TOLLIP, MUC5B, and the Response to N-Acetylcysteine among Individuals with Idiopathic Pulmonary Fibrosis

An Official American Thoracic Society Workshop Report: Translational Research in Rare Respiratory Diseases

Rare respiratory diseases (RRDs) are a heterogeneous group of disorders that collectively represent a significant health care burden. In recent years, strong advocacy and policy initiatives have led to advances in the implementation of research and clinical care for rare diseases. The development of specialized centers and research networks has facilitated support for affected individuals as well as emerging programs in basic, translational, and clinical research. In selected RRDs, subsequent gains in knowledge have informed the development of targeted therapies and effective diagnostic tests, but many gaps persist. There was therefore a desire to identify the elements contributing to an effective translational research program in RRDs. To this end, a workshop was convened in October 2015 with a focus on the implementation of effective transnational research networks and collaborations aimed at developing novel diagnostic and therapeutic tools. Key elements included an emphasis on molecular pathogenesis, the continuing engagement of patient advocacy groups and policy makers, the effective use of preclinical models in the translational research pipeline, and the detailed phenotyping of patient cohorts. During the course of the workshop, current logistical and knowledge gaps were identified, and new solutions or opportunities were highlighted.

Microbes Are Associated with Host Innate Immune Response in Idiopathic Pulmonary Fibrosis

RATIONALE

Differences in the lung microbial community influence idiopathic pulmonary fibrosis (IPF) progression. Whether the lung microbiome influences IPF host defense remains unknown.

OBJECTIVES

To explore the host immune response and microbial interaction in IPF as they relate to progression-free survival (PFS), fibroblast function, and leukocyte phenotypes.

METHODS

Paired microarray gene expression data derived from peripheral blood mononuclear cells as well as 16S ribosomal RNA sequencing data from bronchoalveolar lavage obtained as part of the COMET-IPF (Correlating Outcomes with Biochemical Markers to Estimate Time-Progression in Idiopathic Pulmonary Fibrosis) study were used to conduct association pathway analyses. The responsiveness of paired lung fibroblasts to Toll-like receptor 9 (TLR9) stimulation by CpG-oligodeoxynucleotide (CpG-ODN) was integrated into microbiome-gene expression association analyses for a subset of individuals. The relationship between associated pathways and circulating leukocyte phenotypes was explored by flow cytometry.

MEASUREMENTS AND MAIN RESULTS

Down-regulation of immune response pathways, including nucleotide-binding oligomerization domain (NOD)-, Toll-, and RIG1-like receptor pathways, was associated with worse PFS. Ten of the 11 PFS-associated pathways correlated with microbial diversity and individual genus, with species accumulation curve richness as a hub. Higher species accumulation curve richness was significantly associated with inhibition of NODs and TLRs, whereas increased abundance of Streptococcus correlated with increased NOD-like receptor signaling. In a network analysis, expression of up-regulated signaling pathways was strongly associated with decreased abundance of operational taxonomic unit 1341 (OTU1341; Prevotella) among individuals with fibroblasts responsive to CpG-ODN stimulation. The expression of TLR signaling pathways was also linked to CpG-ODN responsive fibroblasts, OTU1341 (Prevotella), and Shannon index of microbial diversity in a network analysis. Lymphocytes expressing C-X-C chemokine receptor 3 CD8 significantly correlated with OTU1348 (Staphylococcus).

CONCLUSIONS

These findings suggest that host-microbiome interactions influence PFS and fibroblast responsiveness.

Idiopathic pulmonary fibrosis in the era of antifibrotic therapy: Searching for new opportunities grounded in evidence

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease that up to now has been associated with a poor prognosis. However, the results of the INPULSIS and ASCEND trials and the approval of nintedanib and pirfenidone have marked the beginning of a new era for IPF patients. Questions remain, however. Should these drugs be used earlier? What effect will they have on more severe disease? Will their effects last beyond the trial period? This manuscript is the outcome of a multidisciplinary meeting between pulmonology, radiology, and pathology clinicians on the use of antifibrotic agents in IPF. In our opinion, the existing data show that pirfenidone and nintedanib slow functional decline in early stages of disease. These drugs also appear to result in therapeutic benefits when administered to patients with advanced disease at diagnosis and maintain effective over time. The data also suggest that continuing antifibrotic therapy after disease progression may confer benefits, but more evidence is needed. Early diagnosis and treatment are crucial for reducing functional decline, slowing disease progression, and improving quality of life.

