Treatment of Persistent Cough in Subjects with Idiopathic Pulmonary Fibrosis (IPF) with Gefapixant, a P2X3 Antagonist, in a Randomized, Placebo-Controlled Clinical Trial

Morphine for treatment of cough in idiopathic pulmonary fibrosis (PACIFY COUGH): a prospective, multicentre, randomised, double-blind, placebo-controlled, two-way crossover trial

BACKGROUND

Idiopathic pulmonary fibrosis is a progressive fibrotic lung disease, with most patients reporting cough. Currently, there are no proven treatments. We examined the use of low dose controlled-release morphine compared with placebo as an antitussive therapy in individuals with idiopathic pulmonary fibrosis.

METHODS

The PACIFY COUGH study is a phase 2, multicentre, randomised, double-blind, placebo-controlled, two-way crossover trial done in three specialist centres in the UK. Eligible patients aged 40-90 years had a diagnosis of idiopathic pulmonary fibrosis within 5 years, self-reported cough (lasting >8 weeks), and a cough visual analogue scale (VAS) score of 30 mm or higher. Patients were randomly assigned (1:1) to placebo twice daily or controlled-release morphine 5 mg orally twice daily for 14 days followed by crossover after a 7-day washout period. Patients were randomised sequentially to a sequence group defining the order in which morphine and placebo were to be given, according to a computer-generated schedule. Patients, investigators, study nurses, and pharmacy personnel were masked to treatment allocation. The primary endpoint was percentage change in objective awake cough frequency (coughs per h) from baseline as assessed by objective digital cough monitoring at day 14 of treatment in the intention-to-treat population, which included all randomised participants. Safety data were summarised for all patients who took at least one study drug and did not withdraw consent. This study was registered at ClinicalTrials.gov, NCT04429516, and has been completed.

FINDINGS

Between Dec 17, 2020, and March 21, 2023, 47 participants were assessed for eligibility and 44 were enrolled and randomly allocated to treatment. Mean age was 71 (SD 7·4) years, and 31 (70%) of 44 participants were male and 13 (30%) were female. Lung function was moderately impaired; mean forced vital capacity (FVC) was 2·7 L (SD 0·76), mean predicted FVC was 82% (17·3), and mean predicted diffusion capacity of carbon monoxide was 48% (10·9). Of the 44 patients who were randomised, 43 completed morphine treatment and 41 completed placebo treatment. In the intention-to-treat analysis, morphine reduced objective awake cough frequency by 39·4% (95% CI -54·4 to -19·4; p=0·0005) compared with placebo. Mean daytime cough frequency reduced from 21·6 (SE 1·2) coughs per h at baseline to 12·8 (1·2) coughs per h with morphine, whereas cough rates did not change with placebo (21·5 [SE 1·2] coughs per h to 20·6 [1·2] coughs per h). Overall treatment adherence was 98% in the morphine group and 98% in the placebo group. Adverse events were observed in 17 (40%) of 43 participants in the morphine group and six (14%) of 42 patients in the placebo group. The main side-effects of morphine were nausea (six [14%] of 43 participants) and constipation (nine [21%] of 43). One serious adverse event (death) occurred in the placebo group.

INTERPRETATION

In patients with cough related to idiopathic pulmonary fibrosis, low dose controlled-release morphine significantly reduced objective cough counts over 14 days compared with placebo. Morphine shows promise as an effective treatment to palliate cough in patients with idiopathic pulmonary fibrosis, and longer term studies should be the focus of future research.

FUNDING

The Jon Moulton Charity Trust.

Patients with idiopathic pulmonary fibrosis and refractory cough have traction bronchiectasis and distorted airway architecture: a retrospective case review study

