Mucoviscidose : nouvelles thérapeutiques ciblant la protéine CFTR

[New therapies for cystic fibrosis targeting the CFTR gene or the CFTR protein]

BACKGROUND

The treatment of cystic fibrosis has been symptom-based for a number of years. New therapies that aim to improve CFTR protein function are now emerging.

CURRENT SCIENTIFIC KNOWLEDGE

The results of gene therapy has been modest but a recent clinical trial shows a positive effect on FEV1. Recent research has focused primarily on CFTR protein function. Significant respiratory improvement (an average 10% FEV1 increase and a decrease in the frequency of exacerbations) has been achieved with ivacaftor, a CFTR potentiator, in patients with gating mutations, resulting in its marketing authorization (in 2012 for the G551D mutation and in 2015 for rarer mutations). In phe508del homozygous patients, the combination of ivacaftor with a CFTR corrector (lumacaftor) has also led to respiratory improvement, albeit less impressive. The effectiveness of ataluren in patients with nonsense mutations is being evaluated.

OUTLOOK

New CFTR correctors and potentiators are being developed. CFTR protein therapy could change the course of the disease but cost/effectiveness issues should not be overlooked.

CONCLUSION

Ivacaftor can be prescribed in CF patients with a class 3 mutation from the age of 6 years. The Orkambi^® will soon be available for homozygous phe508del patients from the age of 12 years.

A new 9-alkyladenine-cyclic methylglyoxal diadduct activates wt- and F508del-cystic fibrosis transmembrane conductance regulator (CFTR) in vitro and in vivo

Cystic fibrosis transmembrane conductance regulator (CFTR) is the main chloride channel present in the apical membrane of epithelial cells and the F508 deletion (F508del-CFTR) in the CF gene is the most common cystic fibrosis-causing mutation. In the search for a pharmacotherapy of cystic fibrosis caused by the F508del-CFTR, a bi-therapy could be developed associating a corrector of F508del-CFTR trafficking and an activator of the channel activity of CFTR. Here, we report on the synthesis of 9-alkyladenine derivatives analogues of our previously discovered activator of wt-CFTR and F508del-CFTR, GPact-11a, and the identification of a new activator of these channels, GPact-26a, through various flux assays on human airway epithelial CF and non-CF cell lines and in vivo measurement of rat salivary secretion. This study reveals that the possible modifications of the side chain introduced at the N9 position of the main pharmacophore are highly limited since only an allyl group can replace the propyl side chain present in GPact-11a to lead to a strong activation of wt-CFTR in CHO cells. Docking simulations of the synthesised compounds and of four described modulators performed using a 3D model of the wt-type CFTR protein suggest five possible binding sites located at the interface of the nucleotide binding domains NBD1/NBD2. However, the docking study did not allow the differentiation between active and non-active compounds.