[Idiopatic pulmonary fibrosis: A new paradigm]

Idiopathic pulmonary fibrosis ((IPF) is the most common disease from a group of interstitial lung diseases, which occurs mainly in middle-aged and elderly people. Over the past decade, there have been considerable changes in approaches to diagnosing and treating IPF. The paper presents an update on the epidemiology of IPF, the results of new studies of its pathogenesis, and main approaches to diagnosing the disease. In addition, there is new evidence on therapy for IPF.

Precision Medicine: The New Frontier in Idiopathic Pulmonary Fibrosis

Precision medicine is defined by the National Institute of Health's Precision Medicine Initiative Working Group as an approach to disease treatment that takes into account individual variability in genes, environment, and lifestyle. There has been increased interest in applying the concept of precision medicine to idiopathic pulmonary fibrosis, in particular to search for genetic and molecular biomarker-based profiles (so called endotypes) that identify mechanistically distinct disease subgroups. The relevance of precision medicine to idiopathic pulmonary fibrosis is yet to be established, but we believe that it holds great promise to provide targeted and highly effective therapies to patients. In this manuscript, we describe the field's nascent efforts in genetic/molecular endotype identification and how environmental and behavioral subgroups may also be relevant to disease management.

Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is a prototype of chronic, progressive, and fibrotic lung disease. Healthy tissue is replaced by altered extracellular matrix and alveolar architecture is destroyed, which leads to decreased lung compliance, disrupted gas exchange, and ultimately respiratory failure and death. In less than a decade, understanding of the pathogenesis and management of this disease has been transformed, and two disease-modifying therapies have been approved, worldwide. In this Seminar, we summarise the presentation, pathophysiology, diagnosis, and treatment options available for patients with idiopathic pulmonary fibrosis. This disease has improved understanding of the mechanisms of lung fibrosis, and offers hope that similar approaches will transform the management of patients with other progressive fibrotic lung diseases.

Toll-Interacting Protein in Resolving and Non-Resolving Inflammation

Innate leukocytes manifest dynamic and distinct inflammatory responses upon challenges with rising dosages of pathogen-associated molecular pattern molecules such as lipopolysaccharide (LPS). To differentiate signal strengths, innate leukocytes may utilize distinct intracellular signaling circuitries modulated by adaptor molecules. Toll-interacting protein (Tollip) is one of the critical adaptor molecules potentially playing key roles in modulating the dynamic adaptation of innate leukocytes to varying dosages of external stimulants. While Tollip may serve as a negative regulator of nuclear factor κ of activated B cells signaling pathway in cells challenged with higher dosages of LPS, it acts as a positive regulator for low-grade chronic inflammation in leukocytes programmed by subclinical low-dosages of LPS. This review aims to discuss recent progress in our understanding of complex innate leukocyte dynamics and its relevance in the pathogenesis of resolving versus non-resolving chronic inflammatory diseases.

Management of suspected monogenic lung fibrosis in a specialised centre

At least 10% of patients with interstitial lung disease present monogenic lung fibrosis suspected on familial aggregation of pulmonary fibrosis, specific syndromes or early age of diagnosis. Approximately 25% of families have an identified mutation in genes mostly involved in telomere homeostasis, and more rarely in surfactant homeostasis.

Beyond pathophysiological knowledge, detection of these mutations has practical consequence for patients. For instance, mutations involved in telomere homeostasis are associated with haematological complications after lung transplantation and may require adapted immunosuppression. Moreover, relatives may benefit from a clinical and genetic evaluation that should be specifically managed.

The field of genetics of pulmonary fibrosis has made great progress in the last 10 years, raising specific problems that should be addressed by a specialised team.

Pulmonary fibrosis, part II: state-of-the-art patient management

INTRODUCTION

While many pharmacologic therapies for the treatment of idiopathic pulmonary fibrosis (IPF) have been evaluated via randomized, placebo-controlled clinical trials (RCTs) conducted over the past two decades, most therapies have been shown to be ineffective or even potentially harmful. However, a number of recently completed RCTs have shown significant efficacy for pirfenidone and nintedanib for the treatment of IPF. Areas covered: This manuscript reviews recent advances in the management of IPF and other forms of fibrosing interstitial lung disease (ILD) with an emphasis on IPF. The material upon which this discussion is based was obtained from various published texts and manuscripts identified via literature searching (e.g. PubMed). Expert commentary: Anti-fibrotic drugs are now available for clinical use and perceived as standard-of-care therapies that have the potential to blunt disease progression for many patients with IPF. However, these agents do not necessarily stop disease progression or have a significant impact on mortality, and more effective pharmacologic therapies are needed for patients with IPF. Additionally, whether anti-fibrotic agents can be effective therapies for other forms of pulmonary fibrosis, which often have radiologic and histopathologic manifestations that mimic IPF, is being evaluated in a number of RCTs.