Cough is a common and important sign/symptom in patients with idiopathic pulmonary fibrosis (IPF). However, there have been few reports focusing on cough, and the exact mechanisms for cough in patients with IPF have remained unclear. The objective of this study was to investigate the clinical features of IPF patients with refractory cough and to clarify mechanisms for cough in these patients. We retrospectively reviewed the files of patients with the diagnosis of IPF at Kanazawa University Hospital and compared the clinical features of IPF patients with refractory cough with the clinical features of IPF patients without refractory cough. Among a total of 23 patients with IPF, 10 patients (43.5%) had chronic cough. Of the ten patients, seven patients had concomitant conditions that could lead to cough. Of these seven patients, the cough of four patients was resolved after treatment of their concomitant condition. Finally, among the 23 patients there were 6 (26.1%) with refractory cough associated with IPF. Significant differences were seen between the following clinical features of IPF patients with or without refractory cough, respectively, as follows: lower body mass index (BMI; 18.8±2.5 vs. 22.8±2.5 kg/m2, P<0.01), lower forced vital capacity (FVC; 77.5%±30.4% predicted vs. 99.9%±0.53% predicted, P=0.046), and presence of traction bronchiectasis and distorted airway architecture on high-resolution computed tomography (HRCT; 83.3% vs. 11.8%, P<0.01). The difference between the proportions of patients with or without refractory cough with capsaicin cough sensitivity was not significant. Mechanical stress on the airways due to traction bronchiectasis and distorted airway architecture is a possible mechanism for cough in IPF patients.

The Therapeutic Landscape in Chronic Cough

In recent years, there has been a substantial increase in the development of antitussive therapies and the first new therapy, gefapixant has been licenced in Europe. This review describes current unlicenced treatments for chronic cough and details treatments currently in development for refractory chronic cough and cough in idiopathic pulmonary fibrosis, as well as compounds previously explored.

Molecular insights into P2X signalling cascades in acute kidney injury

Acute kidney injury (AKI) is a critical health issue with high mortality and morbidity rates in hospitalized individuals. The complex pathophysiology and underlying health conditions further complicate AKI management. Growing evidence suggests the pivotal role of ion channels in AKI progression, through promoting tubular cell death and altering immune cell functions. Among these channels, P2X purinergic receptors emerge as key players in AKI pathophysiology. P2X receptors gated by adenosine triphosphate (ATP), exhibit increased extracellular levels of ATP during AKI episodes. More importantly, certain P2X receptor subtypes upon activation exacerbate the situation by promoting the release of extracellular ATP. While therapeutic investigations have primarily focused on P2X4 and P2X7 subtypes in the context of AKI, while understanding about other subtypes still remains limited. Whilst some P2X antagonists show promising results against different types of kidney diseases, their role in managing AKI remains unexplored. Henceforth, understanding the intricate interplay between P2X receptors and AKI is crucial for developing targeted interventions. This review elucidates the functional alterations of all P2X receptors during normal kidney function and AKI, offering insights into their involvement in AKI. Notably, we have highlighted the current knowledge of P2X receptor antagonists and the possibilities to use them against AKI in the future. Furthermore, the review delves into the pathways influenced by activated P2X receptors during AKI, presenting potential targets for future therapeutic interventions against this critical condition.

Assessment and Management of Cough in Idiopathic Pulmonary Fibrosis: A Narrative Review

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal disease with an unknown cause. It is characterized by symptoms such as cough and breathlessness, which significantly impact patients' quality of life. Cough, in particular, has emerged as a burdensome symptom for individuals with IPF. The etiology of cough in IPF patients is believed to be complex, involving factors related to the disease itself, such as increased sensitivity of cough nerves, lung structural changes, inflammation, and genetic factors, as well as comorbidities and medication effects. Unfortunately, effective treatment options for cough in IPF remain limited, often relying on empirical approaches based on studies involving chronic cough patients in general and the personal experience of physicians. Medications such as opioids and neuromodulators are commonly prescribed but have shown suboptimal efficacy, imposing significant physical, psychological, and economic burdens on patients. However, there is hope on the horizon, as specific purinergic P2 receptor ligand-gated ion channel (P2X3) inhibitors have demonstrated promising antitussive effects in ongoing clinical trials. This review aims to provide a comprehensive overview of the evaluation and management of cough in IPF patients, as well as highlight emerging pharmacological and non-pharmacological approaches that target the cough reflex and are currently being investigated in clinical settings.

Safety and efficacy of P2X3 receptor antagonist for the treatment of refractory or unexplained chronic cough: A systematic review and meta-analysis of 11 randomized controlled trials

BACKGROUND AND OBJECTIVES

Chronic refractory cough is a challenging condition that requires a thorough evaluation and management approach. P2X3 receptors that are ATP-dependent play an important part in nerve fiber sensitization and pathological pain pathways. We conducted this systematic review and meta-analysis to determine the long-term safety and efficacy of P2X3 receptor antagonist drugs in chronic cough.

