Rescue of Functional CFTR Channels in Cystic Fibrosis: A Dramatic Multivalent Effect Using Iminosugar Cluster‐Based Correctors

Cystic fibrosis is caused by a mutation in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. N ‐butyl 1‐deoxynojirimycin ( N ‐Bu DNJ), a clinical candidate for the treatment of cystic fibrosis, is able to act as a CFTR corrector by overcoming the processing defect of the mutant protein. To explore the potential of multivalency on CFTR correction activity, a library of twelve DNJ click clusters with valencies ranging from 3 to 14 were synthesized. Significantly, the trivalent analogues were found to be up to 225‐fold more potent than N ‐Bu DNJ and up to 1000‐fold more potent than the corresponding monovalent models. These results provide the first description of a multivalent effect for correcting protein folding defects in cells and should have application for the treatment of a number of protein folding disorders. Preliminary mechanistic studies indicated that CFTR correction activity enhancement was not due to a multivalent effect in ER‐glucosidase inhibition or to a different mode of action of the multivalent iminosugars.