Update in diagnosis and management of interstitial lung disease

The field of interstitial lung disease (ILD) has undergone significant evolution in recent years, with an increasing incidence and more complex, ever expanding disease classification. In their most severe forms, these diseases lead to progressive loss of lung function, respiratory failure and eventually death. Despite notable advances, progress has been challenged by a poor understanding of pathological mechanisms and patient heterogeneity, including variable progression. The diagnostic pathway is thus being continually refined, with the introduction of tools such as transbronchial cryo lung biopsy and a move towards genetically aided, precision medicine. In this review, we focus on how to approach a patient with ILD and the diagnostic process.

Treatment of idiopathic pulmonary fibrosis: a position paper from a Nordic expert group

Idiopathic pulmonary fibrosis (IPF) is a fatal progressive lung disease occurring in adults. In the last decade, the results of a number of clinical trials based on the updated disease classification have been published. The registration of pirfenidone and nintedanib, the first two pharmacological treatment options approved for IPF, marks a new chapter in the management of patients with this disease. Other nonpharmacological treatments such as lung transplantation, rehabilitation and palliation have also been shown to be beneficial for these patients. In this review, past and present management is discussed based on a comprehensive literature search. A treatment algorithm is presented based on available evidence and our overall clinical experience. In addition, unmet needs with regard to treatment are highlighted and discussed. We describe the development of various treatment options for IPF from the first consensus to recent guidelines based on evidence from large-scale, multinational, randomized clinical trials, which have led to registration of the first drugs for IPF.

Tissue remodelling in pulmonary fibrosis

Many lung diseases result in fibrotic remodelling. Fibrotic lung disorders can be divided into diseases with known and unknown aetiology. Among those with unknown aetiology, idiopathic pulmonary fibrosis (IPF) is a common diagnosis. Because of its progressive character leading to a rapid decline in lung function, it is a fatal disease with poor prognosis and limited therapeutic options. Thus, IPF has motivated many studies in the last few decades in order to increase our mechanistic understanding of the pathogenesis of the disease. The current concept suggests an ongoing injury of the alveolar epithelium, an impaired regeneration capacity, alveolar collapse and, finally, a fibroproliferative response. The origin of lung injury remains elusive but a diversity of factors, which will be discussed in this article, has been shown to be associated with IPF. Alveolar epithelial type II (AE2) cells play a key role in lung fibrosis and their crucial role for epithelial regeneration, stabilisation of alveoli and interaction with fibroblasts, all known to be responsible for collagen deposition, will be illustrated. Whereas mechanisms of collagen deposition and fibroproliferation are the focus of many studies in the field, the awareness of other mechanisms in this disease is currently limited to biochemical and imaging studies including quantitative assessments of lung structure in IPF and animal models assigning alveolar collapse and collapse induration crucial roles for the degradation of the lung resulting in de-aeration and loss of surface area. Dysfunctional AE2 cells, instable alveoli and mechanical stress trigger remodelling that consists of collapsed alveoli absorbed by fibrotic tissue (i.e., collapse induration).

Update in diagnosis and management of interstitial lung disease

The field of interstitial lung disease (ILD) has undergone significant evolution in recent years, with an increasing incidence and more complex, ever expanding disease classification. In their most severe forms, these diseases lead to progressive loss of lung function, respiratory failure and eventually death. Despite notable advances, progress has been challenged by a poor understanding of pathological mechanisms and patient heterogeneity, including variable progression. The diagnostic pathway is thus being continually refined, with the introduction of tools such as transbronchial cryo lung biopsy and a move towards genetically aided, precision medicine. In this review, we focus on how to approach a patient with ILD and the diagnostic process.

