BACKGROUND:Combined post- and precapillary pulmonary hypertension in heart failure with preserved ejection fraction involves remodeling in both the heart and pulmonary vasculature. Despite significant mortality, there are no proven therapies. METHODS:In this multicenter, randomized, placebo-controlled, phase 2 trial, adults received sotatercept (0.3 or 0.7 mg/kg) or placebo every 3 weeks. The primary end point was change in pulmonary vascular resistance at week 24. Hodges-Lehmann shift estimates described placebo-adjusted changes. RESULTS:A total of 164 patients were randomized 54:55:55 to sotatercept 0.3 mg/kg, 0.7 mg/kg, and placebo, and baseline median pulmonary vascular resistance was 5.2 (interquartile range, 4.0-6.9) Wood units. The median change from baseline in pulmonary vascular resistance at week 24 was -0.67 Wood units in the sotatercept 0.3 mg/kg group, -0.33 Wood units in the sotatercept 0.7 mg/kg group, and 0.26 Wood units in the placebo group. The Hodges-Lehmann shift estimates in pulmonary vascular resistance were -1.02 Wood units (95% CI, -1.81 to -0.23; P=0.004) for 0.3 mg/kg and -0.75 Wood units (95% CI, -1.52 to 0.03; P=0.024) for 0.7 mg/kg sotatercept. Reductions were observed in mean pulmonary arterial pressure (0.3 and 0.7 mg/kg: -9.19 mm Hg [95% CI, -13.00 to -5.38] and -9.22 [95% CI, -12.97 to -5.46]) and pulmonary arterial wedge pressure (0.3 and 0.7 mg/kg: -3.04 mm Hg [95% CI, -5.77 to -0.32] and -2.53 [95% CI, -5.33 to 0.28]). Changes in 6-minute walk distance were 20.3 m (95% CI, 1.5-39.1) for 0.3 mg/kg and 5.8 m (95% CI, -17.3 to 28.9) for 0.7 mg/kg sotatercept. The most common adverse events with sotatercept (both groups) were increased hemoglobin and diarrhea. CONCLUSIONS:These findings provide proof of concept for improved pulmonary vascular and cardiac hemodynamics after activin signaling inhibition with sotatercept in patients with combined post- and precapillary pulmonary hypertension in heart failure with preserved ejection fraction. REGISTRATION:URL: https://www.clinicaltrials.gov; Unique identifier: NCT04945460.

The human lung normally accommodates exercise-induced cardiac output increases mainly via recruitment of non-concomitantly perfused pulmonary capillaries. Recruitment is detectable by measuring the first-pass transpulmonary metabolism of 3H-benzoyl-Phe-Ala-Pro, providing an estimate of functional capillary surface area (FCSA). Pulmonary arterial hypertension (PAH) results from luminal narrowing of small precapillary arterioles, reducing downstream perfused FCSA. We hypothesized that exercising PAH patients would not be able to recruit FCSA normally. We studied two patients with severe PAH. Despite exercising to maximal dyspnea, neither could recruit FCSA. These limited data are the first direct measurements of FCSA in exercising PAH patients.

Exercise testing has long been essential for evaluating diagnosis, prognosis, and functional status in pulmonary hypertension (PH). Recent advances have clarified its role in defining reference values and prognostic markers. Nonetheless, substantial knowledge gaps persist regarding the implementation of invasive cardiopulmonary exercise testing (iCPET) and its potential to inform pathophysiology and therapeutic decision-making. This statement addresses the knowledge gaps that hinder the application of iCPET and exercise right heart catheterization (RHC) in the assessment of PH. We present research priorities and scenarios in which these tests may clarify drug mechanisms and support PH subphenotyping. An international, multidisciplinary task force of cardiology and pulmonology experts reviewed the literature and formulated consensus recommendations through iterative discussions.

