Table 1

Classes of CFTR mutations, their effects and potential treatments

Class number	Consequence	Exemplar genotype	Potential therapies
Class I	No CFTR synthesis (premature stop codon)	G542X	PTC₁₂₄
Class II	CFTR processed incorrectly and does not reach apical cell membrane	DF₅₀₈	VX-809
Class III	CFTR reaches apical membrane, but channel regulation is abnormal	G551D	VX-770
Class IV	CFTR reaches apical membrane, but channel open time is reduced	R334W
Class V	Reduced CFTR synthesis	R117H
Class VI	CFTR reaches apical cell membrane, but has a shortened half life due to more rapid turnover	1811+1.6kbA>G