Update in diagnosis and management of interstitial lung disease

The field of interstitial lung disease (ILD) has undergone significant evolution in recent years, with an increasing incidence and more complex, ever expanding disease classification. In their most severe forms, these diseases lead to progressive loss of lung function, respiratory failure and eventually death. Despite notable advances, progress has been challenged by a poor understanding of pathological mechanisms and patient heterogeneity, including variable progression. The diagnostic pathway is thus being continually refined, with the introduction of tools such as transbronchial cryo lung biopsy and a move towards genetically aided, precision medicine. In this review, we focus on how to approach a patient with ILD and the diagnostic process.

Toll-like receptor 4 activation attenuates profibrotic response in control lung fibroblasts but not in fibroblasts from patients with IPF

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with a median survival of 3 yr. IPF deteriorates upon viral or bacterial lung infection although pulmonary infection (pneumonia) in healthy lungs rarely induces fibrosis. Bacterial lipopolysaccharide (LPS) activates Toll-like receptor 4 (TLR4), initiating proinflammatory pathways. As TLR4 has already been linked to hepatic fibrosis and scleroderma, we now investigated the role of TLR4 in IPF fibroblasts. Lung tissue sections from patients with IPF were analyzed for TLR4 expression. Isolated normal human lung fibroblasts (NL-FB) and IPF fibroblasts (IPF-FB) were exposed to LPS and transforming growth factor-β (TGF-β) before expression analysis of receptors, profibrotic mediators, and cytokines. TLR4 is expressed in fibroblast foci of IPF lungs as well as in primary NL-FB and IPF-FB. As a model for a gram-negative pneumonia in the nonfibrotic lung, NL-FB and IPF-FB were coexposed to LPS and TGF-β. Whereas NL-FB produced significantly less connective tissue growth factor upon costimulation compared with TGF-β stimulation alone, IPF-FB showed significantly increased profibrotic markers compared with control fibroblasts after costimulation. Although levels of antifibrotic prostaglandin E2 were elevated after costimulation, they were not responsible for this effect. However, significant downregulation of TGF-β receptor type 1 in control fibroblasts seems to contribute to the reduced profibrotic response in our in vitro model. Normal and IPF fibroblasts thus differ in their profibrotic response upon LPS-induced TLR4 stimulation.

Pulmonary fibrosis in the era of stratified medicine

Both common and rare variants contribute to the genetic architecture of pulmonary fibrosis. Genome-wide association studies have identified common variants, or those with a minor allele frequency of >5%, that are linked to pulmonary fibrosis. The most widely replicated variant (rs35705950) is located in the promoter region of the MUC5B gene and has been strongly associated with idiopathic pulmonary fibrosis (IPF) and familial interstitial pneumonia (FIP) across multiple different cohorts. However, many more common variants have been identified with disease risk and in aggregate account for approximately one-third of the risk of IPF. Moreover, several of these common variants appear to have prognostic potential. Next generation sequencing technologies have facilitated the identification of rare variants. Recent whole exome sequencing studies have linked pathogenic rare variants in multiple new genes to FIP. Compared with common variants, rare variants have lower population allele frequencies and higher effect sizes. Pulmonary fibrosis rare variants genes can be subdivided into two pathways: telomere maintenance and surfactant metabolism. Heterozygous rare variants in telomere-related genes co-segregate with adult-onset pulmonary fibrosis with incomplete penetrance, lead to reduced protein function, and are associated with short telomere lengths. Despite poor genotype-phenotype correlations, lung fibrosis associated with pathogenic rare variants in different telomere genes is progressive and displays similar survival characteristics. In contrast, many of the heterozygous rare variants in the surfactant genes predict a gain of toxic function from protein misfolding and increased endoplasmic reticulum (ER) stress. Evidence of both telomere shortening and increased ER stress have been found in sporadic IPF patients, suggesting that the mechanisms identified from rare variant genetic studies in unique individuals and families are applicable to a wider spectrum of patients. The ability to sequence large cohorts of individuals rapidly has the potential to further our understanding of the relative contributions of common and rare variants in the pathogenesis of pulmonary fibrosis. The UK 100,000 Genomes Project will provide opportunities to interrogate both common and rare variants and to investigate how these biological signals provide diagnostic and prognostic information in the era of stratified medicine.

