ENAn international research initiative led by medical scientists in Germany has announced promising Phase 2 clinical results for the investigational inhaled drug mosliciguat. The study evaluated patients with pulmonary hypertension associated with interstitial lung disease (PH-ILD), a severe condition with limited therapeutic options. In the global PHocus trial involving 135 adult patients across 87 centers in 20 countries, dry-powder inhaled mosliciguat achieved a 56.3 percent placebo-adjusted reduction in pulmonary vascular resistance at Week 16, alongside meaningful gains in exercise capacity. These findings have laid the groundwork for the ongoing Phase 3 PHrontier trial, which is currently enrolling approximately 375 patients worldwide.
Understanding Pulmonary Hypertension in Interstitial Lung Disease
Interstitial lung diseases encompass a diverse group of chronic conditions characterized by progressive inflammation and irreversible scarring of lung parenchyma. As the structural architecture of the lung deteriorates, secondary pulmonary vascular remodeling frequently develops. This pathological transformation narrows the pulmonary arterial network, forcing the right ventricle of the heart to generate significantly higher pressures to maintain blood flow through the lungs.
The combination of structural lung disease and vascular strain leads to severe breathlessness, profound physical fatigue, and reduced functional tolerance. The emergence of pulmonary hypertension in patients with underlying lung fibrosis substantially worsens overall clinical outcomes and long-term prognosis. Consequently, managing this dual burden represents one of the most complex challenges in contemporary respiratory medicine.
Chronic inflammation and oxidative stress in the diseased lung tissue disrupt critical biochemical pathways that regulate vascular tone. Traditional therapies often fail to deliver targeted relief to the pulmonary vessels without causing systemic adverse effects, reinforcing the need for site-specific treatment strategies.
Current Diagnostic Standards and Therapeutic Principles in Germany
In German university hospitals and specialized lung centers, evaluating suspected pulmonary vascular disease involves comprehensive clinical and hemodynamic profiling. Echocardiography serves as an essential initial screening tool to evaluate right heart geometry and estimate pulmonary pressures. To establish a definitive diagnosis, specialists perform right heart catheterization, directly measuring pulmonary vascular resistance and cardiovascular hemodynamic parameters.
Translational research into the nitric oxide–soluble guanylate cyclase–cyclic guanosine monophosphate (NO–sGC–cGMP) pathway has a long history in Giessen. Previous collaborations between researchers in Giessen and pharmaceutical scientists led by Johannes-Peter Stasch at Bayer yielded riociguat, the first sGC stimulator approved for pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. This scientific breakthrough was recognized with the 2015 German Future Prize of the Federal President.
However, sGC stimulators predominantly act on heme-containing, native forms of the enzyme. In conditions driven by chronic oxidative stress, sGC molecules lose their heme group and become insensitive to endogenous nitric oxide. Furthermore, oral pulmonary vasodilators can induce systemic arterial hypotension, limiting their tolerated dosage in vulnerable patient populations.
Innovative Mechanism and Key Clinical Findings for Mosliciguat
Mosliciguat represents a distinct scientific evolution as a targeted sGC activator. Unlike earlier stimulators, sGC activators specifically target the dysfunctional, heme-free, and oxidized state of the enzyme that accumulates in diseased pulmonary vasculature. Administered as a dry-powder inhalation, mosliciguat restores local cGMP signaling directly in the lungs while minimizing unintended systemic vasodilation and drop in blood pressure.
Initial proof of clinical concept was established in the Phase 1b ATMOS study, published in the medical journal Thorax. Patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension experienced sustained reductions in pulmonary vascular resistance following a single inhaled dose of mosliciguat, with a favorable safety profile and no clinically relevant changes in systemic blood pressure.
Building on these results, the international Phase 2 PHocus trial was conducted under the leadership of pulmonary vascular investigators including Werner Seeger, Ardeschir Ghofrani, Friedrich Grimminger, and Khodr Tello from the Institute for Lung Health (ILH), the German Center for Lung Research (DZL), and the Universities of Giessen and Marburg Lung Center (UGMLC), in partnership with Pulmovant. At Week 16, mosliciguat demonstrated a 56.3 percent placebo-adjusted reduction in pulmonary vascular resistance. Patients gained 35.2 meters in the six-minute walking distance at Week 16, which increased to 52.7 meters at Week 24 in exploratory analysis, accompanied by improvements in NT-proBNP levels.
Clinical Implications and Options for International Patients
The Phase 2 results demonstrated consistent hemodynamic and functional improvements across all prespecified subgroups, regardless of underlying disease subtype or background medication. While mosliciguat remains an investigational drug and is not yet approved for general prescription, these results mark significant progress in addressing an area of high unmet medical need.
The global Phase 3 PHrontier trial is now actively underway under the sponsorship of Pulmovant, planning to evaluate approximately 375 patients with PH-ILD. The trial’s primary endpoint focuses on changes in the six-minute walking distance after 24 weeks of treatment, alongside secondary endpoints evaluating time to clinical worsening, pulmonary vascular resistance, and cardiac biomarker responses.
For international patients seeking advanced care in Germany, these scientific advancements reflect the high standard of specialized pulmonary centers. Patients undergoing evaluation at institutions affiliated with the DZL network can access comprehensive diagnostic workups, expert multidisciplinary consultations, and discussions regarding potential participation in active clinical trials.