INTRODUCTION/BACKGROUND:Oral imatinib, a tyrosine kinase inhibitor, demonstrated efficacy in pulmonary arterial hypertension (PAH) studies but was poorly tolerated. We report here the findings of a study using a dry powder inhaled version of imatinib (AV-101). AIMS AND OBJECTIVES:IMPAHCT (NCT05036135) was designed to assess the efficacy, safety, tolerability, and optimal dose of AV-101 as an add-on treatment for PAH, using a novel phase 2b/3 adaptive study design. Here we report the phase 2b results. METHODS:The phase 2b part assessed 3 doses of AV-101 (10 mg, 35 mg, and 70 mg), administered twice a day, vs placebo for 24 weeks as an add-on treatment in adults with PAH. Change in pulmonary vascular resistance (PVR) was the primary endpoint. Secondary endpoints included the change in other hemodynamic variables, 6-minute walk distance (6MWD), World Health Organization functional class, Registry to Evaluate Early and Long-Term PAH Disease Management Lite 2 risk score, clinical worsening, clinical improvement, N-terminal proB-type natriuretic peptide, quality of life, safety, and tolerability. RESULTS:In total, 202 patients were randomized. Baseline characteristics were broadly well balanced between groups. There were no significant improvements vs placebo in PVR (42.8 dyn·s·cm-5 in the AV-101 10-mg group, -5.5 dyn·s·cm-5 in the AV-101 35-mg group, -57.0 dyn·s·cm-5 in the AV-101 70-mg group, and 19.5 dyn·s·cm-5 in the placebo group), 6MWD, or other secondary endpoints at any dose. Pharmacokinetic measures supported delivery of drug to the lung and into the plasma. The incidence of cough increased with dose. No safety concerns were identified. CONCLUSIONS:Add-on dry powder inhaled imatinib (AV-101) was not effective in lowering PVR at any of the studied doses in patients with PAH. The phase 3 part of the IMPAHCT study was halted.

A 22-year-old woman presented with a rapid clinical deterioration, precapillary pulmonary hypertension (PH), and cardiogenic shock. She received inotropic support and vasodilatory pulmonary arterial hypertension (PAH) therapy. Two hours after the first dose of oral tadalafil, her dyspnea and systemic perfusion had improved markedly. She had been consuming a vitamin C-free diet. Vitamin C was given, and her echocardiogram had normalized by day 4. Vitamin C deficiency should be considered in the differential diagnosis of precapillary PH. The rapid response to phosphodiesterase-5 inhibition supports a prominent role for deficient pulmonary nitric synthesis in scurvy and PH.

Transition from parenteral prostanoids to oral selexipag may be considered in select patients with pulmonary arterial hypertension (PAH) to reduce the therapeutic burden imposed on patients and caregivers, but its safety and efficacy remain uncertain. A retrospective cohort study was conducted involving adult patients with PAH who transitioned from parenteral prostanoids to selexipag at Canadian tertiary referral centers between January 2016 and November 2020. The primary outcome was transition failure at 12 months, defined as a composite of death or PAH-related worsening. Baseline predictors of transition failure were identified using univariate Cox regression, with follow-up data collected up to 36 months post-transition or until site-specific data submission, occurring between May 2021 and February 2023. At 12 months post-transition, 11 of 36 patients (31%) experienced transition failure, including 4 deaths, all classified as high-risk pre-transition. Of the 25 patients (69%) who successfully transitioned, only one (4%) experienced transition failure over the subsequent observation period (median follow-up 28 months). Pre-transition variables protective against transition failure included a right atrial pressure (RAP) < 8 mmHg (HR 0.290, 95% CI 0.084-0.999, p = 0.049), absence of hospitalizations in the year preceding transition (HR 0.239, 95% CI 0.064-0.885, p = 0.032), lower brain natriuretic peptide (< 50 pg/mL)/N-terminal pro-B-type natriuretic peptide (< 300 pg/mL) levels (HR 0.174, 95% CI 0.045-0.676, p = 0.011), and REVEAL 2.0 score < 7 (HR 0.162, 95% CI 0.049-0.541, p = 0.003). These findings suggest that transition from parenteral prostanoids to selexipag carries the risk of clinical deterioration and should only be considered in carefully selected, low-risk patients.

Pulmonary arterial hypertension (PAH) is a chronic disorder with high fatality rates, and its progression is highly associated with the genetic background. Alongside pathogenic variants in genes central to the BMP/TGF-β signaling pathway, recent evidence has linked aquaporin 1 (AQP1) gene variants to PAH. While BMP9 shows promise as a PAH therapy, emerging conflicting evidence challenges this prospect. Herein, we modulated the gene expression of AQP1 and TGFB1 and examined their effect, before and after BMP9 administration, on BMP9, BMP10, BMPR2, AQP1, TGFBR1, and TGFB1 in human pulmonary microvascular endothelial cells (HPMECs) in vitro. Our results demonstrated that silencing of the AQP1 gene resulted in decreased BMPR2 mRNA and protein, downregulated TGFB1 and TGFBR1 mRNA, while tending to reduce TGFBR1 protein levels. BMP9 exogenous administration affected only TGFB1 mRNA, restoring control levels. Silencing of the TGFB1 gene downregulated BMPR2 mRNA and protein levels and affected the expression of its ligands; BMP9 mRNA and protein increased, while BMP10 mRNA levels decreased. Exogenous BMP9 treatment of TGFB1-silenced cells decreased AQP1 mRNA and protein levels. Our results indicate that modulation of AQP1 and TGFB1 genes could possibly disrupt the complex signaling pathway, and that the effects of BMP9 may be cell- and context-dependent. Together, these findings could provide a novel perspective on the interactions of the BMP/TGF-β signaling pathway.

