PF-1355, a Mechanism-Based Myeloperoxidase Inhibitor, Prevents Immune Complex Vasculitis and Anti–Glomerular Basement Membrane Glomerulonephritis

Abstract

Small vessel vasculitis is a life-threatening condition and patients typically present with renal and pulmonary injury. Disease pathogenesis is associated with neutrophil accumulation, activation, and oxidative damage, the latter being driven in large part by myeloperoxidase (MPO), which generates hypochlorous acid among other oxidants. MPO has been associated with vasculitis, disseminated vascular inflammation typically involving pulmonary and renal microvasculature and often resulting in critical consequences. MPO contributes to vascular injury by 1) catabolizing nitric oxide, impairing vasomotor function; 2) causing oxidative damage to lipoproteins and endothelial cells, leading to atherosclerosis; and 3) stimulating formation of neutrophil extracellular traps, resulting in vessel occlusion and thrombosis. Here we report a selective 2-thiouracil mechanism-based MPO inhibitor (PF-1355 [2-(6-(2,5-dimethoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide) and demonstrate that MPO is a critical mediator of vasculitis in mouse disease models. A pharmacokinetic/pharmacodynamic response model of PF-1355 exposure in relation with MPO activity was derived from mouse peritonitis. The contribution of MPO activity to vasculitis was then examined in an immune complex model of pulmonary disease. Oral administration of PF-1355 reduced plasma MPO activity, vascular edema, neutrophil recruitment, and elevated circulating cytokines. In a model of anti-glomerular basement membrane disease, formerly known as Goodpasture disease, albuminuria and chronic renal dysfunction were completely suppressed by PF-1355 treatment. This study shows that MPO activity is critical in driving immune complex vasculitis and provides confidence in testing the hypothesis that MPO inhibition will provide benefit in treating human vasculitic diseases.

Myeloperoxidase Enhances Etoposide and Mitoxantrone-Mediated DNA Damage: A Target for Myeloprotection in Cancer Chemotherapy

“…Recently a number of direct specific MPO inhibitors have been developed. These include PF-1355 (2-(6-(2,5-dimethoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide) (Zheng et al, 2015) and MPOi-II (4-(5-fluoro-1H-indol-3-yl)butanamide) (Soubhye et al, 2013). As expected, both of these inhibitors dramatically reduced MPO activity in NB4 cells (Supplemental Fig.…”

“…MPO has become a target of interest for novel anti-inflammatory drug development (Malle et al, 2007), and a number of potent specific MPO inhibitors were recently reported (Tidén et al, 2011; Forbes et al, 2013; Soubhye et al, 2013, 2016; Li et al, 2015; Zheng et al, 2015). We have used two such inhibitors, PF1355 and MPOi-II, and show that like SA, they reduce etoposide- and mitoxantrone-induced damage in MPO-expressing cells.…”

The role of neutrophils and NETosis in autoimmune and renal diseases

“…MPO inhibitors, such as 4-aminobenzoic acid hydrazide 141 or PF-1355 (REF. 144), reduce NETosis, neutrophil recruitment and levels of circulating cytokines. PF-1355 treatment reduced neutrophil accumulation in a mouse model of immune complex-mediated vasculitis and suppressed albuminuria and chronic renal dysfunction in a murine model of anti-GBM-induced glomerulonephritis.…”

Methods for measuring myeloperoxidase activity toward assessing inhibitor efficacy in living systems

“…Therefore, MPO is considered a druggable target with small-molecule inhibitors already identified and more expected for limiting ROS/RNS production. In preclinical study, several MPO inhibitors have limited inflammation in diseases, including thioxanthine-2 in chronic obstructive pulmonary disease studies [15], PF-1355 in vasculitis and glomerulonephritis [24], and INV315 in atherosclerosis [25]. In this review, we will mainly discuss the recent, emerging tools for in vivo assessment of MPO as a target with the goal of monitoring disease progression, tracking PMN migration, and detecting inflammatory sites for preclinical or clinical applications.…”