METHODS

We systematically searched PubMed, Scopus, Web of Science, and Embase to identify all relevant published studies through January 15, 2023 that assessed P2X3 antagonists in chronic cough. The protocol was registered in the PROSPERO database with ID: CRD42023422408. Efficacy outcomes were awake (daytime) cough frequency, night cough frequency, 24-h cough frequency, Cough Severity Diary, and total Leicester Cough Questionnaire score. We used the random-effect model to pool the data using RStudio and CMA software.

RESULTS

A total of 11 randomized controlled trials comprising 1350 patients receiving a p2x3 antagonist compared to the placebo group were included in this meta-analysis. A significant decrease in 24-h cough frequency (MD = -4.99, 95% CI [-7.15 to -2.82], P < 0.01), awake (daytime) cough frequency (MD = -7.18, 95% CI [-9.98 to 4.37], P < 0.01), and total Leicester Cough Questionnaire score (MD = 1.74, 95% CI [1.02 to 2.46], P < 0.01) exhibited between the P2X3 antagonist and placebo groups. The frequency of the night cough showed an insignificant difference between the two groups. According to the safety, drug-related adverse events, dysgeusia, hypogeusia, and ageusia significantly increased between the P2X3 antagonist and placebo groups.

CONCLUSION

P2X3 receptor antagonists are promising drugs for treating chronic cough by significantly reducing the frequency, severity, and quality. Some potential side effects may include drug-related adverse events such as hypogeusia, ageusia, and dysgeusia.

Mechanisms and management of cough in interstitial lung disease

INTRODUCTION

Many patients with interstitial lung diseases (ILDs), especially fibrotic ILDs, experience chronic cough. It negatively impacts both physical and psychological well-being. Effective treatment options are limited.

AREAS COVERED

The pathophysiology of chronic cough in IPF is complex and involves multiple mechanisms, including mechanical distortion of airways, parenchyma, and nerve fibers. The pathophysiology of cough in other fibrosing ILDs is poorly understood and involves various pathways. The purpose of this review is to highlight mechanisms of chronic cough and to present therapeutic evidence for its management in the most commonly occurring diffuse fibrosing lung diseases including idiopathic pulmonary fibrosis (IPF), connective tissue disease-related interstitial lung disease (CTD-ILD), sarcoidosis-related ILD (Sc-ILD), chronic hypersensitivity pneumonitis-related ILD (CHP-ILD), and post-COVID-19-related interstitial lung disease (PC-ILD).

EXPERT OPINION

This review guides the management of chronic cough in fibrosing ILDs. In this era of precision medicine, chronic cough management should be individualized in each interstitial lung disease.

Cough in chronic lung disease: a state of the art review

Chronic cough (CC; ≥8 weeks in duration) is a common and burdensome feature of respiratory diseases. The understanding of cough has progressed significantly in recent years, albeit largely in refractory (unexplained) chronic cough (RCC) in the absence of other respiratory conditions. The prevalence of CC in respiratory diseases is poorly described, but estimates have been reported: asthma (8-58%), chronic obstructive pulmonary disease (COPD; 10-74%), bronchiectasis (82-98%), interstitial lung disease (ILD; 50-89%) and sarcoidosis (3-64%). CC in respiratory conditions generally predicts impaired health status and more severe disease. It is associated with increased symptom burden and disease severity in asthma, COPD, bronchiectasis and ILD, higher exacerbation frequency in asthma and bronchiectasis, and increased mortality and lung transplantation in idiopathic pulmonary fibrosis (IPF). Physiologically, heightened cough reflex sensitivity (CRS) has been reported and postulated to be mechanistic in isolated RCC. Cough reflex hypersensitivity (CRH) has also been reported in asthma, COPD, bronchiectasis, ILD and sarcoidosis. Unlike recent advances in isolated RCC, there are limited studies and understanding of central cough neuropathways in other respiratory conditions. Of note, dysfunctional central voluntary cough suppression neuropathways and physiology were observed in isolation in RCC; cough suppression is preserved in COPD. Understanding in the mechanism of RCC cannot be simply extrapolated to other respiratory conditions. The restricted understanding of cough mechanisms in these conditions has limited cough-specific therapeutic options in this context. There is currently an unmet need to expand our understanding of cough in chronic respiratory conditions, both in order to improve the quality of life of patients, and to improve knowledge of cough in general. This review aims to describe the prevalence, impact, pathophysiology and management of CC in asthma, COPD, bronchiectasis, ILD and sarcoidosis.