Background: Risk stratification is an essential part of evaluating disease severity in patients with pulmonary arterial hypertension (PAH). This study applied the 4-strata COMPERA 2.0 risk model to the Phase 3 PATENT-1/ 2 studies of riociguat. Methods: This was a post hoc analysis of PATENT-1 and PATENT-2. Log-rank tests of Kaplan-Meier curves were performed to compare the risk strata at PATENT-1 baseline and Week 12 regarding time to clinical worsening and survival at 2 years in the PATENT-2 population. Results: Data on COMPERA 2.0 status at baseline were available for 214 patients with riociguat and 100 with placebo; overall, 120 patients were identified as intermediate-low risk and 96 as intermediate-high risk. At PATENT-1 Week 12, improvements in COMPERA 2.0 risk strata and median 6-min walk distance were seen with riociguat vs placebo in patients assessed as intermediate-low risk and intermediate-high risk at baseline by COMPERA 2.0. More patients improved their COMPERA 2.0 risk status with riociguat vs placebo in the intermediate-low (38 % vs 22 %) and intermediate-high risk groups (42 % vs 31 %). COMPERA 2.0 assessed at PATENT-1 baseline and Week 12 discriminated between risk strata for survival and clinical worsening in PATENT-2 at 2 years (p <= .001 for all analyses). Conclusions: In conclusion, this analysis supports the risk-reduction benefits of riociguat in patients with PAH at intermediate-low risk and intermediate-high risk, and externally validated the utility of COMPERA 2.0 in the long-term risk assessment of patients from a clinical trial population.

Introduction In pulmonary arterial hypertension (PAH) and distal chronic thromboembolic pulmonary hypertension (CTEPH), the consistent use of disease-specific therapies is crucial. We aimed to investigate medication adherence to oral disease-specific medication and the impact on clinical outcome among patients with PAH or CTEPH to identify potential patient-related reasons for treatment incompliance.Study design and methods This prospective study focused on medication adherence using a multimeasure approach, including specialty pharmacy order data to calculate medication possession ratio (MPR) and self-reporting via questionnaire among patients with PAH or CTEPH. Adherence rates of ≥80% were considered adherent. Simplified four-strata risk categories according to the 2022 European Respiratory Society/European Society of Cardiology pulmonary hypertension (PH) guidelines were determined.Results We included 93 patients (66% women, 75% PAH, 25% CTEPH, 57±17 years), all on PH-targeted oral medication between 2013 and 2023. Overall, a number of 73 patients (78%) were classified as adherent. The mean MPR was 98±19% and the mean value of questionnaire responses was 89±10%. At the end of the observation period, adherent patients improved their risk category, while non-adherent patients did not. Factors associated with adherence were older age (OR=1.03, 95% CI=1.01 to 1.07) and being classified in a higher risk category (OR=2.13; 95% CI=1.11 to 4.64). Patients with adverse drug reactions were 75% more likely to be non-adherent to medication (OR=0.25; 95% CI=0.08 to 0.77).Conclusion In this collective, mean MPR and self-reported adherence were overall high, with 78% of patients classified as adherent. Adherent patients improved clinical outcomes contrary to non-adherent patients. Insufficient adherence and potential contributing factors should be regularly considered, especially in patients without improvement after starting disease-specific therapy.

Pulmonary arterial hypertension (PAH) frequently is associated with an imbalance in antiproliferative bone morphogenic protein-2 receptor signaling and proproliferative type-II activin receptor signaling, favoring the latter. Sotatercept is an activin ligand trap that reduces the dominant detrimental activin signaling and provides clinical benefit. We report a patient with heritable PAH in whom sotatercept had neither positive nor negative effects; we relate that fact to his PAH being caused by a previously unreported variant of unknown significance (c.1276T>C, p.[Cys426Arg]) in the GDF2 gene. GDF2 encodes bone morphogenic protein type-9, the presence of which is required for proper functioning of the pulmonary microvasculature. Low levels of functionally active bone morphogenic protein type-9 contribute to PAH. As we enter an era of precision medicine for patients with PAH with increasingly costly therapies, genetic screening may direct appropriate therapy and limit the use of expensive but likely ineffective therapies.

