Evaluation of eluforsen, a novel RNA oligonucleotide for restoration of CFTR function in in vitro and murine models of p.Phe508del cystic fibrosis

PLoS One. 2019 Jun 28;14(6):e0219182. doi: 10.1371/journal.pone.0219182. eCollection 2019.


Cystic fibrosis (CF) is caused by mutations in the gene encoding the epithelial chloride channel CF transmembrane conductance regulator (CFTR) protein. The most common mutation is a deletion of three nucleotides leading to the loss of phenylalanine at position 508 (p.Phe508del) in the protein. This study evaluates eluforsen, a novel, single-stranded, 33-nucleotide antisense oligonucleotide designed to restore CFTR function, in in vitro and in vivo models of p.Phe508del CF. The aims of the study were to demonstrate cellular uptake of eluforsen, and its efficacy in functional restoration of p.Phe508del-CFTR both in vitro and in vivo. In vitro, the effect of eluforsen was investigated in human CF pancreatic adenocarcinoma cells and human bronchial epithelial cells. Two mouse models were used to evaluate eluforsen in vivo. In vitro, eluforsen improved chloride efflux in CF pancreatic adenocarcinoma cell cultures and increased short-circuit current in primary human bronchial epithelial cells, both indicating restoration of CFTR function. In vivo, eluforsen was taken up by airway epithelium following oro-tracheal administration in mice, resulting in systemic exposure of eluforsen. In female F508del-CFTR mice, eluforsen significantly increased CFTR-mediated saliva secretion (used as a measure of CFTR function, equivalent to the sweat test in humans). Similarly, intranasal administration of eluforsen significantly improved nasal potential difference (NPD), and therefore CFTR conductance, in two CF mouse models. These findings indicate that eluforsen improved CFTR function in cell and animal models of p.Phe508del-CFTR-mediated CF and supported further development of eluforsen in human clinical trials, where eluforsen has also been shown to improve CFTR activity as measured by NPD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Cystic Fibrosis / drug therapy*
  • Cystic Fibrosis / genetics
  • Cystic Fibrosis Transmembrane Conductance Regulator / genetics*
  • Disease Models, Animal
  • Epithelial Cells / drug effects*
  • Humans
  • Mice
  • Oligonucleotides, Antisense / pharmacology
  • Oligonucleotides, Antisense / therapeutic use*


  • Oligonucleotides, Antisense
  • Cystic Fibrosis Transmembrane Conductance Regulator

Grant support

This work was supported by the Cystic Fibrosis Foundation (grant number: RITSEM12G0) and the Netherlands Enterprise Agency (RVO) for InnovatieKrediet (grant number: IK12062), both awarded to TR. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement n° 633545, awarded to ProQR Therapeutics). WB, JS, HA, GH, HKB, MP, CP, PB, GP, NH, and TR are or were employees of ProQR Therapeutics. TL and SN received funding from ProQR Therapeutics. HdJ received consultancy fees from ProQR Therapeutics. The specific roles of these authors are articulated in the ‘author contributions’ section. The funder provided support in the form of salaries for authors indicated above (WB, JS, HA, GH, HKB, MP, CP, PB, GP, NH, and TR) as ProQR Therapeutics employees, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. ProQR Therapeutics is developing eluforsen/QR-010 as a treatment for cystic fibrosis. No other sponsors participated in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.