C3 and pulmonary fibrosis: Nintedanib has been shown to reduce pro-collagen 1 mRNA and total collagen in lung tissue in bleomycin models of epithelial cell injury-induced lung inflammation and fibrosis [4, 5], to reduce transforming growth factor-β1-induced elevations in N-terminal propeptide of type I collagen (pro-C1), pro-C3, pro-C6 and fibronectin in primary lung fibroblasts from healthy donors [26] and to reduce pro-C3 and C3M in precision-cut lung slices from subjects with pulmonary fibrosis [27].