TGFB1 and pulmonary fibrosis: Additionally, Pirfenidone, an FDA-approved drug for inhibiting TGF-β1 activity, originally used for the treatment of pulmonary fibrosis, showed a reduction in mRNA expression of TGF-β1 signaling molecules, fibrotic genes, decreased staining of type 1 collagen, and a decrease in the number of pSmad3+ cells when topically applied to mouse models.