Imatinib mesylate as add-on therapy for pulmonary arterial hypertension: results of the randomized IMPRES study

Seralutinib in adults with pulmonary arterial hypertension (TORREY): a randomised, double-blind, placebo-controlled phase 2 trial

BACKGROUND

Morbidity and mortality in pulmonary arterial hypertension (PAH) remain high. Activation of platelet-derived growth factor receptor, colony stimulating factor 1 receptor, and mast or stem cell growth factor receptor kinases stimulates inflammatory, proliferative, and fibrotic pathways driving pulmonary vascular remodelling in PAH. Seralutinib, an inhaled kinase inhibitor, targets these pathways. We aimed to evaluate the efficacy and safety of seralutinib in patients with PAH receiving standard background therapy.

METHODS

The TORREY trial was a phase 2, randomised, multicentre, multinational, double-blind, placebo-controlled study. Patients with PAH from 40 hospital and community sites were randomly assigned 1:1 via interactive response technologies to receive seralutinib (60 mg twice daily for 2 weeks, then increased to 90 mg twice daily as tolerated) or placebo by dry powder inhaler twice daily for 24 weeks. Randomisation was stratified by baseline pulmonary vascular resistance (PVR; <800 dyne·s/cm5 and ≥800 dyne·s/cm5). Patients were eligible if classified as WHO Group 1 PH (PAH), WHO Functional Class II or III, with a PVR of 400 dyne·s/cm5 or more, and a 6 min walk distance of between 150 m and 550 m. The primary endpoint was change in PVR from baseline to 24 weeks. Analyses for efficacy endpoints were conducted in randomly assigned patients (intention-to-treat population). Safety analyses included all patients who received the study drug. TORREY was registered with ClinicalTrials.gov (NCT04456998) and EudraCT (2019-002669-37) and is completed.

FINDINGS

From Nov 12, 2020, to April 20, 2022, 151 patients were screened for eligibility, and following exclusions, 86 adults receiving PAH background therapy were randomly assigned to seralutinib (n=44; four male, 40 female) or placebo (n=42; four male, 38 female), and comprised the intention-to-treat population. At baseline, treatment groups were balanced except for a higher representation of WHO Functional Class II patients in the seralutinib group. The least squares mean change from baseline to week 24 in PVR was 21·2 dyne·s/cm5 (95% CI -37·4 to 79·8) for the placebo group and -74·9 dyne·s/cm5 (-139·7 to -10·2) for the seralutinib group. The least squares mean difference between the seralutinib and placebo groups for change in PVR was -96·1 dyne·s/cm5 (95% CI -183·5 to -8·8; p=0·03). The most common treatment-emergent adverse event in both treatment groups was cough: 16 (38%) of 42 patients in the placebo group; 19 (43%) of 44 patients in the seralutinib group.

INTERPRETATION

Treatment with inhaled seralutinib significantly decreased PVR, meeting the primary endpoint of the study among patients receiving background therapy for PAH.

FUNDING

Gossamer Bio.

Comparative analysis of antiproliferative and vasodilator effects of drugs for pulmonary hypertension: Extensive in vitro study in rats and human

An effective pulmonary hypertension (PH) treatment should combine antiproliferative and vasodilator effects. We characterized a wide-range of drugs comparing their anti-proliferative vs vasodilator effects in human and rat pulmonary artery smooth muscle cells (PASMC). Key findings: 1) Approved PH drugs (PDE5 inhibitors, sGC stimulators and PGI2 agonists) are preferential vasodilators. 2) cGMP stimulators were more effective in cells derived from hypertensive rats. 3) Nifedipine acted equally as vasodilator and antiproliferative. 4) quercetin and imatinib were potent dual vasodilator/antiproliferative drugs. 5) Tacrolimus and levosimendan lacked antiproliferative effects. 6) Forskolin, pinacidil and hydroxyfasudil were more effective as antiproliferative in human cells.

Future Perspectives of Pulmonary Arterial Hypertension: A Review of Novel Pipeline Treatments and Indications

Pulmonary arterial hypertension is characterized by elevated blood pressure and pathological changes in the pulmonary arterioles, leading to the development of right-heart failure and potentially fatal outcomes if left untreated. This review aims to provide an overview of novel drugs or formulations and new drug indications for pulmonary arterial hypertension that are currently in phases II-III of randomized controlled trials, and describe the rationale for the use of these targeted therapies, as well as their efficacy, safety profile, and impact on quality of life and survival. The literature research was conducted using data from ClinicalTrials.gov for the period between 1 January 2016 up to 31 December 2022. The population of interest includes individuals aged ≥ 18 years who have been diagnosed with pulmonary arterial hypertension. The review selection criteria included trials with recruiting, enrolling by invitation, active, terminated or completed status in 2022 and 2023. A total of 24 studies were selected for evaluation based on the inclusion and exclusion criteria. This review summarizes the updated information from randomized clinical trials involving novel therapies for pulmonary arterial hypertension. However, larger clinical trials are required to validate their clinical safety and effects. In the future, clinicians should choose therapies based on the patient's individual situation and requirements when developing treatment strategies.

Pharmacological Update and Emerging Treatments of Pulmonary Hypertension

Pulmonary hypertension (PH) is defined as elevated pressures in the pulmonary artery and is associated with significant morbidity and mortality. The World Health Organization classifies PH into 5 distinct groups based on underlying etiology, pathology, and modality of treatment. Therapeutic approach may be challenging due to the extensive spectrum of causes and underlying mechanisms mediating PH. The 5 groups include pulmonary arterial hypertension (group 1), PH secondary to left heart disease (group 2), PH secondary to chronic lung disease (group 3), chronic thromboembolic pulmonary hypertension (group 4), and PH due to miscellaneous causes (group 5). Although significant progress has been made in the treatment of group 1 PH, there is a continued need to develop new therapies for all types of PH. Additionally, most treatments currently available improve functional capacity and symptoms but without a significant benefit in mortality. In this review, we aim to describe the various etiologies of PH and their established pharmacotherapies, as well as expand on emerging therapeutic options for each group.

BMPR2 mutation and clinical response to imatinib in a case of heritable pulmonary arterial hypertension

Bone morphogenetic protein receptor 2 (BMPR2) mutation is the most common gene mutation implicated in the pathogenesis of pulmonary arterial hypertension (PAH). We describe, for the first time, an excellent clinical response to tyrosine kinase inhibitor imatinib in a patient with heritable PAH from BMPR2 mutation.

IMPAHCT: A randomized phase 2b/3 study of inhaled imatinib for pulmonary arterial hypertension

AV-101 (imatinib) powder for inhalation, an investigational dry powder inhaled formulation of imatinib designed to target the underlying pathobiology of pulmonary arterial hypertension, was generally well tolerated in healthy adults in a phase 1 single and multiple ascending dose study. Inhaled Imatinib Pulmonary Arterial Hypertension Clinical Trial (IMPAHCT; NCT05036135) is a phase 2b/3, randomized, double-blind, placebo-controlled, dose-ranging, and confirmatory study. IMPAHCT is designed to identify an optimal AV-101 dose (phase 2b primary endpoint: pulmonary vascular resistance) and assess the efficacy (phase 3 primary endpoint: 6-min walk distance), safety, and tolerability of AV-101 dose levels in subjects with pulmonary arterial hypertension using background therapies. The study has an operationally seamless, adaptive design allowing for continuous recruitment. It includes three parts; subjects enrolled in Part 1 (phase 2b dose-response portion) or Part 2 (phase 3 intermediate portion) will be randomized 1:1:1:1 to 10, 35, 70 mg AV-101, or placebo (twice daily), respectively. Subjects enrolled in Part 3 (phase 3 optimal dose portion) will be randomized 1:1 to the optimal dose of AV-101 and placebo (twice daily), respectively. All study parts include a screening period, a 24-week treatment period, and a 30-day safety follow-up period; the total duration is ∼32 weeks. Participation is possible in only one study part. IMPAHCT has the potential to advance therapies for patients with pulmonary arterial hypertension by assessing the efficacy and safety of a novel investigational drug-device combination (AV-101) using an improved study design that has the potential to save 6-12 months of development time. ClinicalTrials.gov Identifier: NCT05036135.

