A therapeutic principle rooted in decades of pulmonary vascular research is entering a new stage of clinical development. The investigational inhaled drug mosliciguat, a soluble guanylate cyclase (sGC) activator, has produced marked and consistent effects in a randomized phase 2 study involving patients with pulmonary hypertension associated with interstitial lung disease (PH-ILD), one of the most challenging forms of pulmonary vascular disease.