Adenosine receptor signalling as a driver of pulmonary fibrosis

Pulmonary fibrosis is a debilitating and life-limiting lung condition in which the damage- response mechanisms of mixed-population cells within the lungs go awry. The tissue microenvironment is drastically remodelled by aberrantly activated fibroblasts which deposit ECM components into the surrounding lung tissue, detrimentally affecting lung function and capacity for gas exchange. Growing evidence suggests a role for adenosine signalling in the pathology of tissue fibrosis in a variety of organs, including the lung, but the molecular pathways through which this occurs remain largely unknown. This review explores the role of adenosine in fibrosis and evaluates the contribution of the different adenosine receptors to fibrogenesis. Therapeutic targeting of the adenosine receptors is also considered, along with clinical observations pointing towards a role for adenosine in fibrosis. In addition, the interaction between adenosine signalling and other profibrotic signalling pathways, such as TGFβ1 signalling, is discussed.

The Burden and Impact of Cough in Patients with Idiopathic Pulmonary Fibrosis: An Analysis of the Prospective Observational PROFILE Study

Rationale: Cough is a commonly reported symptom in idiopathic pulmonary fibrosis (IPF) that negatively impacts patient-reported quality of life (QoL). However, both the burden of cough at diagnosis and the behavior of cough over time have not been systematically described in patients with IPF. Objectives: By utilizing data prospectively collected as part of the PROFILE study, we sought to assess cough burden and the impact that this has on QoL within a cohort of patients with newly diagnosed IPF. We also reexamined the previously described relationship between cough and mortality and the association of cough with the MUC5B promoter polymorphism. Methods: The PROFILE study is a multicenter, prospective, observational, longitudinal cohort study of incident IPF. Scores on the Leicester Cough Questionnaire (LCQ) were recorded at baseline in 632 subjects and then repeated 6 monthly in a subset (n = 216) of the cohort. Results: The median LCQ score at diagnosis was 16.1 (interquartile range, 6.5). LCQ scores remained stable over the subsequent year in the majority of patients. There was a weak association between LCQ score and baseline lung function, with worse cough-related QoL associated with more severe physiological impairment. Cough scores were not associated with subsequent mortality after correcting for baseline lung function. Furthermore, there was no relationship between LCQ score and MUC5B promoter polymorphism status. Conclusions: The burden of cough in IPF is high. Although cough is weakly associated with disease severity at baseline, cough-specific QoL, as measured by the LCQ, confers no prognostic value. Cough-specific QoL burden remains relatively stable over time and does not associate with MUC5B promoter polymorphism.

Efficacy and safety of gefapixant for chronic cough: a meta-analysis of randomised controlled trials

BACKGROUND

The efficacy and safety of gefapixant in adults with chronic cough remain unclear. Our objective was to assess the efficacy and safety of gefapixant using updated evidence.

METHODS

MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL) and Embase databases were searched from inception through September 2022. Subgroup analysis based on dose of gefapixant (i.e. ≤20, 45-50 and ≥100 mg twice daily for low, moderate and high doses, respectively) was performed to explore a potential dose-dependent effect.

RESULTS

Five studies involving seven trials showed the efficacy of moderate- or high-dose gefapixant for reducing objective 24-h cough frequency (estimated relative reduction 30.9% and 58.5%, respectively) (i.e. primary outcome) and awake cough frequency (estimated relative reduction 47.3% and 62.8%, respectively). Night-time cough frequency was only reduced with high-dose gefapixant. Consistently, the use of moderate- or high-dose gefapixant significantly alleviated cough severity and improved cough-related quality of life, but increased the risk of all-cause adverse events (AEs), treatment-related AEs and ageusia/dysgeusia/hypogeusia. Subgroup analysis showed dose dependency in both efficacy and AEs with a cut-off dose being ≥45 mg twice daily.