Current Management and Future Directions for Pulmonary Arterial Hypertension Associated with Congenital Heart Disease

Current management of patients with congenital heart disease has increased their survival into adulthood. This is accompanied by potential cardiac complications, including pulmonary hypertension associated with congenital heart disease (PAH-CHD). PAH-CHD constitutes a challenging subgroup of pulmonary hypertension and requires expert management to improve quality of life and prognosis. Novel agents have shown a significant improvement in morbidity and mortality in patients with pulmonary arterial hypertension. However, the long-term effects of these medications on PAH-CHD patients remain somewhat uncertain, necessitating treatment plans largely founded on the clinical experience of the healthcare providers. The aim of this review is to summarize the current evidence and future perspectives regarding treatment strategies for PAH-CHD to help better guide management of this complex disease.

Pulmonary hypertension associated with diazoxide: the SUR1 paradox

The ATP-sensitive potassium channels and their regulatory subunits, sulfonylurea receptor 1 (SUR1/Kir6.2) and SUR2/Kir6.1, contribute to the pathophysiology of pulmonary hypertension (PH). Loss-of-function pathogenic variants in the ABCC8 gene, which encodes for SUR1, have been associated with heritable pulmonary arterial hypertension. Conversely, activation of SUR1 and SUR2 leads to the relaxation of pulmonary arteries and reduces cell proliferation and migration. Diazoxide, a SUR1 activator, has been shown to alleviate experimental PH, suggesting its potential as a therapeutic option. However, there are paradoxical reports of diazoxide-induced PH in infants. This review explores the role of SUR1/2 in the pathophysiology of PH and the contradictory effects of diazoxide on the pulmonary vascular bed. Additionally, we conducted a comprehensive literature review of cases of diazoxide-associated PH and analysed data from the World Health Organization pharmacovigilance database (VigiBase). Significant disproportionality signals link diazoxide to PH, while no other SUR activators have been connected with pulmonary vascular disease. Diazoxide-associated PH seems to be dose-dependent and potentially related to acute effects on the pulmonary vascular bed. Further research is required to decipher the differing pulmonary vascular consequences of diazoxide in different age populations and experimental models.

[Genetic diagnostics and molecular approaches in pulmonary arterial hypertension]

The recently published new European guidelines for diagnosis and treatment of pulmonary hypertension now offer the so far most extensive description of genetic testing and counselling for pulmonary arterial hypertension patients. In addition, the importance of a clinical screening of healthy mutation carriers is highlighted as well as the genetic testing of patients with a suspicion of pulmonary veno-occlusive disease. We frame the respective parts of the guidelines on genetic testing and counselling in the context of recent data and provide comments. Finally, we give an outlook on novel molecular approaches starting from Sotatercept, addressing ion channels and novel therapeutic developments.

Recent Advances in the Treatment of Pulmonary Arterial Hypertension Associated with Connective Tissue Diseases

Pulmonary hypertension (PH) is a severe vascular complication of connective tissue diseases (CTD). Patients with CTD may develop PH belonging to diverse groups: (1) pulmonary arterial hypertension (PAH), (2) PH due to left heart disease, (3) secondary PH due to lung disease and/or hypoxia and (4) chronic thromboembolic pulmonary hypertension (CTEPH). PAH most often develops in systemic scleroderma (SSc), mostly in its limited variant. PAH-CTD is a progressive disease characterized by poor prognosis. Therefore, early diagnosis should be established. A specific treatment for PAH-CTD is currently available and recommended: prostacyclin derivative (treprostinil, epoprostenol, iloprost, selexipag), nitric oxide and natriuretic pathway: stimulators of soluble guanylate cyclase (sGC: riociguat) and phosphodiesterase-five inhibitors (PDE5i: sildenafil, tadalafil), endothelin receptor antagonists (ERA: bosentan, macitentan, ambrisentan). Moreover, novel drugs, e.g., sotatercept, have been intensively investigated in clinical trials. We aim to review the literature on recent advances in the treatment strategy and prognosis of patients with PAH-CTD. In this manuscript, we discuss the mechanism of action of PAH-specific drugs and new agents and the latest research conducted on PAH-CTD patients.

Pulmonary hypertension associated with lung disease: new insights into pathomechanisms, diagnosis, and management

Patients with chronic lung diseases, particularly interstitial lung disease and chronic obstructive pulmonary disease, frequently develop pulmonary hypertension, which results in clinical deterioration, worsening of oxygen uptake, and an increased mortality risk. Pulmonary hypertension can develop and progress independently from the underlying lung disease. The pulmonary vasculopathy is distinct from that of other forms of pulmonary hypertension, with vascular ablation due to loss of small pulmonary vessels being a key feature. Long-term tobacco exposure might contribute to this type of pulmonary vascular remodelling. The distinct pathomechanisms together with the underlying lung disease might explain why treatment options for this condition remain scarce. Most drugs approved for pulmonary arterial hypertension have shown no or sometimes harmful effects in pulmonary hypertension associated with lung disease. An exception is inhaled treprostinil, which improves exercise capacity in patients with interstitial lung disease and pulmonary hypertension. There is a pressing need for safe, effective treatment options and for reliable, non-invasive diagnostic tools to detect and characterise pulmonary hypertension in patients with chronic lung disease.

Pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare and progressive disease characterised by remodelling of the pulmonary arteries and progressive narrowing of the pulmonary vasculature. This leads to a progressive increase in pulmonary vascular resistance and pulmonary arterial pressure and, if left untreated, to right ventricular failure and death. A correct diagnosis requires a complete work-up including right heart catheterisation performed in a specialised centre. Although our knowledge of the epidemiology, pathology and pathophysiology of the disease, as well as the development of innovative therapies, has progressed in recent decades, PAH remains a serious clinical condition. Current treatments for the disease target the three specific pathways of endothelial dysfunction that characterise PAH: the endothelin, nitric oxide and prostacyclin pathways. The current treatment algorithm is based on the assessment of severity using a multiparametric risk stratification approach at the time of diagnosis (baseline) and at regular follow-up visits. It recommends the initiation of combination therapy in PAH patients without cardiopulmonary comorbidities. The choice of therapy (dual or triple) depends on the initial severity of the condition. The main treatment goal is to achieve low-risk status. Further escalation of treatment is required if low-risk status is not achieved at subsequent follow-up assessments. In the most severe patients, who are already on maximal medical therapy, lung transplantation may be indicated. Recent advances in understanding the pathophysiology of the disease have led to the development of promising emerging therapies targeting dysfunctional pathways beyond endothelial dysfunction, including the TGF-β and PDGF pathways.

Pharmacotherapy of refractory pulmonary arterial hypertension

INTRODUCTION

Treatment of refractory pulmonary arterial hypertension (PAH) is challenging and rarely the focus of reviews. The purpose of this review is to discuss current treatment options of refractory PAH, along with the state of research of several new medications.

