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.

Real-world evidence to advance knowledge in pulmonary hypertension: Status, challenges, and opportunities. A consensus statement from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative's Real-world Evidence Working Group.

This manuscript on real-world evidence (RWE) in pulmonary hypertension (PH) incorporates the broad experience of members of the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative Real-World Evidence Working Group. We aim to strengthen the research community's understanding of RWE in PH to facilitate clinical research advances and ultimately improve patient care. Herein, we review real-world data (RWD) sources, discuss challenges and opportunities when using RWD sources to study PH populations, and identify resources needed to support the generation of meaningful RWE for the global PH community.

Pathogenesis, clinical features, and phenotypes of pulmonary hypertension associated with interstitial lung disease: A consensus statement from the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative - Group 3 Pulmonary Hypertension.

Pulmonary hypertension (PH) is a frequent complication of interstitial lung disease (ILD). Although PH has mostly been described in idiopathic pulmonary fibrosis, it can manifest in association with many other forms of ILD. Associated pathogenetic mechanisms are complex and incompletely understood but there is evidence of disruption of molecular and genetic pathways, with panvascular histopathologic changes, multiple pathophysiologic sequelae, and profound clinical ramifications. While there are some recognized clinical phenotypes such as combined pulmonary fibrosis and emphysema and some possible phenotypes such as connective tissue disease associated with ILD and PH, the identification of further phenotypes of PH in ILD has thus far proven elusive. This statement reviews the current evidence on the pathogenesis, recognized patterns, and useful diagnostic tools to detect phenotypes of PH in ILD. Distinct phenotypes warrant recognition if they are characterized through either a distinct presentation, clinical course, or treatment response. Furthermore, we propose a set of recommendations for future studies that might enable the recognition of new phenotypes.

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.

Inhaled mosliciguat (BAY 1237592): targeting pulmonary vasculature via activating apo-sGC.

BACKGROUND: Oxidative stress associated with severe cardiopulmonary diseases leads to impairment in the nitric oxide/soluble guanylate cyclase signaling pathway, shifting native soluble guanylate cyclase toward heme-free apo-soluble guanylate cyclase. Here we describe a new inhaled soluble guanylate cyclase activator to target apo-soluble guanylate cyclase and outline its therapeutic potential. METHODS: We aimed to generate a novel soluble guanylate cyclase activator, specifically designed for local inhaled application in the lung. We report the discovery and in vitro and in vivo characterization of the soluble guanylate cyclase activator mosliciguat (BAY 1237592). RESULTS: Mosliciguat specifically activates apo-soluble guanylate cyclase leading to improved cardiopulmonary circulation. Lung-selective effects, e.g., reduced pulmonary artery pressure without reduced systemic artery pressure, were seen after inhaled but not after intravenous administration in a thromboxane-induced pulmonary hypertension minipig model. These effects were observed over a broad dose range with a long duration of action and were further enhanced under experimental oxidative stress conditions. In a unilateral broncho-occlusion minipig model, inhaled mosliciguat decreased pulmonary arterial pressure without ventilation/perfusion mismatch. With respect to airway resistance, mosliciguat showed additional beneficial bronchodilatory effects in an acetylcholine-induced rat model. CONCLUSION: Inhaled mosliciguat may overcome treatment limitations in patients with pulmonary hypertension by improving pulmonary circulation and airway resistance without systemic exposure or ventilation/perfusion mismatch. Mosliciguat has the potential to become a new therapeutic paradigm, exhibiting a unique mode of action and route of application, and is currently under clinical development in phase Ib for pulmonary hypertension.

Pulmonary thromboembolic events in COVID-19-A systematic literature review.

