CFTR and cystic fibrosis: The observation that P. aeruginosa reduces VX-809 + VX-770 stimulated F508del-CFTR Cl secretion, coupled with the fact that ~85% of adult CF patients are colonized with P. aeruginosa suggests that the modest effect of VX-809 + VX-770 on FEV1 in CF patients (3–5% increase) may be due in part to chronic infection with P. aeruginosa.