Antisense oligonucleotide targeting the E3 ligase RFFL potentiates CFTR modulator efficacy in CF primary bronchial...

Cystic fibrosis (CF) is most commonly caused by the ΔF508 mutation in the CFTR gene, leading to misfolding and degradation of the CFTR protein. Although CFTR modulators such as elexacaftor/tezacaftor/ivacaftor (ETI) provide clinical benefit, their efficacy is limited, particularly in patients with rare or poorly responsive CFTR mutations. RFFL, an E3 ubiquitin ligase, plays a central role in peripheral quality control of CFTR, reducing its plasma membrane (PM) expression and attenuating the effects of modulators. Here, we developed antisense oligonucleotides (ASOs) containing artificial nucleic acids to selectively suppress RFFL expression. An optimized RFFL-targeting ASO enhanced the efficacy of CFTR modulators by increasing the functional PM expression of ΔF508-CFTR in primary human bronchial epithelial (CF-HBE) cells derived from CF patients. Notably, the ASO also potentiated the effects of ETI on CFTR mutants associated with rare forms of CF, including those with limited responsiveness to modulators. In some cases, the ASO alone restored CFTR levels to those achieved by ETI treatment. These findings establish RFFL-targeting ASOs as first-in-class CFTR stabilizers and highlight their potential as a nucleic acid-based therapeutic strategy for CF caused by both common and rare CFTR mutations.