CONCLUSIONS

This meta-analysis revealed dose-dependent efficacy and adverse effects of gefapixant against chronic cough. Further studies are required to investigate the feasibility of moderate-dose (i.e. 45-50 mg twice daily) gefapixant in clinical practice.

An update on current and emerging drug treatments for idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic Pulmonary Fibrosis (IPF) is a progressive and devastating lung disease, characterized by progressive lung scarring.

AREAS COVERED

Prior to antifibrotic therapy (pirfenidone and nintedanib), there was no validated pharmaceutical therapy for IPF. Both antifibrotics can slow disease progression, however, IPF remains a detrimental disease with poor prognosis and treated survival rates of less than 7 years from diagnosis. Despite their effect the disease remains non-reversible and progressing whilst their side effect profile is often challenging. Treatment of comorbidities is also crucial. In this review, we discuss the current pharmacological management as well as management of comorbidities and symptoms. We also reviewed clinicaltrials.gov and summarised all the mid to late stage clinical trials (phase II and III) registered in IPF over the last 7 years and discuss the most promising drugs in clinical development.

EXPERT OPINION

Future for IPF management will need to focus on current unresolved issues. First a primary pathogenetic pathway has not been clearly identified. Future management may involve a combination of brushstroke approach with antifibrotics with targeted treatments for specific pathways in patient subsets following an 'oncological' approach. Another unmet need is management of exacerbations, which are deathly in most cases as well as either treating or preventing lung cancer.

Emerging drugs in the treatment of chronic cough

INTRODUCTION

Chronic cough is a debilitating condition that is among the most common reasons for seeking medical attention yet remains challenging to manage. Identifying an underlying respiratory, nasal or upper gastrointestinal disease triggering cough is the first step in assessment, but once this has been ruled out or adequately treated, many patients remain troubled with chronic cough.

AREAS COVERED

This narrative review discusses the role of existing treatments and describes the current research landscape for the development of new therapies for chronic cough greater than 8 weeks that is refractory (RCC) or unexplained (UCC). The literature search includes published studies found on pubmed and conference abstracts until 2023.

EXPERT OPINION

RCC/UCC can occur due to neuronal dysregulation of the vagus nerve or central nervous system. Hence, novel anti-tussives have targeted ion channels involved in the neuronal signaling which triggers cough. Although some therapies targeting receptors such as TRPV1 have failed to show efficacy, P2X3 antagonists have emerged as the most promising therapy for patients impacted by chronic cough. Disease specific therapies such as for idiopathic pulmonary fibrosis are in early development.

The developmental journey of therapies targeting purine receptors: from basic science to clinical trials

Since the discovery of ATP as an extracellular signalling molecule in 1972, purinergic signalling, mediated by extracellular purines and pyrimidines has been identified in virtually all mammalian tissues and is implicated in regulating fundamental cellular processes. In recent years, there has been an increasing focus on the pathophysiology and potential therapeutic interventions based on purinergic signalling. A vast range of compounds targeting purine receptors are in clinical development, and many more are in preclinical studies, which highlights the fast growth in this research field. As a tribute to Professor Geoffrey Burnstock's legacy in purinergic signalling, we present here a brief review of compounds targeting purine receptors that are in different stages of clinical trials. The review highlights the 50-year journey from basic research on purinergic receptors to clinical applications of therapies targeting purine receptors.

[French practical guidelines for the diagnosis and management of IPF - 2021 update, full version]

BACKGROUND

Since the previous French guidelines were published in 2017, substantial additional knowledge about idiopathic pulmonary fibrosis has accumulated.

METHODS

Under the auspices of the French-speaking Learned Society of Pulmonology and at the initiative of the coordinating reference center, practical guidelines for treatment of rare pulmonary diseases have been established. They were elaborated by groups of writers, reviewers and coordinators with the help of the OrphaLung network, as well as pulmonologists with varying practice modalities, radiologists, pathologists, a general practitioner, a head nurse, and a patients' association. The method was developed according to rules entitled "Good clinical practice" in the overall framework of the "Guidelines for clinical practice" of the official French health authority (HAS), taking into account the results of an online vote using a Likert scale.

