A Randomized, Placebo-controlled Trial of Roflumilast. Effect on Proline-Glycine-Proline and Neutrophilic Inflammation in Chronic Obstructive Pulmonary Disease

Abstract

Rationale: Roflumilast is a therapeutic agent in the treatment of chronic obstructive pulmonary disease (COPD). It has antiinflammatory effects; however, it is not known whether it can affect a biologic pathway implicated in COPD pathogenesis and progression. The self-propagating acetyl-proline-glycine-proline (AcPGP) pathway is a novel means of neutrophilic inflammation that is pathologic in the development of COPD. AcPGP is produced by extracellular matrix collagen breakdown with prolyl endopeptidase and leukotriene A4 hydrolase serving as the enzymes responsible for its production and degradation, respectively.

Objectives: We hypothesized that roflumilast would decrease AcPGP, halting the feed-forward cycle of inflammation.

Methods: We conducted a single-center, placebo-controlled, randomized study investigating 12 weeks of roflumilast treatment added to current therapy in moderate-to-severe COPD with chronic bronchitis. Subjects underwent sputum and blood analyses, pulmonary function testing, exercise tolerance, and quality-of-life assessment at 0, 4, and 12 weeks.

Measurements and main results: Twenty-seven patients were enrolled in the intention-to-treat analysis. Roflumilast treatment decreased sputum AcPGP by more than 50% (P < 0.01) and prolyl endopeptidase by 46% (P = 0.02), without significant improvement in leukotriene A4 hydrolase activity compared with placebo. Roflumilast also reduces other inflammatory markers. There were no significant changes in lung function, quality of life, or exercise tolerance between roflumilast- and placebo-treated groups.

Conclusions: Roflumilast reduces pulmonary inflammation through decreasing prolyl endopeptidase activity and AcPGP. As expected for lower AcPGP levels, markers of neutrophilic inflammation are blunted. Inhibiting this self-propagating pathway lessens the overall inflammatory burden, which may alter the natural history of COPD, including the risk of exacerbation. Clinical trial registered with www.clinicaltrials.gov (NCT 01572948).

Trial registration: ClinicalTrials.gov NCT01572948.

Keywords: COPD; neutrophil; proline-glycine-proline; prolyl endopeptidase; roflumilast.

Figure 1.

Consolidated Standards of Reporting Trials flow diagram.

Figure 2.

Roflumilast reduces sputum acetyl-proline-glycine-proline (AcPGP). Sputa were analyzed in randomized patients. (A) Roflumilast treatment results in lower AcPGP levels compared with placebo after 12 weeks of therapy. (B) Roflumilast reduces sputum AcPGP by >50%. Following 12 weeks of treatment with (C) roflumilast or placebo, there were no statistical changes in sputum proline-glycine-proline (PGP). Open bars and circle represent the placebo group (n = 16), and solid bars and square represent the roflumilast group (n = 11). Values expressed as mean ± SEM. *P < 0.05. NS = not significant.

Figure 3.

Roflumilast affects enzymes critical to the acetyl-proline-glycine-proline/proline-glycine-proline pathway. (A) Roflumilast decreases prolyl endopeptidase (PE), the enzyme critical in the generation of proline-glycine-proline. (B) Likewise, roflumilast treatment reduces leukotriene A₄ hydrolase (LTA₄H) amount in sputum compared with placebo. (C) Although there was an increase in LTA₄H aminopeptidase activity in roflumilast treatment after 12 weeks, there were no statistical differences in this group or placebo compared with baseline values. Open bars represent the placebo group (n = 16), and solid bars represent the roflumilast group (n = 11). Values expressed as mean ± SEM. *P < 0.05.

Figure 4.

Roflumilast therapy does not affect systemic proline-glycine-proline (PGP). There were no statistical differences in plasma (A) acetyl-proline-glycine-proline (AcPGP) and (B) PGP, suggesting the antiinflammatory effect is most pronounced in the lung. Open bars represent the placebo group (n = 16), and solid bars represent the roflumilast group (n = 11). Values expressed as mean ± SEM. NS = not significant.

Figure 5.

Roflumilast reduces other markers of pulmonary inflammation. (A) Myeloperoxidase (MPO) was significantly reduced at 4 and 12 weeks. Roflumilast use is associated with a reduction in (B) leukotriene B₄ (LTB₄) and (C) neutrophil elastase but not (D) IL-8. (E) Neutrophil counts were reduced, although no statistical difference was observed. Open bars represent the placebo group (n = 16), and solid bars represent the roflumilast group (n = 11). Values expressed as mean ± SEM. *P < 0.05; **P < 0.01. NS = not significant.