Pulmonary thromboembolic events have been linked to coronavirus disease 2019 (COVID-19), but their incidence and long-term sequelae remain unclear. We performed a systematic literature review to investigate the incidence of pulmonary embolism (PE), microthrombi, thrombosis in situ (thromboinflammatory disease), and chronic thromboembolic pulmonary hypertension (CTEPH) during and after COVID-19. PubMed and the World Health Organization Global Research Database were searched on May 7, 2021. Hospital cohort and database studies reporting data for ≥1000 patients and autopsy studies reporting data for ≥20 patients were included. Results were summarized descriptively. We screened 1438 records and included 41 references (32 hospital/database studies and 9 autopsy studies). The hospital/database studies reported the incidence of PE but not CTEPH, microthrombi, or thromboinflammatory disease. PE incidence varied widely (0%-1.1% of outpatients, 0.9%-8.2% of hospitalized patients, and 1.8%-18.9% of patients in intensive care). One study reported PE events occurring within 45 days after hospital discharge (incidence in discharged patients: 0.2%). Segmental arteries were generally the most common location for PE. In autopsy studies, PE, thromboinflammatory disease, and microthrombi were reported in 6%-23%, 43%-100%, and 45%-84% of deceased patients, respectively. Overall, the included studies mostly focused on PE during the acute phase of COVID-19. The results demonstrate the challenges of identifying and characterizing vascular abnormalities using current protocols (e.g., visual computed tomography reads). Further research is needed to detect subtle pulmonary vascular abnormalities, distinguish thromboinflammatory disease from PE, optimize treatment, and assess the incidence of long-term sequelae after COVID-19.

Clinical significance of pulmonary hypertension in interstitial lung disease: A consensus statement from the Pulmonary Vascular Research Institute's innovative drug development initiative-Group 3 pulmonary hypertension.

Pulmonary hypertension (PH) has been linked to worse outcomes in chronic lung diseases. The presence of PH in the setting of underlying Interstitial Lung Disease (ILD) is strongly associated with decreased exercise and functional capacity, an increased risk of hospitalizations and death. Examining the scope of this issue and its impact on patients is the first step in trying to define a roadmap to facilitate and encourage future research in this area. The aim of our working group is to strengthen the communities understanding of PH due to lung diseases and to improve the care and quality of life of affected patients. This introductory statement provides a broad overview and lays the foundation for further in-depth papers on specific topics pertaining to PH-ILD.

Application of the REVEAL risk score calculator 2.0 in the CHEST study.

BACKGROUND: Currently there are no risk assessment recommendations for chronic thromboembolic pulmonary hypertension (CTEPH). The Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL) risk score (RRS), developed for risk assessment in patients with pulmonary arterial hypertension, has previously predicted outcomes in CTEPH. RRS 2.0 was developed to refine the RRS. METHODS: This post hoc analysis of the CHEST study (n = 237), which assessed riociguat in patients with inoperable and persistent/recurrent CTEPH, evaluated RRS 2.0 and its relationship with survival and clinical worsening-free survival (CWFS). RESULTS: At CHEST-1 Week 16, RRS 2.0 significantly improved and more patients moved into the low-risk stratum with riociguat versus placebo; these improvements were maintained at CHEST-2 Week 12. RRS 2.0 at CHEST-1 baseline and Week 16, and change in RRS 2.0 from CHEST-1 baseline to Week 16 were significant predictors of survival and CWFS in CHEST-2. CONCLUSIONS: Our data suggest that RRS 2.0 may have utility in predicting outcomes and monitoring treatment response in patients with inoperable or persistent/recurrent CTEPH.

Change in REVEAL Lite 2 risk score predicts outcomes in patients with pulmonary arterial hypertension in the PATENT study.