Endothelin-1 (ET-1) is a potent vasoconstrictor produced by endothelial cells and cleared from circulating blood mainly in the pulmonary vasculature. In a healthy pulmonary circulation, the rate of local production of ET-1 is less than its rate of clearance. In the present study, we aimed to investigate whether the abnormal pulmonary circulatory handling of ET-1 relates to poor clinical outcomes in patients with coronavirus disease 2019 (COVID-19)-induced acute respiratory distress syndrome (ARDS). To this end, central venous and systemic arterial ET-1 plasma levels were simultaneously measured on Days 1 and 3 following ICU admission in mechanically ventilated COVID-19 patients with ARDS (COVID-19 ARDS, N = 18). Central venous and systemic arterial ET-1 plasma levels were also measured in two distinct SARS-CoV-2-negative mechanically ventilated critically ill patient groups, matched for age, sex, and critical illness severity, with ARDS (non-COVID-19 ARDS, N = 14) or without ARDS (non-COVID-19 non-ARDS, N = 20). Upon ICU admission, COVID-19-induced ARDS patients had higher systemic arterial and central venous ET-1 levels compared to the non-COVID-19 ARDS and non-COVID-19 non-ARDS patients (p < 0.05), yet a normal systemic arterial:central venous (A:V) ET-1 ratio [0.63 (0.49–1.02)], suggesting that pulmonary ET-1 clearance is intact in these patients. On the other hand, the non-COVID-19 ARDS patients demonstrated abnormal ET-1 handling [A:V ET-1 ratio 1.06 (0.93–1.20)], while the non-COVID-19 non-ARDS group showed normal ET-1 handling [0.79 (0.52–1.11)]. On Day 3, the A:V ratio in all three groups was <1. When the COVID-19 ARDS patients were divided based on 28-day ICU mortality, while their systemic arterial and central venous levels did not differ, the A:V ET-1 ratio was statistically significantly higher upon ICU admission in the non-survivors [0.95 (0.78–1.34)] compared to the survivors [0.57 (0.48–0.92), p = 0.027]. Our results highlight the potential importance of ET-1 as both a biomarker and a therapeutic target in critically ill COVID-19 patients. The elevated A:V ET-1 ratio in non-survivors suggests that the early disruption of pulmonary ET-1 handling may be a key marker of poor prognosis.

Background: The number of pulmonary arterial hypertension (PAH) patients with comorbidities is increasing, however, there are few published data from these patients in PAH therapy clinical trials meaning that evidence-based treatment recommendations have not been made. Aim: This post-hoc analysis of pooled riociguat clinical trial data assessed the impact of riociguat in patients with PAH and comorbidities. Methods: All interventional studies of riociguat in patients with PAH (PATENT-1, PATENT PLUS, RESPITE, MOTION, REPLACE, and the Phase II study) were included in the pooled analysis. The safety of riociguat and placebo was assessed in patients with ≥3 comorbidities vs <3 comorbidities. Safety was assessed by adverse events (AEs) and serious AEs (SAEs). Comorbidities included: age ≥65 years, body mass index ≥30 kg/m 2 , history of essential hypertension, diabetes mellitus, history of significant coronary artery disease, and atrial fibrillation. Results: The 609 patients who received riociguat and 132 patients who received placebo in the main phase clinical trials of riociguat were included in the analysis. Of these, 113 patients (19%) in the riociguat group and 21 patients (16%) in the placebo group had ≥3 comorbidities. In both treatment groups, AE rates were higher in patients with ≥3 comorbidities vs <3 comorbidities (riociguat 93% vs 86%; placebo 95% vs 84%); with most AEs being mild or moderate. Study drug-related AE rates were similar in both treatment groups and in patients with ≥3 comorbidities vs <3 comorbidities (riociguat 54% vs 56%; placebo 52% vs 52%). SAE rates were higher in riociguat-treated patients with ≥3 comorbidities vs <3 comorbidities (25% vs 12%); of these, 4% and 3% were study drug-related, respectively. In patients with ≥3 comorbidities, study drug-related SAE rates were higher in those receiving placebo vs riociguat (10% vs 4%). AE rates leading to study drug discontinuation were higher in patients with ≥3 comorbidities vs <3 comorbidities (riociguat 6% vs 4%; placebo 10% vs 6%), whereas AE rates leading to death were similar in both groups (riociguat 2% vs 1%; placebo 0% vs 4%). Conclusion: These data suggest that riociguat had an acceptable tolerability profile in PAH patients with comorbidities with most AEs being mild or moderate.