Toll-like receptors in the pathogenesis of pulmonary fibrosis

Pulmonary fibrosis (PF) constitutes the end stage of a broad range of heterogeneous interstitial lung diseases, characterized by the destruction of the pulmonary parenchyma, deposition of extracellular matrix and dramatic changes in the phenotype of both fibroblasts and alveolar epithelial cells. More than 200 causes of pulmonary fibrosis have been identified so far, yet the most common form is idiopathic pulmonary fibrosis (IPF). IPF is a lethal lung disorder of unknown etiology with a gradually increasing worldwide incidence and a median survival of 3-5 years from the time of diagnosis. Despite intense research efforts, the pathogenesis remains elusive and no effective treatment is available. Accumulating body of evidence suggests an abnormal wound healing response followed by extracellular matrix deposition, destruction of lung architecture, ultimately leading to respiratory failure. The contribution of immune system in lung fibrogenesis had been largely underscored due to the absence of response to immunosuppressive agents; however, the premise that lung fibrosis has an immunologic background has been recently revived. Toll-like receptors (TLRs) are pattern recognition receptors (PRRs), which link innate and adaptive immune response and regulate wound healing. TLRs promote tissue repair or fibrosis in many disease settings including lung fibrosis, albeit with profound differences depending on the cellular microenvironment. This review summarizes the current state of knowledge regarding the mechanistic implications between TLRs and lung fibrosis and highlights the therapeutic potential of targeting TLR signaling at the ligand or receptor level.

Redox mechanisms in age-related lung fibrosis

Redox signaling and oxidative stress are associated with tissue fibrosis and aging. Aging is recognized as a major risk factor for fibrotic diseases involving multiple organ systems, including that of the lung. A number of oxidant generating enzymes are upregulated while antioxidant defenses are deficient with aging and cellular senescence, leading to redox imbalance and oxidative stress. However, the precise mechanisms by which redox signaling and oxidative stress contribute to the pathogenesis of lung fibrosis are not well understood. Tissue repair is a highly regulated process that involves the interactions of several cell types, including epithelial cells, fibroblasts and inflammatory cells. Fibrosis may develop when these interactions are dysregulated with the acquisition of pro-fibrotic cellular phenotypes. In this review, we explore the roles of redox mechanisms that promote and perpetuate fibrosis in the context of cellular senescence and aging.

Attenuation of lung fibrosis in mice with a clinically relevant inhibitor of glutathione-S-transferase π

Idiopathic pulmonary fibrosis (IPF) is a debilitating lung disease characterized by excessive collagen production and fibrogenesis. Apoptosis in lung epithelial cells is critical in IPF pathogenesis, as heightened loss of these cells promotes fibroblast activation and remodeling. Changes in glutathione redox status have been reported in IPF patients. S-glutathionylation, the conjugation of glutathione to reactive cysteines, is catalyzed in part by glutathione-S-transferase π (GSTP). To date, no published information exists linking GSTP and IPF to our knowledge. We hypothesized that GSTP mediates lung fibrogenesis in part through FAS S-glutathionylation, a critical event in epithelial cell apoptosis. Our results demonstrate that GSTP immunoreactivity is increased in the lungs of IPF patients, notably within type II epithelial cells. The FAS-GSTP interaction was also increased in IPF lungs. Bleomycin- and AdTGFβ-induced increases in collagen content, α-SMA, FAS S-glutathionylation, and total protein S-glutathionylation were strongly attenuated in Gstp-/- mice. Oropharyngeal administration of the GSTP inhibitor, TLK117, at a time when fibrosis was already apparent, attenuated bleomycin- and AdTGFβ-induced remodeling, α-SMA, caspase activation, FAS S-glutathionylation, and total protein S-glutathionylation. GSTP is an important driver of protein S-glutathionylation and lung fibrosis, and GSTP inhibition via the airways may be a novel therapeutic strategy for the treatment of IPF.

Recent advances in understanding idiopathic pulmonary fibrosis

Despite major research efforts leading to the recent approval of pirfenidone and nintedanib, the dismal prognosis of idiopathic pulmonary fibrosis (IPF) remains unchanged. The elaboration of international diagnostic criteria and disease stratification models based on clinical, physiological, radiological, and histopathological features has improved the accuracy of IPF diagnosis and prediction of mortality risk. Nevertheless, given the marked heterogeneity in clinical phenotype and the considerable overlap of IPF with other fibrotic interstitial lung diseases (ILDs), about 10% of cases of pulmonary fibrosis remain unclassifiable. Moreover, currently available tools fail to detect early IPF, predict the highly variable course of the disease, and assess response to antifibrotic drugs.

