CFTR and cystic fibrosis: VX-770 is currently approved for CF subjects with one copy of one of 38 mutations located throughout the CFTR sequence, including MSD1 (e.g. D110H, E193K), MSD2 (A1067T, R1070W), NBD1 (G551D, D579G), NBD2 (G1244E, G1349D), and other regions (E56K, P67L in the lasso domain)2,22,23.