Used primarily in the treatment of chronic obstructive pulmonary disease (COPD), this compound acts as a selective phosphodiesterase-4 (PDE4) inhibitor, helping to reduce inflammation in the airways. It has been investigated for its potential to improve lung function and decrease the frequency of exacerbations in patients with COPD. Additionally, due to its anti-inflammatory properties, it has been studied in other respiratory and inflammatory conditions such as asthma and rheumatoid arthritis. Despite showing promise in clinical trials, its development was limited by side effects and variable efficacy, leading to discontinuation in late-stage development.