Pirfenidone has well-established antifibrotic and anti-inflammatory properties in various in vitro systems and animal models of fibrosis.[10] A number of cell-based studies have shown that pirfenidone reduces fibroblast proliferation,[11][12][13][14] inhibits transforming growth factor beta stimulated collagen production[11][12][15][16][17] and reduces the production of fibrogenic mediators such as transforming growth factor beta.[13][16] Pirfenidone has also been shown to reduce production of inflammatory mediators such as tumor necrosis factor alpha and IL-1β in both cultured cells and isolated human peripheral blood mononuclear cells.[18][19] These activities are consistent with the broader antifibrotic and anti-inflammatory activities observed in animal models of fibrosis.