Table 1.

CFTR protein defects and their potential therapies

Class	Consequence of mutation	Mutation-specific therapy
I	No CFTR synthesis	Ataluren (PTC124)
II	Failure of CFTR to traffic to the cell surface	VX-809 and ivacaftor (combination)
		VX-661 and ivacaftor (combination)
III	Failure of CFTR to open at cell surface	Ivacaftor
IV	Decreased time CFTR channel is open at cell surface
V	Decreased amount of CFTR at cell surface
VI	Unstable CFTR with decreased half-life at the cell surface

Abbreviation: CFTR, CF transmembrane conductance regulator.