CFTR and cystic fibrosis: Recently, Pedemonte et al. reported the discoveryof ARN23765 (Figure 1), a preclinicalstage compound with remarkable subnanomolar potency in rescuing CFTRfunction in bronchial epithelial cells from F508del-CFTR CF individuals.22 Preliminary data supported the hypothesis that ARN23765 activity is compatible with that of type I correctors.Indeed, it shows additive effects in mutant CFTR rescue with typeII and III correctors, but not with other type I correctors.22 Nevertheless, an extensive biological characterizationof ARN23765 has not yet been reported.