Roflumilast is in late-stage clinical development for the treatment of chronic obstructive pulmonary disease (COPD). We investigated the effects of roflumilast N-oxide (RNO), at concentrations corresponding to therapeutic plasma levels, on human cells involved in pathophysiology of COPD.
RNO was tested in the following in vitro systems according to standard protocols: fMLP-induced O2–, CD11b, endothelial adhesion and transendothelial migration of neutrophils; LPS-induced TNFα release from macrophages, antiCD3/antiCD28-induced proliferation and granzyme B release of CD8 T-cells; TGFβ1-induced O2–(A549) and TNFα-induced GMCSF (BEAS2B) release from airway epithelial cells; bFGF-induced proliferation and TGFβ1-induced expression of α-smooth muscle actin (αSMA), CTGF, fibronectin and collagen I of lung fibroblasts; serum-induced proliferation of airway smooth muscle cells (ASMC); thrombin-induced permeability of endothelial cells.
As previously reported, roflumilast 500 αg once daily results in RNO plasma concentrations around 2 nM in humans. Effects of 2 nM RNO on cell functions were determined and effective concentrations for half-maximum inhibition calculated (EC50). At 2 nM RNO, cell functions were inhibited at different extents contingent on the cellular system. In some of the in vitro systems, endogenously formed mediators in inflammation (adenosine, PGE2, NO) triggering cAMP or cGMP enabled inhibitory effects of RNO. For example, removing adenosine by adenosine deaminase reversed inhibition of neutrophil adhesion to endothelial cells; inhibiting PGE2 release by indomethacin abolished reduction of ASMC proliferation, and removing NO by L-NAME compromised inhibition of endothelial permeability.
RNO at concentrations corresponding to therapeutic plasma levels inhibits numerous cell functions important in COPD pathophysiology.
These pleiotropic cellular effects may account for the clinical efficacy of roflumilast in COPD patients.
Javier Milara, Grant monies (from sources other than industry) Eesteban Morcillo and Julio Cortijo have received grant monies from the Ministry of Science of Spain.; Grant monies (from industry related sources) Eesteban Morcillo and Julio Cortijo have received grant monies from Nycomed GmbH.; Shareholder Christian Schudt is a shareholder.; Employee Rolf Beume, Hermann Tenor and Armin Hatzelmann are full-time employees of Nycomed GmbH. Christian Schudt is a former employee of Altana Pharma (now Nycomed GmbH); Product/procedure/technique that is considered research and is NOT yet approved for any purpose. The contribution describes effects of roflumilast N-oxide, the active metabolite of roflumilast, the oral and once daily PDE4 inhibitor currently in development for COPD at NYCOMED GmbH.