Theophylline-d₃ is deuterated labeled Theophylline (HY-B0809). Theophylline (1,3-Dimethylxanthine) is a potent phosphodiesterase (PDE) inhibitor, adenosine receptor antagonist, and histone deacetylase (HDAC) activator. Theophylline (1,3-Dimethylxanthine) inhibits PDE3 activity to relax airway smooth muscle. Theophylline (1,3-Dimethylxanthine) has anti-inflammatory activity by increase IL-10 and inhibit NF-κB into the nucleus. Theophylline (1,3-Dimethylxanthine) induces apoptosis. Theophylline (1,3-Dimethylxanthine) can be used for asthma and chronic obstructive pulmonary disease (COPD) research^{[1][2][3][4][5]}.