Background The role of serotonin in pulmonary arterial hypertension has been extensively studied in recent decades, with preclinical data strongly indicating involvement in disease pathogenesis; however, clinical studies have yielded mixed results. Methods ELEVATE-2 was a phase 2b dose-ranging, randomised, double-blind, placebo-controlled, multicentre trial investigating rodatristat ethyl as a treatment for patients with pulmonary arterial hypertension. The study was conducted at 64 sites across 16 countries in Europe and North America. Eligible participants were aged 18 years or older, had pulmonary arterial hypertension with WHO functional class II or III symptom severity, and had received a stable dose and regimen of one or more pulmonary arterial hypertension treatments for at least 12 weeks. Participants were randomly assigned 1:1:1 to receive two placebo tablets, one placebo and one rodatristat ethyl 300 mg tablet, or two rodatristat ethyl 300 mg tablets twice daily using an interactive response system. Participants, investigators, site personnel, and sponsors were masked to treatment allocation. Participants who completed the 24 week treatment period were invited to continue in an open-label extension. The primary endpoint was percent change in pulmonary vascular resistance (PVR) from baseline to week 24. Primary efficacy analyses were conducted on the intention-to-treat population and analyses of harms were conducted in the safety population, which included all patients who received any amount of the study drug. This trial is registered with ClinicalTrials.gov, NCT04712669, and is now complete. Findings Between March 18, 2021 and Dec 13, 2022, 108 participants were enrolled and randomly assigned. 36 participants received placebo, 36 received rodatristat ethyl 300 mg, and 36 received rodatristat ethyl 600 mg twice daily. Overall, 85 (79%) of participants were female and 23 (21%) were male. The mean age was 52·8 years (SD 14·7) in the full analysis set. In the open-label extension phase, 62 (82%) of participants were female and 14 (18%) were male, and the mean age was 52·8 years (SD 14·7); this phase was terminated following sponsor review of unmasked main study results. Least-squares mean percent change in PVR from baseline to week 24 favoured placebo and was 5·8% (SE 18·1) for the placebo group, 63·1% (18·5) for the rodatristat ethyl 300 mg group, and 64·2% (18·0) for the rodatristat ethyl 600 mg group. Treatment-emergent adverse events (TEAE) were reported for 29 (81%) patients in the placebo group, 33 (92%) patients in the rodatristat ethyl 300 mg group, and all 36 (100%) patients in the rodatristat ethyl 600 mg group. TEAE leading to study discontinuation were reported for three (8%) patients in the placebo group, four (11%) patients in the rodatristat ethyl 300 mg group, and four (11%) in the rodatristat ethyl 600 mg group. There was one (3%) TEAE leading to death in the rodatristat ethyl 300 mg group. Interpretation Our results indicate that reducing peripheral serotonin concentrations via rodatristat ethyl has a negative effect on pulmonary haemodynamics and cardiac function in patients with pulmonary arterial hypertension. This finding suggests that manipulating this pathway might not be a suitable option for pulmonary arterial hypertension therapy. Funding Enzyvant Therapeutics (now Sumitomo Pharma America).

Care of pulmonary hypertension (PH) patients in special situations requires insightful knowledge of the pathophysiology of the cardiopulmonary system and close interaction with different specialists, depending on the situation. The role of this task force was to gather knowledge about five conditions that PH patients may be faced with. These conditions are 1) perioperative care; 2) management of pregnancy; 3) medication adherence; 4) palliative care; and 5) the influence of climate on PH. Many of these aspects have not been covered by previous World Symposia on Pulmonary Hypertension. All of the above conditions are highly affected by psychological, geographical and socioeconomic factors, and share the need for adequate healthcare provision. The task force identified significant gaps in information and research in these areas. The current recommendations are based on detailed literature search and expert opinion. The task force calls for further studies and research to better understand and address the special circumstances that PH patients may encounter.

