In addition, if P. aeruginosa inhibits VX-809 + VX-770 stimulated F508del-CFTR Cl secretion one would expect to see a disproportional improvement in FEV1 in subjects not infected with P. aeruginosa compared to those who are infected with P. aeruginosa. However, at the North American CF Conference in 2014 data were presented demonstrating that there was no significant difference between the effect of VX-809 + VX-770 on FEV1 in subjects positive or negative for P. aeruginosa [11]. This evidence concerns the gene CFTR and cystic fibrosis.