Roflumilast is an orally active, selective inhibitor of phophodiesterase-4 (PDE-4) with IC50 value of 0.11nM [1].

Roflumilast is developed for the treatment of the inflammatory component of COPD since PDE-4 is found mainly in inflammatory cells. In vitro studies show that roflumilast inhibits the production of inflammatory mediators in a variety of human immune cells, suggesting a role for reducing COPD-related inflammation. Roflumilast has a rapid absorption with a bioavailability of ~ 80% and the half-life is approximately 17h after repeated dosing of 500 mcg OD. Pharmacokinetic studies show no significant interactions with the drugs used by COPD patients. Roflumilast is also found to decrease glucose levels in patients with newly diagnosed type-2 diabetes since diabetes is an important comorbidity associated with COPD [2].

References:
[1] Z Huang, JA Mancini. Phosphodiesterase 4 Inhibitors for the Treatment of Asthma and COPD. Current Medicinal Chemistry, 2006.
[2] Tashkin DP. Roflumilast : the new orally active, selective phophodiesterase-4 inhibitor, for the treatment of COPD. Expert Opin Pharmacother. 2014 Jan;15(1):85-96.