AREAS COVERED

We conducted a comprehensive PubMed search on the relevant literature on treating PAH, with a focus on approved and investigational interventions for high-risk patients. Our strategy used keywords 'Treatment' AND 'Pulmonary Hypertension,' without date restrictions, ensuring a thorough survey of available literature for our review.

EXPERT OPINION

By utilizing serial risk assessment to identify patients remaining intermediate or high-risk, more patients are likely to survive longer. This is done by earlier use of combination or triple therapy with prostacyclin drugs. Current medications for PAH are all essentially vasodilators that improve physiology, but do not truly modify the disease process. The potential application of new investigational medications is exciting as they work by novel pathways likely to change the landscape of refractory PAH treatment.

Treatment of pulmonary arterial hypertension: recent progress and a look to the future

Pulmonary arterial hypertension (PAH) is a severe but treatable form of pre-capillary pulmonary hypertension caused by pulmonary vascular remodelling. As a result of basic science discoveries, randomised controlled trials, studies of real-world data, and the development of clinical practice guidelines, considerable progress has been made in the treatment options and outcomes for patients with PAH, underscoring the importance of seamless translation of information from bench to bedside and, ultimately, to patients. However, PAH still carries a high mortality rate, which emphasises the urgent need for transformative innovations in the field. In this Series paper, written by a group of clinicians, researchers, and a patient with PAH, we review therapeutic approaches and treatment options for PAH. We summarise current knowledge of the cellular and molecular mechanisms of PAH, with an emphasis on emerging treatable pathways and optimisation of current management strategies. In considering future directions for the field, our ambition is to identify therapies with the potential to stall or reverse pulmonary vascular remodelling. We highlight novel therapeutic approaches, the important role of patients as partners in research, and innovative approaches to PAH clinical trials.

Pharmacology and Rationale for Seralutinib in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex disorder characterized by vascular remodeling and a consequent increase in pulmonary vascular resistance. The histologic hallmarks of PAH include plexiform and neointimal lesions of the pulmonary arterioles, which are composed of dysregulated, apoptosis-resistant endothelial cells and myofibroblasts. Platelet-derived growth factor receptors (PDGFR) α and β, colony stimulating factor 1 receptor (CSF1R), and mast/stem cell growth factor receptor kit (c-KIT) are closely related kinases that have been implicated in PAH progression. In addition, emerging data indicate significant crosstalk between PDGF signaling and the bone morphogenetic protein receptor type 2 (BMPR2)/transforming growth factor β (TGFβ) receptor axis. This review will discuss the importance of the PDGFR-CSF1R-c-KIT signaling network in PAH pathogenesis, present evidence that the inhibition of all three nodes in this kinase network is a potential therapeutic approach for PAH, and highlight the therapeutic potential of seralutinib, currently in development for PAH, which targets these pathways.

Medical Management of Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

PURPOSE OF REVIEW

The purpose of this review is to overview the most relevant and recent knowledge regarding medical management in pulmonary arterial hypertension (PAH).

RECENT FINDINGS

Evidence has shown that PAH patients' quality of life and prognosis depend on the capability of the RV to adapt to increased afterload and to fully recover in response to substantially reduced pulmonary vascular resistance obtained with medical therapy. Data from recent clinical studies show that more aggressive treatment strategies, especially in higher risk categories, determine larger afterload reductions, consequentially increasing the probability of achieving right heart reverse remodeling, therefore improving the patients' survival and quality of life. Remarkable progress has been observed over the past decades in the medical treatment of PAH, related to the development of drugs that target multiple biological pathways, strategies for earlier and more aggressive treatment interventions. New hopes for treatment of patients who are unable to achieve low-risk status have been derived from the phase 2 trial PULSAR and the phase 3 trial STELLAR, which show improvement in the hemodynamic status of patients treated with sotatercept on top of background therapy. Promising results are expected from several ongoing clinical trials targeting new pathways involved in the pathophysiology of PAH.

Refined risk stratification, current treatment, and new therapeutic approaches in pulmonary arterial hypertension

The 2022 European Society of Cardiology/European Respiratory Society (ESC/ERS) guidelines for pulmonary hypertension have introduced a refined risk stratification to guide both initial and subsequent treatment of pulmonary arterial hypertension (PAH). The risk stratification at PAH diagnosis still comprises three risk categories (low, intermediate, high) and lists some new parameters. As the estimated 1‑year mortality is more than 20% in high-risk patients after diagnosis, an initial triple-combination therapy including parenteral prostacyclin analogues is recommended for this group. All other patients should receive a dual-combination therapy with an endothelin receptor antagonist and a phosphodiesterase‑5 inhibitor. However, this approach of initial combination therapy is only recommended for classic PAH, while monotherapy followed by regular follow-up and individualized therapy should be used for patients with cardiopulmonary comorbidities. For PAH patients without cardiopulmonary comorbidities, it is recommended to assess their risk at follow-up with a new 4‑strata classification, where the intermediate-risk group is split on the basis of three noninvasive parameters. Importantly, changes from intermediate-high to intermediate-low risk have been shown to be associated with a better prognosis. In addition, the recommendations on treatment escalation became more precise with the addition of a prostacyclin receptor agonist or switching a phosphodiesterase‑5 inhibitor to a soluble guanylate cyclase stimulator for intermediate-low risk and proceeding to triple-combination therapy with parenteral prostacyclin analogues already for intermediate-high risk. With sotatercept, the first non-vasodilator PAH treatment will become available in the near future to further enrich our treatment options for this chronic and still severe disease.

Pulmonary tumor thrombotic microangiopathy: Exploration into current diagnostic aids and therapeutics

Pulmonary tumor thrombotic microangiopathy (PTTM) is an under-recognized cause of pulmonary hypertension and fulminant right ventricle failure. It is associated with a high mortality due to delay in diagnosis. We present two cases of PTTM, both diagnosed postmortem, highlighting the importance of timely identification and initiation of treatment for this near-fatal condition.

Pulmonary hypertension inhaled therapies: An updated review

Treatments of pulmonary hypertension (PH) continue to evolve with approval of new therapies. The currently FDA approved inhaled PH therapies include inhaled iloprost for group 1 pulmonary arterial hypertension (PAH), inhaled treprostinil solution and treprostinil dry powder inhaler for both group 1 PAH and group 3 PH associated with interstitial lung disease (PH-ILD). Inhaled treprostinil was recently approved for group 3 PH-ILD based on the results of INCREASE trial and the newer formulation of treprostinil dry powder that comes with a new inhaler was recently approved for both group 1 PAH and group 3 PH-ILD based on BREEZE study. The pipeline for inhaled PH therapies includes several promising molecules that can enrich the current PH therapeutic era and mitigate several systemic side effects by directly delivering the drug to the target organ. In this review article we summarize the evidence for the currently approved inhaled PAH/PH therapies, discuss the available inhalation devices, present a roadmap for successful treatment strategy, and present several inhaled PAH/PH therapies in the pipeline.

Emerging pharmacotherapies for the treatment of pulmonary arterial hypertension

INTRODUCTION

Pulmonary arterial hypertension (PAH) is a progressive and life-threatening disease. Approved treatment options currently primarily target abnormal cell signaling pathways involved in vasoconstriction and proliferation, such as those mediated by prostacyclin, cyclic guanosine monophosphate, and endothelin.