BACKGROUND: Risk assessment is essential in pulmonary arterial hypertension (PAH) management. We investigated the effect of riociguat on REVEAL Lite 2 score, an abridged version of the REVEAL risk score, and its association with long-term outcomes in PATENT. METHODS: PATENT-1 was a randomized, double-blind study of riociguat vs placebo in patients with PAH. In the PATENT-2 open-label extension, all patients received riociguat up to 2.5 mg three times daily (n = 396). REVEAL Lite 2 scores were calculated at baseline, PATENT-1 Week 12, and PATENT-2 Week 12, with patients stratified as low- (1-5), intermediate- (6-7), or high-risk (≥8). Kaplan-Meier and Cox proportional hazards analyses assessed association of riociguat with survival and clinical worsening-free survival (CWFS). RESULTS: REVEAL Lite 2 score improved with riociguat 2.5 mg at PATENT-1 Week 12 (least-squares mean difference vs placebo: -0.8; p = 0.0004). More patients receiving riociguat 2.5 mg stabilized or improved risk stratum at PATENT-1 Week 12 vs placebo (p = 0.0005) and achieved low-risk status. REVEAL Lite 2 score at baseline and PATENT-1 Week 12 were associated with survival and CWFS (all p < 0.0001), as was change in score from baseline to Week 12 (p = 0.0002 and p < 0.0001, respectively). Survival and CWFS differed between risk strata at baseline (p < 0.0001) and PATENT-1 Week 12 (p < 0.0001). CONCLUSIONS: This analysis confirms the risk-reduction benefits of riociguat in patients with PAH and further contributes to the validation of REVEAL Lite 2 in facilitating PAH risk assessment.

Impact of lung morphology on clinical outcomes with riociguat in patients with pulmonary hypertension and idiopathic interstitial pneumonia: A post hoc subgroup analysis of the RISE-IIP study.

BACKGROUND: Riociguat in Patients with Symptomatic Pulmonary Hypertension associated with Idiopathic Interstitial Pneumonias (RISE-IIP), a randomized, controlled, phase 2b trial of riociguat for pulmonary hypertension associated with idiopathic interstitial pneumonia, was terminated early due to increased mortality in riociguat-treated patients. Baseline characteristics of enrolled patients demonstrated a low diffusing capacity of the lung for carbon monoxide (DLCO) with preserved lung volumes at baseline, suggesting the presence of combined pulmonary fibrosis and emphysema (CPFE) in some patients. This post hoc analysis of RISE-IIP was undertaken to explore lung morphology, assessed by high-resolution computed tomography, and associated clinical outcomes. METHODS: Available baseline/pre-baseline high-resolution computed tomography scans were reviewed centrally by 2 radiologists. The extent of emphysema and fibrosis was retrospectively scored and combined to provide the total CPFE score. RESULTS: Data were available for 65/147 patients (44%), including 15/27 fatal cases (56%). Of these, 41/65 patients (63%) had CPFE. Mortality was higher in patients with CPFE (12/41; 29%) than those without (3/24; 13%). Fourteen patients with CPFE had emphysema > fibrosis (4 died). No relationship was observed between CPFE score, survival status, and treatment assignment. A low DLCO, short 6-min walking distance, and high forced vital capacity:DLCO ratio at baseline also appeared to be risk factors for mortality. CONCLUSIONS: High parenchymal lung disease burden and the presence of more emphysema than fibrosis might have predisposed patients with pulmonary hypertension associated with idiopathic interstitial pneumonia to poor outcomes in RISE-IIP. Future studies of therapy for group 3 pulmonary hypertension should include centrally adjudicated imaging for morphologic phenotyping and disease burden evaluation during screening.

Application of the REVEAL risk score calculator 2.0 in the PATENT study.