Pulmonary arterial hypertension (PAH) is a chronic disease characterized by a progressive increase in mean pulmonary arterial pressure. Mutations in the BMPR2 and AQP1 genes have been described in familial PAH. The bone morphogenetic proteins BMP9 and BMP10 bind with high affinity to BMPR2. Administration of BMP9 has been proposed as a potential therapeutic strategy against PAH, although recent conflicting evidence dispute the effect of such a practice. Considering the involvement of the above molecules in PAH onset, progression, and therapeutic value, we examined the effects of modulation of BMP9, BMPR2, and AQP1 on BMP9, BMP10, BMPR2, AQP1, and TGFB1 expression in human pulmonary microvascular endothelial cells in vitro. Our results demonstrated that silencing the BMPR2 gene resulted in increased expression of its two main ligands, namely BMP9 and BMP10. Exogenous administration of BMP9 caused the return of BMP10 to basal levels, while it restored the decreased AQP1 protein levels and the decreased TGFB1 mRNA and protein expression levels caused by BMPR2 silencing. Moreover, AQP1 gene silencing also resulted in increased expression of BMP9 and BMP10. Our results might possibly imply that the effect of exogenously administered BMP9 on molecules participating in the BMP signaling pathway could depend on the expression levels of BMPR2. Taken together, these results may provide insight into the highly complex interactions of the BMP signaling pathway.

In Riociguat rEplacing PDE5i therapy evaLuated Against Continued PDE5i thErapy (REPLACE) (NCT02891850), improvements in risk status were observed in patients with pulmonary arterial hypertension (PAH) at intermediate risk switching to riociguat versus continuing phosphodiesterase-5 inhibitors (PDE5i). This post hoc study applied the Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL) Lite 2 and Comparative Prospective Registry of Newly Initiated Therapies for Pulmonary (COMPERA) 2.0 risk-assessment tools to REPLACE to investigate the impact of baseline risk status on clinical improvement. The proportions of riociguat- and PDE5i-treated patients achieving the primary end-point at REVEAL Lite 2 low, intermediate, and high baseline risk reflected the overall population. Proportions of riociguat-treated patients achieving the primary end-point were comparable between the COMPERA 2.0 intermediate-low risk (39%) and intermediate-high risk (43%) groups. Our findings show that patients in REPLACE achieved clinical improvement by switching from PDE5i to riociguat across all COMPERA 2.0 and most REVEAL Lite 2 baseline risk strata. J Heart Lung Transplant 2024;43:1756-1760 (c) Published by Elsevier Inc. on behalf of International Society for Heart and Lung Transplantation.

Background: The 2022 ESC/ERS treatment guidelines for pulmonary arterial hypertension (PAH) recommend using a four-strata risk assessment strategy at follow-up. COMPERA 2.0 is a refined four-strata risk assessment tool that subdivides patients at intermediate risk of mortality at 1 year into intermediate-low and intermediate-high risk groups for a more granular approach to risk prediction. Aim: This post-hoc analysis applied COMPERA 2.0 to the PATENT studies of riociguat in patients with PAH. Methods: COMPERA 2.0 was applied to patients who were pretreated with PAH therapy at PATENT-1 entry. Patients with missing data for COMPERA 2.0 variables were excluded. In PATENT-1, risk strata were assessed at baseline and Week 12; and 6-minute walking distance (6MWD) at Week 12 was analyzed by risk strata at baseline. All pretreated patients entering the PATENT-2 open-label extension were included in Kaplan-Meier analyses to assess association of risk strata at PATENT-1 baseline and Week 12 with clinical worsening and survival. Results: At PATENT-1 baseline (riociguat 2.5 mg n=102, placebo n=49), more patients were at intermediate-low risk than intermediate-high risk (Figure 1). At PATENT-1 Week 12, a higher proportion of patients were at low risk with riociguat vs placebo (Figure 1). At PATENT-1 Week 12, the following mean [SD] changes in 6MWD were seen in patients at intermediate-low risk (riociguat 24 m [57 m], placebo 10 m [60 m]) and intermediate-high risk (riociguat 34 m [56 m], placebo –2 m [70 m]) by COMPERA 2.0 at baseline. COMPERA 2.0 assessed at PATENT-1 baseline and Week 12 was able to discriminate between risk strata for clinical worsening and survival in PATENT-2 (n=167, log-rank tests: p≤0.001 for all analyses). Conclusion: This analysis confirmed the risk-reduction benefits of riociguat in patients with PAH and validated the utility of COMPERA 2.0 in the long-term risk assessment of patients from a clinical trial population.