AREAS COVERED

Recent advancements have led to new applications and modes of delivery of currently approved PAH medications. At the same time, novel drugs targeting specific molecular pathways involved in PAH pathogenesis have been developed and are being investigated in clinical trials. This review summarizes investigational drug trials for PAH gathered from a comprehensive search using PubMed and ClinicalTrials.gov between 2003 and 2023. It includes both currently approved medications studied at different doses or new administration forms and experimental drugs that have not yet been approved.

EXPERT OPINION

Approved treatments for PAH target imbalances in pulmonary vasoactive pathways that work primarily on enhancing pulmonary vasodilation with less salient effects on pulmonary vascular remodeling. The advent of more locally acting inhaled medications offers additional therapeutic options that may improve the ease of drug delivery and reduce adverse systemic effects. The more recent emphasis on developing and applying therapeutics that directly impact the aberrant signaling pathways implicated in PAH appears more likely to advance the treatment of this devastating disease.

Treatment with imatinib was useful to delay the neointimal hyperplasia of aortocaval fistula in adenine-induced renal failure rats

PURPOSE

The study was conducted to investigate the effect of the treatment with imatinib, a c-kit specific inhibitor, on the neointimal hyperplasia (NIH) of aortocaval fistula (ACF) in adenine-induced renal failure rats.

MATERIALS AND METHODS

All rats were randomly assigned to 4 groups: rats were fed on a normal diet (normal group); rats were fed on a 0.75% adenine-rich diet (renal failure group). The remaining rats underwent ACF after receiving a 0.75% adenine-rich diet and received daily saline gavage (model group) or imatinib gavage (imatinib group) for 7 days after surgery. Immunohistochemical method was used to detect c-kit expression, and Elastomeric Verhoeff-Van Gieson (EVG) staining was used to observe morphological changes of the ACF. The Pearson correlation analysis was used to evaluate the correlations of c-kit expression with intimal thickness and the percentage of stenosis, respectively.

RESULTS

The renal failure group showed positive c-kit expression on the intima of the inferior vena cava (IVC), whereas the normal group did not. Compared to the model group, intimal thickness (P = 0.001), the percentage of stenosis (P = 0.006) and c-kit expression (P = 0.04) were decreased in the imatinib group at 8 weeks postoperatively. C-kit expression was positively correlated with both intimal thickness and percentage of stenosis (intimal thickness: R = 0.650, P = 0.003; the percentage of stenosis: R = 0.581, P = 0.011) in both the model and imatinib groups.

CONCLUSION

Treatment with imatinib, a c-kit specific inhibitor, was useful to delay the NIH of ACF in adenine-induced renal failure rats.

Pulmonary arterial hypertension trials put to the test: Using the fragility index to assess trials robustness

BACKGROUND

Randomized clinical trials (RCTs) are considered the gold standard for evidence-based medicine. The Fragility Index (FI) is a tool to assess the robustness of RCT results. FI was validated for dichotomous outcomes and recent work expanded its use to continuous outcomes. Studying the robustness of RCTs in Pulmonary Arterial Hypertension (PAH) treatments is crucial due to the severity and mortality risks associated with this rare condition.

OBJECTIVES

Analyze FI and Fragility quotient (FQ) of significant primary outcomes in PAH RCTs and study FI correlation with sample size and journal impact factor.

METHODS

FI and FQ calculation followed by Spearman correlation to assess the correlation between FI and sample size, and FI and impact factor.

RESULTS

The median sample size of the 21 trials was 202 patients (IQR 106-267), with 6 trials reporting primary outcomes as dichotomous and 15 reporting continuous primary outcomes. The median FI was 10 (IQR 3-20), and the median FQ was 0.044 (0.026-0.097). A moderate correlation was found between FI and sample size, with r = 0.56; P = 0.008 and FI and journal impact factor (r=0.50; P=0.019). The FI for continuous outcomes was similar to that for dichotomous outcomes.

CONCLUSIONS

This study represents the first analysis of the FI and FQ of PAH treatment RCTs, and expands the use of FI to continuous outcomes in this context. The moderate correlation between FI and sample size suggests that increasing sample size alone is partially correlated to a higher FI. The similarity between FI for continuous and dichotomous outcomes supports the broader use of FI in PAH RCTs.

Pulmonary vascular fibrosis in pulmonary hypertension - The role of the extracellular matrix as a therapeutic target

Pulmonary hypertension (PH) is a condition characterized by changes in the extracellular matrix (ECM) deposition and vascular remodeling of distal pulmonary arteries. These changes result in increased vessel wall thickness and lumen occlusion, leading to a loss of elasticity and vessel stiffening. Clinically, the mechanobiology of the pulmonary vasculature is becoming increasingly recognized for its prognostic and diagnostic value in PH. Specifically, the increased vascular fibrosis and stiffening resulting from ECM accumulation and crosslinking may be a promising target for the development of anti- or reverse-remodeling therapies. Indeed, there is a huge potential in therapeutic interference with mechano-associated pathways in vascular fibrosis and stiffening. The most direct approach is aiming to restore extracellular matrix homeostasis, by interference with its production, deposition, modification and turnover. Besides structural cells, immune cells contribute to the level of ECM maturation and degradation by direct cell-cell contact or the release of mediators and proteases, thereby opening a huge avenue to target vascular fibrosis via immunomodulation approaches. Indirectly, intracellular pathways associated with altered mechanobiology, ECM production, and fibrosis, offer a third option for therapeutic intervention. In PH, a vicious cycle of persistent activation of mechanosensing pathways such as YAP/TAZ initiates and perpetuates vascular stiffening, and is linked to key pathways disturbed in PH, such as TGF-beta/BMPR2/STAT. Together, this complexity of the regulation of vascular fibrosis and stiffening in PH allows the exploration of numerous potential therapeutic interventions. This review discusses connections and turning points of several of these interventions in detail.

Novel Drugs for the Treatment of Pulmonary Arterial Hypertension: Where Are We Going?

Pulmonary arterial hypertension (PAH) is a progressive disease that despite advances in therapy is associated with a 7-year survival of approximately 50%. Several risk factors are associated with developing PAH, include methamphetamine use, scleroderma, human immunodeficiency virus, portal hypertension, and genetic predisposition. PAH can also be idiopathic. There are traditional pathways underlying the pathophysiology of PAH involving nitric oxide, prostacyclin, thromboxane A2, and endothelin-1, resulting in impaired vasodilation, enhanced vasoconstriction and proliferation in the pulmonary vasculature. Established PAH medications targets these pathways; however, this paper aims to discuss novel drugs for treating PAH by targeting new and alternative pathways.

Pursuing functional biomarkers in complex disease: Focus on pulmonary arterial hypertension

A major gap in diagnosis, classification, risk stratification, and prediction of therapeutic response exists in pulmonary arterial hypertension (PAH), driven in part by a lack of functional biomarkers that are also disease-specific. In this regard, leveraging big data-omics analyses using innovative approaches that integrate network medicine and machine learning correlated with clinically useful indices or risk stratification scores is an approach well-positioned to advance PAH precision medicine. For example, machine learning applied to a panel of 48 cytokines, chemokines, and growth factors could prognosticate PAH patients with immune-dominant subphenotypes at elevated or low-risk for mortality. Here, we discuss strengths and weaknesses of the most current studies evaluating omics-derived biomarkers in PAH. Progress in this field is offset by studies with small sample size, pervasive limitations in bioinformatics, and lack of standardized methods for data processing and interpretation. Future success in this field, in turn, is likely to hinge on mechanistic validation of data outputs in order to couple functional biomarker data with target-specific therapeutics in clinical practice.