BACKGROUND: Regular risk assessment is recommended in pulmonary arterial hypertension (PAH) management to improve patient outcomes. The REVEAL risk score (RRS) predicts survival in patients with PAH, including those from the PATENT study, which assessed riociguat, a soluble guanylate cyclase stimulator approved for PAH treatment. An updated version, RRS 2.0, has been developed to further refine risk prediction. METHODS: This post hoc analysis of PATENT-1 and its open-label extension PATENT-2 (n = 396) assessed RRS 2.0 score and risk stratum and their association with survival and clinical worsening-free survival (CWFS). RESULTS: At PATENT-1 Week 12, riociguat improved RRS 2.0 versus placebo (least-squares mean difference versus placebo: -1.0 [95% confidence interval - 1.4 to -0.6; p < 0.0001]) and more patients improved risk stratum with riociguat (57%) versus placebo (42%). These improvements were maintained at PATENT-2 Week 12. RRS 2.0 score and risk strata at PATENT-1 baseline and Week 12 were significantly associated with survival and CWFS in PATENT-2 (p < 0.0001); change in RRS 2.0 score from PATENT-1 baseline to Week 12 was also significantly associated with outcomes. CONCLUSIONS: These data suggest that RRS 2.0 has clinical utility in predicting long-term outcomes and monitoring treatment response in patients with PAH.

Clinical trial design in phase 2 and 3 trials for pulmonary hypertension.

This article on clinical trial design incorporates the broad experience of members of the Pulmonary Vascular Research Institute's (PVRI) Innovative Drug Development Initiative (IDDI) as an open debate platform for academia, the pharmaceutical industry and regulatory experts surrounding the future design of clinical trials in pulmonary hypertension. It is increasingly clear that the design of phase 2 and 3 trials in pulmonary hypertension will have to diversify from the traditional randomised double-blind design, given the anticipated need to trial novel therapeutic approaches in the immediate future. This article reviews a wide range of differing approaches and places these into context within the field of pulmonary hypertension.

Repurposing of medications for pulmonary arterial hypertension.

This manuscript on drug repurposing incorporates the broad experience of members of the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative as an open debate platform for academia, the pharmaceutical industry and regulatory experts surrounding the future design of clinical trials in pulmonary hypertension. Drug repurposing, use of a drug in a disease for which it was not originally developed, in pulmonary arterial hypertension has been a remarkable success story, as highlighted by positive large phase 3 clinical trials using epoprostenol, bosentan, iloprost, and sildenafil. Despite the availability of multiple therapies for pulmonary arterial hypertension, mortality rates have modestly changed. Moreover, pulmonary arterial hypertension patients are highly symptomatic and frequently end up on parental therapy and lung transplant waiting lists. Therefore, an unmet need for new treatments exists and drug repurposing may be an important avenue to address this problem.

Novel composite clinical endpoints and risk scores used in clinical trials in pulmonary arterial hypertension.

This manuscript on endpoints incorporates the broad experience of members of Pulmonary Vascular Research Institute's Innovative Drug Development Initiative as an open debate platform for academia, the pharmaceutical industry and regulatory experts surrounding the future design of clinical trials in pulmonary hypertension. It reviews our current understanding of endpoints used in phase 2 and 3 trials for pulmonary hypertension and discusses in detail the value of newer approaches. These include the roles of composite endpoints and how these can be developed and validated. The newer concept of risk analysis is also discussed, including how such risk scores might be utilised as endpoints in clinical trials.

Effect of riociguat on pulmonary arterial compliance in the PATENT and CHEST studies.

Pulmonary arterial compliance is a measure of the pulsatile afterload of the right ventricle. Lower pulmonary arterial compliance is associated with reduced right ventricular function and worse prognosis in pulmonary hypertension. The effect of pulmonary vasodilators on pulmonary arterial compliance has not been evaluated in detail in pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. In this post hoc analysis of patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension in the PATENT and CHEST studies, we evaluated the change in pulmonary arterial compliance with riociguat versus placebo. Association of pulmonary arterial compliance with clinical outcomes was assessed using Kaplan-Meier and Cox proportional hazards analyses. Compared with placebo, riociguat significantly improved pulmonary arterial compliance in patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. Pulmonary arterial compliance at baseline was associated with survival and clinical worsening-free survival in pulmonary arterial hypertension but only with clinical worsening-free survival in chronic thromboembolic pulmonary hypertension. In patients with pulmonary arterial hypertension, pulmonary arterial compliance at follow-up ≥1.6 mL/mmHg was associated with better outcomes than pulmonary arterial compliance <1.6 mL/mmHg. In patients with chronic thromboembolic pulmonary hypertension, pulmonary arterial compliance at follow-up did not predict outcomes. Cox proportional hazards analyses showed no association between change in pulmonary arterial compliance and outcomes in patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. In conclusion, riociguat improved pulmonary arterial compliance in patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. Pulmonary arterial compliance at baseline or follow-up, rather than change in pulmonary arterial compliance, is of prognostic importance for outcomes.