Recent advances in understanding the multiple interrelated pathogenic pathways underlying IPF have identified various molecular phenotypes resulting from complex interactions among genetic, epigenetic, transcriptional, post-transcriptional, metabolic, and environmental factors. These different disease endotypes appear to confer variable susceptibility to the condition, differing risks of rapid progression, and, possibly, altered responses to therapy. The development and validation of diagnostic and prognostic biomarkers are necessary to enable a more precise and earlier diagnosis of IPF and to improve prediction of future disease behaviour. The availability of approved antifibrotic therapies together with potential new drugs currently under evaluation also highlights the need for biomarkers able to predict and assess treatment responsiveness, thereby allowing individualised treatment based on risk of progression and drug response. This approach of disease stratification and personalised medicine is already used in the routine management of many cancers and provides a potential road map for guiding clinical care in IPF.

Safety and tolerability of acetylcysteine and pirfenidone combination therapy in idiopathic pulmonary fibrosis: a randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND

Oral acetylcysteine (also known as N-acetylcysteine) is used with pirfenidone to treat idiopathic pulmonary fibrosis (IPF) in Europe. However, no randomised studies have investigated the safety and tolerability of this combination. The PANORAMA study assessed the safety and tolerability of acetylcysteine combined with pirfenidone in patients with IPF. Exploratory efficacy endpoints were also assessed.

METHODS

We did a double-blind randomised trial at 48 sites in eight countries. Patients with IPF aged 40-80 years and established on pirfenidone (at least 1602 mg/day for 8 weeks or longer) were randomly assigned in a 1:1 ratio by interactive voice response system to receive concomitant oral acetylcysteine (600 mg, three times daily) or placebo for 24 weeks. A stratified blocked randomisation scheme was used with a block size of 4. Randomisation was stratified by dose of pirfenidone (2403 mg/day [the maximum dose] or <2403 mg/day). Patients, physicians, study staff and the sponsor were masked to treatment group allocation. The primary endpoint was assessment of adverse events, which were collected at each visit and for 28 days after the last dose of study drug. Exploratory efficacy measurements included forced vital capacity (FVC), carbon monoxide diffusing capacity, and 6 min walk distance. Analyses were done in the modified intention-to-treat population, which included all patients who were randomised and received at least one dose of study medication. This study is registered with the European Clinical Trials Database (EudraCT number 2012-000564-14) and has been completed.

FINDINGS

123 patients participated in the study between June 28, 2013, and Feb 24, 2015. 61 were assigned to the acetylcysteine group (60 received study medication and included in analysis) and 62 were assigned to the placebo group (all included in analysis). The occurrence of at least one adverse event (46 [77%] patients receiving acetylcysteine vs 50 [81%] receiving placebo), adverse events related to study treatment (17 [28%] vs 16 [26%]), and the number of patients experiencing severe adverse events (three [5%] vs two [3%]), life-threatening adverse events (one [2%] vs one [2%]), or death (one [2%] vs three [5%]) was similar between treatment groups. One case of diarrhoea in the acetylcysteine group was considered severe and related to study treatment. Nine serious adverse events were reported by seven patients: dyspnoea, headache, hypertension, intervertebral disc protrusion, and malignant lung neoplasm in the acetylcysteine group, and aortic aneurysm, contusion, forearm fracture, and worsening IPF in the placebo group. The most common adverse events were cough, nasopharyngitis, and diarrhoea. Photosensitivity occurred more frequently with acetylcysteine (eight [13%] patients) than placebo (one [2%] patient; difference 11·7%; 95% CI 2·6-20·9; p=0·016]), and was not attributable to differences in location, season, or concomitant medication. Four (7%) patients receiving acetylcysteine and three (5%) receiving placebo discontinued study treatment due to adverse events. In the exploratory analysis, change in FVC indicated that clinical benefit from addition of acetylcysteine to pirfenidone is unlikely, with the possibility of a harmful effect in patients with IPF (adjusted rate of decline 125·6 mL/6 months for acetylcysteine vs 34·3 mL/6 months for placebo; difference -91·3 mL; 95% CI -174·4 to -8·3; p=0·031).

INTERPRETATION

Findings from the PANORAMA study suggest that addition of acetylcysteine to pirfenidone does not substantially alter the tolerability profile of pirfenidone, and is unlikely to be beneficial in IPF.

