CFTR and cystic fibrosis: Since several in vivo and in vitro studies have suggested that enhancing the F508del-CFTR functional activity as little as 5% may significantly diminish CF symptoms [51,52,53], a major effort of CF research has been intended to identify and characterize small molecules, namely correctors, that are able to deliver defective processing CFTR mutants (class 2 mutations), such as the F508del-CFTR, at the plasma membrane.