, inflammation, excessive mucus secretion and bronchial mucosal epithelial lesions are the main pathological basis of the disease. The prevalence of COPD is increasingly worldwide, which has caused the burden on individuals and society. This paper summarizes the pathogenesis of COPD and clarifies the effect and mechanism of the latest targeted drugs for COPD. Besides, we focus on NOD-like receptor thermal protein domain associated protein 3 inflammasome (NLRP3 inflammasome). NLRP3 can promote production of interleukin-1β (IL-1β) and interleukin-18 (IL-18). NLRP3 is an important factor in the migratory aggregation of macrophages and neutrophils and the generation of oxidative stress. Inhibition of NLRP3 inflammasome indirectly blocks the inflammatory effects of IL-1β and IL-18, which may be regarded as an ideal target for COPD treatment.

The future of inhalation therapy in chronic obstructive pulmonary disease

The inhaled route is critical for the administration of drugs to treat patients suffering from COPD, but there is still an unmet need for new and innovative inhalers to address some limitations of existing products that do not make them suitable for many COPD patients. The treatment of COPD, currently limited to the use of bronchodilators, corticosteroids, and antibiotics, requires a significant expansion of the therapeutic armamentarium that is closely linked to the widening of knowledge on the pathogenesis and evolution of COPD. The great interest in the development of new drugs that may be able to interfere in the natural history of the disease is leading to the synthesis of numerous new molecules, of which however only a few have entered the stages of clinical development. On the other hand, further improvement of inhaled drug delivery could be an interesting possibility because it targets the organ of interest directly, requires significantly less drug to exert the pharmacological effect and, by lowering the amount of drug needed, reduces the cost of therapy. Unfortunately, however, the development of new inhaled drugs for use in COPD is currently too slow.

•

Inhalation therapy is central when treating patients with COPD.

•

There has been and still there is a substantial evolution in inhaler devices.

•

New targets possibly useful for the development of new drugs have been identified.

•

Only very few of new drugs are being evaluated for inhaled administration.

Inhaled Phosphodiesterase Inhibitors for the Treatment of Chronic Obstructive Pulmonary Disease

Phosphodiesterase (PDE) 4 inhibitors prevent the metabolism of cyclic adenosine monophosphate, thereby reducing inflammation. Inhaled PDE4 inhibitors aim to restrict systemic drug exposure to enhance the potential for clinical benefits (in the lungs) versus adverse events (systemically). The orally administered PDE4 inhibitor roflumilast reduces exacerbation rates in the subgroup of chronic obstructive pulmonary disease patients with a history of exacerbations and the presence of chronic bronchitis, but can cause PDE4 related adverse effects due to systemic exposure. CHF6001 is an inhaled PDE4 inhibitor, while inhaled ensifentrine is an inhibitor of both PDE3 and PDE4; antagonism of PDE3 facilitates smooth muscle relaxation and hence bronchodilation. These inhaled PDE inhibitors have both reported positive findings from early phase clinical trials, and have been well tolerated. Longer term trials are needed to firmly establish the clinical benefits of these drugs.

Inhaled Dual Phosphodiesterase 3/4 Inhibitors for the Treatment of Patients with COPD: A Short Review

Current pharmacological treatments for chronic obstructive pulmonary disease (COPD) are mostly limited to inhaled bronchodilators and corticosteroids. Azithromycin can contribute to exacerbation prevention. Roflumilast, a phosphodiesterase (PDE) 4 inhibitor administered orally, also prevents exacerbations in selected patients with chronic bronchitis, recurrent exacerbations, severe airflow limitation and concomitant therapy with long-acting inhaled bronchodilators. This outcome likely results from anti-inflammatory effects since PDE4 is expressed by all inflammatory cell types involved in COPD. The use of this agent is, however, limited by side-effects, particularly nausea and diarrhea. To address remaining unmet needs and enrich therapeutic options for patients with COPD, inhaled dual PDE3/4 inhibitors have been developed, with the aim of enhancing bronchodilation through PDE3 inhibition and modulating inflammation and mucus production though PDE4 inhibition, thus producing a potentially synergistic effect on airway calibre. Experimental preclinical data confirmed these effects in vitro and in animal models. At present, RPL554/ensifentrine is the only agent of this family in clinical development. It decreases sputum markers of both neutrophilic and eosinophilic inflammation in patients with COPD. Clinical Phase II trials confirmed its bronchodilator effect and demonstrated clinically meaningful symptom relief and quality of life improvements in these patients. The safety profile appears satisfactory, with less effects on heart rate and blood pressure than salbutamol and no other side effect. Altogether, these data suggest that ensifentrine could have a role in COPD management, especially in addition to inhaled long-acting bronchodilators with or without corticosteroids since experimental studies suggest potentiation of ensifentrine effects by these agents. However, results from ongoing and future Phase III studies are needed to confirm both beneficial effects and favourable safety profile on a larger scale and assess other outcomes including exacerbations, lung function decline, comorbidities and mortality.