[Physiopathology and treatment of pulmonary arterial hypertension]

Pulmonary arterial hypertension (PAH) is a rare disease affecting mainly the pre-capillary pulmonary vascular bed. However, some forms of the disease have venous/capillary involvement. It is an obstructive remodelling of the pulmonary arterioles coupled with vascular pruning, increasing right ventricular afterload and leading to right heart failure. PAH has a complex pathogeny that is detailed in this review. Current specific treatments target endothelial dysfunction, and primarily aim at vasodilatation. Promising innovative treatments targeting the pulmonary artery remodelling are under development.

Pathophysiological Involvement of Mast Cells and the Lipid Mediators in Pulmonary Vascular Remodeling

Mast cells are responsible for IgE-dependent allergic responses, but they also produce various bioactive mediators and contribute to the pathogenesis of various cardiovascular diseases, including pulmonary hypertension (PH). The importance of lipid mediators in the pathogenesis of PH has become evident in recent years, as exemplified by prostaglandin I2, the most central therapeutic target in pulmonary arterial hypertension. New bioactive lipids other than eicosanoids have also been identified that are associated with the pathogenesis of PH. However, it remains largely unknown how mast cell-derived lipid mediators are involved in pulmonary vascular remodeling. Recently, it has been demonstrated that mast cells produce epoxidized n-3 fatty acid (n-3 epoxides) in a degranulation-independent manner, and that n-3 epoxides produced by mast cells regulate the abnormal activation of pulmonary fibroblasts and suppress the progression of pulmonary vascular remodeling. This review summarizes the role of mast cells and bioactive lipids in the pathogenesis of PH. In addition, we introduce the pathophysiological role and therapeutic potential of n-3 epoxides, a mast cell-derived novel lipid mediator, in the pulmonary vascular remodeling in PH. Further knowledge of mast cells and lipid mediators is expected to lead to the development of innovative therapies targeting pulmonary vascular remodeling.

Spontaneous Non-Traumatic Mediastinal Hematoma in a Patient on Imatinib Therapy for a Gastrointestinal Stromal Tumor (GIST)

Mediastinal hematomas are thoracic complications often resulting from direct trauma or aortic dissections. Spontaneous non-traumatic mediastinal hematomas are rare. We present a case of spontaneous non-traumatic mediastinal hematoma in a patient on Imatinib therapy for a gastrointestinal stromal tumor (GIST). A 67-year-old female presented to the ER with the chief complaint of constant sharp right shoulder pain that progressed to her chest. The patient was not on any anticoagulants and had not complained of shortness of breath. Under suspicion of a pulmonary embolism, a CT chest scan was performed, and a diagnosis of non-traumatic anterior mediastinal hematoma was confirmed. This case may warrant further investigation into the links between Imatinib use and the formation of mediastinal hematomas.

Clinical and Hemodynamic Responses to Imatinib in Pulmonary Veno-Occlusive Disease/Pulmonary Capillary Hemangiomatosis: A Retrospective Pilot Study of Five Cases and Review of the Literature

BACKGROUND

Pulmonary veno-occlusive disease (PVOD) and pulmonary capillary hemangiomatosis (PCH) are rare types of pulmonary arterial hypertension with dismal prognoses; there is no established medical treatment for these conditions. Possible efficacy of imatinib against these conditions has been reported in 15 cases; however, how and in whom imatinib is effective remain unknown.

METHODS

We retrospectively evaluated clinical data from consecutive patients with PVOD/PCH treated with imatinib at our institution. The diagnosis of PVOD/PCH was established using the following criteria: pre-capillary pulmonary hypertension; diffusion capacity of the lung for carbon monoxide < 60%; and two or more high-resolution computed tomography findings of interlobular septal thickening, centrilobular opacities, and mediastinal lymphadenopathy. The dose of pulmonary vasodilators remained unchanged during the assessment of imatinib.

RESULTS

The medical records of five patients with PVOD/PCH were reviewed. The patients were aged 67 ± 13 years, their diffusion capacity of the lung for carbon monoxide was 29 ± 8%, and their mean pulmonary artery pressure was 40 ± 7 mmHg. Imatinib was administered at 50-100 mg/day; consequently, the World Health Organization functional class improved in one patient. In addition, imatinib improved the arterial oxygen partial pressure in this and another patient (these two also experienced a decreased mean pulmonary artery pressure and pulmonary vascular resistance after imatinib usage).

CONCLUSIONS

This study indicated that imatinib improves the clinical condition, including pulmonary hemodynamics, of some patients with PVOD/PCH. In addition, patients with a certain high-resolution computed tomography pattern or PCH-dominant vasculopathy may respond favorably to imatinib.

Pericytes: The lung-forgotten cell type

Pericytes are a heterogeneous population of mesenchymal cells located on the abluminal surface of microvessels, where they provide structural and biochemical support. Pericytes have been implicated in numerous lung diseases including pulmonary arterial hypertension (PAH) and allergic asthma due to their ability to differentiate into scar-forming myofibroblasts, leading to collagen deposition and matrix remodelling and thus driving tissue fibrosis. Pericyte-extracellular matrix interactions as well as other biochemical cues play crucial roles in these processes. In this review, we give an overview of lung pericytes, the key pro-fibrotic mediators they interact with, and detail recent advances in preclinical studies on how pericytes are disrupted and contribute to lung diseases including PAH, allergic asthma, and chronic obstructive pulmonary disease (COPD). Several recent studies using mouse models of PAH have demonstrated that pericytes contribute to these pathological events; efforts are currently underway to mitigate pericyte dysfunction in PAH by targeting the TGF-β, CXCR7, and CXCR4 signalling pathways. In allergic asthma, the dissociation of pericytes from the endothelium of blood vessels and their migration towards inflamed areas of the airway contribute to the characteristic airway remodelling observed in allergic asthma. Although several factors have been suggested to influence this migration such as TGF-β, IL-4, IL-13, and periostin, recent evidence points to the CXCL12/CXCR4 pathway as a potential therapeutic target. Pericytes might also play an essential role in lung dysfunction in response to ageing, as they are responsive to environmental risk factors such as cigarette smoke and air pollutants, which are the main drivers of COPD. However, there is currently no direct evidence delineating the contribution of pericytes to COPD pathology. Although there is a lack of human clinical data, the recent available evidence derived from in vitro and animal-based models shows that pericytes play important roles in the initiation and maintenance of chronic lung diseases and are amenable to pharmacological interventions. Therefore, further studies in this field are required to elucidate if targeting pericytes can treat lung diseases.

AV-101, a novel inhaled dry-powder formulation of imatinib, in healthy adult participants: a phase 1 single and multiple ascending dose study

Background

Oral imatinib has been shown to be effective, but poorly tolerated, in patients with advanced pulmonary arterial hypertension (PAH). To maintain efficacy while improving tolerability, AV-101, a dry powder inhaled formulation of imatinib, was developed to deliver imatinib directly to the lungs.

Methods

This phase 1, placebo-controlled, randomised single ascending dose (SAD) and multiple ascending dose (MAD) study evaluated the safety/tolerability and pharmacokinetics of AV-101 in healthy adults. The SAD study included five AV-101 cohorts (1 mg, 3 mg, 10 mg, 30 mg, 90 mg) and placebo, and a single-dose oral imatinib 400-mg cohort. The MAD study included three AV-101 cohorts (10 mg, 30 mg, 90 mg) and placebo; dosing occurred twice daily for 7 days.

