Therapeutic Potential of Treprostinil Inhalation Powder for Patients with Pulmonary Arterial Hypertension: Evidence to Date

Pulmonary arterial hypertension (PAH) is a complex and incurable disease for which pulmonary vasodilators remain the core therapy. Of the three primary pathways that vasodilators target, the prostacyclin pathway was the earliest to be used and currently has the largest number of modalities for drug delivery. Inhaled treprostinil has been introduced as a treatment option in PAH and, more recently, pulmonary hypertension (PH) due to interstitial lung disease (PH-ILD), and the earlier nebulized form has been joined by a dry powder form allowing for more convenient use. In this review, we discuss inhaled treprostinil, focusing on the dry powder inhalation (DPI) formulation, and explore its dosing, applications, and evidence to support patient tolerance and acceptance. Recent trials underpinning the evidence for use of inhaled treprostinil and the most recent developments concerning the drug are discussed. Finally, the review looks briefly into premarket formulations of inhaled treprostinil and relevant early studies suggesting efficacy in PAH treatment.

Pulmonary hypertension in the setting of interstitial lung disease: Approach to management and treatment. A consensus statement from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative-Group 3 Pulmonary Hypertension

Pulmonary hypertension (PH) due to interstitial lung disease (ILD), a commonly encountered complication of fibrotic ILDs, is associated with significant morbidity and mortality. Until recently, the studies of pulmonary vasodilator therapy in PH-ILD have been largely disappointing, with some even demonstrating the potential for harm. This paper is part of a series of Consensus Statements from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative for Group 3 Pulmonary Hypertension, with prior publications covering pathogenesis, prevalence, clinical features, phenotyping, clinical trials, and impact of PH-ILD. It offers a comprehensive review of and a holistic approach to treatment of PH-ILD, including the management of underlying interstitial lung diseases, importance of treating the comorbidities, emphasis on importance of exercise and palliation of dyspnea, and review of the most up-to-date guidelines for referral for potential lung transplant work up. It also summarizes the prior, ongoing, and possibly future studies in treatment of the vascular derangement of this morbid condition.

Impact of targeted pulmonary arterial hypertension therapies in severe pulmonary hypertension in chronic lung diseases

Research questions

Patients with severe pulmonary hypertension associated with chronic lung disease have a poor prognosis. Targeted pulmonary arterial hypertension therapies might improve exercise capacity and outcome, but there are no guidelines on treatments which are not recommended because of an unproven benefit, with discordant results from few studies in this context. The aim of our study was to evaluate targeted pulmonary arterial hypertension therapies for severe group 3 pulmonary hypertension patients.

Study design and methods

We conducted an observational retrospective monocentre study on patients with severe group 3 pulmonary hypertension diagnosed on right heart catheterisation treated with targeted therapies. Primary outcome was an improvement of the distance on 6-min walk test of ≥30 m. Secondary end-points included changes in haemodynamics (pulmonary vascular resistance (PVR) and mean pulmonary arterial pressure (mPAP)) and identification of potential predictive factors of therapeutic response.

Results

139 patients were enrolled. Most patients had monotherapy with phosphodiesterase 5 inhibitors (n=128; 92%). Mean change in 6-min walk distance was +1.5 m after treatment (p=0.59). Forced expiratory volume in 1 s and forced vital capacity were not predictive factors for response. We found a significant improvement of PVR and mPAP of -1.0 Wood Units (p<0.001) and -4 mmHg (p<0.001), respectively, under treatment. 18% of patients had to withdraw treatment for intolerance. Treatment duration <3 months was associated with poor survival (hazard ratio 2.75, p=0.0005).

Conclusion

Oral targeted pulmonary arterial hypertension therapies do not improve exercise capacity in patients with severe pulmonary hypertension associated with chronic lung disease, but could improve haemodynamic parameters.

Pulmonary hypertension in interstitial lung disease: Clinical trial design and endpoints: A consensus statement from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative-Group 3 Pulmonary Hypertension

Pulmonary hypertension (PH) associated with interstitial lung disease (ILD) is an attractive target for clinical trials of PH medications. There are many factors that need to be considered to prime such studies for success. The patient phenotype most likely to respond to the intervention requires weighing the extent of the parenchymal lung disease against the severity of the hemodynamic impairment. The inclusion criteria should not be too restrictive, thus enabling recruitment. The trial should be of sufficient duration to meet the chosen endpoint which should reflect how the patient feels, functions, or survives. This paper summarizes prior studies in PH-ILD and provides a framework of the type of studies to be considered. Inclusion criteria, clinical trial endpoints, and pharmacovigilance in the context of PH-ILD trials are also addressed. Through lessons learnt from prior studies, suggestions and guidance for future clinical trials in PH-ILD are also provided.

