Iminosugars as a new class of cholinesterase inhibitors.

To further extend the scope of iminosugar biological activity, a systematic structure-activity relationship investigation has been performed by synthesizing and evaluating as cholinesterase inhibitors a library of twenty-three iminoalditols with different substitutions and stereochemistry patterns. These compounds have been evaluated in vitro for the inhibition of cholinesterases (different sources of acetylcholinesterase and butyrylcholinesterase). Some compounds have IC50 values in the micromolar range and display significant inhibition selectivity for butyrylcholinesterase over acetylcholinesterase. These are the first examples of iminosugar-based inhibitors of cholinesterases.

A systematic investigation of iminosugar click clusters as pharmacological chaperones for the treatment of Gaucher disease.

A series of 18 mono- to 14-valent iminosugars with different ligands, scaffolds, and alkyl spacer lengths have been synthesized and evaluated as inhibitors and pharmacological chaperones of ß-glucocerebrosidase (GCase). Small but significant multivalent effects in GCase inhibition have been observed for two iminosugar clusters. Our study provides strong confirmation that compounds that display the best affinity for GCase are not necessarily the best chaperones. The best chaperoning effect observed for a deprotected iminosugar cluster has been obtained with a tetravalent 1-deoxynojirimycin (DNJ) analogue (3.3-fold increase at 10 µM). In addition, our study provides the first evidence of the high potential of prodrugs for the development of potent pharmacological chaperones. Acetylation of a trivalent DNJ derivative, to give the corresponding acetate prodrug, leads to a pharmacological chaperone that produces higher enzyme activity increases (3.0-fold instead of 2.4-fold) at a cellular concentration (1 µM) reduced by one order of magnitude.

The multivalent effect in glycosidase inhibition: probing the influence of valency, peripheral ligand structure, and topology with cyclodextrin-based iminosugar click clusters.

In view of recent reports of a strong multivalent effect in glycosidase inhibition, a library of ß-CD-based multivalent iminosugars has been efficiently synthesized by way of Cu(I) -catalyzed azide-alkyne cycloaddition (CuAAC). In combination with the first application of isothermal titration calorimetry (ITC) experiments to the study of multivalent iminosugar-enzyme interactions, the inhibition properties of these click clusters were evaluated on a panel of glycosidases. The structural parameters that were varied include valency, peripheral ligand structure, and topology. The inhibition results obtained with the iminosugar clusters further highlight the importance of multivalency in the inhibition of α-mannosidase. Generally, the evaluated multivalent iminosugars displayed comparable thermodynamic signatures of binding towards α-mannosidase (Jack bean): that is, large negative enthalpies of complexation coupled with small entropies of either sign. In addition, the enthalpy-entropy compensation observed in all tested cases may be attributed to a common mechanism of dissociation for the enzyme-multivalent iminosugar interactions. The measured binding stoichiometries indicated that each iminosugar cluster interacts with no more than one protein molecule.

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.

The multivalent effect in glycosidase inhibition: probing the influence of architectural parameters with cyclodextrin-based iminosugar click clusters.

In contrast to most lectins, glycosidases may appear to be unpromising targets for multivalent binding because they display only a single active site. To explore the potential of multivalency on glycosidase inhibition, unprecedented cyclodextrin-based iminosugar conjugates have been designed and prepared. The synthesis was performed by way of Cu(I) -catalyzed azide-alkyne cycloaddition reaction under microwave activation between propargylated multivalent ß-cyclodextrins and an azide-armed N-alkyl 1-deoxynojirimycin derivative. Evaluation with a panel of glycosidases of this new class of glycomimetic clusters revealed the strongest affinity enhancement observed to date for a multivalent glycosidase inhibitor, with binding enhancement up to four orders of magnitude over the corresponding monovalent ligand for α-mannosidase. These results demonstrate that the multivalency concept extends beyond carbohydrate-lectin recognition processes to glycomimetic-enzyme inhibition.

Iminosugar-based glycopolypeptides: glycosidase inhibition with bioinspired glycoprotein analogue micellar self-assemblies.

Biomimetic nanoparticles prepared by self-assembly of iminosugar-based glycopolypeptides evidenced remarkable multivalency properties when inhibiting α-mannosidase activity. This approach paves the way to obtain biologically active drug delivery systems having glycosidase inhibition potency.

Glucocerebrosidase enhancers for selected Gaucher disease genotypes by modification of α-1-C-substituted imino-D-xylitols (DIXs) by click chemistry.

A series of hybrid analogues was designed by combination of the iminoxylitol scaffold of parent 1C9-DIX with triazolylalkyl side chains. The resulting compounds were considered potential pharmacological chaperones in Gaucher disease. The DIX analogues reported here were synthesized by CuAAC click chemistry from scaffold 1 (α-1-C-propargyl-1,5-dideoxy-1,5-imino-D-xylitol) and screened as imiglucerase inhibitors. A set of selected compounds were tested as ß-glucocerebrosidase (GBA1) enhancers in fibroblasts from Gaucher patients bearing different genotypes. A number of these DIX compounds were revealed as potent GBA1 enhancers in genotypes containing the G202R mutation, particularly compound DIX-28 (α-1-C-[(1-(3-trimethylsilyl)propyl)-1H-1,2,3-triazol-4-yl)methyl]-1,5-dideoxy-1,5-imino-D-xylitol), bearing the 3-trimethylsilylpropyl group as a new surrogate of a long alkyl chain, with approximately threefold activity enhancement at 10 nM. Despite their structural similarities with isofagomine and with our previously reported aminocyclitols, the present DIX compounds behaved as non-competitive inhibitors, with the exception of the mixed-type inhibitor DIX-28.