Results

82 participants (SAD n=48, MAD n=34) were enrolled. For the SAD study, peak plasma concentrations of imatinib occurred within 3 h of dosing with lower systemic exposure compared to oral imatinib (p<0.001). For the MAD study, systemic exposure of imatinib was higher after multiple doses of AV-101 compared to a single dose, but steady-state plasma concentrations were lower for the highest AV-101 cohort (90 mg) compared to simulated steady-state oral imatinib at day 7 (p=0.0002). Across AV-101 MAD dose cohorts, the most common treatment-emergent adverse events were cough (n=7, 27%) and headache (n=4, 15%).

Conclusions

AV-101 was well tolerated in healthy adults, and targeted doses of AV-101 significantly reduced the systemic exposure of imatinib compared with oral imatinib. An ongoing phase 2b/phase 3 study (IMPAHCT; clinicaltrials.gov identifier NCT05036135) will evaluate the safety/tolerability and clinical benefit of AV-101 for PAH.

New trends in pulmonary hypertension

Pulmonary hypertension (PH) is a prevalent disease of the pulmonary vasculature that is characterised by considerable morbidity and mortality. Substantial efforts have been made in recent years to improve disease recognition, diagnosis and management, and this is reflected in current guidelines. The haemodynamic definition of PH has been revised and a definition for exercise PH has been provided. Risk stratification has been refined and the importance of comorbidities and phenotyping have been highlighted. These changes provide an opportunity to potentially identify pulmonary vascular disease at an earlier stage and to enhance patient-centred, goal-orientated treatment decisions. A promising fourth treatment pathway for pulmonary arterial hypertension and potential targeted therapies for group 3 PH are on the horizon, concepts which seemed inconceivable only a few years ago. Beyond medication, there is a greater appreciation for the importance of supervised training in stable PH and the possible role of interventional therapies in select cases. The landscape of PH is changing and it is characterised by progress, innovation and opportunities. In this article, we highlight some of the new trends in PH, with a specific focus on the revised European Society of Cardiology/European Respiratory Society 2022 guidelines for the diagnosis and management of PH.

Novel Molecular Mechanisms Involved in the Medical Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe condition with a high mortality rate despite advances in diagnostic and therapeutic strategies. In recent years, significant scientific progress has been made in the understanding of the underlying pathobiological mechanisms. Since current available treatments mainly target pulmonary vasodilation, but lack an effect on the pathological changes that develop in the pulmonary vasculature, there is need to develop novel therapeutic compounds aimed at antagonizing the pulmonary vascular remodeling. This review presents the main molecular mechanisms involved in the pathobiology of PAH, discusses the new molecular compounds currently being developed for the medical treatment of PAH and assesses their potential future role in the therapeutic algorithms of PAH.

Pathophysiology and new advances in pulmonary hypertension

Pulmonary hypertension is a progressive and often fatal cardiopulmonary condition characterised by increased pulmonary arterial pressure, structural changes in the pulmonary circulation, and the formation of vaso-occlusive lesions. These changes lead to increased right ventricular afterload, which often progresses to maladaptive right ventricular remodelling and eventually death. Pulmonary arterial hypertension represents one of the most severe and best studied types of pulmonary hypertension and is consistently targeted by drug treatments. The underlying molecular pathogenesis of pulmonary hypertension is a complex and multifactorial process, but can be characterised by several hallmarks: inflammation, impaired angiogenesis, metabolic alterations, genetic or epigenetic abnormalities, influence of sex and sex hormones, and abnormalities in the right ventricle. Current treatments for pulmonary arterial hypertension and some other types of pulmonary hypertension target pathways involved in the control of pulmonary vascular tone and proliferation; however, these treatments have limited efficacy on patient outcomes. This review describes key features of pulmonary hypertension, discusses current and emerging therapeutic interventions, and points to future directions for research and patient care. Because most progress in the specialty has been made in pulmonary arterial hypertension, this review focuses on this type of pulmonary hypertension. The review highlights key pathophysiological concepts and emerging therapeutic directions, targeting inflammation, cellular metabolism, genetics and epigenetics, sex hormone signalling, bone morphogenetic protein signalling, and inhibition of tyrosine kinase receptors.

The Evolving Management and Treatment Options for Patients with Pulmonary Hypertension: Current Evidence and Challenges

Pulmonary hypertension may develop as a disease process specific to pulmonary arteries with no identifiable cause or may occur in relation to other cardiopulmonary and systemic illnesses. The World Health Organization (WHO) classifies pulmonary hypertensive diseases on the basis of primary mechanisms causing increased pulmonary vascular resistance. Effective management of pulmonary hypertension begins with accurately diagnosing and classifying the disease in order to determine appropriate treatment. Pulmonary arterial hypertension (PAH) is a particularly challenging form of pulmonary hypertension as it involves a progressive, hyperproliferative arterial process that leads to right heart failure and death if untreated. Over the last two decades, our understanding of the pathobiology and genetics behind PAH has evolved and led to the development of several targeted disease modifiers that ameliorate hemodynamics and quality of life. Effective risk management strategies and more aggressive treatment protocols have also allowed better outcomes for patients with PAH. For those patients who experience progressive PAH with medical therapy, lung transplantation remains a life-saving option. More recent work has been directed at developing effective treatment strategies for other forms of pulmonary hypertension, such as chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary hypertension due to other lung or heart diseases. The discovery of new disease pathways and modifiers affecting the pulmonary circulation is an ongoing area of intense investigation.

Inhaled seralutinib exhibits potent efficacy in models of pulmonary arterial hypertension

BACKGROUND

Signalling through platelet-derived growth factor receptor (PDGFR), colony-stimulating factor 1 receptor (CSF1R) and mast/stem cell growth factor receptor kit (c-KIT) plays a critical role in pulmonary arterial hypertension (PAH). We examined the preclinical efficacy of inhaled seralutinib, a unique small-molecule PDGFR/CSF1R/c-KIT kinase inhibitor in clinical development for PAH, in comparison to a proof-of-concept kinase inhibitor, imatinib.

METHODS

Seralutinib and imatinib potency and selectivity were compared. Inhaled seralutinib pharmacokinetics/pharmacodynamics were studied in healthy rats. Efficacy was evaluated in two rat models of PAH: SU5416/Hypoxia (SU5416/H) and monocrotaline pneumonectomy (MCTPN). Effects on inflammatory/cytokine signalling were examined. PDGFR, CSF1R and c-KIT immunohistochemistry in rat and human PAH lung samples and microRNA (miRNA) analysis in the SU5416/H model were performed.

RESULTS

Seralutinib potently inhibited PDGFRα/β, CSF1R and c-KIT. Inhaled seralutinib demonstrated dose-dependent inhibition of lung PDGFR and c-KIT signalling and increased bone morphogenetic protein receptor type 2 (BMPR2). Seralutinib improved cardiopulmonary haemodynamic parameters and reduced small pulmonary artery muscularisation and right ventricle hypertrophy in both models. In the SU5416/H model, seralutinib improved cardiopulmonary haemodynamic parameters, restored lung BMPR2 protein levels and decreased N-terminal pro-brain natriuretic peptide (NT-proBNP), more than imatinib. Quantitative immunohistochemistry in human lung PAH samples demonstrated increased PDGFR, CSF1R and c-KIT. miRNA analysis revealed candidates that could mediate seralutinib effects on BMPR2.

CONCLUSIONS

Inhaled seralutinib was an effective treatment of severe PAH in two animal models, with improved cardiopulmonary haemodynamic parameters, a reduction in NT-proBNP, reverse remodelling of pulmonary vascular pathology and improvement in inflammatory biomarkers. Seralutinib showed greater efficacy compared to imatinib in a preclinical study.