Lung Disease-Related Pulmonary Hypertension

Patients with advanced lung disease can develop pulmonary hypertension and succumb to right ventricular failure/cor pulmonale. Patients with pulmonary hypertension owing to chronic lung disease, or World Health Organization group 3 pulmonary hypertension, are more limited and carry a high risk of mortality. Adjunctive therapies remain the cornerstones of treatment. Recent evidence suggests that inhaled pulmonary vasodilator therapy can be helpful in patients with pulmonary hypertension owing to interstitial lung disease. Lung transplantation may be the only life-saving option in select patients, whereas palliative care and hospice should be sought for those who are not candidates as the disease progresses.

Pulmonary hypertension in interstitial lung disease: screening, diagnosis and treatment

PURPOSE OF REVIEW

Pulmonary vascular disease resulting in pulmonary hypertension in the context of interstitial lung disease (PH-ILD) is a common complication that presents many challenges in clinical practice. Despite recent advances, the pathogenetic interplay between parenchymal and vascular disease in ILD is not fully understood. This review provides an overview of the current knowledge and recent advances in the field.

RECENT FINDINGS

Clinical trials employing the phosphodiesterase-5-inhibitor sildenafil delivered negative results whereas riociguat showed harmful effects in the PH-ILD population. More recently, inhaled treprostinil showed positive effects on the primary endpoint (six-min walk-distance) in the largest prospective randomized placebo-controlled trial to date in this patient population. Additionally, a pilot trial of ambulatory inhaled nitric oxide suggests beneficial effects based on the novel endpoint of actigraphy.

SUMMARY

In view of these novel developments this review provides an overview of the status quo of screening, diagnosis and management of pulmonary vascular disease and PH in patients with ILD.

The Trouble With Group 3 Pulmonary Hypertension in Interstitial Lung Disease: Dilemmas in Diagnosis and the Conundrum of Treatment

Pulmonary hypertension (PH) due to interstitial lung disease (ILD; PH-ILD) can complicate a multitude of ILDs, including idiopathic pulmonary fibrosis, chronic hypersensitivity pneumonitis, and nonspecific interstitial pneumonia. Development of PH-ILD is associated with increased need for supplemental oxygen, reduced mobility, and decreased survival. A high index of suspicion is required to make the diagnosis, given the substantial overlap in symptoms with those of ILD without PH. Severely reduced diffusing capacity or 6-min walk test distance, prominent exertional desaturation, and impaired heart rate recovery after exercise are all suggestive of the development of PH-ILD. Traditional transthoracic echocardiography is the most commonly used screening test for PH-ILD, but it lacks sensitivity and specificity. Newer echocardiographic tools involving 3-dimensional assessment of the right ventricle may have a role in both prognosis and the monitoring of patients with PH-ILD. Right-sided heart catheterization remains the gold standard for confirming a diagnosis of PH-ILD. Although there is little debate about the use of supplemental oxygen and diuretic therapy in the treatment of PH-ILD, treatment with pulmonary vasodilator therapy remains controversial. Although several studies have been terminated prematurely for harm, the recently completed INCREASE trial of inhaled treprostinil appears to validate the concept of treating PH-ILD with pulmonary vasodilators and, we hope, will serve as a foundation from which future studies can be developed.

Pulmonary hypertension due to interstitial lung disease

PURPOSE OF REVIEW

Pulmonary hypertension has been reported to complicate the course of a number of fibrotic lung diseases, including idiopathic pulmonary fibrosis, chronic hypersensitivity pneumonitis and nonspecific interstitial pneumonitis. Most commonly, mild elevations in the mean pulmonary artery pressure are seen in patients with advanced pulmonary fibrosis. However, some patients may develop severe pulmonary hypertension, which appears out of proportion to the degree of their restrictive lung disease.

RECENT FINDINGS

The benefits of pulmonary vasodilator therapy have yet to be established in pulmonary hypertension complicating fibrotic lung disease. In fact, one recent clinical trial examining riociguat in patients with pulmonary hypertension complicating idiopathic interstitial pneumonias was terminated early for an increased risk of death or hospitalization. Multiple clinical trials on this topic are currently ongoing, including studies examining inhaled pulmonary vasodilator therapies.

SUMMARY

The development of pulmonary hypertension is associated with increased exertional oxygen requirements, worsened functional capacity and attenuated life expectancy. It is hoped that continued research will find an effective therapy for this condition, which will improve quality of life and extend life expectancy in patients with this condition.

Secondary pulmonary arterial hypertension: to treat or not to treat?

PURPOSE OF REVIEW

The purpose of this review is to review recent literature related to mechanisms and treatment options for 'secondary' (i.e., WHO Groups 3 and 5) pulmonary arterial hypertension (PAH).

