To obtain a better perspective on the future roles of PDE4 inhibitors in COPD and pulmonary fibrosis, we searched www.ClinicalTrials.gov for all actively recruiting clinical trials for roflumilast, nerandomilast, pirfenidone and nintedanib in pulmonary disorders as of 28 August 2025 (see Supplemental File). This evidence concerns the gene PDE4A and chronic obstructive pulmonary disease.