Structure-guided combination of novel CFTR correctors to improve the function of F508del-CFTR in airway epithelial cells

Although remarkable rescue has been achieved for treatment of Cystic Fibrosis (CF) by the combination of two correctors (VX-661, VX-445) and one potentiator (VX-770), the stability and trafficking defects induced by the most common mutation, F508del, are not completely reversed. Therefore, more effective CFTR correctors are still needed. We employed in silico and molecular modelling approaches to design and probe the binding site of novel series of CFTR correctors (a-c). Structure-based studies allowed us to design and synthesize novel class I (b series) and class II (a series) modulators. Thus, class I modulator activity relies on interactions with Met152, Phe81, Phe191, Trp361. The design of class II corrector could be managed via NBD2-ligand H-bonds, involving Gln1291 or Val1288. Furthermore, c compounds were proposed featuring putative dual corrector ability (2c) and class II corrector behavior (1c). Functional measurements in F508del-CFTR CFBE cells and primary nasal epithelial cells demonstrated that eight of fourteen compounds acted as CFTR correctors and the F508del-CFTR rescue was comparable to the level measured after VX-809 or VX-445 treatment in CFBE cells. Through rational selection based on molecular docking studies and mechanisms of action, we showed that combination of compounds (7a+1b and 2a+2b) targeting distinct domains of CFTR, can additively/synergistically rescue F508del-CFTR function in both CFBE cell line and primary nasal cells. Our study demonstrated that in silico and in vitro approaches to develop and investigate the mechanism of action of novel CFTR correctors could be a tool to optimize the combination correctors therapy to synergistically rescue mutated CFTR.