Identification and treatment of T2-low asthma in the era of biologics

Currently, and based on the development of relevant biologic therapies, T2-high is the most well-defined endotype of asthma. Although much progress has been made in elucidating T2-high inflammation pathways, no specific clinically applicable biomarkers for T2-low asthma have been identified. The therapeutic approach of T2-low asthma is a problem urgently needing resolution, firstly because these patients have poor response to steroids, and secondly because they are not candidates for the newer targeted biologic agents. Thus, there is an unmet need for the identification of biomarkers that can help the diagnosis and endotyping of T2-low asthma. Ongoing investigation is focusing on neutrophilic airway inflammation mediators as therapeutic targets, including interleukin (IL)-8, IL-17, IL-1, IL-6, IL-23 and tumour necrosis factor-α; molecules that target restoration of corticosteroid sensitivity, mainly mitogen-activated protein kinase inhibitors, tyrosine kinase inhibitors and phosphatidylinositol 3-kinase inhibitors; phosphodiesterase (PDE)3 inhibitors that act as bronchodilators and PDE4 inhibitors that have an anti-inflammatory effect; and airway smooth muscle mass attenuation therapies, mainly for patients with paucigranulocytic inflammation. This article aims to review the evidence for noneosinophilic inflammation being a target for therapy in asthma; discuss current and potential future therapeutic approaches, such as novel molecules and biologic agents; and assess clinical trials of licensed drugs in the treatment of T2-low asthma.

A Dose-Ranging Study of the Novel Inhaled Dual PDE 3 and 4 Inhibitor Ensifentrine in Patients with COPD Receiving Maintenance Tiotropium Therapy

PURPOSE

Ensifentrine is an inhaled dual inhibitor of phosphodiesterase (PDE) 3 and 4 that has shown bronchodilatory effects and symptom improvement in clinical studies in patients with chronic obstructive pulmonary disease (COPD), and anti-inflammatory effects in healthy volunteers in a model of COPD-like inflammation. This manuscript reports on the results of the clinical study examining if ensifentrine provides meaningful improvements in lung function when added on to tiotropium over 4 weeks in patients with COPD who have impaired lung function and symptoms despite treatment with tiotropium.

PATIENTS AND METHODS

This randomized, double-blind, placebo-controlled, parallel-group, dose-ranging study recruited patients with moderate-to-severe COPD. Patients were randomized to open-label tiotropium once daily (QD) plus (+) blinded escalating doses of ensifentrine or placebo twice daily (BID). Effects on lung function, symptoms and quality of life (QoL) were assessed over 4 weeks.

RESULTS

A total of 416 COPD patients were randomized and 413 received at least one dose of blinded study medication + tiotropium. All ensifentrine doses produced a significant and dose-dependent increase in peak forced expiratory volume in 1 second (FEV1) from baseline to Week 4, with placebo-corrected differences of 77.5 mL when added to tiotropium (0.375 mg; 95% CI: 4.8, 150.1 mL; p=0.037) to 124.2 mL (3 mg; 95% CI: 51.0, 196.8 mL; p<0.001). A significant increase in average FEV1 (0-12h) was shown at Week 4 with the 3 mg dose (87.3 mL; 95% CI: 20.0, 154.5 mL; p=0.011). Clinically meaningful and statistically significant improvements in the St. George's Respiratory Questionnaire - COPD (SGRQ-C) additive to tiotropium were observed at Week 4, exceeding the minimally clinically important difference of 4 units with the 1.5 and 3 mg doses. Adverse events were similar in frequency between the ensifentrine and placebo arms.