FUNDING

InterMune International AG (Roche).

Pharmacological management of IPF

Idiopathic pulmonary fibrosis (IPF) is a deadly disease with a median survival of approximately three years in historical cohorts. Despite increased knowledge of disease pathophysiology and selection of more targeted therapy, main clinical trials yielded negative results. However, two agents, pirfenidone and nintedanib, were recently shown to be effective in IPF and received marketing authorization worldwide. Both drugs significantly reduce functional decline and disease progression with an acceptable safety profile. Yet, none of these drugs actually improves or even stabilizes the disease or the symptoms perceived by the patient. Several other treatments and combinations are currently tested, and many more are ready for clinical trials. Their completion is critical for achieving the ultimate goal of curing patients with IPF.

Novel drug targets for idiopathic pulmonary fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a progressive, fatal lung disorder of unknown cause with a highly variable and unpredictable clinical course. The advances made in deciphering IPF pathobiology over the last decades have led to the approval of two anti-fibrotic molecules, pirfenidone and nintedanib, that showed to be effective in significantly reducing the rate of progression of the disease. Such pharmacological breakthroughs represent a dramatic change in the management of these patients and are reflected in updated international guidelines. However, the need to find a cure for this devastating disease remains unmet and the development of novel therapeutic agents remains hurdled by several factors. Here, we review the latest insights into therapeutic approaches for IPF and the available evidence for the most promising novel compounds currently under development, and discuss the challenges and evolution of IPF clinical research over the next few years.

Lung extracellular matrix and redox regulation

Pulmonary fibrosis affects millions worldwide and, even though there has been a significant investment in understanding the processes involved in wound healing and maladaptive repair, a complete understanding of the mechanisms responsible for lung fibrogenesis eludes us, and interventions capable of reversing or halting disease progression are not available. Pulmonary fibrosis is characterized by the excessive expression and uncontrolled deposition of extracellular matrix (ECM) proteins resulting in erosion of the tissue structure. Initially considered an 'end-stage' process elicited after injury, these events are now considered pathogenic and are believed to contribute to the course of the disease. By interacting with integrins capable of signal transduction and by influencing tissue mechanics, ECM proteins modulate processes ranging from cell adhesion and migration to differentiation and growth factor expression. In doing so, ECM proteins help orchestrate complex developmental processes and maintain tissue homeostasis. However, poorly controlled deposition of ECM proteins promotes inflammation, fibroproliferation, and aberrant differentiation of cells, and has been implicated in the pathogenesis of pulmonary fibrosis, atherosclerosis and cancer. Considering their vital functions, ECM proteins are the target of investigation, and oxidation-reduction (redox) reactions have emerged as important regulators of the ECM. Oxidative stress invariably accompanies lung disease and promotes ECM expression directly or through the overproduction of pro-fibrotic growth factors, while affecting integrin binding and activation. In vitro and in vivo investigations point to redox reactions as targets for intervention in pulmonary fibrosis and related disorders, but studies in humans have been disappointing probably due to the narrow impact of the interventions tested, and our poor understanding of the factors that regulate these complex reactions. This review is not meant to provide a comprehensive review of this field, but rather to highlight what has been learned and to raise interest in this area in need of much attention.

Pharmacological Treatment of Idiopathic Pulmonary Fibrosis: Current Approaches, Unsolved Issues, and Future Perspectives

Idiopathic pulmonary fibrosis (IPF) is a devastating condition with a 5-year survival of approximately 20%. The disease primarily occurs in elderly patients. IPF is a highly heterogeneous disorder with a clinical course that varies from prolonged periods of stability to episodes of rapid deterioration. In the last decade, improved understanding of disease mechanisms along with a more precise disease definition has allowed the design and completion of a number of high-quality clinical trials. Yet, until recently, IPF was essentially an untreatable disease. Finally, pirfenidone and nintedanib, two compounds with antifibrotic properties, have consistently proven effective in reducing functional decline and disease progression in IPF. This is a major breakthrough for patients and physicians alike, but there is still a long way to go. In fact, neither pirfenidone nor nintedanib is a cure for IPF, and most patients continue to progress despite treatment. As such, comprehensive care of patients with IPF, including management of comorbidities/complications and physical debility and timely referral for palliative care or, in a small number of highly selected patients, lung transplantation, remains essential. Several agents with high potential are currently being tested and many more are ready to be evaluated in clinical trials.