RECENT FINDINGS

Published randomized controlled trials, in general, do not support the use of approved therapies for 'primary' (i.e., WHO Group 1) PAH patients in patients with Group 3 PAH because of the small numbers of patients and inconsistent benefit. Therefore, we currently recommend against the use of these medications for Group 3 PAH. Similarly, there is limited evidence supporting the use of Group 1 PAH medications in Group 5 patients. In most patients with Group 5 PAH, treatment should be directed to the underlying disease.

SUMMARY

The utility of PAH-specific therapy in WHO Group 3 PAH is unclear because of the small numbers of patients evaluated and inconsistent beneficial effects observed. There is limited evidence supporting the use of PAH medications in Group 5 patients, and they may be harmful in some cases.

Lipids - two sides of the same coin in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive extracellular matrix deposition in the lung parenchyma leading to the destruction of lung structure, respiratory failure and premature death. Recent studies revealed that the pathogenesis of IPF is associated with alterations in the synthesis and the activity of lipids, lipid regulating proteins and cell membrane lipid transporters and receptors in different lung cells. Furthermore, deregulated lipid metabolism was found to contribute to the profibrotic phenotypes of lung fibroblasts and alveolar epithelial cells. Consequently, several pharmacological agents, targeting lipids, lipid mediators, and lipoprotein receptors, was successfully tested in the animal models of lung fibrosis and entered early phase clinical trials. In this review, we highlight new therapeutic options to counteract disturbed lipid hemostasis in the maladaptive lung remodeling.

Pulmonary Hypertension in Diffuse Parenchymal Lung Diseases

Pulmonary hypertension (PH) can be triggered by any number of disease processes that result in increased pulmonary vascular resistance. Although historically associated with idiopathic pulmonary arterial hypertension (PAH), most patients with PH do not have the idiopathic subtype, but rather PH associated with another underlying diagnosis, such as left heart or lung disease. The World Health Organization (WHO) classification of PH helps conceptualize the different categories based on presumed etiology. WHO group 3 is PH associated with lung disease. This review focuses on PH in diffuse parenchymal lung diseases (DPLDs), such as the idiopathic interstitial pneumonias and other more rare forms of DPLD. Although there are clear associations of PH with DPLD, the exact pathophysiologic mechanisms and full clinical significance remain uncertain. Treatment of PH related to DPLD remains investigational, but an area of great interest given the negative prognostic implications and the growing number of available pulmonary vasoactive agents.

Pulmonary hypertension secondary to interstitial lung disease

Interstitial lung diseases (ILDs) may be complicated by the development of pulmonary hypertension (PH), which is associated with worse functional impairment and a poorer prognosis. This article reviews the current state of knowledge on the prevalence, pathogenesis, diagnosis and prognosis of ILD-related PH. Whether the treatment of ILD-related PH changes clinical outcomes is currently unknown, but the current studies are summarized and the authors' perspective is offered.

Novel therapeutic approaches for pulmonary fibrosis

Pulmonary fibrosis represents the end stage of a number of heterogeneous conditions and is, to a greater or lesser degree, the hallmark of the interstitial lung diseases. It is characterized by the excessive deposition of extracellular matrix proteins within the pulmonary interstitium leading to the obliteration of functional alveolar units and in many cases, respiratory failure. While a small number of interstitial lung diseases have known aetiologies, most are idiopathic in nature, and of these, idiopathic pulmonary fibrosis is the most common and carries with it an appalling prognosis - median survival from the time of diagnosis is less than 3 years. This reflects the lack of any effective therapy to modify the course of the disease, which in turn is indicative of our incomplete understanding of the pathogenesis of this condition. Current prevailing hypotheses focus on dysregulated epithelial-mesenchymal interactions promoting a cycle of continued epithelial cell injury and fibroblast activation leading to progressive fibrosis. However, it is likely that multiple abnormalities in a myriad of biological pathways affecting inflammation and wound repair - including matrix regulation, epithelial reconstitution, the coagulation cascade, neovascularization and antioxidant pathways - modulate this defective crosstalk and promote fibrogenesis. This review aims to offer a pathogenetic rationale behind current therapies, briefly outlining previous and ongoing clinical trials, but will focus on recent and exciting advancements in our understanding of the pathogenesis of idiopathic pulmonary fibrosis, which may ultimately lead to the development of novel and effective therapeutic interventions for this devastating condition.

Eicosanoid lipid mediators in fibrotic lung diseases: ready for prime time?

Recognition of a pivotal role for eicosanoids in both normal and pathologic fibroproliferation is long overdue. These lipid mediators have the ability to regulate all cell types and nearly all pathways relevant to fibrotic lung disorders. Abnormal fibroproliferation is characterized by an excess of profibrotic leukotrienes and a deficiency of antifibrotic prostaglandins. The relevance of an eicosanoid imbalance is pertinent to diseases involving the parenchymal, airway, and vascular compartments of the lung, and is supported by studies conducted both in humans and animal models. Given the lack of effective alternatives, and the existing and emerging options for therapeutic targeting of eicosanoids, such treatments are ready for prime time.