CONCLUSION

This clinical study demonstrated that nebulized ensifentrine added on to tiotropium produced clinically important improvements in lung function and QoL over 4 weeks in COPD patients receiving tiotropium who demonstrated symptoms and lung function impairment, with a safety profile similar to placebo.

Why new biology must be uncovered to advance therapeutic strategies for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by the destruction of alveolar tissue (in emphysema) and airway remodeling (leading to chronic bronchitis), which cause difficulties in breathing. It is a growing public health concern with few therapeutic options that can reverse disease progression or mortality. This is in part because current treatments mainly focus on ameliorating symptoms induced by inflammatory pathways as opposed to curing disease. Hence, emerging research focused on upstream pathways are likely to be beneficial in the development of efficient therapeutics to address the root causes of disease. Some of these pathways include mitochondrial function, cytoskeletal structure and maintenance, and airway hydration, which are all affected by toxins that contribute to COPD. Because of the complexity of COPD and unknown targets for disease onset, simpler model organisms have proved to be useful tools in identifying disease-relevant pathways and targets. This review summarizes COPD pathology, current treatments, and therapeutic discovery research, with a focus on the aforementioned pathways that can advance the therapeutic landscape of COPD.

Prospects for COPD treatment

The management of chronic obstructive pulmonary disease (COPD) is fundamentally still heavily dependent on the use of bronchodilators and corticosteroids. Therefore, there is a need for alternative, more effective and safer therapeutic approaches. In particular, since inflammation in COPD lungs is often poorly responsive to corticosteroid treatment, novel pharmacological anti-inflammatory approaches are needed to optimally treat COPD patients. There have been multiple attempts to develop drugs that inhibit recruitment and activation of inflammatory cells, such as macrophages, neutrophils and T-lymphocytes, in the lungs of patients with COPD or target inflammatory mediators that are important in the recruitment or activation of these inflammatory cells or released by such cells. This review article focuses on novel classes of anti-inflammatory drugs that have already been tested in humans as possible treatments for patients with COPD.

The Phosphodiesterase Inhibitor Ensifentrine Reduces Production of Proinflammatory Mediators in Well Differentiated Bronchial Epithelial Cells by Inhibiting PDE4

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel that impair airway salt and fluid secretion. Excessive release of proinflammatory cytokines and chemokines by CF bronchial epithelium during airway infection leads to chronic inflammation and a slow decline in lung function; thus, there is much interest in finding safe and effective treatments that reduce inflammation in CF. We showed previously that the cyclic nucleotide phosphodiesterase (PDE) inhibitor ensifentrine (RPL554; Verona Pharma) stimulates the channel function of CFTR mutants with abnormal gating and also those with defective trafficking that are partially rescued using a clinically approved corrector drug. PDE inhibitors also have known anti-inflammatory effects; therefore, we examined whether ensifentrine alters the production of proinflammatory cytokines in CF bronchial epithelial cells. Ensifentrine reduced the production of monocyte chemoattractant protein-1 and granulocyte monocyte colony-stimulating factor (GM-CSF) during challenge with interleukin-1β Comparing the effect of ensifentrine with milrinone and roflumilast, selective PDE3 and PDE4 inhibitors, respectively, demonstrated that the anti-inflammatory effect of ensifentrine was mainly due to inhibition of PDE4. Beneficial modulation of GM-CSF was further enhanced when ensifentrine was combined with low concentrations of the β ₂-adrenergic agonist isoproterenol or the corticosteroid dexamethasone. The results indicate that ensifentrine may have beneficial anti-inflammatory effects in CF airways particularly when used in combination with β ₂-adrenergic agonists or corticosteroids. SIGNIFICANCE STATEMENT: Airway inflammation that is disproportionate to the burden of chronic airway infection causes much of the pathology in the cystic fibrosis (CF) lung. We show here that ensifentrine beneficially modulates the release of proinflammatory factors in well differentiated CF bronchial epithelial cells that is further enhanced when combined with β₂-adrenergic agonists or low-concentration corticosteroids. The results encourage further clinical testing of ensifentrine, alone and in combination with β₂-adrenergic agonists or low-concentration corticosteroids, as a novel anti-inflammatory therapy for CF.

