Pirfenidone

The exact mechanism of action of pirfenidone is not fully understood. It is suggested that the antioxidant effects of pirfenidone contribute to its anti-inflammatory effects, leading to antifibrotic effects.

Pirfenidone attenuates the production of transforming growth factor-β1 (TGF-β1), a key profibrotic and pro-inflammatory cytokine implicated in idiopathic pulmonary fibrosis (IPF). By suppressing TGF-β1, pirfenidone inhibits TGF-β1-induced differentiation of human lung fibroblasts into myofibroblasts, thereby preventing excess collagen synthesis and extracellular matrix production.

Some evidence suggests that pirfenidone downregulates pro-inflammatory cytokines, including TNF-α, interleukin-1 (IL-1), IL-6, interferon-gamma (IFN-γ), and platelet-derived growth factor (PDGF). Animal models demonstrated that pirfenidone promotes the production of anti-inflammatory IL-10 and prevents the accumulation of various inflammatory cells, including lymphocytes, macrophages and neutrophils. In animal models, pirfenidone inhibited the influx of inflammatory cells and ameliorated bleomycin-induced pulmonary vascular permeability. Several in vitro studies show that pirfenidone mediates antioxidant actions by scavenging reactive oxygen species (ROS) and inhibiting lipid peroxidation, thereby reducing cellular injury in IPF.