S42909 is an inhibitor of β-nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. S42909 has demonstrated vascular anti-inflammatory properties by preventing leukocyte endothelial cell adhesion, and vascular protection by reducing the expression of the endothelial cell dysfunction marker plasminogen activator inhibitor-1 (PAI-1) and decreasing matrix metalloproteinase-2 (MMP-2) activity. It is initially proposed for development for the oral treatment of venous leg ulcers.