The evolving landscape of pulmonary arterial hypertension clinical trials

Although it is a rare disease, the number of available therapeutic options for treating pulmonary arterial hypertension has increased since the late 1990s, with multiple drugs developed that are shown to be effective in phase 3 randomised controlled trials. Despite considerable advancements in pulmonary arterial hypertension treatment, prognosis remains poor. Existing therapies target pulmonary endothelial dysfunction with vasodilation and anti-proliferative effects. Novel therapies that target proliferative vascular remodelling and affect important outcomes are urgently needed. There is need for additional innovations in clinical trial design so that all emerging candidate therapies can be rigorously studied. Pulmonary arterial hypertension trial design has shifted from short-term submaximal exercise capacity as a primary endpoint, to larger clinical event-driven trial outcomes. Event-driven pulmonary arterial hypertension trials could face feasibility and efficiency issues in the future because increasing sample sizes and longer follow-up durations are needed, which would be problematic in such a rare disease. Enrichment strategies, innovative and alternative trial designs, and novel trial endpoints are potential solutions that could improve the efficiency of future pulmonary arterial hypertension trials while maintaining robustness and clinically meaningful evidence.

An organ-on-chip model of pulmonary arterial hypertension identifies a BMPR2-SOX17-prostacyclin signalling axis

Pulmonary arterial hypertension (PAH) is an unmet clinical need. The lack of models of human disease is a key obstacle to drug development. We present a biomimetic model of pulmonary arterial endothelial-smooth muscle cell interactions in PAH, combining natural and induced bone morphogenetic protein receptor 2 (BMPR2) dysfunction with hypoxia to induce smooth muscle activation and proliferation, which is responsive to drug treatment. BMPR2- and oxygenation-specific changes in endothelial and smooth muscle gene expression, consistent with observations made in genomic and biochemical studies of PAH, enable insights into underlying disease pathways and mechanisms of drug response. The model captures key changes in the pulmonary endothelial phenotype that are essential for the induction of SMC remodelling, including a BMPR2-SOX17-prostacyclin signalling axis and offers an easily accessible approach for researchers to study pulmonary vascular remodelling and advance drug development in PAH.

Recent Advances in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a disease in which stenosis or obstruction of the pulmonary arteries (PAs) causes an increase in PA pressure, leading to right-sided heart failure and death. Basic research has revealed a decrease in the levels of endogenous vasodilators, such as prostacyclin, and an increase in the levels of endogenous vasoconstrictors, such as endothelin, in patients with PAH, leading to the development of therapeutic agents. Currently, therapeutic agents for PAH target three pathways that are selective for PAs: the prostacyclin, endothelin, and nitric oxide pathways. These treatments improve the prognosis of PAH patients. In this review, we introduce new drug therapies and provide an overview of the current therapeutic agents.

Strategizing Drug Therapies in Pulmonary Hypertension for Improved Outcomes

Pulmonary hypertension (PH) is characterized by a resting mean pulmonary artery pressure (PAP) of 20 mmHg or more and is a disease of multiple etiologies. Of the various types of PH, pulmonary arterial hypertension (PAH) is characterized by elevated resistance in the pulmonary arterial tree. It is a rare but deadly disease characterized by vascular remodeling of the distal pulmonary arteries. This paper focuses on PAH diagnosis and management including current and future treatment options. Over the last 15 years, our understanding of this progressive disease has expanded from the concept of vasoconstrictive/vasodilatory mismatch in the pulmonary arterioles to now a better appreciation of the role of genetic determinants, numerous cell signaling pathways, cell proliferation and apoptosis, fibrosis, thrombosis, and metabolic abnormalities. While knowledge of its pathophysiology has expanded, the majority of the treatments available today still modulate the same three vasodilatory pathways that have been targeted for over 30 years (endothelin, nitric oxide, and prostacyclin). While modifying these pathways may help improve symptoms and quality of life, none of these directly modify the underlying disease pathogenesis. However, there are now studies ongoing with new drugs that can prevent or reverse these underlying causes of PAH. This review discusses the evidence base for the current treatment algorithms for PAH, as well as discusses novel therapies in development.

Regnase-1 Prevents Pulmonary Arterial Hypertension Through mRNA Degradation of Interleukin-6 and Platelet-Derived Growth Factor in Alveolar Macrophages

BACKGROUND

Pulmonary arterial hypertension (PAH) is a type of pulmonary hypertension (PH) characterized by obliterative pulmonary vascular remodeling, resulting in right-sided heart failure. Although the pathogenesis of PAH is not fully understood, inflammatory responses and cytokines have been shown to be associated with PAH, in particular, with connective tissue disease-PAH. In this sense, Regnase-1, an RNase that regulates mRNAs encoding genes related to immune reactions, was investigated in relation to the pathogenesis of PH.

METHODS

We first examined the expression levels of ZC3H12A (encoding Regnase-1) in peripheral blood mononuclear cells from patients with PH classified under various types of PH, searching for an association between the ZC3H12A expression and clinical features. We then generated mice lacking Regnase-1 in myeloid cells, including alveolar macrophages, and examined right ventricular systolic pressures and histological changes in the lung. We further performed a comprehensive analysis of the transcriptome of alveolar macrophages and pulmonary arteries to identify genes regulated by Regnase-1 in alveolar macrophages.

RESULTS

ZC3H12A expression in peripheral blood mononuclear cells was inversely correlated with the prognosis and severity of disease in patients with PH, in particular, in connective tissue disease-PAH. The critical role of Regnase-1 in controlling PAH was also reinforced by the analysis of mice lacking Regnase-1 in alveolar macrophages. These mice spontaneously developed severe PAH, characterized by the elevated right ventricular systolic pressures and irreversible pulmonary vascular remodeling, which recapitulated the pathology of patients with PAH. Transcriptomic analysis of alveolar macrophages and pulmonary arteries of these PAH mice revealed that Il6, Il1b, and Pdgfa/b are potential targets of Regnase-1 in alveolar macrophages in the regulation of PAH. The inhibition of IL-6 (interleukin-6) by an anti-IL-6 receptor antibody or platelet-derived growth factor by imatinib but not IL-1β (interleukin-1β) by anakinra, ameliorated the pathogenesis of PAH.

CONCLUSIONS

Regnase-1 maintains lung innate immune homeostasis through the control of IL-6 and platelet-derived growth factor in alveolar macrophages, thereby suppressing the development of PAH in mice. Furthermore, the decreased expression of Regnase-1 in various types of PH implies its involvement in PH pathogenesis and may serve as a disease biomarker, and a therapeutic target for PH as well.

Evolving nonvasodilator treatment options for pulmonary arterial hypertension

PURPOSE OF REVIEW

With the establishment of vasodilator therapy as a mainstay of treatment for pulmonary arterial hypertension (PAH), new therapeutic approaches are needed to prevent the development of the vasculopathy associated with this disease. Many studies are currently underway to investigate nonvasodilator treatment options.

RECENT FINDINGS

Modulation of bone morphogenic protein receptor type 2 (BMPR2) signaling with sotatercept showed promising results in phase 2 studies. Rituximab, an anti-CD20 monoclonal antibody, showed some signal for beneficial effect in patients with scleroderma-associated PAH. Studies evaluating agents including tocilizumab, selonsertib, bardoxolone, 10-nitro-9(E)-enoic acid (CXA-10) and intravenous iron have not shown acceptable efficacy in treating PAH.