REVEAL risk score in patients with chronic thromboembolic pulmonary hypertension receiving riociguat.

BACKGROUND: The REVEAL risk score (RRS) was developed to predict survival in patients with pulmonary arterial hypertension (PAH), based on multiple patient characteristics. Herein we calculated RRS for patients in the randomized CHEST-1 study and open-label CHEST-2 extension study of riociguat in inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH). We investigated the effect of riociguat vs placebo on RRS in the CHEST-1 study, and the relationship between RRS and long-term outcomes in the CHEST-2 study. METHODS: RRS was calculated post hoc for baseline and Week 16 of CHEST-1 and Week 12 of CHEST-2, based on 9 evaluable elements. Patients were grouped into risk strata by RRS. Relationships between RRS and both survival and clinical worsening-free survival were examined by Kaplan-Meier and Cox proportional hazards analyses. RESULTS: Overall, 237 patients completed CHEST-1 and entered CHEST-2. In CHEST-1, riociguat significantly improved RRS (p < 0.0001) and risk stratum (p < 0.001) vs placebo from baseline to Week 16. RRS at baseline, and at Week 16, and change in RRS during CHEST-1 were significantly associated with survival (hazard ratios for a 1-point reduction in RRS: 0.702, 0.692, and 0.682, respectively) and clinical worsening-free survival (hazard ratios: 0.697, 0.719, and 0.754, respectively) over 2 years in CHEST-2. CONCLUSIONS: Riociguat improved RRS in patients with inoperable and persistent/recurrent CTEPH. RRS at baseline and Week 16, and change in RRS from baseline, predicted survival and clinical worsening-free survival. This analysis of RRS in patients with inoperable or persistent/recurrent CTEPH suggests utility for the RRS in indications beyond PAH.

REVEAL risk scores applied to riociguat-treated patients in PATENT-2: Impact of changes in risk score on survival.

BACKGROUND: The Registry to Evaluate Early and Long-term PAH Disease Management (REVEAL) risk score (RRS) calculator was developed using data derived from the REVEAL registry, and predicts survival in patients with pulmonary arterial hypertension (PAH) based on multiple patient characteristics. Herein we applied the RRS to a pivotal PAH trial database, the 12-week PATENT-1 and open-label PATENT-2 extension studies of riociguat. We examined the effect of riociguat vs placebo on RRS in PATENT-1, and investigated the prognostic implications of change in RRS during PATENT-1 on long-term outcomes in PATENT-2. METHODS: RRS was calculated post hoc for baseline and Week 12 of PATENT-1, and Week 12 of PATENT-2. Patients were grouped into risk strata by RRS. Kaplan-Meier estimates were made for survival and clinical worsening-free survival in PATENT-2 to evaluate the relationship between RRS in PATENT-1 and long-term outcomes in PATENT-2. RESULTS: A total of 396 patients completed PATENT-1 and participated in PATENT-2. In PATENT-1, riociguat significantly improved RRS (p = 0.031) and risk stratum (p = 0.018) between baseline and Week 12 compared with placebo. RRS at baseline, and at PATENT-1 Week 12, and change in RRS during PATENT-1 were significantly associated with survival (hazard ratios for a 1-point reduction in RRS: 0.675, 0.705 and 0.804, respectively) and clinical worsening-free survival (hazard ratios of 0.736, 0.716 and 0.753, respectively) over 2 years in PATENT-2. CONCLUSIONS: RRS at baseline and Week 12, and change in RRS, were significant predictors of both survival and clinical worsening-free survival. These data support the long-term predictive value of the RRS in a controlled study population.

