On the discovery and development of CFTR chloride channel activators

Chloride channels play important roles in vital cellular signalling processes contributing to homeostasis in both excitable and non-excitable cells. Since 1987, more than ten ion channel genes have been identified as causing human hereditary diseases among them the genes for the voltage-dependent chloride channel ClC-1 (myotonia) and the cystic fibrosis transmembrane conductance regulator (CFTR) protein (cystic fibrosis). The CFTR gene was cloned in 1989 and its protein product identified as an ATP-gated and phosphorylation-regulated chloride channel during the following two years. Since then, searching for potent and specific small molecules able to modulate normal and mutated CFTR has become a crucial endpoint in the field for both our understanding of the physiological role that CFTR plays in epithelial cells and more importantly for the development of therapeutic agents to cure cystic fibrosis (CF). It is predicted that a pharmacological approach would help not only to restore the defective transport activity of mutant CFTR but also to correct the regulatory function of CFTR. This review describes the evolution of CFTR pharmacology and how during the last five years, high throughput screening assays have been developed to identify novel molecules, some of them probably constituting a reservoir of future therapeutic agents for CF.