Notably, although a lack of responsiveness in the FRT system does not predict lack of clinical benefit (eg, a CFTR variant that does not meet the threshold for in-vitro responsiveness might still be clinically responsive), these data suggest that vanzacaftor–tezacaftor–deutivacaftor has the potential to treat a broader population of people with cystic fibrosis com pared with elexacaftor–tezacaftor–ivacaftor through an expanded indication. Here, CFTR is linked to cystic fibrosis.