In addition, some small molecule compounds (nintedanib, pirfenidone, regorafenib, anlotinib, and imatinib) have been shown to alleviate bleomycin-induced pulmonary fibrosis by downregulating the TGF-β1/Smad3 signalling pathway [26, 34, 42–44]. This evidence concerns the gene SMAD3 and pulmonary fibrosis.