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

Abstract

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.

Searching for Glycomimetics That Target Protein Misfolding in Rare Diseases: Successes, Failures, and Unexpected Progress Made in Organic Synthesis

“…108 To date, the best results by far have been obtained with multivalent CFTR correctors that were found to be up to three orders of magnitude more efficient than the corresponding monovalent analogues, including the clinical candidate N-Bu DNJ (1). 110 This study provides a new potential answer to cystic fibrosis, but also raises many fundamental questions, especially concerning the molecular basis of the strong multivalent effect that is observed. This is just a beginning.…”

Design, synthesis and photochemical properties of the first examples of iminosugar clusters based on fluorescent cores

“…From 2010, the field has however experienced a major take-off with the discovery of the first strong multivalent effects in glycosidase inhibition observed with DNJ clusters based on β-cyclodextrin or C 60 cores showing strong affinity enhancements over the corresponding monomers (up to 610-fold per DNJ unit) [11–12]. In the following years, an impressive ever-growing number of multivalent iminosugars based on various scaffolds, ligands and linkers have been synthesized to further investigate the impact of multivalency on glycosidase inhibition [9–26]. The interest of the inhibitory multivalent effect for drug discovery was demonstrated by targeting glycosidases involved in rare genetic diseases linked to misfolded proteins [24–26].…”

“…In the following years, an impressive ever-growing number of multivalent iminosugars based on various scaffolds, ligands and linkers have been synthesized to further investigate the impact of multivalency on glycosidase inhibition [9–26]. The interest of the inhibitory multivalent effect for drug discovery was demonstrated by targeting glycosidases involved in rare genetic diseases linked to misfolded proteins [24–26]. The first examples of multivalent iminosugars such as 2 and 3 acting as pharmacological chaperones were thus disclosed in the field of Gaucher disease, the most common lysosomal storage disorder (Fig.…”

“…DNJ clusters 2 and 3 are indeed able to increase mutant β-glucocerebrosidase (GCase) residual activity levels as much as 3.3-fold in cells of Gaucher patients at micromolar concentrations. In another rare genetic disease, the rescue by multimeric correctors of the mutant CFTR protein implied in cystic fibrosis led to the first report of a multivalent effect for amending protein folding defects in cells [26]. As judged by EC 50 (half-maximal effective concentration) values, trivalent DNJ clusters 2 were indeed up to 225-fold more efficient as CFTR correctors than the clinical candidate N -Bu DNJ ( 1 ), a potent inhibitor of trimming ER glucosidases [26].…”

“…In another rare genetic disease, the rescue by multimeric correctors of the mutant CFTR protein implied in cystic fibrosis led to the first report of a multivalent effect for amending protein folding defects in cells [26]. As judged by EC 50 (half-maximal effective concentration) values, trivalent DNJ clusters 2 were indeed up to 225-fold more efficient as CFTR correctors than the clinical candidate N -Bu DNJ ( 1 ), a potent inhibitor of trimming ER glucosidases [26]. Taken together, these recent studies provide new therapeutic answers for a number of protein folding disorders [27–28] but also raise many fundamental questions concerning the mechanisms at play.…”