SUMMARY

Pharmacologic approaches for the treatment of PAH include altering of transforming growth factor β/BMPR2 signaling, proliferation via growth factors, immune response, oxidative stress, estrogen signaling, metabolism, and neurohormonal modulation. Other treatment modalities including pulmonary artery nerve denervation, stem cell therapy, and inter-atrial shunt formation are also being explored.

Assessment of Clinical Worsening End Points as a Surrogate for Mortality in Pulmonary Arterial Hypertension: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Clinical worsening (CW) is a composite end point commonly used in pulmonary arterial hypertension (PAH) trials. We aimed to assess the trial-level surrogacy of CW for mortality in PAH trials, and whether the various CW components were similar in terms of frequency of occurrence, treatment-related relative risk (RR) reduction, and importance to patients.

METHODS

We searched MEDLINE, Embase, and the Cochrane Library (January 1990 to December 2020) for trials evaluating the effects of PAH therapies on CW. The coefficient of determination between the RR for CW and mortality was assessed by regression analysis. The frequency of occurrence, RR reduction, and importance to patients of the CW components were assessed.

RESULTS

We included 35 independent cohorts (9450 patients). PAH therapies significantly reduced CW events (RR, 0.64 [95% CI, 0.55-0.73]), including PAH-related hospitalizations (RR, 0.61 [95% CI, 0.47-0.79]), treatment escalation (RR, 0.57 [95% CI, 0.38-0.84]) and symptomatic progression (RR, 0.58 [95% CI, 0.48-0.69]), and modestly reduced all-cause mortality when incorporating deaths occurring after a primary CW-defining event (RR, 0.860 [95% CI, 0.742-0.997]). However, the effects of PAH-specific therapies on CW only modestly correlated with their effects on mortality (R²_trial, 0.35 [95% CI, 0.10-0.59]; P<0.0001), and the gradient in the treatment effect across component end points was large in the majority of trials. The weighted proportions of CW-defining events were hospitalization (33.5%) and symptomatic progression (32.3%), whereas death (6.7%), treatment escalation (5.6%), and transplantation/atrioseptostomy (0.2%) were infrequent. CW events were driven by the occurrence of events of major (49%) and mild-to-moderate (37%) importance to patients, with 14% of the events valued as critical.

CONCLUSIONS

PAH therapies significantly reduced CW events, but study-level CW is not a surrogate for mortality in PAH trials. Moreover, components of CW largely vary in frequency, response to therapy, and importance to patients and are thus not interchangeable.

REGISTRATION

URL: https://www.crd.york.ac.uk/PROSPERO; Unique identifier: CRD42020178949.

The Paradox of Pulmonary Vascular Resistance: Restoration of Pulmonary Capillary Recruitment as a Sine Qua Non for True Therapeutic Success in Pulmonary Arterial Hypertension

Exercise-induced increases in pulmonary blood flow normally increase pulmonary arterial pressure only minimally, largely due to a reserve of pulmonary capillaries that are available for recruitment to carry the flow. In pulmonary arterial hypertension, due to precapillary arteriolar obstruction, such recruitment is greatly reduced. In exercising pulmonary arterial hypertension patients, pulmonary arterial pressure remains high and may even increase further. Current pulmonary arterial hypertension therapies, acting principally as vasodilators, decrease calculated pulmonary vascular resistance by increasing pulmonary blood flow but have a minimal effect in lowering pulmonary arterial pressure and do not restore significant capillary recruitment. Novel pulmonary arterial hypertension therapies that have mainly antiproliferative properties are being developed to try and diminish proliferative cellular obstruction in precapillary arterioles. If effective, those agents should restore capillary recruitment and, during exercise testing, pulmonary arterial pressure should remain low despite increasing pulmonary blood flow. The effectiveness of every novel therapy for pulmonary arterial hypertension should be evaluated not only at rest, but with measurement of exercise pulmonary hemodynamics during clinical trials.

Ataxia telangiectasia mutated: The potential negative regulator in platelet-derived growth factor-BB promoted proliferation of pulmonary arterial smooth muscle cells

Objective

To study the role of ataxia telangiectasia mutated (ATM) in the platelet-derived growth factor (PDGF)-BB-induced proliferation of pulmonary arterial smooth muscle cells (PASMCs) through reactive oxygen species (ROS) formation.

Methods

Primary cultures of PASMCs were treated with different concentrations of PDGF-BB or exogenous hydrogen peroxide (H₂O₂). The activation level of ATM and the proliferation level of PASMCs were measured by immunofluorescence staining and Cell Counting Kit-8, respectively. Moreover, NADPH oxidase 2 (NOX2) and intracellular H₂O₂ were detected under the stimulation of different levels of PDGF-BB by Western blot and dihydroethidium staining.

Results

Both the control group and 50 ng/ml of the PDGF-BB group showed significantly higher levels of phosphorylation ATM compared to other groups (P < 0.05). With the ATM inhibitor, 50 ng/ml of the PDGF-BB group showed further increased proliferative level compared to the 10 ng/ml (P < 0.05). Both the levels of NOX2 and H₂O₂ showed dose-dependent manners under PDGF-BB stimulation (P < 0.05). ATM could be activated by H₂O₂ upon a dose-dependent way, except for the 500 μM H₂O₂ group. Under 200 μM H₂O₂ stimulation, proliferation level decreased significantly (P < 0.05), while no significant difference was shown with the addition of ATM inhibitor (P > 0.05).

Conclusion

Our study first established ROS-induced ATM activation in PDGF-BB-stimulated proliferation of PASMCs. Inhibition of ATM had promoted effects on the proliferation of PASMCs under the excessive levels of PDGF-BB and H₂O₂. Our study might provide a novel promising target for the treatment of pulmonary arterial hypertension (PAH).

Effects of oral targeted treatments in pulmonary arterial hypertension: A systematic review and meta-analysis

Background

Although pulmonary arterial hypertension (PAH) is a fatal disease, specific drugs have been used to treat PAH. These drugs predominantly target these three pathobiological pathways: Endothelin receptor antagonist (ERA), nitric oxide (NO), and prostanoids pathways. In this review, we aimed to analyze the efficacy and safety of oral targeted treatments for PAH.

Methods

The national library of medicine (MEDLINE), excerpta medica database (EMBASE), and Cochrane Central Register of Controlled Trials databases were searched. Randomized controlled trials that compared the oral targeted drugs with placebos were selected. We calculated odds ratios (ORs) with 95% confidence intervals (CIs) for variables with dichotomous outcomes, and standardized mean differences with continuous outcomes variables. Additionally, the mean of the differences for the 6-min walk distance (6MWD) was analyzed.

Results

In total, 23 studies involving 7,121 patients were included in this study. These studies show that orally PAH-specific drugs could decrease the risk of clinical worsening events, with an OR of 0.55 (p < 0.001). Furthermore, these drugs could improve exercise capacity, showing a 21.74-m increase in 6MWD (95% CI: 17.53–25.95 m) and cause a greater amelioration of functional class (OR = 0.60, 95% CI: 0.47–0.76). Additionally, subgroup analysis indicated that compared with placebo, ERAs, and drugs in the NO pathway were most effective and safe, which are associated with an improvement in exercise capacity, 6MWD, and worsening events-free survival rate.

Conclusion

Nitric oxide exhibited the most prominent clinical effect on exercise tolerance. However, in the subgroup analysis, oral targeted drugs of different pathways show applicability to different populations, which highlights the need for precise treatment in the clinical setting.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=297946], identifier [CRD 42022297946].