Delivery of RNAi Therapeutics to the Airways—From Bench to Bedside

Qiu, Yingshan; Lam, Jenny K. W.; Leung, Susan W. S.; Liang, Wanling

RNAi has been exploited to suppress the production of key molecules involved in the fibrotic process, such as TGF-β [92, 224] , amphiregulin (AR) and connective transforming growth factor (CTGF) [8, 225] (Table 5) . Clinical trials examining the effect of neutralized antibodies to block the activity of TGF-β are currently ongoing [14] . Since lung epithelial cells are the key cell types in the pathogenesis of pulmonary fibrosis, local administration of RNAi targeting TGF-β to the lungs can ensure high local concentration of RNAi molecules to produce therapeutic effects. Intratracheal delivery of siRNA targeting TGF-β1 could effectively inhibit pulmonary fibrosis, improved lung function, and prolonged survival in human TGF-β1 transgenic mice [224] . In another in vivo study, intranasal delivery of miRNA-326 mimic, which was designed to suppresses the expression of TGF-β and other profibrotic genes, significantly reduced TGF-β1 expression level and further alleviated the fibrotic feature in the bleomycin-induced pulmonary fibrosis [92] . The results suggest the potential of targeting TGF-β or its signaling pathway using RNAi technology for the management of lung fibrosis. Notes: AR, amphiregulin; CCL2, chemokine (C-C motif) ligand 2/monocyte chemoattractant protein-1; CTGF, connective tissue growth factor; PDGF, platelet-derived growth factor; PDMAEMA, poly(dimethylamino)ethylmethacrylate; PMAPEG: poly(methylether-methacrylate-ethyleneglycol); SAMiRNA, self-assembled micelle interfering RNA; TGF-β, transforming growth factor β.