Pharmacology and Therapeutics of Bronchodilators Revisited

Bronchodilators remain the cornerstone of the treatment of airway disorders such as asthma and chronic obstructive pulmonary disease (COPD). There is therefore considerable interest in understanding how to optimize the use of our existing classes of bronchodilator and in identifying novel classes of bronchodilator drugs. However, new classes of bronchodilator have proved challenging to develop because many of these have no better efficacy than existing classes of bronchodilator and often have unacceptable safety profiles. Recent research has shown that optimization of bronchodilation occurs when both arms of the autonomic nervous system are affected through antagonism of muscarinic receptors to reduce the influence of parasympathetic innervation of the lung and through stimulation of β ₂-adrenoceptors (β ₂-ARs) on airway smooth muscle with β ₂-AR-selective agonists to mimic the sympathetic influence on the lung. This is currently achieved by use of fixed-dose combinations of inhaled long-acting β ₂-adrenoceptor agonists (LABAs) and long-acting muscarinic acetylcholine receptor antagonists (LAMAs). Due to the distinct mechanisms of action of LAMAs and LABAs, the additive/synergistic effects of using these drug classes together has been extensively investigated. More recently, so-called "triple inhalers" containing fixed-dose combinations of both classes of bronchodilator (dual bronchodilation) and an inhaled corticosteroid in the same inhaler have been developed. Furthermore, a number of so-called "bifunctional drugs" having two different primary pharmacological actions in the same molecule are under development. This review discusses recent advancements in knowledge on bronchodilators and bifunctional drugs for the treatment of asthma and COPD. SIGNIFICANCE STATEMENT: Since our last review in 2012, there has been considerable research to identify novel classes of bronchodilator drugs, to further understand how to optimize the use of the existing classes of bronchodilator, and to better understand the role of bifunctional drugs in the treatment of asthma and chronic obstructive pulmonary disease.

Symptom Improvement Following Treatment with the Inhaled Dual Phosphodiesterase 3 and 4 Inhibitor Ensifentrine in Patients with Moderate to Severe COPD - A Detailed Analysis

Introduction

Ensifentrine is an inhaled first-in-class dual inhibitor of phosphodiesterase (PDE) 3 and 4. In a four-week randomized, double-blind, placebo-controlled, parallel-group study in patients with chronic obstructive pulmonary disease (COPD), nebulized ensifentrine 0.75 to 6mg twice daily significantly improved bronchodilation and symptoms, with all doses being well tolerated. Here, we report data for a number of prespecified exploratory and post hoc endpoints from this study that help to further profile the effect of ensifentrine on symptoms.

Methods

Eligible patients were males or females aged 40-75 years with COPD, post-bronchodilator forced expiratory volume in 1 second 40-80% predicted. Other than being clinically stable for at least four weeks prior to entry, there were no symptomatic inclusion or exclusion criteria. The outcome measures reported in this manuscript are the Evaluating Respiratory Symptoms [E-RS™:COPD] questionnaire total score and subscales (breathlessness, cough/sputum and chest symptoms) at Weeks 1-4, Transition Dyspnea Index (TDI) focal score at Weeks 2 and 4, and St George's Respiratory Questionnaire - COPD Specific (SGRQ-C) total score and domain data (symptoms, activity and impacts) at Week 4.

Results

There was a gradual improvement versus placebo with all ensifentrine doses for all three E-RS™:COPD subscales from Week 1 to Week 4, with the greatest ensifentrine effect on the breathlessness subscale, and all four doses superior to placebo from Week 2 onwards (p<0.05). For TDI focal score, all ensifentrine doses were superior to placebo at Weeks 2 and 4 (p<0.05). In the individual SGRQ-C domains at Week 4, ensifentrine had the greatest effect on the symptoms domain, with ensifentrine 6mg superior to placebo (p<0.05).