Riociguat in patients with chronic thromboembolic pulmonary hypertension: results from an early access study.

BACKGROUND: Following positive results from the Phase III CHEST-1 study in patients with inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH), the Phase IIIb CTEPH early access study (EAS) was designed to assess the safety and tolerability of riociguat in real-world clinical practice, as well as to provide patients with early access to riociguat before launch. Riociguat is approved for the treatment of inoperable and persistent/recurrent CTEPH. METHODS: We performed an open-label, uncontrolled, single-arm, early access study in which 300 adult patients with inoperable or persistent/recurrent CTEPH received riociguat adjusted from 1 mg three times daily (tid) to a maximum of 2.5 mg tid. Patients switching from unsatisfactory prior pulmonary arterial hypertension (PAH)-targeted therapy (n = 84) underwent a washout period of at least 3 days before initiating riociguat. The primary aim was to assess the safety and tolerability of riociguat, with World Health Organization functional class and 6-min walking distance (6MWD) as exploratory efficacy endpoints. RESULTS: In total, 262 patients (87%) completed study treatment and entered the safety follow-up (median treatment duration 47 weeks). Adverse events were reported in 273 patients (91%). The most frequently reported serious adverse events were syncope (6%), right ventricular failure (3%), and pneumonia (2%). There were five deaths, none of which was considered related to study medication. The safety and tolerability of riociguat was similar in patients switched from other PAH-targeted therapies and those who were treatment naïve. In patients with data available, mean ± standard deviation 6MWD had increased by 33 ± 42 m at Week 12 with no clinically relevant differences between the switched and treatment-naïve subgroups. CONCLUSIONS: Riociguat was well tolerated in patients with CTEPH who were treatment naïve, and in those who were switched from other PAH-targeted therapies. No new safety signals were observed. TRIAL REGISTRATION: ClinicalTrials.org NCT01784562 . Registered February 4, 2013.

Riociguat for pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension: Results from a phase II long-term extension study.

BACKGROUND: Riociguat was well tolerated and improved exercise and functional capacity in patients with pulmonary arterial hypertension (PAH) and inoperable chronic thromboembolic pulmonary hypertension (CTEPH) in a 12-week Phase II trial. We present final data from the long-term extension phase of this study. METHODS: During this multicenter, open-label, uncontrolled long-term extension study, riociguat dose could be changed at the physician's discretion (range 0.5-2.5 mg three times daily). The primary outcome was long-term safety and tolerability of riociguat; secondary outcomes included 6-minute walking distance, World Health Organization functional class, survival, and clinical worsening-free survival. RESULTS: Sixty-eight patients (inoperable CTEPH, n = 41; PAH, n = 27) entered the long-term extension. Median treatment duration at the final data cut-off was 77 months. The most common adverse events were nasopharyngitis (57%) and peripheral edema (37%). Three patients (4%) experienced serious adverse events of hemoptysis: two moderate, one severe, none fatal or considered drug-related. At Month 48, 6-minute walking distance increased from baseline by 69 ± 105 m, and World Health Organization functional class improved/stabilized/worsened versus baseline in 50/45/5% of patients. Three-year survival and clinical worsening-free survival were 91% and 49%, respectively (with patients censored if they withdrew without experiencing an event). Starting a new PAH treatment was the most frequent clinical worsening event. CONCLUSIONS: Improvements in exercise and functional capacity were maintained at 4 years in patients remaining on treatment, with no new safety signals identified. These data support riociguat as a long-term treatment option for PAH and inoperable CTEPH. TRIAL REGISTERED AT: ClinicalTrials.gov. REGISTRATION NUMBER: NCT00454558.