2-B-P-096 〇日向 大智¹、福田 友佳理¹、福田 亮介¹、笠原 勇矢²、小比賀 聡^2,3、吉田 徳幸⁴、井上 貴雄⁴、沖米田 司¹ Hinata Daichi¹, Yukari Hukuda¹, Ryosuke Hukuda¹, Yuuya Kasahara², Satoshi Obika^2,3, Tokuyuki Yoshida⁴, Takao Inoue⁴, Tsukasa Okiyoneda^{1 1}関西学院大学・生命環境学部・生命医化学専攻、²医薬基盤・健康・栄養研・創薬デザイン研究センター、³大阪大・院薬、⁴国立医薬品食品衛研・遺伝子医薬部 ¹Dept Biomed Sci, Kwansei Gakuin Univ, ²NIBIOHN, ³Grad Sch Pharmaceut Sci, Osaka Univ, ⁴NIHS Cystic fibrosis (CF) is caused by mutation of CFTR, a cAMP-regulated Cl- channel expressing at the apical PM of epithelia. The most common mutant ΔF508 CFTR induces misfolding, leading to ubiquitin-mediated degradation. The CF drug Trikafta improves the PM expression of ΔF508 CFTR. However, the functional ΔF508 CFTR is still removed from the PM in the presence of Trikafta. Previously, we demonstrated that a ubiquitin ligase RFFL directly interacts with ΔF508 CFTR at the PM and endosomes, thereby facilitating the ubiquitination, endocytosis, and degradation of the CFTR mutant. Notably, RFFL knockdown inhibited the CFTR degradation and enhanced the efficacy of Trikafta in cell lines. 
In this study, we determine whether RFFL KD inhibits the degradation of endogenous ∆F508 CFTR and enhances the efficacy of Trikafta in primary bronchial epithelial cells derived from CF patients (CF-HBE), which is the final evaluation system for CF therapeutics in preclinical stages. To achieve the RFFL KD, antisense oligonucleotides (ASO) containing artificial nucleic acids with high intracellular uptake capacity and excellent nuclease resistance were designed. Our results demonstrated that the introduction of the RFFL-ASO resulted in a 1.4-fold improvement in endogenous ∆F508 CFTR function. In conclusion, our study strongly implies that suppressing RFFL enhances the efficacy of CF therapeutic agents in the CF-HBE, underscoring the genuine potential of RFFL as a viable drug target for CF.