Cystic fibrosis transmembrane conductance regulator stabilizing agents

The present invention relates to binding agents specific for the cystic fibrosis transmembrane conductance regulator (CFTR), which increase its thermal stability to provide for potent therapeutics. More particular, the immunoglobulin single variable domains (ISVDs) identified herein reveal novel binding sites on the nucleotide-binding domain 1 of CFTR, which allow to rescue pathogenic mutant F508del CFTR from proteasomal degradation. The binding agents are therefore considered suitable in treatment of cystic fibrosis. Finally, also crystalline structures demonstrating binding interfaces, and computer-assisted methods for selecting molecules able to stabilize CFTR are described.