Conclusion

In these analyses, ensifentrine demonstrated a notable early and meaningful effect on dyspnea, with this effect observed across two different assessment tools.

Investigational treatments in phase I and II clinical trials: a systematic review in chronic obstructive pulmonary disease (COPD)

Introduction. The current pharmacological treatments for the management of stable COPD permit the reduction of symptoms and frequency and severity of exacerbations, and the improvement of exercise tolerance and health status. However, they do not modify the long-term decline in lung function and patient health. Consequently, there is the strong need for 'highly innovative' medications that are focused on new targets and/or mechanisms for the treatment of COPD. Areas covered. This systematic review assesses investigational agents in Phase I and II clinical trials over the last six years. It offers insights on whether drugs and/or formulations in clinical development offer future effective treatments of COPD. Expert opinion. There is no evidence to suggest that current investigational agents can reduce lung function decline and cure COPD. However, looking forward, investigational, innovative treatments in combination with the therapies already recommended by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) may provide future suitable tools to counteract the progression of COPD.

Future Trends in Nebulized Therapies for Pulmonary Disease

Aerosol therapy is a key modality for drug delivery to the lungs of respiratory disease patients. Aerosol therapy improves therapeutic effects by directly targeting diseased lung regions for rapid onset of action, requiring smaller doses than oral or intravenous delivery and minimizing systemic side effects. In order to optimize treatment of critically ill patients, the efficacy of aerosol therapy depends on lung morphology, breathing patterns, aerosol droplet characteristics, disease, mechanical ventilation, pharmacokinetics, and the pharmacodynamics of cell-drug interactions. While aerosol characteristics are influenced by drug formulations and device mechanisms, most other factors are reliant on individual patient variables. This has led to increased efforts towards more personalized therapeutic approaches to optimize pulmonary drug delivery and improve selection of effective drug types for individual patients. Vibrating mesh nebulizers (VMN) are the dominant device in clinical trials involving mechanical ventilation and emerging drugs. In this review, we consider the use of VMN during mechanical ventilation in intensive care units. We aim to link VMN fundamentals to applications in mechanically ventilated patients and look to the future use of VMN in emerging personalized therapeutic drugs.

Respiratory Cilia as a Therapeutic Target of Phosphodiesterase Inhibitors

Mucociliary clearance is an essential airway defense mechanism dependent predominantly on the proper ciliary function and mucus rheology. The crucial role of cilia is evident in `a variety of respiratory diseases, as the ciliary dysfunction is associated with a progressive decline in lung function over time. The activity of cilia is under supervision of multiple physiological regulators, including second messengers. Their role is to enable a movement in coordinated metachronal waves at certain beat frequency. Ciliary function can be modulated by various stimuli, including agents from the group of beta₂ agonists, cholinergic drugs, and adenosine triphosphate (ATP). They trigger cilia to move faster in response to elevated cytoplasmic Ca²⁺ originated from intracellular sources or replenished from extracellular space. Well-known cilia-stimulatory effect of Ca²⁺ ions can be abolished or even reversed by modulating the phosphodiesterase (PDE)-mediated breakdown of cyclic adenosine monophosphate (cAMP) since the overall change in ciliary beating has been dependent on the balance between Ca²⁺ ions and cAMP. Moreover, in chronic respiratory diseases, high ATP levels may contribute to cAMP hydrolysis and thus to a decrease in the ciliary beat frequency (CBF). The role of PDE inhibitors in airway cilia-driven transport may help in prevention of progressive loss of pulmonary function often observed despite current therapy. Furthermore, administration of selective PDE inhibitors by inhalation lowers the risk of their systemic effects. Based on this review we may conclude that selective (PDE1, PDE4) or dual PDE inhibitors (PDE3/4) increase the intracellular level of cyclic nucleotides in airway epithelial cells and thus may be an important target in the development of new inhaled mucokinetic agents. Further research is required to provide evidence of their effectiveness and feasibility regarding their cilia-modulating properties.