RESULTS

After analysis of the literature, 54 recommendations were formulated, improved, and validated by the working groups. The recommendations covered a wide-ranging aspects of the disease and its treatment: epidemiology, diagnostic modalities, quality criteria and interpretation of chest CT, indication and modalities of lung biopsy, etiologic workup, approach to familial disease entailing indications and modalities of genetic testing, evaluation of possible functional impairments and prognosis, indications for and use of antifibrotic therapy, lung transplantation, symptom management, comorbidities and complications, treatment of chronic respiratory failure, diagnosis and management of acute exacerbations of fibrosis.

CONCLUSION

These evidence-based guidelines are aimed at guiding the diagnosis and the management in clinical practice of idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is defined as a chronic progressive fibrosing interstitial pneumonia of unknown etiology. There are intrinsic and extrinsic risk factors that could favor the development of the disease in individuals with a genetic predisposition. The diagnosis is made by characteristic radiological and/or histological findings on high-resolution computed tomography and lung biopsy, respectively, in the absence of a specific identifiable cause. The median survival of the disease for patients without treatment is 3-5years from the onset of symptoms, although its natural history is variable and unpredictable. Currently, there are two antifibrotic drugs that reduce disease progression. The multidisciplinary approach will consider the nutritional and emotional status, physical conditioning, and treatment of comorbidities, as well as lung transplantation and palliative care in advanced stages. The following article reviews the fundamental aspects for the diagnosis and treatment of idiopathic pulmonary fibrosis.

French practical guidelines for the diagnosis and management of idiopathic pulmonary fibrosis - 2021 update. Full-length version

BACKGROUND

Since the latest 2017 French guidelines, knowledge about idiopathic pulmonary fibrosis has evolved considerably.

METHODS

Practical guidelines were drafted on the initiative of the Coordinating Reference Center for Rare Pulmonary Diseases, led by the French Language Pulmonology Society (SPLF), by a coordinating group, a writing group, and a review group, with the involvement of the entire OrphaLung network, pulmonologists practicing in various settings, radiologists, pathologists, a general practitioner, a health manager, and a patient association. The method followed the "Clinical Practice Guidelines" process of the French National Authority for Health (HAS), including an online vote using a Likert scale.

RESULTS

After a literature review, 54 guidelines were formulated, improved, and then validated by the working groups. These guidelines addressed multiple aspects of the disease: epidemiology, diagnostic procedures, quality criteria and interpretation of chest CT scans, lung biopsy indication and procedures, etiological workup, methods and indications for family screening and genetic testing, assessment of the functional impairment and prognosis, indication and use of antifibrotic agents, lung transplantation, management of symptoms, comorbidities and complications, treatment of chronic respiratory failure, diagnosis and management of acute exacerbations of fibrosis.

CONCLUSION

These evidence-based guidelines are intended to guide the diagnosis and practical management of idiopathic pulmonary fibrosis.

ATP, an attractive target for the treatment of refractory chronic cough

Chronic cough is the most common complaint in respiratory clinics. Most of them have identifiable causes and some may respond to common disease-modifying therapies. However, there are many patients whose cough lacks effective aetiologically targeted treatments or remains unexplained after thorough assessments, which have been described as refractory chronic cough. Current treatments for refractory chronic cough are limited and often accompanied by intolerable side effects such as sedation. In recent years, various in-depth researches into the pathogenesis of chronic cough have led to an explosion in the development of drugs for the treatment of refractory chronic cough. There has been considerable progress in the underlying mechanisms of chronic cough targeting ATP, and ongoing or completed clinical studies have confirmed the promising antitussive efficacy of P2X3 antagonists for refractory cough. Herein, we review the foundation on which ATP target was developed as potential antitussive medications and provide an update on current clinical progresses.

Contemporary Concise Review 2021: Interstitial lung disease

The last 2 years have presented previously unforeseen challenges in pulmonary medicine. Despite the significant impact of the SARS‐CoV‐2 pandemic on patients, clinicians and communities, advances in the care and understanding of interstitial lung disease (ILD) continued unabated. Recent studies have led to improved guidelines, better understanding of the role for antifibrotics in fibrosing ILDs, prognostic indicators and novel biomarkers. In this concise contemporary review, we summarize many of the important studies published in 2021, highlighting their relevance and impact to the management and knowledge of ILD.