NTRK1 and pulmonary fibrosis: For example, nintedanib is a receptor tyrosine kinase inhibitor used in the United States for idiopathic pulmonary fibrosis, which mainly interferes with fibroblast growth factor receptor, platelet-derived growth factor receptor, and vascular endothelial growth factor receptor; these targets were identified in the bleomycin-induced lung fibrosis in mice (95).