Inhaled Phosphodiesterase 4 (PDE4) Inhibitors for Inflammatory Respiratory Diseases

PDE4 inhibitors can suppress a variety of inflammatory cell functions that contribute to their anti-inflammatory actions in respiratory diseases like chronic obstructive pulmonary disease (COPD) and asthma. The systemically delivered PDE4 inhibitor roflumilast has been approved for use in a subset of patients with severe COPD with chronic bronchitis and a history of exacerbations. Use of systemically delivered PDE4 inhibitors has been limited by systemic side effects. Inhaled PDE4 inhibitors have been considered as a viable alternative to increase tolerability and determine the maximum therapeutic potential of PDE4 inhibition in respiratory diseases.

Role of phosphodiesterase-4 inhibitors in chronic obstructive pulmonary disease

Phosphodiesterase-4 inhibitors (PDE4Is) are potent anti-inf lammatory agents and roflumilast has been used to prevent acute exacerbation of chronic obstructive pulmonary disease (COPD). Roflumilast decreases neutrophil migration, restores cystic fibrosis transmembrane conductance regulator activity, and recovers glucocorticoid effects. A forced expiratory volume in 1 second of < 50%, a chronic bronchitis phenotype, high blood eosinophil levels, and a history of hospitalization are biomarkers for predicting responses to roflumilast. Adverse effects are common in clinical practice. An inhaled PDE4I has recently been developed and is under clinical trial. CHF6001 and RPL554 exhibit promise and may be future treatment options for COPD.

A dose-ranging study of the inhaled dual phosphodiesterase 3 and 4 inhibitor ensifentrine in COPD

BACKGROUND

Many patients with chronic obstructive pulmonary disease (COPD) still experience daily symptoms, exacerbations, and accelerated lung function decline, even when receiving maximal combined treatment with inhaled long-acting bronchodilators and corticosteroids. Novel treatment options are needed for these patients. Phosphodiesterases (PDEs) are enzymes that impact a range of cellular functions by modulating levels of cyclic nucleotides, and there is evidence to suggest that combined inhibition of PDE3 and PDE4 can have additive (or perhaps synergistic) effects. This study investigated the efficacy and safety of ensifentrine, a first-in-class dual inhibitor of PDE 3 and 4, in patients with COPD.

METHODS

This randomised, double-blind, placebo-controlled, parallel-group, dose-ranging study recruited patients with COPD, post-bronchodilator forced expiratory volume in 1 s (FEV1) 40-80% predicted and FEV1/forced vital capacity ratio ≤ 0.7. Patients were randomised equally to inhale nebulised ensifentrine 0.75, 1.5, 3 or 6 mg or placebo, all twice daily.

PRIMARY OUTCOME

placebo-adjusted difference in peak FEV1 (assessed over 3 h) at Week 4.

RESULTS

The study took place between July 2017 and February 2018. Of 405 patients randomly assigned to medication, 375 (92.6%) completed the study. For peak FEV1 at Week 4, all four ensifentrine doses were superior to placebo (p ≤ 0.0001) with least squares mean differences of 146 (95% CI 75-216), 153 (83-222), 200 (131-270) and 139 (69-210) mL for ensifentrine 0.75, 1.5, 3 and 6 mg, respectively. Respiratory symptoms (assessed using the Evaluating Respiratory Symptoms questionnaire) were also significantly improved with all ensifentrine doses at Week 4. Adverse events were reported by 33.3, 44.4, 35.4 and 36.3% patients with ensifentrine 0.75, 1.5, 3 and 6 mg, respectively, and 39.2% with placebo.

CONCLUSIONS

In this four-week Phase IIb study, all four ensifentrine doses significantly improved bronchodilation and symptoms, with a dose-ranging effect from 0.75 to 3 mg twice daily, and all doses well tolerated. The study supports the continuing development of ensifentrine in COPD.

TRIAL REGISTRATION

EudraCT 2016-005205-40, registered 30 May 2017.

The future of bronchodilation: looking for new classes of bronchodilators

Available bronchodilators can satisfy many of the needs of patients suffering from airway disorders, but they often do not relieve symptoms and their long-term use raises safety concerns. Therefore, there is interest in developing new classes that could help to overcome the limits that characterise the existing classes.At least nine potential new classes of bronchodilators have been identified: 1) selective phosphodiesterase inhibitors; 2) bitter-taste receptor agonists; 3) E-prostanoid receptor 4 agonists; 4) Rho kinase inhibitors; 5) calcilytics; 6) agonists of peroxisome proliferator-activated receptor-γ; 7) agonists of relaxin receptor 1; 8) soluble guanylyl cyclase activators; and 9) pepducins. They are under consideration, but they are mostly in a preclinical phase and, consequently, we still do not know which classes will actually be developed for clinical use and whether it will be proven that a possible clinical benefit outweighs the impact of any adverse effect.It is likely that if developed, these new classes may be a useful addition to, rather than a substitution of, the bronchodilator therapy currently used, in order to achieve further optimisation of bronchodilation.

Ensifentrine (RPL554): an investigational PDE3/4 inhibitor for the treatment of COPD

Introduction: A compound that simultaneously inhibits PDE3 and PDE4 should increase airway caliber by relaxing the smooth muscle and, simultaneously, suppress airway inflammatory responses. Ensifentrine (RPL554) is considered a PDE3/4 inhibitor, although its affinity for PDE3 is 3,440 times higher than that for PDE4, that is under clinical development for the treatment of asthma and COPD and, potentially, cystic fibrosis. Areas covered: We analyze the development of this molecule from its basic pharmacology to the present clinical Phase II studies. Expert opinion: Ensifentrine is an interesting drug but there is a lack of solid studies that still does not allow us to correctly allocate this molecule in the current COPD and even asthma therapeutic armamentarium. Furthermore, apparently ensifentrine has not yet entered Phase III clinical development and, in any case, there is no reliable evidence of its ability to elicit an anti-inflammatory activity in patients with COPD or asthma. Therefore, the real anti-inflammatory profile of ensifentrine must be clarified with new studies of basic pharmacology and adequate clinical studies specifically designed. However, at present the most intriguing perspective is linked to its possible use in the treatment of cystic fibrosis, also considering the lack of valid therapeutic options for this disease.

Efficacy and safety of a first-in-class inhaled PDE3/4 inhibitor (ensifentrine) vs salbutamol in asthma

INTRODUCTION

This study aimed to investigate the dose-response and pharmacology of a range of single doses of nebulised ensifentrine (RPL554), an inhaled dual phosphodiesterase (PDE) 3/4 inhibitor in patients with asthma.

METHODS

In this randomised, placebo-controlled, double-blind crossover study, patients received single nebulised doses of ensifentrine 0.4, 1.5, 6 and 24 mg, salbutamol 2.5 and 7.5 mg, and placebo. Eligible patients were adults with asthma, pre-bronchodilator forced expiratory volume in 1 s (FEV₁) 60-90% predicted and ≥1.5 L, with post-salbutamol FEV₁ increase ≥15%. The co-primary objectives were peak and average FEV₁ over 12 h for ensifentrine vs placebo and salbutamol. Secondary endpoints included: peak and average systolic and diastolic blood pressure, pulse rate and ECG heart rate; and safety and tolerability (adverse events [AEs], and serum potassium). ClinicalTrials.gov: NCT02427165.

RESULTS

A total of 29 patients were randomised, with 25 (89%) completing the study. For the two co-primary endpoints there was a clear ensifentrine dose-response relationship, with all treatments superior to placebo (p < 0.001). There was no relationship between the ensifentrine dose and AE incidence or blood pressure. Ensifentrine 0.4, 1.5 and 6 mg had significantly lower effects than both salbutamol doses on pulse and heart rates. Ensifentrine did not impact potassium, whereas there was a was a dose-related reduction for salbutamol. Inhalation of ensifentrine resulted in a dose-related increase in plasma exposure.

CONCLUSIONS

Single-dose ensifentrine demonstrated dose-dependent bronchodilation, and was as effective as a therapeutic dose of nebulised salbutamol. All ensifentrine doses were similarly well tolerated, and did not show the characteristic β₂-agonist systemic adverse effects.

Experimental and investigational phosphodiesterase inhibitors in development for asthma

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.